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Soils and Foundations 2007年
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soils and Foundations
| タイトル | 表紙（Soils and Foundations） | ||||
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| 出版 | soils and Foundations | ||||
| ページ | -〜- | 発行 | 2007/02/15 | 文書ID | 20973 |
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| 出版 | soils and Foundations | ||||
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| タイトル | Creep Behavior of Tuffaceous Rock at High Temperature Observed in Unconfined Compression Test | ||||
| 著者 | Kenko Shibata・Kazuo Tani・Tetsuji Okada | ||||
| 出版 | soils and Foundations | ||||
| ページ | 1〜10 | 発行 | 2007/02/15 | 文書ID | 20975 |
| 内容 | 表示 SOILS AND FOUNDATIONSVOl 47,No .l,io, Feb. 2007Japanese Geotechnical SoclelyCREEP BEHAVIOR OF TUFFACEOUS ROCK AT HIGH TEMPERATUREOBSERVED IN UNCONFINED COMPRESSION TESTKENKO SHIBA Ai), KAZUO TANlii) and TETSUJI OKADAiii)ABSTRACTGeologicai disposal in soft rocks is expected as one of the most practicable methods for isolation of high-levelradioactive ¥vastes. Since the country rock around the deep tunnels tends to be heated for a long term due to continuous collapse of nuclides, creep behavior of the soft rocks of imperrneable nature under hi_ h temper'ature should bestudied. Under different temperatur'es fr'om '_4'C to 95'C, a series of unconfined compression tests lvas conducted on atuffaceous rock, Ohya stone, at creep stress r'atios ranging frorrl 0.6 to I .O. The results sho v that the creep behavior isaccelerated by high ternperatures over 60'C. That is, for higher ternperatures, the time to failure is decreased, ¥vhile theminimum strain rate is increased. A creep model is then pr'esented, in ¥vhich attention is paid to the change in strainr'ate ¥vith time. Unique relationships bet¥veen the minimum strain rate and various creep parameters are used, thatappear to be dependent on neither' creep stress ratio nor' temperature. According to the proposed model, the creepfailure ¥vill not take place if the creep stress ratio is lolver than 0.44.Key words: constitutive model, creep, geological disposal, soft r'ock, strain rate, temperature, unconfined compres-sion test (IGC:F6/G2)Geological disposal is seen as one of the rnost practicable methods for isolation of high-level radioacti¥'e ¥vastes.studies are needed to elucidate the influence of temperatures on creep behavior of' soft rocks. Attention shouldbe paid to the rock type, and to high temperatures closeto 100'C for the geological disposal of high-level radioac-INTRODUCTIONSedimentar'y soft rocks, especially mudstones, ar'etive ¥vastes.expected as one of the prime candidate as country rockfor this facility (NUMO, 2003). Because they are leastEffects of temperature on creep behavior' under confinin_ : pressures ¥vere also investigated in triaxial tests byjointed thereby irnpermeable sufficiently to prevent suchhazardous ¥vastes from leakage.The countr'y rock around the disposal tunnels tends tobe heated for a long term due to continuous collapse ofnuclides for over tens of thousands years. The temperature of the surrounding rock mass close to the heat sourceHettema et al. (1991) and Thimus and De Bruyn (1998).Their results demonstrated marked influence of tempera-is expected to rise as high as 100'C (JNCDI, 2000).ratios were varied from 0.6 to 1.0. On the basis of theexperirnental data, Kato et al. (2004)'s creep model wasimpr'oved to take into account the influence of tempera-ture, but only limited test results ¥vere reported.In this study, under diffcrent temperatures from 24'Cto 95'C, a series of unconfined compression tests ¥vasconduct.ed on a tufi'aceous rock, Ohya stone. C.r'eep stressTherefore, Iong-term behavior, i.e. creep, of soft rocks inhigh temperatures should be studied.Four reports ¥vere found in the literatures on uniaxialcreep behavior of soft rocks under high temperatures.Yamabe et al. (2001) revealed that creep behavior of atuffaceous rock under temperatures from - 10'C to 55'Cture.METHOD OF CREEP TEST¥vas accelerated for higher temperatures. Similar findin_a._sTes't Appa/'atuS¥vere reported with a diatomaceous mudstone underFigure I sho¥vs the unconfined compression test ap-'_0-90'C (JO et al., 2005) and with a sandstone under1-80eC (Kodama et al., 2005). Howe¥'er, Kato et al.(2004) reported that creep beha¥'ior' of a mudstone wasparatus specifically designeci for creep tests under hightemperatures. The application of' sustained axial load isindependent of temperatures from 20eC and 60'C. Asrnade by leveraged dead ¥veights to f'orestall powerfailures. The maximum load, 50 kN, can allow applica-these reports contradict each other, more experimentaltion of axial stress, 25 MPa, on a specirnen of' diameter 50i)ii}iii)Chiyoda Corporation, Japan (keshibata@ykh.chiyoda,c0.jp).Yokoha na Nationai University, Japan (tani@cvg ynu ac.jp).Central Research Institute of Electric Po¥ver Induslry, ,Japan (t-okada@criepi_derrken.or.jp)-The manuscript for this paper ¥vas received fbr revielv on Jul}' 4, 2005; approved on July 26, 2006.Vri ten discussions on this paper should be submitted before September 1, 2007 ro the Japanese Geo echnical Society 4*38 -,Bunk_vo-ku, 'Tokyo 1 12-001 l, Japan. Upon request the closing date may be extended one month.1,Sengoku, SHIBATA ET AL_286LV DT*4Slraina! e,Tncrmocoupleoinsulated cellFig. 1. Test apparatus for creep test': of T1:1'1::47 m/s and the lon*'itudinal lva¥'e velocity Vp= 2474d:99 m/s were found within the ranges of previous studieson Ohya stone (Ku¥vabara, 1984; Nakajima et al., 2000;V :Kurumura et al., 2003). Consistent data ¥vith small variations ensured that these specimens ¥vere practically identi-,F:- 2100Xub¥cal to each other.b rs' Io' s4)eleajj'7Tas: sil 20QIO) : :1 40040F g. 3. Relationslvip betlveen q** and T35002800o 'o 60T ('O so molrv xurssls' l 2003) : :'Ei_ ht unconfined compression tests (JIS A 1216-1998)¥vere conducted under temperatures T= 24'C, 80'C_ and95'C (Miho, 2005). As sho¥vn in Fig. 3, the values of'I ::1"JI¥"' 'L' ;ti , "1'¥ "V700unconfined compression stren*'ths14i820;/t (kN/m3)Fig. '-. Relationship bet veen 11, Vp and yq= -O.0149T+ 6. 10 (1)The creep stress ratio, q****plq , is defined for the respec-mm.The specimen placed in the insulated cell is submergedin the ¥vater circulated by. a pump. The temperature of thelvater is controlled in a thermostatic bath equipped ¥vithheat source.Measurements are made for temperature by a thermocouple, axialment by a LVDT,lateral strainslateral surfacevere q =5.74 0.43MPa at ordinary temperature, '-4'C, and decrease linearly ¥vith increasing temperature. As r'eference strengths,the values of q (MPa) can be estimated as a function of T('C) obtained by linear regression.oload by a load cell, and axial displacerespectively. lvloreover, both axial andare measured by strain ( ages pasted onof a specimen at opposite diagonal posi-tions. Note that external measurement by the LVDT maysuffer from bedding errors (Matsumoto et al., 1999)^Whereas local measurement by strain gages is believed tobe more representative of specimen's beha¥'ior, and isused for further analysis.tive values of T, ¥vhere q****p is the axial stress durin_'creep.Loading alld Measure/7lentAfter the specimen placement in the insulated cell,the temperature of the cell ¥vater ¥vas raised gradually,0.5'C/min., to the intended value. The specimen vasthen left for at least thirty minutes before application ofaxial load. This is to allo¥v the temperature of the specimen to become the same as that of the cell ¥vater, which iscontrolled vith the maximum variation of :!:0.5'C.To avoid impact or dynamic effect on the specimen, theaxial load ¥vas raised slo¥vly, 0.230.45 MPa/s, to attainthe intended creep stress, q****p, in 10-17 seconds. Fromthe start of load application, measurement were madeSpecil 71 enRhyoiitic ¥velded tuff of Miocene deposit, denoted asOhya stone or green tuff, ¥vas used as the test material.Twenty-five cylindrical specimens of diameter d= 50 mmand height /1 = 100 mm were drilled from dry cubic blocksof about 300 mm. For saturation, they ¥vere kept in theevery 0.5 second for' 30 minutes, and then the interval wasset I minute after that.Data A ila!ysisThe creep time, t*, is defined as the elapsed time sincethe axial stress reached the intended creep stress.Although the axial load was kept constant during¥vater and deaerated for t¥vo ¥veeks.The siz,e, the ¥veight, and the ultra-sonic ¥vave velocitlescreep, the axial stress ¥vas slightly decreased as the cross-¥vere measured of all the specimens. As sho¥vn in Fig. 2,section of the specimen ¥vas increased gradually lvlththe total unit weight ),* = 1 8.5 1 (mean ¥*alue)O.?_6 (stand-creep defor'mation. So, the creep stress, q****p, is deter-ard deviation) kN/m3, the shear ¥va¥'e velocity V,= 1082mined as the average axial stress for O <, t*< t*F, ¥vhere t*f is CREEP BEHAVIOR OF TUFFAC'EOUS ROCKTabie l.T qq,,.,pL*qs"'" Iq.(oC)( 'lPa)Experimental condition and creep parameters!*1 t*2ea T In!t -/ min)(?'/a(min)o 663 .OOE-071 70222o 787.60E-054831203305 03o.88S . 97F -05547i3703_80o 693 60E-07> 70167> 70167o_79l .70E-0325916- o.750-o 7505,02O 911 .40E-043S872242-o 874- o.6903,23o . 623 . 90E-0715969916871 i26349- o.929o 732 50E-0616593l 962 1 4422- O.9)- l4 35o 84l 42E-0434874, , 54 98o.96ooo3.21o.653.80o 77( 'lPa)3,7824 4 . 47 5 . 7440 4.36 5.503 . 8060803L: ;(iHi l(min) (min)22843 1 1 7755- o.900- o_ 852H7 7(?･ )- o.900o 220- o 650o.262- o 800o 265o.916O 201*lo 258O 217- o.630o 250- o.680o . 2495.2- 4.914.34340E-062501 1 129S15034oo2 ,,o <- o.903-O 7192.0<oO. 150O.069O 096O. 1 97- o. 580o.7 9o 348- o 645- o 700o.338o 882 98E-O15 .ool 02l 03E-Ol2.85O.614.46E-06>31115>31115- o. sso*1o 722.43E-05> 2 1 322> 2 1 32',2- o.800*loo95 3.39 4.683 73o 80O.450 =O 1340.30-,2_0<o* I : N,Ieasurement by strain gages ¥vas failed_the time to creep failure. The values of t,f can be determined ¥vith least variations, as the creep failures takeplace abruptly; thereby defined by an arbitral value ofequated to he rninirnum strain rate, *,min' As sho vn inFig. 4(c), in the tertia 'y creep, the double logar'ithmicaxial strain, e*=20/0, in this study.t*, is again modeled by a linear expression. The slopes ofthe lines in Figs. 4(b) and 4(c) for the prirnary creep andthe tertiary cr'eep are defined as ml and ln3, respectively.Test Casesrelationship bet¥veen a and tirne lef't before failure, tcSeventeen tests ¥vere carried out as sho vn in Table 1.The transition time from the primary cr'eep to theTo study the influence of creep stress ratio, qc'eep lqu' andsecondary creep, tcl' is determined from the intersectiontemperature, T, on creep behavior, the range of qc"eplq.Furthermore, three tests were stopped before creepof the respective regression lines in Fig. 4(b). The transitlon tirne from the secondary creep to the ter'tiary creep,t*2, is also determined from the intersection of the respective regression lines in Fig. 4(c).As above, the strain rates, a' in each cr'eep stage can befailure, as the primary creep appeared to continue in-expressed by the following equations;was set from 0.6 to I .O and that of T vas set from 240C to950C*, respectively. Thr'ee specimens vere failed beforet.he intended creep stress ¥vas loaded, thereby 8.0>20/0.tolerably long time.Primary creep (O < t*CREEP MODEL AND CREEP PARAMETERSIn general, creep behavior of rocks is categorized intothree stages taking into account the change of strainrates, *, as sho¥vn in Fig. 4(a). In the primary creep, *decreases vith time asymptotically to a cer'tain value. Inthe secondary creep,* becomes constant; thus theminimum strain rate, *,*j*. In the tertiary creep, * incr'eases acceleratingly with time leading to creep failure.Kato et al. (2004) proposed a creep model based on thisthree stages concept. As shown in Fig. 4(b), the doublelogarithrnic relationship bet¥veen strain rate,*, and creeptime, t*, in the primary creep is modeled by a linearexpression. The strain rate in the secondary creep is thent*i)(c _10g 8* lnllog - Iog a*t**Secondary creep (t* <:tc tc2) a e (3)Tertiary creep (t*2 < tctcf( :)10gwheret,f)a = /n3 Iog + Iogtcrta,mit (4)a* is the reference axial strain rate at the referencetime, tcr'By integration of these strain rates for respective cr'eepstages,*, the follo ving equations can be obtained tocalculate the change of axial strains, 8*, with creep tumet*, as sho¥vn in Fig. 4(d); SHIBATA ET AL.;L(b)(a)( c)A '' .Sec(SecondaFy'' ''-Prin'ary* (log scale)t* (log scale)ea (log SCale)TertiaryPrirnary>lSecondary ,Tertiarv' Failure* Failure1lmlCa ,mln-tcf-tc2 tcf-t cltcl tc7-tcftc (log scale)tc- (normal scale)tcf-tc(log scale)(d))8a( normal scale:f'_a; 7c --Failureprimary secondar)i' la'_calTertiary< 1caOO tcl tc2 tcftc (normal scale)Fig. 4.Creep model and creep parameterPrimary. creep (0<t* t*1)8e:r ti' 1¥)+80. *a=(n7 ' 1)t "'=+1((:,)Secondary creep (t- <t.<t .) e =(5)(t -t l) ea*1 *= *- a a,mln * cTertiary creep ( t*2 < t**.*i* ( tcftc2 )e* =' (nl3 + 1)(6)tci)fll_( ) Tf +e .,(7)tcf tc "** 1tcftc21) Change of strain rate vith creep time Is typicallycharacterized by three creep stages, i.e. primary, secondary and tertiary creeps, as sho¥vn in Fig. 4.2) As sho¥vn in Figs. 5(b) and 5(c), the doublelogarithmic relationships bet¥veen* and t* in the primarycreep and between * and t*ft* in the tertiary creepappear to be expressed by linear expressions.3) Creep beha¥'ior is accelerated for higher temperatures, especially for over 60'C (Shibata et al., 2004).¥vhere 8ao is the initial axial strain at tc= O minute, and e iand ea2 are the axial strain at t* = t*i and tc = t*1' respecti¥rely.On the ¥vhole, the proposed model is described ¥vith atotal of eight creep parameters, i.e. n71, m3, tci ' tc2, 8ao,*r'*,mi and tcr, which can be easily determined by the abovementioned procedure from the test results. The transitiontimes, t*1 and tc2, can be replaced by the relative transitiontimes, t.] It,f and tc2ltcf'TF,ST RF,SUl,TSINFLUENCF, OF TEMPERATURE ONRELATIONSHIPS BF.TWF,EN CRF.EPPARAMF,TF,RS AND CRF,F,P STRESS RATIOFigures 6 to 11 summariz,e the relationships bet¥veensome creep parameters and the creep stress ratios, q****p/q , obtained under different temperatures, T.Figure 6 sho¥vs the relationship bet¥veen ll7}, ln3 andq*,**plq.. n71 represents the deceleration of st,rain rate inthe primary creep stage, and lll3 represents the acceleration of strain rate in the tertiary creep sta*'e. The values ofFigures 5(a) to 5(d) compare typical test results ob-ll71 seem to increase from -0.9 to -0.6 ¥vith the values oftained for' creep stress r'atio bet¥veen 0.84 and O.91 underdifferent temperatures. The follo¥¥'ing features are dra¥vn.q /q from O 6 to I O but independent of T Althou'h''**p " . ' , . *the values of ln3 range similar values, they are dependent 5CREEP BE賛AVIOR OFτUfFACEQUS ROCK0610・も先丁黙80℃丁軍80℃05＝，P勾冒＝088 目10・1惹P内、．．．＿．．．訪6・℃・・法『｝…＼…・…訟曇一謎．．ぶま翠二㌦詰匹プー『沁1σ’∼ 翻……04鑓”繍調響鰹窯03 σ二∫39F〆9冨＝088．．！10402 ヨO l10’50i50 300国0℃ 煮臥奪非llツ／ r＝40℃ ㍗24℃ 9‘譜」琿09レ…−9謂3盤躍088” 巽鍔，，F／9曽慧088 9；「0450 600150 300 4506〔｝0 ∫（min）’（m搬） （d）（a）Fl9．5（￡）．Relatl・鑓s是11pbetweenどaand！。f・r9。，。，P／9u−o・84−o・91Fl9，5（d）。Rel負1亘onsh」PbeIweenεaandずcforgC，、想P／9ロ竺o・84−o，9篁0010暦織噛糞』11「（℃）2440608095“1 ③ 醗 （》 」戯 Ψ鱗／9、こ0889 し一〇3’η， ○ 口 ◇ △ ム…i・06求』1二！．、．＼”Ql o ム ◇ ○隣 ◇ ムコ 会剣 Ψ 献φ8．認⑨G厨『φ貰一 一〇9圭び！、．一121σ5・15l o’： 10 10＝ 1σ101σ06∼c（min）u07 0、8 09 王0 9“障。p／9、（b）F「19．6・RelaIionship between1πi，〃133nd g。，書。p／guFig．5（b）．Rela匡ionshipbetweenεaandf。forg。，。。p／9u竺o・84−0・9玉loPT（℃）244060 80105 ㊥ 囲 ⇔ A一！￠1σ、還ir目l／r㍗80℃雰 』σ σ，や／9L軍08810−r／1。三1＿．．、．．．＿．．＝。㎏慨 『！ づ／！σ圏o℃・一ム．＿！一『瓦r！』101σΣ061010りi O二 ロユむ ゆ ぬ102 三σ07 08 09 1、09c「．緯p／9u ！Cf一1c（mln） （c）Fig．5（c）． Rel飢lo簸shipF董g。7。 Reiat蓬on曲ip be重ween1。f and gc，。。p／g、監between 6目and（fcげ’c）f・ぞ9cre。P／9u讐 O．84−0．91 Figure8showstherelationshlpbetween∼。玉／∼。f，！。2〃。r＆ndσ。，，，p／gu；曲ere∼。1／∼。fand1。2／∼。frepresen曲eratiosneithero昭。，。，p／9unorT。 Figure7shows the sem圭一10garithmic re正atiQnship be−of1c at the end of the prlmary creep and重he secondarycreep重o the f＆ilure time，∫。f，respect圭vely．The values oftween the tlme to creep failure，ご。f，a鳳d g。，，，p／σu．Theご。1／ご。f increase from O．1to O．3wlth the values ofσ。，巳。p／σu星ogarithmicv＆1uesof1。fdecreasemoreorlesslinearlyfrom O．6to1．0．Whereas，the values of1。2／！。f decreasewith（1。，，，p／（7u．The（1ata for24，40an（160。C again appeαrfrom O．8to O．6for the same range ofσ。，，，p／g、．Thissimilar，while those for over60。C shows significantlyimplies that，the relative perlods of the primary creep an（1smaller1cf values．the terti＆ry creep becolne longer for larger values of SHIBATA ET AL6JOC>t=.!t': o c::<>Aos*8T('C) 14 40 60 SOi*],i,. oc Ao a;o<>;; 06> A-iOll-1 -cc)AO'O'- 4A' i - -?.i__ _:c _O Il-i6leF cooa.6 e 7 O 8091 O1qcreeplquRe atronship betFig. 8140 T60( C_) 80-1820Fig. 11.een t,1 It,r t, /t,r and q,,,,p/qOoRelationship bctween parameter B slnd TParallel fitting lines are dr'a¥vn for individual temperatures as expressed by the follo¥1*ing equation;0504log=12 q*.**,j"**P + B (8)q**.; 03¥vhere their' slopes are set as 12 ¥vhich is the average valueof the slopes of linear regression lines for respective temperatures. As sholvn in Fig. 1 1, the intercept B is given as$ o. 2a linear function of T by regression analysis.alOo0607 OSi O i lq !q09**e*p *]iOiOe'f0li_ J!nes sr _ q_ :(8)&'{?)'_ _T ;socc. .¥ . .i O '-r=60 C - ' --' '-' -' il C'2._;_ ___[ . ..... . .::1 rso:C'______'Ezla)L// et: oT 95 C :Tl O-//:/( : :_'lcrs. eiC _';11 _ :i _' __ _''' _j_ ... 1.t ':::::: ::i_ _:_. :.::l O'sT( C) 24 40 60 80 95Q B c A v06 07 08 1 O 1 109q lq ,c*eep *Fig. lO.*. ,i*, and !*f, are dependenton both q*,**p /q and T. The influences of Tbecome moreevident for higher temperatures above 60'C. In the abo¥'ediscussion, it should be r'eminded that the unconfinedthe third type of parameter's,compression strength, q*, is defined as a function oftemperature, T, as Eq. (1).T 2s C1 0i 0'7temperature, T, are taken into account, the creepparameters are grouped into three types. The first type ofparameter, l773, is dependent on neither q****p/q nor T.The second type of parameters, nlj, t,1 /t,f, t.2lt*f and 8*oare dependent on q.,.,p lq ; but independent of T. Finally,Relationsivip between 8*o 8nd q****p lqFig. 9.B=0.0'06T 147 (9)When the influence of creep stress r'atio, q*,**p/q,,, andRelationship bet veen ia.m * and q**e* 1q*1RELATIONSHIPS BF.TWEF,N MlNIMUM STRAINRATE AND OTHF,R CREEP PARAMF.TF.RSKato et al. (2004) pr'oposed a creep model for softrocks, in ¥vhich all the cr'eep parameters in Eqs. (2) to(7) are determined from the creep stress ratio, q***=plq .In their model, the influence of temperature ¥vas nottaken into account, as these creep parameters ¥vere foundq****p lq*, while that of the secondar'y creep stage becomesshorter. Moreover, neither t*1 It.f nor t.2lt.f appears to beindependent of temperatur'e, T, in their experimentaldependent on T.the third type of creep parameters,Figure 9 sho vs the relationship between the initial axiaistrain, 8so, and q.,eep lq . The values of s*o increase frompendent on T, especially for T> 60'C. Other researchers0.20/0 to a little over 0.30/0 with the values of****pq lqufrom 0.6 to I .O. But they appear to be independent of T.Figure 10 sho¥vs the semi-logarithmic relationshipbetween the minimum strain rate' *, ,", and q /q The'*'* ".logarithmic values ofa *appear t,o increase linearly.with q.,..p /q. at a similar rate for respecti¥'e temperatures.data for 20-60'C. However, our test results sho¥ved that*, i* and t*f, are de-also reported this temperature dependent nature ofcreep behavior for sof't rocks (Yamabe et al., 2001;Jo et al., 2005; Kodama et al., ,_005).In this study, focus is placed on the minimum strainr'ate,*, i , because it is the first creep parameter to bedetermined in the analysis of creep tests ¥vith utmostcredibility and least scattering (Shibata et al., 2005). CREEP BEHA¥,IOR OF TUFFACEOUS ROCK!05l 0IG5 r __ r c) I s o 60 so"¥f,e'- ' o <e. -'-'¥1io []_ i04/A j'..1?:J'flo{o'f----''v Eq(ll) --' : ' j_'loEq(15)* "*cI f fE ' io). ; il"- ii o --Eq 1 1-' ) :¥' ' O 3s eo -' T / 'e } I oe _O1. : .T('C) 24 40 60 80e llo -Oola'l O s : O' I 01 O S i 0+ I O ; I OI (rllo s 1(r7 lO'ti iO's loOe I Omn (o/o/min)sFig. 12. Relationship between t*r, t*i, t*2 anda,mi*Fig. 14.o' Io'=a+:EJnRelationship bet,veen e*o and ia *i*, i-o 3-O 6- O 92 Iocr+ 2.32' ': "'m "t <C> o >J _/¥Figure 14 sho¥vs the semi-logar'ithmic relationshipAe>! ,between 8ao andT( 'C ) 24 40 60 so 95*1 210 10 iOa ,m*n･ . The values of eao increase linearlywith log-cycles of *,**i**. The following equationobtained by regression analysis.- -OS-1 S- 1) (13)ln3 = - 0.733 (14)Eq (13)Eq (14)lO i ICo ICl(( /c/min)ml = - (logOoc AmE ･<>A vm oo c]vas then+0.35e*o = 0.023Iog b (15)a,minIt is interesting to note that, the relationships bet¥veenl('5 10* ICr= ICr: Iorl 10 10and other creep parameters are unique as expressed*,m*", mi* (c; 7c/min)by Eqs. (10) to (15), and are dependent on neither q.,.ep/q* nor T.Fig. 13. Relationship between nll, nl3 and i*. j*IMPROVED CREEP MODELFigures 12 to 14, thus, show the relationships betweenand other creep par'ameters obtained under different*,**:Featu/'es oj' hnproved C'reep ModelImpr'ovement vas made on the cr'eep model proposedFigure 12 shows the double lograrithmic relationshipstemperature. This improved model succeeds the basiccreep stress ratios, qc'ee lqu' and temperatures, T.by Kato et al. (2004) to take into account the infiuence ofa,min dependconcept of the original model, that the changes of strainon both qc'eep /qu and 'Tas sho¥vn in Figs. 7 and 10, respec-rate with time are typically expr'essed by Eqs. (2) to (4) fortively. But, the relationship bet¥veen tcrespective creep stages as sho¥vn in Fig. 1,5.In the original model, all the eight cr'eep parameters aregiven as functions of the creep str'ess ratio alone, and nobetween t*1' t*2, tcf anda,min' Note that t*f andanda,min becomeslinear and unique, and is dependent on neither qcreep lqunor T. The following equationvas then obtained byregression analysis.I Ol loa I- .37 (10)log -tcf=' c a,m*nThe similar relationships bet¥veen tcl ' tc2 anda, in are alsorepresented by sub-parallel lines as expressed by thefollowing equations.log t*1 =O 92 Io(:j- I .68 (1 1)log t.2= '- I a,m**03 IoCT- 1.59 (12). ,:' *,"****Figure 13 shows the semi-logar'ithrnic relationshipsbetween lnI m･' 'anda*ml*･ 'While the values oflnlincreasewith log-cycles of a*i ' the values of ln3 seem to beindependent of a****'･ The r'espect.ive relationships for mland ll73 are represented by a hyperbolic function of *' *',and a constant, r'espectively.attention 1¥'as paid to the influence of temperature.However, as explained earlier, the test results on Ohyastone shol¥'ed that some creep parameters, *,*i** and t*f,are dependent on not only q*,**p lq*, but also T (Shibataet al., 2004).In order to take into account the influence of tempera-ture, the method to determine the creep parameters aremodified. Creep parameters are divided into two groups.The ones are intrinsic properties, i.e.*, i , t,f, t.1, t,2, nlj,ln3 and 8*o. And the other is a reference value, i.e.**.The seven intrinsic creep parameters are determined int¥vo steps. Firstly, the minimum strain rate, *,*i , isevaluated from creep stress ratio, q***,p lq , and tempera-ture, T, using Figs. 10 and 11 or Eqs. (8) and (9).Secondly, the other six parameters are estimated from thevalue of*,*j* using Eqs. (10) to (1 5) Ivhich are unique and 8SHIBATA ET AL．εa（iogscaio）丁段b鳳e2． ■he v貸垂ues of COV for e段ch creep P鼠r段meterPoint＼、、 、 Dlf艶ro臥9￠謹ぐPguユ霧ご7’εar獣＼．。ノ＼ Creep Kato et ai、pa「ame［e「 Thi （2004）log（ら、繍） 0．31Eq（2） ’ Eq（4）、 ＼ E蝋12）O Endoピprf爬【yc鯉P￥・、E鰍11）＼ピMudsto鷺e0鮭yaStone＼ レ！！ の1ゴfcr。n：’遇隅，n） Kaεo et al．【udy Tl誠S Study （2004）0．260．230、19lo9（∫亡r）0、670．590，300．Z8109（fd）玉．050．930。260．26109（∼C2）0．770，690，250．25’ni0，130．090．190、i817∼零0．100．100．640。640．860、090．870．i4 、 、 ＼g E網σf瓢（〕臨r｝oreOPPr＝m畠ryα岬sミccnd訂y。脚丁￠『瞳ピ“eごPごcrも （iO9㏄aie〉εユo（％）Fig．15。 Co獄cept of tbe proposed creep mode皿respectively．The extrapolate（i li歎esξor the primary creepapPear to conveτge at a singu歪ar point in early part of the10三creep behavior．Th量s un量que po量nt，1，玉s arbitraτily takenas（1。，，εa，）＝（1．0×10−4minute，10％／minute）for Ohyastoue and（1。，，ε、，）＝（1．0×10−4minute，40％／mlnute）forMudstone．尽／茎0α’1層α（7ッ0ゾ’1）ξ∼∼θ1岬1ηi17ing C1でθp Pα19σ1nθ∼θ1写 Table2compaτes the coefficleat of variations，COV，’沁for the intrinsic creep Parameters obtained for both Ohyastone＆nd Mudstone．These valuesτeprese勲t the accuracyoぐthe proposed reladonships to（ieteτmine the indivi（iual104 三〇『’ 1σ2 10’【 三〇〇 10三 10ま 1σ 10ξ 10《 Ioo ‘c（min）creep parameters，i．e．Figs．10−H，12−140r Eqs．（8）to（i5）． （al The（iata of Ohya stone sぬows that，of all t封e creepparameteτs except1η3，smal玉er values of COV are ob−Fig，玉6（9）． Rel段額ons匪灘ip bet、veen6ユandゴc for Ohy段s｛onetained for tぬe proposed method than由ose for Kato et aL（2004）’s metbod．Similar trends are seen for the data of103 7罵60℃10∼守認，ノ9、誤〕71 アゑぴじ10！100Mudstone．Tむe reason for顔s improvement is that，asshown in Figs．12to 14，the strongeτcorrelations werefound between the minimum strain rate，ε、，min，whichreHects the variations of specimens，than the creep stress、ratio，σ。，。，p／σu，and the o出er lntrinsic cτeep parameters．芝ま『鴇10『E1σこ！icαイ1層αcツoプrル哲04θ11ng C14εθp Bθhαvio1層10『3 Comparison is made for creep behavioτbetween theexperiment and由e proposed modeL Figures16（a）and1041σ｝1σ6國 9課”F・ 9；濫｛｝・79104 1σ♪ 10二 1σ卜 王00 10己 三α 105 10‘ 1G5 ’c（min） （b）Fig．16（b）．Rela重ionsilip be載wee服ε該and f。for MudsIone16（b）sむow the relationships between strain rate，εa，andcreep time，∼c，for Ohya stone and Mudstone，respec．tively． Furthermore， Figs． 17（a） and 17（b） show therelations娠ps betwee熱creep strain，ε巳，and creep time，1、，for the respective rocks．The open symbols imply theexperimenta1（iataラwhile the broken curves imply theproposed model， Overall agreement between t封e experimental data andthe pτoposed model ls good，although some extents ofdependentonne量ther（1。，，ごp／（1unorTasshowninF呈gs．12deviation aτe observed for Ohya stone at T翼800C aadto14．g。，，ピp／σ、翼0．88andギor Mudstone at T＝20。C andσ。，，ピp／ For the reference creep Parameter，assumptions are9、瀟0．86．Hence，it may be coaclude（i that the proposedmade that the creep bebavior starts from a certain point Ias shown in Fig．15。Figures 16（a）an（i i6（b）show therelat量onships between strain rate and creep time for Ohyastone by this study a熱d！〉1udstone by Kato et a圭．（2004），model is valid foτboth Ohya stone and Mudstone toYepresent creep behavior under vaτio毫ls co熱d至tions ofcreep stress ratios and temperatures． 9CR班…P BEH、へVIOR OF TUFF．へCEOUS ROCK05000 τ；ウり℃ ぐ 1属ユ4℃9茸，．ア9．憩s4 9欝宵刃メl ssrCc）24 4＝π1 昏9 8り 肇51＝二4℃ 9 口 φ ム ▼一〇39、豊066 A −06 1η1騙07809＝，，F9』143 ＼ Ψ v φ轡劉 一〇9 φ 幽幽”“』幽qqq＾＾“幽幽”僧一醐”曹鞘”v魯｛“薗蟷 42N 繍…蝸i麺：F飢1…漁5 ”1・二‘1Q9﹁‘1﹃％挿020嗣062一15104 10『」 1σ3 1σ1 100 10【 10z iσ 10‘ iO》 10604 05 06 07 08 09 10 11 9α、ごP！9u rc（min） （a）Fig。18． RelaIio霧1ship beIweenη11a鳳d gc，日￠p／g口Fig．17（段）、 Rei郎ionshlp betweenε凱＆nd∼。for Ohya sto臓e1「6series of creep tests w＆s conducted under uncon負ned1長2。毛i薩． 18l 劃卜、σC 9“。ア望。蔚s6 熱σ一・一9・勇72condition on a tuffaceous rock，Ohya stone，at creepstress ratios，σ。，。，p／σu，ranging from O．6to1。0、Empirlcalrelationships＆re玉nvestigated for the three creep stages，i．e．，primary creep，secondary creep and tertiary creep．14The fo1玉owing conclusions are（iraw簸．ま ユ2（1）Themlnimumstrainrate，εa，．、i，，andthetimetocreepfailure，！。f，arefounddependentol主bothσ。，。，p／σu輸 100806妻箋萎萎嚢萎ζ鷺釜轟and T。The inHuences of T become more evidellt forhigher tempeIlatures above60。C．However，由e rate ofaccelerat玉on of strain rate in tert玉ary creep，1n3，apPeaII to 鶴，評．試｝71104 三σ3 10一二 玉0具 100 ！OI 10： 1σ 104 10》 ’c（mln） （b）be dependent on neither（1。，。，p〆（1、監nor T．Fur出ermore，therate of deceleratlon of sξrain rate in primary creep，〃71，and重he relative time bounding童he three creep stages，‘。…／1。fand1。2／∼。ガ，aredependentonσ。，。，P／σulbutindependentof T．Fig，17（b）．Relationshipbe重weenεユ貧nd∫，forMqdsto騰e（2） Focus was placed on the minlmum straill r飢e，ε、、min，becauseε、．min is considered as most represen重atlve of creepbehavior and can be determined wl重h reasonable accuracyCONDITION TO CAUSE CREEP FAILUREan（i confidence．Un玉que rela書ionships betweenεa，ロ，in and Although the condition to cause creep failure is lm．t紅e other creep Parameters，オ。f，1。1，∼c2，〃11，1113andε撫o，areportant from the englneering point of view，疑is raξherfound，andtheyapPe＆rtobedepellde臓tonneltherσ。，，，碧／dif資cult to tell whether creep wlll dimlnish or enter thetert玉ary creep豆eading to fai互ure．The condition of uniaxiaIσu llor T．（3） In order to take into account the il1Huence of tem−creep fa琵ure is d圭scussed in the fo1豆owing．perature，a new metho（l for detenniaation of the c！’eep From the concept oftheproposed creep model，as seenparameters was proposed for tぬe Klato et al．（2004）ラs重n Fig． 15，圭f the strai煎 rate continue to decrease andcreep modeLτhis metho（1was justified as valid，as goodwould nQt en重er童he secondary creep，creep failure wi1豆agreement was observed betweα1the model and the testnot take p至ace。This non−fa呈1ure conditiou is rea豆ized，ifresu至ts for both Ohya stone and Mu（istone un（ier variousthe slope of the line expressed by Eq．（2）for t紅e prim＆lycreep，1n1，is greater than that of the line expressed byEq．（11）for the creep tlme to enter the second＆ry creep、As shown ill Flg．18，the value of〃11灘（』logε、／沼∼。）；1／（一〇．921）篇一1．09 and 重he regress玉on Hne 〃1歪；0．780（σ。，，，P／σu）一L43provide重hecriticalvalueofcreepstress ratio to boun（i the fa圭lure condition to the non−failure conditionεしs O．44．Sillce〃21is not dependent oncondit呈ons of creep stress rat玉os and temperatures、（4） Accordi勲g to the proposed model＆nd重he ex−pelimental da｛a，重he creep fa玉至ure will not｛a盆e place if thecreep stress ratio is lower than O．44for Ohya stone． Fur重her study is nee（ied by triaxial creep tests ullder難igh temperatu11e to investigate the inHuence of con且nlngやressures、Moreover，the i亘且uence of loadlng rate to theiatended creep stress，（1。，馨。p，shou互d be investigated fortemperature， this crit主cal value is independent of themore rigorous determination of the relevant creeptempera重ure，parameters，CONCLUSIO翼SACKNOWLEDGEMENTSUnder different temperatures，T，from24。C to95。C，aSincere thanks are glven to Mr．Yuji Miho，＆gr＆duate 王0SHIBATA ET AL．stude鍛tGfYokoh＆maNatiQnαIUnivers圭ty，fGrprovid三ngvaluable experimental data．7）Kuwabara，K， （1984）：αassl費ca【io簸of rocks by compresslo職and shear strengtむs，，ノ．oゾ“／SEG，25，Special issue，25−33、8）MatsumotQ，M，Hayano，K．，Sato，丁．，Koseki，」．andTaζsuoka， F。（1999）：τimee匪ec【sonstress−stralnpropertlesatsmallstrainsofRE、FERE、NCES sedime蹴arymudStO鷺e，Proc．211ゴ加．Sアη7μoηP’『θ一ノiα〃ε’1ぞ 0εブ01”’nα∫io／1Chαヂρc∫θ鷹’ic50∫Gθo〃7σ∼θr酪，1，3B一一321，1）Hα【ema，M．H，R．，dePeter，C．，」．andWoif，K．一H．A．A， （1991）：9） 氏4茎ho，Y．，Tan玉，K．，Sh玉bata，K。and Okada，T、（2005）：Inaue頁ce of 照ectsofしemperatureaRdpQrewaζero願creepQfsaRdsto魚erock， ro（：k type QR creep be亘av圭or Qbserved in uncQ【L蕪Red creep tests， Ro（♪んハ4θご乃α11’（〕5α5‘7ル∫置〃∼’ゴ直∫ぐ’ρ1〃∼θ1ツSciε’∼ぐθ，Baikema，393−404． Proc． 34〃∼ Sア〃∼ρ． 017 1∼ooん 1Vθchθ’∼’c5， JSCE， 495−500 （1“2），lapa臓 Nuclear Cycle Developme煎 1nstituこe （2000〉：Projecεεo establish 覧難e scienεiftc and tec鮭nica互bas呈s for HL∼V disposal玉n ，∫apan，2nゴP1909ノ■e5∫」R（∼ρ07’011Rθ5θθ1でhα’7‘1∠）θソθ10ρノ11θ17’，ノ101明11∼θ Japanese）．10）Nakajim呂，T。，Tani，K．and Okada，T、（2000）：Experlme熈al sωdy ond罫ai照geco繭乳lonofln−s1τu【ri＆xiahestonrockmass，P1「トo‘． Gθ0109’cα1∠万5ρ05α10ゾノゾ1，μ！’η／α〃ση，2，4．2Design of d1sposal 35’11SJ棚μoηGεαθc1∼，Eη9。，JGS，1001−1002（lnJapanese）． fac玉1ity（in Japanese）H） Nuc菱ear V》7aste1〉lanagement Organ玉zadon of Japan（2003〉＝Geolo9一3）JQ，M、，AQki，丁。，Ogawa，T．a跳d Ya磁abe，丁．（2005）＝E琵ect Qf tem− 玉cal dispQsa玉，cQnsiderat玉Qn Qn safety，NU！ヤ10，！50（in Japanese）・ peratureon由e鵬echaRlcalbeわaviorsofadiatomaceousmudsto麟e，12） S｝1玉bata，K．，TaRi，K．and Okada，T，（2004）：Uncon島職ed creep test Plo‘． 34∫h 5）ワηρ， oη 1∼ocん ∫、ゲθchθ11’c5， ，ISCE， 177−182 （in Japanese）。 of tu鐸 at ｝1玉9ぬ 芝empera【ure， P！ηc、 ．39’h ノ‘47α11 八7‘7’． Co〃プニ oπ （｝θo∼θごh・五π17g・，571−572（玉n．lapanese）・4）Kato，Y．，Tanl，1く、andOkada，T．（2004）：U獄con且nedcreeptes葛of soft sedimen【ary rocks at higll こempera【ure and proposal of夏3）S短bata，K．，Tanl，K．and Okada，T、（2005〉：Uniaxiai creep test of prediαion model for creep beぬav1or，P1’oご、33擢Sダη1ρ．oηRoごん st面n raεe and creep parameters一，Pヂoご。34∫h S）ア〃∼μoηRo欲 Ohya s【one at hig猷emperaωre−Relat1o且ship beしween min三mu礁 西∫εchα刀1c5，JSCE，25−32（玉簸，Iapanese）． A4echρηκ5，，ISCEラ玉一8（玉n Japanese）．5）Kodama，N．，ヂujil，Y．and Isllijlma，Y．（2005）：Ef￡ects ofτempera−14）Thlmus，J．Fr．and De B田yn，D．（1998）：Long−term由ermo− me麟anlcalbehaviorofBoomclay，ThθGεo！θ‘ノ1’7’c50ブHθπ1 ture on creep beむavior of Inada granite a臓d S頴rabama sandsto鷺e， Pノ曹o（r． 34∫h S．｝ワηρ． oη Ro（汝 」、グθc1∼αη’c5， JSCE， 183−188 （in ，Japanese）． So’Z∫一Soゾ∼Roごん5，Balkema，337弓41．15）Yamabe，1〉1．，｝vl圭yamoto，A．，ho，F、and Tan玉，τ．（2001）：Evalua−6） Kurロmura，丁．，Tani，K，and Okada，丁．（2003）＝Experimental sヒudy t1on of creep be赴avlor ofsoft rock u鷺der non−iso由ermal co疏d三t1on andmodelingofscalee牙ectonstre澱g由c擬aracteristlcsofO簸ya and i1s apPl套cab玉1i［｝r for numer三cal analys玉s，Pノ’oc。31∫1＄yn1μ 011 sto鷺e，Proo．32η‘1Syllrρ．oηRocたム4θ（7hαη’c5，JSCE，107−112〔in Rocたノ》θ‘ノ7θη1c5，JSCE，231−235（in、｝apanese）． ∫apaRese）、 | ||||
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| タイトル | A Thermo-poro-visco-plastic Shear Band Model for Seismic Triggering and Evolution of Catastrophic Landslides | ||||
| 著者 | N. Gerolymos・I. Vardoulakis・G. Gazetas | ||||
| 出版 | soils and Foundations | ||||
| ページ | 11〜25 | 発行 | 2007/02/15 | 文書ID | 20976 |
| 内容 | 表示 SOILS AND FOUNDATIONS¥!ol 47, i¥ O_ l,l25, Feb2007Japanese Geotechnical SocietyA THERMO-PORO-VISCO-PLASTIC SHEAR BAND MODEL FORSEISMIC. TRIGGERING AND EVOLUTION OFCAT'ASTROPHIC LANDSLIDESNIKOS GEROLY rosi), IOANNiS VARDOULAKlsii) and GHORGE GAZHTASiii)ABSTRACTThe goai of this paper is to develop a constitutive model for the rapid deformation of clay-rich shear zones. Such amodel ¥vould be necessary to descr'ibe the seismic triggering and evolution of catastrophic landslides. The model isbased on: (a) the ¥vell-documented in the literature strain-softening and viscoplastic behaviour of saturated clays,and (b) the concept of frictional softening due to heat generated pore-water pressures. T'he inelastic stress-strainrelationship is described with a 1-dimensional cyclic constitutive model of the (Bouc-Wen) type, coupled ¥vith aCam-Clay frictional la v vith hardenin_ : and a set of equations that govern the mechanism of heat-generated porewater' pressure build up. Calibration of' the model parameters is accornplished through laboratory tests, ¥vith the helpof artificial neural net¥¥'ork analysis. The infiuence of key variables on the behaviour of a rapidly deforming shear bandis thoroughly investigated and the resuits of the analysis are critically discussed.Key words: catastrophic landslide, clay, heat generated pore-¥vater pressures, neural net¥vork, shear band, thermoplasticity, thermo-poro-viscoplasticity (IGC: B3 /E8/E14)particles present in the soil:INTRODUC1'10N(a) A turbulent mode, in soils ¥vith high fraction ofDynamic deformation of a saturated clay-rich shearrotund particles (i.e., with cla)' fraction lower thanband involves strongly coupled material nonlinearities,20-25010), or vith platy particles of high interparticlesuch as: (a) strain softening (s!ow residual strength), (b)friction. The slo l' residual friction angle (the shearstrain-rate dependencyst residual strength), (c)thermo-viscoplastic softening due to heat-generatedstrength at slo v displacement rates) is hi**h anddepends mainly on the shape and packin*' of t.herotund particles, rather than the clay mineralogypore-¥ 'ater pressures, and (d) hysteretic stress-strainbehaviour.Numerous experimental results in the literature sho¥vthe relationship with the aforementioned mechanisrns of(kaolinite, illite, montmorillonite, etc).(b) A sliding mode, in soils ¥vith high platy clay (lessthan 2 ft/m) fraction generally larger than 400/0500/0 .of platy particles, clay mineralogy, pore water chemistry,coefficient of interparticle friction, overconsolidationratio, mean normal effect.i¥'e stress, fraction of rotundparticles, existence of particle orientation, etc).The residual strength of soil at slow drained shearin*"A Iow-strength shear band of preferred platy particle orientation develops. Slo¥v residual str'ength ismainly controlled by the interparticle friction ofclay minerals, clay rnineralo*'y, pore water chemistry, and normal effective stress. Skempton (1985)suggested the followin*' typical values for represen-rates has been studied extensively during the last fourtative clay minerals: 15' for kaolinite, 10' for illitedecades. Various correlations between slo v residualstrength and index properties have been proposed (e.g.or clay mica, and 5' for montrnorillonite.(c) A transitional mode, in ¥vhich there is no dominantLupini et al., 1981; Bishop et al., 1971; Skempton, 1985;particle shape (platy or rotund), ¥vith clay fractionBromhead and Curtis, 1983; Tika and Hutchinson,bet¥veen 200/0 and 500/0. Shearing involves both1999). Lupini et al. (1981) utilised the r'esults of a largeturbulent and sliding behaviour at different iocationsnumber of ring shear tests on natural soils to study theof the shear zone. In this mode, slow residualseveral index properties of a clayey soil (e.g., the fractioncontrolling mechanisms of residual shearing. Theystren*'th is sensitive to srnall chan*'es in soil grada-pointed out that three modes reflect the quantity of platytion.i}i,iii)Post-Doctorai Research Civil Engineer, National Technicai University of Athens, Greece (gerolymose*mycosmos.gr).Professor of' Applied Sciences, dittoProfessor of C ivil Engineering, ditto (gazetas@*ath,forthnet.gr).The manuscript for this paper vas received for revielv on July 7, 2005; approved on Juiy 26, ,-006.¥Vritten discussions on this paper should be submitted before September l, 2007 to the Japanese Geotechnical Society, 4-38-,_, Sengoku,Bunkyo-ku, Tokyo 1 12-001 l, Japan Upon request the closing date may be extended one month.11 CJEROLY 'IOS ET AL.12The infiuence of pore ¥vater chemistry upon the residual strength of pure and natural clays, exhibitin_ : thePe k tr ngthq,sliding shear mode, has been studied by several researchers (e.g., Moore, 1991; Anson and Ha¥vkins,lf1998). They demonstr'ated that the type and concentra-Fast res du3 Sta'e(at large veloeities)102400Displ cement : mmFig. 1. Idea]ized evolution of the mobilized friction angle during t il esiiding process in a ring shear apparatusfriction an*･le of about '-', for a calcium-exchangedkaolinite compared ¥vith a sodium-exchanged kaolinite.The increase is larger, reaching 5', ¥vhen the predominantclay mineral is montmorillonite. Salt concentration ¥vasalso found to influence the residual strength. An increase,of about I ' to 2' in the residual friction ang:le of L,ondon3sTU TRSSh5 r, Q eeo2s20and ¥Veald Clay (¥vith illite the predominant mineral),respectively, Ivas reported by Moore (1991).IsAlthou h numerous studies ha¥'e been carried out10regarding the residual strength of clayey soils tested in the5Pt8teE eCOrin*･ shear apparatus, only a fe¥v of them ¥vere dedicatedto the fast residual strength, i.e., the ultimate strength atAccording to their research, three types of rate effect onthe residual strength are identified:(a) A positive rate effect,in soils sho ¥*ing a fast residuali (prOC ciayresults of a series of ring shear tests on saturated clays,sho¥ved that alteration in residual shear strength (causedfast displacement rates. Tika et al. (1996) studied thefast shearing response of pre-existing shear zones andpresented results for a ¥vide range of natural soils.SleYi residu 1 si t(Pr sresidual shear strength. Moore (1991), exploiting theparticles. He reported an a¥'erage increase of the residuale{gt large dispiaeemenis)tion of cations in the pore ¥vater significantly affects theby the presence of exchangeable cations in pore ¥vater)increases with increasing specific surface area of clayCri e { SlO 200ROEO100Clay r 0t:en C*Fig. 2. Dra"rammatlc correlat on of sloll resldual fr]ct]on angleththe cla)' fraction: The three regions of different sl]ear mode bel]av-iour (TU. TR, S) and the tl]ree regions of different consequences(neutra], negative, positive) of the rate of shearing on residuaistrength, are: The error band of the single experimental pointrepresents the effect of pore'ater chemistry on residual strengthstrength higher than the slo¥v one This type ofviscous behaviour is associated only ¥vith the sliding(even enormous) velocities are developed in catastrophicshear mode.landslides. For example, referring to the disastrous(b) A negative rate effect, in soils sho¥ving a significantdrop of fast residual stren_ :th belo¥v the slo¥v resid-Vaiont slide, back-analysis indicated that the sliding massual str'ength, when sheared at rates higher than ato 40m/s (Mench, 1966; Habid, 1967, 1976; Goguel,moved some 400 m, reaching a maximum ¥'elocity of ,_Ocritical value. Soils with transitional or slidin shear1978; Muller, 1964, 1968; Ciabatti, 1964; Voight andmode may exhibit this type of behaviour. In someFaust, 1982; Vardoulakis, 2002). It is thereby evident thattests, fast residual strength was measured to be asthermo-poro-mechanical behaviour of clays is a criticalissue in the evolution of catastrophic landslides. Nevertheless, it is pointed out that frictional strain-ratelo¥v as 600/0 of the slo¥v residual strength.(c) A neutral rate effect, in soils sho¥ving a fast residualstrength nearly equal to the slo¥v residual irrespecti¥'e of displacement rate, associated ¥vith the turbu-lent shear mode.Tika et al. (1996) clarified that: (a) the fast residualstrength is reached ¥vhen the displacement rate surpassesa critical value; (b) stren>'th is sli*･htly affected by excesspore ¥vater pressure arisin*･ from the contractivebehaviour or from heatin_9: of the clay, and (c) thenegative effect on residual strength results from theincreased soil flo¥v potential due to ¥vater absorption bythe shear band, caused by its diiati¥'e behaviour.Ho¥vever, the critical velocity required to reach the fastresidual stren th ¥vas measured to be in the order of O^005m/s to O.1 m/s. This is far smaller than the one requiredfor initiation of heat generated por'e ¥'ater pressures,¥vhich can be of the order of fe¥v meters per second foroverconsolidated clays (Vardoulakis, '_002)^ On the otherhand, it has been proven by several researchers that largesoftening ¥vithout heat-*･enerated pore-¥vater pressuresmay, under cer'tain conditions, Iead to accelerated creep(Vardoulakis, '-OOO). This means that frictional ratesoftening behaviour is by itself a significant destabilizingf actor.The abo¥'e conclusions on shear behaviour of clay areelucidated in Fig:s. I and 2.It is ¥vell documented in the literature that clays arethermo-viscopiastic materials (Campanella and Michell,1968; Nova, 1986; Hueckel and Baldi, 1990)Hicker(1974), Despax (1976), Modaressi (2002), and L,aloui andCekerevac (2003) reported that some clays demonstratethermoplastic softening behaviour, r'efer'ring to theirfriction coefficient in the critical state, ¥vhile others ar'epractically unaffected by temperature. Modaressi andLaloui (1997) pointed out that ¥vhen a clay sample isheated slo¥vly enough to allolv complete draining, t¥vophases of behaviour can be distinguished: SHEAR BAND ivIODEL' a reversible phase, termed "thermoelasticity", dueto diiation of the miueral cornponents, and' an irreversible phase, termed "thermoplasticity",caused by both dilation of clay minerals and collapseof the absorbed ¥vater, resulting in failur'e of someinterparticle ties.Exper'imental vork identifies that the response of anoverconsolidated (OC) clay in thermal loading is differentfrom that of a normally (NC) to slightly overconsolidatedclay. In an OC clay, thermoelastic dilation during theheating phase is followed by thermoelastic contractiondur'ing the cooling phase. In a NC clay, thermoplasticcontraction during the heating phase is usually followedll)va- ( )T (t)Ut)v )d ti] 8(t{t' u{t} __' iIl--:--. / oS e rFig. 3.ndSchematic illustration of the shear band modelby additional thermoelastic contraction during thecooling phase. Ho¥vever, Sultan (1997), and Laloui andCekerevac ('-003) sho ved that at high temperatur'es,above a critical value, overconsolidated clays sustainthermoplastic contraction as ¥vell.In drained loading conditions, therrnoplastic contrac-the forrnation of the shear band (at the critical state), and(iii) a visco-plastic model for strain and strain-ratesoftening at large displacements (residual state).A comprehensive methodolo_ :y for calibration of thetion. Under undrained conditions, the natural trend ofmodel parameters, is also presented by resorting topublished experimental data. Closed-form expressionsare developed from correlation of the key parametersthe soil for thermoplastic contraction _g:ives rise to anwith characteristic index soil properties, making use ofincrease in pore ¥vater pressure, ¥¥'hich in tur'n results inartificial neural network analysis.The objecti¥*es of the paper are (a) to de¥'elop a sheartion results in shear strength increase due to soil densifica-frictional softening. On the other hand, thermoelasticdilation either would not affect at ail or ¥vould only slight-ly increase the soil shear strength. The preconsolidationstr'ess is also affected by temperatur'e, being a decreasingfunction of it. Thus, under drained loading conditions astemperature increases the br;ttle and dilati¥'e behaviourof an overconsolidated clay alters to a more ductile andless dilative (or even contractive) behaviour.Vardoulakis (2000) starting from a set of axiomaticprinciples, rcformulated the equations that govern themotion of a rapidly and monotonically deforming shearband. The soil vas considered as a t'o-phase mixture ofsolids and fluid, and the governing equations werederived from the corresponding conservation la¥vs ofmass, momentum and energy. The resulting governingequations are t¥vo coupled difttrsion-generation partialdifferential equations, containing t¥vo unkno¥vn functions: excess pore-¥vater pressure and te nperature insidethe shear band. The ¥'elocity field is consider'ed as anband model for the analysis of seismic triggering andevolution of catastrophic landslides, (b) to present amethodology for calibrating the model parameters ¥vhenrelevant experimental data is scarce, and (c) to per'for'm a(limited) parametric analysis of a dynamically deformingshear band.The ps'oposed model aims at joining theoretically theinitiation of a landsllde due to seismic loading and ther'esponse of the slide at extremely large deformations.According to the authors' knowledge only a limitedamount of studies is devoted to this issue, including ther'ecent ¥vork of Chang et al. (200) ).CONSTITUTIVE MODEL: EQUATIONS ANDPARAMETERScalibrated the model parameters on experimental data,Prob!eln DefinitionThe problem studied is that of a deformin*' shear bandconsisting of saturated clay, subjected to shear loading.The shear' band is considered of' infinite length and ofthickness db (Fig. 3). Both of its boundaries are assumedexternal loading, and therefore is presumed known.He applied his model to analyse the Vaiont slide, havingfrorn the literature. Strain and strain-rate induced fric-impermeable to fluid fio¥v and nonconductive to heattional softening was also considered in the analysis byflux. This means that the field ¥'ar'iables in the shear band,utilising results from ring shear tests on Vaiont clay speci-namely excess pore vater pressure p, temperature 6, andshear strain y, are 'unctions only of time t. Such boundary conditions imply undrained and adiabatic response,mens conducted by Tika and Hutchinson (1999).In this paper the governing equations of heat-generatedpore pressures inside a rapidly deforming shear band, aresummarised. Their forrnulation is limited to adiabaticand undr'ained response conditions. Then a constituti¥'emodel is developed consisting of the aforementionedequations, coupled with: (i) a 1-dimensional Bouc-Wenwhich is realistic ¥vhen the shear band is deformed at largevelocity, as it is generally the case in a catastrophiclandslide. Excess pore water pressure and heat would nothave the time to dissipate rapidly, especiaily vhen thethickness of the shear band is relatively lar'ge.We assume the shear band thickness to be constanttype constitutive model (Gerolymos and Gazet.as, 2005)for the hysteretic stress-strain behaviour of the shearband in cyclic loading, (ii) a Cam-Ciay model with aduring the slidin_"_. process. It is noteworthy that theevolution of shear band t.hickness with displacement ishardening rule for' the frictional behaviour of soil beforenot well documented in the literature (Otsuki, 1978; 14 CJEROLY+¥,iOS ET AL.Waterson, 1986; Drescher et al., 1990). It is assumed hereb*05considered. The behaviour before shear band formationis modeled ¥vith a Cam-Clay frictional law (ModaressiLb=05et al., 1995). In that stage, volumetric strain rate is alsoconsidered. Eventually, the hysteretic stress-strainbehaviour of the shear band is described ¥vith a BoucWen type model such as the one presented by Gerolymosand Gazetas (2005)..bson=1Mode! ,fol' F/'ictiona! BehaviourA versatile one-dimensional macroscopic model isutilized to describe the shear stress-strain relationshipinside the shear band. The model is capable of reproduc-Fig. 4.versus normalized displacement u/ul curves for differentvalues of parameter n for monotonic louding and different b valuesfor unloading-reioading h,.Tsteresis loopsing an almost endless variety of stress-strain for'ms,monotonic as ¥vell as cyclic. Based on the originalproposal by Bouc (1971) and Wen (1976), the model ¥vasextended by Gerolymos and Gazetas (2005) and appliedto cyclic response of soils. A simple version of the modelis briefly outlined here.The shear stress r at a particular time t is expressed as:r(u( t )) = r.(u( t ))(u( t )) ( I )Equation (6) implies that the ratio r. /uv is the initial stiff-ness of the shear band (in units of kN/m3). From Eq. (i)it is obvious that the ultimate shear strength, r+, isreached when tends to 1. For monotonic loading themaximum value of ( is obtained by settin_9: d /du = O, andby virtue of Eq. (3) this maximum takes the value:i¥vhere u is the lateral displacement (tangential to thesliding surface), r+ is the ultimate shear strength of soil,and = (u(t)) is a dimensionless "hysteretic" parametercontroiling the nonlinear response; it is expressed ¥viththe follo¥vin_ differential equation:dI - l-=- b - i 1'"+(1 -b) du I ) JI [[4(_(*,** I = I (7)From Eqs. (3) and (7) it is obvious thattakes valuesbetween - I and I .Parameter n governs the sharpness of the transitionfr'om the linear to the nonlinear range, during initialvir*'in loading. It ran*'es from O to eo , ¥vith elastic-perfect-d t/(2)ly-plastic behaviour practically achieved ¥vhen ll takesvalues *"reater than 10. Values of n bet¥veen 0.6 and 1in ¥vhich: tt is the lateral velocity; uv is a parameter signal-have been found to better fit experimental resultsing the end of elastic slip (a rigid plastic behaviour is ap-(CJerolymos and Gazetas, 2005). Parameter b controls theshape of unloading-reloading curve. Its range of values isbetlveen O and I . When b =0.5 the stiffness upon loadin_"*.d tproximated by assuming a very small value of u*, say lessthan < 103 m). n and b are dimensionless quantities thatcontrol the shape of the hysteresis loop. Equation (2) isobviously of a hysteretic rather than a viscous type.Hence, its solution is not frequency dependent. Byeliminating t, it can be rewritten in an incremental d -duform:dcI {1-1 i"[b (1 b)slgll (u )]} (3)dt/ u)By differentiating Eq. (1)displacement u:vith respect to the lateraldr dduand obviously that ¥vhenr), du (4)tends to O. Eq. (3) reduces to:parameters, the reader is referred to the recent publication of Gerolymos and CJazetas (2005).The shear strength T. is given by a Cam-Clay frictionlaw ¥vith hardening rule (Modaressi et al., 1995),appropriately modified to be used in conjunction with thehysteretic Bouc-Wen model, and Terz,aghi's effectivestress principle:r+ = !lF(T,'* (8)du u+in ¥vhich /1 is the mobilized friction coefficient, expressedSubstrtutmg Eq. (5) into Eq. (4) one obtains:dT r. _o uc!ureversal equals the initial tangent stiffness, and theMasing criterion for loading-unloading-reloading arises.Monotonic loading curves for different values of ll arepresented in Fig. 4. Hysteresis loops of the parameterversus the normaliz,ed displacement u/u. for selectedvalues of h are plotted in the same figure. For moredetails on Eq. (2) and calibration of the associatedin terms of Coulomb friction an*"le in direct shear:(6)/! = tan q? (9)and SHEAR BAND lvIODEL15is bein_._O formed, at approximately u=0.01 m, the rate of'o evertical displacernent is practically becoming equal tozero.As described in the introduction, the mobilized frictiono e4:coefficient /! is a function of both displacement and¥'elocity. It can be approximated by the follo ving set of'o 02equations:O(a) oo 02c olo Os/t = min {min [(t< to)l/! =! l+ 1-1!r e "uOG04lico ee03p (t = tO) }(14)(15)Ilc* Pc+0.0e02//r _1! , d+ I /1r,de _P'O GeO1( 1 6)ktr,s flr,s /tr,sO-O ) O1where v*0.0002the criticai state, residual, slo v residual, and fast residual-O G 03(b)oo 02o olO 03(= Lt) is the velocity, and ,1* , pl*, p*,= and /1*,d arefriction coefficients, respecti¥'ely. The residual frictioncoefficient pl*, varies bet veen the two extremes: !/*,* andf/, d. The parameters a and control the state of softeningFig. 5. (a) Shear force-tangeutial displacement and (b) normal versustangential displacement, computed with the developed Bouc- Ven-and of rate-softening/hardening of the frictionalCam-Ctal.' mode] (Model parameters: n= 1, b=0.5, k=0.2, ;.=tional sof'tening is irreversible, so it is not recoveringduring cyclic sliding. In other ¥vords, the value of the4000, (1,;0=0.1 MPa, (1*0= 0.3 MPa, and ep= 25')(T,'* = (7,;o(1 - r*), /'= P (10)a,',aresistance, respecti¥'ely. Equation (14) indicates that fric-mobilized friction coefficient /! is computed as theminimum bet¥veen the value of p at current time step(t= to) and the minimum value of p during the previoustime steps (t<to). The critical state coefficient p.. isdefined for a possible state, in which shear' is at constantwhere o',;o is the initial effective stress normal to the shearvolume but with random particle orientation, ¥vhereas theband, and rresiduai friction coefncient /1* Is defined for the state in¥vhich shearing takes place is at preferred particle orienta-the ratio of excess pore water pressure pnormalized to o',',o. The term F in Eq. (8) is introduced toprevent the irreversible volumetric strain from increasingunlimitedly on a dilatant slidin*" surface. It is expressedtion (Lupini et al., 1981).The original Cam-Clay model is not valid after thecritical state point (after the shear band has formed),as :F=1-kln cr,', (11)(T*¥vith(7* = cF*oe ;-,, (12)where }v is the vertical displacernent (normal to slidingsurface), k is a shape parameter, and ), is the volumetrichardening parameter. cT*o is the initial critical pressurewhich is by definition one-half of the pr'econsolidationstress. The evolution of vertical displacement is describedby the following dilatancy rule proposed by Modar'essi( 1 995):dw= -tan /+･,,,,,,,,,,,･･････-Til i !dul (13)¥vhereas the proposed Bouc-Wen-Cam-Clay model isvalid even for displacements larger than those required toreach the residual state of the soil. Furthermore, drainedsoil behaviour is assumed before the formation of theshear band. This is true under the assumption that pore¥vater pressures are generated only due to temperaturerise. As it will be shown in the sequence, heat generatedpore water pressures ar'e associated ¥vith large displacements ¥vhich are usually of the order of Im.Calibration of the aforementioned parameters shouldbe achieved through laboratory t.ests (e.g. ring shear).However, a rnethodology is presented herein for relatingthose parameters to key index soil properties or stressvariables (e.g. clay fraction, plasticity index, effectivenormal stress, etc.).a,',in which v/ is a parameter for dilatancy, taken equal tothe mobilized friction anglein this study. Details on thecalibration of the Cam-Clay model parameters can befound on the ¥vork of Modaressi (1995).As an example, Fig. 5 illustrates curves of shear stressand normal displacement versus tangential displacementfor an overconsolidated clay subjected to monotonicshear loading, as computed with the proposed BoucWen-Cam-Clay model. Notice, that vhen the shear bandEquations fo/' Heat Generated Pore Presstt/'eStarting from the principles of mass and energy conservation in a tlvo-phase soil element, Vardoulakis (2000)re-formulated a set of t¥vo coupled equations that governthe mechanisrn of heat generated excess pore-waterpressure. In the limiting case of undrained shearresponse, the equation of pore water pressure generationis:i GEROLYMOS ET AL.16Poisson's ratio v and of C* on temperature, ¥ve (tentative-81ly, at least) assume that they are both independent ofo;oOC ci ytemperature.( ccANotice in Eq. (18) that the coefficient ), is either nuH orpositive, dependin*' on ¥vhether the temper'ature surpassesa critical value e**, and whether the clayey soil is behavingDS:*ah: y OC el3y;: -o 5NC c!ay ..... Ethermoelastically or is collapsing in a thermoplastic_1manner. We also note that Eq. (17) is not valid as soon asvapor'iz,ation takes place. This happens ¥vhen the temperature surpasses the critical value for vaporization, ¥vhichis approximated by the solution of the follo¥vin_g: equation(Vardoulakis, 2002):1*1 sO 40 5O 10e 120O20TemQerEture e 'CFig. 6. Idealized ;sotropic thermal volumetric deformation of anormalh. consolidated (NO, a slightly overconsoiidated and aheavih_ overconsolidated (OC) cla¥.': The following branches aredeutified: OC Clal.': ( ) Heating phase: A-B, thermoelasticex pansion: B-C, thermop]astic contractton anti (ii) cooling phase:C-D, thermoelastic contraction: NC clay: (i) Heating phase: A-F,,tt]ermoplastic contraction and (ii) cooling phase: E-F, thermoelastic contractionlc p = ).**d edt cJt(1 7)in ¥vhich ),* is the pore-pressure-temperature coefficient(in units of stress per temperature) given by the followingtwo-branched expression:},OeJ ,;Lm:::; Cecr(18)e_rvep+ v +Ceec*(7,,o (62e+16926) exp ) - 4650(20)Oe + 273In the limitin*' case of adiabatic loading conditions thetemperature profile inside the shear band is considered tobe uniform and only variation ¥vith time is assumed. Inthis case the governing equation of heat generation is:deDdt 1j(pC)(21)¥vhere j ( = 4.'_ .J/cal) is the mechanical equivalent of heat,and (pC) represents the specific heat multiplied by themass density of the soil-¥vater mixture. Picard (1994)proposed thatj( pC)m = 2.85 MPal'C,Eq. (19) below. In this limit the shear band boundariesfor ¥vater-saturated clays. D expr'esses the r'ate of mechanicai vork due to frictional heatin : of the soil inside theshear band. By neglectin*' all dissipation in the fluid, Dcoincides with the rate of ¥vor'k of the shear stress deform-are pressure-shock surfaces and it is meaningful toing the soil skeleton:¥vhere ( :: and (x. P are illustrated in Fi_9:. 6 and c is given inassume that the excess pore-¥vater pressure p is uniformlyD = r,, cdistributed along: the thickness of the shear band. In(22)other ¥vords p is only a function of time.As illustrated in Fig. 6, the thermal volumetric strain ina drained heating test under constant isotropic stress,may be expressed as a bilinear function of temperature.Since preconsolidation stress is also a function of temperature, the bilinear behavior is only an approximation. c :is the slope of the volumetric thermal strain-temperature(g) curve, associated ¥vith thermoelastic expansion ino¥'erconsolidated clay and with thermoelastic contractionin normally to slightly overconsolidated clay. Similarly,(x:P is associated with thermoplastic contraction in bothin whichis the rate of shear strain measured after theshear band formation. The shear strain y is expr'essed as afunction of lateral displacement u and shear band thickness dboverconsolidated and normally consolidated clay.The parameter c in Eq. (18) is the oedometric compres-active only after the development of shear band.sibility of the ¥¥'ater-saturated drained soil, approximated(after some algebra) by:y = <z! - u*> (23)c!b¥vhere u*+ is the lateral displacement at critical state(corresponding to zero rate of volumetric strain). Thesymbol < ･ > in Eq. (23) are the Macaulay brackets:<x> = x, if x : O; <x> = O, ot/1e/'Tvise. Therefore, Eq. (21) isEVOl,IJTION OF SHEARING RF.SISTANCF.DURING SLIDING1c (1+ v)eo cf (19)3 ,,oIn i(1+ O)As elucidated in Fi**. 7, the sliding process can be divided into the follo¥vin*" three phases.¥vhere v is the Poisson's ratio of the soil skeleton under(a) Pre-shear-band bellaviou/': The behaviour of thefully drained conditions, e. is the initial ¥'oid ratio of thesoil at first shearin*' should follo¥v the path A-B-C insoil, and C* is the re-compression index in a reloadingcycle, assumed here for simplicity to be identical to theFig. 7. The peak stren*'th is mobilized at the veryearly stage of displacement, and then drops to the"s vellin*"' index in a unloading cycle. Due to lack of anycritical state, triggering the creation of shear band.significant information on the dependence of theBeyond this point, the volumetric displacement is 17SHEAR B、へND MOD薮LP鷲 溺国τ二） C藷蕪壽弘・1磁：心 、F、B憩＼C俄ボq3i5【猷韓〔τo．）ら 語綿ε＝訟鴬of 丁c ＿』τ貿∠二1τツ，，．、、鋸鴇，．抑．．㎡壽鰍爾 r or 噛￥9譜Fρ「暫5sur奪 rさ壱Fas象噂S ／ D芝 ⑳みごりるに ロ きヒ むさヨぬ（b〉 lτヨ財“『3（1−P偏） c心∫ 欝r3コレ》n 〔c、】A置 篇D15p泊qe爬nヒ uFig、7． Idealized evolu重ion of the mobl旦ized shear b謎nd res韮s1ance duri翻9 Ihe shd童ng Process： lhe fo“owing P貰肇ases are idenI董6ed： Prε一5hεαr一加ηゴわ8hα｝・iαθ倉：ApB脚C，Mα勘・1α1∫oゾ’θノ∼〃∼g；C−D，and r1∼θ’7ηo一ρo’じo−1ηθch側’cα150ゾ’θπin8＝D・￡ I I 鐵 雛・ 鑓彦 灘 謙壽 C糖1 直論犀丁翔1高） C凋ダ Fr鵡n IC7（al銀 黛 ・ 、、 ／＼ z・ク 榎 ’N、〆づ数レ■（c）↑↑C． assumed to vanish．The so主I be致aviour in this pぬase 7㌣齢h is governed by Eqs。（1），（2），an（i（13）．（b） Mα1θ1’iα15砺∼εηing： During this phase，the evolu−Fig，8． Schem飢ic 飛usIr飢ion of mu紅i−layer perceptron neura畳 tion of she＆ring resistεしnce玉s depicted by pat｝1C−D． ne霊worksdevebpedforcorrelaIionofthemodeiparame重ersw髄量1 The material insi（ie the shear band is fl甲ictionally softening dueto s宅ra呈nandstrainrateincrease（ifthe key i聡dex soil properIies；Ail重hree neIworks consist of重葦1ree Eayers withthehyperbolictangenねs錘1etransfer“acIiv飢lon”釦臓c芝ion of their neurons material ex紅ibits Ilegative rate e狂ect）．丁銀s frictional softening is accompanied by temperature rlse．The soil behaviour ill this phase is governed by Eqs．（ユ）， （2），and（14）．（c） Thθ1●〃10一ρ01’o−117θchα11icσ15砂1θnillgl This phase，Iayers，is schematically i11ustrated in Fig．8．As shown inFig．8（a），the input Iayer comprises two illput neurons（1n凱2）representing the followi119Parameters（pattems）： corresponcl圭ng to patぬ D−E，starts as soo…1as the ●竜he clay fraction CF，and temperature lnside the sぬear band surp＆sses a 。毛he clay act量vity／1 cri重ical value、Beyond this critical po玉nt，hea重gener−The lat￡er is related to plasdcity index lp： ated pore water pressures deve至op，caus圭ng further1P＝！4CF frictional softening． Eventually a residual stead》7 state condition is I’eac員ed，because： ・excess pore 、vαter pressures c＆nnot exceed 重he lnitl＆l e仔ectlve s重ress，σ看o，and（24）丁紅e “hidden” 1＆yer of the network consists of虚reeneurons （h漏3） arld the output 圭ayer of olle lleurol1，representing the s玉ow residual friction ang玉e ψ「，、． The 。ぬeat genera重ed pore water pressures dhn圭nishhyperbolic tangent function1s used as the‘‘activatiol1” graduallyduetofriαionalsoftenlng． The mecbanisms of this phase are govemed byac短eved with repeated重rials，using the mathematical E（ls、（1），（2），（17），and（21）．Phases （a） a11（i （b） are respons呈ble for the lands豆ide重riggering，but they also inHuence its evolution．On thecontrary，phase（c）a鉦ects only the1εしndslide evolutiol1；it is the major destabilizillg factor that con重ributes toaccelerated“c罫eep”andmaytransformaslopeinstab圭1−ity to a cεし芝astrophic landslide。function of al壼neurons．T1ηiniηg of the neural network iscomputer code MATLAB．The lnpuωata base used for tbis重raining，collsists of results from ring shear tests such asthose of Tika et aL（1996），Tik＆a勲d Rutchinson（1999），Lupini et aL（1981），Skempton（1985），Bishop（197i），andMoOre（墨991）． The mathematical formulation of the neural networkafter the tra量ning，is expressedεしs：＠・・一t ［蕩 h（激｝ヅ1醐）＋わ2］（25）CAL豆BRAT豆ON OF MODEL PARAMETERS A methodology is presented for the caiibration oギ由emo（1el parameters by utlllsing experimental data from the正iteratuIle．The nlethodology is based on correlatiHg wit封where w1，，ノand わ11are the weights and biases of thehidden layer，and w2，andか2the weightsεしnd biases ofα1eoutput layer，given呈n Tab豆e I．刃ノis the nom1εdized inputkey index soil properties，by means of arti最cial neur＆Ivector wlth respect to the minimum v＆1ues of the problemnetworks．parameters崎・（xlr4，x2；CF）．喝・isexpressed＆salinearfunction ofλr／according to：Pαノη〃1θ！θ1’56ゾFヂio！ionα1S〃ηin S（ガン∈∼11ing Aso−cαlled“multilayerperceptron’ラ（MLP）networkfor func｛ion apProximation was developed to correlatethe slow residua玉friction aロ91eψ，，、with key index soi至 拘㎜mm笛 喝篇2 ． 一1 （26） max濁一mm笛properties．丁紅e reader is referl聾ed to the MATLAB userラsThe（min，max）v＆lues of parameters x／are（O．4，4）and（0，80）for14and CF，respectively．The capability of them段nual for details in neural network anα1ysis（theory andneur＆l network 茎node星to ‘‘predict” the slo、∼・residualterm呈nology）、The neural ne￡work，consisting of threefrlction angle ofthe various experiments is demonstrated GJEROLYMOS ET AL.18Table 1. ¥Veights and biases foF the slow residual friction angle ep*_sOmput layerHidden layerbl,l,' 1,J1b2t')-i075'!O,254 O,747- 2 1 O,713,407 20_94 l5'Fl ,555- O.2083. 149- 5 009 O 435 O ;S(!)OTable 2. T)picai displacements at various stages of shear in intactclays having CF>30a/o and at (T,;0<600 kPa (Skempton, 1985)Displacement: mmStageO-C_ NCPeak 0,5-3 3-6Rale of voiume chan_ e approximately zero 4-lOAt30)_OO*.+ Io1 OO- 500Siolh' residuai ep*O 02 03 0405O1G6Dispi30ement I mFig. 10. Slolv residual friction coefficient ratio (norma ized with thefriction coefficient p*, at critical void ratio) versus displacement:Comparison betlveen me8sured in ring shear apparatus and computed behaviour, for a=67: The ex perimeutai points taken fromTika and Hutchinson, 1999, correspond to Vaiont clal.' vith plasticrtl.' index I, = 22, cla¥_ fraction Cr=30, effective normal pressure (T,'*o=0.5 MPa, and criticastate frtction coefficieut p*, =0.4840d A=075* 1 2e, 351'cA=15*43; 30aIF25O A=0*0820,,,5"aOAAo A'.; Ae. 5u,Oo20 40 50Jfioi1$ogjstic8e1 OOSigmoidClay fr ction C*Fig. 9. Sto v residual friction angle versus cla .' fraction and clay activi*/r' '; ';S*: '#*t)': Comparisou bctween experimental data and the arrificiai neuralnet vork approximatton: Data points taken from Tika et al., 1996;Tika and Hutchinson, 1999; Lupin et al., 1981; Skempton, 1985;Bishop et a ., 1971 and Moore, 1991in Fi . 9.The subsequent task is to calibrate the parameter Oi ofEq. (15) that governs the transition from critical to slo¥vresidual state. Skempton (1985) proposed typical valuesof displacement at various sta*'es of shear in intact clays;they are given in Table '- and are valid for clay fractionshigher' than 300/0 and effective normal pressures (7,,o lo¥verthan 600 kPa. These values are consistent ¥vith resultsfrom rin*' shear tests on sand-mica mixtures conducted byLupini et al. (1981). Note that, the displacement requiredto reach the slo¥v residual friction coefficient was 30 mmfor soil specimens exhibitin_g: turbulent shear mode, 100mm for transitional shear mode, and 400 mm for slidin*'shear mode. Evidently, the ma*'nitude of the effectivenormal stress (T,',o and the presence of structural discontinuities also ha¥'e a si :nificant influence on the shearbehaviour of clays. The reader is referred to the lvorks ofSkempton (1985) and Luplni et al. (1981). Figure 10compares analytical [computed ¥vith Eq. (15)] versusiaboratory (ring shear test) results for the Vaiont clayt,aken from Tika and Hutchinson (1999).A neur'al network ¥vas also developed for a shear modesoil classification (Fi**. 11). In this case the net¥vork,(,, .･･* ･;= )tanhiFig. 11. Schematic illustr tion of multi-la¥.'er perceptron neuralnetworks developed for classification of cla¥_ s according to shearmode behaviour and rate effect on residual strength, in terms of theclay fracrion: The networks consist of three la .'ers vith tl]ehyperbolic tangent and logistic sigmoid as tire transfer functions ofthe hidden and output neurons, respectivel,.,consists of one input neuron representin*' the clay fraction CF, t¥vo hidden neurons, and three output neurons,each corresponding to one of: turbulent mode (TU),transitional mode (TR), and sliding shear mode (S);"tar*'et" values are I for the correct class and O otherwise. The prediction of the neural net¥vork after training,is plotted in Fig. 12. Values bet¥veen O and I represent theuncertainty of the network prediction. Accordin*' to theresults, the possibility of a clayey soil to exhibit tur'bulentshear mode is high for CF<,200/0, Io¥v for 200/0 <CF<400/0, and z,ero for CF>400/0. In the same way, the possibility for transitional shear mode is lo¥v for CF<20010, SHEAR BAND19ivIODELlis,) 15' > ;"I '5 08"' :'1'"'F5 04e; 05oo20 40OCl y fr ction C=O80 100Fig. 12. Shear mode potential versus cla, fraction, computed withartific al neurai network anal Isisooeoe= l r)o aeu)ooaorlO naoiveo oOo8o20 40 8080100C[ y fr ctien CFI 9Fig. 13. Correlation of fast residual friction coefficient ratio (normalizedvith the slolv residual friction coefficient /i*.*) with clay frac-tion: Comparison between experimental tlata and artifieial neuralnetwork approximation: Data points taken from Tika et al., 1996high for '_Oo/0<C'F<400/0, and zero for CF>400/0.and Tika and Hutchinson, 1999Finally, the possibility for sliding shear mode is zero forCp < 400/0, and high f'or CF>400/0 .2As mentioned in the introduction, the slo¥v residualstrength depends also on pore ¥vater chemistr'y and- ieffective normal pressure. Unfortunately, theseparameters have not been incorporated into the proposedrnethodology, due to insufficient information provided byscarce experimental data.Several researcher's have sho¥vn that the critical statefriction angle ep*+ correlates with the plasticity index evenif with substantial scatter. One such relationship (¥vithlarge correlation error) has been proposed by Mitchell( 1 976) :,.* arcsin0.6 - O. 14 Iog (Ip- 5) J (27)In pre-existin*' shear surfaces ¥vith large clay fractionEq. (27) overestimates *.. Therefore, Eq. (27) is validonly for intact clays. A value of * close to the slo¥v*,= is more realistic when reactivation of an old landslide is anticipated.O:l 15 05OoO 08O 04o 12Ve[ocity : m / sFig. 14. Fast residual friction coefncieni ratio (normalized with thefriction coefficient p*, at critica! void ratio) versus vetocitl_ .Comparison bet,veen measurcd in ring shear apparatLis andcomputcd behaviour, for P=310, 20, and 452. corresponding tonegatl e neutral, and positive rate effect, espectively. Theex perimental points are from Tika and Hutchinson, 1999residual friction anglePa/'ameters oj' F/'ictiona! Strain-Rate BehaviourMultilayer perceptron neural net¥vorks were de¥'elopedfor the calibration of the viscous parameters of the model/1,,d, (Fi**. 8(b)) and(Fig. 8(c)). The latter, fi, controlsthe sharpness of the transition from slow residual to fastresidual state. The fast residual friction coefficient ratiord=pl,,d///,.* is correlated solely with clay fraction CF,¥vhereas fi is computed as a function of the effectivenormal pressure a,{o, clay activity A , and clay fraction CF.The computed parameter /1*,d is compared in Fig. 13, ¥vithexperimental data of Tika et al. (1996) and Tika andHutchinson (1999). Figure 14 demonstrates the agree-80) for a',;o, A and CF, respectively.In addition, a neural net¥vork was developed for soilclassification according to the rate effect on residualstrength. The output layer of the net¥vork consists ofthree output neurons, one corresponding to each class(neutral, negative, and positive rate effect), and targetvalues of I for the correct class and O, otherwise. Theprediction of the neural net vork after the training, isplotted in Fig. 15. According to the results, the possibilityfor neutral rate effect is high for CF< 100/0, Iow for 100/0< CF<200/0, and zer'o for CF> 200/0. The possibility forne*"ative rate effect is zero for CF<80/0, high for 80/0< Cp<400/0, and lo¥v to medium for Cp>400/0. Finally,the possibility for positive rate effect is zero for Cp < 400/0,ment bet¥veen measured (ring shear apparatus) andand medium to high for CF>400/0.computed [Eq. (16)] fast residual friction coefficient ratiofor' a wide velocity range. C'.alibration of fi ¥vas based onPol'e-Pressure- Tempe/'atu/'e Coefficien tthe neural net¥vork analysis. The expressions derivedLittle information is available for the pore-pressure-after training of the neural network are of the same formas Eqs. (25) and (26). The " veights" and "brases" of thenetwork layers are given in Tables 3 and 4, for the fastresidual friction coefficient ratio rd, and the parametertemperature coefficient, ). . Experimental data takenfrom Sultan (1997), Sulem et al. (2004), Baldi et al.ft, respectively. The (min, max) values of the input(1 991), Plum and Esr'ig (1967), and Laloui and Cekerevak('_003), identify the parameter ).* as str'ongly dependenton overconsolidation stress ratio OCR. Typical values ofpararneters xj are (O. 177 MPa, 0.98 MPa), (0.4, 4) and (O,(x:P (see Eq. (18)) for a norrrrally consolidated clay I .343GEROLYlvIOS ET AL.20Table 3. ¥Veights and biases for the fast residual friction coefiicient ra-overconsolidated clays are in the range of O.5 x 10-4 .C_- ltio rto I .5 x 10-4 .C-i. As sho¥vn in Fig. 6, the elastic thermal=/lr.d /p*..Hidden laverblIt' l,. J- I- 182,149¥vater pressure p. Ho¥vever, due to insufficient information pro¥'ided by scarce experimental data, it is considered as a constant in all the subsequent analysis.l 214526is a function of the overconsolidation stressratio OCR, ¥vhich in turn depends on the excess por'e-b2tiT)_ll . 0445- 1 97 87)_coefficient ceOutput layerO.418Critica! Tel7rpel'atureCritical temperature, e*,, is the threshold for ther-Table 4. ¥ reights and biases for parameterftHidden layerOutpll iayerIt'2i b2bl,l 1' ll,J- 7.408- S.556- 15 298-2)__158= 9. '_4 I6,601lO.8967.84868.73256^857O,31650 415-6 615= I .796moplastic "co!!apse" of an overconsolidated clay.Exploiting experimental data from Sultan (1997),Vardoulakis (2002) proposed the following expression forecr as a function of OCR:O '_02- 9 57 l?_6_444- 2 1 .4927 434l02 301[ OCR - 1420.6398.013ec*400 + 600 [ I - exp 10255 . 895¥vith- I .286OCR (T'fo (29)a,,o2PCon7p/'essibi!ity Incle_1'There is lack of information of any dependence ofthe recompression-s¥velling index, C*, on tempera-e, 08ture-hence our assumption is that C* is independent of04e. Based on the modified Cam clay. model, Wroth andcWood (1978) sho¥ved that C* can be obtained as a funceOtion of the plasticity index:20 40 eO80 100C! y r c ien CFC,= 37Po (30)IFig. 15. Rate effect potential versus cla .' fraction, computed lvitl]artificial neilral network anai .,sisSllea/' Band Thickl7essm*' functlon of OCR Results from drained thermalThe shear band thickness, db, is a critical modelin*'parameter, as it makes the strain-dependent Eqs. (17) and(21) of heat generated pore pr'essures compatible with thedisplacement-dependent Eqs. (2), (13), (15), and (16) ofthe viscoplastic frictional behaviour.loadin*" of illite (Plum and Esri_9:, 1967) and of Boom clayspecimens at constant isotropic stress (Baldi et al., 1991)indicate that the thermal volumetric strain vanishes ¥vithmicroscopic structure of shear bands in Kaolin specimensin direct shear tests, and also proposed that the shear-increasing OCR, reaching zero at OCR=2. Vardoulakisband thickness can be estimated as a function of the('_OO'_) proposed an empirical correlation bet¥veen theparticie size dso, according to;(OCR= 1) are in the range of 1.5x lO4 .C i to 2.5><1 O4 .CI . For slightly overconsolidated clays(1 < OCR< 3) the coefficient a:P appears to be a decreas-Mor*'enstern and Tschalenko (1967) documented thecoefficient oe P and OCR for o¥'erconsolidated clays, utilis-c!b * '_OOd50 (3 1 )ing experimental data from Sultan (1997)::plO3; exp- (OCR12- 1)aiAs a matter of fact, Eq. (3 l) is considered to give a lo¥ver[oCll'bound estimate of db. Results from back analysis of thewell-documented Vaiont landslide, indicated that valuesof db in the range of 0.1 m to 0.2 m are quite reasonable¥vithOCR = (Tnoano(28)P(Vardoulakis, 2000). Such high values are justified if veassume that the active shear band thickness increases inthe course of slidin :Notice in Eq. (28) that (x:P is not a constant but a functionof the excess pore-water pressure p.The elastic thermal coefficient ais estimated to beabout 5 to 10 times smaller than the elastoplasticNUMERICAL FORMULATION OF THF, SHF.ARBAND MODF.Lcoefficient ai:P in normally consolidated and slightlyThe system of differential Eqs. (1), (?_), (13), (17) andoverconsolidated clays. Hence, typical values for' (x: of(21) describes mathematically the deformation of the SHEAR BAND lvIODEL'Table 5. List of materials and model parameters used in the anall05sisof shear band d .'namic deformation(a)oCase srudyParametersClay mineralA I A2Shear modeTRSRabe effectNEGPOSCF (0, )3070A0.4O_4c*, (deg)2S24c* , (deg),-5136* d (deg)16i7C,O.032O 075cKaoliniie(ommoriilonite Montmorillonite ' HliteTRiNEG =SPOS02, TRMontmori loniteiNEG= , 304i 8 41 0.95 267030zo16 50.32 i O.073eeO.22l, (O.2, O 5, 2, 5)o a5 i152, 5322s3urn(b)08O. 75a;,o (h,IPa)OCR04B2BlKaollnite Kaolinite21nte. Kaoiinitoel*5Montrno l:onitee4O."_)eo ('C)e*.p ('C)a ('Cu*l)(m)db (m)1002ISo, (1,_4, 154, 210, 256)7.4 Io ,<o oo_ooi5, (O.Ol, 0.05, O 1)ko.ol;.4aoOo100O osiSu mKao niie80e,nib0.5u. (m)O.OOl6040Only for case C*Montmorll on teH(c)20:: eefshear band. An explicit finite-difi rence algorithrn hasbeen developed for the solution of this system. TheG1algorithm ¥vas incorporated into a computer code, Dsc-LANDSLIDE (developed under the frarnelvork of theresearch pr'oject LESSLoss, 2005), for the analysis ofearthquake triggering and evoiution of catastrophiclandslides.a 05115,253253Um(d)08K ol niteo; oe( 04MontmoriiioniteSHEAR BAND DYNAMIC DEFORMATION:ANALYSIS AND DISCUSSIONThe developed model is utilised to study the dynamico* 02O/ _lo 051ISdu: mdeformation of a shear band in clay-rich material subject-ed to a constant velocity of v=0.1 m/s. As alreadymentioned in the introduction, at such high velocity thefast residual strength ¥vill be fully mobilized. Four casesare considered of varying clay mineral and clay fractioninside the shear band:･ kaolinite ¥vith Cp= 300/0 and CF= 700/0,' montmorillonite with CF= 300/0 and CF= 700/0.The model and material parameters used in each case aresumrnarised in Table 5. Their calibration was based onthe aforementioned neural net¥vork methodology. It isstated however, that there are no available experimentaldata t.o support the validity of the analysis.The computed evolution ¥vith the progress of slidingdisplacement of: (a) the normalized shear stress ratio, (b)the apparent friction coefficient ratio, (c) the temperatureand critical temperature, and (d) the excess pore-waterpressure ratio are plotted in Figs. 16-17. The followingobservations are ¥vorthy of notice in these fi**ures:Fig. 16. Evolution ,vith displacement of: (a) the normalized s learstress ratio tl,r,10, (b) the apparent friction coefficient ratio plp,,,(c) the temperature e (black line) and the criticai temperature g**(gra .' Iine) and (d) the developing excess pore pressure ratio i'( = pl(I o), for cases A1 (Kaolinite with Cr=300/0) and B1 (Montmorillonite with CF=30010): Both soils exhibit transitional shear mode(TR) and ncgative rate effect (NEG)(a) In all cases, montmorillonite exhibited the slo¥verreduction in shear resistance. Although the peakstrength of montmorillonite is about 1.5 timessmaller than that of kaolinite, its mobilized shearresistance after 3 m of sliding is approximately t¥votimes larger than that of kaolinite when negativerate effect is involved and thr'ee times larger whenpositive rate effect is considered. The "ductile"shear behaviour of montrnorillonite, or the (more)"brittle" behaviour of kaolinite, is attributed to thefollo vin*' reasons: CJEROLYlvIOS ET AL.22051oO.e; 0.5(a)- 0404Kaoi niteS 030202*Montmori[ oniteC O1e,EZ:< OoO151103G2040sou mi08Fig. 18. Evolution of apparent friction coefficient ratio plp*. Ivith(b)displacement for values of initial effective normat pressure a 0=0.2, 0.5, 1, 2 and 5 MPa (Case C: I]lite lvith C_F=309/0)06Montrnorillonitev 04a further de-acceleration of the shear strength?: 02(b) The displacement u** at ¥vhich thermo-poro-mechan-softening.< O1 Oo15 25 3O 0580the landslide evolution, displacement is computed to(c) The infiuence of rate effect (positive or' negative) onthe evolution of shear resistance dur'ing the thermoporo-mechanical softening phase, is negligible in the6040case of kaolinite, but appreciable for montmoril-Montmorl on't's20(c)e = oc'05115u m1(d)and the shear band thickness d!' on the evolution of acatastrophic iandslide. The case considered is that of ashear band rich in illite with clay fraction CF=300/0,Kaolinite06, 04CL 02Montmori lon'teo oslonite.Parametric analysis ¥vere also carried out to investigatethe influence of the initial effective normal pressure a,;ooOthe rate effect on residual strength This critical, forbe appr'oximately 0.5 m in kaolinite and 1.4m inmontmorillonite.Kaolinite08ical softening is initiated, is practically unaffected by15 2 25 3ummoving at a constant velocity of z; = O. I m/s. The modeland material parameters used in the analysis (case C) arepresented in Table 5.Figure 18 illustrates the evolution of the apparent friction coefficient ratio ¥vith slidin*', at four levels of initialeffective pressure (T,,o (=0.2MPa, O.5 MPa, I MPa, 2MPa, and 5 MPa). It appears that the displacementFi**. 17. E,volution lvith displacement of: (a) the normalized shearrequired for temperature "explosion" decreases ¥vithincreasing (7,'*o In other words, the shear behaviourstress ratio r/(T e, (b) apparent friction coefi cient ratio ///p*., (c)becomes more brittle at higher values of (T,{o, increasingthe temperature O (black line) and tl]e critical temperature g*. (gra .'line) and (d) the developiDg ex cess pore pressure ratio r* ( =pl,f o),the potential of a catastrophic landslide. It is alsofor cases A2 (Kaolinite with CF=700/0) and B2 (Montmorillonitevith CF=70010): Both so ls ex'!]ibit sliding shear mode (S) andposit ve rate effect (POS)mentioned that the evaporation limit e*,p was not reachedin any of the cases. Figure 19 elucidates the displacementrequired for thermal "explosion" as a function of theshear band thickness clb, for selected values of initialeffective normal pressure cr,',o. It is demonstrated that at･ The small residual strength of montmorillonite,lo¥v levels of (T,'*o ( = 0.2 MPa), the mechanism of thermo-mobilized at the very early stage of sliding, resultsporo-mechanical softening ¥vould only be activated if dbin a si**nificant reduction of frictional heating¥vhich in turn slows down the excess pore-wateris of the order of felv millimeters. At greater values of (7,',opressure generation, and thus the shear stren*･threduction.heat generated pore pressures may rise even for the･ The larger compressibility of montmorillonite,the index of lvhich (C*) is an order of magnitudelarger than that of kaolinite, results in a smallerpore-pressure-temperature coefficient, Ieadin･ to(in excess of 2 lvlPa), ho¥vever, thermal "explosion" andextreme case of db= O. I m. It is noted, that Vardoulakis(2002) estimated an average value of a,{0='-.38 lvlPa asrepresentative for the Vaiont landsllde.The capability of the model is further demonstratedthrough analysis of the shear band response under cyclic 23SHEAR BAND ¥. ,10DELO105o 080 S* 006O1:, 004S, -Oi25{!)o )25- * = e 2 JPo-o sO 5 25 30 3S10Dlspl-O.s2015eement required fer t$mrature "exp:osior,' I･O 25 O O 25DisplacemEnt u :o.sTllFig. 19. Curves of shear band thickness db versus displacementrequired for temperature "explosion" (initrat on of pore waterFig. 21. Example of the effects of oscillaton. ioading: shear stress ratioversus disp acement h)'steresis toops (Casc C: Illite with C F= 300, ,dh= 0.0015 m, a,;o = I MPa)pressure rise) for vaiues of ini ial effective normal pressure c,;0=0.2, l, 2, and 5 MPa (Case C: llite with CF=300/0)1Oeo04oS- a204(a) OF:s oi2c-o 2c3oO 4*o 5-O 2S O O 250.5Dlsp!aoementu m-a 5o1234Fig. 22. Example of the effects of oscillatory loading: evolution of thefriction coefficient ratio with displacement (Case C Illite with CF =t seciO30 ./., db=0.0015 m, a,'rt = I IMPa)s10 1Eo1 O 03)> _5e) Io.ese.04-1 OO1234s1 o. 02t I s80Fig. 20. Example of the effects of osciilator) Ioading: imposeddisplacement and vehociry time histories (Case C: Illite with Cr=10-O 5-0,2S O 0.2505Dis lacement u : m300/0, db = 0.0015 m, e ,,o = I MPa)10ading. The shear band is subjected to a displacementtime history of incr'easing amplitude ¥vith time. TheFig. 23. Ex'ampie of the efrects of oscillator, IoadiFrg: evolution oftemperature with tlisplacement (Case C: Illite with C '=300!/., db =0.0015 m, (T o = I MPa)imposed displacerrrent and resulted velocity time histor'iesare portrayed in Fig. 20. The material and modelparameters used in the analysis are those of case C(Table 5). Unfortunately, according to the authors'knowledge there are no relevant experimental results inthe literature to compare ¥vith the prediction of theorientation has occurred, the shear resistance becomesinsensitive to loading history (Lupini et al., 1981).Fi**ure 23 sho¥vs that the temperature rise is practicallynegligible, meaning that heat generated pore pressures inthis case of cyclic loading do not develop even atmodel.velocities as large as 8 m/s. Such a value for velocity is farFigure 21 portrays the shear stress r'atio-displacementhysteretic loops. It is observed that the shear strength isprogressively de_ :rading lvith cyclic loading reaching anultimate level, which is the f'ast residual strength. Thecorresponding evolution of the friction coefficient ratio isdepicted in Fig. 22. Notice that, the shear strength is notrecover'ing at any time during loading, in agreement ¥vithlaboratory results sho¥ving that once preferred particlelar*'er than those developed in a stron*' seismic motion(which only rarely reach 1.5 m/s), revealing indirectlythat thermo-poro-mechanical softening is associated onlywith the high speeds developing in the course of sliding,driven by gravity for'ces; even if the triggerin_ : of suchsliding was provided by the seismic shaking-aphenomenon reminiscent of liquefaction-induced flo v ofslopes: the seismic shaking strains the material and high GEROLYiviOS ET AL24excess pore-water pressures develop leading to iiquefaction. But only if the residual strength of the liquefied soilis overwhelmed by the gravity-induced shear stresses ¥vill"flo¥v" and large deformation take place.CONCl,USIONbehaviour of Boom cla¥.' and clay-based buffer materials. Repor'!EUR J3365, Cornmission of he EuYopean Communities, NuclearScience and Technotogy.3) Bishop. A^ ¥V , Green. C. E^, Garga. V. K,, Andresen, A andBro¥vn, J. D. (1971): A nelv ring shear apparatus and ils applicationA constituti¥'e model for rapid deformation of a clayrich shear z,one has been developed utilizing the conceptof frictional softening due to heat generated excess pore¥"ater pressures. The model is incorpor'ated into a novelalgorithm named DSC-Landslide for the analysis ofearthquake-induced catastrophic landslides. A methodology is developed, based on muiti-layered artificial neuralnetworks, for' the calibration of the model parametersagainst published laboratory results. A sensitivity analysis is conducted for the influence of key model parameters(initial effective normal stress and shear band thickness)on the pore-¥vater pressure rise due to increase in temper-ature. The capability of the model is demonstrated in anumerical study leading to some interesting conjectures(1vhich, ho¥vever, are for the moment ¥vlthout experimental ¥'erification):(a) Clay activity has a decisive role in the evolution ofthe landslide: Iarger activity (e.g. montmorillonite) Ieads to less rapid slide.to the measurement of residual stren_ :th, Geotechnique, 21(4),273-328.4) Bouc. R^ (1971): Modele ma hernatique d' hysteresis, Acustica, 21,l 6-2 5 .5) Bromhead, E. N. and Curtis. R. Dalternative methods of measurin(1983): A comparison ofhe residual stFength of LondonC_Ia_v. Crotnld En*"ineering, 16, 39-416) Campanella, R. G. and lvlichell, J. K. (1968): Influence ofempera-ure variations on soil beha¥'ior, J. Soi! IV[ec/1. Fo!nlc!., ASC_E, 94,709734.7) Chang, K. J., Taboada, A^, Lin, ,J L. and C_hen. R. F. (2005):Analysis of landsliding by earthquake shaking using a block-on-slope thermo-mechanical model: Example of Jiuf ngershanlandslide, central Tai¥van, Engineering Geo!ogy, 80, 151-163.8) Despax, D. (1976): Influenc,e de la temperature sur les proprietes desargiles saturees. Docrora! Thesis, Ecole C_entrale de Paris9) Drescher, A.. Vardoulakis, I. and Han. C__ (1990): A biaxiaiapparatus for testing soils* Geo!ecll. Tes!. J_. GTJOD; 13,226-234.lO) Fodi . A , Alotllou, ¥¥r. and Hicher, P y. (1997): Viscoplasticbehaviour of soft clay. Geotecllnique, 47(3), 581591 .l l) Gero ymos. N, and Gazetas, G. (2005): C_oustitutive model for 1-Dcyalic soil beha¥*iour applied to seismic analysis of layered deposits,(b) The influence of the rate effect on residualstrength (positive or negative) on the landslideevolution increases ¥vith increasin_sodium montmoriHonite, Geoteclliliq,!e, 48(6), 787800.2) Baldi> T , Hueckel, A., Peana and Pellegrini, R. (1991):Developments in modeling of thermo-hydro-geomechanicalclay. activity.(c) The initial effective normal stress (7,',o and shearband thickness c/b greatly affect the evolution ofthe landslide, ¥vith greater values of (T,fo andsmaller ¥'alues of db, respectively, resulting inmor'e brittle and accelerated slides^(d) Thermo-poro-mechanical softening is associatedonly ¥vith sliding driven by gravity forces and not¥vlth earthquake-induced loading.Application of the proposed model to real case studies(e.g. the Jiufen*'ershan, 1999 Iandslide triggered by theC_hi-Chi Tai¥van earthquake (Chang et al., ?_005)) wouldstrengthen the validity of the aforementioned conclusions.Soil.s anc! Foundations, 45(3).17_) Habid. P. (1967): Sur un mode de glissemen des massifs rocheux,C_ R. Hebc! Seanc, Academy of Sc.ience. Paris, 264, 151-15313) Habid, P_ (1976): Production of gaseous pore pressu e during rockslides, Rock l lecllanics, ?, 193-197.14) Hicher, P. Y. (1974): Etude des proprietes mecaniques des argiles al' aide d' essays triaxiaux, influence de la vitesse et de ia emperaure, Report Soi! M:ecJ1. Labo., Ecole C_entral, de Paris.15) Hueckel, T and Baldi, CJ. (1990): Thermo-plasiici y of saturatedsoils and shales: constitutive equatious, .J. Georech. En*"rg., 116,17651777.16) Hueckel. T.. Pellegrini. R. and Del Olmo, C (1998): A cons itutivestudy of thermo-elas o-plasticity of deep carbonatic clays, In!. J__,¥r2i,,1. Ana!. " feth Geomech., 22, 549-574.17) Laloui, L. and Modaressi. H. (2002): ,Iodelling of the thermohyd,o-plastic behaviour of clays, H.1'c!romechanica! (vlc! Thennohydronlecllanica/ Bellaviour of Deeo A, i!laceou.s Rock, (eds b .,Hoteit et al.). S¥vets & Zeitlinger, Lisse, 161-17318) Laioui, L_ and Cekerevac, C. (2003): Thermo-plastici y of clays:An iso ropic yield mechanism, Compu! Geotech , 30, 649-660_19) LESSLOSS Integrated R&D Project of the EC_ (2005): RiskACKNOWLF,DC.MENTSThis paper' is a par'tial result of the Projectllvlitiga ion of Ear hquakes and Lands ides. EU sixth FramelvorkProgram, Comract number: GOC_E-CT-)_003-505448, http: //¥1'¥¥'¥ '.lessloss.or_ *.PYTHACJORAS I/EPEAEK 11 (Operational Pro-20) Lupini, J. F., Skinner, A. E. and Vaughan, P,, R. (1981): The_2:ramme for Educational and Vocational Trainin*' II)[Title of the individual program: lvlathematical andexperimental modeling of the generation, evolution and181213,2 ) ¥. {ATL,AB (2000): The Language of Technicai Computing,termination mechanisms of catastrophic landslidesj. ThisProject is co-funded by the European Social Fund (7507lvo)of the European Union and by. National Resources (25070)of the Greek Ministry of Education.RF.FF,RF,NCF,Si) Anson, R ¥V. ¥¥; and Halvkins, A^ B (1998): The effect of calcivrnions in pore ¥va er on the residual shear strength of kaolinite a lddrained residual strength of cohesive soils, Geotecllnique, 31(2),Copyright 1984-2000 The h,1ath¥Vorks, Inc.2,_) i¥,lench, V. (1966): ,Iechanics of landslides vi h nonciFcular slipsurfaces ¥vith special reference to the ¥raiont slide. Geotechnique,16, 330337_3) Mitchel , ,1. K. (1976): Fu,Idalne,1!a!s ofSoi! Bellaviour, John ¥Vile .'and Sons. Nelv York, 4'_224) iModaressi, H.. Faccioli, E., Aubr.¥', D. and Nore , C (1995):Numerical modelling approaches for the analysis of earthquaketriggered landslides, Pr'ocGeorecJ13rd hl!. Co,ifEarthquake Engrg. Soi! DRece,1! Ac!v(7,1ces in,nclnl., St. Louis. ¥i ,Iissouri, Il(IiNVLE.03), 833-843?_5) N,10daressl, H. and Laloui, L. (1997): A thermo-viscoplastic FS懸EAR BANDλ｛ODEL constim｛lve model for clays，1nf、ノ、N‘’〃1．〆4’∼α1、A／αh．Gθo’ηεc1∼、， 21，313−335．26）Moore，R、（1991）：Tぬe cねemical a鷺d斑ineralogical con【rols upon the res1dual strength of pure a蹟d naエura量 days， 0θo∼（∼（〕hη’（1μθ，25 Pressurization，So’Z∫α’1ゴ」Foμn4α’io∼15，45（2），97−108．35） Sultan，N，（1997）＝Etude d目coπ1r）ortementエhermo−mechan玉que de rargile de Boom：exper1ences et modeiisatlon，7ノ∼θ5θ4θOoαorα∫， ENPC，CERMεS，Paris． 4玉（1），35−47、36）T1ka，T．E．，Vaugねan，P．R．andLemos，L、J，（1996）：Fastshear三ng27）Muller，L、（1964）：TherocksHdeinこheVaiontValley，Rocん ofpre−exis【ingsむearzoneslnso員，Gθo’θc11’∼罐e，46（2），197−233， ！、4θご1∼σ耽5五n9〃1θθ”〃∼gGθ0109v，2，王48−212、37）Tika，笛む．E、and Hutchinson，L N。（1999）：Ringsheartes器onsoil28）Muller，L．（1968）：Newconsideraτionson嶽eVaion［slide，Rocん from l騒e Vaio真da息dsiide slip surface，Gθo’θぐノ∼’∼’gど’θ，49（1），59−74． A／θぐhα’∼ic5En9’nεθ1カ∼gGθ0109！y，6，1−9王．38）Vardoulakis，L（2000）：Catasエrop緬clandsiidesduetofrlctional29）Nova，R．（1986）＝Soil models as a basis for modeling由e behaviour heating of tbe fla員ure plane， 1、／ec1∼α’がc5 0ゾ噂Co1∼θ5’v（∼一∫丁’一’c”oπ01 of geop難ysical mater玉als，〆王ασλ∫εchαπiご01，64，31一一44．30）Otsuki，K、（1978）：On由erdaζionslllpbeこwee頂hewidthofl由e shearzoneand由edisplacementalongthefεuk，ノ．0θ0109．Soご． Mα∼θノ』1α15P，5，443−467．39）Vardoulakis，L（2002）：Dynamic由ermo−r）oro−mechanicalanab「sis ofcaこas【ro画dandshdes，Gθαθch吻正’θ，52（3），玉57−171 功ノ∼．，84，661−669．40） Vardo狙lakis， 1． （2002）： Steady shear and therma呈 run−a、vay in31）Plcard，」．（1994）：Ecroisageζhermique des arg員es sa撫r6es：apPlica一 clayey gouges，1’π、1．So1’4∫αnゴ∫’尺’cμ”て∼5，39，3831−3844． ξionaustockagedesd6cねetsradlQactifs，711ゑ5ゴ800α01『α’，1’Ecole41）Voi蜘，B．andFaust，C．（玉982）：Frictionalheaエandstreng由lossin 層ationaie des Ponds et Cha琶ss6es，Paris、 some rapid Iands1五desヲGεo’θchlz’（1μθ，32（1），43−54．32）Plum，R．L．andEsrig，M、L（1967）：Sometemperaturee窪ectson42）Wa［erson，」、（1986）：罫auk dimenslo！1s，dlsplacemem and grow由， soilcompressibiliζyalldporewaterpressure，H’9加の身Rθ5、80αヂ4 Pα9θoρ1義蝉c5，三24，365−373． （Sp、Rpζ），三〇3，231−242．43）Wen，Y．一K、（1976）IMe由odforraほdomv1bra［iono佳ysτeret1c33）Skempξon，A、W．（1985）：Residuals［reng漁ofclays in landslides， systems，／、勲gfg、ル∫θc11．，！1SC宏，102，249−263、 folded strata and tねe laboratoryンGθo’θc1∼1∼i（1ε’ε，35（1），3−18．44） V▽roこh，C．P．and V》ood，D．N・1、（1978）＝丁むe correla【ion of index34）Sulem，」、，Vardoulakls，1 ，，Ou籏oukh，H．and Perdik飢sls，V． proper［ieswiτhsomebasicenglneerlngPropertiesofso11s，Co17． （2004）：Thermo−Poro覗ec姓anicalprope痴esofthealglonfault clayeygouge・apPlica仁ion［o由eaaalysisofsねea出eatlngand員uid Gθo’（∼ぐh、／、，15（2），137−145． | ||||
| ログイン | |||||
| タイトル | stress-Dilation of Undisturbed Sand Samples in Drained and Undrained Triaxial Shear | ||||
| 著者 | s. Frydman・M. Talesnick・H. Nawatha・K. Schwartz | ||||
| 出版 | soils and Foundations | ||||
| ページ | 27〜32 | 発行 | 2007/02/15 | 文書ID | 20977 |
| 内容 | 表示 SOILS AND FOUNDA'TIONSVOI. 47,No2732, Feb. 2007lJapanese Geotechnical SocietySTRESS-DILATION OF UNDISTURBED SAND SAMPLES IN DRAlNEDAND UNDRAINED TRIAXIAL SHEARSAh( FRYDhiANi), ivIARK TALESNICKii), HANA NA¥¥*ATHAiii) and KEREN ScH¥¥*ARTZiii)ABSTRACTStress-dilation behavior of undisturbed sand samples tested in both drained and undrained triaxial shear has beenstudied. The stress-dilation relation is recognized as being a basic component of the stress-strain behavior of granularmaterials. The dilation angle, y/ commonly used to represent the dilation characteristics of the soil, is defined clearlyfor plane strain conditions. Ho¥vever, the paper discusses confusion regarding its definition under triaxial loadingconditions, and adopts the definition sin v/= -d8 /dy lax' Drained triaxial tests performed on specimens obtainedfrom undisturbed block samples of sand indicated that the undisturbed material exhibits a ¥vell defined stress-dilationrelation. By referring to plastic (irrecoverable) components of strain, it ¥vas found that this relation ¥vas alsocompatible to results of tests in undrained triaxial shear. Demonstration of this compatibility required that the smallmembrane penetration eff cts in the undrained triaxial shear tests, resulting from changing effective confining stress, betaken into account. From the results of the present investigation, and of other studies reported in the literature, it wasfound that the relation bet¥veen friction angle, c' and dilation angle, V/, under axi-symmetric conditions, as definedabove, can be reasonably expressed by the empirical expression: c' * O.4V/ c**Key words: dilatancy, drained shear, sand, tr'iaxial comp 'ession tests, undrained shear (IGC:D5/D6)principal cornpressive strain, and he developed his stressdilatancy relationship:INTRODUCTIONResearch on stress-strain behavior of _ :ranular materi-(?f l(7 = tan2 (45 ' - cr/2)(1 - de /del )als is, conventionally, based on laboratory testing of(1)lvhere cf is a function of the density of the sand, and liesreconstituted samples. The present paper presents resultsof part of an investigation of the constitutive propertiesof Israeli sands, ¥vhich included triaxial tests on bothundisturbed, and reconstituted samples, with the purposebetween the true, particle friction angle, c , and theof studying the effect of in-situ, internal structure, on thecritical state friction angle, c*+. Li and Dafalious ('-OOO)sug*"ested that cf is related to the state parameter (Beenand Jefferies, 1985) of the sand.behavior of the sand. Undisturbed test specimens wereprepared from block samples extracted in the Haifa Bay'epresents a stress-strain "la¥v" for gr'anular soils. If thisRo¥ve claimed that the stress-dilatancy relationregion. In order to improve reliability of stress-strainrelations, Iocal strain rneasurements ¥vere performed,rather than measurements performed external to the soilis the case, a difficulty may, at first sight, appear to arise,specimen. Equipment was developed for this purpose,ratio, (rf/(T , should remain constant throughout theallowing measurements to be made m the small tostraining process. In fact, Ro¥ve actually specified that themedium strain range.str'ains being consider'ed should be the plastic, or slipcomponents of the overall strain; however, he concludedsince Eq. (1) would indicate that during undr'ainedshearing, inIn this article, attention is concentrated on the stress-'hich volume remains constant, the stressdilatancy behavior of the undisturbed sand. It was firstsuggested by Rowe (1962) that the capacity of granularsoil to carry increasing shear stress (r'epresented by anincreasing ratio, ( f/(T , of major to minor principaleffective stresses) is related to the dilatancy rate in thesoil. Ro¥1'e defined the dilatancy rate as - de /d81, wherethat in drained shear, the elastic or recoverablecomponents of the strains are small enough to be8by Houlsby (1991).rgnored However, in the case of undrained shear, ¥vheretotal volumetric strain is zero, verification of the stress-dilatancy r'elation ¥vould require consideration of theplastic component.s of strain. This point ¥vas emphasizedis the volumetric, compressive strain and 81 is the majori)Prof ssor, Faculty of Civil & En¥'ironmentai Engineering, TechnionIsrael Institute of 'Technology, Haifa 32000,Israel (cvrsfsf @.tx.technion.ac,il).ii)iii}Senior Lecturer, dit o.Former Graduate Student, ditto.The manuscript for this paper ¥vas received for revie¥v on June 23, 2005; approved on Ocrober 2, 2006.¥Vritten discussions on this paper should be submirted before September 1, 2007 to the Japanese Geotechnical Society,Bunkyo-ku, Tokyo I 12-001 l. Japan. Upon reql es the closing date may be extended one month_274-38-2, Sen_cr,_oku, FRYD ,IAN ET AL.2sTHE DEFINITION OF ANGLE OF DILATION,sin v = - (2delSince Ro¥ve's pioneering ¥vork on stress-dilatancy, theimportance of considering not only the static, but also thekinematic aspects of the mechanics of granular media hasbecome ¥vell appreciated (e.g. Roscoe, 1970; Vermeer andde Borst, 1984). This has led to the definition of the angleof dilation, /, (actually originally introduced by Hansen,+ de )1(･-c]e- de )= - (2d8r + de )/(2de- de ) (8)The authors had initially felt that a third, more consistent approach to the definition of dilation angle may be tofollo¥v the convention adopted for c', ¥vhich is definedindependently of boundary conditions, as sin c' = (cr; (T )/((Tfa ), and to similarly definep, under all bound-1958), representing the kinematic equivalent to theary conditions, by. Eq. ('-b). Ho¥vever, under triaxialeffective angle of internal friction, c'. The angle ofconditions, this definition often yields negative values ofV/ although there is volumetric dilation (volume increase),dilation is conventionally defined for plane strain condi-tions (e.g. Hansen, 1958; Roscoe, 1970; Bolton, 1986;Houlsby, 1991), and is given as:sin/= - de, ldyP (2a)",**¥vhich, for plain strain conditions becomes:sin v = - (c/e+ cl8 )1(c!8- c!8 ) (2b)¥vhere y ** is maximum shear strain, 8 and 83 are the'' ,,principal compressive strains, and the indexp inchcates plastic strains.It is noted that a positive value of / corresponds toplastic dilation (plastic volume increase). Furthermore,the definition of / according to Eq. (2b) Ieads to theresult that for a mater'ial yielding in plane strain accord-and so its adoption would be unreasonable.The above discussion indicates that althou*'h Eq. (2b)is a universally accepted definition of angle of dilation forplane strain conditions, differ'ent definitions are in use fortriaxial conditions. It should be understood that definition of the functional form of / is arbitrary, and may bechosen according to convenience, although it is desirablethat one universally agreed- on definition be adopted, inorder to prevent confusion. For example, if v is evaluated from triaxial tests, and then used in plane strain finiteelement analyses, different definitions vould result in theuse of different values in the analysis. The commonlyused numerical codes Plaxis (1998) and Flac (Itasca,'_OOO), for example, su*'gest that / be estimated froming to the Mohr-Coulomb criterion in associated plasticity (i.e. obeying normality), /= c'.triaxial compression tests, according to Eq (7), and thenFor loading under other than plane strain conditions,other definitions have been sug_g:ested for v/. Continuingto adopt the definition given by Eq. (2a) (e.g. Houlsby,1991; Vaid and Sasitharan, 1992), V/ in triaxial compression loading, for example, is given by:calculated from the triaxial tests, according to Eq. (3), asin v/ = - (d8 + de + de )/(de - d8 )= - (de + 2de )/(d- de) (3)¥vhere 8* is the axial str'ain, and e* is the radial stra}n.Similarly, in triaxial extension,sin v/ = - (c!e/ is given by:+ -?de )/(de- de ) (4)An alternative definition of v/ has been suggested byVermeer (Vermeer and de Borst, 1984; Schanz and Vermeer, 1996), for plane strain and triaxial compressionconditions, of the form:sin v/= - (ds /(2cle- de ) (5)In plane strain, Eq. (5) degenerates to Eq. (2b):sin v/ = - (c]8? + d8 )1(deT - de ) (6)Consequently, for plain strain conditions, there iscompatibility bet¥veen the t¥vo definitions given byEqs. (2a) and (5). Ho¥vever, in triaxial compression,used in plane strain analysis. It the value of v/ weredifferent value ¥vould subsequently be used in the planestrain analysis. This confusing situation is undesirable.It is obviously necessary to have a univer'sally agreed ondefinition, preferably one which would give a uniquerelationship between v/ and c for all boundary conditions, representing a fio¥v rule for the material.In order to consider the relative suitability of thealternative definitions of / presented above, an analysishas been made of triaxial compression and extensionfailure data presented by Vaid and Sasitharan (1992).Figure I sho vs the relationship bet¥veen c and v/, basedon the results of 53 triaxial compression and extensiontests on Erksak sand, tested at various relative densities,under various confining stresses and follo¥ving variousstr'ess paths. It is seen that equally. good linear correlations are obtained bet¥veen c and / ¥vhen v/ is definedeither according to Eqs. (3) and (4), or by Eqs. (7) and(8), and neither definition of v/ for triaxial conditions isobviously preferential over the other. Assuming that thecritical state friction angle, cg+, of Erksak sand is of theorder of 3 1 ', the relationships bet¥veen c and / Shown inFig. I are of a form similar to the follo ving, su*'g:ested byBolton (1986) for plane strain conditions:Eq. (5) results in the follo¥vin*' definition of angle ofc' = 0.8 / + cg, (9)dilation:sin v/= - (de + 2d8 )1(c!8r - 2de )where cgis the critical state friction an_ :le of the soil.- -,c!8 ) (7)It is noted that the coefficients of v in the equations ofFig. 1, resulting from triaxial tests, are lo¥ver than theAlthou*'h Vemeer and de Borst (1984) did not refer tovalue 0.8 suggested by Bolton for plane strain. Thistriaxial extension, the form of their development leads tothe follo¥vin relation for triaxial extension:observation is reasonable considerin*' that the frictionangle in plane strain conditions is known to be higher'= - (d8+ _,de )1(c!e STRESS-DiLATION OF UNDISTURBED SAND SAivIPLES(a) 1 / from Eqs (3) and (4)LVZ)TLVDT arm ture plat orrn-4540 C-) )C35Outer magne ic slripo( )9)co o compnco(oa)e)', 9a E c = O.38 fLatex ¥.¥;extn31 .i30 - R2 :: O.8834i a 20-10e nb aneinner 1l gnetic strip ,1Specime 1 1!3a(b)IV (degrees)Fig. 2. Local axial deformation measurement system: (a) photograph(b) Ivfrom Eqs (7) and (8)and (b) schematic detail- 45coc40 -oC )(1)e))e)1:Fao )35e,oE c = 0.59V + 30.5830 -tests described in the present paper ¥vere perforrned onLEL,specimens pr'epared from undisturbed block samples,L'_OO mrn x 200 mmx7_OO mrn, ¥vith relative densities ofbetween 600/0-700/0. The laboratory test specirnens ¥vereprepared by freezing the ¥vetted block samples, and thenR2 = 0.8788coring 70 mm dia. specimens. Following cor'ing, the1 o 1 5 2a-5/ (degrees)specimen was held in a split tefion tube, and the ends cutperpendicular, resultin*' in a specimen length of 1 50 mm.The specimen ¥ "as then r'eturned to the freezer f'orFig. 1. c' versus Y/ at failu e from triaxial compression and ex'tcnsiontests (based on data of Vaid and Sasitharan, 1992)than that under axi-symmetric loading conditions. For/ defined according to Eqs. (3) and (4) for tr'iaxialconrpression and extension conditions respecti¥'ely, it isseen from Fi**. 1(a) that the relationship bet¥veen c' and vlfor Erksak sand rnay be expressed by:c' = 0.4 / + cg, (lO)The remainder of this article studies the relationshipbetween c' and v/ defined by Eq. (3), as obtained fromboth drained and undrained triaxial cornpression tests Onspecimens prepared from undisturbed block samples ofsand from t.he Haifa Bay region. The conclusions wouldbe equally valid if v/ were defined by Eq. (7). It should benoted that, as pointed out by Houlsby (1991), such afunction (fiow rule) may be used to express the relationship bet¥veen values at faiiure of friction and dilationangles obtained from different tests on the same material,as was done m Fig. 1, or to express the relationshipbet¥veen mobilized values of the friction and dilationapproximately one hour prio ' to placement in the triaxialcell.A special technique lvas de¥'eloped to allolv localmeasurement of small, axial strains during the tests.Vertical displacements lvere monitored at four, approxi-mately equidistant, points aiong the specimen height,using LVDT'S. As the specimens ¥vere frozen ¥vhen placedon the triaxial cell base, measuring points on the specimen could not be mounted by t.he usual procedure usingneedle points inserted into the specimen. Consequently, adifi rent mounting procedure ¥vas developed. At eachpoint, a measuring platform ¥vas assembled consisting ofa magnetic strip, 0.5 mm in thickness, 2.5 mm in ¥vidthand 25 mm in length, placed bet¥veen the latex confiningmernbrane and the specimen, and a similar magneticstrip, attached to a measur'ing platform, placed on theoutside of the membrane, held to the first strip by magnetic attr'action. A LVDT ar'rnature platform lvas gluedto the outer magnetic strip. Figure 2 shows the setup,together ¥vith a schematic representation. Calibrationsand initial testing on a rubber dummy sampie verified thest.ability and reliability of these mountings, and indicatedangles as a single test pr'ogresses. The latter appr'oach hasno slip at the rnagnetic strip-specimen interf'ace. Endbeen applied in the present investigation.friction bet¥veen the specimen and the end caps ¥vasminimized by spreading a thin layer of silicon greaseTHE SOIL TESTED AND TESTINGCONFIGURATIONThe sand tested ¥vas sampled from an ancient riverbedin the Haifa Bay area, in Nor'thern Israel. The sand isbetween the highly polished, stainless steel end cap, and alatex membrane (both 'ith central holes for drainage or'pore pressure rneasurement) in contact with the specirnenend. The specimens ¥vere observed to remain essentiallycylindrical during shearing.uniformly graded (SP) ¥vith 870/0 of its particles bet¥veenT'he specimen ¥vas confined in a latex membrane, and0.15 and 0.3 mrn dia.; its major constituents are quartztested using silicon oil as the confining fluid. Followin9:and some calcite. Maximum and minimum dry densitiesare 16.16kN/m3 and 14.03 kN/rn3, respectively. Theapplication of a small confinin*' pressure to the frozenspecimen, it vas allo ved to thaw. The specimen ¥vas then rRYDMAN ET AL.30p' (kPa)p' (kPaj100010010oooo,ool i100 200 30040 oIFev :s IE-05x - O e007O.OOI8v = O.0037LOG(p') - 0.0155R2 s: O 9937O.002 . LOAD R2 = 0.9899o'002 J:' JH UNLOAD-RELOADe'0.003o'003o'004 lev s 4E-06x + o OOi 8R2 :: O 9e90.004 -f ev = o.ool9LoG(P') - o.0053･ LOADo,005 - R2 # 0.99i9UNLOAD*RELOAD0.005o.006IFFig. 4. Isotropic consolidatiom, correctcd for membrane penetrationo,007Frg. 3. Isotropic consolidation, uncorrected for membrane penetra-ric strains, as seen in Fig. 4. A comparison of Figs. 3 and4 illustrates the importance of taking account of mem-tionsaturated under a relatively high back pressure, prior tothe application of consolidation pressure and shearing.brane penetration effects with changing effective confining pressure.DRAINED TRIAXIAl. SHEAR TESTSISOTROPIC CONSOLIDATIONIn order to divide strains into elastic and plasticThe result of an isotropic consolidation test performedon the sand is sho¥vn in Fig. 3. This figure indicates asemi-log relationship bet¥veen effective isotropic stress,p', and both total and recoverable volumetric strains, 8,components, a drained triaxial test ¥vas carried out whichincluded seven load and unload cycles, and the resultingstress-strain curve is sho¥vn in Fig. 5(a). It was found(Fig. 5(b)) that the irrecoverable axial strain, 8f, could beand 8 ,. In this work, reco¥'erable strains have beenrelated to the total axial strain, el, through the followin*'defined as elastic strains, and irrecoverable strains aslinear relationship, ¥vith a correlation coefficient, r2=0.999:plastic strains; this definition may need to be reconsideredin the framework of kinematic hardening plasticity, but isadopted here for simplicity. Figure 3 ¥¥*as based on volu-metric strain measurements, without takin*' account ofmerrrbrane penetration; however, ¥vith cell pressureincrease during an isotropic consolidation test, themembrane penetrates into the outer interstices bet¥veenthe particles, expelling ¥vater and indicating a specimenwater content change inconsistent ¥vith the actual volumechange of the specimen. Frydman et al. (1973) found thatthe membrane penetration volume/unit surface areaincreases, Iinearly,vith log ((T ), ¥vith a slope, g.*,expressed as a function of mean particle size, d. Forstandard, 0.3 mm thick latex membranes such as thoseused in the present study, and d in mm, this function wasfound to be given by:g(cm3/cm2) = 0.014 iog (d ) + 0.012 (1 1)8f = 0.98 1 681 (1 3)Fi*･ure 6 sho vs the relationships bet veen mobilizedvalues of sin v/ (as defined by Eq. (3)) and sin c', as ¥vellas bet¥¥'een v/ and c' , based on the results of three drainedtests performed on undisturbed specimens, at effectiveconfinin*' pressures of between 100 kPa260 kPa. In earlycalculations, it was found that values of sin v/ (or v/) indrained tests ¥vere almost identical lvhen based on eithertotal or plastic strains; consequently total strains ¥vereused for all later calculations, and the values sho¥vn inFrg 6 are based on these. From Fig. 6(a), the relationbetween sin v and sin c' is given as:sin vl=2.77 sin c' - I .45 (14)and the relation betlveen c' and v is given as:For the present sand (mean particle size 0.25 mm),c' = 0.4 / + 3 1 .9' (1 5)g+,* = O.0045, and for specimen dia = 70 mm, the volumetric strain as a r'esult of membrane penetration, 8 , due toEquation (15) is seen to be very similar to the relationobtained for Erksak sand (Eq. (10)). Considering that cg,a chan*"e in effective confining pressure from ((7 )* to (cr )bof Israeli sands may be taken as around 32' (Frydman,is given by:2000), it would appear reasonable, on the basis of8* = O.0023 Iog (((T ) /((7f ).) (1 _')When the membrane penetration effect in the presenttests was taken into account, the soil compressibilityvasfound to be significantly reduced, and relatively linearrelationships ¥ 'ere obtained bet¥veen p' and the volumet-Eqs. (10) and (15), to suggest the following relationshipbetween c' and v/ (defined according to Eq. (3)) for sandsunder axi-symmetric loadin ':*c' = 0.4 / + cg, (1 6)If the stress-dilation relationship is truly a basic FSTRESS-DILATIOiN OF UNDISTURBED SAND SA*lvIPLEScomponent of' the constituti¥'e behavior of the sand,12ao -Eqs. (14) and (1 5) should apply, also, in undrained shear.In the remaining portion of this paper, this principle is's 800oool600 l:+i;2<!c) 400 Jss;s:investi**ated.$$;!si',;2co 'UNDRAINED TRIAXIAL COMPRESSION TESTS$oa2a8412el oloT¥vo consolidated undr'ained, tFiaxial tests ¥vith porepressure measurement were performed at consolidationpressures of 80 kPa and 150 kPa. In addition, a test atconsolidation pressure of 180 kPa ¥vas car'ried out with10ad-unload cycles in order to allo¥v separation of axialstrain into eiastic and plastic components, as was done(a)for the drained test. The relationship between plastic (8f),ioand total axial strain (8 ), ¥vas found to be given, in this8case, by:es: e"nO1CLy = O,,9816x,l4= 0.9223el ( 1 7)In order to check if the stress-dilation relationshipR* = O.9997established for the drained tests (Eq. (14)) is also relevantto the undrained tests, the follolving procedure was used:(a) The development of effective stresses, (Tt and (T ,oo2s4108was calculated throughout each undrained test. Changes81 o/oin (Tf ¥vere calculated accounting for change in the cross-sectional area of the specimen under zero volume change,as ¥vell as membrane penetration as a result of changin*"pore pressure and therefore of effective confining stress.(b)Fic.5. (a) Load*unload drained,triaxial stress-straincurve and (b)Plastic versus total axial strain0,5stage of the test is gi¥'en by:8 8 +28 +8*=0 (18)(a)vhere 8* is the compressive volume strain due to membrane penetration, given by Eq. (12).(b) From known values of (Tf and a at each stage ofo 4>s'0,3e 100 kPaCl 200kPo,2A 250 kPaThe overall volume balance during the undrained shear( e;ethe test, sin c' was calculated.o 1(c) For each value of sin c', sin v/ was calculatedofrom the stress-dilation Eq. (14).(d) Incremental values of axial strain ¥vere calculated.1o3o;7o.6o .4.2from test measurements, and then plastic axial strainy = 2 77i9x . I .4486R2 = 0.9332),3increments, def, were calculated, using Eq. (17).(e) Incremental values of plastic radial strain, de ,),4¥vere calculated from Eq. (3).(f) Accumulated plastic axial and radial strains werecalculated from steps (d) and (e). Ieading to accumulatedsinc'plastic ¥'olumetric strain, 8. .(*･) Accumulated elastic volumetric strain, 8+*,, ¥ 'ascalculated, f'rom the expression:(b)40 COe,(D35OeF'.c(Dc' = 0.414,e,F*ioFig. 4, ¥vhich represents the elastic compressibility of thesand.Figur'es 7(a) and 7(b) show curves of' calculated eo102030¥V (degrees)Fig. 6. Stress*dilation relationshipobtained fromdrainetl triax'ial tcstso:1; undisturbed specimens= O (19)and p' was thencompared to the unloading consolidation curve shown in31 .9R2 = O 9322520+ 8*p + 8(h) The r'elationship between 8¥'ersus p', for the two tests analyzed. Although bothspecimens indicate bulk moduli of the same order ofma*"nitude, the sample tested at the higher confiningstress sho¥vs a lower bulk modulus. This is a result of thevariability of densities between test samples. The order of FRYDilvIAN ET AL,32tent with that observed in drained shearing may also beo o006,i'y =: 2E4Sx - 0.00i5 fo o004magnitude of the plastic strains, such analysis must bebased on results of tests in which local, small strainR2 s O.9978o o002identified in undrained shearin*'. Due to the smallmeasurement is performed, and membrane penetrationoIeffects must be taken into account.; -o o002Confusion exists with regards to the definition of-o o004dilation an*"le, V/, under axi-symmetric loading condi-*o o006tions. It has been found that using the original definition,V/= -d8, /dy **, the relation bet¥veen friction angle, c'(a)q; =80 kPa-o o008and dilation angle,-o ool200400600800/, under axi-symmetric loadin*'conditions, can reasonably be expressed as:c' = O.4v/ + cg,p' (kPa)REFERENCESo 0025o 002y = 7E4ex - O.0033F = O.999eO Ool 5l) Been, K. and Jefferies, M. CJ. (19S5): A sta e parameter f'or sands,Geotechniql!e, 35, 991 12.Io ool7_) Bohon, lvl. D. (1986): The strength and dilatancy of sands,Geotechnique, 36, 6578.3) Frydman, S. (2000): The shear strength of? o o005sraeli soils, Israe! ,J.EartJ1 Sciences, 49, 55-64.o4) Frydman. S., Zeitlen, J. G. and Alpan. I. (1973): The-o o005effect in triaxial testing of granular soils, ASrIVI J. Tesl(b)cF3= ISO kPa =-o oO 1;-o ool 5200600400800p' (kPa)nembraneEva!., l(1), 37-41^5) Hansen, B. (1958): Line ruptures regarded as narro¥v rupture zones,Basic equations based on kinematic considerations, Proc. Coiif.Eanh Pressure Prob!en7s. Bnl,sse!s, I , 39-486) Houlsby, G. T (1991): Ho¥v the dilatancy of soils affects theirbehaviour, Proc. lOth Eur. Conf^ on S1 /:fFE, Floreuce, 4,Fig. 7. 8versus p' from undrained tests calculated assuminer stress*dilation F,q. (14)the moduli, rather than their absolute values, should beconsidered.Figure 7 sho¥vs that for the two tests analyzed, theslopes of the relationships bet¥veen e and p' estimated inundrained shear on the basis of the stress-dilationrelationship found in drained shear, are of the same orderas the measured elastic (unloading) slope (4E-06 1 /kPa),sho¥vn in Fig. 4.l 1 89-1 202.7) Itasca (2000): FLAC-Fast Lagrangian Ana!ysis of Conti,It!a, Itasca Consuhing Group, Inc., ivlinneapoiis, Minnesota, USA^8) l,i, X. S. and Dafalious, Y. F^ (2000): Dilatancy for cohesionlesssoils, Ceotechnique, 50, 449-4609) Plaxis (1998): Firlite E!enlent Code,for Soi! and Rock Ana!.l ses, ¥'er-sion 7, (eds. by BFinkgreve, R. B_ J. and ¥rermeer, P. A.), A, A.Balkema, Rotterdam.lO) Roscoe, K. H (1970): The influence of strains in soil mechanics,Geo!echniql!e, 20, l'_9-i70.ll) Rolve, P. ¥V. (1962): The stress-dikuancy relation for staticequilibrium of an assemb y of particles in contact, Proc. Roya!Sociely. A. , 269, 500527.12) Schanz, T. and Vermeer, P. A. (1996): Angles of friction andCONCLUSIONSAnalysis of triaxial tests performed on undisturbedsand samples has sho¥vn that by considering plasticcomponents of strain, stress-dilatancy behavior consis-dilatancy of sand. Georecllniqlre, 46, 145l51 .13) Vaid. Y. P, and Sasitharan, S. (1992): The s ren_'*th and dilatancy ofsand, Can. Geotech. J > '_9, 52,_526.14) Vermeer, P. A, and de Borst, R (1984): Non-associated piasticityfor soils, concrete and rock. Her0,1, 29(3), 1-64_J | ||||
| ログイン | |||||
| タイトル | Experimental Study on the Measurement of S-p Relations of LNAPL in a Porous Medium | ||||
| 著者 | Masashi Kamon・Y. Li・Kazuto Endo・Toru Inui・Takeshi Katsumi | ||||
| 出版 | soils and Foundations | ||||
| ページ | 33〜45 | 発行 | 2007/02/15 | 文書ID | 20978 |
| 内容 | 表示 SOILS AND FOLJNDATIONS¥Iol. 47, No .l33-4S, Feb. 2007Japanese Geo echnical SacietyEXPERIMENTAL STUDY ON THE MEASUREMENT OF S-p RELATIONSOF LNAPL IN A POROUS MEDIUMMASASHI KA ,IoNi), YAN Llii), KAZUTO ENDOiii), TORU INUltv) and TAKESHI KATSU¥. n+)ABSTRACTA simple and effective device for measuring saturation-capillar'y pressure relation (S-p relation) in LNAPL-¥vatersystem is designed ¥vith electrical conducti¥'ity probes, hydrophilic tensiometers and hydrophobic tensiorneters. Withthis device, the S-p relation in LNAPL-water system is characterized. The S-p relation in air-LNAPL system isobtained by a scaling factor method. At a given saturation of wetting phase, it is found that the descending sequence ofcapillary pressures is in the order of air-water, LNAPL-water and air'-LNAPL systems. The descending sequence ofentry pressure and displacement pressure is also in the order of air-¥vater', LNAPL-¥vater and air-LNAPL systems.Furthermore, the relative permeabillty of air is larger than the LNAPL in their corresponding aqueous t¥vo phasesystems, and the relative permeability of the LNAPL is slightly larger than ¥vater in their corresponding g:aseous t vophase systems.Key words: capillary pressure, degree of saturation, electrical conducti¥'ity probe, light non-aqueous phase liquid(LNAPL), relative permeability, scaling factor method (IGC: B121E7)¥'ertical movement and redistribution of mobile LNAPLSwithin the saturated and unsaturated zones. It is veryimportant to determine the characteristics of LNAPLSINTRODUCTIONNon-aqueous phase liquids (NAPLS) are hydrocarbonliquids and volatile organic compounds that are notmigr'ation in the subsurface with the fluctuation ofvaterreadily miscible vith ¥vater and air. Depending on theirdensities, NAPLS are typically classified as either lighttable in order to remediate the subsurface contaminationnon-aqueous phase liquids (LNAPLS) that are lightewater table fiuctuation on the distribution of LNAPL insubsurface, there are mainly three methods. One is aneffectively. In order to analyze and quantify the effects ofthan ¥vater, or dense non-aqueous phase liquidsanalytic method, in ¥vhich, the in-situ complicated(DNAPLS) that are denser than water.When LNAPLS are released into the subsurfaceproblem is simplified, and thus the analytic solution ofthrough spill or leak, they will migrate do¥¥'n¥vardthe in-situ problem is obtained, ¥vith errors to somethrough t.he vadose zone. The fate, flow and transport ofextent. One is a physical simulation, on lvhich, a proto-LNAPLS are governed by complex interactions amon_crcapillary, viscous and gravity force, mass transferbetween phases and chemical and biological reactions.These processes are also affected by factors such astype system (i.e., the in-situ cornplicated system) is simulated ¥vith a model-based system, i.e., an ex-situ device.The ex-situ device is a reductive in-situ system, ¥vhich isobtained by reducing the in-situ system to a scale asrequested by the theor'y of similarity. Another is anumerical simulation. With regard to this method, therelationship bet¥veen the ¥vater saturation and thetemperature, soil and fluid compressibility, soil heterogeneity, volume of spilled LNAPLS and geometry of thespill source. At a LNAPL polluted site, LNAPL forrnscapillar'y pressur'e (S-p relation) is needed. To measurethe capillar'y pressure as a function of ¥vater saturation,the free lens above the ¥vater table or is tr'apped in thepores in the subsurface. Some evapor'ates into the air(volatilization), some sorbs the sur'face of the soilfive main methods are kno¥vn, i.e., Iong column,particles (sorption), and some dissolves into the ground-centrifuge, vapor pressure, pressure cell and Brooks'water (dissolved plume). Fluctuation of ¥vater table,¥vhich occurs due to pumping of groundwater in a largemethod. Each of them has innumerable variations(Corey, 1994); however, the measurement of water saturation in a porous medium is a major task during meas-quantity or seasonal variety of rainfall, can also causeii)iii]IT]Prof ssor, Graduate School of Global Environmentai Studies, Kyoto University, Japan.Graduate Studem, ditto (Currently Lecturer, Sun Yat-sen Universit_¥', China).Researcher, Research Center f )r lvlateriai Cycles and ¥Vaste Management, National Institute for En¥'ironmental S udies, Japan,Assistant Prof'essor, Graduate School of (i lobal Environmentai Studies, Kyoto Unh,ersity, Japan (inui@*mbox.kudpc.kyoto-u_ac.jp).Associate Professor, ditto,The manuscript for this paper ¥vas received for reviel ' on September 24, 2004; approved on October '2, 2006.¥¥fritten discussions on this paper should be submitted before September l, 2007 o the Japanese Geotechnical Society, 4-38-2, Sengoku,Bunkyo-ku, Tok"vo ll2-001 1, Japan. Upon request the closing date may be extended one month.33- 34KAlvION ET ALurement of S-p relations. Although gravimetric samplin_"..electrical conducti¥'ity probes in L,NAPL-¥vater system.method for measuring ¥vater satur'ation is the mostThe other is to obtain the characteristics of LNAPLaccurate method, it can not provide rimely and accuratemigration in a porous medium to simulate accurately anLNAPL distribution in subsur'face.¥vater saturation continuously and automatically,because soil samples must be removed from a soil mass.In laboratory experiments, generally, the non-intrusive ornon-destructive methods should be used to measure fluidsaturation. Widely accepted in situ methods for measur-CONSTITUTIVF, MODF,LINGCapil!ary Pressul'e Headin*' soil ¥vater saturation are radioacti¥'e methods such asIn a t¥vo-phase porous medium system for monotonicthe neutron scattering method (Gardner and Kirkham,displacement of a wetting fluid j by a nonwetting fiuid i,the capillary pressur'e Pij can be given as:1951), X-ray or the gamma ray attenuation method(Host-Madsen and ,Iensen, i992; Illangasekare et al.,1995a, 1995b; Lenhard et al., 1993; Reginato and vanPjj = Pj - P(1 )Bavel, 1964; Tidwell and Glass, 1994). Time Domain¥vhere Pj is non¥vetting phase pressure; and Pj is ¥vettin-'Refiectometry (TDR) method (TOpp et al., 1980), and soon. These methods ar'e quite accurate anri non-destructive; ho¥vever, they require special caution to avoidpossible health hazards or higher investment. In thispaper', ¥vater satur'ation is measured ¥vith electr'icalconductivity pr'obes (Endo, '_002; Kamon et al., 2003).phase pressure.lvli**ration of a fiuid in a saturated porous medium isexpressed by Darcy's law, ¥vhich can also be extended todescribe a multiphase flo¥v (Bear, 1979; Sharma, '_OOO).lvhere p,. is the density of lvater; and g is the scalar magni-In a multiphase fio¥v system, flux of each fluid is afunction of its effective satur'ation (Brooks and Corey,1964). The unsaturated hydraulic conductivity, ¥vhich islinked with the saturation and capillary pressure, shouldbe determined to simulate accurately a L,NAPL, distribu-tion in an unsaturated porous medium. Ho¥vever, therelationships among capillary pressure, saturation andunsaturated hydraulic conductivity ar'e different durin_"._dryin*' and ¥vetting processes because of contact an*'1ehysteresis and non¥vetting fluid entrapment. Due to theInstead of pressures, it is con¥*enient to employ capilla-ry head, h*j , which is defined on an equivalent vaterheight basis by:/1,ji = Pji /p,.g (2)tude of **ravitational acceleration.In the case of LNAPL, and vater t¥vo-phase sy. stem,t¥vo kinds of probes for measurin*' the pore liquid pressures are required. One is hydrophilic tensiometer ¥vith¥vater-wetting ceramic cup to measure pore ¥vater pressure and the other is a hydrophobic tensiometer ¥vith aLNAPL-¥vetting ceramic cup to measure pore L,NAPL.pressure. The capillary pressure is simply the differencebetween the higher one and the lo¥ver one of the t¥vo pressure readin*"s (Dullien, 1992).practical difficulties encountered in measuring thek-STP Re!atiol7sThe relationship bet¥veen saturation of phase,j, Sj, andunsaturated hydraulic conductivity, considerable effortscapillary pressure head h, in unsaturated porous mediahave been made to estimate the value of unsaturatedwith immiscible fluid phases, pair i and,j, is referred to ashy. draulic conductivity from the relationships bet¥veencapillary pressure and saturation (Lenhard and Parker,a ¥vater retention curve or S-p relation, ¥vhere i and ,ji 987a) .tively. A ¥videly accepted empirical parameter form givenby van Genuchten (1980) ¥vas written as (Helmig, 1997):Furthermore, obtaining the relationship bet¥veen saturation and capillary pressure for a different phase in athree-phase system (air-LNAPL,-¥¥rater) is time consuming and no standard procedure is available for simultaneous measurements of the saturation and pr'essure of ¥vaterand LNAPL in a porous medium. Only a few results ¥verestand for non¥vetting phase andvetting phase respec-/1,ijI _ 1)1/" /1.jj>0 (3)= (Sj*l !"'aiEquation (3) refers to van CJenuchten model (VG model),where (x (1 /cm) and n are parameters, and ll7= I - I In.presented so far for the migration of L.NAPLS inThe effective saturation of the,j phase, S]* is defined as:unsaturated sand using large-scale tanks (Kechavarzi etal., 2000). Therefore, researchers have suggested the useSj* - Sj - Sj, (4)of STP relations in t¥ 'o-phase system to predict those inthree-phase sy. stem (Par'ker et al., 1987). Lenhard andParker (1988) developed an experimental apparatus tomeasure directly the relationships bet¥veen saturation andcapillary pressure in a three-phase system ¥vith unconsoli-dated porous media. Their results indicated a closeagreement bet¥veen ¥vater saturation in a three-phasesystem and that in a t¥vo-phase system as a function of¥vater-L.NAPL, capillary pressure.In this paper, there are two features that are bein_"._focused on. O_ ne is to measure the SiP relations lvith thei - Sj*¥vhere Sj* is the residual or the irreducible saturation ofthe ¥vetting phase j.Another famous empirical form ¥vas given by Brooksand Corey (1964) (BC model), and the equation was¥vritten as:/7,,J hdS i";- h.jj>/1(5)¥vhere ), indicates the pore distribution index and /?d is thedisplacement pressure head of the reference two-phasesystem, that is, the displacement pressure head from the; i 'r'.SRELATIONS OF LNAPLphase j to the other phase i.35LJ pL or waterJrIn a porous medium ¥vith multiphase flolvs, Darcy sLaw is extended as follows:Ivj = - (k*j ///j)(rpj - Pig) (6)¥vhere vj is defined as avera*'e velocity of fluid i; Pl ishydrostatic pressure of fluid i; /ti is viscosity of fluid i; pjand k*j are density and eft:ective perrneability respectively.The effective permeability, k,j, is _ :enerally expressed asa function of the intrinsic permeability k of the mediurn,¥¥'hich is defined as follolvs:k*j = kk*j (7)lvher'e k-*i is called relati¥'e permeability of fluid i.The method for predicting relati¥'e permeability is alsoproposed as the VG and BC models, and the value of therelative permeability is estimated from the parameters ofthe S-p relations fitted ¥vith VG and BC models.As for VG model, the relative per'meability of thenon¥vetting phase, k*j, and that ofbe described as follo¥vs:vetting phase, k*j, cani /""" 'k,j=SJ'*[1 -(1-Sj. ) J- (8)l/"""' (9)k,j = (1 - Sj.):.'[1 - S , J-Fig. 1. Experimeutal apparatus for measuring S-p relations in aLNAPL*lvater s, stemvhere 8 and y representing the conductivity of porestructure can be regarded as e = I /2 and y= I /3, respecti¥'ely (Helmig, 1997).As f'or BC model, the values of therri can be expressedas follo¥vs.The drainage process ¥vas continued until LNAPL beganto be pumped out from the bottom. After' draina*'eprocess had completed, the wetting process began. TheLNAPLk*j = S{･3･･),, (1 O)k,, (1 Sj.) (1-Sj･ -;. ,';) (11)vas purnped out of the column from thebottom, and same volume of ¥vater was infiltrated intothe sand sample frorn the top of the column simultaneously. The ¥vetting process lvas completed ¥vhen ¥vaterbegan to be pumped out of the column. Durin_g: theMATERIALS AND EXPERIMENTE.1"pei'iinen ta! ApparatusThe schematic for measuring S-p relations in LNAPL-drainage or the ¥vetting process, there ¥vas al¥vays a liquidlayer above the sand sample in the column to prevent airfrom penetrating into the sand sample. It can be assuredthat the testsvere al¥vays in a LNAPL-water systemwater porous medium system is sho¥vn in Fig. 1. Anacrylic column (35 mrn inner diameter, 45 mm outerduring both the drainage and ¥vetting processes.diameter, and 50 mm in length) was utilized, ¥vith t¥vopairs of tensiometers assembled along one side, and threeelectrical conductivity probes assembled on the oppositeside. A pair of tensiorneter's is composed of a hydrophobic tensiometer and a hydrophilic tensiometer' for meas-Matel'ia!s and Samp!es P/'eparationToyoura sand, ¥vith a particle density of 2.64 g/cm3,compacteci-state void ratio of 0.62, and saturated densityof 2.01 **/cm3, ¥vas used as a sandy porous medium forthe column test. The grain size distribution of Toyourauring the pore LNAPL pressure and the pore ¥vatersand is sho¥vn in Fi*･. 2.pressure respectively. At the same position of a pair ofA sodium chloride solution ¥vith the concentration oftensiometers, an electrical conductivity probe ¥vas utilizedO.05 mol/1 ¥vas used as the initial pore ¥vater to raise theto measure water saturation. Only the pore liquidat the sarne position ¥vere adopted for S-p relationreactivity of the electrical conductivity probe and toavoid the formation of condenser cornponent in the sandsystem (Kamon et al., 2003). The full water saturation ofdescription. A rotary pump ¥vas utilized to pump the poreliquid out of the column.A testing program is cornposed of the drainage processmethod. The sand sample lvas poured into the column viaa funnel in uniform layers. Then, the pore ¥vater lvasand thevetting process. During drainage process, firstly,induced from the bottorn of the column, and thesand sample ¥vas fully saturated ¥vith water. Then porecorresponding volume of the sodium chloride solution¥¥'as filled into the sand medium from the top of thecolumn. Thus, before the drainage process began, thesandy mediurn had been fully saturated with the sodiumpressure, Pj and Pj, and ¥vater saturation data measuredwater ¥vas pumped out of the column at the bottom.Simultaneously, same volume of the LNAPL ¥vas infiltrated into the sand sample from the top of the column.sandy mediurn was achieved by an underwater falling KAl¥,ION ET AL36chloride solution. Paraffin liquid was used as a substitutefor L.NAPL, due to its very lo¥v volatility. at room temperature, negli_9:ible solubility in ¥vater and safety tohealth. In order to distinguish visually the downwardmigration of the inter'face bet¥veen the L,NAPL and the¥vater during the drainage process, LNAPL, Ivas dyed¥vith Sudan 111 ¥vith the ¥veight ratio of 10000:1. Theproperties of materials used in this test are sho¥vn inTable I .WATER SATURATION MEASURF,MENTE!ecti'ica! Conductivity P/'obeConductance (reciprocal of resistivity) of sands ismostly due to the presence of ¥vater, and electrical resistivity is a function of water content since it is the majorconductive material of the soil matrix. In a multiphasesystem composed of NAPL,, air, ¥vater, and pure sand,laboratories. Due to the dif iculty of designing a multichannel system and several seconds needed for measurin_one signal for a four-electrode probe, in this paper threeelectrode electrical conductivity probes ¥vere utilized toestimate the ¥vater saturation via the measurement of theelectrical conductivity of sand system under immisciblet¥vo-phase flow condition. Althou_ :h this electrical con-ductivity probe ¥vas ori>*inaily developed to measureDNAPL saturation in a porous medium, it can also beused to measure the saturation of LNAPL, which alsoacts as an insulator in the L,NAPL,-water system.Compar'ed to FDR and TDR, the electrical conductivity probe designed by Endo (2002) is very cheap and easyto make by oneself. It is feasible for a column test due toits small size. The electrode of the electrical conductivity,¥vhose diameter is about 1.0 mm and length is about 15mm, is almost non-destructive to the sands. Each of themhas three parallel electrodes. Thus, there is no interfer-¥vater ¥vill be the principal conductor of electrical currentence bet¥veen t¥vo adjacent probes. The disadvanta*･es of¥vhile air, sand particles, and NAPL, which have a largerthe electrical conductivity probe are also obvious. Themeasurin** accuracy of this electrical probe for' ¥vatersaturation is slightly lolv. The electrical conductivityprobe is only feasible for the porous media, ¥vhose pore¥vater is electrolyte. When this electrical conductivityresistance, ¥vill act. as insulators. Thus soil system ¥vithhig:her wat,er saturation is endued ¥vith a lower electricalresistivity. The ¥vater saturation in a porous medium canbe measured by the changes in electrical resistivity of thismedium as described by Archie (1942, 1947). Since then,a four-electr'ode probe has been the standard for theprobe is utilized for the measurement of lvater saturation,electrlcal investi**ation of soil system in both fields andnecessary. Thus this three-electrode electrical conductivity probe is not feasible for in-situ situation.the initial voltage of the resistance attached to it is100Ca!ibration of E!ectrica! Collductivity p/･obes.eu,u,Prior to the calibration, it ¥vas confir'med that theconductivity values of the LNAPL, air', and sand ¥verene*'1igible compared to that of the O.05 mol/1 sodium80,15S:.60e)chloride solution by measuring the volta*"e of theSresistance attached to the probe inserted in the pure,,)u),U40LNAPL, and dry sand samples.a)For measuring the ¥vater saturation, po¥ver source of1.0 Vpp (Peak to peak volta*'e of AC) in output voltage:.)=,OG,,20and frequency of O.1Hz,, provided by a Functiono ol 0.1 IoooiSynthesizer, ¥vere selected. Lo¥v volta*'e of AC was usedso that probes could not interfere ¥vith one another, andelectrolytic reactions in the vicinity of the electrodescould not happen either. Data recorded by a data logger10Equivalent Grain Size, D (mm)Fig. 2. Grain size distribution of To,oura sandTable 1.Properties of materials used for measuring S-p relations in LNAPL-,vater systemFormulaAppearanceBoiling point,Ielring pointE¥'aporation rateSpecific gravityPara in liquidSudan 111¥¥raterC_olorless, odorlessC..Hl6NsORed powderColorless> 300'C_< - 10'CViscosity (mPa s)Hazard na ureSurface tension (mN/m)3 1Interfaciai lension (mN/m) 1)Eleclrical conductivity (mS/cm)l) ¥^ ,Ieasured by Ring method (Huh and ivlason, 1975)l OOo C100'COoC_Non¥*olatileO.87InsoiubleI 70 O (20'C)¥¥rater solubilitvH. Ol .OO<0.1 gllNon toxic07 (25'C)6,_.06 (25'C_)OO7'_.75 (7_OoC_) S*p RELATIONS OF LNAPL37io.60.55O.8o.5,:> 0.45CVOL O.GS,De)f:f 0.4CVU,:xa, 04>o o.35.,:lo.30.2o.250.2o 5 1 o 251520Time (min.)Fig. 3. Variet)' of oiltput voltage during a drainage processooo Voltage2 0.4Index,o.6R/Roo.81Fig. 4. Output voltage index-water saturation relation in air*watersystemwas only the output voltages across the resistanceattached to the electrical conductivity probe. In order toestimate the ¥¥'ater saturation of the sand sample, it isnecessary to get a relationship bet¥veen output signals andvater saturations. Generally, this kind of probe needs tothe charging process has gotten its balance then thedrainage process begins.Till point C, the sand sample around the electricalconductivity probe is still fully saturated ¥vith ¥vater.be calibrated for every porous medium sample.After the ¥vater table passes through the electricalAccordin*' to the Ohm's la¥v, if the resistance across thesand sample has a good relation with its ¥vater' saturation,conductivity probe, the output volta*'e decreases ¥vith thereduction of vater saturation of the sand sarnple nearbythe volta*"e across the same sarnple must have a goodrelation ¥vith its vater saturation. Thus the outputthe electrical conductivity probe. At point D, pump anddata logger ¥vere stopped, and the sand sarnple aroundthe probe ¥vas obtained fr'om the column for measurin*'¥vater saturation with a gravimetric method. Durin*" thisvoltage across the resistance attached to the probe couldbe utilized as an important parameter to estimate the¥vater saturation.drainage process, the output ¥'olta*"e at point C, Ro (V) isThe output voltages across the resistance attached totaken as a reference value. Namely, Ivater saturationthe probe, recorded by the data logger with a sampleequals to I if the output voltage, R (V), recorded by theperiod of 0.5 second, are of sine ¥vave. Cosine function,data logger is equal to or bigger than Ro under abased on the fitting method by Chapra and Canalehydrodynamic condition. It is also tested that the watersaturation is zero when R is equal to zero.(1998), was selected to fit the data to obtain the amplitudes of the output signals.The variety of output voltages across a resistanceattached to an electrical conductivity probe in a porousmedium during a whole drainage process is sho¥vn inFig. ,3. Until point A, the sand sample is under aA ir- Water SystelnIn order to obtain the sand sample lvith its 1'ater satu-hydrostatic condition, and fully saturated with the sodium chloride solution. The output voltage firstly decreasesslowly to achieve its equilibrium, due to charging of theration known and its corresponding output voltage valueacross the attached resistance, the drainage process wasimposed by a rotary pump to extract pore water out ofthe column frorn its bottom. When there was no water toflow out of the column, the sand sample located aroundsand sample (Iitani and Masuda, 1975). When waterthe probe was extracted as a specimen for measuringbegins to be pumped out of the column, the water flowincreases the conductivity of the porous medium. Thusthe voltage of the resistance attached to the probeincreases suddenly to point B. Then it maintains a con-water saturation with *･ravimetric method. Its correspond_ing output ¥'oltage value across the attachedresistance was also recorded with a data logger. Thisstant value or decreases slightly to point C, which is theoutput voltage value ¥vhen the water table fell down justabove the electricai conductivity probe. With re*'ard todraining periods to *'et sand samples ¥vith different ¥vaterthe line B to C, it is normally parallel, and the volta*･e atconditions. From Fi*･. 4, a good relationship between S,any point on the line is almost constant. However, if thechargin_ : process has not reached its balance at point Aand the voltage of point A has not got its stable value, theequation shown in Eq. (12). This indicates that a relationship between S, and R/Ro is not significantly affected byline B to C will slightly decreases due to the further charg-the ¥vater fiow condition.procedure was conducted with different draining rates orsaturations. Figure 4 shows the relation between outputvoltage, and ¥vater saturation under different ¥vater flowand R/Ro is observed and expressed ¥vith the empiricalin*' process. Accordin*"Iy, after the sample preparation isfinished, and before the drainage process begins, the sandS++ = A(1 .O - eB!?/R.) (1 2)sample fully saturated with water should be placed forseveral hours under a hydrostatic condition. Only whenwhere S,+ is water saturation; and A and B are fittingparameters respectively. KA*¥*iON ET AL.381t S rnple (S nd, LNAPL &Water), W ,Mixed wi h EtheThen ltrated v th 0.22 m iteO.8::Ol Sand (W*), W ter&EtherCU OGLNAPL (WL), Ether & WaterL .::Heated atHeated at 60 'CiO"CSar d (W=)C1:U)LNAPL(WL), jrnount of w ter fa,D.4i.':l:A small0.2Dehydrated wi h Siiiea GelWashed with EtherFiitr ted with O 22 m ilteoLNAPL (WL), Ether0.2o 4 o.8Voitage Index, RjRoo=Lk r i "o.6He ted at 60 'c *Fig. 5, Method for measuring the lvater content of a sand samplecontainina both LNAPL antl waterFig. 6. Output voltage index*wa:ter saturation relationwater system¥ llLNAPL- Water System'In L,NAPL-water system, it ¥vas found that, to controll)¥:v . i' Ceramlc Cup¥ , ' Sprayed withdifferent drainin*' rates and dr'ainin*' periods in theWater-Proof Materi aleffective. After LNAPL-1vater interface passes a fullysaturated sand sample, most of the pore vater is com-l'pelled out of the sample, and the ¥vater saturation of themeasure the ¥vater saturation, because the sand sample.lol: se;calibration of these electrical conductivity probes ¥vas notthe sand sample ¥vas removed from the column, thenormal gravimetric method could not be utilized toin LNAPL-¥¥;the ¥vater saturations of the sand samples by usingsand sample is nearly constant. It is more effective toobtain sand samples ¥vith different water saturations bycontrolling the LNAPL-¥ *ater interface position. After1.lPressu re Transd ucerFig. 7. Schematic of modif ) ing a h .'drophilic tensiometer to be ah) drophobic oneof the electrode, the pore ¥vater may not form ¥vater filmwas composed of pure sand, LNAPL and ¥vater. Thus aaround the electrode. In addition, there would be amethod sho¥vn in Fi**. 5 ¥vas designed to separate sand,possibility to change the we ability of the electrode fromLNAPL. and water out of the sand sample.¥vater-¥vet to oil-¥vet.In order to testify the feasibility of this separationmethod, two blank tests ¥vere conducted. For' the testCapi!!ary Presstll'e Measuren7e/7tsample preparation, sand, water and LNAPL of kno¥vnTensiometers (SWT5, Delta-T Devices Ltd.) ¥vereweights were mixed together and kept for '_4 hours. Theaverage error between the water saturations determinedby this method and the reai ones is only 1.660/0.utilized to measure pore liquid pressure. Generally, aThe S, -R/Ro relation in LNAPL-¥vater system isshown in Fig. 6. On the basis of Figs. 4 and 6, it can befound that the SwR/Ro curves in air-¥vater and inLNAPL,-water systems are simiiar. The difference is thatthe curvature in air-¥vater system is somewhat bi*_ger,although the conductivity of the L,NAPL and the air isne*'1igible compared to that of the sodium chlor'ide solution. This ¥vould be caused by the wettability. ofthe gildedtensiometer is designed to measure the pore waterpressure, and a hydrophobic tensiometer suitable formeasuring the LNAPL pressure, ¥vas not available. Thus,a ceramic cup of a normal tensiometer should be modifiedto be hydrophobic. There are some modification methodsproposed, one is spraying water-proof material to theceramic cup (Endo, 200'_; Kamon et al., ,_003) and theother is soaking the ceramic cup in a Glassclad 18 solution for 20 minutes, then oven-drying it at 1000C for I .5hours (Busby et al., 1994). The former method ¥vas select-electrode of the electrical conductivity probe (Kamon eted in the experiment. The schematic of a hydrophobical., 2003). Assuming that the vettability of the electrodeis'ater-¥vet in the water-air system, and the pore airtensiometer is sho¥vn in Fig. 7. The hydrophobic tensiometer consists of a porous cup sprayed ¥¥*ith the ¥vaterproof material, saturated with LNAPL., and a shaft filledhaving no excess pressure, the pore ¥vater forms ¥vaterfilm around the electrode, and the contact angle bet¥veen¥vater and the electrode becomes less than 90'. In the¥vith LNAPL and de ･aired ¥vater for the prevention ofLNAPL volatilization from the scre¥v-type connection¥vater-LNAPL system, Ivhen the pore LNAPL invadesbet¥veen the shaft and the pressure transducer, and theinto the water-saturated pore space ¥vith the pressurestabilization of the output signal from the pressure trans-hi**her than the pore ¥vater pressure and hits to a surfaceducer. S ) RELATIONS OF LNAPL39o-204'1!'L(3.5a,403CaCL2.5-60L:(Q, 2L=u'Q, i-5<-80a,L i,L-i o o20oo.5o408060100Voitage (mV)-25 - .1o -5 o I oVo[tage (mV)-2015Frg. 8. Calibration results of h)drophilic and h¥5Fig. 9. Calibration result of the tensiometer under negative air pressuresdrophobic tensiome-tersDuring measur'ement of pore liquid pressure, the signalfrom tensiometer recorded by the data logger was outputvoltage. A relation between voltage and pressure could beobtained in the calibration test (Fig. 8). The tensiorneteris calibrated under a positive pressure condition. It is verydifficult to calibrate a tensiometer' with ceramic cup fullysaturated with water or LNAPL under a negativepressure condition, because it is very difficult to measurethe variety of negative pressure of the ¥vater or LNAPL ine,U)Drain gs,,,,L':L(f5Opd/pe---We ingSlr_Shthe ceramic cup of a tensiometer ¥vith present testingtechniques.oSaturation1In this colurnn test, four tensiometers were usedtogether with one power supply. The output voltages oftensiometers are recorded by ¥vay of a data logger.However, the output signals from these tensiometers ¥villinterfere with each other due to the limitation of the data10gger, ¥vhich is a singie end data logger. Thus the isolation amplifier (Endo, 2002)'as utilized between thesetensiometers and the data logger. It resulted in the voltage of zero pressure of every tensiorneter being different.Ho¥vever' their slopes of relation between the voltage andthe pressure are almost the same. If the isolation amplifier is not used, the output voltage of every tensiometer atzero pressure is zero.When liquid was filled in the column ¥vithout. sand atdifferent liquid levels, the hydrostatic or LNAPL-staticpressures and their corresponding output volt.ages fromhydrophilic or hydrophobic tensiometers were measured.It was also found that ¥vhen liquid ¥vas purnped out of thecolumn (hydrodynamic or LNAPL-dynamic condition),the voltage from a tensiorneter is slightly different fromthat in a liquid-static condition even at the same liquidlevel. Figure 8 indicates that the correlation coefficientsrange from 0.9997 to 0.9999. Voltage-pressure relationsof hydrophilic tensiometers in hydrostatic condition andthose of hydrophobic tensiometers in LNAPL-dynamiccondit.ion ¥vere selected for Slp relation measurement.Although ¥ve can not calibrate under a negative liquidpressure condition, ¥ve could calibrate the pressuretransducer of a tensiometer under a negative air pressureFig. 10. Definition of p* and pd during drainage and wetting processes(Core .', 1994)condition. The calibration result is shown in Fig. 9. It isfound that the slope of the voltage-pressure relation is0.96, and it is very close to those of tensiometers calibrat-ed with the positive pressure. Moreover, the relationbet¥veen pressure and output ¥'oltagae is linear. From theseobservations, it is acceptable that the negative pressure isextrapolat.ed based on the voltage-pressure relationsho¥vn in Fig. 8.RESULTs AND DISCUSSIONSS-p Re!ations in Air- Water and LNAPL- Water SystelnsThe displacement pressure head, pd, is the capillarypressure at which the first desaturation on a drainagecycle occurs. At a pore space initially f'ully occupied withwater, a finite value of capillary pressure, designed as p*,must be exceeded before non¥vetting fluid can intrudeinto this elernent of the pore volume. The value of p* iscalled entry pressure. The definition of p* and pd is sholvnin Fig. 10. pd is some¥vhat smaller than p* (Corey, 1994).The measured S-p relations in the LNAPL-'atersystem under the drainage/wetting process are shown inFig. I I , 1 'here the one in the air-water systern under thedrainage process (Kamon et al., 2003) is also plotted.These STP relations are obtained at the same test condi- KAMON ET AL.40O:::160leoi40140O:C1 20Ec,_c,c'_100oLi*::u,co2u'Q,8ooo80SCLZ,:60CL40,v1 20B'LQeo40c5OO20oo,e 0,8 io.2 o,4Water Saturation20oo o.4 o.8 1o 2o.6Water Saturation(b)(a)Fig. Il. Measured S-p relations in Toyoura santi: (a) Fitted lvith VG model and (b) Fitted lvith BC modelTable 2. Parameters of Slp relations fitted lvith VG and BC models intlvo*phase sl.'stems¥IG modelA ,? S RBC model) h ;. S* R ! }OO'_1 7 37 O.15 O 78 39.21 4.15 O.14 O 770.039 7.77 0.lO O.91 18.21 2 71 0043 0.90LNAPL*¥va erAir-LNAPL2)O,,043 7 37 O.lO16.67 4.15 O.043Scaled parameters3) 0.021 7.51 O.OO O.90 38.04 3.79 0.00 O.85Air-¥vaterl) R is a correlation coefficient2) The Slp rela ions are obtained ¥vith scaling factor method3) Scaled S-p relation is obtairled aTnong aiF-1va er, LNAPL-1vaterinto the pore, is trapped with a degree of saturation evenwhen the water infiltrated again.Prediction of STP Relation in A ir-LNAPL Systel71The electrical conductivity probe can not be utilized inair-LNAPL system for measuring Slp relation becausethere is no pore water with some electrical conductivity inthe system. For a rigid porous medium it is only necessaryto measure STP relations for t¥vo of the three t¥vo-phasesy. stems (e.g., air-water, air-organic or organic-water).S-p relations for the third system may then be predictedtions including the type of sand used, the porosity of thesand samples, pore ¥vater, test equipments. The capillary(Lenhard and Parker, 1987b). In the scaling procedureproposed by Parker et al. (1987), S-p relations of twophase air-water, air-organic and organic- vater systemsare adjusted to obtain a unique scaled function for agiven porous medium after applying a linear transforma-pressure head in LNAPL-¥vater system at a _ :iven watertion to capillary heads such that:and air-LNAPL systemssaturation is slightly lower compared to that in air-¥vatersystem. This tendency is consistent ¥ 'ith the results byS, .(fi /1 )=S*(h*) (13a)Parker (1989) and Sharma and Mostafa (2003).S, .(ft ,./1To obtain the residual water saturation, t¥vo methodscan be utilized. One is to define residual ¥vater saturation,*+* ***. ) = S * (/7 *) ( 1 3b)S .(fi.. h.. ) = S *(h *) ( 1 3c)more or less, objectively by extrapolation using measur'edwhere a, o, and Tv refer to air, or'ganic substance, e.g.,data, and the other is to determine residual ¥vaterLNAPL,, and water phases respectively; Sj*=(Sj-Sj*)/saturation at some arbitrarily large capillary pressure(Corey, 1994). To define the residual ¥vater saturationwith extrapolation method, it should be noted that thisprocedure can become quite elaborate when only a smallportion of the soil-water retention curve is measured (vanGenuchten, 1980). In this paper, measured S-p relationdata ¥vas fitted to VG and BC models respectively withmodified Gauss-Ne¥vton method (Hartley, 1961). Thefitted S-p relations with VG and BC models are alsosho¥vn in Fig. 11. Fitting parameters of VG and BCmodels are sho¥vn in Table 2.Figure 1 1 also indicate that the S-p relation of ¥vettinprocess is much different to that of drainage process, andthe hysteresis is clearly observed, as reported in pre¥'iousresearches. This is because LNAPL, ¥vhich has infiltrated(1 - Sj*) is the effective saturation of ¥vetting phase j; Sj* isthe irreducible saturation of ¥vettin_9: phase j;ij is a fluidpair-dependent scalin_ factor; and S*(h*) is a scaledfunction bet¥veen the saturation of ¥vetting phase andcapillary pressure head. At a _g:iven saturation of wettingphase, Eq. (13) indicates that:fi*, /1*, =P･, h.,, p*.ll.. (14)For a rigid porous medium, scaling coefficients are relat-ed by Lenhard and Parker (1987b):1 , 1 1 (15)fi*,. ' fi*. p*wAccordingly, if fi*. is kno¥vn, at a gi¥'en saturation ofwetting phase, h** can be obtained depending on Eq. (14),, rS-p RFLATIONS OF LNAPLiso160o 140O 140So 120o 120:c41::'D'l'L:5su) Ieoq,u)iOO,,,a'tae'a* 80iL 80.60' _-, 60.015 40O 40's'S:,:2Q'g 2020oU)O0.6 1o 0.4 0.8oo.20.2o.6o.4o.81Effective Satu rationEffective Saturation(b)(a)Fio. 12. Scaled effective saturation-capillan.' pressure relations in To .'oura sand: (a) VG modei (p**,, = 1.942. P= 2.062) and (b) BC. model (P<,,* =l.739, fta*' = 2.352)OIsoIGO140140O1201 20::::Eo loo100*CDo:co 80:s80'LGo,,,CD,* eO:S*-40O 20,40ce20o0.2o.4 0.8 1Saturation(a)Fig. 13.ooo.2o.4o G08Saturation(b)Slp relations in Toyoura sand fitted lvith: (a) VG motlel and (b) BC modeland S-p relationship in air-LNAPL system can be¥vetting fluid is assumed to be a constant for all two-phaseobtained. The procedure for predict.ing STP relationshipin ail'-LNAPL system is described as follows:(1) Taking the air-1vater syst.em as a reference fluidpair system, and setting fi*w= 1.0;systems according to Lenhard and Parker (1987b), whichindicates that the residual saturation of wetting fiuid,(2) Fitting SrP relationship data in the air-¥vaterdata, in LNAPL-water system. Furthermore, the relationsystem to obtain S*(/7*);(3) Obtaining P･*+ depending on Eq. (13b) and fi*.depending on Eq. (15);(4) calculat.ing S.* and h** depending on Eq. (13c).where S.*=(S.-S.*)/(1 -S.*), and S.* is the residualsaturation of lvetting phase (LNAPL) in air-LNAPLsystem.In the air-¥vater and the LNAPL- ¥'ater systems, ¥vateris a ¥vetting phase fiuid; both air and LNAPL are nonwetting fiuids. Compared to air. LNAPL is a wetting phasefluid in air-LNAPL system. The residual saturation ofLNAPL in air-LNAPL system is assumed to be 0.10,which is the residual sat.uration of ¥vater fitted with testamong the scaling coefficient (Eq. (15)) is of a theory. Inthis paper, the S-p relation in the air'-LNAPL can not beobtained experimentally. Thus Eq. (15) is utilized to esti-mate the S-p relation in the air-LNAPL system.The VG and BC parameters of predicted Slp r'elation inthe air-LNAPL system are sho¥vn in Table 2. The scaledeffective saturation-capillary pressure relations are sho¥vnin Fig. 12, and all the fitted S-p relations in air-water, air-LNAPL and LNAPL-¥vater systems are shown in Fig. 13.It can also be found that descending sequence of capillarypressure head at a given saturation of wetting phase is in KAlvION ET AL.42i1o.8i3, O.8o 6.aCVCD O.e,:gG,>e, O.4o.4.>t*,:,a,o(O( O 2o-2oo-2e.4 o.8o,so1oWater Saturationo.2o.6 e.8LNAPL Saturation1(b)(a)Fig. 14.o 4Estimated k-S relations in To¥.'oura sand: (a) Lr ITAPI,*1vater s}stem and (b) Air*LF {'APL sl.'stemthe order of air-¥vater', LNAPL-¥vater and air-LNAPL,represented ¥vith a group of parallel capillary tubes lvithsystems. This tendency is also consistent ¥vith the resultsdifferent radiisho¥vn by Parker (1989) and Sharma and Mostafa (2003).conjunction ¥vith the more complicated pore geometryIn air-water and LNAPL-¥vater systems, the entrymodel of Mualem (1976). Due to the differences inparameters bet¥veen Burdine model and Mualem model,pressure and displacement pressure of air-water systernare larger than that of L,NAPL-water system. This resultsug (7ests that, in their corresponding aqueous t¥vo phaseThe van CJenuchten model is applied Inthe relati¥'e permeability of BC model is al¥vays smallerthan that of VG model (O_ ostrom and Lenhard, 1998).systems, L,NAPL is easier to displace ¥vater than airWith regard to the relative permeability, fe¥v literaturesduring the draina( ge process. In air-¥vater and air-LNAPL,are found on the differences bet¥veen the relativesystems, the entry pressure and displacement pressure ofair-¥vater system are larger than that of air-LNAPL sys-permeability measured by ¥vay of test and that predictedtem. This also suggests that LNAPL is easier to beby ¥vay of BC and VG models in porous media in ¥vhichLNAPL exists. Ho¥vever some simplified researches havedesaturated than ¥vater in their correspondin( - gases t¥¥'obeen made. In a fracture net¥ *ork, it ¥vas found that, bothphase systems.the VG and BC models *'enerally underestimate relatlvepermeability values, ¥vhile the BC model gives betterresults than the VG model (Liu and Bod¥'arsson, 2001).In porous media, the predictions based on the BC modelalso agreed better ¥vith exper'imental observations thanRe!ative Pernleabi/ity-Satu/'ation Relations in LNAPLWater anc] A ir-LNAPL SystelnsBased on Eqs. (8) to (11), a relation between therelative permeability and the saturation of ¥vettin*' phasecan be estimated based on the SrP relations obtained. Theeffective saturation of wetting phase j here is described as;Si* = Sj - Sj* ( 1 6)1 - Sj* - Sl*¥vhere, Sj* and Sj* are the irreducibie saturations of ¥vettin_"._phase ,j and non-¥vetting phase i, respectively. . Sj* can beobtained ¥vith extrapolation method and a good estimateof S;* for homogeneous and isotropic media is 0.15(Corey, 1994).the predictions based the VG model (Schroth et al.,1998). It can also be found that the BC model used byengineers successfully predicts the relative permeabilitycur'ves (Dana and Skoczy. Ias, 1999). In addition, modifiedprediction methods for the relative permeability includin*' the effects of ¥vettability, contact angle of soiiparticles, and DNAPL entrapment under ¥vater-DNAPLtwo-phase condition have been also developed (Demondand Roberts, 1987; Morro¥v et al., 1985). Ho¥ve¥'er, further research is required to develop the model to deter'mine the relative permeability of NAPL and evaluate itsThe relatlve permeability-saturation relations (k-Srelations) estimated for air-LNAPL, and LNAPL-¥vatersystems are sho¥¥'n in Fig. 14. The values of relativevalidity.permeability of nonwetting fluids (e.g. , air in air-L,NAPLFig. 15. It indicates that the relative permeability. of air issystem and LNAPL in LNAL- vater system) estimatedlar*'er than that of LNAPL m therr correspondmgwith BC model is slightly smaller than that estimated ¥vithaqueous t vo phase systems. It also sug*'ests that theThe differences of k-S relations bet¥veen alr-¥vater,LNAPL-¥¥'ater, and air-LNAPL systems are sho¥¥'n inVG model at a given saturation of ¥vetting phase (e.g.,relative permeability of the LNAPL is sli_2:htly lar*"eT thanwater in air-¥vater system and LNAPL in air-LNAPLthat of ¥vater in their correspondin_g: gaseous t¥vo phasesystem). On the other hand, the relative permeability ofwettin_g: fluid estimated with BC model is nearly the sameas that estimated ¥vith VG model.estimated based on Eqs. (8) to (1 1), these differences areThe Brooks-Corey model is applied in conjunction¥vith the Burdine theorem (1953), in ¥vhich, pores aresystems. Since these relative permeability values aredue to the shapes of S-p relation, ¥vhich includes theeffects of many factors (dynamic interfacial tension,viscosity, and so on) on the multiphase infiltrations rSlp RELATIONS OF LNAPLi1i , c.8? 0.8..:a''43'SG)g O.6o.6ha,o'La,> 0.4G)> 0.4!o)Ce 02a( o.2o0.6 1oo 0.2Saturation of Wetting Phaseo 4o.2 0.6 o.8 io.4o 8Saturation of Wetting Phase(b)(a)Fig. 15.Differences in k*S relations between air*water, LNAPL-water, and air*LN 7APL s)'stems estimated using. (a) VG model antl (b) BC modelproperties, obtained for the corresponding phase system.CONCLUSIONSIn this paper, the experimental system for' the measure-ment of migration character'istics of LNAPL (i.e., S-prelation) in LNAPL-water system in the porous mediumis described. Using this system, SrP relation in theLNAPL-¥vater system is characterized, and that in theair-LNAPL system is determined by the scaling factolmethod. The main results obtained are as follows:(1) A simple experiment device system ¥vith electricai(6) The k-S relation is obtained with parameters fitted¥vith VG and BC model in LNAPL-water and airLNAPL systems. The relative permeability of'LNAPL obtained using BC model is slightly smallerthan that obtained using VG model, and the rclativepermeability of ¥vater obtained using BC model issimilar to that obtained using VG model in bothLNAPL-¥vater and air-LNAPL systems.(7) The entry pressure and displacement pressure ofair¥vater system are larger than that of LNAPL-watersystem. It suggests that, in their correspondingaqueous t¥vo phase systems, LNAPL is easier toconductivity probes and tensiometers is effective fordisplace water than air at the beginning of drainagemeasuring S-p relation in LNAPL-¥vater systern.process. The entry pressure and displacement(2) Relations betlveen ¥vater saturation and outputpressure of air-water system are larger than that ofvoltage across a resistance attached to a calibratedelectrical conductivity probe were determined in theeasier to be desaturated than ¥vater in their corre-laboratory calibration tests. The output voltage¥vater saturation relation in LNAPL- vater system isslightly different from that in air-¥vater system. Inair-water system, the curvature of the relation isslightly larger.(3) The method for modifying a hydrophilic tensiome-air-LNAPL system. It also suggests that LNAPL issponding gaseous two phase systems.(8) The relative per'meability ofair is larger than that ofLNAPL in their' corresponding aqueous two phasesystems. In addition, the relative permeability of theLNAPL is slightly larger than that of water in theircorl'esponding gaseous t¥vo phase systems.ter to a hydrophobic one is proved to be effective formeasuring the pore LNAPL pressur'e even in thecase of a highly-viscous LNAPL such as paraffinliquid used in this study.(4) A method to separate sand particle, LNAPL andwater from the sand sample collected from thecolumn test ¥vas designed and pr'oved to be effectivein the laboratory experiments.(5) At a given water saturation, the measured capillarypressure in LNAPL-water system is slightly smallerthan that in air-¥vater systern. In reference to scalingfactors, Slp relation in air-LNAPL system is obtained. The descending sequence of capillary pressure is in the order of' air'-water, LNAPL-water andair-LNAPL systems. This is consistent ¥vith theresults by Kamon et al. (2003) and Sharma andMostafa (2003).I -ACKr l OWLEDGEMEN1'SThe authors vould like to acknowledge Dr. HuyuanZhang (Former JSPS Research Fello¥v, Graduate Schoolof Global Environmental Studies, Kyoto University,Japan) for his support in the laboratory test.NOTATIONA: fitted parameterB: fitted parameter": '-raviiationai accelerationh* j: capillary pressure head bet veen fluid pair of i and jJld: displacement presst re headh*+*: capillary pressure head in air-¥vaier systemho**: capillary pressure head in LNAPL-water systemh* : capillar_v pressure head in air-LNAPL s.¥'stem 44KAMON EτAL．permeab三1i［y of a med1し1m ん：eEective permeabi蕪t》・of i pl｝ase玉n muitiPhaseβow caseんci：んrilん『」＝reiatlvepermeabilityo顛o鷲wet￡ingP鼓ase’relatlvepermeab1lltyofwe［ヒingPhase／9） Dana，E．and Skoczy歪as，F，（玉999）：Gas relat玉ve permeability and porest田c田reofsandstones，／1π．ノ．RocんMθ‘h．M∫η．5ご．，36， 613−625．10）Demond，A，H、and Roberts，P．V．（1987）l An exam膿atlon of ’η：parameter臨ed wl漁van Genuc厩en model n：parameter撫edwl出、評anGenuchtenmodel μ勿α1∼ε∫α〃’．βε〃．，23，6王7−628．ρc：entrypressure11）Dullien，r．A。L、、（1992）：Porous Me嵌a：F1置”ゴ71／wη，∫poπ017ゴPo肥ρd：d呈splacement pressure S’ri’‘1∼’ヂθ，2nd ed、，Academ圭c Press，Califor鷺ia，USA。nonwe！t玉ng P蝕ase pressure12）Endo，K．（2002）：C負aracter1stics of DNAPL mlgration andwet亘ng phase pressure assessment of DNAPL distrlbu【lon1n a contam魚ated s1te，PhO P監：Pj： rela謡ve permeab玉韮ty relatio鷺s for two−phase負ow in porous me（i玉a，1㍉：capillary pressure between phases pa1r of’a職d／ D’55θ’”θ’ioη，KyotoUnlverslty，Japan（1nJapanese）．Pa、∼：cap玉11ary pressure bet、veen a玉r and、、「ater13） Gard扇er， 、V、 and Klrkham， D． （1951）l De葛ermlnat1o臓 of so11Po、、：capillary pressure be［、veen LNAPL and wa葛er 磁o1sture by neu［ron scatter玉ng，So’1Sc’．，73，39玉一40LPユo：capmary pressure betweeR air and LNAPL夏4） ｝｛ardey，H．O。（196王）：丁血e modi最ed Gauss−Newto【叢metbod for theharmonlc mean radius of curvature ofτ｝1e interface bαween 倣tingofno曲nearregresslonfunctlonsbyleastsquares，rθ‘1η10一 り R‡l凶aselandphase／ 〃1（∼’r’c5，3（2），269−280，harmonlc1nean rad沁s of cur、’ature of由e interface15）｝｛elml9，R．（1997）：M’〃fψhα5召r101∼レα1∼ゴ乃ηノ1∫ρo’トrP／oご8∫5θ∫’17r加 R：outPU［vo韮tage Ro＝referenceOUtpu置voltage S∼め5ど〃プiαごθ，Springer，Berhn．16）Host−Madsen，，」、and Je騎sen，K．冠．（1992）：Laboratory and S、、：watersaturation 3、、ご：e餌ect玉ve water saturation ∫ノyd∼ o1．，135，13−52． So豊：effect1ve saturatiou of LNAPL玉7） Huh，C．and 置〉lasoR，S、G． （1975）：A r玉gorous t飯eory of ring ∫」：saturation of wett魚9P翁ase／ Sβresidual satura首on tenslometrycolloldpolymer，S惚∼‘θ，253，566−58018）Iitanl，K，andM臓suda，H．（19フ5）：Au［omatlcprocessofpowder，efぞective sat雛rat1on of we−t玉厳g pbase 賜じ： Slrlresidual saturation of nonwe柱ing Pぬase’ 畠r＝ res玉dual saIuralion of wett玉ng Phase／S＊（1ブき）1scaied saturat玉oa＿cap玉艮ary島ead func“onvelociこyof伽ldinaporousmedium ど「i＝ 鷺umerical invest1gation of lmΣn玉sc1b叢e rnul【ip員ase 録ow in so貢，．ノ， Thθノ〉’んんα11ノぐ09』yo5hi111Z）置〃1ゐ’ゴ．，Japa鷺（in、lapa鷺ese）．19）Illangasekare，丁．H．，Ramsey，」．L，Jensen，K、H．andBut［s，M． B、（1995a）：Experimenta夏study of movement a録d distribution of denSeOrganlCCO飢amlPantS魚ぬe芝e1っge臓eOUSaqUlferS，ノ．CO’π． H』ド（1r．，20，1−25，total we玉ght of sample includlng sand，LNAPL and water20）Illangasekare，T、H、，Armbruster III，1…，ト，L and Ya葛es，D．N． 耳1s：welghtofsand （1995b）： Non aqueous pilase 翻uids 玉n heterogeneous aqulfers， rFLlwei黛嬢of LNAPL Experimental Study，／．E’1vかoη．五πg。，571づ79． α1parameter且貰ed wiI｝宝van Genuc｝1Ien（VG）model2玉）KamonM．，E陰do，K．andKatsumi，丁。（2003）：Measuringtheた一S一ρ βユ、、：a1卜water gu玉d pa玉卜（玉ependent scaling factor relaξions oR DNAPLs m玉gr飢ion，Eηg。Gθ01。，70，351−363、 β。、、：L醤APL−water丹uid palr−depende瓢scali鷺g factor22）Kecbavarzi，C．，Soga，K．and黛彗art，P。（2000）：Mult玉spectral玉mage β急Q：alr−LNAPL f沁ld palr−dependen重scalingねctor ana｝ys玉s職et簸od to de葛ermlne dynam玉c織u玉d satura額on distrlbution ρ、∼：dens貢y Qf waτer in two−d圭mensional threeイluid pbase flow labora覧ory experiτnents， ！｝1parame【er fitted w琵ぬBrooks and Corey（BC）model ノ。Co1π．κ．yゴ1㌦，46，265−293， ε1parame【erofVGmodel23）Len｝1ard，R，」．and Parker，」．C、（1987a）：A model for hysteretic μ1：viscosity of l P｝1ase coRst1tutive relaこ圭ons governing multip｝｝ase fiow＝2、 Permeability− rvloIall σi｝＝1nterfac玉al tens玉on between pぬases’and／ saturat玉o簾relatio取s， 昇■‘πθr∫∼θ50μ1一．Rθ5．，23，2197−2206． σ藷、∼：i磁erfaclaヒens沁nbetweenalrandwater24〉 Lenhard， R． 」． and Parker， ．L C． σo、、＝ln！erfaclal tension beτwee臓LN．A。PL a簸d waτer Pred玉ct玉o員 of saεuratio鷺一pressure relat1ons短ps in three−phase σ301 i鷺terfaclal tenslon between alr and LNAPL（王987b〉： r〉leasurement and pQrous media systems，ノ．Co11’．劫ノゴ1ト．，1，407−424．25）Lenilard，R．J．andParker，」．C．（1988）IExperimentalvaiidaこlonofREFERENCES1〉Arc為ie，G．E。（玉942）：Theelectrlcalresistivitylogasa蹴a1dindeter− mining some reservolr￠haracτeris【lcs，71四αη，∫、擁，1，λ4、E．，茎46， 54−6玉．2）Arc駐le，G、E．（1947）；Eleαrlcalres1stivityanaidlncQre−a鷺alysis i厭terpreta【ionヲ βμ”． 〆玉1η． ！1550c． Pαr． Gθ01．， ！1、1、ハ4，五二， 31（2）， 350−366．3）Bear，J．（1979）：Hアゴ1’σ疋イ1’050∫（｝rα’ηゴw醒θ1明，McGraw−Hl蹉，New the tぬeory of extePding two−P喪ase saζuration−pressure relat1o【1s芝o three−flu玉d p｝｝ase systems for 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| ログイン | |||||
| タイトル | A Comparative Study between the NGI Direct Simple Shear Apparatus and the Mikasa Direct Shear Apparatus | ||||
| 著者 | Hideo Hanzawa・N. Nutt・T. Lunne・Y. X. Tang・M. Long | ||||
| 出版 | soils and Foundations | ||||
| ページ | 47〜58 | 発行 | 2007/02/15 | 文書ID | 20979 |
| 内容 | 表示 rSOILS AND FOUiNDAT ONS¥rol. 47, No,4758, Feb 2007Japanese Geolechnicai SocietyA COMPARATIVE STUDY BETWEEN THE NGI DIRECT SIMPLE SHEARAPPARATUS AND THE MIKASA DIRECT SHEAR APPARATUSHIDEO HANZA¥VAi), N GEL NUTTii), Toivl LUNNEiii), Y. X. TANGl ) and MICHAEL LONG )ABS1'RAC1'A comparati¥'e study of the NGI Direct Simple Shear Test (DSST) and the Mikasa Dir'ect Shear Test (DST) isreported. Samples from Nor¥ve..*aian Drammen clay and Japanese Ariake clay vere subjected to both types of' test. Anevaluation of these test results and a theoretical considel'ation on the different shearing rnechanisms has sho¥vn thatalthough the DST give generally higher stiffness and strength than the DSST, these differences can mainly be accountedfor by the different shearing mechanisms and shearing rates. Sample disturbance due to transportation and handlingmay also be the reason for some of the diftbrence. A technique for evaluation of sample disturbance in the DSST ispresented and evaluated. Tests on undisturbed and remoulded Drammen clay consolidated to stresses much higherthan the in situ effecti¥'e overburden stress give almost identical r'esults. Thus the effects of sample distur'bance and insitu structur'e in the clay ¥vere eradicated.Kev words:direct shear test, direct simple shear test, Iabor'atory tests, sample disturbance, soft clays (IGC:C6/D6)ences in the shearing mechanism; techniques for extrusion, preparation and mounting of the sample; the reconsolidation process; sample dimensions; rate of shearing;the infiuence of remoulding; and testing of overconsoli-INTRODUCTIONLabcu'atory shear testing has become an integral partof many soil investigations for the determination of thestrength parameters of a soil. In Norlvay preference isgiven to the use of the Direct Simple Shear apparatus,¥vhich was developed by Bjerrum and Landva (1966). Forexample the mode of failure in the DSST is similar to thatdated soil. The pr'evious study showed that sampledisturbance was a likely cause of the difference bet¥veenthe sets of results. In this paper a technique for evaluatingsample disturbance in the DSST is pr'esented and evalu-encountered theoretically under the base of offshoreated.gravity structures or in translational type slope stabilityproblems. In Japan, the Improved Direct Shear appara-VALIDITY OF SHEAR TESTINGtus, developed by Mikasa in 1960 and described byTakada (1993), has gained increasing Popularity. TheDirect Sinzp!e Shear Test (DSST)In the direct simple shear t.est conditions of simpleshear strain are imposed to the specirnen, as shown inextensive application of the DSST and DST to bothonshore and offshore investigat.ions warrants a study intothe differences between these two tests. Such a study ispresented in this paper based on a programme of tests onFig. I (a). The verticai normal and horizontal shear forcesduring shear are measured and the shear strain, y*y, isgiven by u/ho for a shear displacement, u, and an initialt¥vo normally consolidated marine clays: Ariake clayfrom Japan and Dr'ammen clay from Norway. Tsuji et al.consolidated specimen height, ho. For simplicity undrained tests are simulated by holding the volume of thespecimen constant. In constant volume shear testing, it isassumed that the change in applied vertical stress as the(1998) have previously reported on tests carried out inJapan on both clays.This previous work is no¥v extended through a ser'ies ofcomparative tests in both apparatuses for the two clays,¥vith ¥vork carried out both in Nor¥vay and in Japan. Thisspecimen height (and hence volume) is maintainedconstant during shear is equal to the excess pore pressurethat ¥vould have been measured in a truly undrained testwith constant total vertical stress. This procedure wasstudy is aimed at identifying any differences in themeasur'ed test results and determining the causes for thesedifferences. Consideration is given to theoretical differj)ii:iiJ, ,used with the introduction of the DSST (Bjerrum andDeceased, formerly Technical Research Unl , Toa Corporalion, ,Japan.Apis Consulting Group, Canberra. Austraiia (formerl ,, Nor vegian Geotechnical Institute, NGI, Oslo, Norway).Nor¥vegian Geotechnical Institute (NGI), Oslo, Nor¥vay.Kanmon Ko¥van Construction Co , Ltd.. Japan (formerly Toa Corporation, Japan)_University C*oiiege Dublin (UC D), Ireland (i¥,iike.Long@'ucd.ie).The manuscript for his paper ¥vas received for revie¥v on August '-9, 2005; approved on July -'6, 2006,¥¥rritten discussions on this paper should be submi ted before September l, '_007 to the Japanese Geotechnicai Society, 4 38-2, Sengoku,Bunkyo-ku, 'Tokyo 1 12-001 l, ,Japan. Upon request the closing date may be extended one month.47 RHANZA¥VA ET AL.48yl cundrained tests are simulated by holding the volume ofthe specimen constant and recordin*' the chan_ :e ine:1!_ __vertical stress.ihf(aj Djrectsimple Sheav(b) Direct shear'The relative displacement, u, of the t¥vo halves of thespecimen is r'ecorded. Often this value is converted toa shear strain, y*.=ul/1, where h is the height of theelement of the specimen which is assumed to be under'*"oing the shear deformation, as pointed out by Wroth(1987). This value is conveniently taken as ho, the initialF g. 1. Conditions of (a) direct simple shear and (b) direct shearLand¥'a, 1966), and ¥vas confirmed in a comprehensivestudy on normally consolidated Drammen clay reportedconsolidated height of the specimen, although such anassumption must be given consideration ¥vhen interpretin*' stiffness par'ameters from direct shear data.The primary criticisms applied to the direct shear testrelate to the non-uniformity of stress and strain through-out the sample (Saada and To¥vnsend, 1981). This occursby Dyvik et al. (1987).Dur'ing shea distortion, the soil experiences a non-the specimen. Stress concentrations occur at the frontuniform shear stress distribution on the top and bottomfaces. For practical purposes, this state of stress isnormally considered close enough to the state of pureand rear edges of the lo¥ver and upper blocks respectively,giving rise to progressive failure alon*' the plane of shearing, so that the full shearing stren>'th of the specimen isshear to justify the inter'pretation of the test as under pur'enot mobilised simultaneously. Takada (1993), ho¥vever,uses photographic evidence from tests on alluvial clay tosho¥v that up to the point of failure, specimen deformations are remarkably uniform, and only at greater strainsdo non-uniformities become increasingly e¥'ident. Pottsshear stress conditions. To justify this assumption, Luckset al. (197,_) performed theoretical linear elastic analysesof the NCJI type DSST, sho¥ving that 700/0 of the samplevas uniformly stressed. Ho¥ve¥'er Saada and Townsend(1981) criticised some of the assumptions used in suc.hanalyses, particularly concerning the amount of fixity atthe boundaries, and cite the results of Wright et al. (1978)who used photo-elastic methods to illustrate a nonuniform specimen stress distribution. Nevertheless,results from tests conducted by Vucetic and L,acasse(1982) in the NGI apparatus on medium stiff clay atdifferent hei tht to diameter ratios have sho vn that thenon-uniformities do not significantly affect the measuredsoil beha¥'iour'. Airey and Wood (1987) per'formed directsimple shear tests on normally consolidated specimens ofkaolln using a specially instrumented apparatus. In thisway the stress strain behaviour of the central core of aspecimen could be determined representin*' that portionwhich most closely experiences a state of pure stress (orideal simple shear). The results ¥vere then compared ¥vithsimilar tests using a standard NGI type DSST ¥vhere onlythe a¥'era*'e stress-strain response throughout the ¥vholeas a result of the ri*･id platens ¥vhich are used to confineet al(1987) used finite element analyses to determine thestress state ¥vithin the rectangular shear box test, andcompare the stress-strain behaviour ¥vith that of idealsimple shear, shown in Fig. 1(a). An elastic-plastic soilmodel ¥¥*as used and the infiuences of volume chan'*e,initiai stress and strain sof'tening were examined. Theseanalyses indicated the propagation of highly stressedzones from the edges of the box, which gro¥vs and rotatesdurmg shear. This type of behaviour confir'med theexperimental rcsults of Morgenstern and Tchalenko(1967) ¥vho used optical examination of samples of kaolinin the direct shear box. Ho¥vever, despite such anomalousbehaviour, Potts et al. (1987) concluded that for the novolume chan*'e condition, the ultimate strength in idealsimple shear is only overestimated by direct shear byabout 60/0. Similarly. , Ioad displacement behaviour wassho¥vn to be consistently stiffer than for ideal simpleshear.specimen can be measured. Airey and Wood (1987)sho¥ved that the values of shear stren9:th and shearmodulus determined from the average stresses underpredict ideal simple shear values by about 100/0.Dil'ect Shear Test (DS T)In the direct shear test, t¥vo halves of a block of soil,rigidly confined, are forced to translate relative to eachother in the horizontal direction, as sho¥vn in Fig. 1(b).The vertical normal and horizontal shear forces appliedto the specimen are measured, and converted to average¥'alues of direct total stress, (T ' and shear stress, r* .These vaiues are then assumed to apply to the forcedplane of shear in the specimen and to be representative ofthe stresses experienced in the localised region ¥¥'herefailure occurs. In a similar procedure to the DSSTTHEORETICAL MECHANISMS OF SHEARAs shown above, evidence suggests that for tests inclay, the DSST underpredicts both the strength and stiffness of ideal simple shear, ¥vhile the DST overpredictsboth the strength and stiffness of ideal simple shear.Differences bet¥veen the DSST and DST can be attributedto different failure mechanisms. In the DST, failure ofthe specimen is forced along the horizontal plane. In theDSST, two possible mechanisms can occur; one oftranslation along a series of horizontal planes, sho¥¥'n inFig. 2(a), or one of translation aion*" vertical planes ¥vithan associated rotation of those planes, as shown inFig. 2(b). In the DSST either mechanism is possible, butan element of soil vill choose that mechanism 1 'hichs DIR照CT SH醸AR、へPPARATUS婆9鴨ξ葦第 びじ ソy陰 07 06 1 ／ 0508』☆1，』二『『『『『006 ノ軒・・2／ジイ篇i／ レ／ 04plusrot∂tion ／l I 〆／ 盤善 ／「 1 1021Q2040 3050∈詳ecヒ匹ve fRctio臼a翻91e p一 （dε9）FiG 3． ’lheo『e“ea鳳 rela重ionshipbetweenund『alned shea『 s｛『enαth DSST and DST （b）（a）σ‘o is the in situ vertica重effective stress，∫くb重s the in situFlg。2。 Possibleね蓋lure mecha臓ism during she食r（a）horizontgl planess芝ressratio，φ〆isthedrainedfrictionangleand（二』εmdC。are the swelling and compression lndlces respectively、 and（b）ver“c田planes Oh重a et a1．（1985）supPort their tkeoly by citing（iatεしfrom Ladd（1973）and Bjerrum（三973）forclays ofv＆r》・ingplastlci書y，includlng the plastic Drammen clay，used inrequires the least resistance，Le。the second one．Thisargument was 倉rst presented by de Josselin de Jong（1972），and taken up by∼Vroth（1984），who、veut on tosuggest that at重he ultimate stage oεa test，after fallure，the element resorts back to the且rst！nechanism．VVroξh｛his study．h圭s interesting to note that the expression forthe DSST（1温ers￡rom that for the DST by the term cQshβimhe dellomlnator．Hence coshβcan be considered＆sa theoretical correction factor bet∼∼ヂeen s封eεしr strengthsdetermined from DST and DSST．Wroth（1984）showscited experimentα玉resu蛋重s fronl Ladcl and Edgers（1972）that，for mosξclays，zi c＆n be well estimated as O．8．Thean（i Bor重n（i973）to confirm this behaviour．The imp正ica−variation of coshβwithφ’forεしrallge of Ko va至ues istlon is that w勤ile the DSST should give lower peakstrength童han the DST，the ultimate strengths should besimilar．presented in Fig．3． It is，however，difacu正t to quantify such（1星fferences iaTESTING PROGRAMMEstrength，because重he standard DSST and DST ap−正）θ5α●iρ1io110ゾ141’iα左θC1αyp＆ratuses（reported ln重his study）do not allow me＆sure− The site of Ari＆ke ls located in Hizen−Kashima，Saganlent of all the normal stresses。Hence it呈s not poss呈ble toPrefecture in Kyushu ls正and，Japan．Extensive use hasbeen ma（ie of the deposit for Ilesearch purposes．Forex＆mple a de重ailed descriptioll of lts mecha且lca1＆nddetermine the Iargest Mo封r’s circle of stress and corre−sponding shear strength．Using e星asto−plastic constitutiveequations， O紅ta et a1． （1985） （ieveloped theoreticalchemical properties is presented by Hanzawa et aLex夢resslons for the normα1ised unclrained strength（1990），Ohtsubo etε毫1．（1995）and Tanaka etεと1．（1996）．（τゼ／σ‘o）ofκo consoli（iεしted clays under P璽ane strain condi−So1ne圭ndex properties of the material used呈n this studytions，for the t、vo test types，as foHows：are shown on Fig．4（Tang et a豆．，1994）。1重is possible todivi（1e the deposit illto t∼vo stratal the upper clay，from O τr（1＋21ζ。）ルf〆 DSST 一； （1） σ〈℃3∬c・shβ重012m（1epth，an（1thelowerclayfrom12to18mdepth． τf（玉÷2κづ）ハ4θ｛■1than 150％near the surface to abouξ120％。TheI畠e玉s aIu the upper clay uatural water content falls fl’om more DST 一； 一 （2） σ〈・。 3∼百where： キ月「η。！1 β富 （3） 2ルノ（4） 1十2Ko Cs14響1一一一 Cc 3−sinφ’tionrαtlo（OCR）ofabout3．5closeξothesurface，（1ecreαsing with（iepth to a value of about1．5，sεθFig．4．（5）The water table is at about O．8m depth．Z）θ5α甲ip∼ioη0ゾ㌧乙）1藺α1η1nθ11C1αッ 6si11φ’ハ4置tively．Forboth strata the natura重wa重er content is greaterthan the liquid limit．Strain conn’oHed oedo1neter tests，reported by Tang et aL（1994），revea圭an overconsolida−3（1一κo）ηo薫corresponding increase in unit weight from aboud25kN／m3ξ013kN／m3．1航he lower clay重he water contentand unit weight are close to100％and14kN／m3respec−（6） The site where Drammen c玉ay samples were obtained islocated about45km south west of Os王o in毛he clty of HANZ,A¥VA ET AL50unit ¥veight of the soil is on avera_ e 16.7 kN/m3 and 19kN/m3 for the plastic and lean clays respectively. Fieldvane test results sho¥v significant scatter but typicallyincrease from about 22 kPa in the plastic clay to 30 kPaWater content(','.) , 't(kN '/Tn3)OO F-*Ho100 12 14OO 10H･-lo}=oh-Hoo ooeoeOeH-loh--HoI*-lo:)c::HHOhHOoOHohHOHHOHhCHOFig. 4. Basic physicaAriake clayO emg oedometer tests, reported by Lunne and Lacasse(1999) and sho¥vn on Fig. 5, indicate an overconsolida-Otion ratio of I .5 in the plastic clay decreasin*' to I .2 in theOHH) ¥v Wn w20OOOOh-Ho15values are lo¥v and typically increase from about 500 kPain the plastic clay to 900 kPa at 25 m.Preconsolidation stresses (pO from incr'emental load-O eh-- oo- 10PH HHThe field vane sensitivity averages7 in the upper clay and 3 belo¥v 10 m. Cone resistanceoeH-IoH-HoC:in the lean clay at 25 mlean clay. Measurements from in situ total stress cells andhydraulic fracture tests as ¥vell as special laboratory testssug:gest Ko Values of about 0.5.o : O R1 2OCR3 4properties and degree of overconsoiidation ofEquipment,for Direct Sill7p!e Sllear Testillg (DSST)These tests ¥vere performed at NCJI using the simpleshear apparatus ¥vhich is described in detail by Bjerrumand Landva (1966). The specimens ¥vere 67 mm in diwater cent nt (o 20o[f':)40 50OFw 'w., {kN/m})ameter (ar'ea of 35.3 cm2) and 16 mm in height, ¥vhich is ai 6 1 8 20height to diameter r'atio of 0.24. The specimen area isr = l1L Oe Qc¥'ertically and in simple shear. At the top and bottom ofi ',, ' )IoThis membrane allolvs the specimen to be defor'medas:kept constant by means of a reinforced r'ubber membrane, ¥vhich provides constraint in the radial direction.the specimen are filter plates. The filters and the draina_ :ef- eee ae a10tubes ¥vere saturated ¥vith water of the same salinity as thepore water in the clay. At the beginning of the test thespecimen is subjected to Ko consolidation stress in steps.Tests can be performed drained or undrained (as has beenaaoo p: stio cl yr- --J:)oTransition zon8Lean 'L r:ai1 5 c! aySrso20 L oao1oeeS20lL L"Jexplained earlier).eQaeooeEquipmellt ,fol' Direct S/7ear Testing (DST)eO 05 OCR1 is 2Fig. 5. Soi] profile at Drammen 'luseum Park/Danvikgnta si eFor this study DST tests were carried out at the TOACorporation in Japan, using Mikasa's Improved DirectShear apparatus. The apparatus is described in detail byTakada (1993). The cylindrical specimens ¥vere 60 mm indiameter and 20 mm in helght, ¥vhich is a hei**ht todiameter ratio of 0.33. The upper shear box is fixed to aDrammen. The site has been used by the Nor¥vegianloading plate ¥vhich is horizontally guided by a set of rigidGeotechnical Institute (NGI) for several earlier researchprogrammes on site investigations including samplin_-piezocone, Iateral stresscone, self-borin_ : pressuremeter,dilatometer, seismic cone, cross-hole seismic and fieldvane testin_g:, see for example L,unne et al. (1976). Anoverview of the ¥vork and a description of the characteristics of the clay are given by Lunne and L,acasse (1999).Several test site were used by NGI over the years but thesamples obtained for this study ¥vere from close to therollers. The lo¥ver shear box surrounds a loading plate ofslightly smaller diameter, fixed to a ¥'ertically guided rigidloading rod, through which the vertical normal load isapplied. Porous stones of rough silicon carbide are usedto transmit the shear force effectively from the loadingplates to the specimen surface. Loading is applied bytranslating the upper box over the fixed lo¥ver box at acity. centre at the lvluseum Park/Dan¥'ikgata site. The soilconstant rate. The apparatus ¥vas desi*･ned in such a ¥vaythat friction bet veen the upper and lo¥ver' shear boxes,bet¥veen the inside of the shear box and the loadin_ : plateprofile and some characteristics of this site are sho¥vn onand tilting of the loading plate could be minimised.Fi**. 5. In the top 5 m, sand and silty sand are encountered. Below this, the marine deposit consists of 5 m-7 mof soft, plastic clay o¥'erlying 35 m of soft to medlumstiff, Iean clay. The plastic clay has a natural ¥vatercontent bet¥veen 500/0 and 550/0, and the plasticity indexaverages 280/0 . The underl .,ing lean clay has ¥vater contentof about 300/0 and plasticity index of 100/0 to 150/0. TheSoi! San7p!il7gUndisturbed sampling of Ariake clay ¥vas performed toa depth of 15 m using a stationary piston sampler. Thesample tubes were made of brass, with a ¥vall thickness of1 .5 mm, an inside diameter of 75 mm and length of I m.On extraction, the undisturbed samples ¥vere carefully rDIRECT SHEAR AP P RATUSsealed ¥vith plastic film and placed in metal boxes.Paraf in 1¥'ax ¥vas used to seal and support the samples inthe boxes. The samples for testing in Nor vay ¥vere sent by5110 minutes immediately follo¥ved by a shear'ing load. Therate of shear under constant volume conditions ¥vas 0.25mm/minute (about 1.'_50/0 shear strain per minute).air freight. Undisturbed sampling of Drammen clay wasFifteen tests ¥vere carried out in thisalso perforrned using a piston sampler. The sample tubes¥vere made of steel, vith a ¥vall thickness of 2.6 mm, aninside diameter of 96 mm and length of I rn. On extraction, the tubes were sealed vith paraffin ¥vax. Thosedepths ranging from 6 m to 19 m.In the second series of TOA tests, the trimmings fromthe samples taken from depths from 6 m to 9 m (i.e.plastic Dramrnen clay) ¥vere remoulded and then consoli-samples f'or testing in Japan ¥vere sent by air freight.dated to a vertical effective stress of ,392 kPa o¥'er oneSalnp!e Prepa/'ationThe procedures used by TOA C*orp. for the DST differsorne¥vhat in preparation and mounting of the samplesfrom those used by NGI for the DSST. In the TOA Corp.method, the extruded sample is tr'immed by a ¥vire sa¥v toa diameter I mm greater than the specified diarneter for'ay on samples fromday, using the NGI procedure. On the follo¥ving day thespecimens ¥vere unloaded correspondin*' to a predetermined OCR. The rate of shearing under constant volumeconditions of 0.1 mm/minute (about 0.50/0 Shear strainper minute) was used. Seven tests ¥vere carried out in thisvay, at laboratory OCR values bet¥veen I and 40.In the third TOA ser'ies of DST tests, undisturbedthe direct shear test A metal ring, 20 mm lon' of exacttest diameter, and ¥vith a cutting edge is pushed do¥vnsamples of plastic Drarnmen clay were used, from depthsgently into the clay. The top and bottom ends of therespectively. The consoliciation procedure and the rate ofshearing ¥vere the same as those described for the secondTOA series of tests.specimen are trirnmed, and the ring is placed on top ofthe upper shear box. A circular disc is then pushed byhand through the ring, thus pressing the specimen intothe shear box.In the NGI method, the extruded sampie is pressed intoa cutting cylinder, mounted on ver'tical guides. Duringthis operation, the excess clay is cut a vay by a ¥vire saw orspatula. Top and bottom filter stones are mounted, andthe specimen is pressed gently into a suction cylinderholding the reinforced rubber membrane. The specimen,of 6m, 7m and 8m at OCR values of 1, 3 and lONo additional DSST tests were performed by NGI onDrarnrnen clay for this programrne. Rather, use wasmade of previous tests performed in Drammen clay for anumber of research projects. A selection of t¥vel¥'e tests¥ 'as gathered from these projects, corresponding to thetests per'for'med by TOA. In six of these tests (on bothplastic and lean Drammen clay) the specimens ¥vereconsolidated to in situ stresses using 4 Ioad steps, oversupported by top and bottom caps and the reinforcedone day, ¥vith shear testing performed on the f'ollo¥vin_"*.membrane sealed by o-rings, is then transferred to thedirect simple shear apparatus.day. Procedures of sample extrusion and preparationTest Procedti/'esplastic Drammen clay ¥vere first consolidated up to amaximum stress of 400 kPa over one day, follo ved byTests ¥vere performed ¥vith both the DSST and the DSTon specimens of upper and lo¥ver Ariake clay, and plasticand lean Drammen clay. For the Ariake ciay NGI carriedout 7 DSST tests and TOA carried out 14 DST tests. Thedivision bet¥veen uppez' and lo¥ver' clay occurs at 12.1 m.Prior to testing, all specimens ¥vere Kb consolidated up to(y(o, the estimated in situ ver'tical stress. This value was¥vere similar. Average str'ain rate varied bet¥¥'een 0.004and 0.080/0 Per minute. In a further six tests specimens ofunloading on the second day to a vertical str'ess corresponding to a predetermined OC*R, ¥vith shear testing onthe third day at a standard strain rate of about O.080/0 Perminute.estimated based on the values of soil unit ¥ 'eightEVALUATION OF SAMPLE DISTURBANCEmeasured for' each test. Consolidation of the NGI specimens was carried out with 4 Ioad steps; each load stepsug :ested that sample disturbance ¥vas a possible cause ofbeing applied for a minirnum of 30 minutes. The fullyloaded specimen ¥vas then left o¥'ernight before shear'ing.A rate of shear of about O. I o/) shear strain per minute ¥vasapplied to the specimens. In comparison, consolidationIn the previous study by Tsuji et al. (1998) it ¥vasthe difference bet¥veen the t¥vo sets of results. Here asimple technique for evaluarion of sample disturbance inthe DSST' is presented and evaluated. The same techniquecan be applied to the DST.of the TOA specimens ¥vas carried out ¥vith one load stepMany techniques are available for the assessment ofo¥'er 10minutes. Shearing ¥¥'as then immediately performed at a r'ate of 0.25 mm/minute (corr'esponding tosample quality. These include X-ray photography,about I .250/0 shear strain per rninute).son of shear ¥va¥'e velocity measured on the specimen ¥vithThe Drammen plastic and lean clays are separated by athin layer of sand/gravel at a depth of about 10 to I I m.TOA carried out three series of DST tests on this clay. Inthe first series, a consolidation procedure was used thatwas the same as that used for the tests on Ariake clay, i.e.undisturbed specimensvere reconsolidated to theirestimated in situ overburden stress, in one load step, formeasurements of initial suction in the sample, comparithat obtained in situ and the assessment of the stress/strain curves and par'arneters measured in oedometer ortriaxial tests (see for example Lunne et al., 1997; Hightet al., 1992).Early ¥vork (e.g. Andresen and Kolstad, 1979) arguedthat the volumetric strain, 8*., induced ¥vhen consolidating a sample back to the best estimate of in situ stresses 1HANZA¥VA ET AL.52'as a useful indicator of sample quality. For a highpiston (composite type'ith plastic inner liner) samplesquality sample 8,, should be close to zero. Lunne et al.(1997) e¥'aluated ¥vhich soil parameters were most systematically influenced by sample disturbance. The conclusion¥vas that the change in pore volume relative to the initialpore volume, Aeleo, is the best parameter t,o use, becauseit is reasonable to assume that a certain change in pore¥'olume ¥vill be increasingly detrimental to the particleskeleton as the initial pore volume decreases. Over theand on hi*･h quality Sherbrooke block samples. Fromlast seven years NGI has used Ae/eo to evaluate sampledisturbance on a number of onshore and offshore consulting projects according to the sample disturbancecriteria given in Table 1. Note for a particular clay¥vhereas the 54 mm composite samples are mostlymultiply Ae/eo by eo /(1 + eo) to get the criterla in terms ofFig. 6(a) it can be seen that the response of the blocksamples is stiffer, the peak shear stress is higher and thestrain to peak is lower than for the 54 mm compositesamples. Values of Ae/eo for these tests are plottedagainst maximum shear stress (ri, max) and strain atfailure (yf) on Fig. 6(b). The block samples fall in the"very good to excellent" or "good to fair" categories,classified as "poor". Peak shear stress r'educes and yfincreases systematically ¥vith increasing Aeleo. Theseresults confirm the applicability of this criterion to thetest results presented here.e+..Previously unpublished DSST results for the very wellcharacterised Ons y clay are sho¥vn on Fig. 6. The Ons ytest site is presently the main soft clay research sitecurrently used by the NGI. Like the Drammen siteTESTS ON ARIAKF. CLAYTest results from the DSST and DST tests on Ariakeclay are shown on Fig. 7. This includes the normalisedextensive research ¥vork has been carried out on the sitesince the late 1960's. It is located about 100 km southeastof Oslo, just north of the city of Fredrikstad. The site isunderlain by ¥'ery uniform soft to firm marine clays of theorder of 40 m in thickness and it is described in detail bystress at failure (rf/(7(o), the strain at failure (y ), thenormalised large strain strength (t,lcr(o) and the rigidityL,unne et al. (2003).parameters are sufficient to evaluate safety factor ofResults are presented for tests on standard 54 mm fixedindex (G50 /rr). Failure in the DSST and the DST has beendefined as the first point at ¥vhich the maximum shearstress is attained. In traditional design shear stren :_thstability. Currently numerical analyses, such as FEM, arebecoming more popular and in these analyses someTable l. Criteria for evaluation of sample disturbance (Lunne et al.,1997)measure of shear stiffness (or rigidity) is needed. Therefore stiffness some stiffness data in the form of G o/r isalso presented here. G50 corresponds to the secant shear1 e /eoO¥*erconsobdarionratio, OCR Very _'.-ood to GoodPoor*to Veryex'cellent* poor*f air1 2< O.04 O.04-0_07 O.07-0. 14 > O 142-4<0.03 O.03-0.05 : O 05O,lO >0.lOThe description refers to the use of the samples tor measurement ofmechanical properties.35from the t vo tests is smaller, especially for the lowerAriake clay. The contribution of severai factors to theobserved differences in stren*"th are no¥v gi¥'en consideration:S4 mm composit--"r35 rSherbrooke b!oek3af**'#25L f"'_ .' ,r"f' *L!ffF;: 20 '20i}r'{ Denotes peakT_i-' '- [ /)r""modulus at 500/0 of the failure stress.It is clear that the peak failure strengths from DSST aresignificantly lower than for the DST. Consistent ¥vith thediscussion above, the difference in large strain stren*'thsl30 -}e* +* *.¥ ¥ky.[I * i '25'' j{iii i!i20ixrl$!'L IS12>l ci158icOO!fr" " ?.55ii{-a; T [ I [ : T i12She r 5tr :in (*.) ((a))o5ii **i[l poor ii*Very good toexce *ntFi('.)i4Good to fairf I If i f I lo o 04 o 06 o 14o 08o 02olOo 2e f eG(b)6. Results of DSST for 54 mm conxposite piston samples and Sherbrooke block samples of Onsey clay: (a) stress-strain curves and (b) assessnlent of sample qualit .'i ;r;DIRECT SHEAR APPARATUSShear strengt ratio :f(' vO S r in to f i[ure, Vf ('/*)oO 02 04 06 08 Oo 3 6 9 12 IS4rge strain strength ratio, r(: 'a 02 a4 a6 08O I i [ l:oo4oeo4QOaF:8812oLi J8e)c1220$P6}2eo'*oe o o ,ler)16P20 -20Aele,differences in Ae/eo bet¥veen the DSST and DST do nota o 04 O 08 O 12 O 16 O 2clearly echo the differences in shear str'ength exhibited inFig. 7. However, variations in the testing procedures ¥villrnask the effect of disturbance: firstly, at similar depthsllboiIIIIIIlIIliI6)11I IIlaolol llll IolI Ariakei ol o I( I Il clayoa ill II ltIIII f¥1 li . I poor I Very poor20o Arlake8Shear strength and stiffness data for DSST and DST tests in Ariake clayI II Il Ariakeolower16acla yol o I I upperle I o I clay:(16 r4aoo) Ariake16204300aO OOe o clayFig. ?.1 OO 200cOe a :owero412 o- QOo Ariake16G !*faeOo o12Rigidity index,uppee oC:!oe a claye o oiayCQoovoOo o Ariakeo upperS53Very good toexcellent Good tofa'rthe consolidation stresses in the DSSThigher. Secondly, the consolidation tinlevere slightlyvas lon*'er; 1/'2to one day for DSST compared to 10 minutes for DST.An aiternative assessment of disturbance is acomparison of the shear strains to failure as plotted inFig. 7. Shear displacement in the DST has been conver'tedto a shear strain, as discussed above. In this plot, a moreconsistent trend is apparent showin*' a slightly higherstrain to failure for the DSST in all but one test.Qualitatively, this could be due to a larger degree ofsample disturbance in the NGI samples, possibly causedby the air frei**ht transportation.Collso!idation TiineThe effect of consolidation time was studied by Berre(1985) who sho¥ved from constant ¥'olume DSS tests inDrammen clay that a consolidation time of 40 minutesresulted in a shear str'ength that ¥vas only I . 50/0 Io¥ver thana similar test performed lvith a consolidation time of 18hours. Ho¥vever, from Fig. 7, the DST tests with theshorter consolidation times are exhibiting higherFig. 8. Assessment of sample qualrty of Ariake clal_ using qualit･.criteria of LunFre et al., 1997SalTlple Disturbancestrengths than the DSST. Hence the effect of differentconsolidation times is considered less significant thanother factors in assessing differences between DSST andDST.Values of Ae/eo during consolidation for DSST andDST are plotted in Fig. 8. For the upper clay, these dataplot mostly in the "ver'y good to excellent" or "good tofair" categories and there is a clear decrease in qualitywith depth. For the lo¥ver clay most of the specimens fallin the "very good to excellent" category and there is littledifference in quality with depth. The TOA specirnens aremarginally better than the NGI samples (average Ae/eo =0.043 compared to 0.046). It is evident however that the-,Rate of TestingHanzawa et al. (1990) investi**ated the effect of strainrate on Ariake clay from Kb consolidated triaxialcompression tests on undisturbed samples. Their resultsare reproduced in Fig. 9. Although the actual strain ratealong the failure plane (¥vhich ¥-vould be comparable tostrain rates in DST and DSST) will be different to thetriaxial results shown in Fig. 9, the effect on the shear !HANZA¥VA ET AL.54Shear strength ratio, T (; vO1O 02 04 06 08 1O l*= O9*o4r08*n_o8-07O OO1+*o.oo O1Strain rat5 (E1!min ):,,cLAriake c]al.'*oo*oo*othe DST (1.250/0/min) was approximately one order ofma*'nitude hi**her than DSST (0.10/0/min), and hence,from Fig. 9, the shear strengths for DST should beu ppercia yodto" IAr'akeel r o*astrength of tests carried out at strain rates of a differentorder of ma*"nitude should be similar. The strain rate forfactored by about 0.88 in the upper clay and 0.86 in thelo¥ver clay to compare with the DSST results. The use oftriaxial strain rates as a measure of rate effects in sheartesting is arguable, and it should be noted that thesecorrection factors are bein*' applied in the absence ofmore appropriate shear test data.[OFig. 9. Effects of strain rate for Ko conso]idated triaxia tests one*acroooAriakeiowercla yDSSTDSTDST Madifted =20Flg 10. ?, ormalised strength from DSST. DST and DST mod fied totake into account strain rate and shearin" mechanism effects forAriake cla¥_'from DST tests should be factored by 0.85 to give T,*, b.Shearing MechanismAs discussed above, O_ hta et al. (1985) present ananalysis ¥vhich can be used to quantify the difference inshear strength bet veen the DST and the DSST. Hanz,a¥vaet al. (1990) sho¥v that Ko for Ariake clay above 12 m is0.54, and belo¥v 12 m is 0.49. Also from Hanzawa et al.(1990) c{**) rs estimated to be approximately 27' and 28'for the upper and lo¥ver clays respectively (tc=triaxialcompression). Hence from Fi**. 3, the DST strengthsshould be factored 0.92 in the upper clay and 0.89 in thelo¥ver clay to compare with the DSST results.Combining the effects of strain rate and the shearingShear 1 fothdusComparison of shear moduli from DSST and DSTdepends, as discussed above, on the conversion of theshear displacement, in the DST to an equivalent shearstrain. Tan*" et al. (1994) argue that photographic resultsfrom a series of direct shear tests, performed by Takada(1993), verifies uniform specimen defor'mations up to rr.Values of G50 repr'esenting the secant shear moduluscalculated at 500/0 of the maximum shear stress, normalised by rr (i.e. G50/rf the rigidity index) are sho¥vn onand compared to the DSST strengths in Fig. lO. Theagreement is greatly improved. Ho¥vever, even theFi**. 7. The t¥vo apparatuses appear to be in good agreement, including the detection of the more rigid behaviourat 15 m depth. The avera*'e value of the rigidity index(excludin*' the test at 15 m) for DSST is 97 ¥vhile for DSTat corresponding depths it is 1 10. This suggests that bothmodified DST strengths are larger than the DSSTare similarly sensitive to the combined effects of r'ate andstrengths. It is concluded that the remaining discrepancyis most likely due to differences in the quality of the soilsamples, although it is also possible that the rate effects¥vere, in fact, Iarger than estimated, or the correctionfactors of the Ohta et al. method ¥ver'e too small.shear mechanism.mechanism, the DST strengths have been muitiplied by afactor of 0.81 in the upper clay and 0.77 in the lo¥ver clayCorrection Used in P/･acticeHanza¥va (199'_) studied the shear strength valuesTF,STS ON DRAMMEN CLAYSpecimells Conso!idated to in Situ StressesA summary of test results from the DST and DSST onspecimens of Drammen clay reconsolidated to in situstresses is shol¥'n on Fig. 1 1. Some¥vhat fe'er' tests werefor mobilised shear stren*･th (r**b) to be applied foravailable from the NGI sources than ¥vere performed byTOA. Nevertheless, a similar procedure of analysis hasbeen adopted as ¥vas discussed above for Ariake clay.example in design of embankments on soft ground. HeFrom Fi**. 11 again it is clear that unmodified DSTconcluded that in order to overcome the combined effectsstrengths are hi**her.obtained from three tests for three different marine clays.His objective vas to determine ho¥v best to obtain a valueof disturbance, shearing rate and anisotropy, results DIRECT SHFAR APPARATUSShear strength ratio. Ttc vO Strain io f i[ure .f ('/.)O 02 04 OJS 08 1 O 3 6 9Oa I f]f]ll fOoCorrected strength ratio2 15oRigidity irldexe vOO 02 04 Oe 08OoJ iGfT100 200300[ 1 1400r8141 vr'4ooe8ooO Piastio) Drarnrnen8F:p*Ooe eP astic8Drammen8l oeoelay44o:elayo' eo6)o,c:12:12e-51 -1212 r' s'l ' 'Lear?Dr mmenoo16elayoo16ooooooo20 ioFig. 11.o,ooO2048E:aaIIi11l04o 36l034l: 032l:DiE:c, 03lQ,l* 028e,'U) 026io 24eP_ o il olI PlasticiotI eo Pl DramrTlenj clayl li ll ll Le nl ll DrarT menlll t oooiayI lo ltI It o GblIo ll ll I o ( lo 2202O ooO1rT 5= 1==20l * l¥Very goad toexce lentlOO1O110iStrain rate ('/*Imin)e DSST results (NGl, 1972)Aver3ge sirai:FieF.oa, po0 very poor(300d toarFig. 12. Assessment of sample quatit) of Drammen clal.' using qualit)criteria of Lu Ine et al., 1997;;; __o ooili6oo 38i12a20'bShear strengt 1 and stiffness data for DSS'I and DST tests in Drammen claO 04 O 08 O 12 O 16 O 2Illil,lr *9oaOOe O*. :e/e,oocia y16e ooeooo20ooLeanDrarnmenr8te for!il DST fesvlts irpfesenstudy13. Effect of strain rate on the DSST shear stren"th ratio ofDrammen clav (N 'Gl, 1972)the two highly disturbed specimens at 18m to 19m).Similarly, the average value of shear strains to failure forDSST is 3.lo/o, and for the DST it is 4.20/0. This sug*'eststhat specimens tested by TOA ¥vere possibly some ¥'hatmore disturbed than those tested by NGI, i,e. theopposite to the finding for Ariake clay. Again this suggests some disturbance was caused during transportationSample Distu/'banceValues of Ae/eo during consolidation for DSST andby air freight.DST are plotted in Fig. 12. For the plastic Drammen clay,these data plot mostly in the "*"ood to fair" category. Aswould be expected the quality of the lower plasticity leanRate of Testingclay specimens are ¥vorse and Ae/eo Values for thismen clay using fast (O. i20/0 /min), medium (0.01 1 o/o /min)material fall in the "poor" category. The avera*･e le/eowhen consolidated to in situ stresses for DSST specimensand slo¥v (0.000360/0 /rnin) rates of strain. The specimensin both plastic and lean Drammen clay is 0.07. In com-stren*'th ratios at failure of these three tests are plotted inparison, the average value for DST is 0.09 (not includingFig. 13 a*'ainst the strain rate on a logar'ithmic scale.In an early study of the DSST, Lucks et al. (1972) performed three direct simple shear tests on plastic Dram-had been consolidated to in situ stresses. The shear *HANZ,A¥VA ET AL56From the figure, it can be seen that the change in stren*'th¥vith the lo*"arithm of strain rate is approximately linear,120ocR = Iof"and hence Fig. 13 can be used to give an approximate rate80correction factor for each test, although this ¥vill in¥'ol¥'ean extrapolation to account for the strain rates used ¥viththe DST series. The shear strengths for both DSST andDST, therefore, have been corrected for a test ¥vith a40;i -e- unstandard strain rate of O. Io/o/min.tLil --} 1m: ido{o254Disp!8eern nt (mm)Shea/' MlechanismKo for both plastic and lean Drammen clay, determined300from labor'ator'y triaxial tests (Berre and Bjerrum, 1973)200is 0.49. Plastic Drammen clay has c '*=25' and for leanDrammen clay c*'.= 26'. Hence using the chart in Fig. 3,the DST strengths have been corrected by a factor of O.871 oethe shear mechanism leads to corrected shear streng:thsas sho¥vn in Fig. 1 1. In this case, the corrected DSSTstrengths lie marginally above those for the DST. Thesmail discrepancy is possibly due to the slightly greaterdisturbance sho¥vn in the DST specimens. On thisrl acp2 s 3in the plastic clay and 0.88 in the lean clay.Combinin the effects of both the rate of testin( _ and+o *:L- i-1 ooo264Displ (;erTlent (mm)Fig. 14. Comparison of DST tests on remoultied and undisturbedspecimens of plastic Drammen clayevidence alone, the conclusion can be dra¥vn that thecauses for the sample disturbance in both the Ariake clayand the Drammen clay may be the result of sample transportation and handlin._,_a (due to air freightin_4ea) as opposedto variations in the sample preparation, mounting andQ2testing techniques.e_Sllear Moduhls- - eeA comparison of the rigidity index, Gso /rf, is also made10plastic and lean clays ¥'aries significantly ¥vith depth,Specinlens Conso!idated to Predete/'inined OCRSThese tests involved both undisturbed and remouldedspecimens of plastic Drammen clay, which ¥vere consolidated to about 400 kPa and then unloaded to predeter'mined OCR values. This value is much higher than the in3c4e3c40;e200150This similarity in results from both the DST and DSSTproperties.20ocR250 otrend is exhibited by both DST and DSST, but a closerall ciays, but ¥vill instead vary depending on the soilDSSTsOOreaching a maximum at about 12 to 15 m depth. Thistests ¥vas also found for Ariake clay (Fig. 7). Ho¥vever itis unlikely that the coincidence of the results ¥vill apply toDST rr:e(!= *eOin Fig. 1 1 , ¥vhere it Is e¥'ident that the rigidity of both theexamination of the differences in rigidity measured by thet¥vo apparatuses is difficult to make without further data.DST -oe1-o,)=ea100oo(50 -aQOO1020OCRFig. 15. Comparison of shear strength ratio at failure and rigidityindex for overconsolidated specimens of plastic Drammen cla)'cussed above. It is concluded that at preconsolidationpressures of 400 kPa any structural effects that may havesitu overburden stress and thus these series of tests are ofbeen present in an undisturbed specimen have beenvalue in deter'minin*' ¥vhether the same correctionsapplied as to the tests on undisturbed specimens consolidated to in situ stresses. A comparison has been made ofremoved. The consequence of this conclusion is that itshould then be reasonable to compare directly the DSSTresults from undisturbed specimens ¥vith DST resultsDST tests on undisturbed and remoulded specimens offrom remoulded specimens.Drammen plastic clay at O_ CR vaiues of 1, 3 and 10, andShear strength ratios at failure for DSST and DST areplotted against OCR in Fi**. 15. It should be noted thatthe tests plots are sho¥vn in Fig. 14. It is clear that there isno consistent difference in the measured stren*"ths or porepressures for the three OCR ¥'alues used. Note that herepore pressure is taken as the change in vertical stressrequired to maintain constant volume, as has been dis-most of the NGI DSST tests ¥vere performed on largerspecimens (50 c.m2 in area, 16mm hei_ :ht) than in theprevious series. Before any corrections due to shearingmechanism or strain rate have been made, the results;1 rDIRECT SHEAR APPARATUSreveal that there is not a significant difference between thet¥vo tests. At lo v OCR values, narnely I and ,-, the DSTgives slightly, higher strengths than the DSST, ho¥vever atOCR ¥'alues of 3 and greater, the DSST sho¥vs slightlyhigher strengths. This change in relative strength occurs5Tof shear strain, some disturbance in the clay samplestested ¥vas apparent. Since this disturbance vas moreevident in the Ariake specimens tested in Nor¥vay andthe Drammen specimens tested in Japan, it is tentatively concluded that the transportation and handlingapproximately at the OCR value when the Drammen claybe*'ins to exhibit negative rather than positive poreof' samples vas the primar'y cause of any such disturb-pressures at failm'e (Fig. 14). The analysis of Ohta et al.(1985) designed for cor'rection for' shearing rnechanism5) A simple sample disturbance assessment criterion,involving the normalised void ratio change (Ae/eo)bet¥veen DST and DSST ¥vas originally intended forrequired to consolidate the sarrrple to in situ stress, isintact OCR = I to 2 clays. It is not clearvhether it appliesto larger OCR cases. Gi¥'en the lack of an alternati¥'e thesame approach as used above (i.e. determination ofance.sho¥vn to lvork ¥vell for the DSST.6) Direct shear tests on undisturbed and remouldedspecimens that had first been consolidated up to1 /cosh fi using Eqs. (3) to (6) and Fig. 3) ¥vill be appliedstresses of 400 kPa resulted in stress strain plots andfor illustrative purposes. Furthermore in the absence ofreliable data, the correction for rate effects discussedstrengths that were almost identical. Hence, it isabove lvill also be applied. This correction corresponds toconcluded that after experiencing such high stresses,the efi cts of sample disturbance and in situ structuredifferences in rate of shear of about half an order ofmagnitude, Ieading to a correction factor of 0.93. Thein the clay ¥vere eradicated. Comparisons betweenundisturbed direct simple shear tests and remouldedmodified DST strengths are also plotted in Fig. 15. It candirect shear testsvere therefore considered valid.be seen that the DST and DSST strengths match ¥vell atOCR of i, but otherwise the DSST stren*'ths are somewhat higher.Values of rigidity index G50/Tf for the range of OCR7) After rnaking corrections for diff:erences in thevalues tested ar'e also shown in Fig. 15. Despite a consis-in fact, corresponded approximately to the OCRtent dift rence in stifihess between DST and DSST,values where pore pressures at failure became negative), the DSST gave some¥vhat greater stren_g:ths.Variations in stiffness for the range of OCR valuesprobably due to the fundamental difference in the shearing mechanisms, the variation in stiffness ¥vith OCR isremarkably similar for the two tests.Cor TCLUSIONSThe comparative study into the differences bet¥veen theDST' and the DSST has revealed the follo ving conclusions:1) For clays consolidated to in situ stresses, the directshear test (DST) gives higher estimates of strengthand stifihess than the direct simple shear test (DSST).The difi rence bet¥veen the tests can be accounted forby the different shearing mechanism imposed toshearing: mechanism and rate effects in the DST andDSST, shear strengths were similar for OCR valuesof I and 2. For OCR values of 3 and greater (¥1'hich,tested ¥vere remarkably similar.8) It should be noted that the modif'ying factorspresented here, 'hich are used for DSST/DSTcomparative purposes, are not necessarily applicableto pr'actical strength determination in Japan. In theauthor's experience, and as detailed in Hanza¥va(1992), DST shear strengths are actuaily used indesign by multiplying by an overall correction factorof 0.85.REFEREN_ CESspecimens, the difi r'ent rates of strain used, andpossibly sorne contribution due to different degreesl) Airev. D. ¥¥t. and ¥¥*ood, D .¥e. (1987): An evaiuation of direclsimpie shear tes s on clay, Ceorechnique, 37 (i), 25-35'_) Andresen. A and Kolstad, P (1979): The NGI 54 mm samplers forof distur'bance in the clay samples tested in Japan andundisturbed sampling of clays and representative sampling ofNor¥vay.2) The different shearing mechanism bet veen the DSTand DSST can be quantified by adopting an analysisproposed by Ohta et al. (1985) formulated for Kbconsolidated clays under plane strain conditionscoarse material, Proc. Int. S_1'inp.. Singapore, 13-'_1. Also in NGJusing elasto-plastic constitutive equations.3) The eft ct of performing tests at different rates ofstrain is difficult to compare accurately when assessing the DST. This is because there r'emains uncertainty in conver'ting shear displacement to shear strain.Nevertheless, in Ariake clay, corrections based upontriaxial strain rates result in an improved agreementbetween DST and DSST strengths.4) Evidence f'rom the tests in Ariake and Drammen claysuggests that, after making appropriate correctionsfor the shearing mechanism and differences in ratesPub!ication No. 130.3) Berre, T. and Bjerrum, L. (1973): Shear strength of normallyconsolidated clays, Proc. 8th ICS_iVIFE, i¥,losco¥v, 1.1, 3940.4) Berre, T. (1985): Eff ct of consoiidation time on triaxial and directsimple shear tests, JVGI Intenla! Report. No. 56103-29_5) Bjerrum. L, and Landva, A. (1966): Direct simple shear tests on aNor vegian quick clay. Geotechnique, 16 (1), l'_)O.6) Bjerrum, L (1973): Problems of soil mechanics and constructionon soft clay, Proc. 8tll ICS_,VFL', ivlosco¥v, 3, 109l59.7) Borin, D_ L. (1973): The beha¥'iour of saturated kaolin in the simpleshear apparatus, PllD Thesis, University of Cambridge8) de Josselin de Jong. G. (197'_)): Discussion. Proc. Roscoe -'Venloria!S_v,np. Stress-Strain Behaviour of Soi!s, Cambrid**e, '-58261 _9) Dy¥'ik, R., Berre, T , Lacasse, S. and Raadim. B. (1987): Compari-son of truly vndrained and constant volume direct simple sheartests, Geo!ec'hnique, 37 (1), 3-lO.lO) Hanza¥va. H.. Fukaya, T. and Suzuki, K. (1990): Evaluation ofengineering properties for an Ariake clay, Soi!s and FbLindations, 58HANZ、AWA ET AL、 30（4），玉1−24． 613−6王6．11）Hanzawa，賛．（1992〉＝Anewapproac厭odetermlnesoilparameters22） Ohtsubo，i〉L，狂gas簸玉ra，K。a【1d Kas｝1玉ma，K．（1995）＝Depos辻玉onai free from regio鷺al varia亘ons in so涯 behaviour and 【ec自nical a職d posトdeposi“onal geoc簸em玉slry，and 玉ts correlat1on 、、・ith the quality，So’Z∫αη4Fα〃1ゴ副o’∼5，32（1），7レ84． geotechn藍cal properties of marl鷺e clay 玉n Ar玉ake bay， ，lapan，12）封lght，D W．，Boese，R、，Buτc蝕er，A．P．，qayton，C．R、至．and Sm紅血，P．R．（1992）：DisturbanceoftめeBo“1kennarclaypriorto 0θo∫θchη’（1ε’θ，45（3），509−523． laboratory testing，（フθo∫θ（｝h1∼1（1∼’θ，42（2），圭99−217． ele磁e窺a鷲alysisof由edirect5員earbox【esτ，Gθo’θchηゆθ，37（1），13）Ladd，C．C、a“d狂dgers，L、（1972）＝CQRsolidatedundra鎗eddlrect simples鼓eartestsonsatし王ratedclays，M／7Rθ5θσκhRθpor’， R72−82、 王1−23，14）Ladd，C C、（1973）：Dlscussion，mai糞session，8∼h／（フS1》E万， 740，7−77． Moscow，4，108−115，15）Lucks，A．S，Christian，J．τ、，Brandow，G．E aΩd Hoeg，K23）Potts，D．M，，Doun茎as，G、T．a簸d Vaughan，P．R．（1987）：F鮫玉te24〉Saada，A，S．a賞d Townsend，F、C．（1981）＝State of the art： Iaboratorys【rengthtestlngofsoils，．4S7MSρθc．τθ‘h．Pゆ1．，No、25） Takada，N。（1993）：！〉likasa’s direct s員ear appara1us，test pro（：edures and resu置亡s，（｝（ヲo’θ（ン11． 71θ5f．／．，16（3），3茎4−322． （王972）＝S【ress cond虻ions重n NGI simpie shear test，1’∼∼．Co’∼∫．So’126）Tanaka，｝｛．，S｝玉arma，P．，Tsuchida，T、and Tanaka，NI．（1996〉： Mec1；．FoHηゴ。0’v、，ASCE，98（SM1），155一玉60、 Comparat隻vestudyonsamplequahtyusingseveraldl琵ere瓢types16）Lunne，T．，Eide，0．anddeRulter，」，（1976）：Correlat1onsbetween of samplers，So’Z∫σ1∼ゴFα“1面∫’0115，36（2），67−68． cone reslsIance and vane s晦ear strength1n some Scand1nav茎an soft27）Tang，Y．X．，Hanzawa，H，andYasuhara，K。（1994）＝Dlrectshear tomediumclays，Cαη．Gθorθch．／．，13（4），430−44玉， and direct s王mple shear test resuks on a Japanese marine day，1S−17）Lu孤e，T．，Berre，τ。a職d S［randvik，S．（1997）：Sample dlsIurbance Hoκたα’ゴo’94． e餌eαs玉n sof110w plast玉c Nor∼、7eg玉an clay，Pro‘．R8ご8’π1）θveloメ？一28）■suji，K，，Tang，Y．X．andL犠nne，丁．（1998）＝Acomparatives【udy ’ηθノ∼’5’η50”‘7ηゴPovθ1刀θn∫ル1θご11αn’c5，Brazi1，June，8レ102． onshearstre篇gthofmar1neclaysbydirectsllearandd量rectslmple18）L凱ne，τ．andLacasse，S．（玉999）：GeotechnlcalcharacterisIlcsof s簸eauest，，∫．Geo鷹11．Eη9喀，JSCE，589（III−42），275−285（iR low plas重圭city Drammen c蓋ay， Chα1ηcrθπ∫σ”011 0ゾ「Soゾ1’ 1》α’’”1θ Japal｝ese）． αのン5（eds．byTsucぬidaandNakase），Balkema，Rotterdam，33づ6．29） Vuce百c，1〉L a盤d Lacasse，S．（1982）：Spec1men size effeα玉a simple19）Lunne，τ．，Lon9，M．and罫orsberg，C、F．（2003）：Character1satlo鷺 sllearIest，1ηr．Gθ01θc11．E119，ρ’v．！13Cど，108（GT12），1567一玉585． and eng1neering ProperIies of Onsのy cIay，ノニ》ヂoc．1n∼、rIzo∼κ5hoρon30）Wrig壌，D．K．，Glibert，P、A．and Saada，A、S（1978）：Shear Chθ’「βαθ”なα’io〃 01∼ゴだπgi11θθ1”〃7g Pro∫7θ∼’1θ5 0ゾNα11〃門α1So’Z∫ devlces for determlning dynamlc soil properties，P’Poぐ．Sρθc．Co’4． r？〉α’置〃wl So〃52002，ワ（eds．by Ta鷺，丁．S．et aL），NUS S1ngapore， だσπ1∼（∼μακθEη9’ηθθパ179α’1ご50’1Z）Lγ∼101η’c∫，ASCE，Pasadena，2， December．Pubhs致edbyBalkema，1，395−428．20〉Morgensξem，N．R．and Tc負alenko，1．S．（1967）：Mlcroscoplc 1056−1075， strucIures呈n kaolin subjected to direct s鼓ear，（二7θo∼εch∼∼’（1∼∼θ，17（4）， Rankine Lecture，0θo∼θchη’‘7μθ，34（4），449−489．3烹）Wro由，C．P．（1984）：The1nterpretat1onoflns1tusoihests，2紬 309−328，32）Wro由，C．P．（1987）：丁鼓e be瓦aviour of normally consolidaIed cla｝・2玉） Ohta，H．，N1s益貸ユara，A．and r〉lor疑a，Y．（1985）：Undra呈員ed stab玉1iζy as observed1鷺undra玉ned direct shear tests，Gθo’（アご11η’（1∼’θラ37（1）， ofκo consohda【ed cla》βs，」D∼oご． 11’1∼1CSA4Fだ，San Francisco，2， 37−43、甕 | ||||
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| タイトル | Induced Swelling of Kaolinitic Soil in Alkali Solution | ||||
| 著者 | P. V. Sivapullaiah・Manju | ||||
| 出版 | soils and Foundations | ||||
| ページ | 59〜66 | 発行 | 2007/02/15 | 文書ID | 20980 |
| 内容 | 表示 rSOILS AN. D FOUNDATIONSVol47, Nol, 59-66, Feb. 2007,Japanese Geotechnical SocietyINDUCED SWELLlNG OF KAOLINITIC SOIL IN ALKALI SOLUTIONP. V. Sl¥'APULLAIAHi) and MAN'JUii)ABSTRACTUnexpected s¥velling induced in foundation soils can cause distress to structures founded on them. In this paper, thes velling of kaolinitic soils due to interact.ion ¥vith alkali solution has been reported. The induced swelling is attributedto the formation of new minerals, ¥vhich has been confirmed by X-r'ay diffraction patters and SEM studies. Tounderstand the effect of alkali concentration and duration of interaction, two series of consolidation experiments havebeen carried out. In series I , the specimen were r'emoulded ¥vith ¥vater and inundated ¥vith alkali solutions and in series'_, the specimen ¥vere remoulded and inundated ¥'ith same alkali solutions. A steep compression during loading cycleand no abnormal swelling during unloading cycle has been noticed for the specimen remoulded ¥vith water andinundated ¥vith I N NaOH solutions. The steep compression is due to the segregation or break down of clay mineralsdue to alkali interactions. In case of specimen inundated ¥vith 4 N NaOH solutions, abnor'rnal swelling has beenobserved durin*' unloading cycle of the consolidation test. Ne¥v minerals are for'med on interaction of soil ¥vith 4 Nsolution as confirmed by X-ray diffraction patterns. These minerals are kno¥vn to have very fine pores and possess high¥vater holding capacity. The differences in the amount of s velling of samples remoulded ¥vith vater and r'emoulded¥vith alkali solution are due to variations in the concentration of alkali and duration of interaction.Key words: alkali, consolidation, kaolinite, mineralogy, swelling, zeolite (IGC: BIO/D2/D,3/D5)industries such as i) Paint and dyes ii) Paper and pulpindustries iii) Cotton mills iv) Aluminium industries andso on. From an engineering point of vie v, understandingof the mechanism of heave is essential if distress due toIN1'RODUCTIONThe soils in the bases of buildings and struct.ur'es ofindustrial plants, dams, and dikes of industrial se¥vagedifferential s¥velling/settlement has to control.collecting canals are frequently subjected to the action ofdifferent solutions of salts, acids, and alkalis, as a resultof ¥vhich their composition, physico-chemical properties,Numerous researchers have explored that kaolin clayinteraction with alkali solutions leads to the formation ofzeolit.e (Aznar and La lglesia, 1985; Madani et al., 1990;and geotechnical behaviour under*'oes significantchanges. Unexpected volume chan*'es occurring inRocha and Klinowski, 1991; Gualtieri et al., 1997;on thern. Depending on the composition and propertiesAkokelar et al., 1997; Demortier et al., 1999). Zeolitesare hydrated aluminosilicates 1 'ith symmetrically stackedof the soils and of the solutions penetrating into them,alumina and silica t.etrahedral, with open and stable threethe soil may swell or settle.dimensional honeycomb structures ¥vith a negativefoundation soil can cause distress to structures foundedThe volume changes caused by applied stresses andcharge, neutralized by ions such as sodium. The phys-moisture changes, ¥vhich are very significant for soilscontaining expansive minerals, are less important foricochemical conditions under ¥vhich zeolites are obtainedfrom kaolin are ver'y similar to those used in geopolymerization. Geopolymer is the name that has beensoils containing non-s¥velling clay minerals such askaolinite. Ho¥vever, the volume changes in these soilsapplied to a ¥vide range of alkaline or alkali-silicateactivated aluminosilicate binders . The geopolymeric bind-due to chan*'e in chemical environment may becomeer phase is often described as "X-ray amorphous".important. It is kno¥¥'n that the non-slvelling soils canexhibit higher s¥velling in fluids ¥vith low dielectricHowever, many authors have noted formation of phasesdescribed as either semicrystalline or polycrystalline(Palomo et al., 1999; Van Jaarsveld et al., 2002; Rowlesand O'Connor, 2003) in geopolymer. Provis et al. (2005)constant such as carbon tetra chloride (Sridharan andRao, 1973; Chen et al., 2000). Rao and Rao (1994),Sinha et al. (2003), and Sivapullaiah et al. (2004) havereported the swelling of kaolinite rich red soil due tointeraction ¥vith caustic soda. Contamination of foundation soil with alkali solutions can occur froui varioushave reported that *･eopolymers actually containnanocrystalline zeolites. Hence the difference bet¥veengeopolymers and zeolites is rather small." Associate Prof ssor, Departmem of C*ivil Engineering, Indian Institute of Science, india (siva@civiLiisc,ernc ,in).**Research Student, dittoThe manuscript for this paper ¥vas received for revie v on September 17, ,_005; approved on September 5, 2006.Written discussions on this paper shou d be subrnitted befbre September 1, 2007 to he iapanese Geotechnical Society, 4 38*2, Sengoku,Bunkyo-ku, Tokyo I 12-001 1, Japan. Upon reques the closing date may be extended one month_59 I 1SIVAPULLAIAH AND60,lANJUTable '-. Chemical composition and cation exchange capacrt¥.' of theTable 1. Ph)'sical propert¥.' of ti]e soilssoilsPro pertySpecific gravit¥.-Red earth soil Kao]inite2 67Clremicai composition (O/･)Atterberg's limitsLiquid limit (LL), '/-38Plastic limit (PL), ollo19Non-plasticPlasticit .' index (PI), o/o19Non-plasticShrinkage limit (SL), 9'-55036Slvell bet]aviourFree slvell index, g/ccl .214Grain size distributionSilica (SiO.) 62.358^05Ferric (Fel03) 2.61Titanium (TiO.) O 21Potassium (K.O) O_42Sodiurn(Na20) O.32*Magnesiurn (N'IgO) I .67Alumina (Al.O )7 )15Silt content, 75 ;!m-2 um (ollO)4464Fine sand content, O,,_7 mm-75 !!m ( /e) 3421CL49 7041 .80Calcium (CaO) 5 91Loss on ignitian S.41O .30l .OOO.40O_30O OOO.057.40Cation exchange capacity, (meq/lOO g)TotaExchan**eable ionsClay contem, <7-,!m (0/6)Unified soil classificationRed earth KaoliniteParametcr,-,55I O . 84Sodium,82Potassium,NaK OO.38Caicium, Ca 6^86Magnesium, ivlg I .783 ,, 700.40o_502.00o.80CLverted other primary minerals into clays oxides. TheStandard proctor's parametersMax dry unit ¥veight, (kN/ms)17.813 5Optimum ¥ 'ater content, o,fo1828Singh and Kolay (2002) ha¥'e reported the effect ofz,eolitization on the engineering properties of fly ash^Sivapullaiah and Manju (2005) have studied the effect ofzeolitization on the basic properties of kaolinitic soils.Ho¥vever, the eff ct of z,eolitization on the engineerin aproper'ties of kaolinitic soil is not been studied so far.Invesngatron has been carried out to understand theextent of volume change in kaolinitic soils under theactlon of high concentrated sodium hydroxide alkalisohrtions. Understanding the mechanism of changes isnecessary to su_g_gest remedial measures to overcome thedistress caused to structures founded on these soils.physical properties of the soil used are reported in Tablel . Silica, alumina, iron and other chemical constituents inthe soils ¥¥*ere analyzed according to standard methods(Hillerbrand and Lundel, i953). The r'esults have beenpresented in Table 2 and ar'e based on the oven-dried¥veight of the soil at 105'C. The cation exchange capacityof the soils ¥vas determined as per' Jackson (1958), alon_g:vith the type of cations, are reported in Table 2.F!uic!s UsedChemically pure sodium hydroxide pellets ¥vas obtained from Glaxo L,aboratory, India. The fluids used¥vere 1) Distilled water, 2) i N Sodium Hydroxide and 3)4 N Sodium Hydroxide. Concentrations of sodiumhydroxide that many industrial processes use are near 4N. Aluminum extraction plant (Whittington and Cardile,1996) and nuclear ¥veapons industry (Qafoku et al. , 2004)are using approximately 4 N sodium hydroxide solutionMATERIAl,S A_ND MF,THODSSoi! UsedA natural soil, red earth and commercially avaiiablepure kaolinite were used. The red soil used in the study¥vas collected around the soil mechanics iaboratory,Indian Institute of Science, Bangalore, India. The soil¥vas collected by open excavation, from a depth of onefor their different process. When there is any leakage atthese industrial sites, soils at closer surrounding becomecontaminated with a high concentrated sodium hydroxidesolution. And considering the field condition, the contaminants become diluted due to the seepage of surfacemeter to natural ground ievel. The soil ¥vas air dried andwater and rain¥vater into the soil. And hence to study thedifferent concentration effect, I N and 4 N concentratedsolutions have been considered seeing the possible level ofalkaii in the actual site. Sodium hydroxide solution wasused after sievin9: throug:h Indian Standard 4･_5-micronprepared by dissolvin*' the required amount of Analarsieve. The grain size distribution of red earth, andGFade sodium hydroxide pellets in distilled ¥vater.kaolinite has been carried out as per Unified classificationsystem and are presented in Table 1. X-ray diffraction ofboth the soils has sho¥vn peaks at 7.,_ A, 3.6 A and 1.49A, which are diagnostic of the twolayered kaolinitemineral. The major minerals present in red ear'th,ho¥ve¥'er', is quartz and sho¥ved stron*" peaks at 3.36 Aand 4.,_8 A. It is not surprising that quartz is present asthey are the most ¥veathering-resistant primary minerals(Dixon and Weed, 1989) and tropical ¥veathering has con-M:ethoclsX-Ray Diffraction AnalysisRandomly oriented samples ¥vere prepared by manualgrinding in a porcelain mortar and pestle to powder formand subsequently pressing the material lightly into r'ectan-( -ular _ lass holders. Samples were scanned from 3'2e to80'26 using Philips X-Ray diffractometer model P¥V3710i, ri'".INDUCED S¥¥,ELLING OF KAOLINITIC SOILemploying CuK.,, radiation and using 0.04' steps andle- I Red esrlh + ¥ ater I" W terI"I Retl carih + WaSer lrN nOHcounting for at least 0.4 slstep. The mineral compositionh-ir¥¥'*' REtl esrth + IY; er "' 4 N "Iof each sample ¥vas deter'mined using the XRD peakpositions and intensities (JCPDF, 1990).61O l,i*Scanning Electron Microscopy (SEM) StudiesA Cambridge S360 Scanning Electron MicroscopeL -(SEM) interfaced ¥vith a Polaroid camera and an EDAXX-ray analysis system ¥vas employed for characterizingJhand examining the untreated and treated soil and reactionproducts. A very small amount of oven-dried and finelypolvdered sample is mounted on to the tape glued to thefiat surface of SEM stub and sputter coated with goldprior to scanning (White and Dixon, 1995). The terminology used to describe the micrograph has been noted fromSmart and Keith (1981).Free S¥vell IndexThe free swell is the sediment volume per gram of soilin water and is determined using the method of Rao andSridharan (1985).OneDimensional Consolidation TestsIn order to obtain the effect of ingress of alkali solutioninto the soil, experiments were desi**ned to be conductedin different series. Two series of experirnents ¥vere done tobring: out the effect of concentration and duration ofInteraction with alkali solution on the consolidationbehaviour. Soil was statically compacted to the maximumdry density and optimum moisture content of uncontaminated soils as determined from Standard Proctor's test.The maximum dry density and optimum moisture*9iO Con50lid2!ion Prt sure l 0( kPa ,lOO{lFio. l. Volume chanoe be laviour of red earth remoulded with waterand inundated lvith alkali solutionsof 24 hours or until prirnary consolidation ¥vas completed¥¥'as adopted. The samples ¥¥'ere loaded up to a pressure of800 kPa and unloaded to 6.25 kPa.Conventionally, the consolidation test data arerepr'esented by void rati0-10g pressure relationship. Sincethe specific gravity of the materiais might have changed,the data are represented by vertical strainagainst vertical consolidation stress in this paper.Vertical strain 8 is calculated as follo¥vs.Vertical strain 8 = zllllHoWhere: Ah = Ho-HiH0=initial height of the specimen.Hi = height of the specimen at any loadin*' interval.After completion of the above tests, the soil samples wereremoved and oven-dried. The samples ¥vere po¥vdered andthe X-Ray diffraction and SEM studies were conducted.content are 17.8 kN/m3 and 180/0 for red earth; and 13.5kN/m3 maximum dry density and ,-80/0 optimummoisture content for kaolinite. In series 1, the soils ¥vereRESULTS AND DISCUSSIONSmixed ¥vith ¥vater at respective Proctor's optimum watercontent and kept for equilibrium for 2 days. Later soilearth samples compacted ¥vith ¥vater (series 1) and com-samples were statically cornpacted into consolidationpact.ed ¥vith alkali solutions (series 2) has been presentedrin*'s to Proctor's maximurn dry density. The inundatin_"_.fluids ¥vere I N and 4 N sodium hydroxide solutions. Thisseries ¥vas designed to bring out the effect during contami-and the mechanism of the effect of alkali has beendeduced from detailed X-ray diffraction and scanningnation. The sample preparation for ser'ies 2 experimentsis the same as the previous case except that the samplesvere mixed ¥vith the I N or 4 N alkali solutions and keptfor equilibration for one ¥veek before inundating with thesame alkali solutions. This se 'ies ¥vas designed to brin-'out the effect of continued contamination. For compari-son, the consolidation tests on soils compacted andThe volume change behaviour of kaolinite and redelectron microscope studies.Series I-Effect oJ' Alka!i So!utions on Vo!ulne ChangeBehaviour of Samples Colnpacted with WaterFigures I and 2 sho¥v the plot of vertical strain 8 a*'ainstvertical consolidation stress for the compacted red earthsoil and kaolinite ¥vith ¥vater respectively and inundated¥vith ¥vater, I N and 4 N NaOH solutions. Both r'ed earthinundated ¥vith ¥vater were also conducted. Repetition ofthe oedometer tests ¥vith identically prepared specimensgave consistent data.Remoulded samples after' equilibration was staticallyand kaolinite specimen inundated ¥vith I N NaOHcompacted to the Proctor's maximum dry density in a 60mm diameter and 20 mrn high consolidation ring, to aabnormal s¥vell (rebound) during unloading. Thethickness of 14mm. The ring ¥vas then mounted in aunloading in case of red earth soil. It has even crossed itsconsolidation cell and positioned in the loading frame. Atinitial height. Kaolinite specimen inundated ¥vith 4 Na nominal pressure of 6.25 kPa, the sample ¥ 'as inundated with the required fluid. In all the experiments, aNaOH solution also exhibited higher swell duringload increment'atio of one with load increment durationexhibited steeper compression than specimen inundated¥vith ¥vater or 4 N NaOH solution. Ho¥vever', the red soilspecimen inundated ¥vith 4 N NaOH solution exhibitedcompression strain has been completely recovered uponrebound than specimen inundated ¥vith ¥vater and I NNaOH solution but the compression strain has not been j,SIVAPULLAIAH AND i¥,iANJU62compression during loadin." cycle in any pressure rangeunlike the specimens compacted with ¥vater and inundat-,2 loed with I N NaOH solutions. Red earth soil remouldedand inundated ¥vith 4 N NaOH sho¥ved steeper compression during loading as ¥vell as steeper rebound duringunloading as compared to the soil remoulded and inun-l,:!i"11"dated ¥vith water (Fig. 3). It is to be remembered that inthis series, after mixing with contaminant, the sample hasbeen cured for one week before starting the consolidationtest. Durin** the time between mixing and staring the test,silica ¥vould have leached out from kaolinite due to the' -io [K olinitt - 11 ster t I .Isr- 2 *l- KaoTinite - IY,rrI N Ih;sOr hso F,ite-Wster + 4 " ¥.OHIs-[e 1IOtConsolitistion Pressur?(kP2)ooOo{)Fig. 2. Vo]ume cbange behaviour of kaolinite remoulded lvith lvaterand in ndated ,vith a]kaii solutionspresence of 4 N NaOH solutions. And hence, strength ofthe soil would decrease. Thus, more compression hasoccurred in this series compared to soil remoulded withwater and inundated with 4 N NaOH solutions. Whenkaolinite is remoulded and inundated ¥vith 4 N NaOH,compression is same as kaolinite remoulded and inundat-3,led ¥vith water. Ho¥vever, it has also sho¥vn a steeprebound during unloading. The compression strain hasbeen fully recovered during unloading in case of.[kaolinite. The swelling during unloading in case of redearth appears to be less in this series as compared to soil*3remoulded ¥vith ¥vater and inundated with 4 N NaOH>(Fi**. 3). But unlike red earth sample, in case of kaoliniteRed earth + WH,er - Wster* 4-Red esrthJ X. N. Or +A Red esrth*XaOIswelling durin*' unloading appears to be more in thisN.'aOH- 4 ,,. ,,.OH-9lOFig.Conselida tion Prs5surc(kP2}c(icOo3. Volume chanoe behaviour of red earth remou ded and inun*dated lvith a]ka i so]urioTlsseries as compared to kaolinite remoulded ¥vith ¥vater andinundated with 4 N NaOH (Fig. 4). This difference in thebehaviour of red earth and kaolinite could be due to thedifference in cry. stal structure of kaolinite minerals. Inkaolinite the particles are strongly bonded by hydrogenbond than in red earth (the hydro*'en bonding disruptedby presence of non kaolinite particles) and due to hi**heramount of kaolinite, reaction is taking place at slo¥verrate than that of natural red earth soil.,J-1It is reasonable to conclude at this sta*"e that the overallcompressibility (especially s¥velling during unloading) ofsoil/kaolinite is quite different from the untreat.ed redl4*so- '-1Fiso･ Xs(,- i ,, ,,l0 f - I ,,A h:a{, n-4,,:¥ O -{:¥OFOH-16o CQoti s,ion Pr s;ure(kPa)os!ooeFlg 4. Volumccl]ano*ebehaviourofkaoliniteremoulded and inundated lvith alkali solutionsfully recovered during unloading as in the case of redearth soil.earth/kaolinite. To understand this unusual behaviour,the knowledge of the particle-level interactions at themicroscopic level is needed. Thus, to understand thechanges in soil structure and composition of soil due toalkali interactions, X-ray diffraction patterns and Scanning electron microscopic examination of soil particles¥vere obtained on soil samples after consolidation tests.XRD Studies on Red EartlllKao!i,1ite Sa/7lp!es afterCollso!idation TestsTo understand the extent of changes in the soil miner-alogy after consolidated tests, the X-ray diffraction(XRD) patterns ¥vere analy2:ed. Figures 5 and 6 sho¥v theXRD patterns of consolidated samples of red earth andSeries 2-Effect of A !kali Sohrtiolls on Vohlrne Changekaolinite respectively. Untreated samples of red earth andBehaviour of Samples Compacted with A!ka!i Solutionkaolinite sho¥v the peaks mainly due to kaolinite c.layFi**ures 3 and 4 sho¥v the plot of vertical strain 8 a*･ainstminerals. In red earth, kaolinite mineral peaks are of less¥'ertical consolidation stress for red earth and kaolinitespecimen respectively when compacted and inundated¥vith I N and 4 N NaOH solutions in the consolidationcell. Both red earth soil and kaolinite remoulded andinundated ¥vith I N NaOH solutlons exhibited no steepintensity and quartz sho¥vs maximum peak intensity.Change in concentration of alkali used for inundationhas shown significant variations in XRD patterns. In thesamples inundated ¥vith I N NaOH solution during consolidation testing, the intensities of peaks due to kaolinitek:; INDUCED S¥¥,ELLING OF KAOLINITIC SOILr :: Red earth +4N N aoH +4::' ijl - ':;'2:I, !.;z'< ;r!o.: ; QL ' r-- d !*J'vY-'e'I. )' !'y'l*.LJ' ,iNaoHl*.,*.Jt. r:: Red earth +'flQ1i=rYater + 4 N NaoH$rfle;': . < 'vz-i-f-/1J-_.tl_)1/-': -Y,I_irj,-/ *_!" J'-Red earth +1 N NaoHI N NaoHI ;,; '= I!h,' ;*) '- l'r¥'--'Y=" j -'- '! *4J JLlvi_.YY!QRed ear;h +¥Yater + I N' Nao iI' JL_/ JII i ' _ i:J"J__ _ti ;Q Kii;f .h_Jl -._JY,f' . ! J_ ' _J._J ''-tion test: Q=quartz, K=kaolinite, N TASH=sodium altunirwm[ :[< '-II "' Kaolinite + 4N NaoH + 4N NaoH!1' '<'i il 'I':' UJll! " '1""IvlL"I "'e :IT 1 t'jr'vJ¥Jlrjlt !LhfJ '"' :Y v ' I 'r/1'¥-Y"' rvrjh/"I-" t"J:;r l t;1'Y/'YT iL" " L Kaoiinite + ¥¥rater+4N NaOH"I' 1'; i i {:1 '1' l"'!iremoulded ¥vith ¥vater and inundated with I N NaOHremoulded and inundated ¥vith I N NaOH solution didthe literature.Sample rernoulded and inundated with 4 N-alkalikaolinite has been distorted and decomposed in kaolinite.il ; : IlI' !' I'__J V"ItY flL l ";1:Red earth soil remoulded and inundated with I N7.4 A with lesser intensity indicating that the struct.ure oftJ:; :)INa6 4A16 4Si9 60,2.4.6H20 and I .08Na20.Al203. I .68Si02._.l:/! jll"'_1' izI(fLI1 .08Na20 .Al203 . I .68Si02. I .8H20 (NASH) ( JCPDF,1990) in the case of red earth soiL Both the mineralsi;<fL:'? jf' t":':< 1 f ' "tI'r)of composition Na6 ;A16.4Si9.6032.4.6H20 and NaA12(AISi03)lo(OH)2, have been identified in the case ofsolution showed ne¥v peaks correspondin*" to Zeoliterninerals. The peak due to kaolinite mineral, which isnormally been observed at 7.2 A, has been observed atsilicate h,.･tlroxide h _･dratet ttThis is due to participation of kaolinite miner'al inchemical reactions ¥ 'ith alkali in both red earth andkaolinite. The peaks due to sodium alumino silicatesnot match ¥vith the any of the kno¥v patterns of zeolites,and the kaolinite alkali interaction products available inFig. 5. X-ral. diffraction pattern of red earth samples after consolida-fkaolinite minerals have disappeared compietely in case ofred earth, they have broadened in the case of kaolinite.solution. The ne¥v peak appeared in kaolinite specimenrlIcan be noticed that ¥vhile the peaks corresponding toNaOH solution has not showed any si**nificant changesin the X-ray diffraction pattern compared to sampleUntreated red earth'J Iserved in both red earth and kaolinite. At the same time itl .8H.O ar'e zeolitic minerals.o*':rpeaks corresponding to Zeolite rnineral have been ob-kaolinite and sodium aluminum silicate hydrateQY))63: KaolinitelY;"I[rNaoH+ NN 1-"IOHb'vY 'rY"IrvtY_1 _!vi "_v' lY' 'YvYt 'YII: :: IJJ _;;L_ _wl"'-'1-It ¥vas noted in previous section that the peak corresponding to kaolinite mineral is only broadened up inkaolinite remoulded ¥'ith ¥vater and inundated with 4 NNaOH solution. In red earth, the peak corresponding tokaolinite minerals has disappeared completely in both thespecimens remoulded with wat.er or 4 N NaOH solutionbut inundated ¥vith 4 N NaOH solution. Peak due tomineral NaAISi04, first order maximum at 2.47 A Ivithmaximum relative intensity ¥vas observed in the kaoliniteJspecimen remoulded and inundated with 4 N NaOH"_ 'I 'l- _tv fvf 'tsolution, ¥vhich were not observed in kaolinite remouldedj[ .1"! Kao"' :nne ¥¥'ater+1NNaol;4J /¥YIIJIe L i t l-1: :: i'l'YJUliJvYv"J Jr"__"I''tY Ylvl" J _1'Jlj i Untreated Klaolinite4! _¥¥JJr ' ivi[ ' I' 'JJfJ1lt'- JFig. 6. X-ral.' diffraction pattern of kaolinite samples after consolida-tion tcst: Q=quartz, K=kaolinite* NASH=sodium aluminum1 .08Na20 .A1203 . I .68Si02. I . 8H2 O (NASH) has also beenobserved in the kaolinite specimen remoulded and inundated ¥vith 4 N NaOH solution. X-ray diffraction patternof red earth specimen rerrroulded and inundated with 4 NNaOH solutions indicated the formation of (NASH),1.08Na20.A1203.1.68Si02.1.8H20, similar to the XRDpattern of red earth specimen remoulded with ¥vater andinundated vith 4 N alkali solutions.Slight differences in the type of minerais formed in redearth and kaolinite could be due to the differences at thesource material and conditions. Mohnot et al. (1984),Choquette et al. (1991), Chermak (1992), and Qafokusilicate hl_'droxide h･.･dratehave not showith water and inundated with 4 N NaOH solut.ions.Apart from the peak due to NaAISi04, peak due to'n noticeable changes in both red eart.h andet al. (2004) had reported that type of Zeolite is highlykaolinite. The intensity of peak due to quartz hasdependent on sour'ce material, chemistry of t.he poreincr'eased in kaolinite. No other major changes are seen.fluids, temperature and time.In samples inundatedvith 4 N NaOH solution, new 1SI¥rAPULLAIAH AND MANJU64Fig. 7(a). SEM photograph of consolidatcd sampie of uncontaminated red earthFig. 7(d). SEM photograph of consodated sample ofuncontarninat-ed kaoliniteFig. 7(b). SEM photograph of consolidated sample of red eartllremou ded lvith water and inundated lvith 4 N NaOH solutionsFig. 7(c). SEM photograph of consolidated sample of red earthFig. 7(e). SEM photograph of conso]idated sample of kaoliniteremou ded with lvater and inundated lvith l N NaOH solutionsFig. 7(f). SEM photograph of cousolidated sample of kao]initeremoulded and inundated lvith 4 N NaOH solutionsremou ded lvith water and inundated lvith 4 N ' NaOH soluttonsSEM Studies on Rec! Ea/'thlKao!i,7ite Sall?p!es afte/'Conso!idation TestsTo understand the morphological changes, the microstructures of selected samples after consolidation testswere examined by scanning electron microscopy (SEM).XRD studies have sho¥vn the formation of ne¥v minerals¥vhen red earth specimens are remoulded ¥vith ¥vater andinundated ¥vith 4 N NaOH solutions Similar patterns areobserved for kaolinite. Based on this observation, selected red earth soil and kaolinite specimens have been takenfor studying the morpholo_gical changes after' alkaiiinteractions. In case of red earth, samples remouldedwith water or 4 N NaOH solutions and inundated ¥vith4 N NaOH solutions ¥vere taken and compared ¥vithFig.?(g). SEM photograph of consolidated sample ofkaolinitcremoulded and inundated with 4 ¥_ * P 1'aOH solutions&, rINDUC ED S VELLING OF KAOLINITIC SOILuncontaminated red soil sample. Similarly, for kaolinitecase, specimen remoulded ¥vith water and inundated vithl N NaOH and 4 N NaOH solutions and as well as specimen remoulded and inundated lvith 4 N NaOH solutionshas been taken.From Fig. 7(a) it can be observed that the uncontaminated consolidated r'ed earth sample particles appear asuniform compact dense units. Figures 7(b) and 7(c) sho¥vclearly the effect of chemical interaction on the particlesof red earth sample r'emoulded ¥vith ¥vater or 4 Nsolutions and inundated vith 4 N NaOH solutions.paring these micrographs sho¥v that the particlesdegraded or ¥veathered completely and appear as veryparticles ¥vith uniform micropores.NaOHComhavefineFor kaolinite specimen also same changes in themicrostructure have been observed. Fi**ure 7(d) represents the micrograph of uncontaminated kaolinite. It canbe seen that kaolinite particles appear as if the plates arefirmly joined together and it can be obser¥'ed that ho¥v thecrystais of kaolinite tend to rner*'e to_g:ether on consolidation. This has been classified as inter-grown domain struc-ture. And ¥vhen the kaolinite r'emoulded ¥vith water' andinundated lvith I N NaOH solution, it appeared as if thesheets ¥vere getting separated out and a few discretedomain structures were formed, in lvhich the plate-likeparticles ¥vere arranged face to face in distinct domains,with distinct inter-domain voids (Fig. 7(e)).65studies. The formation of Zeolite minerals might be ¥'eryless and they might have been confined ¥vithin the ¥'oids ofred earth particles during the loading cycle. By the timethe loading of the sample is completed in the consolidation test and unloading starts after the lapse of considera-ble time during: ¥vhich more amount of minerals areformed leading to s velling during unloading cycle. Theabove conclusion that zeolites are responsible for s¥vellin_"_of soils is consistent ¥vith the observations made by otherresearchers. Kranz et al. (1989) reported that natur'allyoccurring Zeolite expands vhen hydr'ated and if rock iscomposed of lar_ :ely Zeolites, the entire rock may swellsignificantly as the rock becornes saturated. If such r'ockis constrained, significant stresses may develop as a resultof' hydration. Kruglitskii et al. (1985) had observed theintercrystalline swelling of zeolitic minerals systems dueto the formation of a gelatinous film. Heidug and Wong(1996) observed changes in the crystal dimension ofzeolitized tuffs due to ¥vater absorption that manifestsitself as a swelling of the rock. They reported that theses¥velling effects promoted tensile failure of thevell borevall .It can be termed that qualitatively the effects of alkalion red earth and kaolinite are similar. The relativedifferences can be expressed as follol¥'s based on relati¥'eease ¥vith lvhich the alkali reacts ¥vith different mineralsand consequent changes in the particle arran*･ement.The morphology of kaolinite particies remoulded ¥vithwater or 4 N NaOH solutions and inundated ¥vith 4 NNaOH solutions has changed completely (Figs. 7(D and7(g)) supporting the X-ray diffraction analysis that altera-tion of clay minerals has occurred or' new minerals areformed. Fr'orn the micr'ograph it is clear' that surface ofthe particles are getring cornpletely decomposed andchanging into very fine particles with uniform micro-IMPLICATIONS IN GEO1'ECHNICALENGINEERING PRACTICEIt is very clear from the above discussion that ¥vhenf'oundation soils of kaolinitic type contaminate lvithstrong alkali solutions, unexpected shvelling ¥vill inducepores.the soils leading to upliftment of the foundations.Without the knohvledge of mineralogy, mechanism ofMECHANISM OF VOLUME CHANGE BEHAVIOURsuch abnorrnal behaviour cannot be interpreted satisfactor'y. Therefore, as a general rule in the engineerin_"*.practice, such information on the mineralogy and micro-OF ALKALI CONTAMINATED SOILSFrom the above discussion, mechanism of the volumechange behaviour of alkali-contaminated soils can bededuced. The steep compression which has been noticedstr'ucture of a contaminated soil should al¥vays be pursuedas much as possible. It is necessary for geotechnicalin case of' red earth soil/kaolinite remoulded lvith ¥vateren*"ineers to understand the mechanism of soil pollutantinter'action to avoid problems such as landslides, groundsubsidence, settlement, erosion, pro*'ressive failures,and inundated ¥vith I N NaOH solutions could be moreundergr'ound structural stability, and f'oundation failuresdue to morphological chan*'es occurring durin*' the testby interaction of' soil particles ¥vith inundating fluid,and also to decontaminate the soils as ¥vell as to takeremedial measures.rather than the formation of ne¥v miner'als. It ¥vasbrought out from XRD studies that no new minerals orminerals ar'e for'med in the sarnples during the consolidation tests. The par'ticles became segregated due to interac-tion with I N NaOH solution as indicated by SEM studies. And this could be happening ¥vhen the soil/kaolitespecimen remoulded with ¥vater is inundated with I NNaOH solutions leading to sudden steep cornpression.The abnormal s¥ 'ell during unloading of both redearth/kaolinite r'emoulded ¥vith ¥vater or 4 N NaOH andinundated with 4 N NaOH soiutions is due to formationof' Zeolite minerals as confirmed by X-ray diffractionCONCLUSIONSA steep cornpression and normal swelling has beenobserved for the specimen compacted ¥vith ¥vater andinundated ¥vith I N NaOH solutions. This compression isdue to the segregation or break do¥¥'n of clay minerals dueto alkaii interactions,Due to f'or'rnation of' ne¥v rniner'ais, ¥vhich are havingfine pores and higher water holding capacity, on interaction of soils ¥vith 4 N NaOH solutions, abnormal swellinghas been obser¥'ed. The behaviour has been confirmed by 調66SIVAPULLAIAH AND MANJUX−ray di仔raction patter熱s and SEM photograp熱s． PetroIeu鵬Eng玉neers of AIlv1E，SPE13032・ The difference in the amount of swelling in the samples17）Palomo，A．，Blanco−Varela，M、丁．，Granizo，M．L．，碧uer【as，F、，compacted with water and compacted with alkali solutionbrings out the sensltlvity of the swelling to concentratloavariation and duration Qf interaction．REFERENCES1）Akokelar，D．，Cわaffee，A。and Howe，R．F．（珍97）：Tねe transfor− ma“on of kaoh践to low si三ica X zeo1琵e，Zθ011’θ3，19，359−365．2）Aznar，A．」．and La歪glesla，A．（1985）：Obtenclon de zeo巨tas as Vazquez，T．and Grutzeck，！〉置。V“。（1999）＝C丘1em玉cal stabil玉［y of cememitious materials based on metakao11n，Cαηθη’α’∼ゴCoηααθ Rθ5θακ1∼，29，997−1004．18）Provis，J．L．，Lukey，G．C、and Van Deve飢er，．｝．S。（2005）＝Do geopolymers actua1三y contain nanocrys｛all五ne zeolites？A reexam玉一 natlonofexlstingres縫1ts，Chθ’ηZ5砂oチル勧θ廟Z5，17，3075−3085．19）Qafoku，N．P．，Ainswor由，C C．，Szecsody，J．E and Qafoku，α S、（2004〉：Transporトcontro玉1ed k玉netics 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| タイトル | strain Localization in Solid Cylindrical Clay Specimens Using Digital Image Analysis （DIA） Technique | ||||
| 著者 | A. Sachan・D. Penumadu | ||||
| 出版 | soils and Foundations | ||||
| ページ | 67〜78 | 発行 | 2007/02/15 | 文書ID | 20981 |
| 内容 | 表示 SOILS AND FOUND．ATIONSVo1、47，No、1，67−78，Feb．2007Japa職ese Geotecilnical Societ》’STRAIN LOCALIZATION IN SOLID CYLINDRICAL CLAY SPECIMENS uSING DIGITAL IMAGE ANALYSIS（DIA）TEcHMQuEAJANT．A SAcHANi）and工）AYAKAa PENuMADuii） ABSTRACT The str＆in non−uuiformity due毛o the end restraint for a deforming specimen during triaxlahestillg of clay specimenswas minimized in this study uslng lubricatecl end platens．This rese＆rch presents童he eviclence of the occurrence ofstl畠ain loc＆llzation due重o shear banding withi！1the clay specimen by uslng DIA（Digltal Image Allalysis）techRique。ThevariationinstrainlocalizatlonpattemsofsoilspeclmenisalsostudiedforevaluatingtheinHuenceofconnningstress，loading conditions，stress history，dralnage conditions，a更1d so玉1’s microfabric（geometric arraugement of clay plate−Iets）by performing a series of lubricate（1−en（i trlaxial tests on solld cyhndrical speclmens of Kaolin clay。This paperpresentsacomparativestudybasedon由eobservedorientationofsぬearbandformation，andthein宅enslty・fstrainlocalization（by estimating the maxlmum local strain）wi由in重he specimell during its shear deformation process．Key wo雌s：compresslon，digital image a勲alysis，extensiol1，Kaolin clay，10calized deformatlon，lubrlcated ends，strainlocalization，trlaxial（IGC：D6）↓↓↓INTRODUC■10N When＆macroscopically homogeneous material ele−ment is subjected to a suf且cient至y豆ow homogeneous stress1□iapplied to its boundary，homogeneous（1eformationoccurs．As the deformation becomes larger，concentra−↑↑↑tion ofstra玉n at a loca圭zone within the element can occurbecause of the actual non−uniformity of mass density and（al Be∫bre b〔竃din9（b｝Uai50rmdc齢mladon（C｝S［rainlocaliza乳ioε1stl昼nessofthematerial，asshowninFl9．LFailureof！nαny engilleeriug materials is characterized by theformation and prop＆gatioll of zones of localized shearFig．1。Defom離ionof震soiielememunderextern窪1畳oadl“gco皿dl− tio難Sdeformation．The most typical loca王ized deformationIoca豆ization is caused by the imperfections inherent intransmisslon of micro−defects in the locallzation bandIeads to the formation of（iisplaceme飢discontinuity a難dthe soil specimen，the boundary constraints，and non−stress−free crack at macro正evel．Although出e localizationuniform loadlng conditions（Hvorslev，1960；Hl11，i962；Rudnicki and Rice，1975；Rice，19761Rice and Rudnicki，1980；Vardoulakis，1980；Desrues et aL，1985；Toklmatsuand Seed，19871Peters et a1．，19881Bardet，1990；B量gollitheory is considered to be well establishe（i ma重hematical−observed重n geo−materials is豆iuear shear ban（iing、Strainly，very limited experimental data on geo−materials havebeen Ileported（Vardoulakis，19801DesruesαaL，1985；Finno et al．，19971Lade and Wang，200i），mainly be−cause of the豆ack of exper圭lnental faci正ities to moaitor theand Heuecke正， 19911F玉nno et a至．， 1997；Szabo，20001Lade and Wang，20011Yimsiri and Soga，2002）．There−for鑓1ation of重he shear band an（i its orieutation．fore，strain玉ocalization ls considered to be a major Previous investigations reporte（1 由at the non−un玉一factor，whlch colltrols the overa110bserved mechanicalresponse of the specimen，at or near failure。Strai煎localization manifests in the fαm of a shear band，aheight of a specimell due to testing conditions can benauow zone of intense stra重ning（Jir＆sek，2002；Lai et aL，testing system（Rowe＆nd B＆rden，19641Barden and2003；Lade，2003）．Although，shear bandillg is one of theMcDermott，19651Sarsby et al．，1982）．It is now wellpossible defoImation modes，i巨s usually a precursor toknownξhat童he s重rai厳non−uniformity due to the endcatastrophic failure．The呈nitia歪thickuess of the locαliza一restra圭nt and the strain local量zation due to shear banding看ion band depends on the material’s micro−structure．Theare esselltlally dlfferent in mechanism，but confusion st圭11llil）fomltyofstressstateanddeformationmodealong塗heavoided by the use of正ubricated end platens in tri＆xia玉PosIdoctoral Fe“ow，HT Kanpur，正nd重a（ajantas＠iitk、acjl1）．Professor，Dept．of Civll and Environmental Engineering，Universi［y of Tenaessee，Knoxville，TN，USA（dpenumad＠u汰．edu）．丁負emanuscrlptforthispaperwasreceivedforreviewol｝July11，20051apProvedonSeptember25，2006．W煎endiscussionson由lspa葦）ershouldbesubmittedbeforeSeptember1，2007totbeJapaneseGeotechnica！Socieζy，4−38−2， Sengoku，BunkyQ−ku，Tokyo112−0011，Japan．Upon request漁e closing date may be extended one mon也．67 ISAC_HAN AND PENU *1ADU68exists on the role of end-restraint on the initiation andpropa*"ation of shear banding. In the past literature, It¥vas common to assume that triaxial experiments ¥vithlubricated ends on the specimens ¥vith slenderness ratio 1(height/diameter = 1) provide a more stable geometry andmuch greater uniformity of stress and deformationthroughout the test, and allo¥¥* the specimen to retain itscylindrical shape even at lar*'e strains. In the currentwell established, and they ¥vere applied to investigate thethin shear band type localization (Peters et al., 1988;Bardet, 1990; Bigoni and Heueckel, 1991; Sz,abo, 2000;Lade and Wang, 2001 ; Heueckel, 2002). The most typicallocalized deformation observed in geo-materials is linearshear banding.Most of the pr'evious experimental studies on strainiocalization were dependent on the visual obser'vationsresearch, all the experiments ¥vere performed on soilfrom the deformation profile of the specimens.specimenvith slenderness ratio I using a triaxial testin*'During previous investigation using triaxial testin*", thissetup ¥vith lubricated ends; thus non-uniform deforma-phenomenon was not studied in depth due to the lack oftions due to end restraints was assumed negligiblethrou*"hout the study. The focus of this study is toproper techniques for quantifyin*' the local strains ¥vith aevaluate the strain localization ¥vithin specimen of finegrained cohesi¥'e soil (clay) due to the actual non-uniformity of soil mass and stiffness of the material (not dueto the end restraints) at different testing conditions.It is important to note that clay specimens used in thecurrent research ¥vere macroscopically homogeneousmaterial before their shear defor'mation. If the stress andstrain states ¥vere interpreted at the stage of shear bandformation ignoring the fact that the strain localization¥vould have already taken place, the interpreted stressand strain would be inaccurate. Lin and Penumadu(2005) studied the strain locaiization patterns of hollo¥vcylindrical specimens sheared under combined axialtorsional loading conditions using digital ima_ :e analysis(DIA) technique. They developed an experimental setupfor DIA technique, a procedure for digital data processin*', and a pro_gram for data Interpolation; ¥vhich vasused in this study to produce the strain contour plots andstudy the initiation and propagation of strain localization¥vithin the specimen. This DIA technique ¥vas used in thecurrent research for' evaluating the impact of confinin :pressure, Ioadin*" conditions, stress history, drainageconditions, and soil's microfabric on the strain localiz,ation aspect for solid cylindrical specimens of Kaolin clay.PREVIOUS INVESTIGATIOl l?reasonabie degree of accuracy. Recent developments indi*･ital image analysis (DIA), to some extent, allo¥vs forthe capturing and studying local deformations within thespecimen as a function of global deformations. In thisstudy, many triaxial tests were performed to study thevariation in strain localization and pattern of shearbandin*' ¥vithin the clay specimens with respect to thechange in stress history of clay (normally consolidatedand heavily overconsolidated), inicrofabric of clay speci-mens (dispersed and flocculated), drainage conditionsduring shearing (drained and undrained), the type ofdeviatoric loading (compression and extension), and forvarying levels of effective confining stress. Particleassociation in clay suspensions can be described in theform of dispersed and flocculated microfabric. F!occu!ated microfabric refers to the platelets (or particles) thatare oriented in all possible directions; ¥vhereas, dispersedmicrofabric refers to the platelets that are aligned in apreferential direction (Sachan and Penumadu, '-006a).Durin*' the deformation process, a di**ital imageanalysis (DIA) was used to monitor the overall specimenuniformity, potential initiation of localization, and toquantify the specimen dimensions. Digitized data ¥ver'eobtained from digital images to perform the calculationsfor local deformation and strain profile, ¥vhich alsofacilitated the analysis for strain localization. Digitalimagin_2: technique ¥vas used in this research for all triaxialexperiments to study the evolution of shear bands ¥vithThe localization theory is recogniz,ed to be a mathematically ¥vell established concept for many years; ho¥vever,respect to the specimen and loading/boundary condi-only a few experimental studies including Rice andRudnicki (1980), Vardoulakis (1980), Desrues et al.behavior of cohesive soil.tions, which is important for evaluatin*' constitutive(1985), Finno et al. (1997), Lade and Wang (2001), havebeen performed using g:eo-materials. Hvorsle¥' (1960)observed shear bands and/or post failure bulging in aF.XPERIMF,NTAL PROGRAMseries of unconfined compression tests on clay specimens,and reported that the degree of non-uniformity at largestrains ¥vas much larger than theoretically expected non-the 1-D slurry consolidation method, which allo¥ved onlyuniformity due to the influence of frictional end restraint.Hill (1962) gave a general formulation for shear bands inelasto-plastic materiai using the concept of acceleration¥va¥'e in the context of a boundary value problem.Rudnicki and Rice (1975), and Rice (1976) proposedIn this study, solid cylindrical specimens of Kaolin clay(LL = 620/0, PI = 300/0, G==2.63) ¥vere prepared by usin__'vertical drainage at top and bottom of the specimen(Penumadu et al., 1998). Specimens ¥vith fiocculatedmicrofabric ¥vere obtained by mixing po¥vdered Kaolinclay ¥vith de-aired and de-ionized ¥vater at a ¥vater contenttion of shear band, considering a non-associated flo¥vrule. Based on Rice's ¥vork, the general principles ofof 1550/0, and then consolidatin*' the slurry under' Kocondltion at 207 kPa vertical stress in a slurry consolidometer (207 kPa pressure ¥vas applied in one step).The dispersed microfabric specimens ¥ver'e obtained byusin_g: the same procedure and by adding 20/0 dispersantlocalization of deformation into shear str'ain band ¥vere(Calgon) in the clay slurry of 1550/0 ¥vater content. Claycriterion for formation of shear band and critical orienta-si ; 'r,STRAIN LOCALIZATION N C LAY SPEClivIENS0718161412io06 - (a)¥05*C04-Peak (T-1 )peak (T-3)i 03Peak (T-2)02o':r416Axial strain (o/a)0,7 -(c)06o 5 - Peak (T-1 )(b)Peak (T-6)Peak (T-7)/ ,Peak (T :)08*06*04J02ooO O -Peak (T-5)o 4 8alr03-q = ( l'-O3 (d)16p:= ((J1'+(;2 +(J3f)/3Peak (T-3) peak (T-2)2428Peak (T-6)i4Peak (T-7)o 10CL* 08erPeak (T )02106-02-04q = (;1 -a3o i - p' = (ai +(5:2 +a3')13ooi6220Axial strain (olo)18-1,200469o o o.4 o 8 1 o0206p'/po'r/¥ peak (T-5)OO FoO 02 040608Iop'/ po12i416Fig. 2. Experimental data for triaxial tests (as listed in 'Table 1) performed on solid el. Iindrical specimens of Kaolin clay: (a) Norma!ized stressstrain curves for Tests I to 3, (b) F 'ormalized stress-strain curve for 'Tests 4 to 7, (c) Stress pat!]s for Tests I to 3 and (d) Stress paths for 'I'ests 4to 7specimen vith flocculated microfabric ¥ 'as obtainedafter 24 hours of consolidation; ¥vhereas, the dispersedspecimen was obtained after 330 hours of consolidation(Sachan and Penumadu, 2006a). The diameter (D) andhei**ht (H) of all the slurry consolidated specimens(dispersed, flocculated) ¥vas obtained to be 102 mm (H=D= 102 mm; slenderness rati0= 1). Initially these specimens were isotropically consolidated under 207 kPal276kPa/345 kPa of effective confining pressure. After'isotropic consolidation, the specimens ¥vere shearedunder compression and extension loading conditionsusing lubricated end triaxial testing device developed forthis study, and the measured data vere recorded on acomputer using a data acquisition system. The stressstrain relationships and stress paths for Kaolin clay for allthe tests are presented in Fig. '-. The Lubricated end triax-ial testing setup used in this study had a strain controlledloading frame, which ¥vas capable of applying compression/extension loads on soil specimen at desired axialstrain rate under different loading/boundary conditions;thus the global axial strain (8g) was directly obtainedgrease and pressed in such a ¥vay as to minimize theamount of entrapped air. A circular piece of filter paper,with much larger diameter t.han the platen is placed ontop of the latex membrane in a vay that the filter papercompletely covers the porous plastic strip on the sides ofthe platens. If excess pore pressure gener'ation is achievedto be zero during drained testing, drainage conditions ofthat lubricated end triaxial system are considered to be"good" drainage conditions. The other informationrelated to all drained and undrained triaxial testsperforrned in this study are summarized in Table I ; whichincludes axial strain rate for different tests, void ratiobefore shear deformation (eb=), specimen size beforeshear deformation (H *, Db=), Peak shear stress (o'p) andfor the entire height of the specimen. The other informa-failure location (8p) of each test.Penumadu (2006b).Lubricated ends require smooth and polished endplatens containing radial drainage ports at their outer* *(Sachan and Penumadu, 2006b). In order to prepare thelubricated end platens for testing the clay specimens, theend platens are cleaned thoroughly, a thin layer of highvacuum grease is spread uniforznly over each platen, anda circular piece of latex membrane is then laid on to theusing global displacements measured from LVDT datation about this lubricated end triaxial setup and itstesting procedure could be obtained from Sachan andJsurface. Porous plastic strip is extended circumferentiallycovering all radial drainage ports completely for achieving "good" drainage conditions ¥ 'ithin t.he testing systemDIGITAL IMAGE ANALYSIS (DIA)To address the strain localization and its impact on theinterpretation of test results, the deformation and strain SAC_HAN AND PENUh,IADU70(a)cameraSoft LightTriaxial SpecimenSoft LightTriaxiai specimen clampedDigitato the loading frameCamera(b)¥(c)50-¥e:f Z axis46e,xCLo42y = -O 0083x + 8 21 1R2 s OA9931X-CelibrationoruLL 38c:oCQjs 34Fac-¥¥¥torZ-Calibration Factor- Linear (X-Calibration Pactor)- Linear (Z-Calibration Factor)CQO 30400X a xisy s -O 0084x + 8 3523, > ¥¥¥ : =2 = O 9933500550Distanoe trom Cemera to Object, L (mm)Fig. 3. Strain iocalization }rsing digitai imageanalysis: (a) Digitai imaging setup, (b) Prepared Kaolin cla¥. specimen for digital imaging setup and(c) Caiibration factor using fiat plate anai)sisspecimenused for tr'iaxial testing, ¥vhich was confined in aare needed. Ho¥ 'ever, direct measurement of deforma-cast-acrylic cylinder filled ¥vith ¥ 'ater. The dots on thecomponents at various locations of a deformin_tion at various locations along the height of a specimen isa difficult experimental task. In the present study, digitalimage analysis (DIA) ¥vas used to evaluate the strain10calization in the solid cylindrical Kaolin clay specimenssheared by using lubricated end triaxial testing setup, asshown in Fig. 3. Digital imagin_g: technique in this studyuses a latex membrane (thickness 0.3mm) ¥vith dotsmarked in a grid pattern. CJrid points ¥vere spacedspecimen ¥vere tracked usin*' high resolution di**italuna*'es. To obtain the digital images of tr'iaxial specimens, a Digital camera (Kodak DC 290 "') ¥vith approximately. 2.1-million pixel resolution (1792 H: 1200V) wasplaced at 562 mm distance from the outer wall of cell, assho¥vn in Fig. 3(a). The digital camera vas mounted on atwo-axis controller, which allowed for precisely adjustingapproximately 10 mm apart, as sho¥vn in Fig. 3(a). Thecamera position in t¥vo directions. Images were thendownloaded in to a personal computer, and Ima*"e-Pro-latex membrane was placed o¥'er the cylindr'ical specimenPlus 4. I soft¥vare was used to measure the co-ordinates ofk ; FSTRAIN LOCALiZATION IN CLAY SPECI iENS7ithe points (dots made on the latex membrane placed onthe clay specirnen). The accuracy of measurement wastrue position and displacement of tracking dots on theO.'_ mm in vertical direction and 0.3 mm in circurnferen-used a similar technique for measuring volume changes intial direction. A soft light (Lo¥vell Softlite 2"-･ ') ¥vas used totriaxial testing.provide uniform illumination of the triaxial specimen andsignificantly reduced shadows in the digital images. Afterfinding the co-ordinates of the points on the specimen byusing Image-Pro-Plus 4. I software, the co-ordinates wereEVoLUTION OF SHEAR BANDsurface of cylindrical specimens. Macari et ai. (1997) alsothen used to get the shear band information by using acontour plot program made in pr'ogrammin*' Ian*'uageUsing the data from digital images, the strain components of a point on the soil specimen ¥vere caiculatedbased on the formulation developed by Lin ('_003). TheMAPLE (Lin, 2003).contour plots ¥vere developed to illustrate the strain field,Using irnage analysis software (ImagePro Plus**'), thedistance bet¥veen the specimen edges and the image edges¥vhich facilitated the visualization of the potential for the¥¥'er'e measured in terms of pixels. If these distances ¥verespecimen, such as those shown in Fig. 4, the verticalnot equal, then the carner'a ¥vas repositioned using thehor'izontal adjustment. The process ¥vas repeated untilboth distances are equal. The vertical position adjustment was used to bring the entire specimen into the fieldof vie v. The second horizontal adjustment ¥ 'as perpendicular to the image plane. This adjustment ¥vas also usedto ensure that complete specimen was in view and also foraccurate carnera calibration. The camera ¥vas calibratedto determine the true horizontal and vertical positions onthe specimen surface from digital images as a function ofdistance to image plane. A flat plate ¥vith grid pointsspaced exactly lOmrn apart ¥vas used to calibrat.e thecarner'a. This plate ¥vas fixed to the bott.om end platenstrain on the surface of the specimen is displayed and theintensity of color at certain point of the plot representsinside the triaxial cell, and ima*'es ¥vere obtained ¥vhilevarying the distance bet¥veen the carnera and the front ofthe ffat plate using the horizontal controller' of the camerairnages of specimen and corresponding local-strain-occurr'ence of strain localization. In a contour plot of soilthe magnitude of corresponding axial strain. It shouldbe noted that the X-coordinate of a contour plot isessentially the circumferential coordinate, so that thecylindrical surface of t.he specimen can be ¥'isualized in aplanar manner. The contour lines connect the points thatshare the same value of strain. It is more meaningful toread the pattern of a whole contour plot rather thanfocusing on a single point in a contour plot. Figure 4shows the deformation profile of Kaolin clay specimensheared under triaxial compression loading conditionsat the confining pressure of 207 kPa, which includes thedirection, ¥vere calculated for each image based oncontour plots at differ'ent global axial strain ¥'alues.Visual inspection of the images of specimen during sheardeformation can help in identifying non-unifor'mity ofdeformation ¥vithin the specimen but only ¥vhen the nonuniformities ar'e large enough in magnitude. An advancedtechnique such as DIA used in this research is requir'ed tomeasure the variation of local strains more precisely andstudy small magnitude of deformation that could lead tothe development of shear band type forrnations vithinr'epeated observations. The avera*'e calibration factor asthe specimen. As shown in Fig. 4, the images of claya function of' the distance between the camera and thespecimen at 60/0, I Io/o and 140/0 global axial strain did notirnage plane (corresponding to the front of the flat plate)¥vas obtained, as shown in Fig. 3(c).During the triaxial test, the specimen was confined in aexhibit a significant variation in the local deformationpattern by visual inspection throug)h naked eye. Aftercast-acrylic cylinder filied ¥vith ¥vater, as sho¥vn inFig. 3(b). The presence of confining cylinder and wateraround the specimen in a tr'iaxial cell caused multiplerefractions of light rays to occur, which needed to beaccounted in the analysis of digital ima*'es. Light rayscorresponding local strain contour plots indicated theformation of strong localized deforrnation zones at highbend, or r'efract, as they travel through media of differing¥'ere based on an element ¥vith maximum vertical dimension of approximately 10 mm; therefore, the accuracy ofmeasurement was 20/0 for' obtaining local axial strain.The contour plot at 60/0 global axial strain (Fig. 4(a))normal to the image plane. Using image analysissoftlvare, the observed distance bet¥veen any t¥vo pointscan be measured in units of pixels. The camera calibration factor was calculated from the observed distance, inpixels, and the known ¥'alue, in mm. Average calibrationfactors, one for the horizont.al and one for the verticalindices of refraction, ¥vhich can magnify or reduce theobserved size of the tar*'et object being analyzed. In triaxial testing, the refraction of light will cause the specimenprocessing these images using DIA technique, thestrain levels. It is important to note that the accuracy ofmeasuring displacements using DIA system was 0.2 mmin the vertical direction. The calculations of local strainsplied to the data obtained from digital ima*"es (Fig. 3(b))sho¥ved distribution of local vertical strains ¥vithin theaccuracy range, ¥vhich can be used to infer that within thein order to determine true specimen dimensions and *･ridpoint positions. By incorporating Snell's la¥v of r'efrac-constraints of the measurement system, the deformationwas relatively uniform until the global axial straintion, a 2-D cor'r'ection model (Parker, 1987; Lin andreached 60/0. Shear band with practically constant inclination emerged at 1 Io/o global axial strain and becamemore significant as the global axial strain increased. Theto appear enlarged. Therefore, corrections must be ap-Penumadu, '_005) Ivas developed to describe the relationship bet¥veen the observed and actual specimen measurements. This model lvas used in this study to obtain theshear band was observed to be fully developed at 140/0 !,SAC_HAN AND PENUN,1ADU72(a)8 oo'f /" ..* " <;'/ .r ' ..*--'oQ' (･;./e 5:/)ee/'/''// ' ji:__s)e5. ! ,o--OO)Q '1J 0 .//'i)+o0Specimen60/0 '" ;:.giobalaxia] atstrain- -0.0- -O'; -0.1, ' '*o.. ) e?j ]e_O. 1'/' {-O13.0O2J)e Re]atively Unifoml-+ +-O 1Deforrnation.5 oooo s eoContou-2 oo '-O 1o.oe I oo 2 oo s oooo4 ) ocal strainValueslobal axial strainIot for 60/0b3 ;.' . Specimen at llo/o : i$S- -o o7 cu* J o{ii -o'oo )'['j{i j!-ree'v/ol" # -o".i_*' #; '1 _o 1ee'i' "si"oo f;i'o "/;r . r.. ";/ iContOUr;'S'..__i-o 1/fr :f' ,5 ee 4 oo -e:oo' ') ei;r:-o 1-2 oo -1 oe o ooOt for 1 1 o/oiJSO 200 30e4J:) ocai strainiobal axial strainVaiuesSPecimen at 140/0S!. Si9:lobal axial strain*j '-i ti ;z;1(,( s :: ji'/::;:1:;1,:'1i;:/ !jii{Fig. 4Contoilr plots (X ax is: circumferential coordinate in cm, Z axis: vertical coordinate in cm) and the digital images for Test 1: (a) Uniformdeformation (reiatively). (b) Initiation of shear banding and (c) Shear band formation*-10bal axial strain, as sho¥vn by the contours of t¥vo localcausing an averaging effect in deforming local strainzones (Zone A and Zone B) in Fig. 4(c). Zone A shows amuch smaller values of local axial strains (8100/0) incomparison to Zone B (14160/0). The contour lines arevery dense in the Zone B as compared to Zone A, ¥vhichvalues.In Fi*･. 4(c), the Zone C represents a part of anothershear band, ¥vhich is approximately parallel to the shearband in Zone B. For local strain analysis, the imagestaken during shear deformation covered approximatelyimplies a dramatic transition of the axial strain values.Therefore, the z,one of intense straining (such as Z,one B)1 /3 of the perimeter of specimen. At the end of shearing,can be regarded as a shear band ¥vith an approximatelyconstant inclination. It should be noted that the localthe specimens ¥vere extruded from the triaxial cell andthen visually inspected to e¥'aluate the continuity andstrains in the shear bands could be much hi her than ¥vhatis depicted by the contour plots. This is because the shearinclination of shear bands around the specimen. Fi*･ure 5bandsvere much thinner than the distance bet¥veennodes of measurements (approximately 10mm grid)shows images of the specimens extruded after shearin*'under triaxial compression and extension stress paths.These images ¥vere taken from four orthogonal directions 73STRAIN LOCALIZATION IN CLAY SPECI夏MENSZone of measur鷺1easure【11ents‘1 i ir”1’ r一齢 胴儒榊欄 匹 F 匹講・ ・躍咽一 r、＿＿庸’彗 lShla「lan虫1『’1’、 暉 医 睾 匿 胸ノi 臨 1 ノ：Ψ 1 監 み 1 8、し ： 臼孟臼 真臼『『 1 ’L 庫！17』 1器踏；＝尋， ”1 i1 禰 『 尊 一 F（a〕3−DView ．融ddi【iQn註l zonビ（b）FrontVlew（c）TopViewFig．6．InterpreIa重ionofshearbandlnclin滋ion（4り oflocaUzごd defb㎜εゑ【io臓speclmen and global axial st三lain（ε，）applie（10n the speci−men by Ioading frame was more thaa4％．For examplelthe dif董（）rence inεm andε黛for Test l was1％in Fig．4（b）（玉nitiatio芝10fshear ba亘ding；ε9篇11％，εm＝12％）alld4％ Addi雨onal zone oflocalized dビ負）mlation呈n F皇9．4（c）（formation of shear banding；ε皇淀14％，εm灘18％）．Thus，the global axial strain at the stεしge of shearballd formation（εsB）was observed to be14％for Test1。 It shou1（l be noted重hat tbe observed inclination of theshear band in the contour plots（Fig．6）was not the trueinclination of the shear band玉n the3一王）space．Figure6i正1ustrates the conver・sion from the observed inc正ination tot紅e true inclinatlon oξshear balld with the3−D view（Fig。6（a）），front view（Fig、6（b））and top v呈ew（Fig、6（c））．Assumlng a shear band（＆n ellipse containing Points1，ノ，F藍9．5、She且rb謎紅di矧ginKao嚢董nclayspeclmensus員鶏glub罫ica重edend ωaxi段lsetup：（a）Compress眞on曲earlng（Test2）and（b）ExIension s董1earing（Test4）ん，and1）cut tを1rough the cylindrical specimen duli臓g atest，亡he true inc至ination should be the angleψ・（Fig．6（a）），wh呈c勤is the angle bet∼∼・een the vertical direc芝ion（r【1ajorP「圭nciPal s亡ress d重reαion） and the shear band plane．to completely observe the outer surface of specimen（fron毛，rear，rlght，and left views）．As shown in Fig、5，出e圭nc1圭nations of a至l the thin shear band formations in aAngleψ・can be calculated by uslng Eq．（至）： rtaガ1（4破） （1）sheared specimen were observed to be identical，and ltwas true for bot勤compress三〇n and extension tests．Thewhere‘1is the outer di＆meter of the speclmen an（1His thespecimens were also observed to have additiona豆zones ofpo呈nts i，ノ，ん，and l are in the p1＆ne of the shear band，thelocalize（1deformations as c＆n be seell in Fig．5．followingrelatlon曲ipholds： The stress−strainτe豆ationship for triaxia正colnpress圭o煎test on Kaolin clay specimen with Hocculated microfabricexhibited the peak shear stress互ocation at apProximate隻yvert呈ca至dist＆nce bet、veen point ／and ln （or 1）．Since H繍（π4／2減jk）・h （2）where h is the vertica玉（iis重ance be重ween points／andん，11％axial straln（εp），as shown in Fig．2（a）．It is im−and 14jk is the arc 至ength betweell points／ and ん inportant to note that sm＆11amount of localized deforma一F量9．6（c）．The contour plots ill Fig．4shows esse駐tiα1至y the重ions were observed bef』ore 11％ axial strain，an（i theinner dashed rectangle in F玉9．6（b）．Therefore，bot勤h andcleg茎lee of正ocalization increased as the shearing Process。4jk can be rea（I from the contour plots，Equation（1）ca獄colltillued．However，a clear shear b＆nd type foImationbe rewritten as Eq． （3），whic紅 is independent of thewas observecl start圭ng a｛ a global axial strain of 11％．specimen diameter：It cou豆d be reasonable to interpreεthat stra三n localizεしt圭oninitiated at peak shear stress 正ocatioa，＆nd the fεLi豆ure 一1（2鴇lk） （3）planes in the fornl of s圭gni負can重 shear ba亘ds weredeveloped in the post−peak response．Peak shear stress（σ卸）is the nlaximum value of devia重or stress experiellcedby the soil specimen du正’ing its shear（ieformation、TheThe value of true inc豆i！1atlon angle（ψ）fQr dl任erent triaxl。＆1tests perfomed on cylindrical specimens of Iくaolin clayare given in Table1．axia歪stra重n （globa1）at peak shear stress Iocatiou（εP）隻stermed as the“f＆ilure”of specimen in the current study．Stress paths （Figs． 2（c） εmd 2（（i）） showed clearly thefaiiure point ofeach test，which represents the peak shearstress level．玉n the current research，formation of shearbanding was exp正a星ne（i as the stage wheret紅ed隻fferenceinmaxlmum local axiαl strain（εm）experienced by the sollDISCUSSION ON LOCAL STRAIN ANALYSIS Table l suτnmarizes the information related toorientation ofshear band formationwithin the spec圭nlellsdurlngαseries of tri＆xlal tests performed under dlf罫erentloadi駐g／boundary colldit主ons．The contour plots of local 74SAα｛AN AND PENUMADU■ableL E∬ectofv部lousfacIorson1hes粟面nloc段iiza書ionp飢temsand芝heorien纏onofshe段rb蹴dsobservedin重hepa1IemsTeSt No．a）τeStingconditlonsb）Co面nlngstressc） Specimen typed）Ob、andHb、（P、獣私司02mm）e）eb、，Axials覧rainrateTrlaxlal S駐ear testStrain localizat玉on analys玉sPeakshearφ’StreSS，（deg）εSBεrn（％）（％）（％）εP ψ（deg）σ6（kPa）■esI la）Undrained，Compressionb）ρ‘讐σざ漏207KPac） NC，Floccuiated m圭crofabric12731、711．0王4．018．015430．111．514．019．03618629．514、O玉4、820．O3914735．211．013，026．0311062董．812．514．019．03244826，626．026．029．0NA25127，710、911、0夏7．03｝d）必）b、濡99J mm，Hb，筥1005mme）θb，竺1．03（θ1竺1．18），Rate聯0．05％／m撤Test2a） U鳶dra玉ned，Compresslonb）ρ‘竺σ‘漏276kPac）NC，Flocculated mlcrofabrlcd）Z二）b、繍98．7mm，乏ノb5置99．8mme）εb、筥LOO（ei罵1，i8〉，Rate竺0，05％／謡nTes重3a） Undra玉ned，Compress五〇nb）ρ6漏σご讐345kPac）NC，FIQcc温ated microfabyicd）Ob、竺98．3mm，κb598．8mme）θb、漏0．96（貯L18），Rate罵0、05％／翻nTes芝4a） Und】rained，Ex−ensio貰b）ρ許σ評276kPac） NC，Flocculaεed microfabricd）Pb、竺98、8mm，厚b、漏99．7磁me）θb、＝1、00（a瀟1．18），Raτe需0．05％／min■es重5a） Undrained，Compress玉onb）ρ‘需276kPa，σ‘竺28kPac）HOC，Flocculated mlcrofabricd）Pb，竺99．9mm，κbs司OLOmme）θb、司．07（θi繍1．18），Rate瀟o．05％／ml員τesl6a） Drained，Compressio録b）ρき翫σ‘罵276kPac） NC，Fiocculated m玉crofabricd）Pb、漏98．8mm，乏1ド9％mme）θb，竺1．oo（貯1．18），Rate竺o，oo5％／min■est7a） Undra玉ned，Compress1onb）ρ6瓢σざ竺276kPac）NC，Dlspersed mlcrofabrlc33d）Ob，竺100．2mm，κb、漏99．6m鵬e）θb、罵o，69（θ冊o．79），Rate罵o、oo8％／mlndeform＆tionsonthesurfaceofsolidcylindricαIKadinclay specimens were analyzed witむrespect to the variationin fonowing factors：Coafining Pτessure，Externa1歪oad−ing co賑ditions，Stress History，Drainage conditions，andkPa to study the impact of cQ面ning Pressure（）n stτain玉ocalization pattems of Kaolin c正ay．T｝1e effect ofanisotropic loading conditions and specimen7s stresshistory were also studied by perfoτming an mdrainedMicrOfabr隻c．tr三ax量al extension test on NC clay spec玉men atσざ薫276S〃πi11．乙oごα”《σ∫ioll Pθπθ1串175ρプCloッSρθ（フi117（∼175Shθθ1・θ4（OCR二10）atσ6＝28kP段．The contour plots of locaIkPa and compression test on HOC clay specimen‘！nゴθ1・Un4ズαiηθ4Coηごi！ion5stralnmeasuτementsduringtriaxialcompressiontestat The undrained triaxial compression tests were per−σ6＝207kPa weτe discusse（1earlier，as shown in Fig。4．formed on NC clay specimens with釘occulated micτo・fabric at the con封ning pressuyesσざof207，276and345Similar contour p至ots for the other incl量vidual tests areshown呈n the Fig．7to歪0．嚢 75STRA正N LOCAL夏ZAT正ON IN CL、へY SP匠CIMENS（a）（訊）瞭／頓飯ゆσ7 ・鱗心コGぴ・ 心田lqoアゆ ザコロア 鍵罵躯㍑ぞ 。辱呵 蓑一1心1しO喉、轄欄舳欄1ゴ㈱lio．嚇『c倒 『 繍 ヨ ロいく i ・o嘱 RelativelyU蓑i｛bm1節 De50磁ation 一G侭。。。1翫コ2。。。。 ヌzq 4野。ca夏s舳nさOQ −493 心Ga Contour Iotテor6％ lobal axial strain va匡ues Con重our 10ぜor6％（b）津田1喝1q讐2 0二 rマ 03 鵬ca1宙aiqiobal axial st『ain V副ロ￠S（b）Fig．7． Contour ploIs（X鍼is＝circumferentlal coordi簸a重e in cm，Z aXiS＝vertiCaiCOOrdin訊重einCm）and山edigiIalim謎geSfOrleS｛2：（a）Fig，8．Contourplots（λ1段xis：circumfere凱茎謎lcoord蓑疏atei臓cm，Z 瀬s：vert隻caicoordi戯eincm）andthedigit盆賎magesforTest3：（a） U臓iεorm deformation（re塵adve匪y）＆nd（b）S勧ear ba臓d forma“oI1 Un置orm deformatio聡（reia“vely）a毅d（b）Shear b扱nd form滋ionE価ectofCon且ningPressureoccur at thepeak value ofstress−strain curve，as shown in As shown in Figs．4，7and8，the distribution of localFig．2．It is thus reasonable to intelpret the s重ate ofstressaxialstralnonthedeformingtrlaxialspeclmensattheand s書ra重n froln measul−ed ex重erllaHoad and displacemen重t致ree con且ning Pressure values of207，276，and345kPaassuming a uniform state of deform段tion up to an axialwas observed to be uniform￡or global axial straln valuess重raill value of11％for compression stress path and ofup to6％．The shear ban（i emerged at11％of global axial11．5％forextension．Theshearbandformationwasstrain＆nd became more＆nd more sign呈ncant as the strainQbserved to be ful正y developecl at a globalεしxial stra圭n of正evel increase（i． Shear b＆11ding was observed at 14％I4％forcompression，and13％forextension重esting。Aglobal ax圭al stra重n forσ6凱207an（i276kPa（Fig．4（c）andsignific＆n重d呈f罫erence was noticed between the values of7（b）），and at14．8％g至oba玉段xial stra圭nξorσ6；345kPamaximum local axial straln（εm）for compresslon（19％）（Fig．8（b））．For al1亡he three cases，strai且10calizat圭on∼vasobserved to be initiate（1for stress state corresponding toand extension tests（26％），which illdicated tha｛the strainlocahzation was much stronger in the specimen subjectedthe occurrence ofpeak shear stress圭n the stress−strain plotto extens呈on s重1−ess多aξh．The orientatiou of shear band（Fig．2）。The intensity of stra玉n玉ocal量zαtion was observed（ψ）was obse11ve（1to be slgnif崖c＆ntly higher for compres−to be Inuch s案ronger ξor higher con負ning stressession loading（36。）in compariso11to extension ioadlngexhibiting an increase i且the value of maximum local axialstr＆in（18−20％）experieuced by the specimen with theillcreaseincon丘ningpressure（207−345kPa）．Atrendofincreasing ψ a【191e was observed with the increase incon丘nlng pressure，which vαried fromψ孟31to390forthe varlatlon in connnlng pl’essure from207to345kPa，（310），as listed in Table L The Ileason coul（1be attributedto the rotat圭on of major prillcip段l stress by900 fromvertical to horizontal d玉rection．Dur呈ng ex重ens玉on shear−ing，the specimen tends to hεしve a smaUer cross・・sectiona1＆rea（11ecking）＆t由e middle of the clay specimen com−parecl to tke area a芝top and bottom of t鼓e specimenas lis重e（1in Table里．（Fig．9（b））．The necking of specimen induced by theEf罫ect of Extemal Loading Conditions Co飢our plots for compressiou and extension stressinclination of sぬear bands，wh三ch was not a亘issue forextension loading con（1it三〇ns could ＆lso 量nfiuence thecompression loading．paths（Figs．7and9）showedthatlocaldefomationw＆smiformly distr圭bute（1up to6％global axial strain forboth重he loading conditions。Small zones of locaiizeddeformation were observed within重he c1＆y specimen after6％of g三〇bal axial strain and were connected with eachother in the process of further s｝玉ear defQr1nat三〇n。Strainlocalizations圭n the form ofshear ban（1s were observed toEffect of S宅ress History of C1＆y Speci∬1en For the HOC specimen，the g星obal axia豆strain （ε9）coτresponding to uniform distribution of strains （ε9蹴6％），initiationofshearbanding（ε9聯H％），aadfullycleveloped shear band（ε“14％）were the same as t難osefor NC specimen．They also shared重he same vεし1ue of SAC_HAN AND PENUMADU76(a)O(SPecimen at 6010I 0'2/9 Oe --O S.globai axia] straine 'o_e '$. . /ot2i.,.tf OChO he ,-. Oal}I xrl {f o 1; OT1O 2'Ft"T-ollS J Colli o e' Oi _ *-Relatively Uniform0Deformationo hoe -e oo5 OOo e-2 oo 1 ooContourI uo 2.0{) 3 Qo0ocal strains')lobai axial strainiot for 60/0Valuesb'oc'--0'12/ /' '!1/ ;'tl ' ;'1i(L2""'1li; ¥' ¥L___o l2 :;c-'1 ; .rSS?'4; ';''r'/' 1 l:!'* ' t '- : _Shear Band! !/_/ *' :':1T:7''t 'o' _'__li'o¥V-31! /o ' + ; - '^ * B ; S '_ ' *-- ZOne* =*i * -'5i; sQQs'¥!' -f2+t":--fiT:oo-_ i-/ ' ' '/://'!; 'J' ) : ! r -o'o: ! ;{ '_. ¥-^ '!:! + -*-*-'('/i #'t ss'- J: 'ilL :s' t:' !;{ s+j""'J2-'i{'i's' +"t **/'SSS't'';:i ? # :Zone A -/' ' i' 'x#s '- s ; I+ ¥ +--" !'' ' ': ' ""e/ S-s oo;tLiL- ,,S},:'gjobal axral stramIlllJi'; '!1 oooo -s io -2'oe-o ODI oo 2 oo 3 oo, ; . '!i':*"; " * "' ';o li"olh o 12'/ :'t- ,,'i'.ila i_ -J_*..i'_ '.Tl:f+-t!r',:i+ o -'e'__ ;1:j _ i#t#?-SSj x/ f"!Lt s:oQ'*- ' f f';it''!;o'/f *=f;""'fS!!'/:'O ' !;}i i'/S..-o=S "'!SS';j * SPecimen at 13'/o ' '.0'1al I005f;.i Li :oo,*h---4c ocal strainCOntOUr lOt fOr 1 30/0 lObai aXlal StralnV al ilesFig. 9. Contourplots (Xaxis:circumferentia! coordinate in cm,Zaxis: vertical coordinate in cm) and tl]e di*gital images for Test 4: (a) Uniformdeformation (relative!y) and (b) Shear band formationmaximum local strain (e**) ¥vhen the shear band ¥vas fullydeveloped at 8g= 140/0, as sho¥vn in Figs. 7 and 10. The(a)orientatlon of shear banding for NC clay (36') ¥vasobserved to be larger than that for HOC clay (32'), aslisted in Table 1.(b)ei;;;'{:'i:!:i;I ! 'i;!"I:;i't4';l'I{'t'1"_':/ "'i !_!' ;ii/;:;1!1:; !;i:!;::!;;::::i:i/:;j,; ;:.; ' sh ar 3B_.,aond''#+-ts +*; ss -;-^sf:;;;/l ;'1 !';i ;;/f; /'i ;;/'{fi!:t':;i:::!:;*!;s" ' $ i;i-Qe'::';' " i;""s"; "!;*' /;___ l '' _ i-"-*-' '; ' f:zone" 'B'Effect of Drainage ConditionsThe impact of drainage conditions on strain localization behavior of clay specimens was studied by repeatingthe triaxial compression test on NC clay specimen ofKaolin clay with flocculated microfabric at the confiningstress of 276 kPa, and by allo¥1'ing free drainage duringthe shearing stage of repeated test. The contour plots oflocal strain measurements durin*' drained compression" :; /;ss iLL_ ise; s-- '"'*"teIIS *QIe ttzone A''iTel**;1#;1# ss ='. ;%e {'---';;i';;:t; : ;i:" *-### 'ee ''1;'('"i -' ;'!r! "*" ;''i ' ;!;" ' " " +* ;'#t ;/"' ;:5CQs'i '';*' '+s #! *# 1so s ) -2co - I o oc2eo se'contour !otfor 140/0 Iobal ax 21 straln1 !'Loeai stl inVaiuGsPig, lO. Contour plots (.V axis: circumferential coordinate in cm, Zaxis: vertical coordinate in cm) and the digital ima**es for Test 5: (a)Uniform deformation (relatively) and (b) Shear band formationtest are sho¥vn in Fig. 1 1. The distribution of local axialstrain ¥vas observed to be uniform until 60/0 *'10bal axialstrain for undrained shearing and 130/0 for drainedshearing (Fi**s. 7 and 11). As discussed earlier, theundrained triaxial compression showed clear evidence ofshear bands ¥vithin the specimen at 140/0 global axialstrain (8sB). During drained triaxial c.ompression test, thespecimen did not shol;v linear shear band type localiz,eddeformation mode as observed during undrained testin*';however, it ¥vas observed to have many small z,ones ofhi_ :hly localized deformations at 260/0 of global axiaistrain. The reason could be attributed to the differentmodes of instability causing strain localization fors ( r. 1STRAIN LOCALIZATION IN CLAY SPECl IENS(a)77(a)e**e -* 1 07*J ;)" "IptRelatively UniformDeforrnationet -3eeContour2e+*1O O tei 2.Ge 2 !Ot for 4e/oS i!ob8i axiai strains Q5,,Local stra nVaiues(b)(b)# s ' { i" #" __; ' ;# cs s#"( S'xS-##!!--= '#f W '- ' ^ *" i"1' "s#soH;" '';i'/ #s; *+;;; /:!_ i- # *s;t; ;.. -#^ i"^- ' s#'#' ;;;;1;'S ##rTTiS#; i$; -'i-;-;r - '# t' ii'!'ix""x';# ;(' *'S ** ii# };;;:1;.#'-f t ;+ , 1 ;. ii.;j.#s* ;!!sl' i '/"#'SS's ; " i '*'/'# !' !;!S. ;lif ooHio-!"i '; : -"{' :; -L'!ft'* sj sQo*Lri':'; (i$;1ii's :S{ -;r' i{#ii!'.:;! ;" ; ': '"''" ;x '; 's'j; i' ;;;::::;:;'i!;ji';s ;*.";..s;*r 1i;t _ ._ -*s't_'-' '"'Zone ofLocalized' ;)' ;l "; ;:';! :; :i! ";;:-s s!#1 - i yZi'P:!'# ' ! '_' (;is:'i # SS ;'/s s ":' ii s :s "'t;" DeFfonn atron? s;; ' --i; x#:'1- ' "' ii:!'!# i' :s "#x"''S''r;i* -':s# # i-:;' ' ; ...;;:;:::; ;:;: .":tx;'#!--'5 oo 4 oo 'i Qo -2 ee-eQ e e s I Qe:;_";ii !!!"1' '##i" ;';;; :3 eoContour lot for 260/0 Iobal aXiai strainLoc tl strainVatuesFig. 11. Contour plots (X ax'is: circumferential coortlinate in cm, ZFio*. 12. C',ontour piots (X axis: circumferential coordiuate in cm, Zax, is: vertical coordinate in cm) and the digital images for 'rest 7: (a)Uniform deformation (relatively) and (b) Shear band formationaxis: vertica! coordinate in cm) and the digitai images for Test 6: (a)Uniform deformation (re!ativel .') and (b) Shear band formationvarying drainage conditions. During undrained shearing,the instability caused by pore pressure evolution couldplay an important role in the development of shear bandtype formations within the specimen, which apparentlydid not occur under free drainage conditions duringmicrofabr'ic sho ved a clear formation of shear band atpeak shear stress follo¥ved by a sudden failure response.A notable difference in v/ Value ¥vas observed for flocculated (,36') and dispersed (33') microfabric, as listed inTable 1.drained testing.CONCLUSIONSEffect of lvlicrofabriccylindr'ical specimens of fine grained cohesive soils (clay),A series of tr'iaxial tests ¥vere performed on solidIn this research, t¥vo extreme microfabrics of Kaolinand a technique with digital image analysis (DIA) wasclay vere used to study the effect of microfabric on strainlocalization behavior of soil. The r'esults of triaxialused to evaluate the initiation and propagation of strainlocalization ¥vithin the clay specimen due to actual non-compression test on Kaolin clay specimens withunifor'mity of soil mass density and stiffness of theflocculated microfabric at (7g =276 kPa were discussedearlier (Fig. 7). The same test ¥vas repeated using theKaolin clay specimen with dispersed microfabric, and thematerial at dift rent testing conditions. In the currentspecimen's ends; thus non-uniform deformations due tomeasurernents are sho¥vn in Fig. 12. The distribution ofend restraints were assurned to be negligible throughoutlocal strains ¥vas observed to be uniform until 60/0 globalthis study. The impact of confining stress, Ioadingaxial strain for flocculated rnicrofabric and 40/0 fordispersed microfabric. The initiation of shear' bandingvas observed at 9 and llo/o global strain for dispersedand fiocculated microfabric respectively. The shear bandconditions, stress history, drainage conditions, and soil'smicrofabric on the str'ain localization patterns and shearfor dispersed microfabric (8sB= 110/0) in comparison toflocculated microfabric ( sB=140/0), which indicated ahigher possibility of sudden f'ailure in Kaolin clay ¥vithdispersed rnicrofabric. As shown in Fig. 2, the peak shear'stress ¥vas observed at a global axial strain of 11.50/0for' flocculated microfabric and 10.90/0 for dispersedmicrofabric. Unlike the response of fiocculatedmicrofabric specimen, the specimen with dispersed_triaxial tests, ¥vhich significantly reduced the friction atcorresponding contour plots of local axial straintype formation ¥vas observed at much lo¥ver' strain le¥'els!study, Iubricated end platens were used to performband orientation ¥vas discussed ¥vith the follo¥ving keyobservations.1) Ilnpact of Confining Stress: A clear formation ofshear' banding was observed at the same strainlevels for all values of confining stresses. Muchstronger strain localization and a lar*'er value ofthe orientation angle of shear band were observedfor higher value of confining stress.2) Impact oJLoading Conditions: Str'ain localizationvas obser¥'ed to be much stronger for extensionloading conditions in comparison to compression. 璽78SACHAN AND PENUMADU The value of orientation angle of sheaτban（i was5）Finno，R．J．，Harris，W．W．，Mooney，M．A、a真d Vigglanl，G． estimated to be smalleゴor extenslon s員earing than （1997）：Shear bands in p玉ane s！ra茎n compress玉on of loose sand， thecompressionshe段ring．3）111脚α‘ゾS惚∬Hi3ガ01ア：Strainlocalizatlonpaト tern，shear band formation，an（i tむe orientation of Gθα8ch吻置’θ，47（1），149−165．6）H盗，R．（1962）＝Acceleraεion waves in sollds，ノ、Mθぐ1∼．P1∼）乳∫’‘∫o∫ So〃ゴ5，10，1一韮6、フ） Heueckel，Fr．（2002）＝Reactive plast玉c呈ty for clays dur1ng dd筆ydra一 shear ban（i were observed to be the same for both 巖on and rehydratiol｝．Part1：concepts and op“o職s，1n1、，ノ1 tke NC and HOC specimens oεthe Kaolin cl＆y ひ・，18（3），281−312． lndicatlng no signincant impact of stress hlstory。4） 11刀ρααρゾ01ηinθgθCoη4i∼ion5＝The（irained test− ing di（i not show the linear shear band type forma− tions as observed for undraine（i testing．5）乃7ψσαoゾMiσ磁めric：Dispersed microfabric showed the shear ban（i format量ons at豆o、ver stra三n Ievels in comparison to Hocculated microfabric．A notable difference in tbe orientation angle of sheaτ bands was obtained for both the micτofabrics．P1σ5∫ノd一8）き｛vorslev，M．．L（1960）：Physlca！componemsof【heshearstreng由 ofsaturatedclays，！1SCE1∼ε5εα’納Con∫onS／1θ01’S！・1θ’19’170∫ Cohε5’vθ So’Z5， Un呈vers玉ty of Coiorado， Boulder， Colorado， 69一一273．9） Jirasek， ∼〉1， （2002）＝ Object玉ve modeHng of strain loca巨zation， Rθη置’θ丹αncαZ5θびθGθπ’θαソ〃，6（6），匪120−H32（lnE鷺911sh）．10）Lade，勲、v。and wang，Q。（2001）：Analysls ofshea由anding i郎rue triax玉al tests on sand，∫．Eng1召．1》θch．，127（8），762−768．11）Lade，P．V、（2003）：Analysls and predlαion of sぬear banding聞der 3Dconditionsingranularmaterlals，So1なαノ’ゴFα’11伽ioη∫，43（4）， 161−172．12）La1，T．Y．，Borja，P．V．，D蟻vemay，B、G．and Meehan，R．L． （2003）： Capτuring strain local圭zat玉on be｝1玉nd a geosynthet玉c一ACKNOWLEDGEMENTS 【「e玉nforced so温wa冠，／1∼∼．／．∫01’ノ〉置〃11．〆11701．ハ4（∼∼h、Gθo〃∼θ‘h．，27， Financia歪SupPort from National Science Fouadat量on13） L圭n，簸．（2003）：Three工）imens圭onal Static and L》y鷺a漁ic be員av玉or of 425−45…，（NSF）由rough grants CMS−9872618and CMS−029611i Iくao1沁claywithcontrQlledmicrofabric貸singcomblnedaxlaレtor−is gratefully acknowledged．Any ol）inions，盒ndings，and slonaltest1ng，P砂．乃θ5Z5，Un至versltyofTenηessee，Knoxville、14）Lin，H．and｝》enumadu，D．（2005）：Strain Iocal1zat1o鷺i鷺axiaiconclusions or recommendations expressed in this torsiona王tes重ing，ノ、E119’召．Mθch．（accepted）．material are those of authors aad do not necessarily15）Macari，E．，1．，Parker，，∫，K．andCostes，N．C．（1997）lMeasurementτeHect the views of NSF、 ofvolumec益angeslntrlaxlahesτsusingdigltahmaglng［ecぬnlques． Gθo’θch。τθ5∼，／．，GT，10D、」，2（1），103−109．NOTAT10N pi＝In王t玉aL diame【er of spec圭men 五）b、漏Dlameヒer of speci螢en befbre s姦earl賞g（bs） 私竺1醸la出eigbt of speclmen Hb，漏Heig蹟ofspeclme曲ef』oreshearing（bs） θi讐1顧alvoldrat1oofspeclmen θb5Vold ratio before shearlng（bs）of specimen ε評Globalaxlals【rainapPlledon由especimenbyloadingframe εp讐Global axlal strain aヒpeak由ear stress Ieve1 εsB罵Globa盈ax玉al strain at the format1on of S』ear Band1ng（SB） εm竺M＆xlmum“Locai”axial stral簸experlenced by the soli at iIs local zones w叢tねin tぬe specimen dur玉ng its s｝玉ear deformation processOCR＝筥Overconso1韮dation Rat玉oHOC漏Heav員yOverco鷺so！idatedNC編NormallyConsollda【ed ρる筥Pre−coasoUdat玉on pressure σ‘漏Effectlve con丘n1ng pressure before shearing（bs） σ6竺Peak sbear stress w｝1玉ch correspondsし赴e max呈mum vaiue Qf sぬearstressexperlencedby由especlmend面nglEsshear deformation process φ’讐聞奄ctlvefrlctionangleatpeaksめearstressleve1 》罵Angle o∫Sぬear Ba麟d（SB）from vertical axis（Z axis）16）Parker， J． K． （王987）： 三磁age processing and analysis for 磁e me面anicsofgranularmaterlalsexper1me瓢，滋SM万Proc，19’h5ε S♪卿ρ．5卿θ’ηr舵oぴ，Na曲vlile。17）Penumadu，D．，Skandarajal1，A．and C鼓ameau，J、L，（1998）l Strainイate e舞ec【s in pressuremeter test玉ng us玉ng a cubo玉dal shear device：Experimems and Modellng曳Cα几θθo∼θch、ノ．，35，2742．18）Peters，、｝．F。，Lade，P．V．and Bro，A．（1988）：S鼓ear band forma− t玉on on triax玉al and plane s葛ra玉n teStS，！4ゴvα1κθゴr1ゴ￠Y’‘7！7ゑ∬加g oゾ So〃‘717〔ノ1∼o（ンた，AST STP，977，604−627，19）Rlce，，1．（1976）：τむe locallzatlon of plastic deformatio脈，Pノ”oぐ、14’h 11π．Coπ9．T11θoヂα．．4ρρ1．ル1θc17．，207−220．20）Rice，J。R，andRudnlckl，」．W．（1980）：Anoteonsomefeaturesof tねeoryoflocalizationofdeformatlQn，ノ．So〃ゴ5〃「 ∼嬬惚5，Great Brita叢n，16，597−605．21）Rowe，｝》、∼V，and Barden，L、（1964）＝Importance of free e騒ds ln triaxia亘test玉ng，ノ」50〃Mθぐh．ノ『o∼〃∼ゴ．01v．，ASCE，90（S八41），1−27。22）Rudn量ckl，」．anδRiceJ．（1975）：Conditionsfortねelocaliza置lonof deforma覧lon頭pressure−se駄sitivedila瞭nt materials，ノ．Mθごノ7、PhJ・∫， So1’ご5，23，371−394．23）Sachan，A．a鷺d Penumadu，D．（2006a）：E旺ect of繍crofabric oa s熱ear be盤avior Qf Kaoli鷺clay，ノ』Gθo∫θ‘h．Gθo一θm，i∼・o，1．ε，1grg。， ASCE，Tentatively accepted、24）Sachap，A。and Penumadu，D．（2006b）l Dralned sわear streng出 propert三es of Kao1霊n clay us玉ng蓋ubr量cated end tr玉ax圭al setup，C‘7〃． Geo’εoh。／．（1n Revlew）、25）Sarsby，R、W．，Kaltezlαls，N．and Haddad，E．H，（1982）： Compresslon of“Free−ends，，d麟ng語axiahestlng，／．Gθo’θ‘11．RE、FE、RENCES E1’g’g、P’v、，ASCE，108（GT1），83−107，26）Szabo，L．（2000〉＝Commenヒs on三〇ss of stroag elllpticity in1）Barden，L。and klcDermott，R．J．YV，（1965）：The use of free ends e茎astoplastic玉ty，／η’，／、So1’ゴ5σηゴS’ηκη’1ぞ5，37（28），3775−3806・ 1職trlaxlahesting of clays，／．So’1ルfθch．Fα〃1ゴ．0ハ・．，ASCE，27）Tokimaτsu，K．and Seed，B、（1987）：琵valuaτlon of settlements i鷺 91（S罫v16），1−23， sands due tQ ea貰簸qu＆ke s賊akま糞9， ／， Geo‘ec1！。 επgrg．， ASCE，2）Bardet，J．P．（1990）：Acompre蝕ensiverev1ewofstralnlocahzatlo靡 inelastoplast1csolls，Co’ηρε’rε1”nゴGeαθ01rπic5，10，163−188。 113（8），861−878．28） Vardoulak玉s，1。（1980）；S員ear band三nc1呈鷺at玉on and s短ear modulus3）Blgonl，D．andHeueckel，T．（1991）：U鷺lquenessan引ocalizaζlon・L of sand in biaxial teSts，／17’、／．ノV∼〃7∼．湘17α乙v．A4θ’h．0θo’nθ‘h．，4（2）， associat玉ve and non−assoc玉ative elastopiast玉c玉ty，1η∼．／．501’ゴ5αノ1グ 103−119． S瑠c’∼’ヂe5，28（2），197−213．29）Ylmsirl，S．and Soga，K．（2002）：Appllcation of mlαomec盤anlcs4）Desrues，」．，Lan1er，，1。and Stutz，P， （1985）：Loca巨zation of由e modeitostudyan玉soξropyofsoilsatsmallstrains，So1Z∫θηゴ deforma竃lon intests onsand sample，だ’∼gi1∼θθヂ’ngE1η‘’∼♂1’θ Foε∼11ゴαが01∼5，42（5），15−26． Mθch傭c5，21（4〉，909−92L萎塾 | ||||
| ログイン | |||||
| タイトル | Hydraulic Conductivity of Nonprehydrated Geosynthetic Clay Liners Permeated with Inorganic Solutions and Waste Leachates | ||||
| 著者 | Takeshi Katsumi・Hiroyuki Ishimori・Atsushi Ogawa・Kunihiko Yoshikawa・Kazuyoshi Hanamoto・Ryoichi Fukagawa | ||||
| 出版 | soils and Foundations | ||||
| ページ | 79〜96 | 発行 | 2007/02/15 | 文書ID | 20982 |
| 内容 | 表示 SOILS AND POUNDATIONS¥IOl_ 47,Nol,7996, Feb. 2007Japanese Geotechnical SocielyHYDRAULIC CONDUCTIVITY OF NONPREHYDRATED GEOSYNTHETICCLAY LINERS PERMEATED WITH INORGANICSOLUTIONS AND WASTE LEACHATESTAKFSHI KATSU ･lli), HIROvUKI ISHI 10Rlii), ATSUSHI OGA¥vAiii). KU +1HIKO YoSHIKA¥vAi+),KAZUvoSHI HANA¥. IOTO ) and Rvolc 'HI FU AGA¥¥,A+i)ABSTRACTTo investigate systematically the effects of electrolytic solutions on the barrier performance of geosynthetic clayliners (GCLs), a long-term hydraulic conductivity test for 3 years at longest ¥vas conducted on a nonprehydrated GCLpermeated ¥vith inorganic chemical solutions. The hydr'aulic conductivity test for ¥vaste leachates was also conducted.The results of the test sho v that the hydraulic conductivity of GCLS Significantly correlates ¥vith the swelling capacityof bentonite contained in GCLs. GCLS ha¥'e excellent barrier performance of' k < I .O x 108 crn/s when the free s¥vell islarger than 15 mL/2 g-solid re_ :ardless of the type and concentration of the permeant solution. In addition, when theresults of the hydraulic conductivity test ¥vith chemicai inorganic solutions wer'e compared to those ¥vith ¥vasteleachates, the hydraulic conductivity of GCL permeated vith chemical solution ¥vas almost the same ¥vithin the electricconductivity of O-'_5 S/m as that permeated ¥vith ¥vaste leachate having similar electric conductivity. The hydraulicconducti¥'ity of GCLS to be used in landfill bottom liners can be estimated by the hydraulic conduct.i¥'ity valuesobtained from the experiment using chemical solutions having the similar electric conductivity ¥'alues, if the chemicalsolution had the electric conductivity ¥vithin = 25 S/m.Key words: bentonite, chemical compatibility, geosynthetic clay liner, hydraulic conductivity, long-term hydr'aulicconductivity test (IGC: D4)ance of GCLS (e.g. Egloffstein, 1995). Therefore, thebarrier performance and chemical compatibility of' GCLSINTRODUCTlor lTGeosynthetic clay liners (GCLs) are efibctive barrielmaterials alternated or combined ¥vith compacted clayagainst electrolytic solutions must be evaluated so thatmeasures can be taken to prevent toxic contaminantslayers, vhich are mainly used as the component ofpresent bottom liner systems in vaste containmentfrom leaking to the outside of ¥vaste containment facilities.The efibcts of a..* gressive inorganic solutions on thebarrier performance and s¥velling of bentonite have beenfacilities because of their relatively lo¥v cost, easy installa-tion, and excellent barrier performance to ¥vater. GCLSare factory-manufactured clay liners consisting of a thinlayer of sodium or calcium bentonite glued to a geomembrane or encased by geotextiles. The barrier perforrnanceresearched (e.g. Petrov and Rowe, 1997; Ruhl andDaniel, 1997; Shackelford et al., 2000; Jo et al., 2001;Shan and Lai, 2002; Katsumi et al., 2004; Kolstad et al.,2004a). These studies conclude that the hydraulicof GCLS is attributed to the s velling of bentonitecontained in GCLs. Sodium betonite swells more thanconducti¥*ity and s¥velling capacity of bentonite is sensitive to the concent.ration and ionic valence of cation in acaicium bentonite, and sho vs the lo¥v hydraulic conduc-tivity value of k<1.0x 10scm/s to ¥vater (Gleasonfrom waste containrnent facilities obstructs the s¥1'ellingpermeant solution, in particular, an electrolyte firstexposed to bentonite dominantly affects the hydraulicconductivity value in an ultimate state. In addition, apermeant solution having a lower concentration requiresof the bentonite, and deteriorates the barrier perform-a longer testmg duration to stabilize the hydraulicet al., 1997; Egloffstein, 2001; Egloffstein, 2002).However, the exchangeable cation contained in a leachateI:iiiIYY]Associa e Professor, Graduate School of' Global Environmental Studies, Kyoto University, Japan (tkatsumi@*nrbox.kudpc_kyoto-u.ac.jp).Assistant Professor, Department of Civil Engineering, Ritsumeikan University, Japan (ishimori@"se.ritsumei_ac jp).Formerly Gradu:aie Student, ditto- (Curremly Okumura Co. Ltd., Abeno, Osaka 545-8555, Japall).Forrnerly ditto (C urrently NIPPO (, o_ Ltd.. Chuo-ku, 'Tokyo 104-8380, Japan).Formerly ditto (C*urrently ¥Vesco C*o. Ltd., Okayama, Oka.vama 700-0033. Japan).Professor, ditto.The manuscript for ihis paper ¥vas received ft)r re¥'ie¥v o l December i, 2005; approved on July 26, 2006,¥Vritten discussions on this paper should be submitted before September 1, 2007 to the Japanese Geotechnical Society, 4-38-2, Sengoku,Bunkyo-ku, 'Tokyo I 12-001 l. Japan. Upon request the cfosing date may be extended one month,,79_ ?!KATSUMI ET AL,.80conductivity value of the bentonite. A CaC12 solutiongradually the hydraulic conductivity of GCLS from I .O xSWF.Ll.ING AND HYDRAULIC BARRIER OFBENTONITF,10-9cm/s to i.OX 108 cm/s in 1-3 years (ShackelfordDeve!op/77ent of Swe!ling anc! Hydr'au!ic Barl'ierhaving a molar concentration of <0.02 M increasedet al., 2000; Lee and Shackelford, 2005b).In most previous studies, the permeant solution usedfor the hydraulic conductivity test ¥vas composed ofsingle-species of NaCl or CaC12, ¥vhich is mainly contained in real leachate from waste containment facilities.Thus, most previous studies have been confined toe¥'aluations from the aspect of the single-species solution.Kolstad et al. (2004a) investigated the hydraulic conductivity of GCL permeated ¥vith the multi-species sohrtionBentonite is primarily composed of the mineralmontmorillonite, which is a member of the smectite family. (Grim, 1968). Montmorillonite is composed of layerswhere a thin crystal interlayer (¥vhich thickness is approximately 9.8 A in desiccation state) consisting of two silicatetrahedral sheets and one alumina octahedral sheet isaccumulated. A trivalent AI contained in the octahedralsheet is partially replaced ¥vith a divalent Mg or' Fe so thatof LiCl-CaC12, NaC1-MgC12 or LiCl-NaCl-CaCll-this crystal layer has a permanent charge deficiency. Tosupplement this char*'e deficiency, there is a hydratedMgC12. However, there are still so fe¥v reports re*"ardin__'exchangable cation (e.*". Na, K, Ca, Mg) bet¥veen thethe hydraulic conductivity for the multi-species solutionthat the barrier performance of GCL,s against electr'olyticcrystal layers. Montmorillonite has a large specific sur-solutions having a complex component like ¥vaste(60-100 meq/100 g), and a high charge deficiencyleachate cannot be systematized quantitatively. Therefore, the hydraulic conductivity for the multi-species(0.7-1.3/leq/m2). These factors contribute to the hi_ hs¥vellin*' potential and lolv hydraulic conductivity ofbentonite to ¥vater. Bentonite used in GCLS typically hassolution must be further in¥'esti**ated. It is also importantface area (770 ml/**), a high cation exchange capacityto investigate ¥vhether the barrier performance of GCLmontmorillonite contents of 65-900/0 (Shackelford et al. ,exposed by ¥vaste leachate having various chemical2000).The correlation between the hydraulic conductivity andthe swelling capacity of bentonite is generally attributedsubstances can be estimated from the results of previousstudies in ¥vhich permeant solutions easily made ofconductivity test ¥vith a ¥vaste leachate, the test duration¥vas short and only one kind of vaste leachate ¥vas used.to the volume of ¥vater molecules that are bound to theclay surface. These ¥vater molecules are considered theimmobile water phase ¥vhich behaves like the solid phaseobstructing the flo¥v. When the volume of bound lvaterThere have also been very fe¥v repor'ts regarding themolecules increases and the immobile water phasehydraulic conductivity for ¥vaste ieachate. To secure thebecomes thick, the eff ctive pore space comprised ofbar'rier performance of GCLS that ¥vill be applied to a realsite, the hydraulic conductivity of GCL,s for electrolytlcincrease in the bound water' means a decrease in thesolutions (in particular, the multi-species solution orhydraulic conductivity of bentonite (La*'er'¥verff et al.,inorganic substances such as NaCl and CaC12 ¥vere used.Although Ruhl and Daniel (1997) conducted a hydraulicfreely fio¥ving water decreases. At the macro-scale, an¥vaste leachate) must be further' investigated. In addition,1969; Mesri and Olson, 1971). The volume of boundit is necessary to systematize the barrier performancewater has traditionally been described in the electricagainst electrolytic solutions and to discuss the adequacyof the hydraulic conducti¥'ity test lvith a chemical solution such as a NaCl or a CaC12 solution, ¥vhich have beenused in previous studies.diffusion double layer using the Stern-Gouy theory(Lambe, 1958; Mitchell, 1993; Shang et al., 1994).This study investigates systematically the effects ofHowever, Stern-Gouy theory has significant limitationsand does not accur'ately describe the crystal interlayerexpansion, which is called the s¥velling (Norrish, 1954;electrolytic solutions on the barrier performance ofGCLs, and discusses the applicability of the hydraulicSposito and Prost, 1982; Lo¥v, 1987; Sposito, 1989;McBride, 1994).conductivity test ¥vith a chemical solution as the prediction method of barrier performance that ¥vill be exhibitedin a real site. This paper shows the results of the lon*"-The hydraulic barrier of bentonite significantly correlates with the crystal interlayer expansion of montmorillonite by the intercalation of ¥vater molecules. There aret¥vo types in the interlayer expansion of montmorillonite;the osmotic s¥velling and the hydration s ¥'elling (vanterm hydraulic conductivity test on a nonprehydratedGCL. permeated vith t¥vo types of solutions as follows;(1) the chemical solutions that consisted of the singlespecies and multi-species of NaCl, CaC12, or KCl, and (,_)Olphen, 1977; McBride, 1994; Prost et al., 1998). Theosmotic swelling occurs ¥vhen the exchange sites in thethe real leachates sampled from ¥vaste containmentinterlayer contain monovalent cations (Norrish andfacilities in Japan. The hydraulic conducti¥'ity test ¥vithQuirk, 1954; Posner and Quirk, 1964; L,o¥v, 1987; Changthese permeant solutions ¥vas continuously conducted for3 years at longest to achieve the chemical compatibilitypointed by Shackelford et al, (1999 and 2000), and thedifference in the hydraulic conductivity ¥'alues for thechemical solution and the ¥vaste leachate ¥vas in¥'es-et al., 1995; Karaborni et al., 1996). If the exchange sitestigated.are occupied ¥vith monovalent cations, the force wherethe monovalent cations attract the interiayer chargin_'¥vith negative electricity is ¥veak so that ¥vater moleculesare easily intercalated. The space of crystal interlay. ers ofmontmorillonite expands ¥vith ¥vater molecules (>40 A),and the bound water in bentonite is increased ¥vith hig:hL 断萎81HYDR、へUUC CONDUCτIViTY OF GCLSIab置e L Review on hydr且u賎c conduc醸vi重y正es症s of geosy臓糠le吐ic ci無y旺ners（GCLs）ReferenceSolutiOnType of GC「LEglogsエein（2001）GCL（Geo【extile−sandwichedben芝o煎es）｝oetal、（2001）GCL（GeoteXtile−Sand、viched granu三arSpeciai tesτing condit玉ons notedDI wa［er，CaCl・ Prehydra【ion，Na ben［iQni｛e，Ca benエon宜e，Sequence of permea｛io11DI water，Liα，NaCl，KC「1，benlonites）CaCiユ，Mgαユ，Znαユ，CuC12，LaC13，Base，AcidKa乞sumielal、（2004）GCLs（Geotexdle−sand、、PichedgranularDI water，Naα，CaCl2， Preねydratio隷orpowderedbentoni仁es），NaC1−CaClユN・lodi員ed beatoni｛eKatsumi and罫ukagawa（2005）GC「Ls（Geotext穀e飾sa11dwicねed granularorpowderedbemonltes）Dlw飢er，Naq，CaC12，Con恥lngs【ressNaC韮一CaC1、，1〉茎S∼VIeacha芝eKolsτad et ai．（2004a）GC取Geote畑e−sandwicねedgra“ularKols乳ad et ai、（2004b）GCL（GeOteXtile−sandwiclledgranularben［onites）ben【onites），Lee and Sねackdford（2005a）Dense−preねydra｛ed GCLGCL（Geotextile−sandwi面edgranularL玉C1−CaCl2，NaCl−MgCI3Lic韮一NaC1−CaC12一｝〉lgC1ユDlwater，Naq，CaC1二，Base，AcidCaC12Prehydra芝ionben【oni【es）Lee aほd Sllackelford（2005b）GCL（Geotext員e−sand、、・ic急ed granularDI water，CaCl二be飢onites）Peζrov and Rowe（1997）GCL（Geαextile−sandwichedgranularbenton玉tes）RuhlandDaniel（1997）GCL（Geαextiie−sandwichedgranularbenton玉tes）NaC1，Synthetic｝〉歪S、VCon自nings｛ress，Prehydraこionleac猶a［eTap water，Base，Ac1d，Syn段1e｛ic Ieac皇1ates，r〉IS、V leacねateSねackelfordαa1、（2000）GCL（Geoζextiie−sand、、「iched granularCaCi二be煎o蝋es）S｝｝an and￡ai（2002）GCL（Geo董ex工韮e−sandw玉ched granularbe【Ron王tes）Vaskoetal．（2001）GCL（Geotex工玉le−sandw1ched granularDI water，τap water，、へc1d，Sea water，脚IS、V leacねateC「aClユ Prehydrationbentonites）萎densまty． The osmot圭c swe豆lil19 Prov玉des the exceHentEαα013！4熊αing ∼hθ的41’躍ぜ1ic Co11ゴ己κ1iviぴoゾ’8εn一hydraulic barrier to bentonite．On t勤e other hand，the∼01zirθhydration swellillg appears in bentonite contain圭119multivε迄1ent cat圭ons（Norrish and Quirk，19541Posner T＆ble王shows the review of previous studies on the＆nd Quirk，1964；Kje1玉ander et al。，1988；Prost e毛a1．，1998）．The interca圭ation of water molecu正es is limited andthe space of crystal interlayers is narrow， becausehydraulic conductivity tests of GCLs．Fundamen芯alfactors a廷ecting the hydraulic con（iuct圭vity of GCLs are（1）quality of bentouite，（2）effective pressure coRfiningmultiv＆1ent cat圭ons attract the crystal interlayer moreGCLs，an（1（3）conceutration and type of chemical sub−stances dissolved ln permeant solutiol1．The（luallty ofstrongly than monovalent ca婁ions．Therefore，the hydra−belltonite used in GCLs is affected by several factorsl tぬetion swelHng cannot suf丑cie【1dy provi（ie t｝1e swe三ling aτ1（imlneralogical composition（in particular，montmoriレhydraulic barrier窒o bentonlte．Eglof￡stein（玉995）meas− lonite content），the surface al’ea aad part宝c豆e grain s量ze，ured由e free swell of sodium bentonite（the exc紅angethe surface charge （ie且ciency， the catiou exchangesites are occupied with sodium ions）and calcium ben−capaclty，and芝he composition＆nd amount of exchangea−tonite（the exchange sites are occupie（i wi亡h calcium ions），ble cations（圭n par重icular，sod量um cat量on）．The quali重y ofand showed over30mL／2g−solid for sodlum bentonltebentonlte ls substantially dependen重on the mlning siteandシ7mL／2g−solid for calcium bentollite，respectlvely．and the crushing Process of the bentonite．In general，the The sweUillg capacity and hydraulic b＆rrier of ben−tonite signi長candy correlates the space of the crys重a1super玉or barrier perforlnance of GCLs量s provided by the玉nterlayeτs expan（led by the illtercalation of watermontmori110nite content，smaller surface area andmolecules．When the exchange sites are occupied wlthparticle grain size， higher surface charge deaciency，higher catlon exchange capacity，and lager amount ofexchεしngeable sodium cation． Lee and Shackelforc至cεし重ions having重he stronger attraction force，the sp段ceof the crystal interlayers is narro、∼・er because waterbentonite hav圭ng the hig紅er qua正ity such as 五ig紅ermolecules are not lntercalated e＆sily。Therefore，if （2005b） 圭nvestigated t紅e impact of benton嚢e quality，bento虚e is permeated with electro墨ytic solu重ion havlngstτonger concentration， the beutonite cannot swe1正su伍cien￡1y and cannot form the superior封ydraulicbarrier．which di任ered in重he montmorilionite contents（77and86％in principal mlner31s of the be飢onite），on the hydrau−hc conductiv圭ty of GCLs，and showed｛hat t難e h量gh ben−tonite quality decreased the 勤ydraulic concluctiv呈ty foII *f'"KATSUh,{I ET ALs2water but adversely increased the hydraulic conductivityfor electrolytic solutions. Katsumi and Fukaga¥va (2005)Table 2. Properties of bentonite in GCL usedcompared the granular bentonite GCLS ¥vith thepo vdered bentonite GCL,s in the hydraulic conductivity,and sho¥ved that the significant difference appeared in thehydraulic conductivity of GCL,s permeated ¥vith stron_gelectrolytic solution. The po¥vder'ed bentonite GCL,s ¥vasmore chemically compatible than the _9:ranular bentoniteGCLs.Second factor, effective pressure confining GCL.s,si**nificantly affects the hydraulic conductivity of CJCL.S.GCLS that ¥vill be applied in bottom liners at ¥vastecontainment facilities are confined by the load of the¥vastes buried. The confined pressure consolidates thebentonite so that the hydraulic conductivity of GCL,s isPFopertyUnitPowderedStandard bentoni ein CJCLSoil particle densityNa ural vater coutentPlastic lintLiquid limit[g/cm;] JIS A 120_?[q/.] JIS A 1203['･ ] JIS A 1205[9/.] JIS A 1205[mL/2 -solid] ASTlvl D5890Methylene blue consumption [mmol/lOOg] JBAS 107 91JIS ,i 8853C_hemical compositionSiO.S¥vell index) ,839lO.O51.0619.533.0l 04.0[','･]59.65Al.O_ s[ /.]l 8 .297_15O.41Fe. Os['/ ]TiO.[?･/.]CaO['/.])_.02[?!.]3.140.462.600.13'lgOdecreased. Studds et al. (1996) investi_g:ated the effects ofK.O[9/.]the confined pressure on the void ratio of sodium bentonite permeated with electrolytic solutions that areN a. O[e/.]P.O,['･/.]*lvlnO[ '.]O Ollgnilion loss[ ･6.15composed of different ionic valence. In addition, Katsumiand Fukagavva (2005) conducted the hydraulic conductiv-ity tests on the po¥vdered bentonite GCLS confined atO1'_56 kPa. Their researches sho¥ved that multivalentcations mor'e significantly decreased the void ratio ofbentonite or the hydraulic conductivlty of GCLS by theconifined pressure than monovalent cations.Lastly, the concentration and type of permeant solution are also an important factor affecting the hydraulicconductivity of clay liners including CJCLs. Strong acidsand bases decr'ease the s¥velling capacity of bentonite, andincrease the hydraulic conductivity. of CjCL,s (.Io et al.,2001). Strong acids promote the dissolving of carbonates,iron oxides, and alumlna octahedral sheets of clayJar'e further decr'eased. The pre¥'ious researches sho¥vedthat the hydraulic conductivity of GCL,s became higherfor the electrolytic solution ha¥'in_g: the stron*'er concen-tration. The multivalent cation increased the hydraulicconductivity more significantly than the monovalentcation according to the comparison that ¥vas scaled by themolar concentration of the electr'olytic solution (Lutz, andKemper, 1958; McNeal et al., 1966; Alther et al., 1985;CJleason et al., 1997; Petrov and Ro¥ve, 1997; Ruhl andDaniel, 1997; Shackelford et al., 2000; Jo et al., 2001;minerals. Strong bases promote the dissolving of silicaShan and L,ai, ,_002; Katsumi, et al. 2004; Kolstad et al.,tetrahedral sheets of clay minerals. These effects increase2004a). However, most previous studies ha¥'e been con-the hydraulic conductivity, but reprecipitation of thedissolved compounds might clog the pore of bentoniteand decrease the hydraulic conductivity of clay liners(Mitchell and Madsen, 1987). Nonpolar fluids or polarfined to evaluations from the aspect of the sin_gle-speciesfluids having: Io¥v dielectric constants such as alcohols aresolution of NaCl or CaCl , and little studies were reported on the multi-species solution (Kolstad et al.,2004a; Katsumi and Fukaga¥va, 2005). It is necessary toevaluate the hydraulic conductivity of GCLS permeatedalso a factor to increase the hydraulic conducti¥'ity of clayliners (Shackelford et al., 2000). Ho¥ve¥'er, no significant¥vith the multi-species solution or' theincrease in the hydraulic conductivity occurs ¥vhen theconcentration of or*'anic chemical compounds is lo¥verpatibility.than 500/0, because the dilution ¥vith ¥vater increases thedielectric constant (Mesri and Olson, 1971 ; Bowders andDaniel, 1987; Fernandez and Quigley, 1988; Shackelford,1994). In addition, an increase in the hydraulic conductivity by the permeation of electrolytic solutions is of*'reat concern to use CjCLs in the sea areas or ¥vastecontainment facilities. When the electrolytic solutioncontaining exchangeable cations permeates into GCLs,the space of cry. stal interlayers of clay minerals (in par-ticular, montmorillonite) is narrolved by the attractionforce of the cations, and the s¥velling volume and thebarrier performance of bentonite are decreased. In thecases of the electrolytic solution having the multi¥'alentexchangeable cations, moreover, the multivalent cationsreplace the monovalent cations occupied in the exchangesites of montmorillonite so that the barrier performancel¥'aste leachate inorder to systematize quantitatively the chemical com-EXPERIMENTAL MF,THODSMateria!s UsedCJCL (Bentofix NPS 4900-1) ¥vas used in evaluatingbarrier performance a*"ainst chemical attack. This is atypical GCL ¥vhere the po vdered sodium bentonite isencapsulated bet¥veen a poly. propylene ¥voven geotextileand a polypropylene non¥vo¥'en _9:eot.extile by needlepunching fibers. The mass per unit area of GCL. Ivasapproximately 4.73 kg/m2, and the initial thickness ¥vas6.0-7.0 mm. The basic properties of these materials aresummariz,ed in Table 2. The evaluations of these properties were based on Japanese Industrial Standards exceptfor the methylene blue consumption and the swell index.s HY[)RAULIC CONDUCT ¥,ITY OF GCLSNa1'nfluent1 o*ve1 02K+8VAcr ylicS042-10'c ylinder' Iaoaeotextile16.1and1 0-2filter paperMembranec a 2+N03-Unit : mMEftluCr>H*-WasteWasteW8steW8steleachate A (pH = 6 50, EC = O 93 Slrn)leachaie H (pH = 6 9 , EC = O 24 S!rn)leachate S (pH = 1 1 8, EC = 4f- S/m)leachate K (pH = 7 7S, EC = 29 3 SlrT1)Flg. 1. Chemical component of lvastc leachatesPennean t So!utiol7sThere ¥vere two types of permeant solutions used; (1)the inorganic chemical solutions and (2) the ¥¥'asteleachates.The chemical solut.ions consisted of the single-speciesor multi-species of the inorganic chemical substances;NaCl, CaCll, and KCl. The ionic strength, I, and thelvall permeameters: GCL specimen was 6 cm in the diameter, andapprox'imately 0.7 cm in the thickuesssoil material used in this test was the po¥vdered bentoniteobt.ained fr'om GCL. T vo grams of the dry po¥vderedbentonite ¥vas dusted into a permeant solution in a 100mL graduated cylinder filled ¥vit.h 90 mL solution. Afterthese '_ g of bentonite ¥vere placed into the graduatedcylinder, this cylinder ¥vas filled up to 100 mL. The graduated cylinder ¥vas carefully covered ¥vithout disturbance,The sample stood for 24 hours before taking a reading.ratio of monovalent to divalent, RMD, were used asLiquid Lin7it TestThe soil mater'ial used in the liquid limit test ¥vas theindicators of the chernical solution. The ionic strength I ispowdered bentonite obtained from GCL. After thecalculated from I=0.5 ciz , where cj and zi are thebentonite lvas soaked ¥vith a permeant solution for I day,concentration and the valence of the i-th ion, respectively. The ionic strength was calculated using only thecations contained in the chemical solution because theswelling and barrier performance (in particular, thede¥'elopment of the electric diffusion double layer) ofthe liquid limit test ¥vas conducted according to JIS Al'_05. The bentonite soaked ¥vith a solution was coveredby lapping with a polyethylene sheet so that the moisturein the sample could not evaporate during the test.bentonite are significantly dependent on the exchangeableHyc!rau!ic Colrductivity Testcation. The other pararneter', ratio of monovalent toThe po¥vdered bentonite GCL was used for thedivalent RMD, is calculated from RMD=c 1/(2cD)05hydraulic conductivity test. The hydraulic conductivity¥¥'here c l and CD are the concentration of monovalent andtest ¥vas conducted according to ASTM D 5084 "Standard Test Methods f'or Measurement of Hydraulic Con-divalent cations. The chemical solutions used in thisstudy ¥vere prepar'ed by parametrically changing theselFig. 2. Apparatus for the h,draulic conductivit)･ test using fiexible-ductivity of Saturated Porous Materials Using a Flexibletwo par'arneters.Wall Permeameter"'. The test ¥vas performed by usingThe ¥vaste leachates used in this study ¥vere sampledfrom 4 vaste containment facilities (A, H, S, and K) inJapan. The chemical component in each ¥vaste leachate isflexible-¥vall permeameters ¥vith a cell pressure of 20-30kPa and an average hydraulic *'radient of 90 in a constantsho¥vn in Fig. 1. This component showed the chemicaltus for the test is sho¥vn in Fig. 2.substances that ¥vere detectable with Sequential PlasmaSpectrometer (ICPS-8000; Shirnadzu Co., Ltd.) and lonspecimen for the t.est, GC L was cut to a diarneter of 6 cm.Chrorrrato*'raphy (PIA-1000; Shimadzu C*o., Ltd.).The GCL used ¥ 'as approximately 7 mrn in thickness,Many other chemical substances ¥vould be contained ineach waste leachate besides the substances sho¥vn in thisfi**ure. The lvaste leachate S had a high pH value, and the¥vaste leachate K had a high electric conductivity.0.87 g/cm3 in bulk dry density, and 100/0 in vater content. Next, the specimen ¥¥'as sandrviched ¥vith the filterpapers and the woven geotextiles, and ¥vas placed in theapparatus. The side of this specimen ¥vas restrained ¥vitha rubber mernbr'ane. This membrane received a hydraulicFree Swe!1 TestA free s¥vell test ¥¥'as performed according to ASTM Dpressure of 2030kPa by filling an outside cell ¥vithwater, so that the solution could permeate through the5890 "Standard Test Method fol S¥ ell Index of Cla)Mineral Component of Geosynthetic Clay Liners". Thespecimen without a leaka*'e on the side of the specimen.For the specimen permeated vit.h chemical solutions, thetemperature room contr'olled at 20 degrees. The apparaThe procedure ¥vas as follo ¥'s. In order to make the !EKATSUMI ET AL.84solutions ¥vere directly permeated from the influent point¥vithout prehydration ¥vith the deionized water. The testplots sho¥¥' the free s¥vell for the multi-species solution.As the *"lobal trend, the free slvell of the bentonite ¥vas¥vas continuously performed for 3 years at longest inorder to investi**ate the long-term change in hydrauiicconductivity and to achieve the chemical compatibility.smaller for' the solution ha¥'ing the str'onger ionicThe flolv volumes, the thickness and the hydraulicconductivity of the specimen ¥vere measured over thetesting: duration^strength. The free s¥vell of the bentonite becameapproximately 7 mL/,- g-solid when the ionic strength ofthe chemical solution exceeded 0.5 M. For the effects ofthe difference in the type of cation, the solution containing KCI affected a gr'eater decrease of the free s¥vell forthe same ionic strength levels than any other solutioncontaining NaCl or CaC12. The free s¥vell for the singlespecies solution of KCI ¥vas appr'oximately a half of thatfor the single-species solution of NaCl. Figure 4 sho vs aResultsFree S}ve!lFigure 3 sho¥¥'s the results of the free swell test lvith thefree swell of the bentonite for the various permeantchemical solutions. This figure indicates the rclationbet veen the free s¥vell of the bentonite and the ionicsolutions of I=0.1 M. This figure sholvs that the electrolytic solution obstr'ucts the s¥velling of the bentonite.strength of the chemical solutions. "Na(X) K(Y)"Also, the single-species solution of KCI obstructs moreseriously the s¥velling of the bentonite than the singlespecies solution of NaCl. Therefore, the effect of thesho¥vn in this figure means the mixin*' of volumetric ratioNaCl solution and KC_1 solution. For example, "Na(2) :K(8)" indicates that NaC1 solution and KCI solution ¥veremixed under the volumetric ratio NaC1 : KCI = 2 : 8. Theopen plots sho¥v the free s¥vell for the deionized water andelectrolytic solutions on the free swell is different even¥vhen the valence and ionic stren th is the same in eachsolution.the single-species solution, and in contrast, the closedO GCL wlth D1 w ter35C] GCLwith N CA GCLwith CaCl,GCLwith I<Cls5r 30o:40O GCLwith NaC CaC12 (RMD = O 20 M=f2)") 25JNext, Fig. 5 sho vs the results of the free s¥vell test ¥viththe waste leachates. Figure 5(a) indicates the free swellvalues for the ¥vaste leachates A, H, S, and K . The ¥vastef8< !::jfii;,/i l1 7I }<(2)::i::;/lA GC with NaC CaC!2 ( MD=a50 M'! ); i; -l._))1' '; fJ(K{4:s;20v GCLwith NaC CaC1hJ ro) K(:))(RMD = I aO M1! )v' 30c GCLwith NaC KC:N {4) K{s)cnv,Q,20O:/ ;/"11';,c¥ti a{P? K{8)Hei8ht of B r - Fre8 s Y8il [m /2g- ;eilidjV !ve on sh top o Bar - Eleeirie e<)rxivetivity [S!mjo 02''///'// ; ;';;o 5,* <// ;'t Se)h< <(5) : i((S)'///= :;,J,90e, ID;LLOoe0408oC5l.: _':110 107/ .:/i//;( '';'1u''//p;;i;'/t(;//.;//'ii,;'',,.t;.;. ;r*o(:, )(5c) 5t*5o jc:,O(J',sZQ(tErQZO( :Z r:Fig. 4. Effect of the electrolytes on the free slvell of polvdered ben*tonite in GCL under I=0.1 M403530:::a25o)c¥Ici20E1535302520IsOQ,Q;e't:11 2;://:;,1No J;*Yoo-solution were mix.-ed under the volumetric ratio r l aCl:KC = 2:8JE14 oli s115- - - a)( -XC5 ,C5L"OX ( r)X c'i･t X o (-O :e- ZZ-O-t)-V( ) 11 V n C ) El ZZZ ::::Z2:(5example, "Na(2):K(8)'* indicates tl]at Na:CI solution and KClo)' '*o : oFrg 3. Relation betlveen tl]e free slveil and ti]e ionic strength forchemical solution: "N 'a(X):K(Y)" sholvn in this figure means tllemix. ing volumetric ratio of r ;*aCl solution and KCI solution: For;; ;+ 21614 i(1 :,lonic streng h forc tion [M]a{6 4/'1///;Oe't5soo5 xl!)**(!)Qo<o {!)(1)(!)Q) e)(ocD: Ie,(1':::g!r'( 1eiv It il v ll [1 V i[ [1 v ll ll1)coJ J :C LLI:o J 10l :2.LU1:,::c: c::s, Q,:F 1Q) Q,:, l:,e,q,:,:), 1:; I I)1Q;Lf):,C(1)t (IC;lOCOC¥COXaLSJ(a) Waste leachatesA H S and Kr ig. 5.(b) Waste leachate K and its diluted solutionsrree s,veil of powdered bentonite in GCL for lvasteeachate' rHYDRAULIC CONDUCTI¥,1'TY OF GCLS7ao700O GCL with D water600600C:] GCLwith NaClA GCLwith CaCi.500::: "oO GC with NaCl-CaC12 (RMD= O 20 M1,2)A GCL with NaCI-CaC12 (RMD= O 50 Mlt2)V GCL with NaC[-CaC12 (RMD = oa M1,2)E_ 400E'1:,:sJ500400300:300crJ2001 oo852001 aoo a2o040885< :::ionicstrength forcation [M]ESS OC l a' o)cD(c;C:; : :oCQ :::Oc V{t :iFig. 6. Relation between the liquid l mrt and the ionic strength forchemical solutionJ ' uJ J(1'Fig. 7.5(D* (:) tQ)(QJ:V(Qe,;: ;!:J IOQ,ExC LlcQ:o(o(1)J5Lf)coC;h:Cil ll:OCLLL!Liquid limit of polvdered bentonite in GCL for was e leachateleachates with and vithout filtration ¥vere used. Thefiltration ¥vas conducted by using 6 pm mesh filter paper.The free s¥vell of the bentonite was the same regardless ofthe filtration of the ¥vaste leachate, and vas significantlymaterial can be investigated approximately by evaluatingthe liquid limit, vhich indicates ho v much ¥vater can bedependent on the electric conductivity of the ¥¥'asteleachate. The free s¥vell shows the lower value for thetest with the chemical solutions. This figure indicates therelation bet¥veen the liquid limit of the bentonite and theionic strength of the chemical solutions. The liquid limit¥vaste leachate having the higher electric conductivity.Figur'e 5(b) indicates the free slvell values for wasteleachate K and its diluted solutions. The open bar indicates the free swell that ¥vas measured immediately aft.ersampling, and in contrast, the hatched bar indicates t.hefree swell that was measured after an interval of I year{I{jthe ¥vaste leachates. The filtration of the vaste leachatehardly affected the liquid limit value of the bentonite, andthe liquid litnit lvas decreased for waste leachate havin*'high electric conductivity.to the pore volumes of flo¥v, PVF. Here, the poreis the immobile water layer formed by attracting watermolecules to the surface of a montmorillonite mineralwith an electrostatic gravitation. The thickness of thisvolumes of flo¥v, PVF, is the dimensionless parametercomes in contact ¥vith a montmorillonite mineral, theimmobile water layer becomes thick by attractin*" thewater molecules to the montmorillonite mineral, then thebentonite swells. Ho 'ever, when water including electro-iI,lytes such as NaCl or CaC12 comes in contact'ith a mont-morillonite mineral, the immobile ¥vater layer becomesthin because the electrolytes are attracted to the montrnorillonite mineral together. Therefore, the swellingcapacity of bentonite deteriorates for the electrolytic{j,solution.{(1) the hydraulic conductivity, k, (2) the thickness ofthe stronger electrolyte (Mitchell, 1993). The double layerbarrier performance of bentonite. When pure ¥vaterjHyc!l'atl!ic ConductivityThe changes of the hydraulic conductivity o¥'er time areshown in Fi**s. 8 to 18. These figures sho¥v the changes ofspecimen, H, and (3) the volumetric fio¥v ratio, Q..*lQi ,layer is si**nificantly related to the swelling capacity and{Figure 7 sho¥vs the r'esults of the liquid limit test ¥vithdouble layer of bentonite becomes thinner by attracting{,in the permeant solution did not appear clearly on theslightly than the ¥vaste leachate that was left alone for lyear. Also, the ¥vaste leachate diluted with the deionizedstronger concentration .The electrolytic solution obstructed the swelling of thebentonit.e for the following reasons. The electric diffusion{bentonit.e was exposed to the strong electrolytic solution.For the effect of the difference in the type of cation on theliquid limit, the difference in the type of cation dissolvedliquid limit ¥'alue.becomes lower for an electrolytic solution having the{of the bentonite contained in GCL decreased ¥vhen thefrorn sampling. The ¥vaste leachate immediately aftersampling obstructed the swelling of the bentonite morewater increased the free swell because the concentrationof the solution vas decreased by dilution. Taking thesefindin*'s together, the swelling capacity of the bentonite{held in a soil. Figure 6 shows the results of the liquid limitregarding the elapsed time, and this parameter' is a valuein ¥vhich the accumulated flow volume is divided by theporous volume of the specimen. Figures 8 to 15 sho vs theresults on the polvdered bentonite GCL permeated withthe chemical solutions. On the other hand, Figs. 16 to 18sho¥vs the results on the polvdered bentonite GCL permeated with the waste leachates.Figures 8 to 10 sho¥v the results of the hydraulicconductivity test with the single-species solutions ofNaCl, CaCi2 and KCl, respectively. The closed plotsindicate the case of usin*' the deionized water, in cont 'ast,the open plots indicate the cases of using the electrolyticsolutions. The hydraulic conductivity of the po vderedbentonite GCL was very low: k =2.2 x 10-9 crn/s for thedeionized ¥vater. Ho¥ve¥'er, the hydraulic conducti¥'ity of*Liquid LinlitThe swell and the hydraulic conductivity of a soilGCL becarne higher for the electrolytic solutions havingstronger ionic strength. As shown in Fig. 8, the hydraulic{*{J KATSUMI ET AL.86Pore volvrnes of now PVF [-]o 20i0-1(T5oso Go 2014e 15050o0o S1 OO1 20i01 O;e 20 s 80 IsoPere vo!ume*sof fle v_ PVF [ ]100 1801 o,"- -!* pi-rFT7; CCr Q ,Z'* ** =1 o's,, C.X{::: :C ?10 'X:i:O:}rT1 o-- ecL with Dl ,!faterl *-20eCLvilth r;_Ct GCL 1'iTth N C- eC'iTth N C(i = O 10(i = O 2SA?*'*D =F10 *':)20;:,.r D = - P* ', )(1 = O Se q,D = * M ': }Is15Test f10dvfat}on : I - 3 ye rs104J':J' :0505ThicknSs--s Yi s me sL r$H'{ s5 frequ8,r-n r?jdr3Lie cor u:SiY :yoososo404eo 'La30a･_o>va-(O : + C}{ )irl_10oo 2040 eO 2080Pofe10140>2010Oeo2e80Pore YC?lvTT s O,0lumes oS Sel', FVF j-1Fig. 8. The changes of the hl.'draulic conductivitl.', tl]e tl]ickness offOO>¥*J PVF {-]Fig. 10. The changes of the hydrau ic conductivitT.･, the thickness ofspecimen anti tlre volumetric fiolv ratio for powdered bentonitespecimen and the volumetric fiow ra:tio for polvdered bentoniteGCL with DI water and NaCGC.1, 11'ith DI Ivater and KCI soh tionso utionPore Yoiumes ef fiew PVF04oios¥velling capacity of bentonite means that the GCL, speci-[*]20300men became thicker and its barrier performance issuperior. The deionized'o 5o10¥vhen an electrolytic solution that could not s¥ "ell bentonite sufficiently ¥vas permeated into the specimen, thecrio t20thickness of the specimen ¥vould be almost the same asIsthe initiai value, and this specimen ¥vould sho¥v inferiorobarrier performance. This figure sho¥vs that the number:of total plots for the thickness, H, ¥vas less than that forOsthe hydraulic conductivity, k. This ¥vas because thethickness of the GCl, specimen ¥vas not frequentlyoso40measured in the testing duration. The thickness could be30obtained by measurin_g: a distance bet¥veen the color filterpapers, whose sides ¥vere colored ¥vith red ink; set up on'L;acvater could s¥vell the bentonite,so that the GCL. specimen became thick by the s¥vellingand sho¥ved excellent barrier performance. Holve¥'er,*o '>30:,o10oO102030the upper and the lo¥ver sides of the GCL specimen using:a micr'oscope. The thickness of the CJCL, specimen ¥vas40PQre voiurne-s ef Ael'i PVF [-]Flg 9. The changes of the l]1.'tlraulic conductivity, the tl]ickness offrequently measured at the ear'ly stage of permeation,because the thickness changed ¥vhen exposing the speci-specimen and the volumetric fl017 ratio for powdered bentoniteGCL with DI watcr and CaCl, solutionmen to the permeant solution. After the early stage, Iittlechange in the thickness ¥vas obser'ved, and the thicknessconductivity value ¥vas k=2.1 x 10-s cm/s when NaCl¥vas not frequently measured. The hydraulic conductivity¥vas calculated using a latest measured thickness. Thevolumetric flo¥v ratios in any of the cases ¥vere almostsingle-species solution of I=0.5 M ¥vas permeated intoconstant over time during the tests. Therefore, the satura-GCL. The electrolytic solution decreased the barrier per-tion of the specimen ¥vas almost constant over time.formance of GCL,. For the change in the thickness ofNext, as sho¥vn in Figs. 9 and 10, the hydraulic conductivit ., for the single-species solution of CaC12 or KCI alsoGCL specimen, the thickness for the deioniz,ed ¥vater'vasincreased from the initial thickness of H=0.5 cm by thes¥velling of the bentonite contained in GCL, and ¥vasreached to approximately H= 1.0 cm in PVF>5. Thisthickness ¥vas larger than that for the NaC1 solution. Thisis because the bentonite cannot s¥vell sufficiently for theelectrolytic solution as shown in Figs. 3 and 4. The largerdecreased ¥vhen the ionic strength of the permeant solu-tion was strong. The hydraulic conductivity values ofGCL, permeated with the single-species solutions of I=0.5 M ¥vere k= 2.1 x 10-5 cm/s (NaCl solution), k= 5 3 x105 cm/s (CaC12 solution), and k･= 6.7 x 10r, cm/s (KClsolution), respectively. rHYDRAULIC CONDUCTl¥,lTY OF GCLSO 20104 *SgO 1Pore vo:urTleef flow. PVP 1-]OeOS7Pore Yo lrr s o2010ele" L_O 40SO:ow PVF [-]o 'OO?O240230120 2402801 *O320i,,,, IoI0 --iot?::H102. OEeGL wi+h Di w ier- GC w;th NaC CBC(1 = D 10 M R D = O 20 M*1):1020eCt w:t NaC C Cf- (1 = O.?O, R' D = O.SO' j- eCLw;th N C C C(1 = 0.10 r.1 R D = I OO ,+ 1 :)Is15Bstir d r ix: n 1 1 - 3 ye ro-Y, :05tTh; ck-;:1 : 1ss .'/as F?1easL e{1 iess fr**' verEtiy th-Ein by ra e eenciLcti* tyo*oso'so'o40O_ 30r* 20LF:a20-=aIJ>30!10>oO 20oSOOPore voi*Jmesof1 OOO40180sO1ew. PVF i-]Pore Ye!ul?1es o20032Gfiow PVF l iFig, 11. The changes of the h _･draulic conductivit) , the tl]ickness ofFig. 13. The charrges of the h)draulic conductivit) , the thickness ofspecimen and the volumetric fio v ratio for powdered bentoniteGCL Ivith DI water and NaCI-CaCl, solution of I=0.1 Mspecimen and the voiumetric flow ratio for polvdered bentoniteGCL with DI vater and NaCt-CaCl. solution of I=0.5 Mo 4010Pore ve Jme-s oBO1 20Pefe volvrne-s o fio v PVF [-]f ow PVF [-1ISO20010*1:! - IQf'40 eo12* 480OC7Co:is_ O 20?4 o::140oO180: : : : '-･rrrr?fl*._,'--.1lo-i 0-3H10'o20ecL wlih Dl w tere = 0.20 t, ,*;- ecL ,Y, h r 3e e8Cli {1 = I oe,*: GCL Wf:h N$C C Cl* l*1eo ,1 RF C; = o so ,41 -)* GC Yl: NaC CaC = {{ = I Oe , , D = I ee lT)IsteF:- Ioo-os:::>oho!20Oloo 4080120 200 240160Pore ve Jme-sof f ow. PVF [-]20'v ' J ' i･,':;1'110oo 20oeO 120aoOo140IsoPore voiume-s of now PVP j-]Fig. 14. The ctlanges of the h,.'draulic conductivit)', the thickness ofspecimen and the votumetric flo,v ratio for powdered bentoniteGCL with DI water and ¥. *aCI-CaCl. soliltion of I=0.2 Mspecimen and the volumetric fiow ratio for powdered bentoniteGC.L with DI water and NaC.1-CaC12 solution of I= 1.0 Mthe hydraulic conductivity of GCL permeated withon the hydraulic conductivity of' GCL, the hydraulicconductivity value became high ¥vhen a large amount ofCaC12 was contained in the permeant solution (namely,NaCl-CaC12 multi-species solution having a certain ionicstrength, the permeant solution havinga the strong ionicRMD ¥vas small) under the lo¥v ionic strength as shown instrength decreased the barrier perfor'mance of GCLsuch as calcium attracts the crystal layer, ¥vhich hasnegative electricity, of bentonite more strongly than agreatly. This reason closely relates to the above-describeds¥ 'elling capacity. That is, when the ionic strength of the;>soFig. 12. The changes of the h,_'draulic conductivit･.', the thickness ofNaC1-CaC12 or NaC1-KCl. As shown in Figs. Il to 14,i* ,****-***. :i40Flgures 11 to 15 shows the results of the hydraulicconductivity test ¥vith the multi-species solutions of{2 - 3 yearsso40oduratienTr :d(ness hvas fT Bas red i -gs reqver :'/ jh :'-n r,ldr8v; e eerK Lcll' ty* 3 )o_* ZososoeT stin10Frg 1 1 . In general, the multivalent exchan*･eable cationmonovalent exchangeable cation such as sodium, andpermeant solution was stronger', the bentonite could nots vell sufficiently hence the bentonite specirnen sho vedinferior barrier performance. For the effect of the mixingdecreases the swelling capacity of the bentonite because itbecomes difficult for ¥vat.er rnolecuies to enter bet¥veen theratio RMD of the NaC1 solution and the CaCl, solutionered to deteriorate when a large amount of CaC12 iscrystal layers. Thus, the barrier performance is consid- KATSUivll ET AL.88Pore voivmes of fiow- PVF {-iior*Pore veivrnes of ow. PVF [-]O 20 SO 100 140; r; lc-4080i201 o'Ei: i:: ' Io>0::ovv oF'-'*10sOS 2So'{r: : r :rr:L L !::l;10 "' , ,,io s-leecL v,Ith waste !e cbate ,e ( itered}4- GCL '/1Sh ,, s e {e eh te A10(: 2'oecL 1'iit" Is5F; Q'swfth w ste Isach SeoTe t ng dLJ? :x)n : 2 ye rsTr :kr)e-sso:: 4040: 3'oe;a20a15> io40 80 I0BoPore Ye vmes o{ f:ol'i, FVF i-)140t n trydrJ x; corx uotF, tyso2.0eJ.*,_(o 20vS s measuT;d 18ss fr querlo50a' '(f,itef d)+ GCL with was'e * cbat* K0_5:50o- GC10ote H { iteredjl - GCL wfth Yia5 e :8ach tB S (nlt redjC with ,ias e leeeh;te S,,,o- Io.･/ ste IB eilHF GCL w:th IYas e le chate h20e'{s300 3502001 O-e)_1!O 501 ooio>o1 20o soooSoPe,e voiumes ot200250soo 350ow, PVF l-]Fig. 15. The ehanges of the lu_'drauiic conductivit)', the thickness ofFrg 16. The chano*es of the h¥.'draulic couductivit¥.', the thickness ofspecimen and the volumetric fiow ratio for polvdered bentoniteGC_L vith Dl water and NaClKCI solutionspecimen and the volumetric fiolv ratio for powdered bentoniteGCL with vaste leachates A, H, S, and Kcontained in the permeant solution. Ho¥vever, under' thehigh ionic strength as sho¥vn in Fig. 14, the hydraulicconductivity value became small adversely ¥ 'hen a largeamount of CaC12 ¥vas contained in the permeant solution.In addition, from comparison of the hydraulic conductivity values for the NaCl single-species solution and theNaClCaC12 multi-species solution of I= 0.5 M in Figs. 8and 14, it can be stated that the hydr'aulic conductivity forthe NaCl sin.ale-species solution is much hi_ :her than thatfor the NaCI-CaC12 multi-species solution. These findingslead to a conclusion that sodium becomes more sensitiveto an increase in the hydraulic conductivity than calciumwhen the ionic str'en_g:th increases. As the proof of thisconsideration, sodium decreased the free s¥vell of ben-tonite more than calcium at a high ionic stren*'th assho¥vn in Fig. 3; the free s¥vell values ¥vere 6.5 mL/2g-solid for NaCl solution and 7.9 mL/2 g-solid for CaC12solution at I= 0.5 M. In part, the hydraulic conductivityvalue in the case of per'meation ¥vith NaC1-CaC12 solutionhaving I=0.5 M and RMD= 0.2 Mi/2 as sho¥vn in H 13¥vas much decreased at PVF>280. This is because theGCL pore might be blocked by the migration of thecolloidal matters contained in GCL. On the other hand,Fig. 15 sho¥vs the hydraulic conductivity of GCL permeated with the multi-species solution of NaCI-KCl. Inthis figure, the hydraulic c.onductivity for the single-Pore voiumes o ilow. PVF {-i101a so1 OO 200SO^o 501001 SOi300 350･50300 3soIo::c:v s loI0:E10 *2.0u Is0 , Ie'; 05o5_ols 40= 3a_*12.0"'**.=a>sloo1502eOPore Yotunles of f ow PVF [-]F g 17. Tl]e changes of the hl.'draulic conductivitl.', the thickness ofspecimen and the volumetric flol ' ratio for powdered bentouiteGCL Ivith vaste knchate K and i ts diluted solution ( x 1.5 and x2.0)in the type of cation appeared in the hydr'aulic conductiv-ity value, even ¥vhen the valence and concentration ofspecies solution of NaC1 and KCI under I=0.1 M iscation dissolved in each solution ¥vas the same.shown as a reference value. When the permeant solutionconductivity for KCI solution ¥vas highest, and theFigures 16 to 18 sho¥vs the results of the hydraulicconductivity test ¥vith the ¥vaste leachates. Figure 16shows the hydraulic conductivity of GCL permeated withhydraulic conductivity for NaCl solution ¥vas lo¥ver thanthe ¥vaste leachates A, H, S, and K. The hydraulicthat for NaC1KCI solution. This may be due to theconductivity values for the ¥vaste leachates A, H, and Swere as lo¥v as k< 1.0x 10 8 cm/s, and in contrast, thehydraulic conductivity value for ¥vaste leachate K becameof I=0.1 M was permeated into GCL, the hydraulics¥vellin_ ., capacity for the electrolytic solution as sho¥vn inFigs. 3 and 4; namely, it ¥vas because the KCI solutionobstructed t,he s¥velling of the bentonite more seriouslythan NaCl solution. It ¥vas concluded that the differenceas hi_g:h as k= 6.4 x 10-7 cm/s. This was because the wasteleachates K had a higher concentration than any otherj 89｝｛YDR．へULIC CONDUCTIVITY OF GC「LS 100 Pore volurnes o『移ow PVF Erl1。70 10 2。 30 4。 50 6G一851αさ工“GCい，V、Lhx4dr獄ξ｝dwa5【e陸ξcna幅K（轍εrεの噸h GC」w壇h x8dllL詫3d wa5に匠設d旭監a K（篠ヒerεd） 20門岱rGCLWヒhx16qぼεdwastel5憾dr凄憾Kσ誼erεd）E→ロ』GCL、v、竃hx32d置 戚醜wasteleヨ鵬にK（f・磁r館）燈r GCしW、匙hx64d言戯eGwa5【e海aα旧ヒeK（硫ereのo− 10Testi㎎d甑欝匙｝on 2years1・・職翠∼lll 諜§ ！甚1・・ノ 1窪 05Dl waterNaCI so［utionCaCb＄o！utionKCI solutionNaCトCaClっsoiutionNaCトKCl so臨bnWa＄te leachate〔）i賦ed waste Ieachate丁園㈱SSW尊號a購d睡ssf剛鉱晩吻σ「蹴C図戯M亡y− 0 50田 じ o0 20 40 60 80 歪00 ∈ヨectrlc condcutivitity of inぎluent ISlm】鳴 403山ε 。 30．§9巷著2DFl9．至9．Comparison…n揺1eelectricconduc症ivltyof e撮uenねccordi購9吐oASTMD6766……o苔 1D〉i臓翁uen【 and 00 1G 20 30 40 50 60 Pore yo塁り露短S D”low PVF 日F韮g．18。 The d臓nges of the hydraUic conductiviIy，霊he thicl｛ness ofof GCL．In any testing cases，t量1e hydrau星ic conducξivityof GCL was evaluated as approximatelyん撚2．0×10−9 specimen 段nd the vo雇umetric 行ow rat韮o for powdered ben吐onitecm／s in PレF聯7，bu重the hydraulic conductivity increased GCL wlth waste ieac掴症e K a賑d its diluIed so藍uIio臓（x4。O to×gra（iua正ly over t圭me in Pレ労＞7．For the waste leachate 64．0）wlth the dilution m＆gni長catlon factor of4．0，ln particu−lar，the紅ydraulic conducti、・ity increase（i from左；2，0×1each飢e；the electric conductivity values were O．24S／m（waste le＆chate A），o．93S／m（waste leacha重e H），4，17S／m（waste leachate S），and29．3S／m（waste leachate K），respectively。Tぬe nltrεしtion of the waste正eachates har（墨1yaffected the hydraulic conductivity value of GCL数ydraulic conduct量vity apPeared in the cases of using tぬewaste leachates having the e豆ectric conduct宝v主ty of聯8．58wαste leachate K w圭｛hout負1tration．The reason for thisS／m，which had a value for the waste leachate wlth thewas because the GCL pore speclmen migh重be blocke（1bythe colloidal matters contained in the waste leachate。dilution magni且cation factor of4。O．rθノ7ηinα！ion Cl−iオε’婚iα（λブ1Loη9−Tθη11乃rアゴ14αμ1iぐCon4己κ一がvめ7Tε3∼I7and王8show the hy（irauiic conductivity of GCL per− As a general crite11ia to termlnate the hydraulic conduc−tivity test，it is necessary to satisfy the fo至10wing threeFig。17，the closed circle plots indicate a test玉ng case thatpoints；（玉）the hydraulic conductivity value圭s stab正e overwas conductecl immediately after sampllng waste Ieacha重etime，（2）the volumetric How ratiQ ls approximately l，andK，εしnd on the other halld，the open circ正e plots in（iicate a（3）the pore volulnes of f董ow of aξ1east20r more are per−test圭ng case that was conducte（i by using waste leachate Kleft alone for l ye＆r from lts sampling．The difference of lorder magnitude appeared in the hydraulic conduct重vityevaluate（i from each testing case．Probably，the organicsubstances contailled may be deteriorated by至eaving thewaste正eac負ate alone for l year．For the effects of themeate（1into the bentonlte specimen。It is also one of芝heimporta互1t criteria to establlsh the chem量cal equl1量briumst叙e before the test is terminated（Bowders，19881Sむack−elford et al。，1999）．Shackelford et a1．（1999）suggest t数atthe electric conductivity ofthe inHuent and ef巳uent can beused as indicators of t紅e chemical equ圭libriunl state，andd童luted solution on the ぬydraulic coHductiv量ty， therecolnlnend tha重（4）the electric conduct圭vity ratio of thehydraulic conductivity for the（ii正uted waste leachate wasinHuent an（1efHuent fall with量n O。9−1．l before the test is王ower than that for the und玉1uted ∼vaste leachate，terminated．ASTM D5084explains in detail about theHowever，the difβerence beξween the dilu塗ion mαgnihca．criteria described in the above−mentloned（1）to（3），ontion factor of1．5an（i2．O h段rdly＆PPeared in the hydrau1−the other hand，ASTM D6766“Standard Test Methodic conductivity value．The test呈ng cases of using the wastefor Evaluation of Hydrαulic Properties of GeosyntheticIeachate dilute（i Yvith more deiol1玉zed∼vater is shown inClay Liners Permeated with Potelltia旦y IncompatibleFig．i8．This且gureshows＆nimpressivepro負1e。Whenthedilution maglli丘cat玉on factor was more than4，0，thelong−term change appeared l鮭he hydraulic conductlvity多CONSIDERATIONSIeachate was use（i for the書est without且1tratlon。Figuresmeated wi宣h was重e leacha重e K and its dlluted solution．王n，Lpermeated with芝he e至ectric solut玉on having＆low concen−tration． In this study， the 豆ong−term change of thedecreased in PVF；250as sho∼vn in the testing case to usemauce of GCL might be evaluated excessively due toc圭ogging of the colloidal matters when the raw waste韮Therefore，辻was necessaly to be careful for the long一毛erm cぬange of the barrier pel齢εQrm＆nce w勤en GCL wasHowever，出e hydraulic conductlvity of GCL w＆s muchTherefore，it should be noted重hat the barrier perfor−萎10−gcm／stoえ；8．7×10㎜gcm／sveryslowlyin2years．L呈（lu圭ds”explains the cri｛erion regarding（4）。 Most hydraulic conductivl重y values obtained in thisstudy had already satisfied the criteria described in ASTM 90KATSUMI ET AL。＿ lo一の◇のA△セ口繍 10『PM＞）O GCしwilh Dl wate「口 GCLwlth NaC『◇ GCL with Caαっ△10おoコoq△ GCL wi匙h KCloo1αプコ10¶ε◆GCLwit贈aC1−Caα2（RMD司OOMtf2）A GCL w詫h Naα一Kα（Na（5）；K（5））雲ロコで＞ヱ讐盆番・oO GCL wlth Naα一Caα2（RMD＝020M∼12）圏 GCLwlth Naα一Caα2（RMD＝050M笠ノ2）1α902 04 06 08 て〔）lonlcstrenglhforcation岡F童9・20・Rel戯ionbeIweenthehydraulicconduαM重y鋤d芝heionlcs｛reng重hforchemicaisolu芝ionTable3・Res醸soflong・重ermllydraulicconduαivi重ytes重forpowderedbenIoniIeGCLPermeant solut重QREndoftes巖照ChemIcal compoundsType of solutlonDeionlzed、vaterNasOlutionCa sok星証on11Mlノ∼ハζ∫Z） Na聖 conc， Ca” conc． K学 conc．［M雛1 ［Ml 【MI ［へ｛］0．000。100、250，500．200。501、00K soIUtlonNa−Caso1面o陰0．100．250．500。100．三〇りooりqり0．000。000、00ccQりつc・0．200．50〇、101．000．200．200．200．500、500．500、200，501．00王．00Na−K solu［めa0．001．000．200。501．000．200、501．001．000．圭0劣0、50∼Vasτe leac｝1a【e．AWaSteleacha！eA（飲ered）Wasleleac鮭ateHWaSteleacha【eH（食1tered）、Vas［e｝ea（：hateS、VasteieacぬateS（f灘tered）りc0．000，200．50玉．000，000。000、000．000．000．000．050．110．150．080，170．260、130．300．500．190．440．780．100。500．00000、0，000、000．玉00．250、500．00G，000．000．040．020．010．080．060．030．220．180，…30．450．390．310．000、000．000．000、000．000．000、000、000．200．501．000．000．000．000．000，000．000、000、000．000．000．000．000、100。50pH EC［一1 ［S／ml7．045．68TimelyearlPI乙F pH ECl−l H ［S／ml 0，02く320．66 8．0518、43く259．17 8「0742．10く20．31 んlcm／sl2、、24x10＝918．0王4．61×10鼎94！．80玉．41x10皿s17．8韮1．83x10−s5，425．368．568、889．2476．80く158．61 一16．85く藍 三2、22 8．1935．90く1 5．15 ＿62、40く123，72 6．5766。002．80x10づ7．9321、60＜2129．04 8．1724．203、30XlO−s7．577．3749．10く1 5。G795，40く127．69 −11、48く369．69 7．1611．311、ア0×10而s14．22三．52×10略17．8夏6．40×10−9フ、59144．85 7．692、13×10づ5，25×10柵52．76×10鼎66．69×10』614．OIく3！10、70 6、65I6，43く362．97 6．8820、10く3213，80 7．432王、403．12×10糟823．80＜3157、58 7。5126．201．37x互〇一s1，75×10『呂24．60く3互72．10 7、1129．6040．40〈3296．93 8．6143、502．55×10㌣947、60＜392．95 7．4948．804，37×10−854．30く394、74 7、0459，402。86×10憎s71，30く2135．13 7．1078．008．17XIO−885。20く2145．29 7，2982．708．63×10楠s92、40く284．99 10．95く218．20 8、227．1099．003．王2x10一胃11．424．26x｝0』91，47X lO−91．16×10榊5〈127．97 ＿〈210．26 7．94豆．32 0．25く211、04 8．482．031、00x王0府9 0．93く2！4、2．392、384．274．231、96x10−95．986．50128．806、917．977．85 0．2429 8．08 0、79＜214．34 7．7211．79 4．17く210、87 7、7211．74 4．08く211、28 7．47i．95x10−92、17×10”91．89XlO−97、757．3i29，30く2315．59 70329、806，38×10鼎7WaSteleachateK（魚eredソ29．70〈2322．04 7．6429．406．16x10学7Wasteieac駐ateK（飛ltered）こ6，4030、30＜2210、99 7．4229．玉05．三9x10−s ×1．5d玉luted（負1【ered）26、3120．50く252．92 20．601．23×10榊s ×2di1厩ed（丘ltered〉ユ6、256．356。4515．76I．09×玉〇一§、、1aste leachate K ×4d1luted（翫ered）肝 x8dlluted（丘ltered）ユ x16diluヒed（最1tered）2 ×32曲ted（飾ered）ユ x64diluted（負ltered）ユ6．466．396．547．4816．26＜260．67 8、57 8、58く250．01 8，078。538．66×10憎9 4．34＜23王叫49 8．101、20x10−s 2．32く233．19 8、、394．242、25 1．46く230．20 8．531。558．14XIO−9 0．60く217．62 8， 242．135．50×10柵9互．圭7×10榊sused immediately after sampllngusedaf｛erlyearfromsampling韮 fHYDRAULIC CONDUCTIVITY OF GCIS91- 10-7c"_v1 O -3o_i>'$(>>o:; I O10476 835 9; ;128 895 4i O 5;;B1::1 0-6c:c:oo::::1):>:Heig t of Bar - Pree swe!i [mL/2g-soiiid]Valve on the top of 88r - Eiectric condvctivity [S/rn]';47 6i O-B>10:c:a1 O-9oV::(QoooO :i zzi g (Q cT ('dO :!(U(' trQCQa a acQ:rQa)e)OCQ2:o( zo( zc :;a,oC554 3'40 4;;/////.o';O 02e)+co' ; ; ;:.iO-':;c5Lf):,::,tf)oo a:o(oO oo) aoQ(:oo(oC:tr)a:Z:o((b) J = O.5 M(a) I = O I MFig. 21. Effect of the electrol .'tes on the h)･draulic conductivit¥. of GCL: note that the electric conductivit¥.' of each solution is quite different even ifthe ionic strength is the same. In actualit¥. , the electric conductivity values of the solutions of I = 0.5 M Ivere 76.8 S/m (N 'aCl solution), 35.9 Slm (CaCl. solution), and 95.4 S/m (KCI solution), respectiveh.'D 5084. However, in the cases of using the permeantsolution of the lo¥v concentration, the hydraulic conductivity values increased gradually as shown in Fig. 18. Thebarrier performance of GCLS must be evaluated inconsideration of a long-term change of the hydraulicconductivity. Figure 19 sholvs the electric conducti¥'ityof influent versus effiuent at an ultimate state of thehydraulic conductivity test. According to ASTM D 6766to achieve the chemical equilibrium, the hydraulic conductivity test is required to be continued until the ratio ofthe electric conductivity of' effiuent over the electric conductivity of influent falls into 0.9-1 . I . Figure 19 indicatesonly the monovaient cations of NaCl and KCI made thehydraulic conductivity as high as k= 1.2 x lO5 cm/s atI=0.5M. In the hi**h ionic strength of ; 0.5M, thehydraulic conductivity values to the single-species solution ¥vere approximately k = I .O x 10 5 cm/s regardless ofthe difference in the valence of cation. However, themulti-species solution composed of the monovalent anddivalent cations increased the hydraulic conductivityvalues to k=i.OX 10-7 cm/s in the same range of theionic strength. Although the hydraulic barrier of bentonite to the single-species solution has been traditionallyexplained from the thickness of electric diffusion doublethat the most hydraulic conductivity tests conducted inthis research satisfy the termination criteria of ASTM D6766. Most tested GCLS achie¥'ed a chemical equilibriumlayer' and the size of hydrated ionic molecule, thehydraulic conductivity to the multi-species solutioncondition before the tests were terrninated.kno¥vled**e re*'arding the hydraulic conductivity to theSunllnaly oj'Long-Term Hydrau!ic Conductivity TestThe results of the long-term hydraulic conductivitytest are summarized in Table 3. This table shows theelectrolytes on the hydraulic conductivity of GCL undercannot be simply predicted from the traditionalsingle-species solution. Figur'e 21 sho¥vs the effect of theproperties of the permeant solution used, and the resultsat the end of the hydraulic conductivity test using its solution.{Figure 20 shows the relation bet¥veen the hydraulic,;conductivity of GCL and the ionic strength of thechemical solutions. The open plots indicate the hydraulicconductivity for the deionized water or the single-species{solution, and the closed plots indicate the hydraulic{,conductivity for the multi-species solution. The hydraulic;{{I=0.1 M and I=0.5 M. The hydraulic conductivity ofGCL fo ' CaC1, solution of I=0.1 M ¥vas referred to thedata reported by Lin et al. (2000). The hydraulic conducrivity for the deionized ¥vater was as lo¥v as k = 2.2 x 109cm/s, in contrast, the hydraulic conductivity for theelectrolytic solution ¥vas higher than that for' thedeionized water. For the hydraulic conductivity to thepermeant solution of I=0.1 M, the KCI solution increased the hydraulic conductivity of GCL more slightlythan any other solution. On the other hand, the electrolytic solutions of I=0.,5 M sho¥ved that the hydraulicconductivity of GCL permeated with the electrolyticsolution became higher when the ionic strength of theconductivity with the single-species or multi-species solu-solution was stronger'. The infiuence on an increase in thehydraulic conductivity significantly differed bet¥veen thesingle-species solut.ion and the multi-species solution.siderably higher than those ¥'ith the multi-species solu-tion containin*' only monovalent cations became con-tion containing divalent cation for the same ionicstrength.Most of the hydraulic conductivity values to the multi-Next. Fig. 22 shows the hydraulic conductivity of GCLspecies solution ¥vere lower than those to the single-spe-permeated ¥vith the ¥vaste leachates. As sho¥vn incies solution, and these values ¥ver'e smaller' than k-= I .O XFi**. 22(a), the hydraulic conductivity of GCL became107 cm/s. In part, the multi-species solution containinghigher for the ¥vaste leachate having the higher' electric lKATSUh41 ET AL.92conductivity. This reason can also explained by the s¥velling capacity of bentonite as sho¥vn in Fig. 5. On the otherby leaving the ¥vaste leachate alone for I year.hand, Fig. '-2(b) sho¥vs the hydraulic conductivity forApp!icahi!ity ofEva!uatioll Mlet/70ds }vitll Chenlica! Inor-¥vaste leachate K and its distilled sohrtion. The hydraulicganic So!utionsIn this subsection, the results obtained by using thechemical inorganic solutions lvere compared lvith thoseobtained by using the real waste leachates. Here, thechemical solution means the permeant solution that waseasily made of inorganic substances such as NaCl, CaC12,or KC1. All experimental data obtained in this study ar'esummaTized in Table 4.conductivity for the diluted waste leachate was lowerthan that for the undiluted waste leachate, and ¥vasdecreased with the increase of the dilution magnification.In addition, the waste leachate that was left alone for 1year from sampling sho¥ved the lo¥ver hydraulic conductivity than the ¥¥'aste leachate immediately after sampling.The organic substances contained might be deteriorated1 OI O e(,)v_v_! ( 10>:; 10 f:>o:;Oo:el:;:'c:ooae) I O-::=o IO1:'I> 10:hI 10<5 c/)I hco v'o;Lf)cccio :l:o :0'c:FV fi ll :z:oo f] Ilhaio r(c[1 llf::( :oUJ J :l:oLIJ 810cLLuo n liJl:)1Q, Q,(Lr)l :,(1)1:)1):: c¥1:: ,t : t)1:,Ls) 1:,e)Q,a,q,::::co1lc:)(OC Jcf) ( )xJ c LIJ(a) Waste leachatesA H S and K(b) Waste leachate K and its diluted solutionsH .'drau]ic conductivrty of CCL forFicF. 22.vaste knchateSummary of results for pol"dered bentonite GCLTable 4.Permeam solutionTesting FesliltsChemical compoundsI RM:D Na conc. C_a2Type of soiution [lM] [lM *2j [iM]Deionized ¥vaterNa solu ionO.OOO.02O . 04O 05O.060.08O 10O_ ,_OO.2SO 50l .OOC_a solutionK solutionoc-O.OOO 040.08*f*0. I O'-f-O.12c=O. 1 6O.OOc:'c*f_cc]coc:.O.200.50O.OOO.OOO OOl OOO . OO0.02ooO . 04*f_O. I OO.05O.06O_08O.10O.20O.25O^501 .OOc.,':*c_,c:'c'c=f_:*0.20O_40O.501 ^OO2 OOO.OOO.OOO OOO OOO_OOO.OOO.OO0.00O OOO.OOO.OOO.OOO OOO OOconc. K conc.[ivl]O OOO.OOO OO0.000.00O_OO0.00O.OOO.OOO.OOO_OO0.05O. I OO 25O.50O OOO.OOO OOO OOO OOO OOO OOO OOO.OOO.OO[lv. 1]pH EC Free s vell. Liquid limit Hydraulic cond[ - I [S/m] [InL/" sol d] [o! ] k [cm/s] "33 O23 2619 5 2 24x lO 9OO7 . 040.0,_O.OOO.OOO.OO6,686.364 2069.91O . OO5,7)1 ,_ 09O_OOO.OOO.OO5.665.68l 5 .095 . 4434.30O . OO5.4,42. I O8.lO .OO5,365^18766 5111 '-6,09 O8.07 97 815 O98.5OO^OOO.OOO.OOO_OOO.OO050. I O8.568 889,247.577.366,89O_ 1 26_81O_ 1 66.687.937 747.577.377.32O . 04O.08O.200.40O_501 .OO2 . OO8 . 061 8 .4380l 29. I O9.0316.8535.9062^405 . 059 7612.0613.5517^7719,018.518.016.015_991185.0136 2l 14-92.13 x 10l.83 x lO s5 25 x lO '2.80 x lO )9.27 27,l7. l41.lO5,049. I O5.04*54.0169.80I 41 x lOsll.l2 1 _6095 ^ 404 61 x l0 9181.03.30 x lOs)_.76 x lO66 69 x l0 6Table 4^ coutinued on next page セ93｝｛YDRAULIC CONDUCτIVITY OF GC「LS…hble4．con韮inuedfromprevlouspageTes“n黛 resu玉tsPermea瓢soluτionCねelnicalcompounds Free swel1 王jquid limit H｝『draulic cond、1 RMP Na一conc．Caユ甲conc、K廟conc、 P｝｛ EC ［M】 ［M1 ［MI 卜1［S／m】 lmL／29−solidl ［％】 たlcm／slTypeofsoiutionlM】 ［M匪〆3】翼a−Ca solution0．040．070、05 0．200。05 0、500、05 1．000，090．10 0、200，050．10 0、500．玉10．000、040、020、10 1、000．150、010、20 0．200．080．170．080．20 0、500．260、130，300．500．20 1．000．50 0．200、50 0、500、50 1 ．000．191．00 0。20…0、10 つつ0、440．780．040、080、100．120、10 」つ0、三60．50 0c0、、501．00 0．501．00 墨．00Na−KSdutlon0．王0 コつ0．10 つ￠0．10 フつ…韮き妻妻韮0．020」010、060，030．220、180．130、450．390，310、000．000．000．000．000、000．000、000．000、000．000，000．000．000．000、000．000．000，000．000、000．160．120、100、080、040．5014．017．Ol9、01、70×10−s9．5 11、48 14．0110、5 16．4314．01、52x10蘭s6、40×10甲9 20、108．2184、玉3、12×10一＄ 23．808．5179、「71、37x10略 24．60 40．4010．0玉80、41．75×王〇一sB1、68．02，、55×10瞭9 47、608。2127．74、37×10酔s 54、308、5127．72、86×10−s 7玉．307、2122．98．17x10酬s 85、208、0i1368，63x10−s一一 92．408．2102．23，12x10一薗7．23 1！．4711、97．35 王1、167，59 io、9513、0147．68 10．7314、27．83 10．5416、94．26×王0｝9，05。98 王28、804、8WasteleachateA6、50 0．24WasteleachateA（丘ltered）6．91 0，25Waste！e段chateHWasteleachateR（創tered）7．97 0、93、Vaste leacねate S11，79 4．17V》as［eleacむateS（f灘｛ered）11．74 4，0828、028．026．026、023．025．07．85 0．791、16x10僧5580．61，47×10−9629、91、00×10簡956521、96×10−9562、31，95×10皿9523．52．17×10｝9517．71、89×10−9∼Vaste leac｝1a【e K7、75 29．36．0165、56，38x10一「WasteleachateK（丘1tered）IWasζeleachate駁（脈red）ユ7、3玉 29、75。9165、66、40 30，307．06、16x10｝「5、19x10−s ×1．5diluted（負ltered）26．31 20．507．1玉．23x10備s ×2diluted（自ltered）ユ6、25 16、268、5I、09×10FS ×4diluted（51tered）26．35 8、，5812．i8．66×10−9 ×8dlluエed（自1ζered）26．45 4、34l7、41、20x10欄8 ×玉6dil凱ed（負ltered）26、46 2．326．39 1、46 x64diluted（翁ltered）ユ6．54 0、6024、727．529，51、17×10−s ×32diiuted（負ltered）ユ814×10−95、50x10榊9usedimmedla芝elyaftersamplingused after l year from sa臓1Plings700600 1＿ 104 働、 O≧ 亀，鐙③、9500Oの鋤ノ○ ○￡ 10『5Oメ 催oむ㊤彗．だ 400∈○呈 噛〇一ア2oσ 3005コ 200、．爵joo OO Oも ○oコ、A−h8re x瓢Free5㌔ve目〔mし／29−solldl0 10『9着き0工 1α鴇5 10 15 20 25 3035 Free swell lmL129・solid】Flσ23．嘩0 1α5藍 y＝LlqUld II醸t［％］0 ⑧のy酋206x （R篇0．97｝びo○どRelaIio“between芝heliquid疑mitandthefreeswell020 40 60 80 100 120 140 Eヨectric conduCtM鞍 IS！m】Fig。24．Rel郎ionbetweenthehydr旦騒licconductM｛ya臓d象heelectric conduc症ivity KATSUMI ET AL.94ate the hydraulic conductivity of GCL from the ionic1 aOi O-sv_qq, h r>o i a'T]hn o ::):,c:I O-G,,c:,,>O-9x ;; Fr e Ewe:; [mL;29 sQi:dj', O bse>r rstren*'th, ¥vhich is the parameter considering the type andconcentration of the solution, is not practicable. In orderL e p( ix bJ) j :;QB3)y s: Hydreu;io co{ItiL;c v'ty_ iOot)le)3.0= -e 31ern"5irnL/2e-solidx io ? crn's (H' 'alJi=c conducifY'tys x to Inf:ntty'e-OQ Oee----d -------iO eO ee 8JO W ste :eachate0-1a 1 5 20 25 30SPree sv i! [m /2g-soiid]Fig. 25. Relation between the hl.'draulic conduct vit)' amti the free slvellfor GCLS confined at 29.4 kPsFigure 23 sho¥vs the relation bet¥veen the liquid limitand the free s¥vell. The liquid limit tests were conductedon '_4 types of permeant solutions as sho¥vn in Table 4.These index values ¥vere almost in a linear relation regar'dless of the type and concentration of the permeant solution. Figure 24 sho vs the relation between the hydraulicconductivity of GCL and the electric conductivity of thepermeant solution. The electric conductivity was used asto evaluate practicably the hydr'aulic conductivity ofGC_L, the hydraulic conducti¥'ity should be indirectlyestimated from the relation bet¥veen the free s¥vell and thehydraulic conductivity as sho¥vn in Fig. 25. Even if thetype and concentration of the permeant solution cannotbe specified, the free s¥vell to the solution will derive thehydraulic conductivity. This method to evaluate thehydraulic conductivity of CJCL, permeated ¥vith an inorganic solution is especially available in investigating thebarrier performance of GCL that had been applied at a¥vaste containment facility. The barr'ier performance ofGCL, can be estimated by (1) sampling the r'eal vasteleachate from the waste containment facility, then (2)conducting the free s¥vell test with the waste leachate, andfinally (3) evaluating the hydraulic conductivity from theobtained free s¥vell using the regression curve:lo*' y = exp (a(x - b)) ( i )c¥vhere, x is the free swell of bentonite in GCL, (mL/2g-solid), y is the hydr'aulic conductivity of the GCL (cm/an indicator of the permeant solution because the ionics), a is - 0.31 , b is 8.69 mL,/,- g-solid, and c is 3.09 x 109strength, which is ¥videly used in permeation problems, ofthe ¥vaste leachate could not be calculated correctly. Thecm/s ¥vhich is the hydraulic conductivity at x to infinity. .tendency of the hydraulic conductivity for the chemicalsolution ¥vas similar to that for the waste leachate in therange of the lo¥ ' electric conductivity. Therefore, it ¥vasconcluded that the hydraulic conductivity of GCLS to beused in landfill bottom liners can be estimated by thehydraulic conductivity values obtained from the experiment usln*" chemical solutions having the similar electricc.onductivity values if the chemical solution had theelectric conductivity ¥vithin =25 S/m. In contrast, ¥vhenthe chemical solution or the ¥vaste leachate has the highelectric conducti¥,ity of >25 S/m, the hydraulic conductivity value may be significantly increased and scattered.CONCLUSIONSThis study investigates systematically the effects ofelectrolytic solutions on the bar'rier performance of geosynthetic clay liners (GCL,s), and discusses the adequacyof the hydraulic conductivity test ¥vith the chemical solution as the prediction method of barrier performance that¥vill be exhibited in a real site. The long-term hydraulicconductivity test ¥vas conducted on a nonprehydratedCJCL permeated ¥vith the chemical inorganic solutionsand the ¥vaste leachates, and showed the follo¥vin_"_.results.Figure 25 sho¥vs the relation between the hydraulic(1) The hydraulic conductivity of GCL, significantl .,conductivity and the fr'ee s¥vell. The hydraulic conductivi-correlates to the s¥vellin*" capacity of bentonite containedty tests ¥vere conducted on 40 types of permeant solutionsin GCL, and GCL sho¥vs excellent barrier performance ofas shown in Table 4. The hydraulic conductivity of GCLcould be given as a simple function of the free s¥vellregardless of the type and concentration of the permeantsolution. This relation is very useful in estimating thek< I .O x 10 s cm/sbarrier performance of GCLS or bentonite permeatedvith the inorganic solution, because the barrier perfor'mance can be easily estimated by the free s¥vell, ¥vhich canbe evaluated much more rapidly than the hydraulic conductivity. GCLS have excellent bar'r'ier performance ofk< I .O x 10-8 cm/s ¥vhen the free s¥vell of the bentonite inGCLS is lar*･er than 15 mL/2 g-solid.The type and concentration of the chemical permeantsolution has a significant influence on the barrier perfor'mance of CJCL. However, it is too difficult to predictthe type and concentration of the permeant solutionbefore CJCL is applied to a site, because the solutionpermeated into GCL is unspecified. Therefore, to evalu-vhen the free s¥vell, ¥vhich is an indexof the swellin*' capacity, ¥vas lar'ger than i5 mL,/2 g-solid.('_) The effect of the electrolytic solution on the hydraulicconductivity of GCl, could be explained by the ionicstrength for cation contained in the solution. Ho¥vever,the sensitivity of the ionic strength to the hydraulic conductivity was dependent on the type of cation. Potassiumhad an influence on the increase in the hydraulicconductivity more than sodium, even ¥vhen the valenceand concentration of cation dissolved in each solution'as the same. (3) The hydraulic conductivity for themulti-species solution containing the divalent cation ¥vas10¥ver than that for the single-species or' multi-speclessolution containin*' only the monovalent cation for thesame ionic strength. (4) The long-term change of hydraul-ic conductivity appeared in the cases ¥vhere ¥vasteleachates having the electric conductivity of = 8.58 S/m PHYDRAULIC CONDUCTI¥,ITY OF GCLS¥vere used. The permeant solution having the lo v electricconductivity intercalated a fe¥v exchangable cationsslo vly into the space of crystal interlayers of clay minerals. 'The exchangeable sites in clay minerals ¥vere gradual-ly occupied ¥vith the cations so that the volume of bound¥vater ¥vas decreased ¥vith time. As a result, the permeantsolution having the lo¥v electric conductivity graduallyincreased the hydraulic conducti¥'ity of GCLs. (5) In therange of lo¥v electric conductivity, hydraulic conductivityfor the chemical solution vas almost the same as that forreal ¥vaste leachate having similar electric conductivity.Therefore, the hydraulic conductivity test with chemicalsolution, which ¥vas easily made of inorganic substancessuch as NaCl and CaC*12, had a good possibility to4) Chang, r^, Skipper, N. and Sposilo. G. (1995): C*omputer simufation of interia¥'er molecular siructure in sodium montmorillonitehydrates, Lan*"muir, Il (7), 273427415) Fglofi tein, T. A,, (1995): Properties and tesl methods to assessben onite used in geosyntheric clay liners, Geo yn[hetic Cla_T'Liners. Baikema, Rotterdam, The Netherlands, 51-72.6) Egloffstein, T. A. (2001): Natural bentonites-infiuence of the ionexchange and partial desiccation on permeability and self-heaiincapacity of ben onites used in GCLs. Geotexti!es aird Geomellibranes. Elsevier, 19, 427444.7) Egloff ein, T. A. (2002): Bentonite as sealing materiai in geosynlhetic clay liners - Infiuence of the electrolytic concentration, theion exchange and ion exchange ¥vith ¥vith simultaneous partialdesiccation on permeability. Cla_v Geosynthetic Barriers (eds. byZanzinger. H., Koerner, R. ivl. and Gartung. E.), Slve s &Zei linger= Iisse, The Nelherlands, 141-153,,S) Fernandez, F. and Quigley, R. i¥,1 (1988): Viscosity and dielectricestimate the barrier performance of GCLS that ¥ 'ill beconstant controis on the hydrauHc conductivity of claye_¥' soilspermea ed lvith water-soluble organics. Can,, Geo[ech. J., 25,582-589.applied in an actual site if the chemical solution had theelectric conductivity ¥vithin = 25 S/m.Improvement of the chernical compatibility of ben-959) Gleason, ilvl. H.. Daniel, D. E. and Eykholt, G . R. (1997): Calci lmand sodium bentonite for hydraullc containmeu applicalions, J.Geotech. Geoenviron. E,,gr*"., ASCE, 123 (5), 438445.tonite is one of the important subjects to apply GCLS tobottom liners in ¥vaste containment facilities. ApplicationlO) Griln, R. E. (1968): C!a_v IV;finera!o*"_1'-2nd edition, McGra v-Hill,of multiswellable bentonite or prehydrated bentonite isNe¥v York.ll) Jo, H. Y., Ka sumi, T., Benson, Cconsider'ed an effective method of improving t.he chemicalresistance (Onikata et al., 1996; Shackelford et al., 2000;Vasko et al., 2001; Katsumi et al., 2004; Kolstad et al.,2004b; Katsumi and Fukagawa, 2005; Lee andShackelford, 2005a). In addition, the barrier performance of GCLS that ¥vill be applied in bottom liners isconsidered to be improved by the load of the ¥vastes bu-ried (Petro¥' and Ro¥ve, 1997; Katsumi and Fukaga¥va,2005). The barrier performance of modified bentonitesand the effect of confined pressure acting on bentonitemust be investigated in order to use GCLS Securely as aH and Edll, 'T. B. ('_OO1):Hvdraulic conductivity and s¥velling of non-prehydrated GCLSpermeated ¥vith single species salt solutioris, J. Geotecll. Geoenvi-ron. En*"rg., ASCE, 127 (7), 557567.12) Karabomi, S_ Smit. B.. Heidug, ¥V., Urai, J. and van Oort. E.(1996): The s¥velling of cla.vs: Molecular simulations of thehydralion of montmorilioni e. Science, 271, I i02-1 104.13) Katsumi. T., Oga va. A. and Fukagalva. R. (2004): Efi ct ofchernical solutlons on hydraulic barrier performance of claygeosynthetic barriers. Proc. 3rd Ltlr Conf. Ceosynthetics,70 1 -70614) Ka sumi, T_ and Fukagawa. R. (2005): Fac ors afi cting chemicalcornpatibility and barrier pertormance of C} CLs. Proc. 16thICSllfGE, ivlillpress Science Publishers. Ro terdam, Ne herlands,barrier material in ¥vaste containment facilities.228522S815) Kjellander, R., ivlarcelja, S. and Quirk. J. (1988): Attracrive doublelayer imeractions betlveen caicium clay particles, J. Co!!oid andAC.KNOWLEDGMENTSHelpful comments and discussions were provided byProfessor Craig H. Benson (University of Wisconsin),In!e!face Science, 126 (1), 194-21 1 .16) Kolstad, D. C., Benson, C . H and Edil, 'T. B. (2004a): Hydraulicconductivity and s¥vell of nor)prehydra ed geos_vnthetic clay linerspermeated ¥vith mul ispecies inorganic solutions, J_ Geotech.Geoenviron. Eng/ " , ASCE, 130 (1'_), 1236l249.Professor Masashi Kamon (Kyoto University), Dr.Masanobu Onikata (Hojun Co., Ltd.), and Mr. MitsujiKondo (Hojun Co., Ltd.). The GCLS ¥vere provided byMarubeni Tetsugen Co., Ltd. Thanks are due to Dr.Katsumi Mizuno (Hojun Co., Ltd.) and Dr. KazutoEndo (NIES) for providing the waste leachates for thestudy. Assistance ¥vith the experimental work ¥vas provided by former students of Ritsumeikan University includin_2: Shinya Hasegawa, Shugo Numata, and MasatoYokoi.REFERENCESl) Alther. G_, Evans, J_ C., Fang. H Y. and ¥ritmer, K_ (1985):Influence of inorganic permeants upon the permeabilit,.v ofbentonite, Hydraulic barriers in soil and rock, S'T'P 874 (eds. byJohnson. A . Frobel, R. and Petterson, C.), ASTllvl, ¥¥restConshohocken, Peunsylvania, 64-73.2) Bo 'ders. J J. and Daniel, D. E. (1987): Hydraulic conductivity ofcompacted clay o dilu e organic chemicals, J. Geotecll. E'ngrg,,,113 (12), 1432-1448.3) Bo vders, J. J. (1988): Discussion of terminarion criteria for claypermeability tesring. J. Geotech. Engrg., ASCE, I14 (8), 947-949.17) Kolstad. D. C., Benson, C. H., Edil, T. B. and Jo, HY_ (2004b):Hydraulic conductivi y of' a dense prehydrated G CL permeaiedvith a gressive inorganic solutions, Geos_T, 'nt/tetics Internationa!, 11(3), 233241,18) Lager¥verff. J. V , Nakayama. F S. and Frere, iM. H(1969):Hydraulic conducti¥'ity related to porosity and s velling of soll. Soi!Science Socier_v of Anlerica Proc. , 33, 3-1 1 .19) Lambe, 'T. (1958): 'The structure of compacted clay, J. Soi! J,ifech.Fbulrd. Div., ASCE, 84 (?-), 1-33.20) Lee, J. h,1_ and Shackelfbrd, C. D. (2005a): C*oncemrationdependency of the prehydration efi ct for a geosynthetic clay liner,Soils and Foundation5, 45 (4), ,-741 ,,21) Lee J, i¥,1. and Shackelford, C D. (2005b): Impact of ben onitequality on hydraulic conductivity of geosynthetic clay liners, J.Geotec!1_ Geoenviron. Engrg., ASCE, 131 (1), 64-7722) Lin, L , Katsumi, T.. Kamon, ,1_, Benson. C. H.. Onikata, l¥,L andKondo. N'I. (2000): Evaluation of' chemical-resistant bentonite forlandfiH barrier appiication, Disaster Prevention Research Institt/teAnllua!s. Kyoto University, (43 B-2), 5,_5-533.23) Lolv, P. (1987): S ructurai componem of ihe s¥velling pressure ofclays, Lall*"nu!ir, 3 (1), IS2524) Lutz, J F. and Kemper, ¥V. D. (1958): Intrinsic permeabilhy ofclay as aff cted by clay-1va er imeraction, Soi! Science, 88, 83-90.25)"lesri, G, and Olson, R. E. 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| タイトル | Characteristics of Scanning Curves of Two Soils | ||||
| 著者 | D. Tami・H. Rahardjo・E.-C. Leong | ||||
| 出版 | soils and Foundations | ||||
| ページ | 97〜108 | 発行 | 2007/02/15 | 文書ID | 20983 |
| 内容 | 表示 rSOILS AND FOUNDATIONS¥'ol47, No. 1, 97l08 Feb 'OOlJapanese G eotechnical SocietyCHARACTERISTICS OF SCANNING CURVES OF TWO SOILSDFiNNY TAhi i), HARIA *TO RAHARDioii) and ENG-CHOON LFo*¥,Giii)ABSTRACTScanning curves of two different soils ¥vere obtained from three series of infiltration and drainage experiments ontwo physical models of soil slopes in the laboratory. The first slope model consisted of a fine sand layer overlying agr'avelly sand layer, vhile the second siope model involved a silty sand layer overlying a gravelly sand layer. Each soillayer had a thickness of 200 mm and both slope models had an inclination angle of 30'. The slope models ¥¥'eresubjected to artificial rainfalls of different intensities, followed by draining ¥vhere no rainfallvas applied. Var'iousinstruments ¥vere installed to continuously measur'e the changes in matric suction, volumetric water content and thewater balance of the slope models during the experiment. Scanning curves ¥vere then constructed using the rnatricsuction and water content data measur'ed at the bottom, middle and top parts of the slope models and ¥vere cornpared¥vith the primary drying and primary ¥vetting soil-¥vater char'acter'istic curves that were measured separately. It ¥vasfound that the scannin*' curves follo ved the primary ¥vetting cur¥'e during the adsorption process and then follo ved theprimary drying curve during the desorption process. During the transition period, over ¥vhich the scanning curvemoved from the primary dr'ying curve to the primary ¥vetting curve (or vice versa), the path of the scanning curve had arelati¥'ely flat slope as cornpared to the slope of' the primary curves, and sometimes it ¥vas almost horizontal. Holvever,the slope and the path of the scannin*' curves ¥vere found to be similar for the cases ¥vith similar initial conditions.Key ,vords: hysteresis, scanning cur¥'es, soil-¥vater characteristic curve, unsaturated soils (IGC: D4/E6/E7)due to its non-uniforrn pore size distribution. There areIN1'RODUCTIONthree specific mechanisms causing hysteresis (I¥vata et al. ,Hysteresis in the relationship between negative pore¥vater pressure or matric suction and water' content is1995): (i) dift rent por'e sizes of the soil in difi rentmoisture states, (ii) adsorbed lvater on clay surfaces andcommonly obser¥'ed for many unsaturated soils in the(iii) differ'ent contact angles bet¥veen the air-¥vater inter-laboratory. The path of the matric suction ¥'ersus waterface and the soil solid surface.content plot for the desorption pr'ocess (i.e., decrease inThe plot of water content or degree of saturation¥vater content) and the path for the adsorption processversus matric suction of soils is kno¥vn as the soil- ¥'ater(i.e., increase in water content) are different, as a result ofcharacteristic curve or SWCC. The ¥vater content of' thehysteresis. This phenomenon can be described usin*' thesoil decreases as its matric suction increases follo ving a'ink bot.tle effect' . When an empty capillary tube is placedin a water bath, the ¥vater table lvithin the tube ¥vill rise updrying (desorption) path and the reverse cycle ¥villincrease the ¥vater content along a ¥vetting (adsorption)path. The soil-¥vater characteristic curve is hysteretic;until ¥vater reaches an equilibrium state. In this case, thewetting cycle occurs. On the other hand, when the tube isfilled up ¥vith ¥vater, water ¥vill be drained out until itreaches an equilibrium state. The case refers to the dryingcycle. The equilibrium state achieved thr'ough a wettingcycle and through a drying cycle is the sarne lvhen thetube is straight. However, ¥vhen the tube has an expandedthat is, f'or a specific matric suction, the water' content ona vetting curve is always lo¥ver than that found on adrying curve. The drying curve that starts from saturation is comrnonly called the primary drying curve (Fig. l).Similarly, the vetting curve that starts from a dry (orrelati¥'ely low ¥vater' content) condition is commonlycalled the pr'imary wetting curve. The region enclosedwithin the primary drying and primary ¥vetting curves iscalled the hysteresis region. Besides the primary cur¥'es(or bounding curves), the "scanning" cur¥'es are series ofspace in the middle, the equilibrium state may bedifferent. The expanded portion of the tube is empty inthe wetting cycle, while it is filled with water in the dryin*'cycle. As a result, the water contents obtained from thewettin*' and dr'yin*' cycles are not the same. The abovesoil-water characteristic curves that start from a particu-lar condition that is neither saturated nor dry. Thesecapillary tube analogy applies to soil conditions in natureFormerly Research Scholar, School of Civil and Environmental Engineering, Nanyang Technological Universiiy, Singapore.*'* Professor and vice Dean, ditto (chrahardjoC"n u,edu,sg).Associaie Professor and Head of' Geotechnical and Transportation Engineering Division, ditto.The manuscript for this paper ¥vas received ft)r revielv on November 17, 2005; approved cul July 26, 2006¥Vri ten discussions on this paper should be submitted before September i, 2007 to the Japanese Geolechnical Society, 4-38-2, Sengoku,Bunkyo-ku, Tok.vo 1 12-001 l, Japan. Upon request the closing date may be extended one momh.j)=ii*C).l 98TA ,11ET AL.The focus of this paper is to compare and analyse60scannin*･ curves that vere obtained from a series ofinfiltration and draina*･e tests on a physical model of soil=0slopes in the laboratory. Both ¥vetting and drying40scanning curves of two different soils (i.e., fine sand andoa,silty sand) are presented Scanning curves measured atthe bottom, middle and top parts of each slope model¥vere constructed and compared ¥vith the primary dr'yingand primary ¥vettin_g: curves that ¥vere measured inde-o:IS 20E:,>opendently, to sho¥v the processes (i.e., drying or ¥vetting)oi lOo 101 0203Matric suction, (ua u ) (kPa)Frg 1. Primar¥_' soil-1vater clraracteristic curve and scanning curvesscanning curves are different depending on the state of thereversal point in the process of successive ¥vetting anddrying (see Fig. l).Researchers In the soil physics field have tried tomeasure and construct the primary and scanning curvesof a porous specimen in the labor'atory for a long time(e.g., Topp and Miller, 1966). Topp and lvliller (1966)measured the scanning curves for a poorly graded glassbead sample. Many other researchers have measured therelationships bet¥veen ¥vater content and pore-¥vatersuction for different soils (e._g:., Talsma, 1970; Watson etal., 1975; Topp, 1971; Poulovassilis, 1970; Poulovassilisand Childs, 1971; Vachaud and Thony, 1971; Nimmoand lvliller, 1986; Hogarth et al., i988, Feng and Fredlund, 1999; Pham et al., '_003). Ho¥vever, their main concern ¥vas the primary or bounding curves, rather than thescanning curves, in studying the hysteresis phenomena inunsaturated soils.A number of simple analytical solutions have also beendeveloped to provide forms for the primary curves thatexhibit hysteresis. In the early stage, the independentdomain theory. Ivas used to model the hysteresis of ¥vaterin soil. The soil pores are vie¥ved as independent domainthat have only t¥vo states, either full or empty, and eachdomain has t¥vo corresponding matric suctions for eachin an unsaturated slope under different flux conditions.The differences obser'ved in the scanning curve of thesetwo soils as well as the characteristic of the scanningcurve are analysed and discussed.MATERIALS AND METHODSDescription and Parail7eters of Soi!sT¥vo-layer soil slope models ¥vere constructed in thelaboratory to elucidate the mechanism of water flo¥v inunsaturated slopes. The soil slope consisted of relativelyfine soil over relatively coarse soil layers. Sllty sand andfine sand ¥vere used as relatively fine materials, ¥vhilegravelly sand ¥vas selected as a relatively coarse material.The silty sand is a local residual soil from the BukitTimah formation (Public Works Department, 1976).Bukit Timah Granitic residual soils vary from silty orclayey sands to silty or sandy clays, depending on thedegree of ¥veathering, but ar'e commonly sandy clayeysilts (Rahardjo, '-OOO). The fine sand ¥vas a sand used inthe Changi reclamation projects. The light grey to lvhitegravelly sand ¥vas crushed from fresh granite. These threesoils ¥vere selected to provide t¥vo-layer soil slope models¥vith contrasting hy. draulic parameters.The silty sand was ¥vell-graded ¥vith a coefficient ofuniformity, U* of I 120 and a coefficient of curvature, C*of 1.58, and was cate*"orized as an SM soil according tothe Unified Soil Classification System (USCS). The finesand ¥vas poorly-graded (U* of 2.1 and C* of 0.89). Thegravelly sand was a poorly-graded, uniform soil ha¥'ing50.10/0 of grains passing the No. 4 ASTN/1 (4.75 mm).state. Poulovassilis (1970) reported a theory that is applicable to glass beads and sands. Ho¥vever, other' re-Both the fine sand and _ :ra¥'elly sand ¥vere categorized assearches observed considerable discrepancies bet¥veensaturated coefficients of per'meability, k*, for the siltysand (at a dry density of I .47 Mg/m3), the fine sand (at apredicted and observed scanning curves (TOpp andpoorly-graded sand (SP according to the USCS). TheMiller, 1966; Topp, 1971; Talsma, 1970; Vachaud andThony, 1 97 1 ) . Muaiem ( 1 974) then pro posed aconceptual model of hysteresis that simplifies thecomputational procedures but _g:ives better agreementdry density of 1.56 Mg/m3), and the gravelly sand (at adry density of 1.62 lvlg/m3) were 2.2x 10-6, 2.7x 104with observations. Subsequently, Parlange (1976)proposed a model that corresponds to a special case ofto the dry densities used in the slope models. The basicparameters of the soils used in this study are sho¥vn inMualem's hypothesis, ¥vhich requires a knowledge ofTable I .only one primary cur¥'e. Hogarth et al. (1988), Viaeneand 7.6 x 10-2 m/s, respectivel}.,. The dry densities of thesoils in the permeability tests ¥vere controlled to be similarThe primary dryin_curves of the soil-¥vater character-(1995), Si and Kachanoski (,_OOO)istic curves of the soils ¥vere measured using a Tempeand Braddock et al. (2001) applied the classical Brooksand Corey (1964) and ¥'an Genuchten (1980) soil-1vater'characteristlc curve models to the Parlange hysteresismodel and reported that the predicted curves agree ¥viththe laboratory observation.pressure cell (Model 1405 BOIM3-3, Soilmoistureet al. (1994), L,iu et alEquipment Co., USA), ¥vhile the primary ¥vetting curves¥vere measured using capillary rise tubes. The Tempepressure cell operates on the same principle as the pres-sure plate apparatus as described in ASTM D 2325-68 r99SCANNING CUR¥'ES OF T¥¥*O SOILSTable l. Index and !1)draul c parameters of the soilslOO, l='ff'¥'==SoilsPropertiesll 1Fine SiltyUnlt Gra¥'ellysand sandsandUnified Soil ClassificationSpecific gravit}'SPsPSlvl2 622 652.595O.35O.230.17O.56O.O00521l 120Crain-size analysis resultsD6{)Inm 5 -D<0D orllm 3.6Smnl 2.7319Coef cient of uniformity, C*,Coef cient of cur¥'ature, C*Gravel contenl (>4.75 mm)Fines content (<0.075 mm)0.96o*/a 49.9OOI*lj ifi i_'I II]iil' iI' i: 50 11""""""""""_"'_'_'_ijt:i,i= * 'l=I =i *i i [,: [ rr'i'irT1 . I =';' j ' ILill ; i*===*i"4e20to*l{l¥ ,1= =:ilty=*d' l = :i iiir"^ -> 'IfiLiljfjl..-- 'I Ij!i '=i-= - 1f!II't llI02 10.89Ol.580.838 9l!!1 i" "Il__ =='' =L_;:i jU{ Illltol e*.:lly'' j_'* d spFi * =*nd sp-lllil1002o 1 o'ol o'ooiGr in size (mm)Atterber_ * IimitsLiquid limitOj'OPlastic limitO!!OPlastici y index, PIO/ IO4827Fig. 2. Particle size distribution curves of soils used in the stud,21Relative density test results'I".._ /ms I .42*,,Iaximum dry density, Jzd**.* N,Ig /m; I 7 1,Iinimum dry densitv, 7zdO.845O 532,iax'imum void ralio, e ,<>l¥,Iinimum ¥'oid ratio, e**xi**Compactionest results,Iaximum dry densi y, izd*****Optimum water conlent, T,'*, *Saturated permeabiliiy, k,,at dry densitv, Jzcii .341.21l 61l 56O.978O_646l 1400.660e_03N'Ig /m' - I _S502lom/s 7 6xlO 2 2,7xlO -' 2.2x lO6N'Ig/m; I .62 1 .47l .56(1994) and the method using capillary rise tubes can befound in Lambe (1951) and Fredlund and RahardjoeJa.1OOa.ol aI ooo I oooMat c suctian, (u_-u*,,j (kPaj(1993). The measured volumetric water content and thecorresponding matric suction for both the primary dryin_O._and pr'imary ¥¥'etting soil-water characteristic curves ¥vereFig. 3. Primar) soil-water characteristic curves of soils used in thestud) (W antl D indicate wetting and drying data, espectively)fitted using the Fredlund and Xing (1994) equation. Thecor'rection factor for the fitting equation, C(V/), was setto I as recommended by Leong and Rahardjo (1997). Thevolumetric water content data, the scanning curvesmain purpose of the curve fittinga ¥vas to obtain smoothand full-range primary drying and lvetting soil-wat.erdeveloped during the exper'iments ¥vere constructed.characteristic curves. The dry densities of the soils used inPhysical Model of' Soil Slopethe tests f'or the determination of the primary soil-1vatercharacteristic curves were controlled to be similar to thech'y densities used in the slope models.The grain size distribution curves of the soil samplesThe general arrangement of' the physical model isshown in Fig. 4. The rnain components of the physicalare sho¥vn in Fig. 2, vhile the primary drying and theprimary vetting soil-water characteristic curves areinfiltration box was 2.45 m in length, 2 m in height andpresented in Fig. 3.table, Ivhich also functions as an enclosure for a ¥vatersurnp tank ( vhich provides the rainfall and recycles itusing the ¥vater' circulation system) and a ¥vater' pump.The rainfalls vere applied through a rainfall simulatorlocated on top of the infiltration box. The intensities anddurations of the simulated rainfalls ¥vere controlled usinga magnetic flo¥vmeter, ¥vhile the amount of ¥vater flowsLabol'atory ExperimentsSoil slope models were designed and constructed in thelaboratory to study the mechanism of ¥vater flo¥v inunsaturated soil slopes. The two-layer soil slope modelsconsisted of a 20-cm thick layer of relatively fine soil(i.e., fine sand or silty sand) over a 20-cm thick relativelyicoarse soil layer (i.e., gravelly sand), and were con{structed inside an infiltration box and subjected to simulated rainfalls ¥vith varying intensities and durations.The changes in matric suction and ¥'olumetric ¥vater content at various locations along the slope model, as ¥vell as{ii{;ichanges in vater balance, ¥vere monitored continuouslyduring the experiments. From the matric suction and themodel are: an infiltr'ation box, a rainfall simulator, a¥vater circulation system and rneasuring devices. The0.4 m in ¥vidth. The infiltration box is supported by a steelfrom the model ¥vas measured using electronic weighingbalances. A detailed explanation of the apparatus andtest procedures adopted are given in Tami et al. (2004).Measuring DevicesA tensiometer-pressure transducer system and timedomain reflectometr'y (TDR) ¥vere employed to continu-ously measure the changes in matric suction and ?:TAhJI ET ALlOO2c022sc c-25 ce' 02"f.,+ee e2 ･7ce c )_ 28c :'02j:/r;i:{( j;/':,::'.iJ*l iSlity sani '_=2i!i1Tr *,2Jui 02 21 J ; 02 2S22 J022J02! a * 2S i ! 02111T 1eFrg 5. Daih., fiuctuation of tensiometer readings in sihy sand and finesand after the correction madeFig. 4. A vielv of laborator)' sct-up for the experiment (RS: rainfalsimulator, IB: infiltration box, DAS: data acqilisition s.vstem, ¥VB:colleetion tanl{ above electronic lveight balance, TDR: Irasesl.'stem and accessories, T: tensiometer body tube and pressnretransducer attac!led, FS: fine sand la .'er, GS: gravelly sand layer(magnetic fiolv meter not sho vn in photograph)volumetric ¥vater content alon*' the slope model duringthe experiments. The experimental data vere stored in aand as a result, the accuracy of the tensiometer'-transducer system used could reach 0.1 kPa.This correction was especially effective and useful in along-term experiment or in a steady-state experiment,¥vhen the change in the matric suction of the slope model¥vas not large. Without the correction, it ¥vould bedif cult to analyze the experimental data since thechanges in matric suction observed could be at similarorder to the fluctuations. Figure 5 presents a relativelypersonal computer via a data acquisition system, forsmall daily fluctuations of matric suctions from thesubsequent analyses.tensiometer-pressure transducer readings in the fine sandand the silty sand after applyin*" the correction.Tensiometer-Pressure TransducerSmall-tip tensiometers, with flexible coaxial tubing,from the Soilmoisture Equipment Corp. were used in thisstudy. The pressure transducer can measure negativeTime Domain Refiectometry (TDR)The TDR system used in this study was manufacturedby Soilmoisture Equipment Corp. The system consists ofand positive pressures (i.e., - 100 to 75 kPa) and ¥vasa step-pulse generator (i.e., namely Trase BE) that comesattached to each of the tensiometers for automaticwith a 4-megabyte memory card for data storage pur-data recording. The pressure tr'ansducers ¥vere calibratedagamst water pressure and each pressure transducerposes, a coaxial cable and three-rod standard buriable¥vave-guides ¥vith r'od dimensions of 3 mm in diameterreadin*' ¥vas rechecked or verified again prior to theand 200 mm in length. A 76-channel multiplexer en-ex periments .closure and two 16-channel TDR switchin9: boards ¥verealso used to allo¥v simultaneous measurements of volu-During a trial run prior to the experiments, it ¥vasobserved that the tensiometer-pressure transducer systemused could give almost an instantaneous response (i.e.,within one minute) to the changes in matric suction in thesandy soils and needed a maximum five minutes tomeasure matric suction in the silty sand soils. The differ-ence in response time of tensiometer-pressure transducersystem ¥¥'as due to the difference in ¥ 'ater content of thefine sand and silty sand used in the slope model at thetime of the trial run. The response time of the tensiometer-pressure transducer' system decreased as themetric ¥vater content for up to 31 ¥vave-guides.The relationship bet¥veen the dielectric constant (K*)and the volumetric water content (e,,,) of soil for thestandard buriable ¥vave-guide used was provided by theTDR's manufacturer and it ¥vas already integrated in theTrase BE. The maximum deviation of the measurement is20/0 of the volumetric water contents (Soilmoisture,1996). In this study, the accuracy of the TDR used in themeasurements was verified prior to the experiments. Thevolumetric water contents of soils measured by the TDRde*'ree of saturation of the soils increased.It ¥vas observed that the tensiometer-transducer system¥vere compared ¥vith the volumetric ¥vater contentsused exhibited daily fluctuations of up to I kPa. Themagnitude and pattern of the daily fluctuations of thetest ¥vas conducted on ail soiis used in the study over thepressure tr'ansducers' readings ¥vere similar for each datalogger. Therefore, these fluctuations could be eliminatedby using a reference transducer in each data log_ er. Thereadings of the other pressure transducers ¥¥*ere correctedbased on the readings of the reference pressure transducermeasured by. the oven-drying method. This verificationran*･e of ¥vater contents. Figure 6 presents the verificationcurve of the TDR measurement. Unlike the tensiometertransducer readin_ , the TDR reading did not exhibit dailyfluctuations.A total of 18 tensiometers ¥vas installed along 6 crosssections ¥vith 3 tensiometers located in each ro¥v. Similar-: SCANNING CURVES OF T¥¥,O SOILS101It ¥vas suspected that the lvater phase in the gr'avelly sand: K.'- iOOc')¥vas likely discontinuous due to the lo¥v ¥vater content ofQ)the gravelly sand layer (i.e., 3 to 40/0 at the initial stage of?;) 80,::experiment). Once the tensiometer lost contact with the¥vater phase in the soil, the tensiometer reading ¥vould1:'e:e)>o 60o= 40become unreliable. The relatively large size of the gravellye)sand grains and the tensiometer tip ¥vould not besand grains also contr'ibuted to the poor performance ofthe tensiometers since good contact between the *･ravelly:oo{S 20achieved. As a result, only the scannin*･ curves frorn the;relatively fine soil layer (i.e., fine sand or silty sand) ¥vereI 5>o 20 40 1 oo60Vol water content from TDR80Ieasurements (o/o)Verification of TDR measurement against oven-drying methodFig. 6.T* 4*L53il5Locahon ot scan ing curvesB (T-24: TDR-32)T44T43T4M CT-34; TDR-52)T-44:DR-72)T*34T･3BT-3eM ,T-24T-23c)T*･BT*i 4T-} 3:coOR*1 2D - 1eflne soil :ayerOR*32TQ *31:ns vmenta'Jon iD:along ro¥¥"-3 (i.e., T-,_3, T-33 and T-43), because theirlocations ¥ver'e closer to the locations of the corre:bottom, middle and top part locations of the model,respectively. The tensiometers and the TDRS used ¥verealso highlighted in bold type.# TDR , ve-guideo ensiome 8rtipAs can be seen fr'om Fig. 7, the locations of the2002 OO mmSOsponding TDRS (i.e., TDR-32, TDR-52 and TDR-72).The locations vhere the scanning cur¥'es measured arepresented in Fig. 7 as indicated by B, M and T for theTOR*S1TOR42TOR4T-14'-4 (i.e., T-24,T-34 and T44) ¥vere selected, instead of those locatedeTDR-T1c DR･72R.22roR*2Ve ic l di +t nee [o su ce (mn ):T-34 and T-44 and the volumetric water content datameasured by TDR-52 and TDR-7,_ ¥vere used, r'espectively. The tensiometers located along roRelativelycoarse soilayerTDR-Se1 50Fig.T?OeTDR･S2OR-52o*#o*#eeRelative:yavailable from the experiments.For the scanning curves located at the bottom part ofthe model, the matric suction data measured by tensiometer T-24 and the volumetric ¥vater content data measuredby TDR-32 vere used. Similarly, to construct the scanning curves located at the middle and top parts of themodel, the matric suction data measured by tensiometersDR* '2-24 TD -321 OO50 100T-34 TDR-S2 T44 TDR-7235 1 OOSO i OO7. Location of measuring devices and the points where thescanning curves lvere measured (B,middle and top parts of the model)M and Tindicate bottom,ly, a total of 14 TDR ¥vave-guides ¥vas installed along 7cross-sections vith 3 TDR ¥vave-guides located in eachtensiometers used to construct the scanning: curves arelo 'er than the locations of the corresponding TDRs.Ho vever, in terms of vertical distance to the surface ofthe slope model, the tensiometer locations are nearer tothe surface of the model compared to the cor'respondin*"TDRS Iocations. These arrangements of the locations ofthe tensiometers and the TDRS Ivere consistent for thethree sets of scanning curves analysed in this paper. Theerror that could be involved in the construction of thescanning curves due to the different locatrons of thetensiorneters and the TDRS are discussed in Erl'or illcross-section. The arrangement of the tensiometer tipsand the TDR ¥vave-guides along the slope model is sho¥vnEstilnation of Scanni/7g Curves due to the Dlfferent Loca-in Fig. 7.tions oj' Tensiometer Tips and T'DR Wave-Guides of thispaper.Constructioll of the Scanning CurvesThe matric suction and volurnetric lvater content datarecorded by the tensiometers and TDRs, r'espectively,from locations at close proximity are plotted together onthe same graph. This plot can be used to investigate thepath along the soil-¥vater characteristic curve that ¥ 'asRESULTS AND DISCUSSIONThe experimental data frorn the t¥vo infiltration testsare presented and analyzed in this paper in order to studythe characteristics of' the scanning curves for fine sandfollowed during the experiment. These paths define t.heand silty sand. The infiltration tests involved bothscanning curves for the soil-¥vater characteristic curve.adsorption (i.e., application of simulated rainfall for a**iven intensity and duration) and desorption (i.e., noapplication of simulated rainfall ¥vhile infiltrating lvater¥vas allowed to drain out from the slope model). Hence,Three sets of scanning curves frorn the experimentaldata from the bottom, middle and top parts of the slopemodel were constructed for each series of experiments.suction in the relatively coarse soil layer (i.e., gravellythe volumetric vater contents of the soils increasedduring the adsorption process and decreased during thesand) and the tensiometers gave erroneous readings.desorption process.Difficulty was encountered in measuring the matric l02ETTA *11AL .Prior to the experiment, t,he slope model ¥vas leftexposed to ambient conditions for about one ¥veek afterinfiltration test, where A and D indicate adsorption anddesorption processes, respectively. The draining processthe previous infiltration tests had ended. This ¥vas done tominimize the effect of the previous test on the current testas well as to obtain a relatively dry initial condition forthe model. Each infiltration test compr'ised of three sta*"esof Stage 111 (i.e., Stages 111-D) for the experiment on theslope model consisting of fine sand over *'ravelly. sand(i.e., the first infiltration test) ¥vas carried out for about60 hours. Ho¥vever, due to the difficulty of draining thesilty sand (i.e., the silty sand has a significantly lo¥vercoefficient permeabilit}., compared ¥vith the fine sand),Stage 111-D consisting of silty sand o¥'er gravelly sand'ith different rainfall loading being applied. In eachstage, a t¥venty-four hour simulation ¥vas conducted,starting ¥vith 5 hours of adsorption (i.e., application ofrainfall or ¥vetting process) and subsequently followed by(i.e., the second infiltration test) ¥vas continued up to 12days.i9 hours of desorption (i.e. , no rainfall applied and ¥vatervas allo¥ved to drain from the model or drainageThe underlain *'ravelly sand layer used in the slopeprocess). The average intensities of the simulated rain-model, apparently acts as a capillary break similar to thatin a capillary barr'ier system (i.e., relatively fine-grainedlayer over relatively coarse-grained layer). Under certainfalls applied during Stages I. 11 and 111 of the first infiltra-tion test ¥vere 8.1, 19.2 and 8.0mm/h, respectively.Similarly, in the second infiltration test the averagecircumstances, the relatively coarse-grained layer pre-intensities of the simulated rainfall applied were 7.8, 15.8vents do vn¥vard ¥vater movement. In the infiltration testsand 7.5 mm/h during Stages I, 11 and 111, respectively.The duration of the application of the simulated rainfallspresented in this paper, no breakthrough (i.e., penetration of vater to the relatively coarse-grained layer) vasobserved as the matric suctions and ¥vater contents of thein the second infiltration test was the same as in the fir'stgravelly sand layer remained unchan*"ed throughout theinfiltration test. Fi**ure 8 sho¥vs the intensities anddurations of the simulated rainfalls applied in the firstStage I Stsge IIS = =E: 2 +itests.Genera! Shapes of the Scanning CurvesScanning Curves of Fine SandStage illFigure 9 sho¥vs three sets of scanning curves measuredin the fine sand at locations B, M and T (see Fig. 7).The solid symbols (i.e., diamonds, circles or squares)D'l.s'S i_ 'represent the experimental data from the adsorptionprocess, ¥'hile the open symbols represent the experimen-tal data from the desorption process. The time intervallapsed tme (h)bet¥veen measurements lvas 5 minutes. The primaryFig. 8. Intensiries and dursrtioms of simulated rainfali applied in thedrying and the primary wetting soil-water characteristiccurves as obtained from independent measurements (i.e. ,first and second infiltration test seriesI40!¥ {i¥ i l-+' "' l-A I-D- er li-A Il-D;il1f;X iiI :1i ; Primacurves:> o(cr30i;iii'Ji;j :;';i; ('fiiY'1r'i I-oF(Di!i!felJ[[-A I -D¥Primary Curves:Drying}r*X ,T= ,We=t n=¥ il' PrimaryCurves} = _E5;Il1 Irioj '...¥! = ¥= X)0=/ " 'r" " ri*FItj;:_'=:p':i ･,..**+*+**''; ';;;;"* *!* 'i : ": ' ii;ii. ; ii I '- _ "i '*....l ]1l ;I ¥i i :T W, ett ingl" , l,¥i oo;= '.' .**i*=*+ ** * *(1)Drying,1 i ; ,*"- :o-+<>- l-A -Di--l-A l-D¥i ¥ i _ jll-A l[1-D, ,, vK)20>I-A -D¥"ii-A i-DC>*-¥=[Yc L!'Hi}; r'i't'lco{: - i!1-A i!1'rD--+ -¥Y' {' { YPf='-/1::# i' ;" fr_ 't # ; " ' i¥Y¥; ! =i=" s YO i 2 3 4 5 60 1 2 3 4 5 60 1 2 3 4 5 6Matric suction, (ua uw) (kPa)Matric suction, (ua uw) (kPa)Matric suction, (Ua uw) (kPaj(a) at bottom part of the model(b) at midd]e part of the model(c) at top parts of the model(location B)(location M)(location T)Fia. 9. Primar¥.' soil-water characteristic and sca:nning curves measured in the fine sand dtlring the first infiltration test series (1. II, IH indicate thestages, 11'h le A and D indicate adsorption and desorption, respectivei)) rSCAN. NINGCURVESTempe pressure cell test or capillary rise test) are alsochanges in the second stagepresented in Fi_･... 9.those in the other stages (see Fig. 9).The scanning curves follo¥ved the primary wetting soilwater characteristic curve during the adsorption processand follo¥ved the primary drying soil-¥ 'ater characteristiccurve during the desorption process (see Fig. 9). Sincethe adsorption exper'iments vere started frorn a drycondition, the scanning curve lvas initiated from theprimary drying curve. At the initial state of the experiments, the scanning curves fir'st moved from the primarydrylng cur¥'e to the primary ¥vetting curve, ho¥vever thepath did not move horizontally since both matric suctionsand volumetric ¥¥'ater contents changed. The scanningcurves then follo ved the path of the primary ¥vettingcur¥'e to some extent, depending on the intensities of thesimulated rainfall applied. It ¥vas also observed that therates of matric suction and volumetric vater contentchange decreased as the scanning cur¥'e data pointsbecarne closer to each other since the acquisition timebet¥veen two data points vas the sarne.Once the simulated rainfall ended, the scanning cur¥'esmoved back to the primary drying curve. However, thedevelopment of these drying scanning curves ¥vas slowercompared ¥vith the development of the ¥vetting scanningvere notlceably higher thanIf the scanning cur¥'es from different locations arecompared, it can be seen that those measured at locationB ha¥'e the largest matric suction and volumetric ¥¥*atercontent variations, ¥vhile those measur'ed at location Thave the smallest matric suction and volumetr'ic ¥vatercontent variations. Even though the simulated rainfall¥vas distributed uniformly over the surf'ace of the model,the difference in terms of the size of scanning curves stilloccurred since the infiltrated ¥vater flo¥ved along the finesand and accumulated at the lower part of the slopemodel, resulting in the larger changes in matric suctionsand ¥'olumetric vater content in the lower part of theslope model.Scanning Curves of Silty SandAnother thr'ee sets of scanning curves measured on thesilty sand ar'e presented in Fig. 10. The intensities anddurations of the simulated rainfall applied in theexperiments lvere similar to those applied in the experiments on the fine sand (Fig. 8). Ho vever, the data plottedin Fig. 10 ¥vere taken from measurements with a timethe drying curves. This observation indicated that theinterval of 10 minutes.Unlike the scanning curves measured for the fine sand,the scanning curves measured for the silty sand vere onlydecrease in matric suction and the increase in volurnetricin a form of horizontal paths bet¥veen the primary¥vater content occurred rapidly during the adsorption¥vetting and the primary drying soil-¥vater characteristicprocess. In contrast to the r'apid changes in matrlc suctioncurves. This happened since the volumetric ¥vater con-and volumetr'ic ¥vater content observed in the adsorptionprocess, the increase in matric suction and the decreasevolumetr'ic vater content observed during the desorptionprocess occurred gradually.The difference in the rate of development of the scan-tents of the silty sand did not chan_._"e during the t venty-cur¥'es, as the plotted data ¥vere set in a closer distance inning curves between those observed on adsorption andthose observed on desorption was related to the changesin the coefncient of perrneability of the soils. In theadsorption process, the permeability increased during thetest since the matric suction decreased and this caused arapid increase in the ¥'elocity of water flo¥v in the soil. Onthe other hand, the permeability decreased during thedesorption process since the matric suction increased andthis caused a slo¥ving down of ¥vater movement along theslope model. As a result, the changes in matric suctionoccurred gradually in the desorption process.It lvas also observed that the matric suctions and volumetric ¥vater contents in the fine sand returned to theirinitial values (i.e., prior to the application of the simulated rainfall) after 19 hours of drainage. As a result,f'our hour simulation. The scanning: curves moved f'romthe primary drying cur¥'e to the primary ¥vetting curvedurlng the application of' rainfall (i.e., adsorption process) and returned to the primary drying curve again after19 hours of drainage (s'ee Fig. 10).In order to obtain a full-100p scanning curve forthe silty sand, one additional series of unsteady-stateinfiltration tests ¥vas conducted. Prior to this additionaltest, the slope model ¥vas left under ambient condition forabout 50 days to achieve a relatively dry condltion in thesilty sand. The rainfall loadings in this test ¥vere alsoreduced (i.e., by reducing the duration of the sirnulatedrainf'all to I hour) to rnaintain a lo¥v degree of saturationof the silty sand. There were four infiltration stagesinvolved in the additional test. In the first stage, theintensity of the rainfall applied was 9.9 mm/h and followed by a 3 days draining pr'ocess. In the second, thirdand fourth stages, the intensities of the applied rainfallswere I 1.1, 10.3 and 69.0 mm/h, respectively, follo ved bydulmg the t¥venty-four hour simuiation, complete7 days of' drainage. Fi*aure 11 illustrates the prog)ram¥vetting and drying scanning curves could be obtained.The scanning curves from the first and the third stages(see Fig. 8) were alrnost the same for both adsorption andadopted in the additional series of infiltration tests.desorption, while those f'rom the second sta*･e variedFig. 12. The time interval used ¥vas 10minutes. Themore ¥videly but still exhibited the same trend. Thematric suction and volumetric ¥vat.er content data wereintensity of the simulated rainfall ¥vas higher during thesecond stage than those applied in the other t¥vo stages,taken from the readings of tensiometer T-14 andthereby producin*･ a longer path for the scannin*･ curves.The matric suction and the volumetric_103OF 'T¥¥*O SOILSvater contentThe scanning curves obtained frorn the additionalseries of unsteady-state infiltration tests are presented inTDR-12, respectively. The scanning curves at iocation T(see Fig. 7) ¥vas not available since the matric suctionsobserved in this part of the model vere beyond the range ヱ04τAM茎ET AL．一・卜A l−D一一 秘〈〉 1トA lレD 鰯く）一 鷺一｛｝ ［ll−A 擁i−D己♂40芒￡1−A l−D口1 1「一一㈱＿1、All−A ll−D lll−A l目騨D i i1−D 翻〉 ll−A・i 鰍｛｝ 目1−A聾一D【ll−D 巽i PrimaryCurves．ll −r纏馬、 lii燕iili皿oQ i PrrmaツCurves． i l 田 i I 1i i ［）rylng㊥綿ti I l l i 劇…1唱li P ξ脳輪奪li…・￡O」35ヨ＼Φ…≡…田田用N、9… ＼凝o＞＼額 30PrimaツCu四es寧騨iπ源 Dryingl l網一一We賞ini目…0 4 8 12 16 20 24 0 4 8 12 ↑6 20 24 Matricsuction，（αθ一Uw）（kPa）Ma重ricsuction，（σ∂一Uw）（kPa）（a〉at bottom partofthe modeI （bcationB〉04812162024Matricsuction，（αθ一1／w）（kPa）（b）at middle partofセhe model（c）attop Par重s ofthe modeI （locationY） （iocationM）Fig。10． Primary solレwa重er ch賢rac1eris重lc and scanning curves measured i癩the siky sand dur董ng Ihe second in行ltratio訊est series（1，II，III i鶏dic飢e Ihest段ges，whileA段ndDi鳳dica重eadsorption段nddesorption，respeαive】y）T44vsτDR42（ex甘emele負Grosssec廿on）5g o．L蔓38εε… AI103昌匙O窩 O多ε暴C琵S職］1ε1εd隊l 5c5馨卜oじr08Feb2003，09100： ←く一調トA同レD 8目d ofmeasurement24Jaa363108ぷ泊nFebざli 僧醐 一 l alc㎝d、l…農c34虫弦〔103隈繭lorIhour｝ 澱読 1アJan2003，雀6：GO：applica冒onoぎr謝ヨ！1悪…爆I驚E（掘mm加めr籍our｝マ1麗讐轡 タ戸／ ξ 、30 were not complete，since the suctlons in the middle and14Jan2003，1410αappricatめnofrainr副E（99m輪forlhour｝ 驚。哩 toP Parts ofthe slope mo（iel were also relatively hig勤after（cavitations in the tensiometer）in most of the experi−appllca勧ofra輪匪観i盤32a long Period Qf drainεしge an（i cou1（i not be measu影ed2尋Jan2003，16：30：セ S畷e董nmIr段｛io磁IestserieskPa）．Similarly，thescanuingcurvesatlocationsMandB（690mn》hfodhDロr） 1FigほL ExperlmenI段l program adoPIed in the謎ddition騒hmsteady−of measurement of the tensiometer（i．e．，greater than玉OO3iJan2QO3，萱6，Q厭言ppl…calbnDfrainlallt−配 14 17 Jan Jan 梱ン il−A li甲D P》琶 9、9 額1l i i l銅．D28 Dゆg SWCC一一We穎ng SWCCo爆Inl恒ヨl condi匠on（aRer50・d§ydrainrng） ¶0 20 30Ma願csuction，（uθガ謄）（kPa）ments． As can be seen in Fig．12，the scannlng curve startedfrom the dry重ng Primary curve slnce the model ex−perienced（1τying prior to the experiments．During theapplicatlon of tbe simロlated rainfall ln the nrst stageFig、12、Scanningcurvesfromtheresul重sofIlle段dd韮重ionaluns霊e段dy− s畷ei洲症ratloηIheseriesmeasured茎n纏1esiltysand（IJI，夏夏IJV lnd釜cateIhestages，、、・hileA鮒dDindicateadsorp芝lonand desorp重員on，resPec重iveコy）（dated14Jan），there was no s圭gnincant cむanges in bothmatric suction and volumetric wαter content．However，additionεし1series of tests （Fig． 12） were found to haveafter the simulate（i rainfal至ended，it was observed thatdi価erent shapes compare（i with the scannlng curve fromthe matric suction started to（iecrease and the volumetricthe typical innltrat呈on test．Unhke the scanning curveswater content to increase，resalting in the scann量ng curvepresente（i in Figs．9and10，where the volumetric water（ieveloping a path from the drying primary curve to thecontent decrease（i once the matric suction increased，thewett圭ng primary cur∼7e（even t｝10ugh there was no rainfallscanning curves shown in Fig．i2had a different shapeapplied）．The delay in宅he（ievelopment of the scaming（量．e。，‘humpy’shape），since the volumetr圭c water contentcurve was due to the time needed by the in且ltrating waterto登ow from the surface of the slope model to the loca−tion of the instrumentat量ons． In terms of the shape，the scanaing curves from theof the silty sand kept lncreasing alt紅ough its matricsuction started to increase．Th量s observation was sas＿pected to be due to the di登erent mechanlsms（i，e．，ad−sorption and （iesorption） experienced b》7the soil sur一温 SC'ANNING CURVES OF T¥Vo SOILSrounding tensiometer T-14 comparedl051'ith those ex-perienced by the soil surrounding TDR-1'_ (Fig. 7). Thematric suction as recorded by Tensiometer T-14 ¥vasMstric suetion eentours (kPaj :- oon our fnten!a = 0.10 kPa* max. pressvre = 0.44 kParTlin ressure = 2.ee Pa"+*;¥ .-i,FLl ･ 1 *'!*-r'--1 _1,*_4Se--e]' '/'recovered (i.e., increased) after the infiltrating ¥vaterf'rom the surface of the model flo¥ved and passed thetensiometer tip. Ho¥vever, the volumetric water contentof the soil surrounding TDR-12 stiH increased, due tolateral drainage from the upper part of the slope model.The ¥vater from lateral drainage did not pass tensiometer' 1l O1_ Oe '**-_vir"'* .e .^+'11 )/;T-14 since its location ¥vas in the extreme lef't of the slopet/ ;-'O*' ._"'r.; 1model (see Fig. 7) and the water from lateral drainagelr.../e Te lsiome er pflo¥ved to the drainage outlet at the bottom of the slopeTDR*/ave guidemodei. The volumetr'ic ¥ 'ater content measured byTDR-12 decreased a*'ain (i.e., r'ecovered) once there vasno more ¥vater fiolv from lateral drainage, and as a resultthe scannin*' curve began to follo¥v the path of theprimary drying cur've.The effect of lateral drainage as discussed above(a) st wet eondition (i e. end of Test ll･A)M trto suction oentours (kPa) :- contouf intervai * O.10 kPa* max. pressure * 2.T5 kPa- min pressure = 5 )T kPs.!'//i: :;il/･4/..* : rli_ /･ r r/.!!' ii 1.* *appears to be due to the initial dry condition of the siltysand. If the initial condition of the silty sand was relatively ¥vet (see Fig. 10), the 'hump' shape of the cur¥'e./. + "!･･1$･･i;/ " -1/i:;; : /" ;,*!'* /:; ..-.-...//'would not occur, even ¥vhen the duration of the rainfall¥vas short (e.g., I hour'). When the initial condition of thesilty sand was relatively wet, the water phase in the soilvoids vas continuous, and as a result the matric suctiondecreased once rainfall ¥vas applied. In addition, theeft ct of lateral drainage on the shape of the scanningcurves would not exist if both the tensiometer and TDR¥vere at the same location. In this case, the scanningcurves wauld be similar to those presented in Fig. 10.The same scanning curve trend ¥vas also observed in theother stages conducted in the additional series of infiltration test (Stages II, 111 and IV). It should be noted thatthe intensity of' the simulated r'ainfall applied in thefourth stage'as significantly higher than that applied inthe first three stages. Howe¥'er, the amount of ¥ 'aterinfiltrating into the model remained the same, since theadditional water from the simulated rainfall ¥vas transformed into runoff.As was mentioned earlier, the scanning curve followedthe primary lvettin*' curve of the soil-water characteristiccurve even thou*'h the simulated rainfall had ended. Thisobservation indicated that the path of the scanning curveduring the experiment did not depend on the flux bound-ary applied to the slope model (i.e., precipitation orevaporation), but on the process exhibited by the soils(i.e., adsorption or desorption). During adsorption, thescanning curve follo¥ved the primary lvetting soil-¥vatercharacteristic cur've, while during desorption, the scannin*'curve followed rhe primar'y drying soil-¥vater characteristic curve.! t･-!･-{C5*+-'1･i) +,T :/r--IF:/ ***e Tensiometer tpTDFh･/ ve 9uide(b) at dry eondihon (i e , end of Test lii-D)Fig. 13.Matric suction contours measured in the fine sandmagnitude of the errors that could be invol¥'ed in theconstruction of the scanning curves due to the differentmeasurement locations, the matric suction data werecontoured and the magnitude of the matric suctions atthe exact locations of the volumetric ¥vat.er contentmeasurements were estimated from the matric suctioncontours. Using the same technique, the magnitude of the¥'olumetric water contents at the exact location of matricsuction measurements could also be estimated by contourin*' the volumetric ¥vater content data. Holvever,since the nurnber of measurement locations of matricsuction was larger than the number of measurementlocations of volumetric vater content, the matric suctiondata were selected to be contoured r'ather than thevolurnetric water content data. The matric suction contours ¥vere created using the computer program. Surfer'RVer.6 (Golden Soft¥vare Inc., 1997).T¥vo sets of matric suction contours were created foreach soil; one r'epresented a dry condition and the otherrepresented a wet condition. The measurement data usedError in Estilnation of'Scanning Cun'es c/ue to the Dlffe/'-to construct the matric suction contours at the wetent Locations of Tensiolneter Tips and TDR Wave-condition was taken at the end of Stage II-A (indicated byGuid espoint X in Fig. 9), ¥vhile those used to construct thematric suction contours at the dry condition ¥vere takenfrom the end of Stage 111-D (indicated by point Y inThe scanning curves presented in this paper ¥vereconstructed from the matric suction and the volumetricwater content data that were measured at the same timebut at slightly difi: rent locations. In order to quantify theFig. 9). Fi_g:ure 13 presents the contours of matric suctionsmeasured in the fine sand, ¥vhile Fig. 14 presents the l 06TA N*1 IET AL.Table 2. Differeuces in matric suction data between those Ineasured b _'Mstris suetion c0 1 ours (kPa) :* oQntov int5 val = 0.01 kPathe tensiometer and those estimated from the matrie suction contours* max. pTessure * 0.22 kPa- Fnin pressure * O 5e kPah,iatric suctions (kPa)i ; s *-Q: s_ f･ 1; 1; .-=;._._*.+;:: -.F JSoilLocatiorSoiltype condition (see Fig;'/ ,".*,t. r. .* ;･ , ',._/ ;; ,_'++.･; ..(at ¥vet iu9:IF ･+Finesand,*at drying:･ TensiometertiMat c suction contQurs {kPa>- eentour interval s O,50 kP* max. pressure :; 3.54 kPa- min pressure :2S 49Tl _59l . 85B4.264.734.534,, 1 5O. I l4 404.45O.33O.080.40O 33O.40O 34O.30O 32lO.8019.6024 OOO.06O 03O.08Ml¥*lT1, ** *comoursO.65O.95Mdryintens ometero 88BaEs imatedfrom he Differenceso.81TSihysandbyBBat ¥vet ing(a) at wet eonditlon (i e , end otTest i]･A),leasuredl¥*lTTDR wave uide8)8 9118 7524.49O.160.07O 26I .89O.852 49Pa-2:. +¥ *(.1･?: ,t ; ;: :B-'2 :l_;+: *:30_..:-*-'v es:cJ : t"*+*(,,*¥*tc:o 20o:5u'c'e TensiometertipTDR w ve guideIISSl ,:' iOc(b)tdryeondition (ie end ofTestili-D)Fig. 14. Matric suction contours measured in the silty sandcontours of matric suction measured in the silty sand.The matric suction contours sho¥vn in Fi**s. 13(a), 13(b)and 14(a) have a small range bet¥veen their maximumand minimum values, indicating that the matr'ic suctiondistributions ¥vithin the slope model ¥vere relativelyuniform. However, this ¥vas not the case in Fig. 14(b),¥vhere the differences bet¥veen the maximum andminimum valuesvere quite significant. It ¥vas alsoobserved from the experimental data that the gradient inmatric suction ¥vas lar_ e in Fig. 14(b), indicatin*' that thesilty sandvas still experiencing draina*'e. In other ¥vords,the matric suctions in Fig. 14(b) were still changin_ ,ho¥vever the rate of matric suction or volumetric ¥vatercontent changes ¥vas r'elatively small.From Figs. 13 and 14, the matric suctions at thelocations of the TDR ¥vave-guides could be estimated.The matric suctions obtained from the contours (i.e.,Figs. 13 and 14) were then compared with those measuredby the tensiometers (i.e., used to create the scanningcurves). By comparing these matric suction data (asshown in Table 2), the magnitude of errors involved in.E;LuoO 5 1 O i 5 20 25 30fvleasured mairic suctions (kPajFi**. 15. Comparison of matric suctions*bet vee lmeasured andestimated data (refer to Table 2)comparison of matric suctions measured by the tensiometers and those estimated from the contours are presentedm Frg. 15. The resulting scanning curves ¥vould be in thesame region and would have the same shape as sho¥vn inFrgs. 9, 10 and 12, ¥vhen the matric suction data ¥verecorrected according to Table 2.Effect of Fine Content on Scanning CurvesFigure 16 presents the scanning curves for both finesand and silty sand measured at the middle of the slopemodel (i.e., point M). The matric suction and volumetricwater content data ¥vere obtained from tensiometer T-34and TDR-52, respectively. The infiltration tests used toobtain both scanning curves ¥vere also the same (Fig. 8).The primary drying and primary wet,ting curves of thethe matric suction data used to create the scanning curvesdue to the different locations of the tensiometer tips andsoil-¥vater characteristic curve are also sho¥vn in Fig. 16.TDR ¥vave-guides can be estimated and quantified.As can be seen from Table 2, the difference inscanning curves at the bottom and top part of the slopemodel (i.e., points T and B).magnitude of matric suction (in kPa) obtained from thedifferent methods ¥vas relatively insignlficant. Theexperiments, the changes in volumetric ¥vater contentsSimilar observations were found ¥vhen comparing theFor the matric suction ranges observed during the SCANNING CUR¥,ES OF T¥VO SOILS¥vettin_ : cur¥'es, but also rnoved along the primary- 40 '. --___;i_/ (siity s nd - W):; *'¥'_-' " _:*i¥ Scanning*-''' '*.,*rl _ ourvess:ov(1)-/;r^ ' ' ' ' ' ';t 'i::･tf/f'allprim ry wetti g curve(silty s nd -D)20c,{ ne s nd - W)E:: 10/¥¥¥ (L¥//)"'i "Prlm8ry dryjng cvrve'n'vas transferred to infiltration.Numerical methods such as the finite element or finitedifference techniques ha¥'e become a necessary tool for, primary Y/ettlng curveQ)vertingcurve during adsorption and along the primar'y dryin_( ._cur¥'e during desorption. This observation was consistentvith the ¥vater balance measurement, and there ¥vas norunoff observed in the experiment. In this case, all rain-Pfimary drylng curvel:;aJ 30107solving infiltration problems. Numerical analyses are"D")'S>usually preformed using the drying soil- vater characteristic curve, because the soil-1vater characteristic curve isO10O2aMatrie suction, {u -ut') (kPajFig, i6, Comparison of scanning curves measu ed on siltl.' sand andfine sand (from experimental data at location of point M)observed in the fine sand ¥ 'ere significant as comparedthan those observed in the silty sand. This difference ¥¥'ascommonly determined follo ving a drying process. In thecase, ¥vher'e both drying and ¥vetting soil-¥vater char'acter-istic curves are available, numerical analysis of theinfiltration process ernploys the ¥vetting soil-¥vater charac-teristic cur¥'e while the drying soil-¥vater characteristiccurve is used to sirnulate e¥'aporation.By examinin_g: the scanning curves obtained from theexperimental data presented in this paper, the use ofdue to the difi rence in the amount of free ¥vater in thesoil skeleton. Free ¥ 'ater is the soil ¥vater that can ber'emoved from the soil by applying a difference in totalhead or a hydr'aulic gradient. For a specific volume ofsoil, the amount of free ¥vater in the fine sand was largerthan that in the silty sand.drying or wetting soil-¥vater characteristic curves in theUnlike the changes in volumetric water content,desorption process, the scanning cur¥'e follo¥ved the primary drying soil-¥vater characteristic curve, regardless oflvhether the soil ¥vas subjected to precipitation or evapor'ation. Therefore, the appropr'iate hydraulic parametersof the soils (i.e., drying or wetting) should be used according to the process that the soils actually experience(i.e., desorption process or' adsorption process).lvlost of the available numerical rnethods sol¥'e thechanges in rnatric suction observed in the silty sand had alarger range compared vith those in the fine sand. Inother ¥vords, the changes in matric suction lvere moresensitive to changes in volumetric 'vater content in finegrained soils compared with those in coarse-*'rained soils,especially in the high water content/lo¥v suction regime.This is due to the fact that in the lo¥v suction re*'ime,¥vhere the soil has a hi**h volumetric vater content, thelvater phase in the soil skeleton ¥vas continuous. As amodelling of vater flo¥v in unsaturated soils can berevie¥ved. During the adsorption process, the scanningcurve follo¥ved the prirnar'y ¥vetting) soil-¥vater characteristic cur¥'e, regardless of vhether the soil was subjected toprecipitation or evaporation. Similarly, during theseepage problem in terms of pressure head, and thencalculate other necessary parameters, such as waterresult, an increase or a decrease in pressure from thecontent, flo¥v rate or' water storage, based on the pressureinfiltrating ¥vater ¥vill be transferred directly to a changehead obtained. Figure 17 illustrates the error that couldin matric suction of the soil.take place in the calculation of the volumetric lvatercontent when the drying soil-water characteristic curveFrom the abo¥'e observation, for the matric suctionran*'es observed dur'ing the experiments, it can beconcluded that a small chan*･e in the volumetric watercontent of the fine-grained soil does not mean that thematric suction does not chan*"e significantly. On the otherhand, a small change in the matric suction in the coarse-grained soil does not mean that the volumetric ¥vatercontent does not change si**nificantly.In terms of the water storage capacity of the soils, itwas observed that the longer the scanning cur¥'es formedduring infiltration, the larger the amount of ¥vater ad-sorbed by the soil. During the twenty-four hour simulation, the scanning curves of the silty sand only movedbetween the primary dryin*･ and the primary wettingcurves in an almost horizontal direction, indicating smallchan*'es in the volumetric water content of the silty sand.This observation ¥vas consistent ¥vith the water balancemeasurement, where most of the rainfall applied ¥vastransformed into runoff in the silty sand. On the otherhand, the scannin*' curves observed for fine sand did notonly move bet¥veen the primary dryin*' and the primarywas ernployed in t.he simuiation of infiltration in unsaturated soils. For the same matric suction changes (initialcondition at point O), the volumetric water' contentsmeasured using the drying soil-¥vater characteristic curve(indicated by point Q) were significantly higher comparedhvith those measured using the scanning curve (point P).The error in the calculation of the volumetric watercontent ¥vill lead to an error in the calculation of the¥vater balance.CONCLUSIONSThe scanning curves and the primary soil-¥vater char'acteristic curves of t¥vo soils (i.e., silty sand and fine sand)have been presented in this paper. It ¥vas found that thescanning curves followed the primary ¥vetting curvedurin*' the adsorption process and then f'ollowed theprimary drying curve during the desorption process.During the transition bet¥veen the t vo primary curves(i.e., dr'ying and 1¥'etting), the scanning curve had a rela- 禰108TAMI ET AL。606）Fredlund，D．G．and Xlng，A．（1994）：Equations for thesoil一、、・ater characteristlccurve，Cσ∼7、Gθo∫θch．ノ．，31（3），521−532． 7） Golden Software Inc、 （1997）： U5θ1巴∫ G∼”oFθ 、ノ10ヂ S1〃プセ1門 vθr。6，i Q界鷹の一 40鵬 旺πor incalculatior…ofoo ￥ （1988）：ApP玉ication of a s玉mple so1レwa【er bysteresis model，／α！η1θ1、vwater con皇ent弦8）Hogarth，W，Σ．，Hopmans，J、，Parlange，」．・Y、and｝｛averkamp，R． ￥volumet舜Cの駕 Golden，CO。、￥、￥ 0ゾHア4rology，98，2ま一29、99）王wata，S。，Tabuch玉，T．and、Varke距t1n，B、P，（1995）：30’1JVα∫θノ「お 20 11πθ1ηα’oη5，NewYork，Marce1Dekker，Inc．Pi殉哨、』胃隔 0εヨ10）Lambe，T．W．（1951）：So’1rε∬加g，弄oノ’￡ng加θε1写，New York，Jo自no＞ ∼V員ey and So【｝s夏鷺c．01びn）Leong，E，Change恥ma象jcsuctionC、an（i Ra｝1ardjo，H，（1997）；Revlew of soi1−waτer characteristlccurveequatio跳s，（｝θαθ‘11．Gθoθηvか017．E119’“9．，100101壌02103Matricsuction，（Ua−Uw）（kPa） ASCE，123（王2〉，1三〇6唄17．12〉Liu，Y．，Parlange，」、一Y、，Stee！出uls，T．S．and擁averkamp，R （1995）：Asoll−wate出ystereslsmodelfor負ngeredao、、’data，μ■鯉ヂFig．17， 葦deβ鷺ized pa重h of so蓋1幽waIer ch貸ra（：terist量c curve used in重he numericaisimulaIionofin61芝r謎110nprocess（dec臓sei臓m9亘rlc suαion） 1∼ε50ε〃℃ε5ノ∼ε5a7ヂch，31，2263−2266．B）Mualem，Y．（1974）：A concep田al of無ysτeresis，｝殉’θr Rε∫α’κε5 ノ∼e5α71でh，12，514−520．14）Nimmo，J．R，and Ml11er，E．班．（1986）：The temperaωre depende賢ce of1sotbermal moisture vs po【ent玉al c員aracter玉s“cs oftively Ha毛slope compared with the slope of the pr量marycurves，an（i sometimes it was almost koτizontaL solls，So〃Sc’θ刀cεSoc’θひ》11ηθ’“’cρ／0置’r〃α1，50，1105−HI3．玉5）Parlange，．1、 一Y、（1976）：Cap玉貝aryむysteresis and relationsh玉p be一 芝weendrylngandwett玉ngcurves，肋∫σ1∼θ50縦ε51∼ε∫θαrc1∼，12（2），However，the s至ope and path of the scanning curves were 224−228。found to be similar for the cases wlt熱simllar initial condi−16）Pわam，員．Q。，Fredlund，D．G．andBarbour，S．L（2003）：Apractl−tions． 1t was observed from the scanning curve of the且nesand that a small change in matτic suction can cause a ca1ぬysteresis modei for dle so11−wa乞er characteristic curve for so琵s wi由negliglble volume c目ange，Gθ01θごh11’σ∼’θ，53（2），293−298．17）Poulovassi1玉s，A．（1970）：Hysteresis of pore water 1n granular porousbodles，／α’η1α10∫So〃S‘1θ17cθ，1G9（1），5−12、signi負cant change in water content。On tぬe other hand，a18）Poulovass澁s，A、and C翻ds，E C（圭971）：丁鼓eねysteres1s of porelarge change ln the matric suction in the silty s＆nd might water＝t員e no玲一independence of doma圭ns，．10∼’η∼α10ゾSo〃S（ゴ（∼ηα∼，not change its water content signi且cantly． 112（5），30レ312、玉9）Publlc Works Department（互976）＝丁瓦e Geology of tbe Republic S1ngapore，Si鷺gapore，20）Rahardjo，H、（2000）l Ralnfalhnduced slope fa賛魏res，NSTB Rep．ACKNOWLE、DGMENT 17／6／16，scl曳ooiofclvllandstructuralEngineerlng，Nanyang The work（iescribe（i is supPorted by researc鉦9τant No． Tecぬnological Univ．，S玉ngaPo「e．RG7／99 from Nanyang Technologlcal Unlversity，S量ngapore，The貴rst author ackno、v正edges the discussion21）Si，B．C．and Kachanosk圭，R．G．（2000）＝Un玉且ed sdut玉on for in一 丘hra亘on and drainage w玉tぬ熱ysteres玉s；τheory and ae豆d tes【，5011 Sc’ε17cθ50c’θひ㌧4’ηε1ブcα／0置〃’nσ1，64，30弓5．and the advlce glven by Prof．D．G．Fredlund from t熱e22） Soilmo1sture Equ圭pment Corp、（1996）＝OPθ1’αf’η9／’15〃P∼’α’o’∼ノ101’University o郵Saskatchewan，Canada，especially at t熱e 7γθ5θβE6050κ1，Santa Barbara，CA．beginning of the study，and also t薮e research scholarshiρfrom the Nanyang Technologlcal Unlversity，Singapoτe．23） Talsma，丁．（1970）：Hysteresis 玉n two sands anc玉tbe玉adepeI｝dent domaiamode1，肋’θ1ト1∼ε5α〃℃ε51∼θ5θακ11ほ5，95−102，24）Taml，D．，Rahardjo，H．，Leong，E、C andFredlu【1d，D．G．（2004）l Apねysicalmodelforcaplliarybarriers，Gθo’θご1∼．rθ5∼．／．，27（2），REFERENCESi） 、ASTNI D2325−68，（1994）：S芭andard Test N歪etぬod for Nleas廿reme鷺t 王73−183．25）τopp，G．C．（1971）：Sollwaterhystereslsinslldoamandclayloam soils，蹄■θごθ71∼θ50μヂcθ51∼ε5θμノ・c1∼，7（4），914−920、 ofMolstureC鼓aracterlstlcCurveUsi貸gaTempeCe11，加11μα126）τoPP，G、C、and MiHer，E．E（豆966）1｝｛ysteresls moisturecharac− Booんo勇4S7ン》S∫σηぬr4∫，04．08，Soll and Rock．American Society terist玉cs and ねydraulic conductivi亘es for glass−bead 職edia， Soil for Test塗g and Maεerials（ASTM），峯》賊adelphla，Pa． Sc’θ17cθSo‘初屑’ηθノ加Pro‘．，30，三56−162．2）13raddock，R．D．，Parlange，J．7Y．andLee．，9．（2001）：Appllcation27）Vachaud，G、andnony，，L−L（1971）：擁ysteres1sduringin最kration of a so玉i water蝕ys【eresis mode蓋to simple water re監e【玉tion curves， and red1stribution in a so玉1column aτdifferen置玉aitial water content， 1二1’‘7’1，∫poヂ∼”∼Po1’oま’∫A（1（∼グiα，44，407−420。 肋’eノ’ノ∼θ50置’κθ51∼ε5θσκh，7（1），11H27、3）Brooks，R．H。aadCorey，A．L（玉964）：Hydraulicpropertiesof28）vanGe照chten，M．丁短．（1980）＝Aciosedformequat1onforpred1α一 porousmedia，∫かゴrolo＆yP叩θβ，ColoradoS職eUnlversity，Fort 玉ng t1｝e｝1ydrat王1玉c conduct圭v玉τ呈es of u【玉saturated soils，Soll S〔ゴθn（コθ Colllns，CO，1−27． Soc’θり厚11ηθr’oα／α’1’nα1，44，892−898．4） Feng， 氏4． and Fredlund， D． G． （1999）： Hystere［ic inf至uence29）Vlaene，P、，Vereecke鷺，H，，Diels，J．andFeyen，」．（1994）：Astat1stl− assocla【edwl由由ermalconduαivltysensormeasurements，Pノ呼oc． calanalysisofslxhystereslsmodelsfor撒emolstureretePtion ヵ’01η7＝hε01ッfO11∼θP辺α’ごθo∫Uη、∫硫〃’α紹ゴSo〃Mθ‘1∼θ1∼1c5，ln c員araCter玉St玉c，30〃Sc’θ7cθ，薫57，345−355． assoclation w玉th52nd Canadlan GeQtec姓nical CGnference＆30）Watson，K．K．，Reglnato，R．」、and Jackson，R．D．G9フ5）＝Soil Unsatura芝ed So註Group，Reg玉na，14：2＝14−14：2：20． wa芝e出ystereslslna員e！dso録，So’1Sぐ’θηc8Soc初屑1ηθノf‘αP1’ocθ．，5） Frediund， D． G，and Ra｝｝ardjo， ｝｛， （1993）： So’1／》8chθ’1’o∫ノio1’ U’1∫α躍1’σ’綴SoiZ∫，New York，John Wlley and Sons Inc． 39（2），242−246． | ||||
| ログイン | |||||
| タイトル | Improvements in Nuclear-Density Cone Penetrometer for Non-Homogeneous Soils | ||||
| 著者 | M. Karthikeyan・T.-S. Tan・Mamoru Mimura・Mitsugu Yoshimura・C. P. Tee | ||||
| 出版 | soils and Foundations | ||||
| ページ | 109〜117 | 発行 | 2007/02/15 | 文書ID | 20984 |
| 内容 | 表示 SOILS AN D FOUl¥,DATIONS Vol47, No1,l09- 1 1 7,Feb2007Japanese Geotechnical Societ}IMPROVEMENTS IN NUCLEAR-DENSITY CONE PENETROMETERFOR NON-HOMOGENEOUS SOILSMUTHUSAh, Y KARTHIKEYANi), THIAhl SOON TAN'ii), MAi¥,roRU MI*¥,IURAiii), MITSUGU YosHih,1URAi+)and CHooN. PENG T E )ABSTRACTIn Singapore, the use of clays from mar'ine dredging and land-based construction activities as fill for land reclamation provides a solution to the problern of disposal ¥vhile turning such un¥vanted soils into rnaterial of economic value.A major problem ¥vith such fill is the formation of very hi**h degree of heterogeneity in the *･round. The characterization of such ground at different stages of land reclamation ¥vorks poses a major challenge as many traditional in-situtests ¥vhich provide point values are based on solutions deri¥'ed assuming the ground is a continuum. A major sitecharacterization program ¥ 'as carried out as part of a research project. The Nuclear-Density Cone Penetrometer isemployed for site investigation to measure the continuous changes in density together with other usual coneparameters. The tests have been conducted at var'ious stages of land reclamation vorks. In the present paper, theproblems faced in marine based investigations associated with the use of an existing Double Probe Nuclear-DensityCone Penetrometer are briefly discussed and this limitation has led to the development of a ne¥v Single Probe NuclearDensity Cone Penetrometer lvhich is the main focus of this paper. The wet density profiles obtained from the SingleProbe Nuclear-Density Cone Penetrometer' are compared ¥vith the double pr'obe and the comparison sholvs a verygood agreement.Kev words: land reclamation, Iumpy fill, natural radioactivity, nuclear-density cone penetrometer, vet density (IGC:C3/D3)INTRODUCTIONDred..,*Oing ¥vorks in the coastal areas and excavations inSanti Fiurban areas produce large quantities of unwanted soils inSingapore. As ther'e are no land fills in Singapore, thedisposal of such soils pose an almost intractable problembecause of' the ver'y large volume involved. The use of""*;* /"""; 1'rl/" (e 'o, :/' t /'Fio.･,･ f;i;ua/ '(':(/=_.1;/""/1';rl",_.1" '1 1:<)O:u//; ;; , 'Aj 4TS2t/7(*.j''' ; ',; :////;;f ' ': ;e j'."'Dredged Big C[ays:Lumps: .(l /' .:1" . ;. ' s .F;.."j""_*//;;(: i ,'( e.'//'/ ' f/// ' =//. .![nte r-lump voidsfilled w'th smallclay lumps andwater1. Schematic profile of reclamationlyitilcla . Iumps(af terKarthikeyan et al., 2004)with large voids bet veen them, the inter-lump voids.These inter-lump voids can be filled vith small claythat there is little information on the behavlor of thelumps, slurry and/or water, as sho¥vn in Fig. 1. A majorchallenge in this project is the characterization of suchtype of "lurnpy" fill. A revie¥v of the literature suggestslurnpy fill in the field, except surface settlements(Casa*'rande, 1949; Whitman, 1970; Hartlen and Ingers,i981; Bo et al., 2001).Visiting Scholar, Department of Civil Engineering, Nationai University of Singapore, Singapore.Associate Professor, ditto.Associate Profcssor, Disaster Prevention Research Institu e, Kyoto University, Uji, Japan (mimura * :eo ech dpri.kyoto-u,ac.jp)-General l¥,lanager, Soil and Rock Engineering Co. Ltd., Toyonaka, Japan_Surbana Internalional Consultams Pte Ltd., Singapore.The manuscript for this paper was received for revie¥v on June 8, 2006; appro¥'ed on September lO, 2006¥Vritten discussions on this paper should be submitted before September l, 2007 to the Japanese Geotechnical Society, 4-38-,-, Sengoku,Bunkyo-ku, 'Tokyo 1 1'_-OOI 1, Japan. Upon request he closing date may be extended one month.109,' "; jSeahedsite. The resulting fill is highly heterogeneous, characterized by a structural matrix formed by large lump of soils,Y.*o' G : '" " *"'/''<effective, they were dumped directly into the reclamationJ* )'/r/// : /(. i;//"i/ ;>rl//f e / e (: 7 0<:s' / i ;li :e :': "'^ ,;1( o ' / f ' '/ : ]' 'i;' '///(';);///i (/.'i'/.for land reclamation, pro¥'ides a sensible alternat.ive andiii7l,J """".g,*,',:=is no¥v implemented in the 1500 hectares Pulau Tekongreclamation project ofl' the northern eastern coast ofSingapore.For such innovative use of unwanted soils to be costi;'/'/;//z/'; ' ii. . ･such soils as fill for' Singapor'e continued growing appetiteii)' KARTHIKEYAN ET AL.llOFor a lumpy fill, retrieval of undisturbed samples isnear impossible especially at the early state ¥vhen inter-<1)- t 1lump voids are big. Most in-situ tests are based on theresponse of a continuum to a simple probe such as a conepenetr'ometer or a fiat plate (dilatometer). The existenceof a loose lumpy matr'ix with large voids makes meaning-ful interpretation of the obtained point ¥'alues verydifficult. One parameter' that can complement the usual****Fig. 2. Diagram of Nuclear-Densit) Cone Penetrometer: (a) Cableleading to data collection s .'stem, (b) Preamplifier, (c) Photomultiplicr tube, (d) Lead (Pb) sl]ield, (e) l;7cs gramma-ral.' source: Alldimensions are in milli leters (after Shibata et al., 1993)cone parameters to provide a deeper insi*･ht to the gr'oundcondition is the density of the fill.A Nuclear-Density Coue Penetrometer (ND-CP) hastional Society for Soil Mechanics and Foundationbeen sho¥vn to be able to measure reliably in-sltu ¥vetEn_g:ineerin*' (ISSMFE, 1989) for' cone penetration test-density of a soil (Shibata et al., 199'-; 1993; 1 994; Mimuraing, namely the diameter is 35.6 mm, the apex angle iset al., 1995; 1999; Mimura and Shrivastava, 1998;60', the base area is 10 cm2 and the area ratio is 0.75. AShrivastava and lvlimura, 1998). This cone penetrometerporous ceramic filter is located just behind the cone tip.The total length of the shaft housing the sensors is 258mm. After this, the shaft tapers out¥vardly at an angle of¥vill provide information of the density of a small volumearound the probe, over and above the usual coneparameters of cone resistance (q*), sleeve friction (f*) andpore pressure (u2).These researchers have focused on the use of theextensively ND-CP in naturally deposited clayey andsandy formations. Since then, this tool ¥vas used toprofile the **round in a reclamation project in Singapore,in ¥vhich the fill is formed by clay lumps and is highlyheterogeneous (Karthikeyan et al., 2001, 2004; Dasariet al., 2006). The interpretation of the results from suchNuclear-Density cone penetration test (ND-CPT) ischallenging (Karthikeyan, '-005) but ¥vhen done properly,can produce meaningful results.The existing design of the Nuclear-Density ConePenetrometer requires t¥vo probing for every single15'. The tapered portion of the shaft is 49 mm long andbeyond this, the shaft has a constant diameter of 48.6mm and extends for a total length of 896 mm. This upperpart houses the radioisotope source, the detector, and apreamplifier. The gamma ray source used in the construction of the Nuclear-Density Cone Penetrometer is theCesium (Cs!37) isotope (primary source of radiation is a3.7 MBq) ¥vhich has a half-life of 37.6 years, and thedetector is sodium iodide activated ¥vith thallium (Nal(TI)) scintillator mounted on a photomultiplier tube. Thelen*"th of the Nal scintillation detector' is 10.2 mm. Theseparation distance bet¥veen the source and the center ofthe :amma detector is 25 . mm.The ND-CPTs ¥vere performed according to thelocation; first, to obtain the background count of natu-procedure for standard piez,ocone penetration tests, asrally occurring gamma photons and then to measure thespecified by British Standard, BS 5930: 1999. During test-actual nuclear density (RI) count. The natural radioactiveing, the ND-CP was pushed into the ground at a rate ofapproximately 1-2 cm/s and cone resistance (q*), sleevefriction (f*), pore pressure (u2), RI count and back-count (background; BG) is inevitable and needs to besubtracted from the total count measured to give a countthat is better correlated to the density to be measured.The natural background count itself is also related to thesoil that is being: studied and this issue is also examined inthis paper. This requirement for two probings causes anumber of serious practical difficulties in the investigation ¥vhen the surface of the fill is belo¥v sea-level (sub-marine condition) and the tests need to be carried outfrom barges. In searchin*' a solution to these practicaldifficulties, a ne¥v Nuclear-Density Cone Penetrometer¥vas designed ¥vhich requires only a single probing. Thispaper ¥vill discuss the issues involved in this development,DESCRIPTION OF NUCLF,AR-DF.NSITY CONEPF.NF.TRATION TEST (ND-CPT)The Nuclear Density Cone Penetrometer used in thepresent study is based on the design of Shibata et ai.(1993). Fi**ure_ sho¥vs major components of the Nuclear-Density. Cone Penetrometer. The lo¥ver part of the conehouses ¥'arious sensors to measure the three typical coneparameters, namely, cone resistance (q*), sleeve friction(f*) and pore pr'essure (u2). The size of the lower partconforms to the standards recommended by the Interna-*'round (BG) count ¥vere recorded continuously. Thedetailed description and working procedure of ND-CPT¥vas reported in Shibata et al. (1993) and calibrationissues have also been discussed by Shibata et al. (1993)and Dasari et al. (2006).LAND RECLAMATION USING BIG CI,AY LUMPSAs part of the construction of the bunds surrounding:the area to be reclaimed, Iar*"e dredged clay lumps of upto about 8 m3 in volume ¥vere exca¥'ated usin9: clam-shellgrabs to form a trench for the construction of a sand key.A typical clay lump dredged from the seabed is shown inFig. 3. The physical properties of these stiff clay lumpsconsists of about 50/0 Sand, 550/0 Silt and 400/0 clay sizedparticles. These stiff clay lumps have a natural moisturecontent of 600/0, Iiquid limit of 770/0 and plastic limit of360/0 . These dredged clay lumps are placed in a bar*"e andtransported to a reclaimed site, ¥vhere the lumps aredlscharged on to the seabed up to l-2 m belo¥v the sealevel. This depth is needed to cater for the draught of thebarge dumping the lumps. Sand is then used to cap the filland to provide the surcharge to accelerate the consolida- fNUCLEAR-DENSITY CONE PENE'TRO*METERlllW!arillB Cone Penetration S stemD'mensions ofPiatfor t: 80 ftx2S ftCounter wetght =O tonDlame er of Counter weight = 3.4mContro Un't/ }iil:;!';i:::: i: s T:::j Hydraulic penetration systemReaction frame or Tawer andS;SSSS-' '-"""? S;'Frg. 3. A typical big clay lump obtained using clam-shell grab^ =isFig. 4. Photographic view' of the Marine Cone Penetration S1.'stemused in Staee 1tion. A schematic section of the reclamation site ¥vithdredged clay lumps and sand surcharge is sho¥vn in Fig. I .crawier was used to carry out the ND-CPTs.During the early stages of reclamation, there would belar_ e ¥'oids bet¥veen the big dredged clay lumps and theseinter-lump voids (void bet¥veen lumps) could be partlyfilled ¥vith small lumps, slurry and/or water. The keyproblem vith a lumpy fill is the very high degree ofheter'ogeneity due to a very porous structural matrixformed by the lumps (Karthikeyan et al., 2004). Thecharacterization of such a ground at different stages ofiand reclamation works poses a major challenge, and theND-CP has proven to be an effective tool to character'izesuch a ground (Dasari et ai., 2006).FIELD INVESTIGATION LAYOUTIn this paper, the results from one of the 3 field pilottests (TA 2) will be discussed in greater detail. The pilottest area (TA 2) is 100 m in length and 100 m in width.The clay lumps ¥vere placed directly on the seabed whichis about - 1,3 to - 14 mCD by bottom-opening barges toform an 8 m to 9 m thick lumpy fill layer from June toAu*'ust 2002. 120 numbers of marine ND-CPTs wereconducted from August to November 2002 (Stage 1).Subsequently, 7 m of sand was placed in several lifts upSITE INVES1'1GATIONto +4 mCD over a period of 10 months. Then, another120 numbers of ND-CPTs were conducted fromThe field ¥vorks to be described ¥vere carried out at theDecerrrber 2003 to March 2004 (Stage 2) with the inten-1500 hectares Pulau Tekong Reclamation project off thetion to be over the same location as in Stage I . However,northeast coast of' mainland Singapore. The projectit ¥vas impossible to ensure that the ND-CPTs werecarried out in exactly the same locations because ofbegan in 1999 and is still ongoing. Thr'ee field pilot tests(TA 1, TA 2, and TA 3) were conducted in this project.inevitable surveying setting-out errors of about d: 0.5 m.The site investigations ¥vere carried out using a Nuclear-While such a small deviation usually does not pose anyDensity Cone Penetrometer. Thus far, the state of theproblem in a site investigation, in this project, this is aproblem due to the lumpy nature of the fill.The investigation plan carried out at TA 2 for Stage 1and Sta*'e 2 is sho¥vn in Fig. 5, which consists of a smalldense grid set vvithin a big grid. The big *"rid is 99 m x 100m and the small grid is 10 m x I I m. The small dense gridis highlighted as 'A' in Fig. 5. The big grid consists of I lOlumpy fill at t¥vo different stages has been profiled. Thefirst stage is immediately after placing the dredgedmaterials in the reclamation area up to -3 mCD (metreabove chart datum; chart datum is taken as mean sealevel) and the second stage is immediately after dumpingthe capping sand, up to +4 mCD. The third stage will beat the end of consolidation, ¥vhich has not been reachedyet .In Stage l, as the surface of fill is below sea level, ND-CPTS vere performed using a Marine Cone PenetrationSystem, as sho 'n in Fig. 4. The control unit and thehydraulic po¥ver unit were placed on a barge. A hydraulicpenetration system, which was mounted on steel frame ortower, was lo¥vered on to the surface. The reaction forcewas provided by the dead lveight of the steel tower. TheND-CPTs and the small dense *'rid has 10 ND-CPTswithin a 10 m x 1 1 m ar'ea, an extremely closely spacedarrangement. This arrangement ¥vas designed to provideadequate information to characterize a representativevolume of lumpy fill and also to provide sufficient idea ofthe variation.barge is equipped with a four-point anchor mooringPROBLEMS FACED IN SUB-MARINEINVESTIGATIONsystem to secure the barge in position and to maintain itsstability during operations. In Stage 2, Iand is alreadyProblems in the sub-marine investi*･ation in Stage lcome mainly from the fact that the current desi**n of theformed above the sea level and thus a conventional CPTNuclear-Density Cone Penetr'ometer requires t.wo prob- 噸112KARTHIK狂YAN ET AL． 等 2 3 4 1： 1∼ 13 ¶4 7 5 9 10Background count（CPS）Background count（CPS） 1 0 ！00 200 30G 0 100 200 300 1 I 21 22 2ユ 2‘ 25C 27 23￠ 圏 3000t ∼5 17 ¶8 当9C 2P55 1 響 3¶ 3z 320 34 言喜0 37 33 コ9 磁c ［ 1輔m l 41 42 4コ 4‘4 4ξ 47 48 49 50警，， ，2 53点1．㊦ 1硲麺 1 引 52 53 64 1 76 77 78 75 εO 5I B2 B3 94 ε6 5ア 33 8肇 50 1ぎ 1 田c 92 閃 寺 94十雲 1桶｝ ＄1mゆ 1CI lO2 IO息 104Eε彰15・二 15ボ審αooo5’ ε5 67 53 63 70 1 1 7！C 72 73 7‘101020202525（b〉（a）30309 56 97 雪a 馨oo l ∼05 107 ｛oa lo9 110鋸釣一Drammenαay（Norway） Kinkai Bay（Japan）一Hachirougata（Japan）9曾m一Holmen Sand（No四vay） ・Vancouver Sand（Canada）一Kamigawa Sand（Japan）一Higashi Ohgishima Sand （Japan）（a）Fig，5（無）． Laぎoul of ND・CP■i臓site lnvesIig寂Ilon飢TA2（Stages lFig，6． Typic田backgrou臓d coun重pro61es obtained forhomogeηeo糊s so韮ls：（謎）ciay deposi重and（む）s段ndy depos董重s（Nobuyama，2000） and2） RI count（GPS）Background count（GPS）0o備◎則O600 800 1000 1200 50 董OO 150 20025030045一一一一RI45 −R葦111 1 F己115一一一一RI116一一Ri45−R！111 隠115一…R捌6一一RI118●働卿RI120− Rl｛18繭。。 Fご120−AveragεBG一5一5 ND−CPT 1至5 121 1−1 ，．画笥 1 ，！Qo篶ooE） 一10） 一105￡一一一“一一→o 気＿ 辱 ．ぎ器＄Ωぐ（b）』葦偽旧ρ一15・土！メ≧・∼ンFig．5（b）． De臓iled ND−CP■1段you｛郎10c謎tlon‘A少iη重he si題e invesIト一15 胤 ’ o’ 9段llon 鍾（a）一20穫1二驚（b）一20ing for every sing至e measur量ng Point，負rst to obta量n theb＆ckground count of natural rad量ation an（i then theFig。7、 Typic朗promes ob絵lned for highly heIerogeneous lumpy欄1；actual nuclear density（RI）count，so as to obtain the net （a）魏ckgroundcounωnG（わ）Rlco蝋gamma−ray count to determine the act疑al nuclear densitymeasurement．The backgroun（i count is measured using acone which contalns only a detector and no gammasource． Figure6shows the typ圭cal bεしckgroun（i count profi重esw量th（iepth obtained for a number of natura至soils．It canCPTs are very closely spaced within a 5，0m×5，5msquare grid，very s量gni負caat var量ε珪ion圭n RI and back−groun（1count pro盒星es can be observeci，a consequence oξ由e fact that the lumpy且11is highly heterogeneous，Withtむ藍s degree o￡var圭at圭on in tむe backgrQund count，the usebe seen that for these natural soils，there are里ittleHuctua−of any averaged backgrouncl count pro盒重e is likely to betions with depth．豆f the soil is homQgeneous and thevariation in the backgroun（i count prof涯e1s neghgibleproblematic．Figure7（a）s勤ows an average backgroundwithin a test site，then（ioub重e probes are notτequ呈re（i，aserrors from slight var量ation in location wiII be negligible、Figure7 s｝10ws the backgroun（i an（i RI count profilescount pronle obtainecl for the above six茎）ronles．If theaverage backgroun（i count pro釘le is use（i together withthe actual RI counts shown in Fig、7（b）to determlne thewet density，then an error o｛about10％is observe（i圭n theobtained郵or the lumpy負II slte＆t locations R互45，RI lH，estimated wet density as shown in Flg．8for locations RIRI115，RI116，RI H8and RI120，which arein the small45and RI115．To reduce the error in such a highlydense grld，s紅owll ln Fig。5．Althoug封all the six N五）一勤eteroge勲eous豆umpy盒11site，it is necessary to carry out NUCLEAR-DENSITY CONE PEN ETRO¥.,IETERoWet Oen$ity (kN/m3)Wet Density (kN/mG)12 1412 14 Ie 8 20-RI56 18 20o*- R145-Ave ge BeCLO200=oOE-oErQ(ce>o*__101 o1 ooo800600Maxir lum r dius o400io-2020O3a40Distance frorn edge of cham er (cm)1 5Filg.-20Jer ce200O1 5iTlzone s abovt23 e cmuJeoc:1 4aoc:(::aoEv1 600(1'- Average BG-o1l _9. ¥_ ,Iaximum radius of the influence zone ofment in water (a:ftcr Karthikeyan, 2005)Fig. 8. Comparison of esrimated wet densit) using actual measvredbackoround count and averaoe backcrround count400eND-CPTmeasure-Kaoiin Claycl)fO 300t¥vo probings at every single measuring point, and the t¥voprobings need to be located precisely at the sarne hole.In a sub-mar'ine investi**ation (Stage 1), it is ¥'erydifficult, time consurning and expensive to ensure that thet¥vo probes conducted at two different timings are pusheds::soO 200c:::soS OO:through exactly the same hole due to operationalCQdifficulties. In reality, the variation in the t¥vo differento100probings ranges from O. 15 m to I .5 m. The data shown inin location. This high sensitivity to location ¥vill affectseriously the accuracy of the measured density for the1 2040eO80 200 220 240 260Water Oontent ( .)Fig. 7 sho¥ ' very large variation e¥'en ¥vith small variationFrg 10. Laborator) results sholving variation in the BG count vaiuewitb various water content of soilhighly hetero*･eneous fill encountered here.Befor'e discussing the new development, at this juncture, it is important to have a better understanding of thenat.ur'al radioactivity in soils. Ther'efore, an investigationwas carried out to e¥'aluate the fact.ors infiuencin9: thenatural radioactivity (background count; BG) in soils andthis is discussed next.Therefore, a stainless steel chamber of' diameter 700mm and height 1000 mm vas used to carry out theexperiment. In the first series of tests, onl), kaolin clay¥vas used and slu 'ries of dift rent ¥vater contents ¥vereprepared. The physical properties of the kaolin claysho ved that it consists of about 870/0 clay fraction andINFLUENCE OF NATURAL RADIOACTIVITY(BACKGROUND COUNT)Radioacti¥'e elements are found naturally in air, waterand soil. There is nowhere on Earth that we cannot findnatural radioactivity. The amount of radioactivity level(background count) in soil varies greatly depending onthe soil type, mineral makeup, density of materials andits *'eoiogical history (Eisenbud, 1987). To evaluate thevariation of the background count in soil, Iaboratoryexperirnents lvere carried out using the calibration130/0 Silts. The calibration chambervas filled ¥vith slurryand the background count ¥vas measured using a dummycone, in ¥vhich only the detector is placed at the centre ofthe calibration chamber to rneasure the BG count. TheBG counts f'or clay slurries vith ¥vater content rangingfrom 1250/0 to 2,_50/0 'ere measured and the results areshovvn in Fig. 10. This figure sho vs that the BG countvalue decreases vith increasing hvater content of kaolinclay.Next, the BG counts from field tests ar'e examined.chamber. One of the controlling factors is the size of theFigure ll shows the variations in the BG count ¥ 'ith ¥vetdensity for ciayey and sandy soils. These BG counts datalaborat.ory calibration chamber. Based on the theory ofwere obtained from Nobuyama (2000), for different soilgamma scattering and neutron methods (Homilius andLorch, 1958; Olgaard, 196)) the "measurmg volume"types namely, Kinkai Bay clay, Hachirogata clay,Holmen sand, Higashi Ohgishima sand and Vancouversand. The data from Pulau Tekong and Punggol Timoraround a source ¥vas found to be about 30 cm in radius.Based on experimental results, Karthikeyan (2005)deduced that the maximum radius of the infiuence zonefor the ND-CP used in the present study is about 23 .6 cm,are obtained as part of the present research 1¥'ork. FromFig. 11(a), it can be seen that for clayey soils, the BGcount varies depending upon the physical properties andas shown in Fig. 9, and it was found that the radius ofinfluence zone decreases with increasing vet density ofits depositional history of the sediment. The BG countthe material.cps (counts per second). The intensity of' natural gammaf'or naturally deposited clayey soils varies from 30 to 7-50 ljKARTHIKEYAN ET ALll4(a);300TS5 5 jjO Kink i Bay (Japan)Hachirogata (Jap n)c/) 250OP AA Pvl uTekong (Singapore)A:o50AOo* 100toj;J!/* *(:f/108eA Single Probe Nuclear-Density Cone Penetrometer isWet Density (kNlm3)developed by modifying the double probe ¥vhere the(b)300gamma-ray section is extended so as to insert an additional detector' that is outside of t,he gamma-ray zone emittingo Ho:men sand(Norway)e Higashi Ohgishima sand (Japan)Pu!au Tekong (Singapore)(/) 250aOfrom the source. With this, the cone is able to measureboth the background and actual RI count during theA Vancouver Sand(C nada)c 200same probing, thus removing the need to do t¥vo prob-Punggol Tirnor(Sing pore)ings, a real challenge ¥vhen carryin..*,a out such characteri-150zation under sub-marine condition.+ +r ),::erig. 12. Diagram of Single Probe F i*uclear-Densit) Cone Penetrometer(AU the dimensions are in mi]limeters)IMPROVEMF,NTS IN _NUCLF,AR-DF,NSITY CONF,PF,NETROMF,TF,R:"*O=}e'eetcr*2' A5OO 50o..i fTJLSSJ;DEteet'ef'i /AA)o )^#) JCAL f(c:j" * iGa 1rtl153s $v : 200OO'+*+' 'AtaQ___"__'/T.__ )_>.:i!'o"S,_A {i'i'l"'-. -:"__.-....=..J'i"____Description of Sing!e P/'obe ND-CPc:' EnCn 'vFigure 12 sho¥ 's major components of the Single Probeo14Fi('.} sf ;155 17 18 19 2120Wet Density (kNlm3)Nuclear-Density Cone Penetrometer (ND-CP). The lo¥verpart of the ne¥v cone is similar to the old ND-CP ¥vhere ithouses various sensors to measure the usual conell. Typical variation in the BG count with vet densit) forparameters, namely, cone resistance (q*), pore pressuredifferent soils from the field studies: (a) claye)' soils and (b) sand)(u2), and the sleeve friction (f)･ The upper part of thecone section is extended so as to insert an additionalsoilsdetector to measure the naturally occurring gammaray (BG) mainly depends on the concentration ofphotons. This upper part houses the radioisotope source,radioactive minerals present in soil, such as potassium(K). As the content of the radioisotope minerals variesdependin*' upon the soil types, hence the value of BGand t¥vo detectors. Detector-1 is used to measure thecount is also different for each clayey. soils. Figure 11(a)_',_amma photons.also sho¥vs a rou zh correlation bet¥veen the backg:roundcount and ¥vet density, ¥vhich could be a useful preliminary profilln_ indicator. However, for the sandy soils, theSepa/'ation Dista/7ce betTveen Detector-1 alld 2BG count values vary ¥vithin a relatively narro¥v bandfrom 40 to 120 cps, as can be seen in Fig. 1 1(b). The BGcount for sandy soils also does not vary much with its ¥vetdensity.Clearly, the intensity of natural radioactivity (back-ground count; BG) depends on ¥vet density of soil, thusthe background count profiles are also useful to classifythe soil type ¥vhen other more conclusive information isnot available. As a general trend at the same densities, thebackground count profile is ¥ 'eak in sand as comparedwith clay and thus it can be used as a rough guide toidentify the boundary bet¥veen clay and sand strata.These results also confirm the necessity of taking intoaccount the backg round count for accurate determination of ¥vet density in characterization of a hi_ :hly heter-o*'eneous lumpy fill. To¥vards this purpose, the existin_"*,double probe ND-CP needs to be impro¥'ed to measureboth the RI count and BG count ¥vith one probin*'.actual nuclear density (RI) count and Detector-2 is usedto obtain the background count of naturally occurringIn this ne¥v de¥'elopment, the important issue is toensure that the separation distance bet¥veen the twodetectors (Detector-1 and -2) is sufficient, so that theadditional detector (Detector-'_) is able to measure thebackground count accurately ¥vithout being influenced bythe gamma-ray source that is placed in the cone. Therefore, experimental in¥'estigations were carried out todetermine the minimum separation distance neededbet¥veen the t vo detectors. T¥vo different sets of laborato-ry experiments ¥vere conducted using a stainless steelcaiibration champer of diameter 600 mm and hei**ht 2000mm. In the first set of experiments, the calibrationchamber ¥vas filled ¥vith water and the upper part of thecone ¥vith the radioisotope source and detector units ¥verekept inside at the centre of the calibration chamber. Inthe second set, experiments were conducted ¥vithout theradioisotope source unit but only the detector ¥vas keptinside at the centre of the chamber. In both experiments,the detector' is moved up vertically inside the cone shaftlvith the help of a pull-up motor and at the same tlme, thegamma counts detected were recorded continuously.Fig:ure 13 sho¥vs the results obtained for the measuredJ i¥TUCLEAR-DEl¥*SITYCONE PENETRO ,1ETER20035R p 7 5477 4 9967 p t + o 9 1 Oe p t2180O((s 140o'(N=446.vYlcr' ' "' 'f"r;･ O 8)!rx^'2c:120::oOG){3d 25160o115i5>loo'+'_(" ;oe,z; 80,oO6005,eJapan Seils-Deuble ProbeSingapore Cl y-Deuble Probeaboratory Calibration T*or Singie Probeo40e1.246822Wet Density, p t (tlm3)20O(3amma-ray200 Count300400Rate (cps)OOFlg. 14. Improved catibration chart obtained for Sin"le Prober l'uclear-Densit) Cone PenetrometerFig. 13. Reiationship between the gnnlma-ra) coilnt rate lersusdistance for ,vo 8borator) experimeutsEffecti¥'e gamma count = RI Count - 1 .0353*BG Count(1)gamma counts versus distance in the t¥vo different sets ofexperiments. This figure sho¥vs that there are significantdifferences in rneasured gamma counts for a depth ofCalibration of the Sing!e P/'obe Nuc!ear-Density Coileabout 600 mrn, clearly suggesting that the minirnurn sepa-Penetrol 1 1 eterration distance required between the tlvo detectors isabout 600 mm. Subsequently, this calibrated separationCone Penetrometer needs to be calibrated before it can bedistance is used for the design of a single probe Nuclear-Density Cone Penetrometer. Another issue that needs tobe investigated is the applicability of field calibrationThe ne¥vly developed Single Probe Nuclear-Densityused to obtain an accurate relation bet¥veen the lvetdensity to the count rate ratio. For this purpose, theNuclear-Density Cone Penetr'orneter' which is discussed incalibration chamber vas filled ¥vith ¥'ater and the ND-CPwas placed at the centre of the charnber' to measure bothRI Count and B(3* Count. Similar'ly another configurationa later section.was made ¥vith Sodium Silicate chemicals ¥vith a ¥vetchart obtained for the Double Probe to a Sing:le Probedensity of 14 kN/m3 instead of ¥vater. The ¥vet densitiesDeptll Col'rectionsBecause of the fact that diftbrent sensors and detectorsare placed at different locations along the probe, there is aof' these liquids are kno¥vn and the calibration chartsrelating the density to the count rate ratio were thenobtained. These t¥vo data are incorporated into the fieldneed to adjust the depths so as to be able to produce theparameters at the same depth. For' the Single Probe NDCP, the measurement center for the cone is considered atcalibration chart obtained for Double Probe Nuclear-the cone resistance sensor just like in the original ND-CPand then the other sensors readings are adjusted accordingly. The depth corrections for pore pressure (0.04 m),sleeve friction (O. 1 1 m) and RI Count (0.60 m) remain theratio and the ¥vet density regardless of ¥vhether the NDCP is single or double probing. Finally, the applicabilityof the calibration charts in Fig. 14 against field data isdiscussed next.Density Cone Penetrometer, as shown in Fi*･. 14. There isa unique and consistent trend bet¥1'een the count ratesame as in the original ND-CP while the BG Count dataneeds to be shifted up by 1.20 m.Detector Efficiency RatioAs described earlier, in the single probe ND-CP, twodetectors were housed in the same probe to measure boththe actual nuclear density (RI) count and the background(BG) count of naturally occur'ring garnrna photons simultaneously, ¥vhereas, in the double probe ND-C*P, the RICOMPARISON OF SINGLE AND DOUBLE PROBEND-CPTThe development of' the single probe is to overcome theneed for t¥vo probing in the same hole in a marine basedinvestigation. As a br'and new tool, its performance needsto be compar'ed against the double probe device ¥vhichhas been extensively calibrated and used to dat.e. Thecount and BG count are measured by the same detectorbut in tlvo separate probings. The counting efficiencycomparison of the double and single probe ND-CP ¥vas(numbers of counts r'ecorded per unit time) of these t¥vodetectors in the Single Probe ND-CP are not similar andremoves any ambiguity about the position and it iscarried out when land is formed above the sea level. Thisit ¥vas found that the ratio between Detector-1 andpossible to ensure that the t¥vo probings conducted atdifferent timings are pushed through exactly the sameDetector-2 is I .0353. This dift'erence in detector efficiencyhole. Out of a total of 120 tests in Stage '_, 10 testsmust be accounted for while calculating the effectivegamma count f'or the Single Probe ND-CP. The ef ectivegamma count is calculated as belo v:used for this purpose. The focations are 19C, 28C, 33C,36C, 40C, 6) C, 71C, 91C, 109C and 121C in Fig. 5. 10verenumbers of double probe ND-CPTs ¥vere conducted Fu 12-Single Probe121-DoubleProbeT1KARTHIKEYAN ET AL_l 16Wet De sity (kN/me)O12 14 16 18 20 22o24W*t Density (kN/**)W*t D*nsity (kN/m')12 14 16 18 20 2212 14 16 18 20 2212 14 16 18 20 22O24Sand F' I.E_ 10Lumpy Fill12E_ 10E_ Io'S* 12Fig. 15.Lumpy Fill141416161618181820Lumpy FiilSeabed2020SeabedSeabed(07 O1.2004)- RI 91-Doub e Probe2.2003)" 12* i2Lumpy Fi:I- RI 9 -Single Probe( 2Sand Fi lSand Fi l6E_ Io222004)488(1 5.014816222814Seabed261420Sand F'Io68'Wet Density (kNlm3)(09 02.2003)2222- RJ 71-Singie ProbeFu 28-Single Probe(09.01.2004)(09 OI 2004)(G9. 1 2.2003)(1 O.1 2.2003)Fil 28-Double ProbeComparison of wet density profiles measured b, the Double Probe ND-CPT Ivith tl]e Single Probefrom 4th December to 12th December 2003. Unfortunately, the single probe ND-CPT could not be performed immediately after completing the double probetests due to some practical problems encountered. Thethe spikes bet¥veen the single probe and double probe forthe highly hetero*'eneous lumpy fill in bet¥veen the sandand seabed. The small variation in lvet density spikes maybe attr'ibuted to the average measurement of ND-CPTproblems arose mainly because the incr'ease in the length¥vithin the measuring ¥'olume. In a ND-CPT, theof the single probe ND-CP to accommodate the additional detector led to bending: Ivhen the cone encountered adense sandy layer above the ground-¥vater table. It tookabout a month to modify the cone str'ucture. To avoidpotential damages to the nelvly modified equipment, ameasuring sphere of the radioactive source is about 23.6cm in radius, and thus the density measured refiects theaverage around the central polnt of the radioactive sourcehole ¥vas pre-drilled about 6 m from the ground level forthe remaining: ND-CPT Iocations in Stag:e 2. The loss ofinformation for the first 6 m of the sandy layer is notcritical to this study as the aim is to profile the hi_g:hlyhetero*'eneous lump"¥' fill belo v. The single probe NDCPTS usin*" the ne¥v cone lvere conducted in the same holeprofiles measured by ND-CPT to reduce statistical fluctu-from 5th .Januar'y '-004 to 15th January '-004. As this ¥vasdouble probin_ : and the uncertalnties that are involved inensurin*" that both probin*'s are along the same location,a real challen :e in a sub-marine environment. The use ofcarried out one month after the double probe tests,durlng this tnne some additronal settlement ¥vasobserved in the ne¥vly reclaimed land. As the settlement¥vas measured, these readings ¥vere used for adjusting thedepth of the measured ¥vet density profiles accordingly.The ¥vet density profiles obtained from the doubleprobe ND-CPT are compared ¥vith the sin*'1e probe NDCPT, using the same calibration chart and the resultssho¥v ¥'ery good agreement, as sho¥vn in Fig. 15. Theand detector confi_g:uration. In addition, it is also necessa-ry to carry out averaging or filtering of wet densityations. In spite of these small differences, it is clear thatthe single probe ND-CPT has performed very ¥vell inmeasurin_g the ¥vet density profiles.One of the main advantages of this ne¥vly de¥'elopedSingle Probe ND-CP is that it eliminates the need fora single probe device in a sub-marine investigation is asignificant improvement to the design of ND-CP.CONC_LUSIO l+SNuclear-Density Cone Penetrometer ¥vas extensivelyused to evaluate the early state of the lumpy fill formed byseparation distance bet¥veen the t¥vo detectors isthe dredged clay lumps. In this paper, problems faced¥vhile performing ND-CPTs in sub-marine investigation¥vere hi_ hlighted. Experiments conducted in soils tosuf icient, so that Detector-2 is able to measure theinvestigate the influence of natural radioactivity (back-background accurately. As a further result, there is a veryood agreement in the measur'ed lvet density profiles forboth the sand fill at the top and the soft clayey seabed atthe bottom. Ho¥vever, there are some small differences inground count) sho¥ved that the natural radioactivityresults from only four out of the 10 ND-C_PTS are sho¥vnin Fig:. 15 for illustration. This result also means that the(background count) of soils greatly depends on the vetdensity of soil. Thus the background count profiles arealso useful to provide a rough classification of the soil rNUCLEAR-DENSiTY CONE PENETRO iE'TERtype ¥vhen other more conclusive inforrnation is notavailable. As a general trend at the same densities, thebackgr'ound count profile is ¥veak in sand as compared¥vith clay and thus it can be used as a rough guide toidentif'y the boundary bet¥veen clay and sand strata.These findings clearly demonstrate the importance of thebackground count in the characterization of a highlyheter'ogeneous lumpy fill for accurate determination oflvet density of soils.An important contribution in this paper' is thedevelopment of a ne¥v Sin*'1e Probe Nuclear'-DensityC*one Penetrometer. This new sin*'1e probe is developedby modifying the double probe ¥vhere the gamma-raysection is extended so as to insert an additional detectorthat is outside of the gamma-ray zone emitting from thesource. With this, the cone is able to measure both thebackground and actual RI count durin*' the sarneprobing. The comparison of the wet density profilesobtained from the double pr'obe and the single probeND-CPT is conducted ¥vhen land is formed above the sealevel. The measured results from the single probeND-CPT agree very well with that from the doubleprobe. This implies that the separation distance bet¥veenthe t¥vo detectors is sufficient, so that the additionaldetector is able to measure the background count accurately. This ne¥vly developed single probe ND-CPelirninates the need for double probing and the uncertainties that ar'e involved in ensuring that both probings arealong the same location, a real challenge in a sub-marineenvironment. Commercially, this is also important especially in sub-marine measur'ement ¥vhere each test is timeconsuming. This ¥vill mean significant cost saving.ACKNOWLEDGEMENTSThe authors ¥vould like to thank Housing and Develop-ment Board, Singapore, Surbana Internationai Consultants Pte Ltd, Singapore, TOAJDN (PUT) JointVenture, Singapore and Kiso-Jiban Consultants Co.,Ltd, Singapore, for their support during site investigationand laboratory testing. The authors have benefited great-ly from the many discussions on the details of ND-CPTwith Mr. M. Nobuyama of Soil & Rock Engineering Co.LTD., Japan. The authors are also grateful to theNationai Science and Technolo*"y Board (NSTB)(Presently kno¥vn as A* STAR) of Singapore for fundingthe present research ¥vork under grant NSTB/MCE/99/003 .11T2) British Standards Instilurion (1999): Coc!e o.f Practice for Sitelllvestigations (BS 5930), Brirish Standards Insritution (BS1).London3) Casagrande, A. (1949): Soil mechanics in he design and construcrion of Logan Airport, JBos!on Societ_1' of Cil'i! E,t*"ineers, 36 (2),l 76-2054) Dasari, G. R., Karthikeyan, l¥1 , Ta, T. S., i¥,iimura, iivl. andPhoon, K_ K. (2006): In-situ evaluation of radioiso ope conepenetrometers in clays, GeotechT s!. J_, ASTlvl, 29 (1), 4553.5) Eisenbud, ivl_ (1 9S7): E,,vironinent(d Rac!ioac!iv!f_v.' F,-om N(Itura!.Industri(7! and JTfi!ilar}' Sourc"es, 'Third EdiLion. Academic Press,475 .6) Hartleu, J and Ingers, C_ (1981): Land reclamation using finegrained dredged ma erial. Proc 10fh ICSI :fFE. Stockhol n, l,145-148.7) Homilius, i, and Lorch. S_ (1958): On the theory of gamma rayscattering in boreholes. Geophysica! Prospecting. VI, 342364.S) ISSivIFF (1989): Interna ional reference est procedure for conepenetration test (CPT), Report of the ISS_,VIFE T chnica! Colnini!!ee on Penerra!ion Testing of Soi!s- TC 16, Is'ith References ro TestProcedures. S¥vedish Geotechnical Institule, Linkoping, Information, 7, 6-16.9) Kanhikeyan, lvl. (2005): Applicarion of radioisotope conepenetrometer to characterize a lumpy fill, Ph D Thesii, NarionalUniversity of' Singapore, Singapore. 219p,lO) Karthrkeyan, M., Dasari, G. R,,, 'Tan. T. S., Lam, P_ ¥!.. Loh. YH.,¥rei, Jand Mimura. N,1. (2001): C haracterization of areclaimed land si e in Sirrgapore, Proc. 3i･cl Int. Conf･ Sofi Soi!Engineering, Hong Kong, 587) 92.ll) Karthikeyan, l¥,1.. Dasari, G. R. and Tan 'T S. (2004): In-situcharacterization of land reclaimed using big clay lumps. Can.Geotech. J., 41 (2), 24,_256.12) ilvlimura, ivl. and Shrivastava, A. K. (1998): RI-Cone penetrometersexperience in naturall.v and artificiaHy deposited sand, Proc. Ist Int.Conf. Site Characterisation-ISC'98, Atlanta, 1, 575-580.13) .¥,Iimura,/1., Shrivasrava. A. K , Shibala, Tand Nobuyama. N'I(1995): Perf'ormance of RI cone penetrometers in sand deposits,Proc. Int,, S_vnlp. Cone Penetration Testin*" (CPr'95), 2, 55-60.14) ivlimura, M., Shrivastava, A. K., Shrba a, 'T. and Nobuyama, N'I.(1999): In-situ measurement of vet density and natural ¥valercontent vith RI-Cone penetrometers, Proc. 5th Int. S_1'nlp Fie!c!1' leasurenlents irl Geo,nechanics, Singapore, 559564.15) Nobuyama, lvl. (2000): The result of the RI cone penetration tests,NUS Inrerna! Report No 6004998/264, Soil and Rock Engineerin_"..C o., Japan16) Olgaard, P. L. (1965): On the theory of the neutronic method formeasuring the lvater con ent in soil. Danish Atomic Energ_1'C'oinmission Research Estab!isllrnent. Denmark, Riso Report No97 .17) Shibata, T., iMimura, ivl., Shrivastava, A. K. and Nobuyama, ivl.(1992): ¥. toisture nleasurement by neutron moisture cone penetrometer: desi**n and application, Soils anc! Foundatiolls, 32 (4), 58-67.18) Shibata, 'T., h,iimura, iM. and Shrivas ava, A. K. (1993): RI ConePenetrometer experience in marine clays in Japan, Proc 4!hCanadian Conference on A;farine Geotechnica! Engineering, 3,1 024 I 033 _19) Shibata, T , lvlimura,,1. and Shrivastava. A. K(1994): Use of RIconc penetrometer data in f'oundation engineering, P,'oc. 13thICSMFE, Ne¥v Delhi, 1, 147150.REFERENCES20) Shrivastava, A K. and h,Iimura, i¥,1. (i998): Radioisotope conepene rometers and the assessment of foundation improvement,l) Bo, M. ¥¥r., Ba¥vajee, R. and Choa, V. ('_OO1): Reclamation usingdredged materials, Proc. Int. Coilf. Port and Maritiine R & D andProc. Ist Int. Conf. Site Characterization-ISC'98, Atlauta, 1,T chno!ogy, The ivlaririme and Port Authority of Sin_ apore,21) ¥¥r}ritman, R. ¥r_ (1970): H_vdraulic fills to support structural loads,455-46 1 .60 1 606J. Soi! IV[ech. Fbunc!. Div., ASCE, 96 (SM l), '_3-47. | ||||
| ログイン | |||||
| タイトル | Effect of Specimen Size on Unconfined Compressive Strength Properties of Natural Deposits | ||||
| 著者 | Takaharu Shogaki | ||||
| 出版 | soils and Foundations | ||||
| ページ | 119〜129 | 発行 | 2007/02/15 | 文書ID | 20985 |
| 内容 | 表示 SOILS AND FOUNDATIONSVol_47 ,No.It19- 129,F eb2007Japanese Geotechnical Socie yEFFECT OF SPECIMEN SIZE ON UNCONFINED COMPRESSIVE STRENGTHPROPERTIES OF NATURAL DEPOSITSTAKAHARU SHOGAKli)ABSTRACTIn order to use the ad¥'anta*'es of unconfined compression tests, a ne¥v testing procedure using S (or Small size)specimens (15 mm in diameter and 35 mm in height) is proposed and a ne v por'table unconfined compression tesapparatus ¥vith suction measurement is outlined. The efi ct of specimen size on unconfined compressive strengthproperties of natural deposits is discussed fr'om laboratory tests. The standard deviations of the ratios of q and E50values of' the S specimens to O (or Ordinary size) specimens (35 mm c! and 80 mm h) ¥vere in the range of 0.09 to O. 16.The 100/0 variation from the mean value refiects the hornogeneity of soils since the coefficient of variations of theundrained shear strength for the undisturbed and reconstituted soils were 80/0 to 170/0 (Matsuo and Shogaki, 1988). Inan en_ :ineer'ing sense, there ¥vas no difference in shear str'en*'th and deformation characteristics bet¥veen the S and Ospecimens for soils having plasticity indexes ranging from 10 to 370 and unconfined compressive strengths of 18 kPa to1000 kPa, that vere taken from 26 dif erent sites in the United Kin*'dom, Korea and Japan. These soils consisted ofHolocene and Pleistocene clays plus diatomaceous mudstone and highly organic soils.Kev words: clay, organic soil, specimen size, strength properties, suction, unconfined compression test (IGC: C6/D5)automatically ¥'ia electronic instruments.IN1'RODUCTIONA srnall diameter (45-mm) and a cone sampler vith at vo-chambered hydr'aulic piston have been developedThe unconfined compressive strength (q ) is ¥videlyused in Japan for stability analysis of clay foundationsunder undrained conditions. This is mainly because themean ¥'alue of q. /2 clearly describes the undrained shearand their applicability for natural Holocene andstrength on the failure surface in a specific area (Nakase,Shogaki et al., '_004a, 2004b, 2006. The effect of specimensize on the unconfined compressive strength properties isnecessary f'or the examination of strength properties of aPleistocene clays, or'ganic and sand deposits were sho¥vnby Shogaki, 1997a; Shogaki and Sakamoto, 2004;1967; Matsuo and Asaoka, 1976; Shogaki et al., 1997),and in addition to this, the testing pr'ocedure for theq -value is simple and economical. The specimen sizeusually used in Japan for unconfined compression tests(UCT) is the O (or Ordinary size) specimen, 35 mm indiarneter and 80 mm in height.The thin-walled t.ube sampler normally used in Japansample obtained from the 45-mm and cone samplers.In this paper', an outline of the portable unconfinedcompression apparatus (PUCA) for rneasuring the suction and q is shown and the eflbct of specimen size onunconfined compressive strength properties of naturalfor obtaining undisturbed soil samples is the 75-mm (JGSclay, organic and diatomaceous mudstone deposits is1221-2003) and double tube (JGS 1222-2003) samplersdiscussed based on laboratory tests.having an inner diameter of 75mm and a length of1 meter. The reasons for using O specimens in Japan arethat two specimens can be taken from a sarnple 75 mm indiameter and 100 rnm in height and the stress calculationREVIEW OF STUDIES FOR THE EFFECT OFSPECIMEN SIZE ON UNDRAINED STRENGTHPROPERTIESis easy because the cross sectional area of the specimen isabout 10 cm2. However, for O specimens, the number' ofIn the studies for the effect of specimen size on unconfined compressive stren*'th properties, Yoshinaka (1976)and Lo (1970) mentioned that the stren*'th properties ar'einfluenced by the specimen size for rock materials andspecimens is limited and their preparation for testing isdifficult due to latent cracks or homogeneity. In addition,undisturbed sampling for hard soils like Pleistocene isdifficult. Therefore, the small size specimen is better foreffective use of samples because its size facilitates stresscalculations and it is not necessary to retain the samplefissured clays respectively. Kamei and Tokida (1991)per'formed the UCT with specimen sizes of 10 mm, 20mm, 35 mm and 50 mm in diameter and 10- 100 mm insince calculations and measurements can be doneheight for reconstituted clays having plasticity indexesi] Associate Prof'essor, Narional Def nse Academy, Japan (shogakie,nda.ac,jp).The manuscrip for this paper vas received for revielv on August '-4, 2005; approved on Oc ober 2, -,006.Wrhten discussians on this paper should be submitted before September l, 2007 o lhe Japanese Geotechnicai Society 4-38-2, Sengoku,Bunkyo-ku, Tokyo 1 12-0011, Japan. Upon request the closing date may be extended one mor th.ll9 120SHOCJAKlfrom 19 to 36. They showed that there is no effect of¥specimen size on strength and deformatlon characteristicsif the ratio of specimen height to diameter' is 2.0 fordiameters greater than 20 mm. Ho¥vever the q* and secantmodulus (E50) values increase gr'eatly if the diameter is 10isplacementtransducerLoad cellmm under hlc!=2. They made the specimens by usingsmall size sampling tubes of 10mm and 20 mm in di-Perspexeylinderameter and then by a trimmer only for 35 mm and 50 mmSpecimendiameter specimens. Shogaki and Maruyama (1995)[d ISWTI Jpointed out from the test results of reconstituteddisk platePressuretransducerMatsui et al. (1994) developed a triaxial apparatususing a small size specimen, 22.5 mm in diameter and45 mm in height and discussed its applicability forS eed POtYerasxpcontrOller oundisturbed cla}.' in Osaka city. They sho¥ved fr'om theorganic and diatomaceous mudstone deposits.The S (or Smail siz,e) specimen (15 mm in diameter and35mm in height) can be used for measurin*' theundrained strength anisotropy ¥vith a different an*"le ofinclination to the vertical (Sho*'aki et al., 1997) and also200mmL,ength250mmMass70kNSpecimend l5-3Srnms zeh=3S-80rnrnLoadingspeedclay deposits that specimen size has no effect on the shearstrength. Fr'om these tests, they found that drainage timeeffect of specimen size on strength properties for the ¥viderange of strength and plasticity in various soils, includingHeightoad cel]Load'r powertriaxial compression test on Holocene and Pleistocenebecomes shorter during the consolidation process.The effect of friction bet¥veen specimen and pedestalcap on stren*"th properties diff rs by specimen size (e.g..IGS 0530-2000). Many researchers repor'ted that there isno effect of specimen size on strength properties underh/d 5 2. Ho¥vever, there are no systematic studies for theh 3smnCeramiclKa¥vasakl clay that the q and E50 values increase as thediameter decreases is caused by the problems in specimentaking, concerning Kamei and Tokida's test (1991).500-5000ki¥O 15-2 OOmm/minValead slvitcsl itchC_urrentDirector AiternatingFig. 1.La _'out of the portab e unconfined compression apparatushard soil ¥vith latent hair cracks (Shogaki, 1997b). Thevalue of q* ¥vas deter'mined to be the maximum stresscorresponding to axial str'ain of 150/0 or iess. The Eso isgiven by Eq. (1), in which 850 is the strain at the value ofq*, /2 .E50(q.l-') ( I )8<0Ko-consolidated triaxial compression (CKoUC) andextension (CA'OUE) tests (Shogaki and Nochikawa, 2004)for samples taken from the 75-mm sampler. Using the45-mm and cone samplers having an inner tube diameterof 45 mm produces a smaller specimen, which is moreadvantageous for measuring mechanical and statisticalproperties. Therefore, the strength and deformationproperties of the O and S specimens are discussed fromthe effect of specimen size in this study.PORTABl.F, IJNCONFINF.D COMPRF,SSIONAPPARATI JSThe PIJCA and its specifications for measurin_thesuction and the q values are sho¥vn in Fi_9:. 1. In thisapparatus, the load is applied by the linear head and isSOIL SAMPLES AND TEST PROCF.DURF SThe undisturbed soil samples used in this study aresho¥ 'n in Fig. 2. The 75-mm rotary double-tube sampleridentified as 75R, in accordance ¥vith the JapaneseGeotechnical Standard (JCJS 1222-2003), ¥vas usedinstead of the 75-mm sampler normally used in Japan inthe Pleistocene clay deposits of Nagoya, Izumi, Osakaand I¥vai soft clays and or*'anic soil. The 84T sampler(JGS-1223, 2003) vas used for I¥vai Pleistocene clay.The method of core samplin*' (Core) used for thediatomaceous mudstone of Nanao ¥vas double tube coresampling using water pressure for drilling to minimizesample disturbance.The lvater content (}v ), Iiquid limit (1vL), Plastic limittransmitted through an AC/DC motor. This equipment(1vp), Ip, clay composition of less than 5/Im (CC),has a hei**ht of about 20 cm and a mass of about 7 k**.effecti¥'e overburden pressure (cr(*), overconsolidatedratio (O_ CR) (defined as the ratio of preconsolidationTherefore, since the equipment is portable, it is practicalfor field use. The UC_T ¥vas performed on specimens15 -35 mm in diameter and 35 -80 mm in heig:ht at astrain rate of lo/o/min, after specimen suction ¥vasmeasured using a ceramic disk plate. The air entry valueof a ceramic disc is about ?_OO kPa. The PUCA isequipped ¥¥'ith a Perspex cylinder to measure the suctionover one atmospheric pressure and also the q** value forpressure ((7 ) to ((T(.)) and qto*"ether with samplers usedin this study are summarized in Table 1. The lp and q*values range from 10 to 370 and 18 kPa to 1000 kParespectively, ¥vhich are very wide ranges. The Holoceneclays are classified as from normally consolidated toslightly overconsolidated clays since the OCR values arein the range of 1.0 to 3.09, except for Busan Ne¥v Port 12！SPECIN｛EN SIZ薮EF罫ECT 魯・ 〆75mm蜘←s＾鐸禦灘 100㎜・難舗s・ 瓢 35㎜ 玉5㎜A sample ob｛aiぬed罫rom75−mmε匙nd75R samplers（a） 小45mm Ψ無45mm5m⇒丁s 、鼠． 点Ariake 陶o45皿m90mm ↓議s鞍F董9。2。 S巨mpEi臓g siIes45錨 Ψclay，whlch has OCR values rallging from O。79to2。20．sBusan New Port clays were disturbed under soil sampling（b） A sanlple obtained frQm45−mm samplers（Shogaki et aL，2005a）．T｝1e OCR values of Pleistoceneclayラhighly orgaRic soil and diatomaceous mudstoneFig，3。 Location of specimens for a samp亘eraugefromLO玉to78．1andclassinedasfromnormallyconsolidated to heavily overconso1呈（iate（l clays． becomes constan芒，can be measured qulckly when芒he piezometer me＆surement iadicates a similar value to Figure3shows the location of specimens，for sanユPles75mm in diameter and100mm iH height and45mm indiameter and180mm in height，from the samplillgξubeof重he75−mm an（175R samp茎ers and45−mm sampler、Six 重he expecξed specimen suctio【1．2）asshownlnFig．3．Shogakie亡al．（i995α）shows重hatthe However，the possibi至ity exis重s重hat suction greater than that of the p圭ezometer measurement cannot beS specimens and one O specimen can be obtalned fromthe samples of亡he75−mm and75R samplers alld eight Sspecimens and one O specimen from重he45−mm sampler， accurately me＆suIled if all air ls not removed from由e pressure transducer pipe．3） If the alr iIUhe pressul』e transducer pipe is removedstrength and deformation properties of ten S specimens and the piezome重er seusitivity is hlgh，the measuredobtained from a sample75mm in diameter and45mm in So va茎ues are unrelated whell the spec三men is put onheight＆re similar in an engineering sense．The specimen the ceramic disc plate to get piezometer measure．site，as shown in Fig。3，is not hlnuenced by the samp正edistul−bance caused by tube penetration an〔i fr玉ctionbetweell soil and tube during sample extruslon。This wascon倉rmed by using a Scannlng Electron Microscope（Shogaki and Matsuo，1985）and a color laser three（iimensioual pro負le microscope（Shogakl，2006a）．Eachspecimen was she＆red at1％／min after suctioll measure− ments．4） However，the time in which suction becomes constant is less when the suction drops from a王arger value to specimen suction．The maximum time for measuring suction w＆s six For the e貸ec重of measuring suc重ion before＆ndminutes．after shear on strength and deforma重ion propertles o郵ment uslng PUCA ln accordance with the Japa！1esespecimens，lt was con貸rmed by Shogaki et aL（1995b）Industrial Standar〔l for unconfined compression tests oεt紅at there∼vas no efモect for natur＆1deposits．Namely，thesoils（皿SA12164993）． The procedure for measuring由e suction is simiiar todecreasesinwatel’contentofspecimensduringsuctionthat reported in other Iiterature（Shogaki etε迄L，1995blconsidered tha重t難is smal至cbange il1∼vater content doesShogaki and Maruyama，1998）．It is important that themeasurement and shear were less than I％．It wasnot affect the strengthεmd deformation properties．suction be measured quickly重o mlnimize stress cQnditio亘changes，whichdirectlya登ecttheundrainedshearstrength＆nd secan嘘modulus values。The specimen suc−EFFECT OF SPECIMEN SIZE ON SUCTION，based on亡he author’s expe11iα1ce，as foliows：RELATIONSHIP BETWEEN STRESS AND STRAINAND EFFECTIVE STRESS PATHS1） The suction（So）of＆specimen，in which the suction Figures 4（a），（b），（c），（d），（e），（f） and （9） show thetlon was measured using a larger piezometer point value， JSHOGAKIi22Table 1.Geotechnicaproperties of soil samp]es used in this studl_C_ (kPa)* a( (kPa)q(o/o)lp C_OC_RSamplerIt'n It'L Tt*pNo. Site(O/o) (O/o) (o/o)(Holocene)1 Shizunai5062291 36209S93 Urayasu81 - 85i04 - 1 144 Kalvata4836) 65 Tokyo4649327_ Hachiro :a a6 Kalvasakil05 - 108l 13 - 120444933 41 29_)l 50 6 1 36l .20l 07l .2360 - 65 50 - 5)_ 232 - 45710 15 77l 7 _, I , 245, 51, 23 - I .19 12/l952. I O-7759l08 - 320464864 - 73 47 - 54 160 - 223l OO - l.08 66 - 189333638-41 16-26195-211l .06 - ?_ 02 100 - 1977 = Yokohama57-61738 Hekinan60 - 9374 - 10731 -3845-7225-43 6-124O 99 - I .37_ 60 - 14534 - 7151 - 952538'-6-57 i 3-30 99-7_051 , 1 7 - 2.94 92 - 2204759 - 10526 - 4133 - 69 30 - 54 191 - 241l .O_7 - I .36 130 - 138 75-mm96 - 107293459-71 3'_-42 = 51-92l.OI - l 12 23 - 778,_ - 150294819-lO)_ 36-42 =l.05 - 3.09 : 15 -27390 - 1 154447469 Ku¥vanaIO Amagasakil I Ashiya6812 j Tokuyama8968 - 1301 3 AFiakel 2014 Kahoku a a16 Kimhae (Kr)4613850883460803050441 026653 - 70I 8 Yangsan (Kr)l 9 I ,f ai64 395798 - 10939(Kr)68 5581 7415 Bothkennar (UK)17 Busan Ne v Por7)7464358592577560 - 86l .26135l .9612131 35)_6 - 40 30 - 35 95 - 154l 02-1_51 = 91 -l072832 - 54 36 - 60 59 - 175O 79 - 2.20 48 - 1296167 - I 18l .03 - I 13 26-323,34) 733446586l 03S434-74 = 34-63 18-23l .OI - 2.04 16 - 20(Pleis ocene clav)20Nagoya34 - 73 63 - 78 -75 - 4033 - 47 8 - 26 1 95 - ,_412.44 - 4^2521lzumi28 - 60 49 - 96 2_, - 2827-6S 5-28 = 8-1364^5 - 78. 1 347 - 578, 2Osaka (Bay area)23Osaka (h,Ial2: Inland area)63 -73 75 - I 18 31 -444424Ilvai74-83 = 101-lll 41-5158-7440 60274S3378 3966 32473034640-66 66-681 1658 - 76275R44 21.832.08 362-585 45-mm. Cone1 ,,OI - I ^90 25 - 3584T(Highl¥.' organic soil)25 I¥vai393-592 380-655 : 164 )8)l 99 - 37023 - 35 14 - 15 8.03 - 1 1 42 25 33 75-mm(Diatomaceous mudstone)26 * Nanao87 - 187 143915,1 3542 =22.32335 - 1070 C_ore*: C_lay composition of less than 5 l!mresults of the suction measurement for Bothkennar,Kimhae, Busan Ne¥v Port, Yangsan, Hachirogata, I¥vaiorganic and Holocene clays respectively. . These specimens¥vere put on the ceramic disc plate when the piezometerpoint indicated about 80 kPa, dependent on type of soiltested. The time, in ¥vhich the specimen suction becameconstant, varied slightly for each specimen and this timewas independent of specimen siz,e. The suction valuedecreased ¥vith sample disturbance (Shogaki, 1995). Theeffect of specimen trimming on suction is unrelated tospecimen size since the So Values of both specimen sizesare similar, as sho vn in Fig. 4. The suction values of 1¥vaiorganic and Holocene clays, as sho¥vn in Figs. 4(f) and(g) respectively, are as small as 3 -5 kPa since the (T(values are as small as 14 -23 kPa.Figures 5(a), (b), (c), (d), (e), (f) and (g) sho¥v therelationships between the pore water pressure measuredat the base of the specimen, the axial stress and the axialstrain (8*) for the same specimen, as shown in Fi**. 4. Thesuction under shear is represented as the pore ¥vaterpressure (u) in Fig. 5 since the suction under shearbecomes zero to plus for an O_ specimen and a small So¥'alue for the S specimens. Therefore, the u Values at thee*=00/0 are So values. The w , q , E50 and axial strain at 123SPECIN{EN SIZE EFFECTooIlc ]Bothkenuar20C,¥60'[4 1 . 8]CIiO[39 8]+ o specimen:;Cl)V)1 _ 3 4 6,40Hachirogata[ l: Suction (kPa)60O:;A S2 specimeno[lO.3 jiSi[ l:Suction (kPa) o S specirnen80[8.412037.9]¥40Oc ;o o specimeno SI specimen805Time, t (min)o(a) Bothkennar cla)'o1 Time,2 3t (min)456(e) Hachiroga a da)'[1)1 6] ¥ [30.0]c t 20c(o40ioc20c/c,o40S0=(3'4 5.4)kPa[31.5] [ l:Suction(kPa). 60+ o specimeno Slspecimeno:sKirnhae A S2 specimen(') 80o+0' Sl ' S4^ S, ' S5o 601 _ D 4 5 6' S(/) 80,Time, t (min).o(b) Kimhae cla}'･ S6lwai (Organic)1 _ 3 4,56Time, t (min)(f) Iwai organic soilBusan New Portc:;cloo:$C/o37^91l/50[47.7]100c:$CCO+05:O 60A S2 specimenoS0=(3'O-4.9)kPal 40[41 3]+ o spesimeno Slspecimen[ l: Suctron (kPa)20:o_,o Sl a S3A S2 ' S480C,D7lwai (Holocene clay)100Time, t (min)o(c) Busan New Port da)'- !).7I'ime, t (min)56(g) I vai (Holocene da)')lce 1/ [22.6]20Fig. 4.Relationships betlveen suction anti time' 4¥J40Cl)iO[24.2Yangsanfailure values of each specimen are also given in Fig. 5.The q60[ l: Suction (kPa),O 80:$Cl)100o+ o specimeno S specimen1 2 Time,3 4t (min)5 6 7(d) Yangsan d*yand E50 values and the relationships bet¥veenstress and axial strain for each soil are almost the same,unrelated to specimen size. However', pore water pressureunder shearing differs by specimen size, namely the porelvater pressure of O specimens changed from minus to8plus under an axial strain of from 0.50/0 to lo/o beforemaximum axial stress and the amount of change of porewater pressure was greater than that of S specimens. Asdescribed in the previous chapter, the strain rate of bothspecimens ¥vas lo/o/min. The pore water pressure valuesmeasured at the specimen bottom are smaller than thosearound the shear band and caused by the delayed SHOGAKI1_ 4100'Ce*1 OOb, ,bSlmbol.Cl50Cl): S ecimenkPa)olo):SCl)ooE *oq*T'* n*50t-( MP a)(o/o)Scl)Ol60l7 9 15 559I 0.0 12 g2733S.s927 2 13 534O20Q)h::51:5v)(,)c,)e,l^ c1'o(L)/c9 -4vonL1)v+e :Oaf)¥d'AAAA-20,,13 5-40)e)O-40hoBothkennaroCL2 4 6 8 10olOO80¥J60eb_ 60c:;k) 40S mbol. * i S ecimen40'D )'Cl)t$' no20*slS2O1)')cl)(,DF soq(qt)kPa)70656476 574 l76 2CMPa)e'(" )42 4135 3639 6Gf)20Svmbol. $*: S ec imeD$oe; 1020s15a(o/o)(c) Busan Ne v Port cla}'(a) Bothkennar cla)*lCe105Axial strain,Axial Strain, 6a (o/o)q*Es )Sre/elkPa)(Oloo65(MPa)54 o, 5s6653 o33530$$w alhsoorOc8uo)1cs vn,eh '{e) / lO4q)¥l* sec:lN -20Q,e)oKimhaeo -AnvCL-20-3 oOo510Yangsanc155lOAxial Strain, g a (o/o)15Axial strain, aa (o/o)(d) Yangsan da)'(b) Kimhae cla}'mi**ration of pore water pr'essure, as shown in Fig. 6. Thealmost similar for the O and S specimens. However, thereundrained condition under' shear for both specimen sizesis a large difference in the effecti¥'e stress paths bet¥veenwas sufficient since the decrease of ¥vater content ¥vas lessthe O and S specimens of Bothkennar, Kimhae, Yangsanthan lo/o by calculating specimen ¥veight before and aftershear for both sizes. For' I¥vai organic soil and soft claydeposits, the effective stress paths of UCT using S speci-and I¥vai Holocene clays ¥vhich is caused by the delayedmens are consistent ¥vith those of the CKoUC except thecontent are as high as 150-3700/0 and 136-59,_o/odifference in the initial stress condition (Shogaki, 2006b).respectively and the qTherefore, the UCT ¥vith suction measurement using Sspecimens is suitable for the measurement of effectiveHachirogata clay had many diatoms and the samplesmigration of ¥vater' content. In Hachlro*'ata clay and I¥vaiorganic soil, the plasticity index and natural ¥vatervalue is as small as '-5 -33 kPa.¥vere saturated by ¥vater (Tanaka and Locat, 1998) andstress paths under undrained conditions.The effecti¥'e stress paths concerning Fig. 5 are sho vnin Fig 7. From the relationships bet¥veen axial stress andI¥vai or_9:anic soil had a hi*･h ¥vater content of 3700/0. Theaxial strain, as sho¥vn in Fig. 5, the deviation stresses arecan be ignored.delayed migration of pore ¥vater pressure forHachirogata clay and l¥vai organic soil is so minor that it Ti25SPECll¥,lEiN SIZE EFFECT30c30c tC20{-b 20bcl O lOc o 10:S%: Svnlbolc')$$: S eaimenwnaeolo)OoSoq,133133q*kPa22 925 5Cl:E soMPa)3030Cf(0/5437oq)h:5 O:5 O(,/?')ODof_ cee)1c ce, ; -5*ce: , -5'*ceoe'o -lOe*o -lOHaehirogatao510e*15o5lOAxial Strain, 8a (o/o)Axial Strain, 6a (o/o)(e) Hachirogata cla)'( fi)Fig. 5.15I¥vai (Holocene cla}')RelationshiPs between u, a ancl 8*40c s30Loadbe 20c')lc'10larger u.1..OMigration of u""""'¥V""""'a'I:' 5E,)smaller uu)),^ce-}'-'4 OPressuretransduceree sCeramic disca)oe 5Fig. 6.o105Axial Strain, Ca (o/o)Concept on migration of pore water pressure under shear15against lp and q(f) 1lvai organic soilThe relationship between axial stress and axial strainfor Osaka and lwai Pleistocene clays is sho¥vn in Figs. 8(a) and (b). The UCT usin*" S specimens is applicablein Figs. 9 and 10 respectively. The ratios(REso) of E50 Values are also sho¥vn in Figs. 11 and 12.The plot symbols are classified for Bothkennar, Kimhae,Busan Ne¥v Port and Yan*'san clays in order to distinguish f'rom Osaka Mal2, I¥vai Holocene and Pleistoceneclays and or_ :anic soil and other Japanese Holocene andunder JIS A1212-1993, as well as the triaxial test using SPleistocene clays and diatomaceous mudstone. The Rq*specimens (Shogaki and Nochikawa, 2004) since therelationship between axial stress and axial strain isvalues ar'e in the range of 0.91 to 1.25, unrelated to thelp = 10 - 370 and q = 18 - 1000 kPa values, and the meanunrelated to soils, as sho¥vn in Figs. 5 and 8.value is I .02. The RE50 values are also in the range of 0.77to I .24 and the mean value is 0.99. The q** and E50 Valuesobtained from the O and S specimens are almost similar,unrelated to t¥venty-six different sites in the UnitedEFFECT OF SPECIMEN SIZE ON q. AND EsoVALUES. '_Km*'dom, Korea and Japan and also Holocene andvaluesPleistocene clays, organic soils and diatornaceousof S specimens to those of O specimens are plottedmudstone. Ho vever, the RE50 of I¥vai organic soils ¥ver'eThe ratios (Rq ) of the mean value (q.(s)) of q SHOGAKIl 26201 OOBothkennar80rHachirogatafScclc')60ce C40hceS:: :vO*'S'c') QlOje'C20O-(ce+ o specimen.o S specimenA S specimeno+ o specimeno s specimeno20 40 60 80 1 OOoEffective stress, q,,/2 - u (kPa)O lO(a) Bothkennar da)'C*20Kimhae50･ ') e40u)lwai (Organic)_101 30(5Ce¥20+0o Sl-c+ o specimenq)o sl specimenA S2 specimen10Oee.->a)ovA S2a s3i6020oeeS4s5s6O 5151020EffectiVe stress, 0/2 - u (kP a)Effective stress, d2 - u (kPa)(f) hvai organic soil(b) Kimhae cla)*8020+" 60os",AO specimenlwai (Holocene clay)Busan New PortSl specimenS2 specimencle'_ce-c')s - 40$::o 10-(::;c¥'ee- 20o30(e) Hachirogata clay60l20Effective stress, d2 - u (kPa)>e)o4060;+ OoAOoSl DS2 vS3s4' , -l (O )20Effective stress d2 u kPaEffective stress, d2 - u (kPa)(c.) Busan Ne v Port clay(_ ,*) hvai (Holocene cla)')40cFig. 7. The effective stress pathsYangsan_ 30s^ceu)s:'in the range of 0.67 to 0.91 and the mean value vas 0.76.This is caused by soil homogeneity, as shown in Fig. 5(f).Namely, the q and E50 values of the O, Sl and S6 speci-ono 4v-cce lS.Cq) 10o+ o specimeno s specimeno1 O 20 3 O 40 50 60Effective stress, d2 - u (kPa)(d) Yangsan claymens under similar w* values are similar. The UCT testfor hi**hly or*'anic soils is very difficult since theundrained condition under shear cannot always be confirmed. However, it ¥vas judged from the effective stressbehavior for the UCT and Ko consolidated-undrainedtriaxial compression tests (Shogaki et al., 2004b) that theUCT test for I¥vai organic soils could be accuratelyperf ormed.It ¥¥'as shown in Figs. 9 to 12 that the qand E50 Valuesobtained from O and S specimens are unrelated to sampling sites and various soils. Based on this fact, Figs. 13 TSPECllvIEN SIZE EFFECT127Osaka Mal 2600llcO1' eF ¥ql 400k),D$)200+ooA'S;'sls3oo12AS cimenquwn･$4+q8: S bo , *:fcnEsosfolekPaMPao/e6868542.643,2539.043.36966524.937 8534.038.2o1O2118;23223Axial Strain, 6a (olo)50806(a) Osaka Pleistocene (iMal2) clay50 200 600 1000(kPa)lOO150Unconfmed compressive strength, qF'io. 10.Relationships bet,veen Rqand qulwai (Pleistocene clay)400'c:S¥/ 30014b1" Smbo,,*+ooAslDvs3(1c' onne) 4vvC'l OO2 4oOS2s4**: S cilnenEsOq*wnookPaa23 7360 29385848984ef:: Io/o378 4312 4351 l22 9202519 62.19.6303 1 1.221.32.26 8102Ocl I .O.¥vlQl O,oAxial strain, 6a (olo)06(b) I¥vai Pieis ocene cla)'Fig. 8.Relationships betlveen er and e2300500Plasticity index, Ip (o/o)Fio, Il.Re!ationships betlveen RE_.-o and lpFigs. 9 to 12 are the mean ¥'alue for several specirnens.1 .4The mean values of the Rq and RE50 Values using thesespecimens ¥vere similar to those of Figs. 13 and 14. Themean vaiues of the Rq and RE50 are in the range of 0.99e< I ,2to I .03, unrelated to Holocene and Pleistocene clays. Thestandard deviations (s) of Rq* and RE50 are in the rangeof 0.09 to 0.16. The 100/0 ¥'ariation from the mean valueO_:20 40 60 go loo1,0.Cl)reflects the soil homogeneity since the coefficient of:variations of the undrained shear strength for theundistur'bed and reconstituted soils, excluding soilO,8o.6'_O 40 60 80 iOO 300 500Plasticity index, Ip (o/o)strength, stiffness and sampling methods, ¥vere 8- 17010(Matsuo and Shogaki, 1988). Therefore, the strength anddeformation properties of the O and S specimens aresimilar for undisturbed clay and organic soil deposits andFig. 9.Relationships betlveen Rqand Idiatomaceous mudstone ha¥'ing plasticity indexes from10 to 370 and the unconfined compressive strengths are1 8 - 1000 kPa. The undrained strength propertiesand 14 show the histograms and their norrnal distributioncurves for the Rq and RE50 for Holocene and Pleistoceneclays respecti¥'ely. The number (n) of S specimens inFigs. 13 and 14 are 93 for Holocene and 37 forPleistocene clays for specimens having similar wet densities and wvalues since the q*(s) and E50(s) for each plot inbetween the ordinary and small specimens are also similarsince the effects of specimen proportions on the strengthproperties are similar.The unconfined compression test using the S specimenwith suction measurement is better for effective use ofsamples and measuring strength properties and determin- SHOGAKI1_･860o Bothkeru,arA Osaka la 2o Hoioceneclay D KisT'haec hYai (H)A pjeistocene elay a Busan ¥. 'ew Port A Iwai (P)A Diatomaceous mudstonehYai {O)a YangsanPleistocene clayRq*50l .4RE'¥' 40Mean value ofRE O * O.99cn37oMeanal .020.090.990,lOa' Standard deviationLr)oC: 1.'O1rlr)e)h_" 30VecPA Ab--J -Ar-A--c-AA ,X- o. -9Ao:O ) o1 O6-- i< ec Do'¥lOoc')or ) O_8q,:'cr fl' ."AAOAl.5 0.5O.50.6lOO 150 200 600 100050oUnconfined compressive strength, qFio. 12.Relationships bet veen RESO and q*nHolocene clayRqRE50)K.' 4093Mean0.lOl 020.1630that ¥vere taken from 26 different sites in the UnitedKingdom, Korea and Japan. These soils consisted ofHolocene and Pleistocene clays plus diatomaceousmudstone and highly organic soils.ACKNOWLEDC.F,MENTThe author wishes to express his sincere *'ratitude toMr. Yoshikazu Maruyama, Syuji Shirakawa and Ryos)Sakamato, ¥vho ¥vereDefense Academy, forworks and also to thethe Port and Airports)c･* 20lOO0.5RquFig. 13.The statisticai properties of Rq* and RESO (Pleistocene clay)al .03(T Standard deviation0:l.5(kPa)6050Fig. 14.1RE50Rqul.5 O.5l.5RE50The statistica properties of Rq and RE<0 (Hotoceue cla)')graduate students of the Nationaltheir cooperation in experimentalGeotechnical Survey L,aboratory ofResearch Institute for the use oftheir Bothkennar and Yangsan clay samples in hisresearch.NOTATIONCC: clay composition of less than 5 !!ming statistical properties.E50: secant moduluslp: Plasticity indexOCR: oveFconsolidated ratios defined as the ratro of effectl eCONCLUSIONSThe conclusions obtained f'rom this test are summarized as follo¥vs:1) The unconfined compression test using S (or Smallsize) specimens of 15 mm in diameter and 35 mm inheight ¥¥'ith suction measurement is better for measuring strength properties and determining statisticalpro perties.2) The standard deviations of the ratios of q and E50values of the S specimens to O (or Ordinary size)specimens (d35 mm and /780 mm) ¥vere in the rangeof 0.09 to 0.16. The 100/0 variation from the meanvalue reflects the soil homogeneity since thecoefficlents of variations of the undrained shearstrength for the undisturbed and reconstituted soils¥vere 8 - 170/0 (Matsuo and Shogaki, 1988).3) In an engineering sense, there ¥vas no difference inoverburden pressure (a( ) to preconsolidation pressure ((T;)q : unconfined compressive stren_ thSo: specirnen sucrion before shearu: pore ¥vater pressureIt'L: Iiquid limitst' : natural ¥vater contentT4'p: Plasticity limit8*: axial strainef: stFain at failurecr: axial stress(T(*: effective o¥'erburden pressureREFF,RF,NCF,S1) Japanese CJeotechnical Societ¥.' (2000): Preparation ofSpecinlens ofCo(?rse Gramdar Materials for Tria_1'ia/ rest. JGS 0530-2000,454-46,_ (in Japanese).2) Japanese Geotechnical Society (2005): The method for obtainingsoil samples using a thin-¥valled sampler ¥vith fixed piston, JGS12_,1-2003. Standards of Japanese Geo,ecJlnica! Society forbet¥veen the S specimens and O specimens from soilsObtaiiling Soil Sanlp!es -Srandarc!s arld E_rp!anations- ( Eng!is/7version), 1-9.3) Japanese Geotechnical Society (2005): The method for obtainin_"..soil samples using rotary double-tube sampler (JGS 12,_,_-2003),ha¥'ing plasticity indexes rangin*" from 10 to 370 andStandards of Japanese Geotechnia7! Societ.v for Obraining Soi!unconfined compressive stren*'ths of 18 - 1000 kPaSanlp!es -Sta/7dards anc! E. p!anations- ( Eng!ish versi0,7), I O- 14.shear strength and deformation characteristics 可SPEC獄1EN SIZE EFFECτ4） Iapanese Geo［echnical Society （2005）：τ麺e metむod for obtaining三29 samplers，（｝θo∼εchnicα1Si∫θC1∼α’｝ααθ舵α”o’∼，Atlanζa，419−424、 so㍊samplesusingrotar｝’trlple−mbesampler，／G51223−2003，19） S｝10gaki，丁．andで〉latsuo，茜1，（玉985）：Factor analysis apProac酒to 5fαηゴα1噌450ゾ／αμznθ∫εGθo∼εc1∼’1iごα！Soご’（∼ぴ∫io1『0δ’α’∼∼iπg So〃 賦consoildated undralned sbear strength oll clay wi由 some Sα〃∼με5−S∼αn面酪α1∼4疎P’αノ∼副0135一（だ∼∼9”5hソθ老5’oη），15−2L co…1sideration on m王croscopic struc【ures，Pro（フ．Sy〃2ρ．Sα〃∼ρ1”∼9，5）Japanese Sこandard Associatlon（1993）：Me由od flor uacon負ned 三〇9−116（in∫apanese）、 compressionζests，／1S〆1／2／6−1993，王一王1（in Japanese）、20） Shogaki， T．， ｝vloro， ｝｛． and Kogure， K、 （1995a）： Stat玉sこ呈cal6）Kamei，T、andτokida，M．（1991）II浦uenceofspecimensizeon properしies of so員da【a with111乳hin一、va11ed sa荘1plers，P∼oc、5rh∫n∼、 題ncon負ned compressivestreng家h and deformation cむaracζer玉stics of C喚1∼o’■θ‘η∼oF po1αノ’」薮1∼9．Co1∼∫，406−413，Hague． co執esive so盟s，Proぐ． 45’1∼！1’1’1、 Co’1ゾ1． ／SCE， No、436， HI46，21）Shogaki，τ、and Kaneko，M、，Moro，｝｛、aad Mi員ara，S．（1995b）＝ 131−134（ill Japaaese）． Me般10dforpredictlngi’∼一蜘’undralneds［reng【hofclaysby uncon員nedcOmpressio旧es［withsuctiomneasurements，Proご、7）Lo，K、Y．（1970）：τむe oPζical s甘eng由of臼ssured clays， Gθαθぐhnゆθ，20（2），57−54、 ⑤y〃1ρ．So〃Sα’nρ1’n9，95−102（ln、lapanese）．8） N｛atsui，T．，Oda，K．and Nabes員i斑a，Y．（1994）：Deve皇opmellt and22）Shogak玉，T．，へ・loro，｝・｛、and L4atsuo，｝v玉．（1997）：A slope stabi韮ity apPllcationsforna〔uraldepOsitsofmlnimu磁triaxialcompresslon analys玉s co真sidering undrained stre疏9【h anisotroPy of natura里c蓋ay apParatus，7寵κh1∫oκ’50，42（H），17−22（in Japanese）、 deposits，T51ごch’イo−1ぐ’30，JGS，45（8），13一王6（in Japanese）．9）Matsuo，M．and Asaoka，A、（1976）：A statlstlcal study on a conven一 芝ional safセty factor meζhod，Soiたrαηd「Fo∼〃1（ノαだoη5，玉6（1），75−90．10） Nlaτsuo，N’i、and Shogak玉，T、（圭988）：E廷壱αof−Plasticity and sample23｝S員ogaki，丁．and Noc鼓ikawa，Y．（2004）：Triaxial stre119重妓properties ofnaturaldepositsaτκoconsolidaこiOnsエaヒeuslngaprecislOntriaxi− aL apParatus w註h sma賦size specimeus，So〃∫απグFヒ）μnゴα’101∼∫，45 disturbanceonstatlsticalpropertlesofu痘drainedshearstreng出， （2），41−52、 So’Z5α∼∼ゴFoπηo「（rがo／15，28（2）， 14−24・24）Shogaki，一、and Sakamoこo，R，（2004）l I妓e applicab瓶ty of a sma賊11） Nakase，A、（1967）：τheφu二〇allalysis of sζab重販ty and uΣ1con且ned compressioΩstrengt騒，SoiZ5姻ごF加ηゴα1io1∼5，7（2），35−50、12） Shogaki，T、（1995）：E9琶c【ive stress be姓av1or of days玉n uτ1con且ned compressiontests，So11∫oπゴFαご11伽’01∼5，34（4），169−171．王3）Shogaki，T、（1997a）：Asma麺diametersamplerwi芝hatwo−chaτn− diameter sa磁Pler witね a エwo−cむambered ぬydrauまic piston for 、laPanese clay dePosi工s，So’Z5α’∼ゴ’δ置’nゴα’io刀sシ44（1），113−124、25）S熱ogaki，丁、，Sakamoto，R ，，Kondo，E．andTac撤bana，H．（2004a）： Slnall diameter cone sampler and its apPHcabih【y for P韮eistocene Osaka氏／1a 正2clay，So’Z5απ‘ゴFo直〃1ゴo”oη∫，44（4），119−126． bered hydraulic piston aad￡he quality of its samples，Proc．14’h26）Sむogaki，τ、，Sakamoto，R．，Kanno，Y、and Nakano，Y．（2004b）： lCSM■五，Hamburg，201−204、 Small diameter cone sampler and iτs apr）licab11ity fo由ig恩yorganlc玉4） Sねogaki， τ， （1997b）： Strengtむ prope賞ies of c里ay by portable uτ1confined compression apParatus， P1’oご、 1／r∫。 Co17ゾニ G（∼o∼（∼ご1∼． 石ngrg、、弄o〆Co鯉α1P8vθ10ρ、，85−88．15） S轍ogaki， T． （2006a）：亙〉1玉crostructure，strength and consolidation properties of Ariake clay depos1ts obIained frQm samplers，／． 〆is7’闇ル望「11πθ1’、，3（5），98一王05．16）Sむogaki，T、（2006b）：An improved meτhod for estimat沁g ln一誼ε’ clayeysoils，Pヂoc、11π．S｝，〃∼ρ。E119’nθ帥1gPrααicθθn4P師01・ ’ηα1∼α∼oゾSoゾ1∫∠）θpo5’∫5（1S−Osαなα2004），153−158・27）Sむogaki，丁、，Nochikawa，Y、，Jeong，G．R．，Suwa，S．aRd K姓ada， N．（2005a）：S韮reΩgth and consdidation properties of Busan New PorζcLays，So’なα’1ゴノ＝oμn4α’10η∫，45（1），153−169、28）Sむogaki，T．，Sakamaこo，S．，Nakano，Y．and Shibata，A．（2006）：撫e appllcabiliζy ol’smaII diame菰er sampler for Niigata sand undrained shear strength of natural deposi［s， So”5 αηご deposits，So〃5σ∼∼4Fα’1∼ゴφo’1∫，46（1），1−15． Fo乱〃∼ご（πioη5，46（2），109−121．17）Sねogaki，丁．and Ma田yama，Y、（1995）：丁益eρortable uncon負ned29）Tanaka，H．and Locat，J、（王998）：Recollsideraζion of由e meanlng Qfplas￡icityindexingeotechnicalengineering，75ε’c1∼1一’o一幻50， compresslQII apparatus and iエs applicaこlon，Proc．40’1∼／GS＄γ〃∼ρ，， JGS，46（4），9−12（in Japanese）、 287−294（in∫apanese）、and Maruyama，Y．（1998）l Es芝imation of in一∫i∼‘’18）S藏ogaki，T undrained shear strength using disturbed samples witねt1｝in−waUed30）Yosむln＆ka，R。（1976）：E艶ctofspec1買1ensizeonsζrengthoflrock so玉1s，5θんoμgびε’！5μ，9，58−60（in∫apanese）。 | ||||
| ログイン | |||||
| タイトル | 3D-Visualization of Ground of New Runway at Haneda Airport | ||||
| 著者 | Masanori Tanaka・Yoichi Watabe・Masafumi Miyata・Saiichi Sakajo | ||||
| 出版 | soils and Foundations | ||||
| ページ | 131〜139 | 発行 | 2007/02/15 | 文書ID | 20986 |
| 内容 | 表示 TSOILS AND FOUNDATIONSVol. 47, No-1,131l39, Feb 2007Japanese Geotechnical SacleL)3D-VISUALIZATION OF GROUND OF NEW RUNWAY AT HANEDA AIRPORTMASANORI TANAKAi), Yolc ru WATABHi), MASAFU "{1 MIYA'TAii) and SAIICHI SAKAJO ii)ABSTRACTThe 4th rumvay of Tokyo Haneda International Airport is no¥ ' under planning. The distributions of lveak layer,bearing layer and their en*'ineering characteristics must be clarified to some extent. Prior to detailed foundationinvestigations leading to for detailed designs and constructions. Ne¥v soil investigations of boring, sampling andlaboratory tests ¥vere conducted in this area. Using these data and the past boring data frorn the database, the vhole3D ground was visualized by the 3D soil layer estimation system, that ve have proposed. Subsequently, the 3D groundfor the rum¥'ay could be successfully modeled. This 3D model is very useful to recognize the general soil layer compositions for planning the detailed soil investigations on their test items, depths and numbers. Furthermore, this result isexpected to reduce the costs regarding numerical analysis, design and construction.Key words: alluvial deposit, dilu¥'ial deposit, geology, Kriging, standard penetration test, visualized 3D ground (IGC:CO /C3 /C4 IC9)INTRODUCTIONThe Ministry of Land Infrastructure and Transport(MLIT) has started a committee on "Third Anpcut m theMetropolitan Area Survey" since 26th September, 2000to examine the shortage of air'port capacity in Tokyometropolitan area.O ayFollo ving that, the MLIT had offered a basic construction plan of the 4th run¥vay. This new r'umvay ¥¥'ill beconstructed ofishore to the south of the current Hanedaonnecting bridgeAirport. It ¥vill be parallel to the B runway in the north assho¥vn in Fi**. 1.In order to r'ealize this plan, full scale soil investigations ¥vill be conducted. Before this, the distribution ofthe weak layers and bearing layers must be determined ingeneral and their soil characteristics must be identified.Usually in case of the routine soil investigations, the*'eological features are drawn on the main 2D sections ofthe construction fields. Follo¥ving that, the geological¥lFig, l.Basic plan of re-expansion of HanedQ 1000nL-lAirportfeatures on their perpendicular 2D sections would bechecked additionally. However, in such a lar*'e scaie andlayer classification criteria obtained from multi-re*'ression analyses of soil parameters.Therefore, the ne¥v soil investi**ations were conductedin the construction area and alon*" axis of the connectingmassive area in Haneda Airport, the ¥vhole groundshould be classified and displayed in 3D.On the other hand, the authors have proposed the 3Dbridge between the new runway and the Haneda Air'por't.Finally, the ground for the ne¥v run¥vay vas displayed insoil layer estimation system in order to increase the utilityof the soil database in engineering practice. This systemhas been successfully applied on the various sites.This system can specify soil layers in 3D by inputtin*' aset of soil parameters estimated spatially into the soil3D by usin*' this system based on the nelv soil investigation results and the past boring database.The boring database used ¥vas developed by the Port*) Geotechnical and Geo-environmeut Division, Por and Airpor Research Institute, Japan (tanakam@pari go-jp, ¥vatabe@pari.go.jp).'*) Haneda Airport Expansion Project Section, Kanto Regional Developmem Bureau, Minis r¥ ' of Infrastructure, Japan (miyata-m92v2@pa,kur.mlit.*･o.jp).=**)Applied Information Science Center, Kiso-Jjban Consultants C*0., Ltd. Japan (sakajo saiichi@kiso.co jp).The manuscript for ihis paper vas received for revie¥v on January lO, 2006; approved on Jul_v 26, 2006.¥Vritten discussions on this paper should be submitted before Septernber 1, 2007 to the Japanese Geotechnical Society, 4-38-2, Sengoku,Bunkyo-ku, Tokyo 1 1'_-OOI 1, Japan. Upon request the closing date may be exiended one month131+ TANAKA FT AL.132from A-3 to A-7 and the sites from A-9 to A-13 arelocated alon*' the sea side and the airport side from theaxis of the runway respectively. The sites A-1 , A-2, A-14and A-8 are located on the axis of the new run¥vay. Thesites from B-1 to B-3 are located on the axis of the br'idgebetween the new run¥vay and the existing HanedaAirport. The distance bet¥veen these borin*" sites isapproximately 500 m. This distance is of course not closeenou*'h from the Japanese design codes. Ho¥vever, theaverage distance of the new borings in the area to bedisplayed in 3D is 750 m. Therefore, the authors used the26 old boring from the database of Port and AirportResearch Institute. Although they are not scatteredhomogeneously in the area, the avera*'e distance amon__'ail boring sites could be reduced to be 470 m.This value is still not close enough for the code of earthwork in .Japan. The Japanese Road Committee suggestsFig. 2. Area to display ground in 3D and atl soiinvestigationsthe appropriate distance to be 100 m for the preliminarysoil investigation of sounding and sampling. This is theand Airport Research Institute. It contains 22,000 borin_'reason why the acoustic explorations were conductedlogs ¥ 'ith SPT results and soil property data. In thisconstruction area, the 26 borin*" data ¥vere used from2,300 boring database in Haneda Airport.The main purpose of this research is to investigate ifthis soil layer estimation system can make a realistic 3D"_round model in such a large scale area. Subsequently, atogether ¥vith soil investigations. However, this distance3D **round model was successfully made because therewas adequate soil data available though not abundant.This implies the importance of soil database use inmodeling ground.AREA TO DISPLAY IN 3D AND AVAII.ABl,EBORINC. DATAof 470 m seems to be able to guarantee accuracy to someextent from the correlation of the soil parameters.Because the statistical result of soil properties su"-*'eststhat the maximum distance to estimate soil properties is470 m.Geo!ogica! I,ayers ii? TTvo Cross Sections a!ong t/1e MainA xisBefore conducting 3D soil layer estimation, the generaltrend of soil layer structures must be reco*'nized ft'om theboring lo*'s. Herein soil layers on the t¥vo cross sectionsaltitudes of ground surface and bedrock. Then, the soilalon*' the traverses, 1) airport side and 2) sea side aresho¥vn in Fi**. 3. These figures vere made from boringlogs by the geologists. These are not correct geometricallybecause they are projected on the same sections althou*'hthey are not on the same sections.From these figures, it is seen that four main layers, 1)Yuraku-cho layer, 2) Nanago layer, 3) Tokyo layer and 4)parameters would be estimated in the 3D space byEdogawa layer are deposited from the surface. Yuraku-Kriging. The criteria to classify soil layers would be calcu-cho layer is the upper half part of alluvial layer in Tokyolated by a multi-regression analysis of several kinds oflo¥v iand. It was deposited in the sea by the sea level rise insoil parameters. It is possible to define the soil layer nameat a specific point.layer is the lo¥ver' half part of alluvial layer in Tokyo lo¥vIn order to apply the three-dimensional soil layerestimation system, the available boring data and soilparameters must be re*"istered on the digital map. First,the 3D estimation area should be defined with theThe area to be displayed in 3D and all soil investiga-tions are marked on the di**ital map around HanedaAirport in Fig. 2. The target area is the inside of a rectan-gular square 4,300 m by 2,200 m. There is also the rectan-gular mesh of acoustic explorations. In this area, theJohmon era beginnin*' about 10,000 years ago. Nanagoland. It ¥vas deposited in the fresh¥'ater to sea water be-fore around 18,000 years ago. Tokyo layer is the diluviallayer ¥vhich consists of upper marine clay, middle sandand lower mixture of sand and **ravel. Edo*'a¥va layer isthe diluvial layer which consists of the upper sand and thelarge white circle ( - , ) sho¥vs ne¥v boring site and the blacklower sand containing clay. They both have bedrock ofcircle (o) sho¥vs old borin*' site in the database. Smallgravel. These layer boundaries ¥vere manually interpolated from the boring lo*"s. Furthermore, each layer consists¥vhite circle ( ' ) sho¥vs boring site out of the area. At theboring sites, SPT and samplin_9: ¥vere conducted. Severalof more than t¥vo sub-Iayers of clay, sand and gravel.kinds of soil tests lvere conducted at laboratory. SeaTherefore, the layer structures are actually very complicated.depth ¥vas measured in this area to investigate theThree traverses of sea side, airport side and bridge axisfor soil investigations are sho¥vn in Fig. 2. The 17 borin*'sHowever, the characteristics of these layers can beroughly understood from SPT results in boring logs.N-values for Yuraku-cho are too smail to be measured.vere conducted at A-1 to A-14 and B-1 to B-3. The sitesN-values for Nanago layer are 20-30 for sand and are less_9:eographical **round sur'face in the sea., TNE¥¥! RUN¥¥IAY A'T HAi¥'EDANanagoTama-Rivero()Jonan-Isl ndstrong. The forrner and the latter are ar'ound 50 and more;A-8[A-9 A-iOj ----{ A-iilA-i2] A-i3]A-2 A 1-10()-20 o133than 10 for clay. Tokyo layer and Edoga¥va layer areYu aku- ho layeFla yerAIRPORTthan 50 respecti¥'ely.Even though these t¥vo sections are only 400 m a vayfrom each other, some difference can be seen. Yuraku-l-30 o-40 O-50 ocho layer on the airport side is a little thicker than that on-60J) }the sea side. On the sea side, bet¥¥'een boring sites of A-5-70()-80 oand A-6, the boundary of Yuraku-cho layer and Nanago:-90 o-ioo o= 'Hgoes lower than on the airport side. Nanago layer on theiisea side is a little thinner than that on the airport side. OnH800 1,200 1,60c; 2,000 2.400 2,80a 3,200 3,600 (m)the airport side, Edoga¥va layer is much rnore intrudedbedrock Edogawa iayer Tokyo layerinto Tokyo layer' than the sea side. Therefore, the cr'osssection on the sea side seems veaker than that on theairport side. Such complexity was due to the Tama RiverEdogawa layer is muchintrudecl into Tokyo layeractivities over a long time with the many repetitions of sea(a)¥vater level changes in the glacial age.Any engineers regarding this project have to pay attention to the distribution of the bearing layers for designsand constructions. Therefore, the authors tried to definesoil layer constitutions in 3D r'ationally in this area. Theinformation used are 1) boring, sampling and soil properties, 2) acoustic exploration results, 3) soil database, 4)The boundary between Yurakv-cholayer and Nanago layer is lowerbetween A-S and A-6,Tama-R;verNanago layer Yuraku-cho iayerOOJonanIs!andO O-20 O-3 Osea bed depth contour map and 5) geological informa-O-40 Otion.50 O-60 OThis time, from an engineering point of vie¥v, it has-70 O-80()been requested to classify all layers into the ) Iayers, i)alluvial soft clay iayers, ii) diluvial clay layer mixed ¥vith-90{):'.*"-'" '><";',''sand, iii) diluvial sand layer ¥vith N-values of about 50,iv) diluvial gra¥'el layer with N-values of more than ,50and v) bedr'ock layer. These 5 Ia)'ers roughly are drawn":-100()400 f800.200 1,600 2,000 2,400i2,800 3,200 3,600 (m)Tokyo layerEdogawa layerbed ro cktentatively in this figure.It is actually a ¥'ery difficult task for geologists and civil(b)traverse and (b) Geologicai soil la¥. er constitutions on the sea sideengineer's to define the soil layer' boundaries experimentally. Especially, in determining the layer boundaries fortraversethe above Edogawa layer, the pre-defined results ¥vereFig. 3. (a) Geo!ogical soil la¥.'er constitutions on the airport sideTable 1.Data No.Soil data of A4AhitudeSoil layer(A.P.)(m)¥VaterPlasricit.vcontent t'**index lpFlnecontent F*(g /cm3 )(o/o)(o/o)(o/o)157.S146.2145.2138.9142.8i33.688.3S-'.360.446.898 699,799,799*499,799 4, 6.584 . 1SpecificN-vaiuegravit*Geolo vEng.YvcYucYucYucYucYucYucAcAcAcAc- 21 .032 . 662- 24.03- 28.53YlcYlcYlcAcAcAcDcDcDc2.6382.6362.6382.5932.6362 6192.7082 7512.712, 6ToclDc- 72. I l, 7Tos lDs- 72. 9428Toc7Toc _- 74, 1 11346789lO. 5.53- 27 .0331.53- 34,,53- 36.03- 37.53- 40.5379.272.259 l43 . 76. 153.144 842.3655764.9Z31Toc2Tog23,To :2DcDcDcDgDg33Eds2Eds2DsDs2930342.72123- 76, i l- 77.88- 78,32- 83.3388,37- 93,362.7322.6682.6752 661more than 50nore than 50more than 50more than 502.832.7372 7342 709X-coordlnate: - 960 rrl, Y-coordinate: - 57_,OOI m (Digital coordinate), En . Is engineermg name.44.827 3, 9,74)-.539*935.421 950. i29 78.7457.429.385.895.992.910.48.728.24 1 .216.518.5 134TANAKA ET AL .modified based on the acoustic exploration results andAn unknown value can be esrim tedthe *'eological fact, that the layer contains volcanic ash.from suri-ounding knol n¥'al uesColltents of Soi! Data on DatabaseIn this research, the database developed by Port andAirport Research Institute is used and all new soil investi-ation data ¥vere registered with the same database form.An example of the soil data at boring site A-4 is sho¥vn inTable i. In the database, geolo_ :ical soil layer names arerenamed to be alluvial layers and diluvial layers asengineering names. The former names are alluvial clay(Ac), sand (As) and gravel (A**) Iayers. The latter namesare diluvial clay (Dc), sand (Ds) and gravel (Dg) Iayers.¥Fig. 4.Target SpaceSpatial statistics tecl]nique by KrigingYuraku-cho clay layer and sand layer were renamed asAc and As layers. Yuraku-cho lower clay layer was re-technique, because any information obtained at manycategorized to be Dc because of its similarity ¥vith Nanagoclay layer. It ¥vill be explained later. Clay. of Nanago,seen in Fig. 4. These data should be in the target space tointerpolate them. This method also can be valid in 3D andhas been applied widely to the various fields in geo-technical and geological practices. The estimated value z (x) canbe expressed by the ordinary Kri_ging as follolvs summar-Tokyo and Edogawa layers ¥vere renamed to be Dc layer.Yuraku-cho lo¥ver clay layer ¥vas renamed as Dc, becauseIts characteristics are similar to Dc. This reason ¥vill beexplained in the later section.This database contains l) N-value, 2) ¥vater content w*,3) plasticity index lp, 4) fine content (percentage of smallparticle less than 75 /Im), 5) specific *"ravity and so on.Furthermore, it contains 6) X-Y coordinates (localcoordinate of Haneda) and 7) altitudes of ground surfaceand soil layers. And it is not explained here but thisdatabase also contains a fe v mechanical test results likeoedometer test, unconfined compression test and tri-axialcompression test.Each of these data is useful for the geotechnicaldesigns. This database ¥vill ho¥vever be much more usefulif some of them can be the criteria of soil characterization. Furthermore, the authors 'ill define soil layers byclassifying soil types. In this case, the applicability of soildatabase ¥vould increase very much.3D SOIL LAYER F.STIMATION SYSTEMpoints can be rationally estimated at a certain point asiz,in>" all the observed values (Cressie, 1993).z (x) =wjZ (xj) (1)where, z(x): estimated value at the location x, wj: weightfactor at the location x!, z(xi): the observed value at thelocation xj, N: number of observed samples.The above weight factor is calculated from thecovariance among the observed data. The weight factor isrelating mathematic,ally with the secondary order errory(/7), which can be calculated by the following equation.=1{z(xj)-z(. 'j)}22Nh i,jwhere, y(11): the secondary order error for the data thatare h far away each other, /7: the distance bet¥veen dataeither in horiz.ontal direction or vertical dir'ection, Nh:number of pairs of samples with a span of /1 among them,Z (xj): value of a sample at the distance of xi, z (xj): valueAny soil designers are required to define soil layers andtheir soil parameters rationally. This task can be achievedby this 3D soil layer estimation system.This system can judge ¥vhich soil layer a specific soillayer belongs to. It can be done by inputting a set of soilof a sample at the distance ofparameters interpolated spatially by Kriging method into¥vhere, y(h): the a, c and d are constants to express y(h).the classification criteria, ¥vhich is calculated throu*'h theIn the above equation, the y(/1) becomes a constant ofd at that h is O. On the other hand, the y(/7) becomes d+ cat that h becomes + oo. The cut d means a potential errormar*'in. From this equation, the larger a is or the smallerc is, the smaller y(h) is ¥vith the larger /1. Basically, themulti-re*'ression analysis of these parameters (Tanakaet al., 2002, 2004a).This system has been applied to the marine clay inOfunato harbor (Tanaka et al., 2004b) and the slopedi'Finally, the caiculated relation of y(h) and h can besimply assumed by the follo¥ving exponential equation.y(h) = d + c(1 - e }*/*) (3)g:round in the mountainous area of Shikoku Islandabove equation expresses a natural decrease of correla-(Tanaka et al., 7_005). If it could be linked with GIStion of data estimation with the horizontal distancesystem, this system ¥vould be more convenient and useful.increase. This relation is called to be variogram, ¥vhich(Sakajo, '_005).can be selected from various mathematical functionsEstil77atiol? of Matel'ia! P/'oper'ties by Kl-igingbesides the exponential curve in this system.As an example, the calculated y(h) values and horizon-The geologists and geotechnical engineers usuallyestimate the soil layers experimentally ¥vhen makingtal distance h on N-values at the Haneda district aregeological sections. In such a case, Kriginca seems a goodalso is shown in this figure. From this figure, it is seen thatplotted in Fi*･. 5. An approximate curve of the Eq. (3) NE¥V RUN¥ ;AYAT HANEDA AIRPORTl 35600Eva!uation of Estilnated Soi! P/'ope/'ties on the Main Axis500f'ol' the Present P!anFigure 6 sho vs N-value distribution in 3D estimated by400Krrging. Color index is that dark blue is less than 10, Iightblue is 10 to '-O, green is 20 to 30, yello¥v is 30 to 40, and>* 300200100oO 5002 500 3 Ooo1 ,OOO 1 500 2,000horizontai distance h (m)( s; )and Edoga¥va layers, but unf'ortunately these color' gradations are not ciear in identifying these layers. These colorsare changing at places and a green color area is seen in theLTalue500400Et :: c] Pr(h) * 150 - 200(1OQe = ** )300ha200 1_ t];.:;measured piasioityindex PI,- ap roxirnatB curve1 OOored area.To see more details, the 2D cross sections of N-value,plasticity index lp and natural ¥vater content }t' are sho¥vnin Fig. 7. These are the cross sections on the main axis ofthe ne¥v run¥vay, vhere the boring logs on the airport sidetraverse are projected as references.In the figure of N-¥'alue, it is found that the ¥'ery softground ¥vith N< 10 is deposited from the surface up too 5001 OOO500 2 OOO 2.500 3,000horizentai distance h (m)( b ) ptnstieitv_A.P.-35 m and the soilvith 10<N<'_O is depositedf'rom the bottom up to A.P. -50 m. Under thls, ratherstrong soil ¥vith 20<N<:40 is deposited up to A.P. - 55Qde: /1*m. Furthermore, strong soil1 200r(h) ･OO800>* eooOO(1 e * ' *)Q 'E=deposited almost horizontally below A.P. - 55 m.FJoF Q rTleasured water-content- approxirn te eurve200oO500 1,000 1 500 2 OOO2 500 3 Ooohorizontai distanee h (Fn)( c ) watcr conte t f'*Fig. 5.vith N-value of' rnore than50 is deposited belo¥v it up to A.P. - 80 m. These findingsare simpl.¥* summarized in Table 2.Generally, the soil vith N-values of mor'e than 40 isooO400red is 40 to 50 and more than 50 in N-¥'alue. The darkgreen means the bedrock. Therefore, the distribution ofbearing layer ¥vith N> 50 can be understood from the redcolor and dark reen areas.The yello¥v to red color areas seem to be in the TokyoVariogram of IV-valueHo vever, there are weaker' soils with small N-vaiuesbet¥veen A-10 and A-11 and through A-1 to A-13. Fromthe figures of l and w , the portion between A-10 andA-1 1 seems to be sand or intermediate soil because I+. isless than 20 and w** is less than 500/0 there. The soil fromA-1 to A-1,3 seems clay because lp is about 40 and 4'** isrnore than 500/0 there.Combinations of soil parameters, N-value, Ip and w'**can determine soil characteristics mentioned above. Theestimated accur'acy of these soil properties by Krigingvilly(h) increases ¥vith /1. It meets a turning point at h of 500be explained in a separate paper.m and it becomes a constant at /1 of 2.000- 3,000 m.Another reason for 500 m to be the maximurn reliableMu!ti-Re*"/'ession Ana!ysis of Soi! Data for Soi! Layej'distance to interpolate N-value, is that cyclic frustrationsof data are seen after h of 500 m in this figure. It may bethat the observed data are not enough in the target spacesaid longer than the 500 m. This means that the maximum distance to estimate N-value should be ¥vithin 500C*!asslficatiol7 Cl itel'iaHerein, the authors ¥vould like to explain soil classification criteria for the soil parameters. This is equivalent todefinin*' the soil characteristics. Multi-regression analysism. An average distance bet¥veen borin_g: distance is 470 mamong the soil parameters can produce these criteria.Then, by inputting the soil parameters estimated byin the soil investigation. The estirnation capability by thisKriging into these criteria, all soils can be classified to besystem is close to the limit. This conclusion was support-in the proper soil layers.ed by the same relations of y(h) values and horizontalExamples of criteria by regression analysis are, 1) acr'iteria from natural ¥vater content and fine content anddistance /1 on plasticity index and ¥vater contents.From this figure, it is interesting that N-value has anerr'or at that h is zero, ¥vhere the y(/1) is about 100 and itssquared value is 10. This implies that N-value might beabout 10 different at t¥vo very close points due to the inuniformity of soils. This is the resuit in the horizontalway. The vertical lvay also can be considered, althoughthe rather poor correlation with distance vould be used.2) another criteria from altitude and plasticity indexsho 'n in Fig. 8. Clay and sand can be separated clearlyand Ac layer and Dc layer can be separated clearly.In this lo¥ver figure, Yur'aku-cho lo ver layer vascateg:orized into Dc. 'The criterion ¥vhere itvas classifiedto be Ac, seems unnatural. Therefore engineering properties are very Important in classifying soil types. I OO. OTANAKA ET AL^136H#ntds A "Table 2.5D{_.';1;! 40Ct]aracteristics of the estimated soil properties bl.' KrigingPlasticity ¥Va erAltitude(A P.)soillp (o/o) Ts'** (O/o)( n)105rT)Supposedindex con emN-valuelayer{ .;.- -35 m10> 30O - 10(dark blue)Ac> 50(green lo (gTeen toyello¥v o red): yello¥v, red)ON-ve; e3) m - - 50 m< 30lO - 20Fig. 6. 3D distribution of estimated !¥r_value (SPT))O m - -55 m30 - 50(light blue(light blue)to blue)20 - 40AslDc(light blue) ,Ds/Dg< 30(green to(blue)yello¥v)Tama-RiverJonan- Isiand-55 m- 80 m1 o o i--0.0 --- A-8A*9 IA*iO I: AIi A i2 A 13 A-2･ A-iIT'ith 20 to 3050-*-30. O '----40. O '---40-50.0 *-"-; 30lOO2090IoSoSO O i-----70 O ----80 O J---e ool 200 1,800 2,400 3000 3.800 (m)O70-va ue60T m -RJverJo!A-9 : A-lOAAAA A1A AA ^ ^^L"a!)AASA4 4 ; " AAiOl ,, A,.( a)0.01 A 8Bedrock- 80 m --20 O T--ODs / D_",*(red)N-valuesOO--90 O> 40 - 6050oo40 oo c}30 ooo -'n-ls andA 11 A i2 A i3 A 2 A-1 !pisabout40.20 -- I 0.0 --s hdoA Clavo Sand- Boundan' Lineo ciO -- eoe;o-20.0 --o50o200150lOO1 '( )(a)70.0 ----Criter'a to set-80.0 l.__-90.0Yurakl'-che layer to Ae-- .O-1000*- -500 1 200lp is iess than-O1.800 2.400 3000 3,600 (m)fJonan-[slandTama-River230 1":'el'"".SltT"a"III II q' ' $- 'e8 vol"o.,?J't'P(b)l t; ,':l'l'e i'1 ･e'] o"' :rT ;dP';P:' e Ie'::Qe(po10 IfSo "' "-' T "' L :' ･ d""" t" ' , . f1 o{) +--OOA-8 [ A-9 [A-iO A-liA-12:A-i3-1- A-2 --- A-1 ti'n is more than 50- 00+-20 o !----soJe' 4I4 "I"'c ' AAAd:80A'_ ' ' I*'[ "!AI':;su-ehofwfle Ac(YUraku-co upper layeAoi J':A1 '1h'I l;- : '-90d L ., , ,A Dej BotJndsrye (A$)-ioo"' 8QundsryLiLine(De)-70 O '-O-800 t ---20sobedroek_;={ll: wn{ )200 1,800 2.400 3,000 3eOO (m)6080T OO!, (Cr{te a to set-1 OO O * ---O 600id<To i-90.0lll:. 'e -Yuraku-eho lewer layer ta De(b)t'rs is le_ s 50(c)Fig. 7. Estimated properties on main axis of the nelv runlval ' of thecurrent plan: (a) 1¥r_va ue (SPT), (b) Plasticity index (Ip) and (c)N. 'atural water content (,t' )Fig. 8. Examples of soil classification criteria: (a) Fine content (F*)and natura ¥vater content (w ) and (b) Ip and altitude level : ;,NE¥V RUN¥VAY A'T HANEDA AIRPORTTo generalize regression analysis, the following multiregression analysis is adapted employin*' the polynomialfunctions.The equation used is as follows:Y aa Xl+a2'X +a3 X +a X a X Ta6 X (4)13 fAg does not exist in this area. All soil classificationcriteria used are summarized in Table 3.In the actual computation, the computational area ¥vasseparated into boxy meshes as precise as 50 m by 50 m by,50 m. Then, each box was identified to be a proper soiltype by the above cornputations.Where, Y: objective variable, X: explanation variables; Xi: ground level or altitude (rn), X._: N-value, X3:natural lvater' content, w (olo). X4: Plasticity Index, Ip,X5: Fine content, F* (olo), X6: Specific gravity, G.As an objective va 'iable, Y should be set to be a specificvalue (for example, Y=0 can be set that clay is for Y> Oand sand is for' Y<0) and then multi-r'egression analysisis conducted.By inputting the parameters estimated by Kriging intothe above equation, the sign of Y ¥¥'ould be checked tojudge the soil layer.Soi/ Layer C!asslfication RestdtThe ¥vhole ground for' the ne¥v run¥vay is displayed in3D in Fig. 10. The 2D cross sections along the t¥ 'o soilinvestigation traverses and the connecting brid**e ar'esho¥vn in Fig. Il.First of all, from Figs. 1 1(a) and (b), it is found that theAc, Dc, Ds and Dg layers can be classified very clearly,although the layer boundaries ¥vere srnoothed (Shiono,2000). In these figures, the As layer ¥vas neglected becauseit ¥vas sholvn in a very srnall area. The Dg layer boundaries ¥vere rnodified by the acoustic exploration results assimilarly done in Fi*･. 3.SOIL CLASSIFICATIO_N CALCULATIONHere, the authors tried to define soil iayers compositions of the whole ground for the new r'un¥vay by inputting a set of soil parameter's estimated spatially into thesoil layer classification criteria obtained fr'om multiregression analyses of soil parameters.The classification calculation fiow is sho¥vn in Fig. 9.The 3D Iayers model is very useful because any crosssection can be generated ¥vith ease. This can correspondvery easily to the change of plan, even in the case ofchanging the main axis of the runway.To recognize the details, it is better to see the 2D crosssections. The t¥vo cross sections on the airport side andsea side traverses apparently resemble to those inAt first, soils are classified into clay or gr'avel extremely.Figs. 3(a) and (b). Ho¥vever, these fi**ures are very correctSecondly, the soils classified as clay are classified againin geometr'ical scale. These figures were not manuallyinterpolated based on experiences like in Fig. 3. And itlvas assured from the sorne triai calculations that themaximum difference bet¥veen the estimated soil layerboundary levels and those in Fig. 3 is about 2 minto clay or sand and soils classified as gravel are classifiedinto sand or' gravel.Then, the sedimentation types ar'e again classified intoalluvial or diluvial layer. Through these steps of soilclassification, all the soils can be classified as Ac, As, Dc,Ds and Dg. It was noticed that Ag ¥vas ignored because} grain siznsans Airpor(!c I ass i f ica t i anbv sedi entcl ass i f i c_e ! r'4t i Or･rFig. 10. 3D estimated soil la) rs of the ground for the new runwa .'Fig. 9. Calcu atlon flow for sorl classlficatron'Table 3.aealCtassification criteria and their parametersala3(7sa{ravel - O. 9920.000o ,ooo - 0.0990.000Clay-Sand I .5 1 80.000O.045 - 0. 1 20o ooo1 627O . OOOCla.v-(Jl.316C16Y>0Y< O0.000ClayGravelO.OOO ClaySandl 207 -O.OIOO. I I lo.oooAc-Dc0.081 - I .3780,0000,000o 567AsDcAs-Ds- O.7 10 - 0.885o,ooo,_. 1 99o oooAsDsAs D,:'(1- I .OOOo.oooo,oooo oooo.oooAgDgSand-Gravel(;- O. 104O . 3 Sand20 G ravel TANAKA ET AL.13SJonan-lslandTama-RiveOO-a fe¥v new boring data in Fig. 11(c).For the case of O_ funato harbor, the soil layer classifica-0.0-A-8A-9 - A-iOA._ -i_A. .-1._ 2A-13 A-2 - A-i .-1 0.0 --20 Otion was not precise enough because of the ambi..guousclassification cr'iteria due to the shortage of materialproperty data (Tanaka et al., 2004b). In this case,-30 Oho¥ve¥'er, the many soil properties from the soil databasecould be used here to obtain precise soil classificationcriteria. Therefore, it can be concluded that any database-40.050 O80 O-70 Ocould play an impor'tant role in the modeling of ground-80 Osoil in engineering practice.-90 o-1 oo oo600.2008002 4003 ooo3,eOO (m)(a)The follolvin_g: conclusions were developed in thisTama-River*Jonan-ls and100oo1 o O 'A-8 :] A-7 1 A-6A-5CONCLUSIONSA-4 :A-3A:-2A-i --20.0-30{) ;-40 o }50 O-60.0 s{research. Furthermore, the rational and precise 3Dground modeling developed could promise the moreaccurate numerical analysis like on FEM, ¥vhich canexpress ground behavior by the advanced constitutiveequations of soils.1) Ne¥v soil investigations ¥vere carried out offshore atHaneda Airport. By usin*' these data ¥vith the past boringdatabase, the three dimensional (3D) soil layer estimationsystem could clarify the basic soil layer compositions of-80 othe ground for the ne¥v rum 'ay of Haneda Airport.2) Although these borin*' distances lvere not close-90.0 *enough as recommended by the various design or-70 o --1000o600 1 2001 .8002 4003 ooo3500 (m)(b)construction manuals, the accuracy of the estimation canbe secured to some extent from the data correlations withdistance.3) Consequently, the 3D soil layers ¥vere classifiedNe ^/-RunwayAirportOO-B- 1h2B-3A-100.0 -into the follo¥ving five layers, i) the soft clay ground, ii)the alternate mixture layer of sand and clay, iii) thebearing layer with N-values of about 50, iv) the bearing-10(}clay layer lvith N-value of more than 50 containing-20 Opartially clay, v) the continuously ¥'ery strong bearinglayer' ¥vith N-value of more than 50.30.0-40()4) This 3D _g:round model wiil be very useful for a-50 Odetailed investigation to define the place, the depth, and-eO Othe number in preparation of constructing this run¥vay.70 OIn addition, since the soil layers were once clarified in 3D,80 Oit is possible to dra¥v any corresponding cross sectionseven if a present plan would be changed.-go o5) This 3D soil estimation system based on the soil-1 OO Oo 200 400 600800 l ooo.200 (m)(c)Fig. 11. Estimated soi] Ia: .'er classifications: (a) On the airport sidetraverse, (b) On the sea side traverse and (c) On the axis of theconnectin"* bridgeproperties estimated by. Kriging with the soil layer classifi-cation criteria from multi-regr'ession analysis is extremelyeffective to define en_g:ineerin*' Iayer compositions.6) The soil database used in this study developed byPort and Airport Research Institute ¥vas found to behighly applicable in geo-technical engineering practices,if used ¥vith this soil layer estimation system.The soil layers could be classified successfully by thefi¥'e layers, i) the soft clay ground, ii) the alternatemixture layer of sand and clay, iii) the bearing layer withN-values of about 50, i¥') the bearing layer clay ¥vithN-value ¥vith more than 50 containing partially cla}.', v)the continuously very strong bearing layer with N-valuetude to Mr. T. Nisioka at Kiso-.Jiban Consultants Co.,Ltd. and Prof. K. Shiono at the Osaka City Universityof more than 50.for their' helpful dlscussions.Furthermore, the soil layers are classified very clearlyon the axis of the connecting bridge, although there wereACKNOWLEDGEMF.NTSFinally. , the authors would like to show sincere grati- 139N鷺W RUNWAYAτHANEDAAIRPORT6） Tanaka， 猶・1、， Sakajo，S，and N三sむioka，T、（2004a）：A study onREFERENCES ra芝ional stratum estinlation usi鷺g soH database，39’h！1111r、Co1∼ゾニ1）Cressie（1993）：S∫α”5！’c5∫orSρα1’α1P徽，Wiley． ／G8（Niigala），181−182（lnJapanese）、2）Researc短Ins【imte of Civil…三ngineeri鷺g，Tokyo Govemme撚，Tokyo7） Tanaka， ！y董．， Sakajo， S、 ＆nd Nish玉oka， 丁，（2004b）： 3D Sにa￡ロm （districエ） （1996）：The deep underground geolog｝・， 710勘vo （3ε0109’（♪ εstlma［ion System Using So旦Da【abase，Cα∫θκ醜01二y qブU1カα’∼ ！VαρCo〃εご’io／1，（6）（in Japanese）、3） Sakajo，S，（2005）：New technolo9玉es fQr so員investigatio鷺s，P”oc、 Gθo−／’401F’ηα”c5，澱rC10Thailand，presented as an exこra paper．8）Tanaka，レ1．，Sakajo，S、，Nis短Qka，丁、and Sakai，τ．（2005）：A study 71θ6ノ∼∼泌θ1P／25θ〃1〃110n，／ノ1！、Co∼∼∫0θo！召納．zシ∼9！8．，Osaka，Japan． of creation of rational2D design cross sectio良in tlle mou撚ainous4） Shiono，K，，λ｛asumoto，S、，Sakamoto，∼1、and Yao，A，（2000）： areabasedo捻3Dgroundvisuallzationsysτem，40∫13・4肌Coπ≠ノG5 Geological sarvey and Ioglc of geologic map，Computer processing （Hakodate），31−32（in、lapanese）． anditsproblem，1吻〃∼顧o∼1Gθ010＆｝，，玉1（4），241−252（ln9）Watabe，Y．andTanaka，M、（2004）：Geotechnicaldatabaseforpor｛ Japanese）． and airport consζructlon ln Japan，Cα5θHi甜oぴo∫Uめα’∼θθo−5） Tanaka，∼1、，Sakajo，S，and Nis赴ioka，T．（2002）：S芝udy on use ofsoiI 1顧oηn如c3，パTα0，Thailand，72−83， da℃abase，57∼hパn1π∼α1／C五S，3，681−682（in Japanese）， | ||||
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| タイトル | Failure of Reinforced Earth as Attacked by Typhoon No.23 in 2004 | ||||
| 著者 | satoru Shibuya・Takayuki Kawaguchi・J. Chae | ||||
| 出版 | soils and Foundations | ||||
| ページ | 153〜160 | 発行 | 2007/02/15 | 文書ID | 20987 |
| 内容 | 表示 R !'.SOILS AND FOUi¥'DATIONS¥rol47 ,Nol, 153l60, Feb 2007Japanese Geoiechnical SocielyFAILURE OF REINFORCED EARTH AS ATTACKEDBY TYPHOON NO. 23 IN 2004SATORU SHIBUYAi), TAKAvU}(1 KA¥¥*AGUcHlii) and JONGGIL CHAEiii)ABSTRACTIn October 2004, Typhoon No. '_3 attacked western part of Japan, causing severe damage to infrastructures over a¥vide ar'ea in Kansai. In the early morning on 2lst October, failure of a large Reinforced Earth lvall with the maximumheight of about 23 m took place in a mountainous area in Yabu city, Hyogo Prcfecture. The debris flo¥v from ther'einforced embankment attacked a ¥varehouse at the foot of the mountain, however, no casualties ¥vere reported.Immediately after the incident, an investigation committee ¥vas set up vith missions to investigate the causes of thiscatastrophic embankment failure and also to examine any possible occm'rence of' further slope disasters in this region.In this paper, the failure mechanism by considerin*' causes of the slope failure is discussed based on the results 0stability analysis performed using laboratory and field data, coupled ¥vith topological information and the rainfalldata. Some lessons learnt from this unique case study ar'e described ¥vith reference to the design and construction ofReinforced Earth wall in rainy mountainous ar'eas, in particular.Key words: design, in-situ test, Iaboratory test, Reinforced Earth, shear strength, slope disaster (IGC: B5/BI I /C*,3/D6/E6/H6)INTRODUCTIONThe design and construction manual of ReinforcedEarth Arm6e wall does not consider any ¥vater in andWa i*¥.adjacent to the reinforced soil. Similar'ly, Iittle attentionis paid to infiltration of rainfall ¥vater' from the surround-'; +･･}ing area. Nevertheless, the Reinforced Earth using metalstrips has been popular in use for constructing local roadsin mountainous area in Japan, ¥vhere the attack ofseasonal hea¥'y rainfalls is commonly encountered.Moreover, ¥vhen considering the need for reducing theconstruction cost, Iocal government is often obliged touse local soils ¥vith lo¥v permeability and low frictionFig. l.angle in constr'ucting Reinforced Earth ¥vall. Despite thatthe stability of reinforced ¥valls is usually threatened byrainfalls (e.g., see Kutara et al. , 1991), a proper drainagesystern around the wall tends to be optional, not obligatory, in the light of the current format of the desi**n andYabu city in northern part of Hyogo Prefecture in westJapan. The time of occurrence of the incident ¥vas quiteexact by the record of an emergency phone call from a10cal resident to Yabu local government office. Figure 1construction manual for this type of wall. Geotechnicalengineers have therefore been concerned with the shortterm stability of Reinforced Earth in the event of annualtyphoon attacks as they are constructed in a mountainousregion. Unfortunately, such a worry became a reality inshows a picture of the ¥vall failure that was taken a fe¥vmonths after the incident.The urgent matter that after required attention vas toensure short-term safety of neighborin*･ inhabitantsagainst occurrence of any further slope disasters.Accordingly, under the authority of Yabu city govern-the case study described in this paper.At around 1:40 am on 2lst of October' 2004, a hugelandslide involved vith a catastrophic failure of Reinforced Earth vall took place in the mountainous area ofi,ii)iii)Site after the collapse of Reinforced Earth wallrnent, comprehensive geotechnical site investigation ¥vascarried out over six-month period after the incident.Professor, Department of Architecture and C ivil Engineerin_ , Kobe University, Japan (sshibuya@kobe-u.ac jp).Associate Proftssor, Department of Civil Engineering, Hakodate National College of Technology, Japan.Gradua e Student, Graduate School of Natural Science, Kobe University.The manuscript for this paper ¥vas received for revie v oll May 9, 2006; appro¥'ed on N. ovember 17, 2006Written discussions on this paper should be submitted before September l, 2007 to the Japanese Geotechnical Society 4-38-2, Sengoku,Bunk.vo-ku, Tokyo I l'_-OOI 1, Japan. Upon request the closing date may be extended one momh.153 SHIBUYA ETl 54*+' ' - " )i' +*'"' rE;li Tl,] i [ l 0:. 'KOU ou ' "*'/ ::*= '+oo 20Cf' ': 1: ('"__50 oAL .::It::::' _ L: r ; :: : l- :;in---- awa-' -vvsar:ver -_ "'' 'Fi(g. 3.Cross section of the remainder of the lvallFig. 2. Topographica] map of tlle site immediatel¥. after the incidentSeveral key observations from comprehensive surveyper'formed immediately after the incident (Shibuya andIn addition, in an attempt to back-analyz,e properly theKa¥vaguchi, '_006) are:i)Parts of the ¥vall (i.e., concr'ete skins and metalstrips) reached to the end of debris flo¥v,stability of the collapsed ¥vall, a series of direct shear boxtests in simulating the mode of undrained shear of theii)foundation soil was carried out in the GeotechnicalEngineerin_2: Laboratory at Kobe University.In this paper, based on the results of geotechnical siteinvestigation, key factors responsible for the ¥vall collapse are manifested, and the scenario of the ¥vall failureis discussed in depth by performing a conventional stabil-iii)ity analysis ¥vith detailed soil profile and the stren*'th dataV)of the local soil.iv)Neither dama_,_"e of metal skins nor breakage ofmetal strip/concrete skin joints ¥1'as found,The remainder of the ¥¥'all stood in good shape,The metal strips remaining on the side ¥vall of ¥vallwere all inclined at an angle of 24-26 degrees fromthe horizontal that ¥vas equal to the supposed slipsurface an*"le on the foundation (Fig. 3), andRainfail ¥vater poured into the collapsed area duringrainfall.Regardin*' the remark iv), it lvas observed that theOUTLINF, OF THE WALL FAILIJREThe construction of the reinforced ¥vall ¥vas completedin the year of 2000, i.e., four years before the incident.Figure 2 sho¥vs a topographical map of the site sho¥vingthe condition immediately af'ter the failure of the vall.metal strips in the remained ¥vall aligned horizontally justlike the arrangement ¥vhen the ¥vall ¥vas constructed. Itshould be mentioned that the collapsed ¥vall ¥vas as highas 23 m. To the authors' best kno¥vledge, such a hu*"ecollapse as that of Reinforced Earth ¥vall has not beenreported in the liter'ature.The numbers shown in this figure refer to spots from¥vhere some pictures immediately after the incident weretaken in order to obtain any clues into the failuremechanism (Shibuya and Ka¥va_ uchi, '_006). The landslide took place over a length of about 150 m along theslope involved with the collapse of the vall over 80 mlength alon_ the road. It ¥vas obvious in the map that theslope over ¥vhich the wall failure occurred consisted of acouple of small valleys. Moreover, the road ¥vas inclinedabout 70/0 from West (right hand side in Fig )-) to East(1eft hand side in Fi_g:. 2). These topo*'raphical surround-RAINFALL RF,CORDAs mentioned earlier, the incident took place at 1:40am on 2lst October in 2004. Figure 4 sho¥vs the intensityof rainfall ¥vith time over three day. s befor'e and after theincident. It should be mentioned that the data ¥vasrecorded at an observatory ¥'ery close to the site. Heavyrain ¥vith the intensity in excess of 10 mm per hour con-tinued over eight hours (1 pm-8 pm) on 20th October.Note that the amount of 226 mm of rainfall ¥vas certainlyings ¥vould have brou*'ht about some concentration ofthe peak record over the past eight years in this region. Itsurface/_ round ¥vater into the collapsed portion of theroad durin*" the heavy rainfall.trig:9:er of the disaster.may ¥vell be postulated that this heavy rainfall ¥vas the 羅155FAILURE OF REINFORCED鷺ARTH塾ゆGξ ﹃ 蓬li纏護li髄際04110／19…1……馨筆顯ll， 照馨：コ？」『，一τ …尉：1竃菖 窯旧出［』甲．『9353界アo ） ℃ Φ↓…． i；，．li饒 ！liiiilii 罵瓢二5e3 のliU『 『p暁『9i 『iii難it の5G ① α、1鰭畷 t三1織隠1三諏嚢・η詰e，li鱒蕪葦04／10！2040 噂關『 ‘ ゆ訟 ］㊦P や〒門r讐酬 臼一Irr・叩■ r 71ε』甲liP， ：1：1：黙 ll……＝，2。3：：ll：設 甲 r卜乎昌一1 腰 甲』・…霞 臼 ・1eGヨ ロロコ の コTerre Arm6e Wali collapsed04110／21【01瓢，ili垂ii臨i臓にli湊揮匡搾 Grain size（mm）τ㎞εFines∈ンFig、6。Sa縞dGravelGra豆n size d韮str窪bu芝ion of so産夏α＝、． 、影コ奪．』』薦試葺誕ノ 轟1◇☆露Fig．4． R田ほfa畳l da瞼蜀＼ズ擁離爾 鐸糞謙藩毅鑛轟暴藩・灘1轡！購響罷響㌧』 ・萎鷲蒙蕎◎欝・ 匡嚢塾到Fig．7． Geo垂ecllnlcai si｛e韮nvesIigalion performedFig．5．CoロstrucIionseqロenceofthewa鍼er in order to secure prescr重bed friction between InetaIstrips an（nhe soiL As stated later， the soil stabilization●tyREINFORCED EARTH WALL COLLAPSEDtreatment has reduced the permeabiofiu−wallsoiltoaconsi〔ierable ex重ent． Figure 5 sho∼vs the sequence of cons重ruction of thiswa1正in the year of2000．Some features pertaining to thedesign and cons紅uction of芝he wa至1are su互nlnar三zed in theGEOTECHNICAL SITE INVESTIGATIONbelo∼v（Shibuya and Kawagucぬi，2006）：Soκ1π1in8i） Local geQmateri＆ls，1．e。，wea由eIled sllty so圭10rigi− The site is covered with heavily we撮hered soil origi− nate（i from yellow tu仔，with the丘nes con塗ent well innated from ye星10w tuff．Geotechnical site i煎vestigation excess of25％was employed for constructing theperforme（1is shown in Fig．7，The scheme consis塗ed of wal1，notillg that F圭9．6s紅ows t1｝e distribution curveSPT sou且ding and in−situ se圭smic survey to cover the of several samples from B21＆yer，survived as we至1as重he coilapsed portions of the wa1L Theii） Drain pipe with a small diameter of200mm wasSPT souuding a玉ong three survey lines from south to erllployed at t董1e bottom of the wa1正，but it did Ilotuorth involved with soll sampling by using the Japanese exten（i to cover an area behiIKI the、vall（5θθFig．5），thin−wall sampler．Spectrum aualysls of surface wavei圭i） The surface oぎthe road had been unpaved over the（SASW）（Stokoe et al．，1988）was＆lso carried out aξthe past four years，andsurvived parts of the∼v段n。iv） SPTノ〉一value隻n重he foundat重on ranged between15 and20，which was surprising星y low to supPor重the Crosssectionsoftkewalldepictedfromthesege− sollwallwith毛hemaximumheight of23m．Fig．8，the subsoils may be convenient至y characterized It should be meutiolled輩hat圭n the construction of thewal1，the IocαI soll was mixed with cement−based s宅abiliz一otechnic＆1investigations are showa in Fig．8．As seell lninto seve且layers as describe（I below： : F P's ' #SHIBIJYA ET AL.l 56a)E }EP }4e S EP NS 2ooeBP No 2L=15n20surf_'"' '-ilcer'** /(s3 /DL=140BF No 3!so= 'e JFd- _--*･,S･;;'ij;!2 i*II:;: i;;;Ge' s "I"rITT¥:_EP.1 ..- --- Y_# ;;1!!"YIT2 oi:4 oi ';::!{:{:::;:" "';SS"tB QOO 4a :le 200EOI*'2 fll DL='20 l"Z;,/'/.;:;;;::i;;:'::'_____4./-" ' ' '= '"i'':"'" '; //"' *' * /i ? / ･---///:'1i j!;{/;;:; ;t;::!;ji:':/"'1':; ;;;:! "i;lei " " """/ ; = ;;"'**S';*4* #^^i""i "_= ;"';;1"'TEs,# o ='s;o'2e oi2oo3PNOS - '"'* "*- 'N'v !u"f' #; - ; {)' 'j'*' :';' : ' "f"'-*-*'! "'*- 'o* **s o so oQ: '/' ;"" =:*._xp/"'Si=r ;'i"_";*;1'-_* .*_* .2eDKP-21I!so"; ;' ' ' ;;' ;"';';;i;';::;j L't5BP'No'4KP.3zs o 2s'o20KP's i b ): :e/:TS OEP F{O S1 iBP NS2;oo40Eo20 2 O 240 202 eo s o 400 4 o5 oDist r en tee 9iri)'Fig. 9.;";; '/' ""' '-Profile of shear wave velocit), from SASW* method ( 1'est side)iii) Foundation rock (W* -layer) ¥vith N>, 50.It is to be noted that the ¥vall rests on W*o-layer ¥vithN-value of 22 on avera9:e. It should also be mentionedC)BP'N0'7Q*' ' 'ls rfa :s' ! si r*/* e'!"* ' _1 ' l' ' #'' '#''/'( ; /';* B2 f '1 s't' '- : / '#x # ; ; ;i::( ;;!! ;; l;::;:';;:/ ! _';;:1;;;;:(;:!:! ;i!""'"i;t;';:: ;:;;' '1;;:i:;,: :;;!; ';/ ''_ /// ;'! W "W:/ _;iiSi;' ' 'i/#'e_ # ^i"!; ss##ss': i ;,,:'/;:''; :;1:IIll(: (1;;,:;::;1::!;:,: ' #; ;: i#$ $ '/ ;i'l:,::, .; ;;;j:(: :::;;::f i :" ;#s!/"'# i/i ; t'; ' ;" /''. f-#:;i"/ F**'-/'; ;"+**'+./- ' *'.'r -' ' :;' ;iiflli gre ;Fti /'e r''l*/on lit ¥vas smaller by one order of ma_g:nitude in the roadembankment (i.e., B1, B2 and B3 Iayers).!';;' ;LS ' 30m"":: ,!1:;;;;/'; ;i,!/'that the permeability from in-situ test ¥vas in the order of105 (m/s) for ¥veathered rock layer (W,o-Iayer), ¥vhereasDL* 2iPSpectrull7 A na!ysis of Sulface Wave (SA S W)SASW survey is a non-destructive method by ¥ 'hich theprofile of shear wave velocity, V*, ¥vith depth is easilymanifested down to the depth of about 20 m. Figure 9Q =tlOFT1Fig. 8. Cross section of the wall: a) Ivest line, b) central line and c) eastl inesho¥vs the result of the survey performed at west end ofthe remainin_g wall (see Fi_9:. 7). In this figure, the N-valueestimated using the following empirical expression is alsosho¥vn for comparison.Road E/7lbankl7lenti) Surface layer (B1-layer) with the SPT N-value rang-ing from I to il (N=5 on average), non-uniformand the fines content ran*'ed from 30 to 800/0,ii) Improved layer (B2-layer) with the SPT N-valueN= (V, /b)* (1)¥vhere the constants, a=0.314, b=97 (m/s) were employed (Imai et al., 1975).The follo¥vin*" may be noted:i)The shear ¥vave velocity, V , ranged from 150 mls to360 m/s as examined do¥vn to depth 20 m,ranging from 15 to 18 (N= 16 on average), relativelyuniform and the fines content ranged from 31 to460/0 ,ii)The profile of estimated N-value using Eq. (1) is simi-lar to the measurement, indicating that the N-valueof weathered r'ock (W*o-layer) is far less than 50iii) Behind the ¥vall layer (B3-layer) ¥vith the SPTN-value ranging from 2 to 5 (N=4 on aver'age),non-uniform and comprising *"ravel-size particlesThe efficacy of the SASW method ¥vas well demon-about 30-400/0 by lveight, andiv) Base layer (Fj-layer) with the SPT N-value averagestrated in this investigation that it provided 2-D picture ofN-value profile ¥vith depth, from ¥vhich the soil layeringof 17.Sulface Soi!lFouncJationi) Surface soil (D*-layer) ¥vith the SPT N-value rangingfrom 3 to 5 (N=4 on a¥'erage)ii) Weathered rock layer (W*o-layer) ¥vith the SPTN-value ranging from 5 to 50 (N=22 on average),t,hroughout the layer.shown in Fig. 8 ¥vas determined ¥vith reasonable confidence.I,abol'atoiy Sllear TestsTwo kinds of laboratory tests ¥vere performed in orderto obtain soil strength in use for back-analyzing the ¥vallfailure. In the first place, a ser'ies of unconsolidated-and a clear trend of N -¥'alue to increase ¥vith depth,undrained triaxial compression tests (i.e., triaxial UIJandtest) ¥vas carried out using intact samples fr'om different FAILURE OF REINFORCED EARTH157lable 1. Soil propertiesBulk DryDepth density densi .¥'GL-mp(g/cm3) (g/cm3)* PNatu,alSoilparticle¥vater ¥roiddensitycoment ratiop.(g /cm3)De ree ofsaturarione( ',S,(c)( 1O)55 _0-5 .7 1 .83 1 2 38.73798 . 5l .322107 l1 06495 ,, 97 .O8 .O I . 8 1 6 1 . 32 1 37.42 . 7272I .2050-2.6 1 .6342 .7 1 635.71261 77.6l .4683.03_7 1 .888 2.768 ･8 7 0.887 89 7O. 5 1 .723 l 2. 203.708 43 .2 1 .25 1 93 .5Table 2. Results of triaxial UU testBulk densiSoii layer p* (g/cm;)B2 and Fl.8Bl and B317Dt¥l .6181 r(TTotal stressc (kPa) c ( ' ) tan c;1;: Oirect46.3 7.77 0.136rive mator for horizont i !o68.0 o.0643,66, _f'l.T Load cell for ver ie ! Ioadirig* ' ,:Str in ampiifier08rd* "+.S :A/D board36.4 12.0S O.214Fig. 10. Direct(T cos- aNote that the soil samples from not only embankmentvas 46 kPa and 68 kPa for improvedlayer (B2) and unimproved layer (B3), respect.ively.Secondly, t¥vo series of constant-volume direct shear. 4;i;¥a10 shows the direct shear box apparatus developed atHokkaido Uni¥'ersity (Shibuya et al., 2001). The loadcontrol as well as data acquisition is fully automatedlear box apparatUS= 250h--'A(1 eosa sLnaW cos a: Crv COS2 aA!cosa' VH WIAwsinaAwco j f'I'lf""I w cosa//box tests ¥vere performed using reconstituted samplesretrieved from the slip surface. A block sample ¥vas firstprepared from the slurry with the initial ¥vater contentapproximately equal to liquid limit (i.e. , ,50600/0). Figure: petsen l oomputer7+.. L Linear rol{er waybut also the foundation were all close to full saturation.As a result, the angle of shear resistance c from triaxialUU test ¥vas small ¥vith the values less than 10 de*"rees., Load cell for hori2:ontai loading"4*.',: Qrive unit for vertieai ioadin' j,: Siiding uni41 .9 1 4.96 O.267:* : Shear hox('=9_. I Water containerin'-:)C*: Se aldepths. The results are sho¥vn in Table I and Table 2.The cohesion, c,ing2==: Qriv$ unit for herizont l lo ding'3,.*: Oirect drive motor for vertic l !oarW sinaA!cosa = (TV COSa sin aAFig. 11.Stress conditions a[ong the slip surface¥'it.han aid of PC. The nominal dimension of the specimenfor the long-term and short-term stability analysis,was 6 cm in diameter and 4 cm high. The gap between therespecti¥'ely. In the second series, in-situ stress conditionsupper and lo¥ver shear boxes ¥vas maintained at aon the collapsed slope were more closely sirnulated inconstant value of 0.5 mm during shear, noting the meandiameter of about 0.1 mm for the soil tested. The soileach sample by applying initial shear stress under draineddensity¥'as I .7-1 .8 g/cm3 bein*' very close to the in-situdensity.Regarding a sketch sho¥vn in Fig. 1 1, three samples inthe first se 'ies ¥¥'ere each consolidated to the verticalconsolidation stress, (T.* of about 200, 300 and 400 kPa,respectively. After'wards, the samples were sheared underconditions (refer to Fig. 11). In general, in-situ soilelement on a slope ¥vith angle ai from the horizontal issubjected to the initial stress conditions as sho¥vn in thef ollowin*";(Ti = (T.* cos2 ci = ((2), cos a sin a (3)constant-volume conditions by using a constant rate ofFigures 13 and 14 sho¥v the z'esults of five tests perforrnedhorizontal displacement of 2 mm/min. The undrainedin the second series. As can be seen in Fig. 13, eacheffective stress paths of this conventional consolidatedundrained (C*U) test are shown in Fig. 12, in which thesample was fir'st consolidated to a prescribed initial (andvariation of normal ( =verticai) effective stress is plottedstrength paramet.ers of (c' , c') = (O, 37.4'), together ¥vith25'), where the angle of 25' corresponds to the averagedangle of' the collapsed slope from the horizontal (seeFig. 3). The sample ¥ 'as then subjected to application oft.he tot.al stress parameters, S /(7.*=0.34drained initial shear to the ¥'alue of ti = 1 1 5 kPa ( = 300 xa*'ainst the horizontal shear stress, T. The effectivevere obtainedcommon) ¥'ertical stress of (7i=246 kPa (=300xcos2J SHIBUYA ET AL158I OOOOm inip' = 37.4'2003000minlOOmin200Ca)ip' = 37.4 'l Om inl m inl 1 5kPap)S" jOO*+.*' i; 100;.*Cl *l:19oo200I OOoo400300200l OO400300Normal stress. a(kPa)Norrna] stress, (7(kPa)Fig. 14. Undrained effective stress paths in direct shear box.' test vithb)en 200*c$ Le".'? 'ce)initiat sheaFlO.34!OO7300te209 kPac:s:':S OolOO 200300400 500b 200pNormal stress, (r(kPa)S*, = 4.88 In(t)+138 i"Pi('.12. Resu]ts of conventional direct shear test: a) effective stresspaths and b) undrained shear strength" 100I"4 _vears later i:)200Ol OoTim e.c:; 150:lOl Ot ( 111 i4Fio*. 15. Undratned shear strength versus duration of1 1 5kPainitialshearstress appliedJ"?) 100l 06)coristant shear stress":(3000min)* '50In itial shear i Reshearconsequence, the undrained shear strength S (i.e., themaximum shear stress) also increased ¥vith the sustainedperiod of initial shear stress. On the other hand, theI(constant stress) , (constant ¥'olume)oo,Horizontal disp lacement (mm )effective strength parameters of (c', c') = (O, 37.4') ¥1'erenot affected at all by the application of initial shear (referto Fi*･. 12). The significant softening behavior observed inthe second series suggests strongly that a catastrophicvith initial sheartype of failure ¥vould take place once the foundation soilexceeds the peak strength.Figure 15 sho¥ 's the S value in the second series whencos 25' sin 25') by using a slo¥ver rate of horizontal shearexamined against the sustained period of initial shear.Fig. 13. Relationship bet veen t]orizoutal shear stress and horizontaldisplacement in a testdisplacement of 0.0'_ mm/min. The initial shear stressBearing in mind that the ¥vall collapsed at 4 years after thewas then maintained constant over a prescr'ibed period ineach test. At this initial shear stage, the volume change ofthe sample ¥vas insignificant ¥vhereas the horizontal sheardisplacement developed as much as 0.2 mm (see Fi**. 13).construction, the value of 209 kPa for (T *=300 kPa,hence S./cr ,.=209/300=0.70, ¥vas attained by extrapolating the S ¥'alues from the laboratory test to aninstant after 4 years.The sample ¥vas finally sheared to failure under theconditions of constant volume by using a faster rate of2 mm/min. The initial shear stress was maintained overdifferent, but fixed, periods of 1, 10, 100, 3,000 andSCENF,RIO OF THF, WALL FAILURE10,000 min, respectively. Surprisingly, the effective stress_ :eotechnical investigation and comprehensive re¥'ie¥v ofpath ¥vas very much influenced by the duration of thedesign and constr'uction scheme of the ¥vall, itinitial shear stress application, showing that it rose moreconcluded that this particular ¥vall ¥vas properly designedand constructed in the light of the available "design andsharply as the duration increased (see Fig. 14). As aBased on the field observations, the results ofvas FAILURE OF REINFORCED EARTHsurface waterR=57.50m !embankment(Y=18kNlm3) Wslna W: Su:159surface was carried out by using the strength parametersfrom triaxial UU test and constant-volurne direct sheartest. Fi**ure 16 sho¥vs the short-term stability analysisperformed at the centr'al portion of the collapsed ¥vall(see Fig. 8(b)). The surface ¥¥'ater level ¥vas postulatedbased on in-situ measurement that ¥vas made immediatelyafter the incident. The results of back-analysis are sho¥vnin Fig. 17, in ¥vhich the back-calculated factor of safety,F*, is plotted against the total stress strength pararneter,S** IcT... Note that F, is close to unity (i.e., F, = I . 1) ¥vhenthe S. /(T.. ¥'alue of O.70 is employed, ¥vher'eas F= ¥vas farrock foundationFig. 16. Short･term stability a}lalysis,ldirect shear test is used for the calculation. The resultstrongly suggests that ¥ve should use soil strength fromdirect shear box test in vhich the magnitude as vell ashistory of initial stress conditions on the supposed slipsurface are closely simulated in the laboratory. In thestability analysis performed, it ¥vas assumed that the soilbehind the wall ¥vas saturated as a consequence of heavyrainfall over a short period of time. The effect of65 11,concentrated rainfall on the ¥vall stability ¥vas manifestedin the fact that the F* value ¥vith dry soil (i.e., S*=00/0)I.l) 08o 54 _104:o.7: o.34O O 2 O_6 O 8 lOO.4Su / C;:*Fig. 17. Back caiculated factor of safet .' Ivith S*/(T,*construction manual" (Ci¥'il Engineering ResearchCenter, 2003). However, it is the fact that the ¥vall faileddue to the heavy rainfall.Theless t.han unity ¥¥'hen S la., of 0.34 frorn con¥'entionalvall failure rnay be attributed to simultaneousoccurrence of sever'al, not a single, causes as listed belo¥v:i) C*oncentration of in-soil seepage and surface ¥¥'aterflo¥ ' into the collapsed area,ii) Relatively lo¥v permeability of embankment (BI , B2and B3 Iayers) as compared to the ¥veathered rockfoundation (W*o-layer) (see Fi**. 8),iii) Poor drain system behind the ¥vall in particular',iv) Lo¥¥' bearin*" capacity of the foundation, andv) Softening characteristic of the foundation soil assheared undrained (see Figs. 13 and 14).behind the wall ¥ 'as far greater than unity.Regarding the sketch sho vn in Fig. 18, the scenario ofthe ¥vall failure could be described as:i) A great deal of in-soil and surface water poured intothe collapsed area over a short period of time,ii) The ¥vater infiltrated into the embankment andgradually stored behind the v¥'all since thepermeability of the vall ¥vas relatively small,iii) Total load increased due to the ¥vater infiltration,i¥') Seepage lvater pressure in the ¥veathered rockf'oundation ha¥'ing relatively high permeability Increased gradually,¥') The overall stability of the embankment reducedsubstantially due to the vater storage in and behindthe ¥vall, together with possible development ofseepage pressure in the foundation soil,vi) The localized failure on the foot of the wall mayhave occurred due to the lack of' bearing capacity,andvii) A type of circular slip occurrcd across the foundation.The wall failure as such could be described simply as"the undrained shear failure of' foundation since the ¥vallacted as if a reservoir dam in the event of heavy rainfall" .It should be stressed that the first three possible causesFinally, it is strongly recommended that the design andconstruction manual should be revised properly so as tohave something to do with problems of in-soil seepageflow. As stated earlier, accordin*' to "design and con-prevent any future occur'rence of this type of failure. Thecase st.udy described in this paper also suggests the stron*'struction manual" in Japan like in other countriesneed for co-operation bet¥veen structural engineers andgeotechnical engineers.perhaps, any existence of water/water flo¥v is not considered at all in the design of the ¥vall. In fact, ho¥vever,rainfall water invaded the reinforced embankment in thiscase study. It was confirmed ¥vith the result of fieidobservation that the de*'ree of' saturation of the collapsedCONCLUSIONSThe Reinforced Earthvall that collapsed ¥vas properlyembankment soil ¥vas near'ly equai to 1000/0 ¥vhen ex-designed and constr'ucted in the light of "design andamined right after the incident.The short-term stability analysis assurning circular slipconstruction manual" in Japan. Unfortunately, it ¥'as afact that the wall failed during the hea¥'y rainfall as SHIBUYA ET AL.l 60Rainf i]l;:zi_.__Heavy rainfall by typhoani ' 7 7_v y'tf ;e' v1] hti: t::iff;i1(! Ll:Infiitratin of water from unpaved road ' l'//."'/' l"Embankment w th felatively-*S4- $4_# y:_; - .iow pe leability (i xi 0-7-5 mfs)Jl'.- Ctiff with TelativelyJl " ' - high Pe meability) /.____ ･"_ _ $_ y S'- - /'.'#;'.i'i^^- SSS(1xlO-5m/s)Cement-mixed soils/// ' Soil in embankment saturated/ '..";./;:>/ ; :/ i '(-$;?< ;''" ' ; {- )$ J/.･... ..*'"ri;Loss of bearing capaoity dueto seepage fiow/increaseof sustai'l t/' , ;;: :;' ';. !,;;;';;;''i. c:'.'*.(j:;*:*' ;i"-';' ""' :; ;' I r'; ' Instability of:;' ;"';_;'.;,' ';'. ';;'. "i;,;<,:,.';.! ' ',...", ";"'; "<,"'; ;,Block of. : 'ow to increasewate¥,,c!)SeepageFig. 18." embankment' // ;,'::{i :i '; j JCircular sliplevelof ground waterSeenario of the wa l fai!ureattacked by Typhoon No. 23 in October, '_004.Field obser¥'ations immediately after the incidentsimulated, and¥') Construction of this type of Reinforced Earth ¥vallcoupled ¥vith the result of the stability analysis corroborated the premise that the ¥vall itself stood in a good shapeneeds sound co-operation betlveen structural eng:ineer's and g:eotechnical en9:ineers.till the moment of the catastrophic failure. The ¥ 'allfallure in this case study could be described simply as"the undrained shear failure of foundation" since thewall acted as if a reservoir dam in the event of heavyrainfall. Simultaneous occurrence of several causes suchACKNOWLEDGEMENTas concentration of in-soil seepage and surface water fio¥vcity chaired by Professor Makoto Nishigaki, Okayamainto the collapsed area, Io¥v permeability of embankment, poor drain system behind the ¥vall, etc. ¥ver'esupposedly responsible for the failure. It is thereforerecommended that the design and construction manualshould be revised properly. so as to prevent any futureUniversity.occurrence of this type of failure induced by heavy rainfalls. In so doin*', every effort should be made to preventwater from seeping into and near the ¥vall.Other lessons learnt from this unique case study are:i) Drainage system should take care not only the ¥vallbut also the embankment behind the vall,ii) The wall should be placed on rock foundation lvithSPT N-value more than 50,Most of field data reported in this paper is referencedto the report issued by the technical committee of YabuREFERENCES1) Civil En_ineering Research Cen er (7-003): Desigll (z,Id Corl,structionMan!la! of Reinforcec! Soi! ,"t7!l !Vle[hod (in Japanese).2) Imai, T.. Roku. H^ and Yokota, K. (1975): Rela ionship bet veenshear ¥va¥'e velocity and mechanical properlies of Japanese soils,Proc- 5!/1 S.vn7p. Eartllqtrake Engineering (in Japanese).3) Kutara, K.,,fiki, H., Nakayama, K. and Fnjiki. H_ (1991):Beha¥*ior of prototype s eep slope embankment having soil-¥vallsreinf'orced by continuous fibers, J. Coilstruction IVlanagemen! (vrdEngineering. JSC_E, (4,_7, ¥rl-14), )_23-237_ (in Japancse)4) Shibuya, S , ¥. ,iitachi, T., Tanaka, H , Ka¥vaguchi, T. ar d Lee. I. h,J(2001): Measurement and application of quasi-elastic properties iniii) The surface ofthe road should be temporarily paved_ eotechnical site characterisation, Tllen7e Lecrure. Proc. Jlrh Asianeven in the course of construction by ¥vhich infiltra-Regiona! Conference on SMGE, Seolrl, Balkema, 2, 639-710.5) Shibuya, S, and Ka¥vaguchi, T. (2006): Lessons learnt from ation of surface ¥vater into the surroundings of thewall may be grossly lessened, andiv) In short-term stability analysis of the ¥vall involvin_",_cataslrophic failure of terre arm6e val due to heavy rainfall,Geomechanics II. Proc. Second Japa,1-U_S. ,Vorkshop 0,2 resting1lfoc!eling and Sinuda!ion in Geon7echanics, ASCE, Kyoto, 454-470the case of rainfall attacks, it is promisin_9: to employ6) Stokoe, K,, H , Nazarin, S., Rix, G. J., Sanchez-Salinero. I., Sheu,soil strength from direct shear box test, in ¥vhichthe ma_gnitude as ¥vell as history of initial stressconditions on the supposed slip surface are closelysoils by surface ¥vave method, Eallhquake Engineer'ing and Soi!D_ *namics II. Recen! Ac!vances !n Gr'ound !V[o!ion E1'a!uation,J. C. and ¥,Iok, Y. JASCE, 264-278.(19S8): In siru seismic testing of hard- o-sample | ||||
| ログイン | |||||
| タイトル | Design Parameters for EPS Geofoam | ||||
| 著者 | D. Negussey | ||||
| 出版 | soils and Foundations | ||||
| ページ | 161〜170 | 発行 | 2007/02/15 | 文書ID | 20988 |
| 内容 | 表示 SOiLS AND FOUi¥'DATIONS Vol47 .No1161-170, Feb_ 2007Japanese Geotechnical SocietyDESIGN PARAMETERS FOR EPS GEOFOAMD. NEG*USSEYi)ABSTRACTOver the past 30 years, design vith geofoam has been based on either factored strength or limit strain approaches.Geofoam parameters for design ha¥'e been derived from unconfined compression testing of small laboratory samples.Closer examination of performance observations indicate extrapolation of small sample laboratory results can lead tomisleading interpretation of field results. The potential for creep deformations is exagger'ated and design modulusvalues are underestirnated ¥vhen based on small sample laboratory tests. Possible reasons for these shortcomings, inreference to field observations, are examined on the basis of creep tests on small samples, uniaxial loading of' Iar*'esamples, comp*ession tests using tactile pr'essure sensors and revie¥v of enlarged images of geofoam surfaces. C reepdeformations in geofoams under uniaxial loadin_g: remain mainly in primary stages where strain rates continuallydecrease. Modulus values for design that are deri¥'ed from small sample laboratory tests are about half of the valuesthat ¥vere estimated from field observations. Accordingly, the sug:gestion is made to increase small sample basedmodulus values from laboratory tests for design applications.Key words: compression, creep, deformation, elastic,geo f 'o am ,modulus, polystyr'ene,strain, stress, tactile sensor(IGC: K14/M9)density geofoam is taken as 100 kPa to provide up to 30INTRODUCTIONkPa allowable stresses from surcharge loadings. Thisdesign method constitutes a factor'ed strength approachbased on correspondence bet veen density and strength.The first documented use of EPS (expanded polystyr'ene) geofoam as light¥veight fill occurred in Nor¥¥'ay overTo allo v for ¥veight increases due to moisture pick up inser¥'ice, design densities are increased to 50 and 100 kglm3 for installations expected to remain above and belo¥v,30 years a*"o. The reconstruction of the approach fill toFlom Bridge, near Oslo, is a significant milestone inlight¥veight embankment construction (Frydenlund,ground ¥vater, respectively. These density adjustmentsare adequate to compensate for ¥veight increases due tomoisture absorption under field conditions (Esch, 1995;Frydenlund and Aab e, 1996). For buoyancy considera-1987). The motivation for the application ¥vas to betterrespond to the cycle of settlernents and grade adjustmentsof a road¥vay supported on ver'y compressible soil foun-dation. The top surface of the geofoam fill was coveredtions, the actual 20 k**/m3 is used without adjustment orthe geofoam ¥veight is neglected. A friction coefficient of¥vith polyurethane spray and the overlying pavementstructure ¥vas only 0.5 m in thickness. Under estimateddaily traffic of some 15,000 vehicles, the road sectionperformed ¥vell and settlements0.5 has been assurned for geofoam to geofoam andgeofoam to soil or concrete interfaces. The practice ofpro¥'iding the equi¥'alent of two double sided timber¥'ere *'radually arrested.Geofoam blocks installed in 1972 ¥vere recovered andreused when the road¥vay ¥vas reconstructed by 1996.fasteners per block bet¥veen geofoam layers was introduced in Nor¥vay and has become ¥vide spread. Forpurposes of pavement design, a modulus of 5 MPa hasbeen assigned for geofoam subgrades. Actual modulusVisual inspection and laboratory testing of samples fromthe exhumed EPS blocks further confirmed the durabilityof **eofoam in service and under conditions of periodicflooding. The design approach developed in Nor¥vay forthis project and many more that follo¥ved continues toinfluence practice around the world. Mainly, the allowa-values from project specific tests have not been requiredfor' design or product qualification.In the rapid and innovati¥'e development of **eofoamapplications in Japan since 1985, a design process hasble surcharge load over geofoam fill is restricted to 300/0of the compressive st.rength at 50/0 Strain as determined bylaborat.ory testing of small size samples at a strain rate ofevolved ¥vherein stress at a limit lo/o strain has become aworking load criterion (Miki, 1996). The behavior' ofgeofoam belo¥v lo/o strain has been considered to belinear elastic. The design standard adapted in Japanprovides a 50 kPa allowable compression load for 20 kg/100/0 Per minute (Frydenlund and Aab e, 1996). Themost commonly used density variety has been 20 k**/nf.The nominal design strength at 50/0 strain for 20 kg/m3i' Director, Geofoam Research Center, s)*racuse Universit)*, Syracuse, NY 13244, USA (negussey@syr.edu).The manuscript for this paper ¥vas received for revie v on August 22. 2005; approved on August 29, 2006¥¥rriuen discussions orl: this paper should be submitted before September 1, '_007 to the Japanese Geo echnical Society,Bunkyo-ku, 'Tokyo I i?_-OOI l, Japan. Upon requesl the closing date may be extended one monih.1614 3 8 2 ,Sengoku, l 62NEGUSSEYm3 density *'eofoam and thus the same modulus of 5 MPa25Q .as ¥vas previously assumed in Nor¥vay. Allo¥vable stressesto a lo/o strain limit remain below half of the r'especti¥'e33 kg!m20ecompression strengths at 50/0 Strain. Ho¥vever, as thestresses under a limit strain criter'ia account for bothsurcharge and live loading, the t¥vo desi_9:n approachesIse -IQe -developed in Nor¥vay and subsequently in Japan arecomparable (Ne*'ussey and Sun, 1996). In the latter>50method, the essential correspondence is bet¥veen densityoand modulus. Modulus values of the order of 10 MPaand Poisson's ratios generally in the range of 0.1 andlo¥ver have been assumed in analy. ses for geofoam of20 kg/mi density (Hotta, 2001). A slightly higher frictiono264Vef eal Str in (810)Fig. 1. Unconfined compression of 50 mm geofoam cubes of 12 and33 kg/m3 densitiescoefficient of 0.6 has been in common use in Japan for>"eofoam to geofoam and geofoam to soil interfaces.Also, Iarger (150 by 150 mm) double-sided fasteners areused instead of the smaller (100 by 100 mm) size ty. pes2eo lstr3;r r B = 10earlier introduced in Nor¥vay. The design procedureintroduced in Japan enabled consideration of deforma-200 *iJfo*i 1Ts Isotion or perfor'mance cr'iteria.o'Shear demand at *･eofoam interfaces from live loadingdue to vehicle stopping and acceleration is lo¥v (Sheeley,yeQS Sx *3 04A: = O 9e1*･'** vBrtie 1 s: in5v eal st irly = 7 4o*x - 41sOYee1 st iT,3F " = O eS1> 50x * 21 52:o lO Q5lD1ostrengths, their use in practice is not common. Residualfriction coefficient values of 0.5 to 0.7 have so far beenhigher friction coefficients as compared to geotextiles andper1202000). Although statlc geofoam to geofoam interfaceshear stren9:ths are hi :her than residual interfaceadequate. Ho¥ 'ever, ¥vhy geofoam interfaces develop50 r m cvbe 5 mpies240 ls201025soss40Derl S ty {kOfTn:}Fig. 2. Strength gnin at 1, 5 and 1001!o strain levelsgeofoam densitylvith increasinggeomembranes is not vell understood. Althou'h reported to be unnecessary (Sheeley and Negusse}.', 2000),12 ldouble sided timber fasteners and similar proprietary10 JsPldevices continue to be installed bet¥veen geofoam layers.Capping of _"*,eofoam fills ¥vith concrete slab for loads:i*! i10s;6-distribution and protection continues to be a commonpractice. Apart from minor differences in sample sizesJi':(e*D *F te{}2]and shapes, design practices in other' countries generally.follo¥v the state of practice developed in Nor¥vay andO.Iapan. The aforementioned geofoam proper'ties havebeen used for different geotechnical applications (BASFPlastic.s, 1998; Negussey, 1997). Poisson's ratio valuesattributed to geofoams, the infiuence of confining pressures and effects of temperature on geofoam performancehave not been closely investigated. The latter propertiesand effects are generally not important for common near5'o1 S 20 2DBr s :･oTF.s'f *}Fig. 3. Modulus values for different densities of 50 mm cube samplesofeofoam100/0 strain levels and geofoam density are as sho¥vn insurface and belo¥v ground installations of geofoam.Geofoam desi**n parameters and behavior re*"ardin_*'stren*'ths and moduli ¥vith density as well as cr'eepphenomena are of more practical significance and areFig. 2. Differences bet¥veen strengths at 5 and 100/0 Strainconsidered herein.geofoam densities are sho¥vn in Fig. 3. The data fromdifferent sources are for 50 mm cube samples tested at100/0 strain per minute. These results indicate modulusUNCONFINED COMPRESSION AND DENSITYThe geofoam base material or resin price closely follo¥vs the trend of oil futures and the cost of EPS blocksincrease with density. For large volume applications therecan be considerable savin*'s from specifying a lowerdensity geofoam. As sho¥vn in Fig. 1, it is clear' that boththe strengths and moduli of geofoam increase ¥vithdensity. Relationships bet¥veen limit stresses at 1, 5 andare relatively minor and both the 5 and 100/0 straincriteria have been used in factored strength design procedures. Initial moduli to lo/o strain and ¥vith inc.reasingvalues for geofoam, as a function of density, determinedby testin*' specimens of the same nominal dimensions, atthe same strain rate are reasonably reproducible ¥vithin+ /- 100/0. Provided the manufacturing process andfusion quality are good, density is a consistent indexproperty for strength and modulus as desi**n parameters. DESIGN PARAN,1ETERS1631dsn5Tty = 20 h =meSO rE Tt c }c s nl9?kPaj Ya5tr* : 1+00? S1 -ol{Q¥j l ** S¥･ It23*-SeJ:,a {?Q* 29>e3s,a t Qof stf : s T5gP{70-C- 4g Pa {sG' - 23Pa {sQ*:*e LF a)- - S ,,pa (Se j2* -Gap irnsest ¥1_)1 E 3s 3 F? }C3CLfSSS¥ ' _LPC;O'stre:1 tn- tr;: ¥ 1 ,I , e : sL･+ in1 E*Qstr; n-05¥¥S;1:; prm3rys ¥¥¥¥1+:er'*=3ry* F-esOO.CeO-yeenYent 2*i x}n} C:fe P st { ; esF )7O eO1 o ol O I10 IQO IeQeO COOI O ODI O O1O1T 1TILrne (d ,s)F'ig. 4. Creep strain developments in three geofoam samples stdifferent stress levelsThe main rationale for limiting allowable static pres-10oO1 ee ySFig. 5. Creep strain ratcs for geofoam samples of 20 kg/m densityand t)pical creep stagesseoCREEP BEHAVIOR OF GEOFOAMiJsso Jn!en r 9c eompr ssones../30 4 k !m: (0=?s 2 n :TI H=s1 35 lscoosures to 300/0 of strength at 50/0 strain or total stresses to'I3eo l10/0 Iimit strain has been to minimize potential creepdeformations. The behavior of geofoam is assumed to beelastic and deformations to be tolerable for ¥vorkingstress levels consistent with these criteria. Figure 4presents results of creep tests frorn thr'ee 50 mm cubesamples of nominal 20 kg/m3 density geofoarn. Each testsample ¥vas subjected to almost 2 years of sustainedunconfined compression loading of '_9, 49 or 68 kPa.These load levels correspond to about 30, 50 and 70010 oft.he unconfined compression strength at 50/0 Strain forspecimens of the same nominal dimensions and density(Sheeley, 2000). Initial strain of 0.5, 0.8 and 1.50/0developed on application of' Ioading at the respectivestress levels. Additional deformation of about 0.5. 0.6and 200/0 developed over the 2 years of creep loadingperiod. The extent of creep deformation ¥vas especiallyacute for the higher loading at 700/0 of the unconfinedt250JJ "t'52e,1 l''IEtfils5JL/!150$:tt:l/leoooO 2SO10Vattic ! S:t40eOTo:n (Fig. 6. Unconfined compression loading and unloading of 30 kg/m3densitlgeofoamreduction in loading or stress intensity, secondary andeven ter'tiary stages can re¥'erse back to primary. Thecreep deformations of geofoam remained in primary ordecreasing strain rate mode for all loading levels even asaccumulated st.rains exceeded 100/0, as in the case f'or the700/0 Ioadin*'. Continually decreasing strain rat.es implystrain increments diminish ¥vith time. This is furthercompression strength. Both the 30 and 500/0 Ioadingsubst.antiated by results sho¥ 'n in Fig. 6 Ivhere, underconditions resulted in creep strains in addition to theunconfined compression, geofoam continues to stiffeninitial or immediate deformations. The results sug:,_*aestand gain strength ¥vith plastic strain instead of approach-geofoams develop both elastic and plastic strains under10ading to lo/o limit strain. For 700/0 Ioading or ¥vhatin*' rupture. On unloading and re-loadin*', the proportional limit increases lvith accurnulated strain. The resultswould amount to a stress state above the presumedsuggest controlled pre-stressing of **eofoam fill can beproportional limit, 50/0 strain developed in 3 days and upto 200/0 strain over 2 years of constant. Ioading. Such largebeneficial in reducin*' initial deformations vhile improving the allo¥vable working stress range. This observationcreep defor'mation observations encouraged the practiceof setting strict limitation on allowable ¥vorking stresslevels in geofoam design.is for a higher, 30kg/m3, density geofoarn and lo verdensity geofoams tend to develop softer' reloadingmodulus (Elragi, 2000) but continue to strain harden andthe test results sho¥vn in Fig. 4. Depending on the sustained load level, common materials deform in stages ofstiffen. The iaboratory test results suggest creep deformations occurred at all load sta*'es but will tend to eventuallycease without inducin_9: shear rupture, regardless of theprimary, secondary and tertiary creep to ultimateamount of accumulated strain (Negussey and Jahanan-rupture. In the primary stage, strain rates continue todecrease while in the secondary, the strain rates becomeconstant. With time, secondary creep can t.ransit to atertiary stage of increasing strain rates and ultimatedish, 1993; Elragi, 2000).Figure ,5 presents the creep strain rates associated ¥vithrupture. Reducing creep strain r'ates in the primary stageimply continuing stability as in one dimensional compression loading of soils. Secondary creep is a transition stage¥vhile tertiary is a precursor to ultimate instability. WithFIELD OBSERVATIONSField monitorin*' of high geofoam fills at the I-15reconstruction pr'oject in Salt Lake City (Negussey et al.,2001; Bartlett et al., 2001), the NRRL (Nor¥¥'egian RoadResearch Laboratory) test embankment and accom- NEC.USSEY164Ti lS [O;yS;a 2Qe 250 4Qe 4SO505e･Q *cJ'20 *-l OO- I e4..... , . _ :; 41$1S･･･Fe ,S ,rS!S .:S:i*1 Oe tr:1 : tieS !*20 '11 - FteSS fe eeit "sf:rSe T-30･140 -25 *,:1' f :_' / deS -- 10:> O30 -S50Q'Ps1 s', s20 *15 *ID *"e:er S$"I-Se -S . O *70$Q r･ t e;; se,Itc Q O 50O 25'(Negussey et al., 2001)teeO1 2s,5v rt:ee: Str- e -Fig. 7. Loadi rg and deformation of a large geofoam embankmenteo)Fig. 8. Geof0 m deformations f rom labresultandfieldobservation(Negusse¥.' et at., 2001)panying field monitoring (Frydenlund and Aabc e, 2001)indicate development of limited creep settlements. Figure7 presents data from the long-term monitor'ing progr'amat the 100 South Street crossing of the 1-15 project(Negussey and Stuedlein, 2003). T¥vo duplicate sensortaken after the 150 mm thickness concrete load distribution slab ¥vas poured but prior to placement of the I .2 mpavement section. As construction of the pavement overthe load distribution slab began, settlements due to gapsets of base pressure cell and extensometer column at 14m separation represent the Nor'th and South instrumentclosure bet¥veen *"eofoam block layers occurred. Thearrays. The pressure cells installed belo¥v the geofoam fillfield observations are associated ¥vith such gap closur'es.Whereas the typical initial lag of the stress-strain curveregistered the construction loadin*'. Deformations ¥vereinitial lag evident in the stress-strain results derived frommonitored with ma*"net extensometer plates iocatedfor the small size specimen under uniaxial compressionbetlveen the natural subgrade and the geofoam fill andbetween rigid metal platen is commonly attributed to nonuniform contact interfaces or seating error at the earlystages of loading. Beyond gap closure and seating erroreffects and as loadings pro*"ressed, the highest estimatesalso at different elevations bet¥veen geofoam block layers.The top three curves represent the loading history on thebasis of the t¥vo pressure cell readings and estimates fromthe record of surcharge placement over the geofoam fill.of tangent modulus from the field results are 11.6 andThe corresponding bottom two curves r'epresent settle-13.1 MPa compared to 4.1 MPa for the small sizedments of the geofoam fill at the respecti¥'e extensometerlaboratory test specimen. The dashed line in Fig. 8represents the average of the maximum secant modulusfor the t vo field curves of about 4 MPa. This secantpositions. The settlements are total deformations of 9and 9.5 Iayers of geofoam at the South and Nor'th arraylocations. The nominal thickness of each layer ¥vas 0.83m, so that the initial geofoam heights ¥vere about 7.5 mand 7.9 m at the South and North arrays, respectively.A Iarge part of the deformations re*'istered by themodulus value is closer to what normally is considered tobe the elastic modulus derived from corrected stressstrain data from laboratory tests on small size specimens.The trend of the field observations su*" est the tangentextensometers during construction ¥vere inferred to bemostly a result of **ap closure bet¥veen block layers(Negussey et al., ,_OO1; Stuedlein et al., 2004). Theinstalled geofoam blocks ¥vere not trimmed and tightdimensional tolerance criteria ¥vas not enforced. Postconstruction creep settlements, beyond approximatelymoduli, at stages beyond initial gap closure and for300 days, are minimal if not evident even thoughto transient loadings in post construction.assessin*･ incremental deformations and fati**ue life;should be at least twice the maximum modulus derivedfrom the laboratory testing of small specimens. Thehi*･her modulus values sug_ested by the field observationswould be more appropriate for evaiuating responses dueestimated and recorded stress levels exceeded 300/0 ofstrength at 50/0 str'ain for the nominal 20 kg/m3 densitygeof oam .SAMPLE SIZE F,FFF,CTSThe self ¥veight of the geofoam fill ¥vas negligible asPrevious studies of geofoam engineerin_g behavior bycompared to the surcharge pressure of the pavementDu kov (1997), Elra*'i et al. (2000), O'Brien (2001) alsosug_ :est a higher modulus and a linear range less thanthe normally assumed lo/o corrected strain limit. Furtherstructure. Estimates of applied pressures and pressure cellreadings at the base of the geofoam fill wer'e comparable.Figure 8 sho¥vs average stress strain relationships basedsmall strain modulus evaluation on the basis ofon the field observations presented in Fig. 7. Typicalresults from unconfined compression testin*" of a standard 50 mm cube sample of geofoam installed at 1-15 arecompression ¥vave velocities ¥vith bender element testsalso included in Fig. 8 for comparison. The curves for thefield results manifest an initial lag stage and stiffening¥vith further strain like the compression test behavior ofthe small siz,e test specimen. The base line readin*' for thethan the ¥videly accepted value of 5 MPa (as from resultsshown in Fig. 3) for 20 k**/m3 density geofoam. An alter-settlement monitorin_g: ¥vith extensometer arrays ¥vas(Sivathayalan et al., 2001) su_g:*"est upper bound estimatesof *･eofoam elastic moduli of 14 to 22 MPa and highernative approach for evaluating modulus from small beamdeflection testing also indicates higher modulus values(Anasthas, 2001). 165正）ESIGN PARAMETERSaDL弓aとnx糊戯n「冊 難冊鷲『㎜酬曽，r一雫 ▼ ▼■押酌窄r聖聖糊罵’『？【綴雫P概停… eo；灘＿一甲甲騰際篇爺…燕薫ト湾atnx Hεigh： 卜r、猟雛黛無澱淵＿．節＿＿陶一＿”曽 ”＿叩＿ 胃瓢算 甲”』諺篇”：爾 ＿“＿ΩolumR〉“曲隅綿；蹄拡器器襯闇”触‘甜甲甲，ぞ肺rr4 甲剛r障榊酌 F『お4D ＼ や、§3タ 一 2D 』 瀦繋』潔 一 loTab Row糊G 2 4 8 凌O 團 Coiロmn Sρ3qng Ve鵬aS児昌｛葵 一諏±眉㎜㎜Fl9。9．Uncon伽edcompresslo日of50a賎d600mmcubegeoεo甕m samplesFig，11． Det＆iis of謎tactile pressure sensor（謎dapted from Ieksc露r1， 2002）25一鉛現謂c睡狙s 血き ホあぬおる20一from Iaboratory tests on small size samples are too smaH篭15『and rather unrea正is宅ic to be used 圭n des量gn。 Beyondadjustnlents for seating error，the reason for the noted篇 10一sig且i負cant di仔erence玉n mo（玉ulus obta圭ned fronl sma王l ancl匿large sized samples was assumed to be due to end e錨ects． Conditions of uniformlty in both stress and（ieform＆一tlon cannot be imposed simukaneously at the interface ofo0 5 10 15 20 25 30 35 40 Densとylk9励Fl9．10．Geofoammoduluswi吐hde紅sit》一，sgmplessizeandest韮m郎e from6e鳳d observ鼠Iion（E塵r盆gi et訊L，2000）two materia圭s tぬat have cQntrasting sti登ness．In＆labora−tory test，the王oading Platens impose uniform deforma−tlon across the section area of test samples．Therefore，the s蓄ress non−uniforn1量ty at the relative星y rigid loadingplatell and Hexible but co勤esive geofoεしnl samPle was When compared to typical（iesign values associ飢edwith d醗ren嘘types ofsolls，5MP役is in a range normallyinferred topro（iuce h玉gherstressestoward theedgesi鍛themanner discussed by Taylor（1948）．This reasouing wasassumed for interpreting results of stacked samplesassoci＆tedwi由verysofttosof竜clays（Das，1998）．（Eh・＆gi et a1。，2000）where the average deformat玉on neαrWhereas the over10MP＆modulus implied by the且eldthe rigid Ioa（iing Platen was shown to be higher thandata indicates20kg／！n3density geofoaln compares betterdeformations across geofoam to geofoam interf＆ces．Aswith stifモer clays．Even when the｝1主gher unit cost can bea result of h圭gher edge stresses over tぬe top and bottonljusti且e（1，the apParent e（lulvalence of geofoam moduluseud faces of geofoam test samples，crushing and localto very soft to soft clay soまls cαn be ambiguous for prac−y量e1（i三ng were envisionedεしs like董y mechanisms for the lowtit1oners less familiar with prior geofo＆m applications．modulus an（1exaggerate（1creep deformatlon of small slzeFlgUre9preSentS reSUltS and COmpariSOn Of UnCOn且nedcompression tests on50aud600mm cube samples．Bothsαmples．With development of tactile pressure sensors，an altematlve means for sensing an（1investigation of亡he smα11an（i large size cube samplesαre of noml照1iuterf＆ce pressure distributions became poss量ble．15kg／m3density geofoam au（i were teste（1at10％perminute str＆in rate。However，｛he st正’ess strain curve for重he large sample is based on deformaξio茎1s measured over夏NTERfACE PRESSURE DISTRI8UT豆ON亡he midd圭e third of重he height and aw＆y from possible Tactile pressure sensors consist of tYvo Hexible sheetsedge e鉦ects at the lo＆ding Platen boundar圭es．The resultsshow the large sample based modulus can be double thateach containing thin conductlng strips over semi−con−ducting coated surface．Two sheets are mated to form＆for the slnall sa…11ple of the salne density．However，芝hevery thiu sandwich of semi−conductlng surf＆ce bet∼veenstrengths at either50r10％strain criteria are about thecon（iucting strips．In forlning the sandw重c｝1，the upPersame for both sample sizes．A slmllar di廷erence inInodu正us values over a range of densit量es was reported byand lower conducting strips are orien重ed orthogonally toform a grid pattem or ma芝rix of pressure sensing elemelltsElragi et＆L（2000）and ls shown in Fig．10．Also includedcalledsense歪s，Fig．n．Arowof44strlpsismatedwitむain Fig．10aτe the modulus estimates from負eld observa−tions and laboratory testing shown in Figs．3an（i8．τhecolumn of44strips to form a ma芝rix of1936sense至s．modulus of about10MPa for600mm cube sαmples ofand shapes c＆n be custom made．The spacing of theStandard sens量ng P段d sizes are avai正able aud specif崖c sizes20kg／m3density geofo＆m is in better agreement withconducting strips is varied to matc歴he deslre（i slze of themodu正us est呈mates from且eld observations，provicle（i gapsensing area．The semi−conductor Iayer be重ween theclosure e鉦ects are viewed separately．The星arger height ofcon（1ucting strips changes in resistance in response to600mm cube san1Ples is closer to the 重hickness ofcommon fu1正size EPS b三〇cks．八40（iulus values derivedapplied pressures．Reslstances measure（I at each gridpoint＆re highest when no external pressure exists．The NEGUSSEYl 66Table 1. Maximum, average and minimum pressuree O-70O -* festates at 1 ,locorrected strain in 25 clusters over the base platen and *eofoam'SliIIX:Itl!lllli;,;St :tiXlllAinterface: E,ach cltrster contains 64 senselsSQ - IllilllSl:lllltll8 sensels in each of columns A Io BSett30 - tt .'t .･'iO ' l:tle t.Itl'ilFa'$$2o*/er:$ = S:rBlr,)Fig. 12. Comparison of average pressures from a load celand tactilepressure seusors>oVconducting strips are protected by fiexible polyestersheets and connect to a handle. The handle connects to adata acquisition board in a computer via a cable. Theoverall sensor thickness can be less than a millimeter. Thethickness of the semi-conductin_g: Iayer controls the sensoroperating capacity, ¥vhich can vary from a lo v of O to 14kPa to a high of O to 175 MPa. Pressure sensor calibra-3e,ABC_153S61587)0829ll171617OOOOO23039O89248113237OMax 15557i 14177 432OOOAve 35Min O1 70,4vO1 2037O28O12034O6S20O23OD9821El 1433Ol 178172) )7 8OOO898920O77oe)19O20Otion studies indicate errors in accuracy to be less than 10to 200/0 depending on the pressure range. Sequentialscanning of the pressure field is displayed and stored inreal time. The average sensor output is calibrated againsta kno¥vn force or pressure to establish an adjustmentfactor. Force and pressure time histories of each sensingpoint can be further analyz,ed by exportin*' the data toother soft¥vare. The sensor manufacturer provides boththe hard¥vare and soft¥¥'are for the system. Tactile sensortechnolo*"y is about 25 years old and is now used in otherfields and industries (Paikowsky and Hajduk, 1997;Sodhi, 2001).re_g:ion follo¥ved by apparent yleld and plastic deforma-tion. The corrected modulus of about 2.5 MPa, strengthat 50/0 Strain of about 60 kPa indicated by results fromthe tactile sensors and also the load cell ar'e inood ag:ree-ment ¥vith corresponding values for' 15 k**/m3 nominaldensity geofoam, shown in Figs. '_ and 3. There is _ :oodcorrespondence and consistenc.y bet¥veen the stress straincurves and moduli derived from the record of tactilesensors and load cell obser¥'ations, as sho¥ 'n in Fig. 12.Individual sensel pressure states of the tactile sensorA 56 by 56 mm pressure sensing pad, Iike the onepads ¥vere captured and stored for further analyses andsho¥vn in Fi**. 1 1, ¥vas placed at the top and bottom of agraphic output. In play back mode, different stages of thetest ¥vere vie¥ved separately, frame by frame, to observe50 mm cube *'eofoam test specimen. There ¥vere 1936sensels over the full sensor pad. Pressure states at about1600 Iocations over each sample end surface contact areapressure distribution patterns over the geofoam testwere detected. Thus the area coverage per sensel wasapproximately 1.6 mnf. The tactile pressure pads had aseatmg error sta*'e, the applied load induced contactran'*._e of O to 250 kPa. Standard unconfined compressiontests at a strain rate of 100/0 Per minute ¥vere performedsample end areas. At the be*'inning of loading and in thepressure on only about half of the sample end areas. Withcontinued loading, the contact areas enlarged to the sizeof the sample end surface. A 3D representation ofon geofoam samples of 15k**/m3 nominal density.pressure patterns over the geofoam test specimen andPressure distributions bet¥veen g:eofoam to g:eofoam interfaces ¥vere also examined by testing t¥vo stacked 50 mmcube samples ¥vith tactile sensors placed in bet¥veen thesamples and also at the interface of the lo¥ver block andbase pedestal. A Ioad cell and a displacement transducerrecorded the applied vertical force and resulting deforma-base platen interface sho¥ved scattered spikes and loadfree sensels. A summary of pressure states for all senseltion synchronously.Figure 12 shows a plot of vertical stress against strainfor a geofoam sample based on data from the tactilesensors and the load cell output. The lo¥ver curvepositions, as in Fig. 1 1, at a corrected strain of lo/o anda¥'erage adjusted pressure of 25 kPa (at approximately20/0 Vertical strain in Fig. 12) is presented in Table I . Eachof columns A to E contains 8 sensel columns and each ofro¥vs I to 5 contains 8 sensel rows. Thus clusters IAthrough 5E each represent 64 sensels for a total of 1600potential load bearing sensels at the base platen andgeofoam mterface. Maximum, a¥'erage and minimum ofrepr'esents the unad.justed average output from the top64 sensel pressure states within each of the 25 clusters areand base tactile sensor pads. With ad.justment or calibration, the average stress strain curve for the tactile sensorspresented in Table I . Maximum pressures vary from '_30matched ¥vith the load cell based stress strain resultsreasonably ¥vell. All three curves sho¥v the characteristicsure states in all clusters, except 3B, exceed 60 kPa or thestren*'th of the geofoam at 50/0 strain. In several clusters,bedding error stage at initial loading, presumed elasticmaximum pressure states exceed twice the 60 kPa refer-to 57 kPa ¥vith an average of 110 kPa. Maximum pres- DESIGN PARAMETERS167'T'able 2. Contact pressure statcs at 1?/o corrected strain for 64 sensels2 e s: *of cluster 3C, the middle clustcr in Table lRo¥vHh ssColumn3 . 1 29 24 1 2 27 99O1736o98oo45oooi5oooo50:363 6 O 29 101 50 56 O3.7 21 32 3- O O38 O 80 363341O15e*; J'J3sQ3.3o 33o 60 29 o o41ili+f fC I C ' C 3 C.4 C.5 C.6 C 7 C 8O,!_ 2ee +o1 O 20OSO eso3070QiS 1'**iPereerit e cf Cen s: J feFig, 13. Sensei pressure states at I and 5,,corrected vertical strain fortactile sensors at top and bottom geofoam and loading piateuinterfaces89250 -33x,*!s, s:S e es:n! 3 s :sF:slFISs;feesl ISsse :} rn ,ee* at3ee･SlTeC$]5BitTxxx)ecXxxefTe s ) (xx20 )JL=iS,f ses,･!e xxxxxxXX'(e LeSti e : ce e(XXxx:･.e(xxXxxxence strength for setting an allo vable ¥vorking stress.Average pressure states in the same 25 clusters range fromiSO xXXxxXxXxx xx39 to 11 kPa ¥vith a mean of 25 kPa. The mean of thelee *.faverage pressures is the global average of all 1600 senselsand is equal to the a¥'erage pressure deri¥'ed from the loadcell record at lo/o corrected strain. The 25 kPa giobalaverage pressure at 10/0 corrected strain constitutes theallolvable ¥vorking stress for the test sample geofoamdensity. Ho¥vever, maximum pressures of up to one orderof magnitude higher than the allowable ¥vorking stressx ia,"Y･･F･ .. .IU,ll･1'1･I ll !uf･･8.81 9'ell'>SOx e..*e""""""'･f･･･"IF････'･"""'e$ee,Fee#$$x ...O tSt AdL*t4 G #A.-2VertiGa' SL 2 n (Fig. 14. Contact pressutes betwee 1 geofoamlgeofoam and geofoam/end platcn surfacesdeveloped at discrete positions over the end contact area.Initial contact and loadin*' started along the left edge ofdecreased in the manner evident in the long durationthe sample. The highest contact pressures continued todevelop on the left side as loading progressed but zeroconstant loading r'esults sho¥vn in Fig. 5. As local stressstates greater than yield began to develop at the earliestpressure states existed in all 25 clusters and at all stages ofstages of loading and co-existed ¥vith states of zeroloading and strain le¥'els. Pressure states for all 64 senselspressure throughout the test period, elastic and plasticconditions remained current at a loading interface at allof the center cluster 3C at lo/o corrected strain are shownin Table 2. Maximum, average and minimum pressuresfor' cluster 3C hvere 101 , '_1 and O kPa, respectively. Bothtimes.Figur'e 14 sho¥vs comparisons of pressure distributionsthe rnaximum and a¥'erage pressures of 101 and 21 kPawere below the mean of maximum and avera*'e pressuresof llO and ,_5 kPa for the 25 clusters. Over l/3 of thebet¥veen a geofoam/sensorlgeofoam interface and at ageofoam/sensor/base loading platen for a test on twostacked ,50 mm cube geofoam samples. The interface atsensels in cluster 3C vere under zero pressure ¥vhile about420/0 of the sensels ¥¥'ere at pressure states greater than thethe bottom tactile sensor pad was between the metal baseallo¥vable ¥vorking stress of 25 kPa. Approximately 6010tactile sensor pad lvas located at the geofoam to geofoamof the sensels in cluster 3C ¥vere at pressure states equal orinterface between the two samples. While the trend ofcontact pressures for the upper and lower sensor padsgreater than the *"eofoam stren*'th of 60 kPa at 5010corrected strain.plate and the lo¥ver geofoam block end area. The top¥'as sirnilar, t.he upper geof'oam to geofoam interface ex-Frames containing pressure states for all sensels atcorrected strain levels of I and 50/0 were extracted toperienced a lower maximum pressure profile. Maximumfurther review the pattern of stress distributions. Figurebe lo¥ver, if detected ¥vith a more flexible tactile sensor13 shows the percentile of the contact areas that weresubjected to differ'ent tactile pressures at the top andbottom of geofoam to rigid plate interfaces. At the lolopad to closely approximate a geofoam to geofoam interface. This is because the sensor acts to bridge voids toinhibit cushioning of small area stress concentrations.strain le¥'el, about 100/0 of the end areas ¥vere subjected toThe interlocking of intact cells and void spaces is a likelypressures at or above the average pressure associated with50/0 global strain. On the lo¥v side, up to 300/0 of the endareas were under zero pressure at lo/o strain. About 100/0cause for observed good interface strengths at geofoamto geofoam interfaces. Figure 14 also shows that peakpressure states exceeding levels correspondin_ : to thestrength at 50/0 corrected strain began to develop nearzero corrected strain and at initiation of loading. Suchof the end areas were at contact pressur'e states belo vyield when the global st.rain reached 50/0 . With yieldingcontact pressures between geofoam surfaces should evenand pressure redistribution in the vicinity of localhigh stresses tend to infiuence laboratory test results butmaximum pressure areas, creep rates would ha¥'ewould not develop to the same extent to significantly NEGUSSEY168* ' "" ;.' **.*SS*' ",'!,!' ."Fig. 15, Resin beads, pre-puffs and a cut surface ex'posure of ageofoam blockFig. 17. Magnified (X30) image of fused pre-puffs and void labyrinthsat a geofoam surfacepufi) void spaces are visible. For' the sensel dimensions ofthe tactile sensors that were used, about 8 sensels coverthe field of view (about X30ma*"nification) in Flg. 17.Some sensels ¥vould therefore cover fully or partially voidspace ¥vhile others would come in contact ¥vith pre-puffelements. Ho¥vever, at a cut surface, as in the backgroundof Fig. 15, most pre-puff units become cut. The voidspaces become exposed to atmospheric pressure and onoccasion intact pre-puffs remain undama*'ed at or verynear to the cut surface. The fe¥v sensels that came in fullcontact with undamaged pre-puffs ¥vere likely positions atFig. 16. Magnified (X600) image of pre-stFessed ce!Is in a pre-puffaffect field performance.CONTACT SURFACE DETAILSA photograph of resin beads (the feed stock for¥vhich maximum pressures developed. Ho¥vever, even at acut pre-puff, some gas cells ¥vere open ¥vhile othersremained intact. The image in Fig. 16 covers a portion ofa cut pre-puff from a sample that ¥vas previously loadedto 100/0 strain. Most of the cells ¥vere open and thecollapsed ¥¥'alls formed hexagonal configurations. Closedcells are evident at the south east corner of Fig. 16. Inmating cut geofoam to geofoam as opposed to _"_.eofoam*'eofoam production), pre-expanded beads or pre-puffto metal surfaces, the maximum tactile pressures attogether vith a small cut sample from a *'eofoam block issho¥vn in Fig. 15. The spherical resin beads, on the lowergeofoam interfaces ¥vould be lo¥ver and less susceptible tocreep. Within the interior of the geofoam mass, pressur'eleft, are generally 0.5 to I mm in diameter and containtiny impregnated **as bubbles, pentane, as a blo¥vin-'in the discontinuous voids can increase in response toloading and deformation of the fused pre-puff particles.a*･ent. The gas bubbies are contained in a polystyrenematrix. In the pre-expansion stage, the resin beads aresubjected to steam and pressure. The polystyrene matrixThe initially spherical pre-puff particles tend to acquir'esoftens to allo¥v the gas bubbles to expand in forming thepr'e-expanded beads or pre-puffs, on lo¥ver right, thatacquire diameters of 3 to 5 mm. The resin type and extentof pre-expansion *'enerally determine the density gradeof the geofoam block. As nei_g:hboring gas cells act tocontain the expansion of adjacent cells, the sphericalbubbles ¥vithin a resin bead acquire polyhedral shapes¥vithin the pre-puff, Fig. 16. The field of vie¥v in thisscanning electron microscope image (about X600magnification) covers an area of about O 05 mm2. Theindividual cell units ¥vithin a pre-puff are too small to bedetected in isolation by a sensel of about 1.6 mm2 ar'ea.The pre-expanded beads are poured in a mold and aresubjected to steam and pressure under all around confine-polyhedrai shapes ¥vith loading and deformation. As thenetwork of fused pre-puffs contains the trapped air in thelabyrinths, pressure increases ¥vithin the voids contributeto stiffening and more uniform internal pressure distribu-tion. Along the outer perimeter surface, voids betweenpre-puffs remain exposed to atmospheric pressure. As aresult, the portions of geofoam in the proximity of theouter boundary surface ¥vould tend to manifest morecompressible behavior. When spherical pre-puffs anddiscontinuous void spaces come in contact ¥vith loadin_-'platen, higher pressures begin to develop at the spher'econtacts like for individual grains in a granular matrix.Ho¥vever, vhereas granular particles can rearrange, thefused pre-puffs remain relatively immobile. L,oad shedding ¥vould tend to be restricted and the intact pre-puffsand cells ¥vithin sustain pressure. The maximum stressesment to form a geofoam block. On further expansion andregistered by the sensels refiect the combinations offusion ¥vhile in the mold, the pre-expanded beads or pre-relaxation, as the ¥vall of closed cells expand, changes inpuffs become immobilized in a matrix of discontinuousgas volume occur and interaction ¥vith adjoining cellscontinue. Void spaces and open cells occur across a cutair ¥'oids. This is sho¥vn in Flg. 17 where individual preexpanded beads have fused and inter-particle (inter pr'e-face and their influences on creep defor'mation beha¥'ior DESIGN PARA *IETFRS 169become exaggerated ¥vith decreasing sample height,paper. Chuck McWilliams of Tekscan, Inc. assistedlvlodulus ¥'alues determined by testing small samplestactile pressure sensor tests. Huntsman Chemicalrepresent significant underestimates of the beha¥'ior ofCorporation, the Federal High¥vay Administration-NYfull sized blocks.Di¥'ision, NY State Department of Transportation, UtahDepartment of Transportation and the Foam PolystyreneAlliance of the American Plastics Institute pr'o¥'idedCONCLUDING REMARKSWith 30 years of field experience and resear'ch, somevithresearch support. The author is indebted to all mentionedand others ¥vho helped.changes in determination and application of geofoamdesign parameters appear to be in or'der. Density is a_ ood index property for design parameters and classifica-tion of geofoam. Both strength and modulus of geofoamincrease ¥vith density. Field and laboratory results indi-cate modulus values determined by testing small sizelaborator'y samples can be increased. Thus for thecommon 20 kg/m3 density geofoarn and the generic design value most often used, a modulus of up to 10 rather 5MPa is more consistent with actual behavior of larg:eblocks. The mix of closed cells and ¥'oids over a geofoamsurface and associated variability of contact pressureintensities evident from tactile sensor observations alsopr'o¥'ide insight into friction coefficients for geofoam togeofoam sliding. The interface friction bet¥veen geofoamsurf'aces is higher than values for geomembr'anes becauseof the surface conditions. Creep concerns pr'e¥'iouslyidentified on the basis of laboratory tests on small samples ha¥'e not been evident to the same extent in fieldobservations. Even ¥vhere excessi¥'e deformations undersustained pressures occurred in laboratory tests, the creepstates remained in primary stage and dld not lead tor'upture or failure. Field obser'vations indicate seating andgap closure mo¥'ements mostly occur' during construction. Post construction total and differential settlementsof geofoarn fills ha¥'e gener'ally remained tolerable. Byincreasing the design modulus and with better understanding of creep behavior in geofoams, Io¥ver densityand less expensive grades of geofoam can be jusrified forsome applications. Alternatively, more intense static andtransient design loads can be supported ¥vith higher'density geofoams. The increase in modulus improves thecorrespondence of design estirnates and performanceobser'vations for dead load or sur'char'ge loading. Fortransient r'esponse, such as from tr'affic loading on rigidor' flexible pavement structures, the combined action ofthe load distr'ibution slab and the geofoam fill should beconsidered. Additional effort has been directed to examine alternative approaches of representing concreteslab and geofoam composite subgrades for pavementdesign.ACKNOWLEDGEMENTSThe author ackno vledges the contributions of formerand current gr'aduate students A. Elragi, N. Anasthas, X.Huang, M. Sheeley, S. Srirajan, A. Stuedlein and M. Sunvhose individual and collective work has been the basisfor this paper. R. Chave, G. Gresovic and J. Banasassisted ¥vith setting up test equipment and data acquisi-tion systerns. P. Ford helped vith preparation of theREFERENCESi) Anasthas. N (2001): Young's nloduius by bending lest and otherproperlies of EPS geofoam relaled to geotechnical applicarions,iV[asrer's Thesis, Syracuse Universi ¥'. Syracuse, NY,2) Bartlett, S , Farnswor h, C., Negussey, D. and Stuedlein, A(2001): Instrumentatlon and long-term monitoring of geofoamembankmems, -15 reconstruction project, Sait Lake C*ity. Utah,EPS Geofoam 2001 , 3rd Int. Coirf EPS Geofoafn, Sah Lake City,UT3) BASF Plastics (1998): S!.vropor Techilica! Information, Ludlvigshafen, (i ermany.4) Das, 'l. D. (1998): Principles o_f Fozmc!ation Engineering, 4thEdirion, P ¥;S Publishir.5) Du kov. N'I_ (1997): EPS as a llght-¥veigh sub-base material inpavement s ructures, P/i.D Tliesis, Delft Universily of Technology. Delft, the Netherlands6) Elragi. A F (2000): Selected engineering properties and applica-tions of EPS geofoam, Ph.D. Thesis, State University of Ne¥vYork, Syracuse. NY_7) Elragi, A. F., Negussey, N. and Kyanka, G. (2000): Sample sizeeffec s on the behavior of EPS geofoam. Proc. Sof! Ground T cllno!o*"_v Conf , ASCE Geotechnical Special Publication I 12, IheNetherlands8) Eriksson, L. and Trank, R. (199 ): Propenies ofE.xpanc!ec! Pol_vstyrene. Laborato,y E"¥periments, Swedish (3 eotechnical Institu e,Link6ping. S¥veden,9) Esch, D. C. (1995): Long-term evaluations of insulated roads andairfields in Alaska. T,'ansportation Research Recorcl ! ' o_ 1481,Transpor ation Research Board, 1¥;ashingtorl. D.C.lO) Frydenlund, T_ E (1987): Soft ground problems, outline of alternative solutions arrd the various applications of ex.'panded polystyreneas a light fill material in Nor¥vay, Vegc!irektoratet, Norwegian RoadResearch Laboratory, lvleddelelse 61 .11) Frydenlund, T. E. and Aabce, R(1996): Expanded poly-styrene-the light solution. Proc Inf. S_vmp- EPS CollstructionIVlethoc!, 'Tokyo, Japan12) Frydenlund. T. E. and Aaboe. R (2001): Long term performanceand durability of EPS as a light¥veight fil ing material, EPSGeofoain 2001, 3rd International Conference on EPS G eofoam,Salt Lake C ity. UT13) Ho ta, H (2001): Aseismic design of expanded poly-styrol fil inJapan. E'PS Geofoam 2001, 3rd Internationai C onference on FPSGeofoam. Sali Lake City. UT,14) i¥,Iiki, O . (1996): EPS construction method in Japan, Proc. Int.S_vinp. JEPS C*onstruction !V[etllod, 'Tokyo, Japan.15) Negussey, D. (1997): Proper!ies anc! App!ic'a!ioiis of Geofoain,Society of the Plastics industry, Inc., ¥Vashington, D_C.16) Negussey, D. and Jahanandish, "I. (1993): A comparison of someengineering properties of EPS to soils. Transporta!ion Researc'/1Recorc! No. 14J8. Transporta ion Research Board, ¥¥rashing on,D.C17) Negussey. D. and Stuedlein. A. (2003): G eofoam fill performancemonitoring, Report No. UT-03.17, Ulah Departmem of Transporation Research Division, Salt Lake Citv. UT.18) Negussey, D. and Sun, .¥,1. (i996): Reducing lateral pressure b)geofoam (EPS) substitution. Proc. In[ S_ 'inp EPS Construc!ion_, ifethoc!. Tokyo, Japan19) Negussey. D . Stuedlein, A , Barrletl. S. and Farns vorth. C , 170NEGUSSEY （2001）：Performance of a geofoam embankmem at王00south，董一1524）Siva由ayala鷺，S．，Negussey，D．and Vald，Y．P、（2001）l Simple reconstruclion projec【，Salt Lake C紅y，U置a無，だP3Gθoゾ10σ1η2001， shearandbenderelementtestlngofgeofoa磁，EPSGθoゾoαη12001， 3rd I臓ematlonal Conference on EPS Geofoam，Salt Lake C琵y， 3rd王瓢ematlonal Conference on EPS Geofoam，Sah Lake Clty， uT． uτ、20）0，Brien，A．S．（2001）＝葺PS be員avior dur玉ng static and cyc巨c25） Sodhi，D、S、（2001）：Crush圭ng faHure during玉ce−structure interac− Ioad1ngfromO、 05％stra圭ntofallure，EPSGθoゾoσ1π2001，3rd tlon，動gi17θε’甲’ngF1’αc’三〃ぞル伽17傭c5，68， Intemationa亙Conference o貴EPS Geofoam，Sak Lake Clty，U■．2玉）Palkowsky，S。G、andHajduk，E．L．（1997）：Calibraほonan（玉useof h玉story ofεhe use of geofoam for bridge apProac｝1負裏玉s，Proc，5’h gri曲asedtactilepressuresensorsingra凹iarma面al，Gθo鷹1∼、 加．Co11∫Cα5θ甜5’01ブθ5’11Gθo’θchη’cθ’E119’ノ1θθ吻9，NewYork， ル5r．／．，GT．∫ODJ，20（2）、 NY．22） Sheeley，費1、（2000）：Slope stab簸呈zation u樋1iz玉葺99eofoam，A∫o∬θ∼門y Thθ5Z∫，Syracuse Universlty，Syracuse，NY．26）S葛uedlein，A，，Negussey，D．andMathloudakis，M．（2004）IAcase27）Taylor，D。W．（1948）：F∼〃ゆ’ηθηfθ150∫So〃Mθごhαn’c5，Jo盤nWiley an（玉Sons，Inc、，New York，NY。23）Sheeley，M， andNegussey，N。（2000）＝A鳶inves葛igationofgeofoam28） Tekscan， Inc． （2002）：11πノ々5’がα1Sθη501’Cα’α109，Sou【益 Bosto鷺， 玉Pterface stre澱gth behavior，P1”o（：．50ゾγG1’oμπゴ7セch’70109y Coπノ〔， MA、 ASCE Geotecねn玉cal Spec1al Publication ll2，こhe Net簸erlands。 | ||||
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| タイトル | Initiation and Traveling Mechanisms of the May 2004 Landslide-Debris Flow at Bettou-dani of the Jinnosuke-Dani Landslide Haku-san Mountain, Japan | ||||
| 著者 | F. Wang・Kyoji Sassa | ||||
| 出版 | soils and Foundations | ||||
| ページ | 141〜152 | 発行 | 2007/02/15 | 文書ID | 20989 |
| 内容 | 表示 YSOILS AND FOUNDATIONS¥f ol47, Nol.141l52,F eb .2007Japanese Geotechnical Socie vINITIATION AND TRAVELING MECHANISMS OF THE MAY 2004LANDSLIDE-DEBRIS FLOW AT BETTOUDANI OF THEJINNOSUKE-DANI LANDSLIDE, HAKU-SANMOUNTAIN, JAPANFA ¥*U WANGi) and KYOJI SASSAi)ABSTRACTIn May 2004, a landslide occurred at the right flank of the Jinnosuke-dani landslide, and transfor'med into a debrisflow after fluidization. By analysis of the monitored video images of the debris flo¥v, field investigation on the sourcear'ea of the landslide, and a series of simulation tests ¥vith a rin_ :-shear apparatus on the initiation of the rainfallinduced landslide and its tra¥'eling process, the initiation and traveling mechanisms of the debris fio¥v traveling in thevalley were investigated. It is sho vn that concentrated ground¥vater flo¥v ¥vas the main reason for the landslideinitiation, and a rapid decrease of the mobilized shear resistance even under naturally drained condition caused therapid landslide motion. Durin*" the debris motion in the valley, high potential for grain-crushin*" of deposits inupstream and lo¥ver potential for the do¥vnstream deposits controlled the traveling and depositin*' processes of thedebris fiow. Different grain-crushing potential of the ¥'alley deposits played an important role in the debris flo¥vtra¥'eling and depositing processes.Key lvords: case study, fluidization, grain-crushing, ,: Oround¥vater, landslide, ring-shear test (IGC: D6)fINTRODUCTIONHaku-san Mountain is located at the boundary between Ishikawa Pr'efecture and Gifu Prefecture inHokuriku district, Japan (Fi**. 1). It is an active volcanoJapan Seawith a summit elevation of 2,703 m, and the ¥vholernountain is a national park. This park is famous for itsbeautiful scenery. About 50,000 mountain climbers visit*N 'r'¥¥"'_=' r¥^*this mountain in the period from 15 May to 15 OctoberTedori RiVer fr¥ Ka na wa!lrevery year'. Tedori River, the largest river in IshikawaPrefecture, originates in this area. The Jinnosuke-danilandslide (Fig. 2) is a giant landslide located on the'¥ I .,r. *Tedor idam(r_'r_ ?' ' _'"'vsouth vestern slope of Haku-san Mountain ("dani"Gifu"landslide designated as a "Landslide prevention area" byFig. 1.the "Japanese Landslide Prevention La¥v" in 1958.Meunta i nfi nnosuke lan i, 50 l 1 Iandslidec*!means valley or torrent in Japanese). It lvas also the first--;; :::.HakutsanFUku i ' * * - * -'/_"' !?vToyamaLocationmapof the Jinnosuke*dani landslideLandslides fr'equently occur in this area, and cornmonlytrigger debris fiows that tra¥'el long distances and damageproperties in the downstream valley of the Tedori River.right side is an active landslide, according to data obtained by rnonitoring, and is called the "Central RidgeIn the photograph of Fig. 2, t.he areas not covered byvegetation are local slope failures. For example, at theleft side of' the photograph, the main scarp and slidingBlock" of the Jmnosuke dam landslide (Frg. 3). The¥vidth and length of' this block are 500 rn and 2,000 mrespectively. Besides the "Central Ridge Block", thereare many other active landslide blocks in this area (Wangsurface of the Bettou-dani failure, which occurred in1934, is visible. In that event, a debris flow initiated by alandslide reached the Japan Sea after traveling for 7,_ km.et al., 2007). In Fig. 3, the blocks with arro¥v inside areThe upper part of the central ridge sand¥viched by thethe deformation of the Central Ridge Block, IocalBettou-dani at the left side and the Jinnosuke-dani at thelandslidesactive landslide blocks. In recent decades, accompanying'ith different volumes occurred at both bound-_ , Japan ( vangf¥v@landslide.dprl k}'oto-u,ac,jp).Research Centre on Landslides, Disaster Prevention Research Institute, Kyolo Universit}'The manuscript for this paper ¥vas received for revie v on lvlay 12, 2006; appro¥'ed on Nobember 17, ,-006.¥Vritten discussiorls on this paper should be submitted before September 1, 2007 to the Japanese Geotechnicai Sodet.v, 4-38-2, SengokuBunkyo-ku, Tokyo I l_7-001 1, Japan. Upon request the closing date rnay be extended one month.14i 142WANG AND SASS．A翁Fiα4． PhoIo o郵deb罫is rete凱io臓dams cons汀ucled ln the Jin鳳osuke・ danl、’＆lleydestroye（墨，and a loca玉road with a s量mple bridge utilizedfor debris−retention dam construction at the m量d（1至e ofBettou−dani was heavily（iamaged．Fortunate正y，nobodywas injured because there were not many mountainFig，2， Aeriai phoIog獄ph of the‘‘L聞薩s髄de Preven1董on Area”onlleclimbeτs passing through the vα11ey when the lan（i− Jin鶏os聴ke・｛韮ani Iandsl量de（Photo Cour吐esy of K謎癩段zawa Of罰ce ofslide一（iebris Row Qccurre（i．However，becαuse l＆n（1s正ides R韮vers段ndN飢io罰翫1｝｛ighways，MUT）with sim録ar behavior fre（1ue難t至y occur in this area，therisk for further 星an（islide and debris How activity still鰯．』蜜蓄歪㌻霧諺藁纂叢exists。As a national park，it should be absolutely safe forthe tourists．Even if some large Iandslides cannot becompletely stabi歪ized，understanding their potential risk，espec玉ally their motion behavior is a玉so very impoτtantfor disaster mitigation．Looking at the large parks ia themOUatainOUSareaSintぬewOrld，itlSeaSytO負ndaCOm−mon feature，th飢ls，steep topography with nice viewsoften has highτisk for landslide．This paper attempts toc1αrify the inltiation and trave1量ng mechanisms of theIandslide−debris flovv， aiming to supPly ins量ght for馨難難響難、察響 彦i馨馨藤麟 馨饗斐嚢∼ 際だ外♪、 ．驚』一至uturelandslidedisasterpreventioninsimilararea．GENEKAL CONDITIONS OF THE JINNOSUKE−DAM LANDSHDE ON｝｛AKU−SAN MOUNTAIN 丁紅e Haku−san Mountain area is characteτized by heavyprecipitation and由e Tedori River is characterized by itssteep gradient（Wang et aL，200410kuno et al．，2004）．InFig。3． Ac額ve kmds韮ide b置ocks in Ihe】遷謎ku冒s段睡mounI田臓area aroundIhe“Ce瞭alR韮dgeB皿ock”oヂ 1e Jinnosuke鼎da鳳i皿露ndslide（B段sedwinter，due to the s毛rong inHuence of monsoons fromSlberia，the accumulative snowfall may exceed12m ino臓 Kan段za、va O盤ce Qε Ri、rer and Natlon登1｝翌i毬h、、’段ys，MLIτ，the Haku−san Mountain area．In other seαsons，half of2004a）the days are rainy．For this reason，local annual averageprecipitatio鷺is3，295mm，about two times the nationaIaverage of1，700mm for Japan、In this area，snowmeltary valleys of the Central R．idge Block an（i causedgenerally begins in the middle of Maτc勤aad Bnisbes by〔iamage，althoug熱many countermeasure works熱avetむe end of May．互勲May2004when the landslidebeen imple搬ented in出is area for more than50ye＆rs．Figure4shows the debris retention dams constructed intive rainf段ll for three days be｛ore the歪an（isl量de occurredthe，linnosuke−dani valle》・．h May2004，a landslideoccurred at the upper part of the Bettou−danl from theOCCUrYed，SnOW melting WaS On−gOing，and the aCCllmUla−was216mm（F呈9．5）．It is also reasonable to consider thatt薮e effective water that infiltrated into the slope s封ould beCentral Ridge Block．This landslide was transfoτmed intomore than this value．Because the movement wasa debris How t勤at tra、7eled more嵐an2km after it slidrecoτded by a video camera of the Kanazawa O伍ce ofinto theBetto11−dani，A suspensionbridge was completelyRivers a熟d Natlonal Hlghways，Ministry of Land 2004 BETTOU-DANl LANDSLIDES-DEBRIS FLO Veo300:: 50250o: 40E:IlI 150! 30c:_(Q100>' 20:)Io Io50O o:1 ,900 m, and the elevation of the toe part of the depositof the debris flow caused by the landslide was about I ,2007sm. Figure 7 sho¥vs t¥vo aerial photographs taken beforec:cQthe event ((a): in the fall of 2003), and after the event ((b):e)on 24 May 2004, 7 days after the landslide-debris fiow),and the trace of the debris flo¥v with ele¥'ations at some)ce:!V<Voee ,e eo to ,O h hh143h hDateFig. 5. Hourl, rainfall before the landslide-debris flolv occurred(The rainfaH gnuge vas tocated at the ceutral ridge block ofJinnosuke-dani lantlslide, antl ,1'as measured b .' Kanaza va Officeof Rivers and National Highways, MLIT)key points (c). As shown in Fi**. 7(a), the source area is asteep cliff and there ¥vas no vegetation on the lo¥¥'ersegment of the landslide; ho¥vever, at the upper part, theslope is relatively gentle and is covered by vegetation. Formountain climber's, after leaving Bettou Deai, vhich hasfacilities such as parking areas, rest rooms, simplerestaurants, and a bus stop, most of the climbers have tocross the suspension bridge and access the Central RidgeBlock of the Jinnosuke-dani landslide to get to thesummit of Haku-san Mountain. At the middle of theBettou-dani, an access road for construction of debrisretention dams crosses the valley and enters the CentralRidge Block. As sho¥vn in Fi**. 7(b), both the roads andthe bridge ¥vere badly dama*'ed ¥vhen the debris fiow hitthem. The entire flowing process of the debris fiow lvasrecorded by a video camera (see Fig. 7(c) for the photo ofthe video camera set at the site), ¥vhich was set at anelevation of about I ,860 m for the purpose to monitor theFig. 6. Geologicai map of the area adjacent to the Jiunosuke-danilandslide (modified from Kaseno, 2003)important rivers, especially at the sites ¥vhich ha¥'e highInfrastructure and T'ransport, Japan (KORNH-MLIT)risk for landslide and debris flo¥v. The video cameramonitorin*" was conducted with a remote control system,and the ¥'ideo image can be r'evie¥ved in real time on the(2004b), the actual failure time ¥vas also exactly recorded,and the video image is very important for the study on theinternet. Because Bettou-dani is a valley ¥vith high potential for landslide and debris flow, it has been under con-motion mechanism of the landslide and debris flow.trol and rnonitored for 24 hours a day. Through analyz-As a part of the 1:50,000 geological map of theHaku-san mountainous area, a geological map of theJinnosuke-dani landslide and the nearby area wasing the recorded video images of this event, it is estirnatedHaku-san mountainous area is Lower Paleozoic Hidagnerss Overlymg this gnelss are Jurassic to Ear'lythat the velocity of the debris flo¥v may have reached amaximum of 20 m/s. As shown in Fig. 7(c), the relativeheight difference between the source area and the toe ofthe deposits of the debris flow (near No. 10 debris retention dam) ¥vas 700 m, and the horizontal travelin*" dis-Cretaceous sediments consisting of shaie, sandstone andtance was about 2,000 m. Based on these data, thecompleted by Kaseno (2001). The basal bedrock in theconglomerate, and lacustrine sediments kno¥vn as theTedori Forrnation. General descriptions of the geologycan be found in Kaseno (1993). Figure 6 sho vs thedistribution of strata in this area. Alter'nating layers ofapparent friction angle c. (defined as tan c. = H/L, IvhereH is the difference of elevation between head and toe of alandslide, and L is the horizontal distance from head totoe) of t.he debris flow is estimated to be 19.3 de*'rees.sandstone and shale of the Tedori Formation areFigure 8 shows the situation when the suspensiondistributed at the left side of the figure, and thebridge was completely destroyed. Large boulders 3-4 min diameter were transported and deposited near theCretaceous Nohi Rhyolites are distributed at the rightside. Both form the bedrock of this area. Volcanicdeposits, which erupted 100,000 years ago and 10,000years ago, overlie the strata of' the Tedori Formation andthe Nohi Rhyolites.THE MAY 2004 LANDSLIDE-DEBRIS FLOWAs mentioned earlier, the landslide occurred on 17 May2004 after conrinuous intense 'ainfall for two days. Theelevation of the source area of the landslide was abouts;debris fio v in the Bett.ou-dani valley by the KORNHMLIT (2004c). In Japan, under the leadership of theMinistry of Landslide, Infrastructure and Transport,monitorin*" video cameras are set at different parts ofbridge site. Some small debris vas deposited on the top ofthe left pillar' of the bridge, about 10 meters above thevalley bottom. This sho vs that even near the terminus ofthe debris flolv, the sliding potential ¥vas high andpowerful.Figure 9 sho¥vs a series of' continuous images takenfrorn the monitorin*' video of KORNH-MLIT. Thelocation of the video carnera was about 250 m downstream from the source area of the landslide. The time inseconds is shown at the top of each image. Fi**ure 9(a) ¥ rANG AND SASSA144s. ' Source j reiay. 2 004'i n' t"eTd- j!iide'lE]evation1 ,900 m*Beto" 1iIBet0-2_..,l,*{ S**"'*MonitoringVideo j* Si ;.:..-..,camera i;.i=',*; ;;;:{; Z{ Z,{'-Tota I iBeto-horizontal ;distance: i2,000 m iEleVation1 ,25,0 m-(-uspensi,onbridgBet1 O Deb isntion d mElevation1 ,200 m(a)(b)(c)Fi**. ?. The Mal ' 2004landslide-debns flo l 1 hrch occurred m theBettou dam from the Central RltigeBloek of theJlnnosuke dam landsllde (a)aerial photograph taken before the slope failure (in the falof 2003), (b) aerial photograph after the landslide (taken on 24 Ma)' 2004) and (c)trace of the debris fiow (Photos courtesy of th8 Kanazalva Office of Rivers and National Highlva .'s, MI.IT)there was fog goin*" alon*' ¥vith the sliding mass, indicating a hi**h traveling speed of the slidin*' mass. The secondwa¥'e ¥vas from (g) to (i), ¥vhich continued for 3 seconds.In this short period, a relatively. small sliding mass passedthe video very quickly. The third wave ¥vas from (i) to (s),which continued for 1 1 seconds. During this lon*' period,the slidin*' mass passing before the video ¥vas ver'y highand wide, indicating a large ¥'olume. As sho¥vn inFig. 9(s), an interrupt can be seen in the middle of theslidin*' mass. Actually, the flow of the slidin_ : mass shouldFia. 8. The suspension bridge that was completeh_' destro .'ed by thekeep continuous at the lo¥ver position of the valley (FromMa .' 2004 debris flow in the Bettou-dani (Plroto courtes .' of tl]ethe camera location, the bottom of the valley cannot beobserved). From 16:32:58 hrs, the dimension of the fio¥vbecame smaller, but sho¥ving a continuous flo¥v. For thisKanazawa Office of Rivers and ¥. *ationai Highways, Ml,IT)shows the situation just before the debris flow ar'rived.The vhite dotted lines in these ima'-es are the boundariesof the sliding mass in the Bettou-dani valley. The whitecolor in the images is snolv. The debris fiow passedthrou*'h the video from 16:32:37 hrs to 16:33:16hrs;reason, the fourth wave ¥vas defined from (/') to the end ofthe motion (at 16:33:16hrs), ¥vhich continued for 18seconds. The ima*"es after (x) ¥vere not presented herebecause the direction of the video camera ¥vas changed toobserve the situation of the upstream part. For all of thethus, the entire process continued for only 40 seconds infront of the video camera. By analysis of the video ima*'esima*'es includin*' the sliding mass, it is obvious that all ofsho¥vn in Fig. 9, the debris flo¥v can be di¥'ided into fourseparate ¥vaves. The first ¥vave vas from (b) to (g), ¥vhichcontinued for 7 seconds. As a frontier of the slidin_"_, mass,recognized in Figs. 9(d), 9(e), 9(r), 9(s) and 9(t), indicat-the debris included sno¥v, and muddy fog can being rapid motion durin_ : do¥vnstream tra¥'el.Figure 10 shows the situation at the source area of the "i2004 BHTTOU-DANI LANDSLIDES-DEBRIS FLO¥¥,FigF.1459. Continuous images of the May 2004 debris flow in the Bettou-tlani (Video courtesy of the Kanazawa Office of Rivers and NationalHrghwa,.Is, IMLII): Sliding mass is shown in white dotted iines: ¥Vllite color in thevhitc dotted lines is snowlandslide on 1 1 September 2005, more than one year afterwater flo¥v exited at W1, W2, and W3 at relatively hi**herthe landslide event. A man in the enlar'ged box can bepositions. On the other hand, at the lo ver part of L3,seen as a scale. According to the report of investigationthere ¥vere three ground¥vater exits ¥V4, W5 and W6.conducted soon after the event by KORNH-MLITThese groundwater exits ¥vere located in relative lower(2004b), the average slope angle was about 28 degrees,positions compared with W1, W2 and W3. It appearsand the average thickness of' the sliding mass ¥vasout into the valley. A cornmon phenomenon at the sourcethat the g:round¥vater level was different at the left andright parts, and the exits indicated the different ground¥vater veins. It is estimated that the phenomenon of thesliding mass in L3 not moving so far is due to the slidingmass at L3 being not fully saturated by the ground¥vaterflo v vhen the landslide occurred. This fact ensured thatthe debris, especially in the potential sliding zone, wasfully saturated and that high water pressure ¥vas suppliedto the back of the debris to make the slope unstable. Theground¥vater exiting at a high position at the head of theareas of these sliding blocks is that concentrated ground-debris ¥vas a major triggering factor for the landslideestimated as 30 m. In this figure, L1 , L,_, and L3 sho¥v therear boundaries of' three different sliding blocks, whichmoved for a limited distance from the rnain scarp;ho¥vever, most of these blocks did not move so far, butjust rested on the slope. At the middle block, bet¥veen L1and L3, most of the debris material slid out of the sourcear'ea, entered into the Bettou-dani, and joined the debrisflow. Also, at the lo¥ver part of' L2, most of the debris slid 2004 BETTOU-DANI LANDSLIDES-DEBRIS FLO¥¥*N1 " > 'l10Lead) .'Bet0-2 Bet0-3/:' ' 'ti hyt ' df 'f8OCQe)a)C(U6.- ,¥f ,,4 _fi,C::)l 47Beto-4(:a)Q)J:(a)2Toyoura silica sandCE/(Q/o'(/)l,2llllo 12 3 4 567Shear displacement (m)l1¥Fig. 14. Sample-height change with shear displacement duringI [] :'¥ /'f ete psrts Rots TsrtFig. 12. A half section of the sbear box and the close-up diagram ofthe edges (from Sassa et al., 2004a)constant-shear-speed dr _' ring-shear tests on samples Bet0-2Beto*3, Beto-4, and Toyoura silica sand: Normal stress =300 kPa,Shear vefocit) = 10.0 mm/s: The void ratios for the fouF samplesafter consolidation (before sl]earing) are 0.687, 0.760, 0.753 and0.901, respectivel)and is sensitive to pore-pressure monitoring, although themonitoring point is not at the center of the shear zone1 oo(Sassa et al., ,_004a).In this study, the rin_ : shear apparatus DPR1-5 wasemployed. The diameters of the outer ring and inner r'ingare 180 mm and 120 mrn, r'espectively. The sample, after) 80(!)>I*Q) 60placement in the shear box, had a donut shape with a:width of 30 mm. To avoid possible grain-size effects onthe shearing behavior, only grains ¥vith diameter smallerthan 4.75 rnm ¥vere included in the tested samples.Q)O)a 40C20ooi1ioGrain size (mm)Fig. 13. Grain-size distribution of soil samp!es taken from the sourcearea of the 2004 Iandslide and from the traveling path of the debrisflolvformation of the shear zone and the post-failure mobilityof high-speed landslides and observe the consequence ofmobilized shear resistance, as vell as the post-failureshear displacement and generated pore-water pressure(Sassa et al., 2004a). In this study, ring-shear tests wereconducted using ring-shear apparatus DPRI-5, Ivhich wasdeveloped by Sassa in 1996 (Sassa et al., 2003).One of the most important features in the developmentof the ring shear apparatus is the development of aneffective and durable pore-pressure monitoring system.To have a large inlet section and provide an averagepore-pressure value throughout the soil sample, porepressure transducers are connected to a gutter (4 x 4 mm)extending along the entire circumference of the inner vallof the outer ring in the upper box, as shown in Fig. 12.The gutter is located 2 mm above the shear surface and iscovered by t¥vo metal filters, ¥vith a filter cloth betweenthem. This system is quite durable in regard to shearingGRAIN-CRUSHING SUSCEPTIBILITY OF THEVALLEY DEPOSITS IN DIFFERENT PARTS OFTHE BETTOU-DANIIt is believed that the difference in grain-crushing sus-ceptibility should cause the difference in the travelingprocess of the landslide-debris flow. When the soil iseasy to be crushed, excess pore pressure ¥vill be easilygenerated durin*" the shearing process under rapid rnotion(means undrained condition), and in turn, the shearresistance will decrease and result in high mobility oflandslides. To check the grain-crushing susceptibility ofthe valley deposits, dry ring-shear' tests ¥vere conductedon the samples. The test conditions ¥vere: consolidate thesample at 300 kPa normal stress lvhich corresponds to theactual str'ess level of the landslide, and shear it underconstant speed of 10.0 mm/s until the shear displacementreaches 6.4m. For' comparison, Toyoura silica sand'hich is kno¥vn as a standard sandy soil that is difficult tocrush, ¥vas also sheared under the same test conditions.Figure 14 shows sample-height change during the dryr'ing-shear tests. Soil ¥vith high gr'ain-crushing susceptibi-lity generally has large sample-height change (contraction) during dry shear. The sample-hei_g:ht changes thatoccurred in the samples taken from Bett.ou-dani ¥verequite a bit larger than that of Toyour'a silica sand. ¥¥,ANG AND SASSA1481 oO(a)otted i le: ,before she ring80/'/se:id line: ;afiershearingo,5500CUJ*O!4.../'+"ll=/l '*>pore pre$sure (measured)e::0.350_*--ca,o40CQ$ _.././.,oQ)**･** Beto*3(DShear displ., ,21U)*CIS(1):50 1 oo 1 50 200 250 300 350 400o CDElapsed time (sec)400･ (b)Beto*4Residual failure lineoiGrain size (mm)CUCL:300Peak failure line2.70 33.7aa)(b)o(:oO(Uu)e)o) I200.-sta rtend TSP" 5(UooOEe)OBeto So olc:e)---= ･- h- Beto-2! ., /o**"'- Bet0-21 oo**･-･ Toyoura ss20 -15u,u)'-"- 8eto*4 ={$$s/ "/'.'Q)CL*･*･･ Toyoura ss/ .'::e)C:e)3C f200)c:cQa)4Shear resistance{60xPore pressure (appiied)300u)(t)ENorma! stre$s400e)/ "5(a)R101co(Da,ESP a=15.101 ooLllJ::(1)co)c IcO 1005c:(QO*200300 400 500Normai stress (kPa)300 (c)oToyourasil'esand8et0-2 Bet04endBeto-3semple sampie sampleF esidua tailure inexe) 200-Tested samples60033 7'oc:(UFig. 15. Grain crusl]ing occurred in the drl.' constant-shear-speed ringshcar tests on samples Bet0-2, Bet0-3. Bet0-4, and Toyoura si icasand: (a) Grain-size distribution of tlre tested samples before andt 100(Q(Dstart!:after shearing and (b) Marsal's grain crusl]ing susceptibtlit .･ Bp(defined b), Marsa , 1967)(1)oo I ooAmong the samples taken from Bettou-dani, Bet0-4 hasthe smallest sample-height change during shearing, sho¥vin,_,_a relatively lolver grain-crushing susceptibility.Figures 15(a) and 15(b) sho¥v the ,_._arain-size distribution200 400300Norrnal stress (kPa)500Fig. 16. Simulatiou test results of landslide iniriation tri( *gered b¥.rainfall under naturally drained condition: B )=0.96, Pore vaterpressure increasing rate = 0.5 kPa/s: (a) Time-series data, (b) Totalstress path (TSP) and pseudo effective stress path (ESP) and (c)Residual friction 2ngle of the tested soil sample Bet0-1 from theof the tested samples before and after shearing, and thegrain-crushing percentage Bp of all samples (Marsal,source area1967), respectively. Bp is the summation of the differenceof grain-size distribution at each sieve siz,e of the samplebefore and after dry shear (taken from shear zone), and itunit ¥veight of the slidin_g: mass, a avera_g:e ¥'alue of 18 kN/indicates the grain-crushing susceptibility of the soil. It ism3 was assumed in the test. Assuming the _"*,round¥vaterobvious that _ :rain-crushing susceptibility becomes lo¥vertable near the sliding surface, the initiai effective normalfrom the upstream part to the do¥vnstream part of theBettou-dani.stress ((To) and shear stress (ro) acting on the slidingsurface ¥vere 420 kPa and 224 kPa, respectively. Then,pore-water pressure acting on the element increased as theresult of rainfall and sno¥vmelt. The test ¥vas conductedunder the follo¥ving procedure:RING-SHEAR TESTS ON SOII, SAMPLES TAKENFROM THE SOIJRCF. AREAThe purpose of this test is to simulate the initiation ofthe landslide by vater pressure. The initial slope condition ¥vas simplified as bein*' 30 m in thickness (h) and 28degrees in slope angle (e). The landslide was triggered int,he ideal slope by rainfall and sno¥vmelt ¥vater. Throu_ghcT0=y*/1 cos2 e and r0=y*h cos e cos e, vhere, y* is the(1)Saturate the soil sample to a hi**h degr'ee of satura-tion with caTbon dioxide and de-aired water; it wasconfirmed that the BD Value (BD is a pore pressureparameter, related to the de*'ree of saturation in thedirect-shear state. It lvas propased by Sassa (1988))reached 0,96, sho 1'ing a high de_',_ree of saturation.(2)Consolidate the sample under normal stress of 420 ;.2004 BETTOU-DANI LANDSLIDES-DEBRIS FLO¥¥*kPa;149(a)(3) Apply the initial shear stress of '_'_4 kPagradually at41 .7 Pa/s to avoid pore-¥vater pressure generat.ion;!T d*fS:'/**' ;/;;･ i(x(4) Increase the pore-1vater pressure gradually at therate of 0.5 Pa/s through the upper drainage lineAalSlidingT Mass; "**WoFaDe r'sDe ositdirectly connecting to the upper surface of the sam-!,ople until failure occurs;(5) Measure the residual friction angle of the soil ¥vithconstant shear speed, ¥vhile increasing the normalstress gradually from a lo¥v stress le¥'el (about 90kPa) to a high stress level (about 400 kPa).Frgures 16(a) 16(b), and 16(c) present the test results.Figure 16(a) sho¥vs the time-series data for the ¥vhole testseries. From the beginning to nearly 200 sec, t.he normalstress and shear resistance were kept constant, vhile thepore pressur'e ¥vas increased gradually. From 200 sec toAAhlllCC _lllh=o(b)ACB cPAWO//BC=F<=Kd ' Aw330sec, srnail displacement occurred, and the shear'resistance mobilized a little bit higher, although the shear'stress lvas kept constant. The void ratio at 250 sec ¥vas0.350. After 330 sec, rapid f'ailur'e occurred, which can beconfirmed by the acceleration of the shear displacement.Corresponding to the rapidly increasing shear displacement, the shear resistance decreased rapidly to about I lO(,,c <; :?kPa. At that point, the apparent friction angle becamel jD/ :15.1 degrees, vhich is shown by the total stress path andeffective stress path in Fig. 16(b). The residual frictionangle of the soil ¥vas measured under complete drainedcondition as 33.7 degrees, ¥vhich is shown in Fig. 16(c),when the above test ¥vas finished. The procedure was toincrease the normal stress _ :radually (5.6Pa/s) fromabout 95 kPa to 405 kPa when keeping a constant shear4J:AecaNorrna stressFrg 17. Model for undrained loading of saturated deposits by adisplaced s:iding mass (Sassa et ai., 1997): (a) Illustration of themodel, (b) stress path of the torrent deposit during loading, a:angle of thrust bet veen the slope and the torrent bed, F : d,namicstress, kd: dynamic coefticient (Fd /A ;V)velocity. The shear velocity was set as slo¥v as 0.02 mm/szone. From the above test results, it is easy to calculateeffective stress state in the shear zone, because rhemeasured pore pressure is not directly from the shearthat the slope can remain stable at its initial slope angle ofzone. It ¥vas also affected by the supplied pore pressure.28 degrees, if there is no increase in pore pressure at theslidin_g: sur'face. In addition, from Fig. 16(b), it can beWhen pore pressure at shear zone is correctly measured,seen that the peak friction angle of the soil at initialfailure is much higher than 33.7 degrees.In Fi,.*,a. 16, there are some concepts that need to beresidual failure line. In the later part of this test, only theclarified. At first, naturally drained condition means thatin the test procedure drainage is not prevented and excesspore-water pressure can generate dependin_ : on materialThrough the above test aimin*" to simulate the failureprocess of a natural slope when the pore pressure actin*'to avoid excess pore pressure generation in the shearbehavior and loading rate, and it ¥¥'as referred to asnaturally drained conditions by Sassa et al. ('_004b).Under the naturally drained condition, it is easy to findout in Fig. 16(a), that there is a difference bet¥veen thepore pressure (applied) and pore pressure (measured).As sho¥vn in Fig. 12, t.he pore pressure transducer isconnected ¥vith the shear zone, also ¥vith the upperdrainage line through which pore pressure ¥vas supplied.When the pore pressure value from shear zone and upperdrainage line is different, the high value will be recoded bythe transducer. It is obvious that the high portion of thepore pressure (measured) was from shear zone. From thisdifference, it is estimated that high excess pore pressure_shear resistance should be replied on for data explanation.on the potential sliding surface was increased by theground¥vater table rise caused by heavy rainfail andsnowmelt, it is found that high excess pore pr'essure couldhave resulted, and in turn, the shear resistance of the soilat sliding surface could drop dol 'n rapidly. The resultantrapid drop-down of the shear resistance should causeacceleration of the landslide motion ¥vhen it moved downto the valley, and resulted in a high velocity lvhen itrushed into the valley.RING-SHEAR TESTS ON SOIL SAMPLES TAKENFROM THE LANDSLIDE TRAVEL PATH IN THEBETTOU-DAr '1was _ enerated in the rapid motion process after theThe above test simulated the initiation of rapid land-sample failure. Related to the above concept, the pseudoslide from natural slope. What lvill happen ¥vhen thefailed sliding mass rushed into the Bettou-dani valley,effective stress path (EPT) in Fi_ :. 16(b) is not the act.ualjthe effective stress path should move along peak or ¥VANG AND SASSA150Table l. Initial condrtion forundrained loadingon tl]evaile)' depositsfrom a rapid shding mass, Bettou-dani lands]ideho h**(m)(m)8 oorQas oo,,,,1;40ece)(deg.)Cl)Bet0-218)3lO30Bet0-318)3o7_oBet0-4))3o5(a)Normal stressShear stress20eoothe destroyed bridge; and Bet0-4 was taken below thesuspension bridge and near the toe of deposit of the800!(b)fr¥ N/1lf//V lLxFi**ure 17 is a model proposed by Sassa et al. (1997) todeposits by a rapidly sliding mass. The slidin*" massmoved do¥vn the slope (1), and applied load onto thetorrent deposits at the foot of the slope (II). Because asurface water stream or subsurface flow existed and someof the deposits ¥vere saturated, the torrent deposit ¥vas30,20E:r-¥': ¥ lNormal stressPoFe pressure:5u)u,a,400+1/510l'shear dispi1)E:rQu,(,) 200-Ce,Ea)V(U,:U):,lil,o 5 COe)Q)(1)Tesistance(1)o5 20o525oo30Elapsed time (sec){, (c) o: Ini al state1 oo L ESP TSP-- >; :1 ./ s!/ ... 2 6'2000+X*.l -f .･･" .-debris flo¥v.simulate the undrained-loading behavior of ¥'alley25Tirr}e (sec)e)* 500vhere thick torrent deposits ¥vere distributed? To simulate the landslide motion in the Bettou-dani, three other'samples (Bet0-2, Bet0-3, Bet0-4) from different parts ofthe Bettou-dani ¥vere sampled and used in rin_ -shear teststo show the fluidiz,ation process of the landslide (seeFig. 7(b)). Beto-2 was taken near the upper'most debrisretention dam in the Bettou-dani; Bet0-3 ¥vas taken near10 15 205(1)oo 600 700 80Dd oo200300400 500Norm 1 stress (kPa)Fig. 18. Simu]atton test results on sample Bet0-2 when sliding massrushed into the vallel_ and ioaded on the torrent deposits: (a)Applicd-stress signals (normal-stress and shear-stress increments),(b) Time-series data and (c) Effective stress path (ESP) and totalstress path (TSP), B =0.96sheared by undrained loadin*' and transported do vnstream together ¥vith the sliding mass (III). Here, acolumn ¥vith unit length of its sliding surface, ¥vhich is apart of the torrent deposit is assumed. In the position (1)of the sliding mass, the ¥vei**ht of the column (WO) ¥vas ineffect. When the sliding mass rode on to the torrentdeposit (II) ¥vith a certain velocity, it provided dynamicloading of the column. It is assumed that the appliedstress on the torrent deposits ¥vas the sum of the staticstress, W, (10ad due to the weight of the sliding mass) andthe dynamic (impact) stress, Fd, ¥vorking in the directionof motion of the sliding mass.At the Bettou-dani, the sliding mass moved down theslope (1), and applied a load to the valley deposits at thefoot of the slope (II). Because a surface-¥vater stream orsubsurface flo¥v existed and some of the deposits weresaturated, the valley deposit was sheared by undrainedloading and transported do¥vnstream together ¥vith thesliding mass (III) (Sassa et al., 2004a). The above testand Sassa et al. (2004a), it is reasonable for Kd to take avalue of unity. Then, the increment of normal stress andshear stress from the rapidly sliding mass to the depositscan be determined. The initial conditions for the threesampling points, ¥vhich were employ. ed in the rin*'-sheartests, are summarized in Table l. From the upstream todo¥vnstream, the slope angle ¥vas changed from 18de*'rees to 5 degrees near' the No. 10 debris retention dam.The initial thickness of the torrent deposits at the valley¥vas assumed to be the same value of 5 m, and the thickness of groundwater ¥vas assumed to be 3 m (ground¥vatertabie ¥vas 2 m below the torrent sur'face). The intrusionangle was assumed as 10 de*'rees for Bet0-2 sample nearthe source of the landslide from natural slope. It is thediff rence bet¥veen the slope angle of the initiated landslide and the slope angle of the valley bed.Arhen slidingoccurred at slope (1).To simulate the succeeding process, sample Beto-'- ¥1*asused to simulate the situation at slope (II), while samplesmass moved along the Bettou-dani valley, the intrusionangle became zero for Beto-3 and Bet0-4. Because of theeffect of the debris retention dam, the thickness of thesliding mass became thinner and thinner. Consideringthis phenomenon, the thickness of the sliding mass ¥vasBet0-3 and Bet0-4 were used to simulate the behavior atassumed to be 30m, 20 m and 5 m from upstream toslope (III), and the local slope an_ les of the valley at thedo¥vnstream.Figure 18 sho¥vs the results of the simulation test onsho¥vn in Fig. 16 corresponds to the landslide thatsampling points (Bet0-3 and Bet0-4) ¥vere considered.In Fig. 17, the valley deposit has a thickness of ho, aninitial slope an_gle of the valley g, and ground¥vaterthickness on the sliding surface /7, . The undrained10ading from a rapidly moving displaced landslide has athickness of A h, an intrusion angle of (x, and a dynamic(impact) coefficient of Kd. Based on Sassa et al. (1997)slope (II) using sample Bet0-2. Fi.･ure i8(a) sho¥vs theinput stress signals of normal stress and shear' stressbefore (0-5 sec), during (5l5 sec), and after the dynamicimpact process (15-30 sec). The signal ¥vas loaded on thesample under the undrained condition to simulate therapid loading of sliding mass on the torrent deposits, o）l）匙童9α隻9鼻轟ひ置）0 o 0躯ひωしノ1仁o）監oζω）亀o仁＞σ＞ぴ＞αo星9の口ごいooごご駆oΦω亘く吋①蹟7巽ヨヨ漏の聖9①σ帥一u。コ昌ヨ）ζ∫Q桝躍 竃 ヨの ㌦ → 謹． 7ゆハのΩ・誰，℃（窩o唱3弱器…：o轟帥諏ω聖→㌣虫尊肇①覧目鴇oビ ヨ 巴o①男器P（u弓釦ンずけロ鋤しウo → oooこ欝曽， oゑへけの（銭．o霞7野嵩に⇒ oo＝℃o鄭o鋤⊆L￠Lo） の鋤めドバ の の嵩塵仁 α §悪鐸 いしねの筥ヨぴQO Q弓の0り一の PG）の00り匂り旨。 図図O“｝0轡『q）ぐD I 匂り列 ロぐr鴇霞ε三 ε三”コ 僻ロリ（o 簾）篇♂羅蕗 ①臣uo 8§’星号 一零黛≦ （ωO＝匿 醐oリコo 臼nU噂嘉。諏 ”『 蕊 飴殺 唱臼請・守 くの・言 ①鶴一層 自o＝o写 嵩自o ”① 団一”o 角い『昌 雲露鴇さ＆言懇 o自謄昌ロハワ u羅ε≡i＝房 ゆ のや”三℃筥り のの撃蕪ハ の の怨ε魯富罫霧肩三i甥言巴包曽讐やあ ヨαQ囑 幽・跨【・σ灘題B緩号 ＝‘ro＝。 ハ ロゆ麟鎗 肇の＝’ 誰窺ど 鵠一唱浮 ののロけ 黛㌶覧守 ロしの ）彗ざo 閂鎚騒墾塁恥”顕再o「縛跨㌍ の この o薦ひコoo塁霧藝宅蕪騒箒：錯呂陀琶讐自・り房）三…．三竺欝 舅 りけ冨潟包霧PΩ‘r一く酔。・孚鼠o欝＿のQnりゆ ユロド儲Q岩πで（o器aδ蜂Noo 旧 o oΦ田ω猷鋤コ○でmω ゆ の6ヲ o oOi∋o里o9Φ ○ 『 ， ハ 富 りら 砿 → ω 自r ℃Shearresistance（kPa）oo㎝oo轟ZO訳貧8紹ωδ勉処∋8z9悼oo m の 刀 e’訴 r？・・1バ9 こン のS熱earresistance依Pa〉 一▲ 卜oOo ぐつ轟 し跨のの＃ヨZσo oShear dis診lacemenセ（★肇0”3m） ロ の こン の 8占o 一ム ヘ｝ ω σ肇1N一） lω沁1⑩OIO ｝ヨ1α例Φ一』1i“） 、て｝ 1ω父1o oへ》 ω … … …の ロ ロ oゆo8涙8鐸3z一一〇1 房 刃 しo 「 ［ ○ ジお ① ［o ＿ o o ＞ z 戸 ＞ z o しり ［ ε S葉ress（KPa〉 団 の ε 8 8 1 ⊂：N 切o 順 → → ○ ω ① 0 ￠ Φ 0 0つ o料盆oΦ①8 岬 ω嘗 仁）z ① ヨ〔D“譲ヨ量 OSセress and pressure（kPa〉一 N Nさi㊤iのωωζ 堺 裟i＄hear displacement（rn〉9鋤ω串』 σ｝o o oかQ Stress（kPa） 劇奮① ω o』一 ゆ ＼ l o t zlゴ 婁1幕一 σコ o の の ロooo盤ωP①o（Dヨ瞬冨℃ωΦ晶Ω，qo I 曾1 −l I o o oo ロ くつ こンStress and蓼）ressure（kPa〉 N 4』』 σ》，．．翻 152¥¥,ANG AND SASSAFrom the above simulation tests that reproduced rapidJoint Research Programme of Disaster Preventionloadin_ : on valley deposits, the impact process, the travel-occurred in May 2004 ¥vere ¥vell reproduced in the labora-Research Institute (DPRI), Kyoto University are highlyappreciated. Dr. Huabin Wang, Mr. Ryuta Saito, lvlr.Jozef Jurko, and Mr. Taichi Minamitani of the Researchtory.Centr'e on Landslides (RCL), Disaster Preventioning process, and depositing process of the debris flo¥v thatCONCLUSIONSThe May 2004 Iandslide-debris fiow that occurred inthe Bettou-dani of the Jinnosuke-dani landslide, Haku-san Mountain, sho¥ved a fluidization process fromResear'ch Institute, Kyoto University, joined the samplingand field investigatlon.REFERENCESl) Kanaza¥va Office of Rivers and Natioual High¥vays. Ministry oflandslide to debris fio v. By analysis of the monitoredLand, Infrastructure and Transporvideo ima*"es of the debris flo¥v, field investigation of theRepol't on Jjnnosl!ke-Dani Larlds!ic!e (in ,Iapanese)source area of the landslide, and laboratory. ring-sheartests that simulated the rainfall tri**_ :ering mechanism andthe fiuidization mechanism during the process of do¥vnstream travel, the follo¥ving vere concluded:(1) Concentrated ground¥vater flo¥vs ¥vere a main tri**gering factor for the landslide initiation by increasing water pressure in the slope;(2) In the ring-shear simulation test of the landslideinitiation, it ¥vas shown that even under naturallydrained conditions, the mobilized shear resistance ofthe ¥veathered soil in the source area sho¥ved a rapiddecrease after landslide initiation, and this should bethe instinctive factor for rapid landslide motionafter its initiation;(3) In the ring-shear simulation test of dynamic loadingon the valley deposits, it ¥vas shown that hi_ghpotential for grain-crushing of upstream depositsand lo¥ver potential of the do¥vnstream depositscontrolled the traveling and depositing process ofthe debris flo¥v;(4) The shear resistance at steady state under undrainedconditions is the same for the soil samples takenfrom different parts of the valley (Sample Beto-2, 3,4). A possible reason is that although the initialgrain gradations of these samples differ at the initialstate, the soil at the shear z,one ¥vould become thesame ¥vhen the shearing process reached the steadystate, ¥vhen all of the possible grain-cr'ushing iscompleted.of Japan ('-004a): Investigation2) Kanazawa Office of Rivers and Nationa Highlvays, lvlinistry ofLand, Infrastructure and Transport of Japan (2004b): Debris o voccurred on 17 h,1ay 2004 in Bettou-clani, NeTt J!etter SaboHakusan, 6, l4 (in ,Japanese)3) Kanaza¥va Ofnce of Rivers and National Hi_ h¥vays, lvlinistry ofLand, Infrastructure and Transport of Japan (2004c):http: //)_1 O. 1 3 1 .8. 1 2/ - kanaza¥va/mb5kouhou lpress /ne¥vs .html.4) Kaseno. Y. (1993): Geo!ogica! .,Vfapping of Ishika va Ceo!og.)'Bu[lelin (in Japanese)^5) Kaseno, Y (2001): Suppleme,u ofCeo!ogica! Jt(Iappi,1g oflshikalt'aGeo!o*"_v Bu!!etin (in Japanese).6) h,Iarsal, R. J. (1967) Large scale tes in_'* of rockfill materials, ASC_EJ. Soil l ifecll. Fozlnd. Div., 93 (S.M?_), 27-43.7) O_ kuno, T., ¥Vang, F¥Vand ivlatsumoto, T. (2004): Thedef'orming characters of he Jinnosuke-dani lands ide in Haku-sanmountainous area, Japan, Lands!ides, Eva!uation & Stabi!ization(eds. by Lacerda, ¥V., Ehrlich, h,i , Fontoura S_, Sayao, A.), P,-oc^I_X InrS.}vnp. Lanc!s!ides, Rio de .Janeiro, 2, 127917_85^8) Sassa, K. (1988): CJeotechnical model for he motion of landslides,Specia! I,eclure of 5rll Inr. S;*mp. LancJs!ides, Landslides, l0-15July, 1, 37-55.9) Sassa, K., Fukuoka. H^ and ¥Van_g, F. ¥V. (1997): l¥,iechanism andrisk assessmem of landslide-triggered-debris fio¥vs: Lesson from the1996.12.6 Otari debris fio¥v disasler, Nagano, Japan, Lands!ideRisk Assessnle,It (eds by Cruden D. ,i., Fell R.), Proc. Int-Tfibrkshop oil Lands!ide Risk A,ssessmenr, Honolulu, 9-21February, 347356.IO) Sassa, K., ¥¥rang, G. and Fukuoka, H. (2003): Performin_ :undrained shear tests on saturated sands in a ne¥v intelligentype ofring-shear apparatus, Geolech. Test. J., ASTi¥,1, 26 (3), 257-265.ll) Sassa, K., Fukuoka, H., ¥Vang. Cj. and Ishikalva. N^ (2004a):Undrained dynamic-loadin_ : ring-shear apparatus and its application to landsiide dynamics. Landslides." J. Int. Consortium orl L(!nc!s!ides, 1(1), 7-19.17_) Sassa, K., ¥Vang, G , Fukuoka, H., ¥¥rang, F. ¥¥r , Ochiai. T.,Sugiyama, lvl, and Sekiguchi, T. ()_004b): Landslide risk evaluationand hazard mapping for rapid and long-travel landslides in urbanACKNOWLEDC.MF,NTSDeep thanks are *'iven to the Kanaza¥va Office of Riversand National High¥vays. MLIT, for cooperation in thefield ¥vork and as a source of information on the May2004 Iandslide-debris flow. Financial supports byresearch **rants (No. 15310127, Representative: F. W.Wang) from the Ministry of E.ducation, Culture, Sports,Science, and Technology of Japan (MEXT), and 16G-03development area, Lanc!slides.' .J. Int. Consortiunl on Lands!ides, 1(3), 27_1-235.13) ¥Van_9:, F. ¥ r.. Okuno, T, and Matsumoto. T. (2004): Deformationstyle and infiuential factors of Ehe giant Jinnosuke-dani landslidein Japan. Proc. 15th Sout/1easr Asian Geotech. Conf., 1, 399-40414) ¥¥ran_ , F. ¥¥r., Okuno. T. and l¥,1atsumoto, T. (2007): Deforrnationcharacteris ics and influential f'actors for the ziant Jinnosuke-danilandslide in the Haku-san h,10un ain area. Japan. I,ailds[ides.' JIn!Consoriiinn on Lanc!s!ides. DOI lO.1007/sl0346-006-0049-9,4(1) (in press). | ||||
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- Creep Behavior of Tuffaceous Rock at High Temperature Observed in Unconfined Compression Test
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- Kenko Shibata・Kazuo Tani・Tetsuji Okada
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- SOILS AND FOUNDATIONSVOl 47,No .l,io, Feb. 2007Japanese Geotechnical SoclelyCREEP BEHAVIOR OF TUFFACEOUS ROCK AT HIGH TEMPERATUREOBSERVED IN UNCONFINED COMPRESSION TESTKENKO SHIBA Ai), KAZUO TANlii) and TETSUJI OKADAiii)ABSTRACTGeologicai disposal in soft rocks is expected as one of the most practicable methods for isolation of high-levelradioactive ¥vastes. Since the country rock around the deep tunnels tends to be heated for a long term due to continuous collapse of nuclides, creep behavior of the soft rocks of imperrneable nature under hi_ h temper'ature should bestudied. Under different temperatur'es fr'om '_4'C to 95'C, a series of unconfined compression tests lvas conducted on atuffaceous rock, Ohya stone, at creep stress r'atios ranging frorrl 0.6 to I .O. The results sho v that the creep behavior isaccelerated by high ternperatures over 60'C. That is, for higher ternperatures, the time to failure is decreased, ¥vhile theminimum strain rate is increased. A creep model is then pr'esented, in ¥vhich attention is paid to the change in strainr'ate ¥vith time. Unique relationships bet¥veen the minimum strain rate and various creep parameters are used, thatappear to be dependent on neither' creep stress ratio nor' temperature. According to the proposed model, the creepfailure ¥vill not take place if the creep stress ratio is lolver than 0.44.Key words: constitutive model, creep, geological disposal, soft r'ock, strain rate, temperature, unconfined compres-sion test (IGC:F6/G2)Geological disposal is seen as one of the rnost practicable methods for isolation of high-level radioacti¥'e ¥vastes.studies are needed to elucidate the influence of temperatures on creep behavior of' soft rocks. Attention shouldbe paid to the rock type, and to high temperatures closeto 100'C for the geological disposal of high-level radioac-INTRODUCTIONSedimentar'y soft rocks, especially mudstones, ar'etive ¥vastes.expected as one of the prime candidate as country rockfor this facility (NUMO, 2003). Because they are leastEffects of temperature on creep behavior' under confinin_ : pressures ¥vere also investigated in triaxial tests byjointed thereby irnpermeable sufficiently to prevent suchhazardous ¥vastes from leakage.The countr'y rock around the disposal tunnels tends tobe heated for a long term due to continuous collapse ofnuclides for over tens of thousands years. The temperature of the surrounding rock mass close to the heat sourceHettema et al. (1991) and Thimus and De Bruyn (1998).Their results demonstrated marked influence of tempera-is expected to rise as high as 100'C (JNCDI, 2000).ratios were varied from 0.6 to 1.0. On the basis of theexperirnental data, Kato et al. (2004)'s creep model wasimpr'oved to take into account the influence of tempera-ture, but only limited test results ¥vere reported.In this study, under diffcrent temperatures from 24'Cto 95'C, a series of unconfined compression tests ¥vasconduct.ed on a tufi'aceous rock, Ohya stone. C.r'eep stressTherefore, Iong-term behavior, i.e. creep, of soft rocks inhigh temperatures should be studied.Four reports ¥vere found in the literatures on uniaxialcreep behavior of soft rocks under high temperatures.Yamabe et al. (2001) revealed that creep behavior of atuffaceous rock under temperatures from - 10'C to 55'Cture.METHOD OF CREEP TEST¥vas accelerated for higher temperatures. Similar findin_a._sTes't Appa/'atuS¥vere reported with a diatomaceous mudstone underFigure I sho¥vs the unconfined compression test ap-'_0-90'C (JO et al., 2005) and with a sandstone under1-80eC (Kodama et al., 2005). Howe¥'er, Kato et al.(2004) reported that creep beha¥'ior' of a mudstone wasparatus specifically designeci for creep tests under hightemperatures. The application of' sustained axial load isindependent of temperatures from 20eC and 60'C. Asrnade by leveraged dead ¥veights to f'orestall powerfailures. The maximum load, 50 kN, can allow applica-these reports contradict each other, more experimentaltion of axial stress, 25 MPa, on a specirnen of' diameter 50i)ii}iii)Chiyoda Corporation, Japan (keshibata@ykh.chiyoda,c0.jp).Yokoha na Nationai University, Japan (tani@cvg ynu ac.jp).Central Research Institute of Electric Po¥ver Induslry, ,Japan (t-okada@criepi_derrken.or.jp)-The manuscript for this paper ¥vas received fbr revielv on Jul}' 4, 2005; approved on July 26, 2006.Vri ten discussions on this paper should be submitted before September 1, 2007 ro the Japanese Geo echnical Society 4*38 -,Bunk_vo-ku, 'Tokyo 1 12-001 l, Japan. Upon request the closing date may be extended one month.1,Sengoku, SHIBATA ET AL_286LV DT*4Slraina! e,Tncrmocoupleoinsulated cellFig. 1. Test apparatus for creep test': of T1:1'1::47 m/s and the lon*'itudinal lva¥'e velocity Vp= 2474d:99 m/s were found within the ranges of previous studieson Ohya stone (Ku¥vabara, 1984; Nakajima et al., 2000;V :Kurumura et al., 2003). Consistent data ¥vith small variations ensured that these specimens ¥vere practically identi-,F:- 2100Xub¥cal to each other.b rs' Io' s4)eleajj'7Tas: sil 20QIO) : :1 40040F g. 3. Relationslvip betlveen q** and T35002800o 'o 60T ('O so molrv xurssls' l 2003) : :'Ei_ ht unconfined compression tests (JIS A 1216-1998)¥vere conducted under temperatures T= 24'C, 80'C_ and95'C (Miho, 2005). As sho¥vn in Fig. 3, the values of'I ::1"JI¥"' 'L' ;ti , "1'¥ "V700unconfined compression stren*'ths14i820;/t (kN/m3)Fig. '-. Relationship bet veen 11, Vp and yq= -O.0149T+ 6. 10 (1)The creep stress ratio, q****plq , is defined for the respec-mm.The specimen placed in the insulated cell is submergedin the ¥vater circulated by. a pump. The temperature of thelvater is controlled in a thermostatic bath equipped ¥vithheat source.Measurements are made for temperature by a thermocouple, axialment by a LVDT,lateral strainslateral surfacevere q =5.74 0.43MPa at ordinary temperature, '-4'C, and decrease linearly ¥vith increasing temperature. As r'eference strengths,the values of q (MPa) can be estimated as a function of T('C) obtained by linear regression.oload by a load cell, and axial displacerespectively. lvloreover, both axial andare measured by strain ( ages pasted onof a specimen at opposite diagonal posi-tions. Note that external measurement by the LVDT maysuffer from bedding errors (Matsumoto et al., 1999)^Whereas local measurement by strain gages is believed tobe more representative of specimen's beha¥'ior, and isused for further analysis.tive values of T, ¥vhere q****p is the axial stress durin_'creep.Loading alld Measure/7lentAfter the specimen placement in the insulated cell,the temperature of the cell ¥vater ¥vas raised gradually,0.5'C/min., to the intended value. The specimen vasthen left for at least thirty minutes before application ofaxial load. This is to allo¥v the temperature of the specimen to become the same as that of the cell ¥vater, which iscontrolled vith the maximum variation of :!:0.5'C.To avoid impact or dynamic effect on the specimen, theaxial load ¥vas raised slo¥vly, 0.230.45 MPa/s, to attainthe intended creep stress, q****p, in 10-17 seconds. Fromthe start of load application, measurement were madeSpecil 71 enRhyoiitic ¥velded tuff of Miocene deposit, denoted asOhya stone or green tuff, ¥vas used as the test material.Twenty-five cylindrical specimens of diameter d= 50 mmand height /1 = 100 mm were drilled from dry cubic blocksof about 300 mm. For saturation, they ¥vere kept in theevery 0.5 second for' 30 minutes, and then the interval wasset I minute after that.Data A ila!ysisThe creep time, t*, is defined as the elapsed time sincethe axial stress reached the intended creep stress.Although the axial load was kept constant during¥vater and deaerated for t¥vo ¥veeks.The siz,e, the ¥veight, and the ultra-sonic ¥vave velocitlescreep, the axial stress ¥vas slightly decreased as the cross-¥vere measured of all the specimens. As sho¥vn in Fig. 2,section of the specimen ¥vas increased gradually lvlththe total unit weight ),* = 1 8.5 1 (mean ¥*alue)O.?_6 (stand-creep defor'mation. So, the creep stress, q****p, is deter-ard deviation) kN/m3, the shear ¥va¥'e velocity V,= 1082mined as the average axial stress for O <, t*< t*F, ¥vhere t*f is CREEP BEHAVIOR OF TUFFAC'EOUS ROCKTabie l.T qq,,.,pL*qs"'" Iq.(oC)( 'lPa)Experimental condition and creep parameters!*1 t*2ea T In!t -/ min)(?'/a(min)o 663 .OOE-071 70222o 787.60E-054831203305 03o.88S . 97F -05547i3703_80o 693 60E-07> 70167> 70167o_79l .70E-0325916- o.750-o 7505,02O 911 .40E-043S872242-o 874- o.6903,23o . 623 . 90E-0715969916871 i26349- o.929o 732 50E-0616593l 962 1 4422- O.9)- l4 35o 84l 42E-0434874, , 54 98o.96ooo3.21o.653.80o 77( 'lPa)3,7824 4 . 47 5 . 7440 4.36 5.503 . 8060803L: ;(iHi l(min) (min)22843 1 1 7755- o.900- o_ 852H7 7(?･ )- o.900o 220- o 650o.262- o 800o 265o.916O 201*lo 258O 217- o.630o 250- o.680o . 2495.2- 4.914.34340E-062501 1 129S15034oo2 ,,o <- o.903-O 7192.0<oO. 150O.069O 096O. 1 97- o. 580o.7 9o 348- o 645- o 700o.338o 882 98E-O15 .ool 02l 03E-Ol2.85O.614.46E-06>31115>31115- o. sso*1o 722.43E-05> 2 1 322> 2 1 32',2- o.800*loo95 3.39 4.683 73o 80O.450 =O 1340.30-,2_0<o* I : N,Ieasurement by strain gages ¥vas failed_the time to creep failure. The values of t,f can be determined ¥vith least variations, as the creep failures takeplace abruptly; thereby defined by an arbitral value ofequated to he rninirnum strain rate, *,min' As sho vn inFig. 4(c), in the tertia 'y creep, the double logar'ithmicaxial strain, e*=20/0, in this study.t*, is again modeled by a linear expression. The slopes ofthe lines in Figs. 4(b) and 4(c) for the prirnary creep andthe tertiary cr'eep are defined as ml and ln3, respectively.Test Casesrelationship bet¥veen a and tirne lef't before failure, tcSeventeen tests ¥vere carried out as sho vn in Table 1.The transition time from the primary cr'eep to theTo study the influence of creep stress ratio, qc'eep lqu' andsecondary creep, tcl' is determined from the intersectiontemperature, T, on creep behavior, the range of qc"eplq.Furthermore, three tests were stopped before creepof the respective regression lines in Fig. 4(b). The transitlon tirne from the secondary creep to the ter'tiary creep,t*2, is also determined from the intersection of the respective regression lines in Fig. 4(c).As above, the strain rates, a' in each cr'eep stage can befailure, as the primary creep appeared to continue in-expressed by the following equations;was set from 0.6 to I .O and that of T vas set from 240C to950C*, respectively. Thr'ee specimens vere failed beforet.he intended creep stress ¥vas loaded, thereby 8.0>20/0.tolerably long time.Primary creep (O < t*CREEP MODEL AND CREEP PARAMETERSIn general, creep behavior of rocks is categorized intothree stages taking into account the change of strainrates, *, as sho¥vn in Fig. 4(a). In the primary creep, *decreases vith time asymptotically to a cer'tain value. Inthe secondary creep,* becomes constant; thus theminimum strain rate, *,*j*. In the tertiary creep, * incr'eases acceleratingly with time leading to creep failure.Kato et al. (2004) proposed a creep model based on thisthree stages concept. As shown in Fig. 4(b), the doublelogarithrnic relationship bet¥veen strain rate,*, and creeptime, t*, in the primary creep is modeled by a linearexpression. The strain rate in the secondary creep is thent*i)(c _10g 8* lnllog - Iog a*t**Secondary creep (t* <:tc tc2) a e (3)Tertiary creep (t*2 < tctcf( :)10gwheret,f)a = /n3 Iog + Iogtcrta,mit (4)a* is the reference axial strain rate at the referencetime, tcr'By integration of these strain rates for respective cr'eepstages,*, the follo ving equations can be obtained tocalculate the change of axial strains, 8*, with creep tumet*, as sho¥vn in Fig. 4(d); SHIBATA ET AL.;L(b)(a)( c)A '' .Sec(SecondaFy'' ''-Prin'ary* (log scale)t* (log scale)ea (log SCale)TertiaryPrirnary>lSecondary ,Tertiarv' Failure* Failure1lmlCa ,mln-tcf-tc2 tcf-t cltcl tc7-tcftc (log scale)tc- (normal scale)tcf-tc(log scale)(d))8a( normal scale:f'_a; 7c --Failureprimary secondar)i' la'_calTertiary< 1caOO tcl tc2 tcftc (normal scale)Fig. 4.Creep model and creep parameterPrimary. creep (0<t* t*1)8e:r ti' 1¥)+80. *a=(n7 ' 1)t "'=+1((:,)Secondary creep (t- <t.<t .) e =(5)(t -t l) ea*1 *= *- a a,mln * cTertiary creep ( t*2 < t**.*i* ( tcftc2 )e* =' (nl3 + 1)(6)tci)fll_( ) Tf +e .,(7)tcf tc "** 1tcftc21) Change of strain rate vith creep time Is typicallycharacterized by three creep stages, i.e. primary, secondary and tertiary creeps, as sho¥vn in Fig. 4.2) As sho¥vn in Figs. 5(b) and 5(c), the doublelogarithmic relationships bet¥veen* and t* in the primarycreep and between * and t*ft* in the tertiary creepappear to be expressed by linear expressions.3) Creep beha¥'ior is accelerated for higher temperatures, especially for over 60'C (Shibata et al., 2004).¥vhere 8ao is the initial axial strain at tc= O minute, and e iand ea2 are the axial strain at t* = t*i and tc = t*1' respecti¥rely.On the ¥vhole, the proposed model is described ¥vith atotal of eight creep parameters, i.e. n71, m3, tci ' tc2, 8ao,*r'*,mi and tcr, which can be easily determined by the abovementioned procedure from the test results. The transitiontimes, t*1 and tc2, can be replaced by the relative transitiontimes, t.] It,f and tc2ltcf'TF,ST RF,SUl,TSINFLUENCF, OF TEMPERATURE ONRELATIONSHIPS BF.TWF,EN CRF.EPPARAMF,TF,RS AND CRF,F,P STRESS RATIOFigures 6 to 11 summariz,e the relationships bet¥veensome creep parameters and the creep stress ratios, q****p/q , obtained under different temperatures, T.Figure 6 sho¥vs the relationship bet¥veen ll7}, ln3 andq*,**plq.. n71 represents the deceleration of st,rain rate inthe primary creep stage, and lll3 represents the acceleration of strain rate in the tertiary creep sta*'e. The values ofFigures 5(a) to 5(d) compare typical test results ob-ll71 seem to increase from -0.9 to -0.6 ¥vith the values oftained for' creep stress r'atio bet¥veen 0.84 and O.91 underdifferent temperatures. The follo¥¥'ing features are dra¥vn.q /q from O 6 to I O but independent of T Althou'h''**p " . ' , . *the values of ln3 range similar values, they are dependent 5CREEP BE賛AVIOR OFτUfFACEQUS ROCK0610・も先丁黙80℃丁軍80℃05＝，P勾冒＝088 目10・1惹P内、．．．＿．．．訪6・℃・・法『｝…＼…・…訟曇一謎．．ぶま翠二㌦詰匹プー『沁1σ’∼ 翻……04鑓”繍調響鰹窯03 σ二∫39F〆9冨＝088．．！10402 ヨO l10’50i50 300国0℃ 煮臥奪非llツ／ r＝40℃ ㍗24℃ 9‘譜」琿09レ…−9謂3盤躍088” 巽鍔，，F／9曽慧088 9；「0450 600150 300 4506〔｝0 ∫（min）’（m搬） （d）（a）Fl9．5（￡）．Relatl・鑓s是11pbetweenどaand！。f・r9。，。，P／9u−o・84−o・91Fl9，5（d）。Rel負1亘onsh」PbeIweenεaandずcforgC，、想P／9ロ竺o・84−o，9篁0010暦織噛糞』11「（℃）2440608095“1 ③ 醗 （》 」戯 Ψ鱗／9、こ0889 し一〇3’η， ○ 口 ◇ △ ム…i・06求』1二！．、．＼”Ql o ム ◇ ○隣 ◇ ムコ 会剣 Ψ 献φ8．認⑨G厨『φ貰一 一〇9圭び！、．一121σ5・15l o’： 10 10＝ 1σ101σ06∼c（min）u07 0、8 09 王0 9“障。p／9、（b）F「19．6・RelaIionship between1πi，〃133nd g。，書。p／guFig．5（b）．Rela匡ionshipbetweenεaandf。forg。，。。p／9u竺o・84−0・9玉loPT（℃）244060 80105 ㊥ 囲 ⇔ A一！￠1σ、還ir目l／r㍗80℃雰 』σ σ，や／9L軍08810−r／1。三1＿．．、．．．＿．．＝。㎏慨 『！ づ／！σ圏o℃・一ム．＿！一『瓦r！』101σΣ061010りi O二 ロユむ ゆ ぬ102 三σ07 08 09 1、09c「．緯p／9u ！Cf一1c（mln） （c）Fig．5（c）． Rel飢lo簸shipF董g。7。 Reiat蓬on曲ip be重ween1。f and gc，。。p／g、監between 6目and（fcげ’c）f・ぞ9cre。P／9u讐 O．84−0．91 Figure8showstherelationshlpbetween∼。玉／∼。f，！。2〃。r＆ndσ。，，，p／gu；曲ere∼。1／∼。fand1。2／∼。frepresen曲eratiosneithero昭。，。，p／9unorT。 Figure7shows the sem圭一10garithmic re正atiQnship be−of1c at the end of the prlmary creep and重he secondarycreep重o the f＆ilure time，∫。f，respect圭vely．The values oftween the tlme to creep failure，ご。f，a鳳d g。，，，p／σu．Theご。1／ご。f increase from O．1to O．3wlth the values ofσ。，巳。p／σu星ogarithmicv＆1uesof1。fdecreasemoreorlesslinearlyfrom O．6to1．0．Whereas，the values of1。2／！。f decreasewith（1。，，，p／（7u．The（1ata for24，40an（160。C again appeαrfrom O．8to O．6for the same range ofσ。，，，p／g、．Thissimilar，while those for over60。C shows significantlyimplies that，the relative perlods of the primary creep an（1smaller1cf values．the terti＆ry creep becolne longer for larger values of SHIBATA ET AL6JOC>t=.!t': o c::<>Aos*8T('C) 14 40 60 SOi*],i,. oc Ao a;o<>;; 06> A-iOll-1 -cc)AO'O'- 4A' i - -?.i__ _:c _O Il-i6leF cooa.6 e 7 O 8091 O1qcreeplquRe atronship betFig. 8140 T60( C_) 80-1820Fig. 11.een t,1 It,r t, /t,r and q,,,,p/qOoRelationship bctween parameter B slnd TParallel fitting lines are dr'a¥vn for individual temperatures as expressed by the follo¥1*ing equation;0504log=12 q*.**,j"**P + B (8)q**.; 03¥vhere their' slopes are set as 12 ¥vhich is the average valueof the slopes of linear regression lines for respective temperatures. As sholvn in Fig. 1 1, the intercept B is given as$ o. 2a linear function of T by regression analysis.alOo0607 OSi O i lq !q09**e*p *]iOiOe'f0li_ J!nes sr _ q_ :(8)&'{?)'_ _T ;socc. .¥ . .i O '-r=60 C - ' --' '-' -' il C'2._;_ ___[ . ..... . .::1 rso:C'______'Ezla)L// et: oT 95 C :Tl O-//:/( : :_'lcrs. eiC _';11 _ :i _' __ _''' _j_ ... 1.t ':::::: ::i_ _:_. :.::l O'sT( C) 24 40 60 80 95Q B c A v06 07 08 1 O 1 109q lq ,c*eep *Fig. lO.*. ,i*, and !*f, are dependenton both q*,**p /q and T. The influences of Tbecome moreevident for higher temperatures above 60'C. In the abo¥'ediscussion, it should be r'eminded that the unconfinedthe third type of parameter's,compression strength, q*, is defined as a function oftemperature, T, as Eq. (1).T 2s C1 0i 0'7temperature, T, are taken into account, the creepparameters are grouped into three types. The first type ofparameter, l773, is dependent on neither q****p/q nor T.The second type of parameters, nlj, t,1 /t,f, t.2lt*f and 8*oare dependent on q.,.,p lq ; but independent of T. Finally,Relationsivip between 8*o 8nd q****p lqFig. 9.B=0.0'06T 147 (9)When the influence of creep stress r'atio, q*,**p/q,,, andRelationship bet veen ia.m * and q**e* 1q*1RELATIONSHIPS BF.TWEF,N MlNIMUM STRAINRATE AND OTHF,R CREEP PARAMF.TF.RSKato et al. (2004) pr'oposed a creep model for softrocks, in ¥vhich all the cr'eep parameters in Eqs. (2) to(7) are determined from the creep stress ratio, q***=plq .In their model, the influence of temperature ¥vas nottaken into account, as these creep parameters ¥vere foundq****p lq*, while that of the secondar'y creep stage becomesshorter. Moreover, neither t*1 It.f nor t.2lt.f appears to beindependent of temperatur'e, T, in their experimentaldependent on T.the third type of creep parameters,Figure 9 sho vs the relationship between the initial axiaistrain, 8so, and q.,eep lq . The values of s*o increase frompendent on T, especially for T> 60'C. Other researchers0.20/0 to a little over 0.30/0 with the values of****pq lqufrom 0.6 to I .O. But they appear to be independent of T.Figure 10 sho¥vs the semi-logarithmic relationshipbetween the minimum strain rate' *, ,", and q /q The'*'* ".logarithmic values ofa *appear t,o increase linearly.with q.,..p /q. at a similar rate for respecti¥'e temperatures.data for 20-60'C. However, our test results sho¥ved that*, i* and t*f, are de-also reported this temperature dependent nature ofcreep behavior for sof't rocks (Yamabe et al., 2001;Jo et al., 2005; Kodama et al., ,_005).In this study, focus is placed on the minimum strainr'ate,*, i , because it is the first creep parameter to bedetermined in the analysis of creep tests ¥vith utmostcredibility and least scattering (Shibata et al., 2005). CREEP BEHA¥,IOR OF TUFFACEOUS ROCK!05l 0IG5 r __ r c) I s o 60 so"¥f,e'- ' o <e. -'-'¥1io []_ i04/A j'..1?:J'flo{o'f----''v Eq(ll) --' : ' j_'loEq(15)* "*cI f fE ' io). ; il"- ii o --Eq 1 1-' ) :¥' ' O 3s eo -' T / 'e } I oe _O1. : .T('C) 24 40 60 80e llo -Oola'l O s : O' I 01 O S i 0+ I O ; I OI (rllo s 1(r7 lO'ti iO's loOe I Omn (o/o/min)sFig. 12. Relationship between t*r, t*i, t*2 anda,mi*Fig. 14.o' Io'=a+:EJnRelationship bet,veen e*o and ia *i*, i-o 3-O 6- O 92 Iocr+ 2.32' ': "'m "t <C> o >J _/¥Figure 14 sho¥vs the semi-logar'ithmic relationshipAe>! ,between 8ao andT( 'C ) 24 40 60 so 95*1 210 10 iOa ,m*n･ . The values of eao increase linearlywith log-cycles of *,**i**. The following equationobtained by regression analysis.- -OS-1 S- 1) (13)ln3 = - 0.733 (14)Eq (13)Eq (14)lO i ICo ICl(( /c/min)ml = - (logOoc AmE ･<>A vm oo c]vas then+0.35e*o = 0.023Iog b (15)a,minIt is interesting to note that, the relationships bet¥veenl('5 10* ICr= ICr: Iorl 10 10and other creep parameters are unique as expressed*,m*", mi* (c; 7c/min)by Eqs. (10) to (15), and are dependent on neither q.,.ep/q* nor T.Fig. 13. Relationship between nll, nl3 and i*. j*IMPROVED CREEP MODELFigures 12 to 14, thus, show the relationships betweenand other creep par'ameters obtained under different*,**:Featu/'es oj' hnproved C'reep ModelImpr'ovement vas made on the cr'eep model proposedFigure 12 shows the double lograrithmic relationshipstemperature. This improved model succeeds the basiccreep stress ratios, qc'ee lqu' and temperatures, T.by Kato et al. (2004) to take into account the infiuence ofa,min dependconcept of the original model, that the changes of strainon both qc'eep /qu and 'Tas sho¥vn in Figs. 7 and 10, respec-rate with time are typically expr'essed by Eqs. (2) to (4) fortively. But, the relationship bet¥veen tcrespective creep stages as sho¥vn in Fig. 1,5.In the original model, all the eight cr'eep parameters aregiven as functions of the creep str'ess ratio alone, and nobetween t*1' t*2, tcf anda,min' Note that t*f andanda,min becomeslinear and unique, and is dependent on neither qcreep lqunor T. The following equationvas then obtained byregression analysis.I Ol loa I- .37 (10)log -tcf=' c a,m*nThe similar relationships bet¥veen tcl ' tc2 anda, in are alsorepresented by sub-parallel lines as expressed by thefollowing equations.log t*1 =O 92 Io(:j- I .68 (1 1)log t.2= '- I a,m**03 IoCT- 1.59 (12). ,:' *,"****Figure 13 shows the semi-logar'ithrnic relationshipsbetween lnI m･' 'anda*ml*･ 'While the values oflnlincreasewith log-cycles of a*i ' the values of ln3 seem to beindependent of a****'･ The r'espect.ive relationships for mland ll73 are represented by a hyperbolic function of *' *',and a constant, r'espectively.attention 1¥'as paid to the influence of temperature.However, as explained earlier, the test results on Ohyastone shol¥'ed that some creep parameters, *,*i** and t*f,are dependent on not only q*,**p lq*, but also T (Shibataet al., 2004).In order to take into account the influence of tempera-ture, the method to determine the creep parameters aremodified. Creep parameters are divided into two groups.The ones are intrinsic properties, i.e.*, i , t,f, t.1, t,2, nlj,ln3 and 8*o. And the other is a reference value, i.e.**.The seven intrinsic creep parameters are determined int¥vo steps. Firstly, the minimum strain rate, *,*i , isevaluated from creep stress ratio, q***,p lq , and tempera-ture, T, using Figs. 10 and 11 or Eqs. (8) and (9).Secondly, the other six parameters are estimated from thevalue of*,*j* using Eqs. (10) to (1 5) Ivhich are unique and 8SHIBATA ET AL．εa（iogscaio）丁段b鳳e2． ■he v貸垂ues of COV for e段ch creep P鼠r段meterPoint＼、、 、 Dlf艶ro臥9￠謹ぐPguユ霧ご7’εar獣＼．。ノ＼ Creep Kato et ai、pa「ame［e「 Thi （2004）log（ら、繍） 0．31Eq（2） ’ Eq（4）、 ＼ E蝋12）O Endoピprf爬【yc鯉P￥・、E鰍11）＼ピMudsto鷺e0鮭yaStone＼ レ！！ の1ゴfcr。n：’遇隅，n） Kaεo et al．【udy Tl誠S Study （2004）0．260．230、19lo9（∫亡r）0、670．590，300．Z8109（fd）玉．050．930。260．26109（∼C2）0．770，690，250．25’ni0，130．090．190、i817∼零0．100．100．640。640．860、090．870．i4 、 、 ＼g E網σf瓢（〕臨r｝oreOPPr＝m畠ryα岬sミccnd訂y。脚丁￠『瞳ピ“eごPごcrも （iO9㏄aie〉εユo（％）Fig．15。 Co獄cept of tbe proposed creep mode皿respectively．The extrapolate（i li歎esξor the primary creepapPear to conveτge at a singu歪ar point in early part of the10三creep behavior．Th量s un量que po量nt，1，玉s arbitraτily takenas（1。，，εa，）＝（1．0×10−4minute，10％／minute）for Ohyastoue and（1。，，ε、，）＝（1．0×10−4minute，40％／mlnute）forMudstone．尽／茎0α’1層α（7ッ0ゾ’1）ξ∼∼θ1岬1ηi17ing C1でθp Pα19σ1nθ∼θ1写 Table2compaτes the coefficleat of variations，COV，’沁for the intrinsic creep Parameters obtained for both Ohyastone＆nd Mudstone．These valuesτeprese勲t the accuracyoぐthe proposed reladonships to（ieteτmine the indivi（iual104 三〇『’ 1σ2 10’【 三〇〇 10三 10ま 1σ 10ξ 10《 Ioo ‘c（min）creep parameters，i．e．Figs．10−H，12−140r Eqs．（8）to（i5）． （al The（iata of Ohya stone sぬows that，of all t封e creepparameteτs except1η3，smal玉er values of COV are ob−Fig，玉6（9）． Rel段額ons匪灘ip bet、veen6ユandゴc for Ohy段s｛onetained for tぬe proposed method than由ose for Kato et aL（2004）’s metbod．Similar trends are seen for the data of103 7罵60℃10∼守認，ノ9、誤〕71 アゑぴじ10！100Mudstone．Tむe reason for顔s improvement is that，asshown in Figs．12to 14，the strongeτcorrelations werefound between the minimum strain rate，ε、，min，whichreHects the variations of specimens，than the creep stress、ratio，σ。，。，p／σu，and the o出er lntrinsic cτeep parameters．芝ま『鴇10『E1σこ！icαイ1層αcツoプrル哲04θ11ng C14εθp Bθhαvio1層10『3 Comparison is made for creep behavioτbetween theexperiment and由e proposed modeL Figures16（a）and1041σ｝1σ6國 9課”F・ 9；濫｛｝・79104 1σ♪ 10二 1σ卜 王00 10己 三α 105 10‘ 1G5 ’c（min） （b）Fig．16（b）．Rela重ionsilip be載wee服ε該and f。for MudsIone16（b）sむow the relationships between strain rate，εa，andcreep time，∼c，for Ohya stone and Mudstone，respec．tively． Furthermore， Figs． 17（a） and 17（b） show therelations娠ps betwee熱creep strain，ε巳，and creep time，1、，for the respective rocks．The open symbols imply theexperimenta1（iataラwhile the broken curves imply theproposed model， Overall agreement between t封e experimental data andthe pτoposed model ls good，although some extents ofdependentonne量ther（1。，，ごp／（1unorTasshowninF呈gs．12deviation aτe observed for Ohya stone at T翼800C aadto14．g。，，ピp／σ、翼0．88andギor Mudstone at T＝20。C andσ。，，ピp／ For the reference creep Parameter，assumptions are9、瀟0．86．Hence，it may be coaclude（i that the proposedmade that the creep bebavior starts from a certain point Ias shown in Fig．15。Figures 16（a）an（i i6（b）show therelat量onships between strain rate and creep time for Ohyastone by this study a熱d！〉1udstone by Kato et a圭．（2004），model is valid foτboth Ohya stone and Mudstone toYepresent creep behavior under vaτio毫ls co熱d至tions ofcreep stress ratios and temperatures． 9CR班…P BEH、へVIOR OF TUFF．へCEOUS ROCK05000 τ；ウり℃ ぐ 1属ユ4℃9茸，．ア9．憩s4 9欝宵刃メl ssrCc）24 4＝π1 昏9 8り 肇51＝二4℃ 9 口 φ ム ▼一〇39、豊066 A −06 1η1騙07809＝，，F9』143 ＼ Ψ v φ轡劉 一〇9 φ 幽幽”“』幽qqq＾＾“幽幽”僧一醐”曹鞘”v魯｛“薗蟷 42N 繍…蝸i麺：F飢1…漁5 ”1・二‘1Q9﹁‘1﹃％挿020嗣062一15104 10『」 1σ3 1σ1 100 10【 10z iσ 10‘ iO》 10604 05 06 07 08 09 10 11 9α、ごP！9u rc（min） （a）Fig。18． RelaIio霧1ship beIweenη11a鳳d gc，日￠p／g口Fig．17（段）、 Rei郎ionshlp betweenε凱＆nd∼。for Ohya sto臓e1「6series of creep tests w＆s conducted under uncon負ned1長2。毛i薩． 18l 劃卜、σC 9“。ア望。蔚s6 熱σ一・一9・勇72condition on a tuffaceous rock，Ohya stone，at creepstress ratios，σ。，。，p／σu，ranging from O．6to1。0、Empirlcalrelationships＆re玉nvestigated for the three creep stages，i．e．，primary creep，secondary creep and tertiary creep．14The fo1玉owing conclusions are（iraw簸．ま ユ2（1）Themlnimumstrainrate，εa，．、i，，andthetimetocreepfailure，！。f，arefounddependentol主bothσ。，。，p／σu輸 100806妻箋萎萎嚢萎ζ鷺釜轟and T。The inHuences of T become more evidellt forhigher tempeIlatures above60。C．However，由e rate ofaccelerat玉on of strain rate in tert玉ary creep，1n3，apPeaII to 鶴，評．試｝71104 三σ3 10一二 玉0具 100 ！OI 10： 1σ 104 10》 ’c（mln） （b）be dependent on neither（1。，。，p〆（1、監nor T．Fur出ermore，therate of deceleratlon of sξrain rate in primary creep，〃71，and重he relative time bounding童he three creep stages，‘。…／1。fand1。2／∼。ガ，aredependentonσ。，。，P／σulbutindependentof T．Fig，17（b）．Relationshipbe重weenεユ貧nd∫，forMqdsto騰e（2） Focus was placed on the minlmum straill r飢e，ε、、min，becauseε、．min is considered as most represen重atlve of creepbehavior and can be determined wl重h reasonable accuracyCONDITION TO CAUSE CREEP FAILUREan（i confidence．Un玉que rela書ionships betweenεa，ロ，in and Although the condition to cause creep failure is lm．t紅e other creep Parameters，オ。f，1。1，∼c2，〃11，1113andε撫o，areportant from the englneering point of view，疑is raξherfound，andtheyapPe＆rtobedepellde臓tonneltherσ。，，，碧／dif資cult to tell whether creep wlll dimlnish or enter thetert玉ary creep豆eading to fai互ure．The condition of uniaxiaIσu llor T．（3） In order to take into account the il1Huence of tem−creep fa琵ure is d圭scussed in the fo1豆owing．perature，a new metho（l for detenniaation of the c！’eep From the concept oftheproposed creep model，as seenparameters was proposed for tぬe Klato et al．（2004）ラs重n Fig． 15，圭f the strai煎 rate continue to decrease andcreep modeLτhis metho（1was justified as valid，as goodwould nQt en重er童he secondary creep，creep failure wi1豆agreement was observed betweα1the model and the testnot take p至ace。This non−fa呈1ure conditiou is rea豆ized，ifresu至ts for both Ohya stone and Mu（istone un（ier variousthe slope of the line expressed by Eq．（2）for t紅e prim＆lycreep，1n1，is greater than that of the line expressed byEq．（11）for the creep tlme to enter the second＆ry creep、As shown ill Flg．18，the value of〃11灘（』logε、／沼∼。）；1／（一〇．921）篇一1．09 and 重he regress玉on Hne 〃1歪；0．780（σ。，，，P／σu）一L43provide重hecriticalvalueofcreepstress ratio to boun（i the fa圭lure condition to the non−failure conditionεしs O．44．Sillce〃21is not dependent oncondit呈ons of creep stress rat玉os and temperatures、（4） Accordi勲g to the proposed model＆nd重he ex−pelimental da｛a，重he creep fa玉至ure will not｛a盆e place if thecreep stress ratio is lower than O．44for Ohya stone． Fur重her study is nee（ied by triaxial creep tests ullder難igh temperatu11e to investigate the inHuence of con且nlngやressures、Moreover，the i亘且uence of loadlng rate to theiatended creep stress，（1。，馨。p，shou互d be investigated fortemperature， this crit主cal value is independent of themore rigorous determination of the relevant creeptempera重ure，parameters，CONCLUSIO翼SACKNOWLEDGEMENTSUnder different temperatures，T，from24。C to95。C，aSincere thanks are glven to Mr．Yuji Miho，＆gr＆duate 王0SHIBATA ET AL．stude鍛tGfYokoh＆maNatiQnαIUnivers圭ty，fGrprovid三ngvaluable experimental data．7）Kuwabara，K， （1984）：αassl費ca【io簸of rocks by compresslo職and shear strengtむs，，ノ．oゾ“／SEG，25，Special issue，25−33、8）MatsumotQ，M，Hayano，K．，Sato，丁．，Koseki，」．andTaζsuoka， F。（1999）：τimee匪ec【sonstress−stralnpropertlesatsmallstrainsofRE、FERE、NCES sedime蹴arymudStO鷺e，Proc．211ゴ加．Sアη7μoηP’『θ一ノiα〃ε’1ぞ 0εブ01”’nα∫io／1Chαヂρc∫θ鷹’ic50∫Gθo〃7σ∼θr酪，1，3B一一321，1）Hα【ema，M．H，R．，dePeter，C．，」．andWoif，K．一H．A．A， （1991）：9） 氏4茎ho，Y．，Tan玉，K．，Sh玉bata，K。and Okada，T、（2005）：Inaue頁ce of 照ectsofしemperatureaRdpQrewaζero願creepQfsaRdsto魚erock， ro（：k type QR creep be亘av圭or Qbserved in uncQ【L蕪Red creep tests， Ro（♪んハ4θご乃α11’（〕5α5‘7ル∫置〃∼’ゴ直∫ぐ’ρ1〃∼θ1ツSciε’∼ぐθ，Baikema，393−404． Proc． 34〃∼ Sア〃∼ρ． 017 1∼ooん 1Vθchθ’∼’c5， JSCE， 495−500 （1“2），lapa臓 Nuclear Cycle Developme煎 1nstituこe （2000〉：Projecεεo establish 覧難e scienεiftc and tec鮭nica互bas呈s for HL∼V disposal玉n ，∫apan，2nゴP1909ノ■e5∫」R（∼ρ07’011Rθ5θθ1でhα’7‘1∠）θソθ10ρノ11θ17’，ノ101明11∼θ Japanese）．10）Nakajim呂，T。，Tani，K．and Okada，T、（2000）：Experlme熈al sωdy ond罫ai照geco繭乳lonofln−s1τu【ri＆xiahestonrockmass，P1「トo‘． Gθ0109’cα1∠万5ρ05α10ゾノゾ1，μ！’η／α〃ση，2，4．2Design of d1sposal 35’11SJ棚μoηGεαθc1∼，Eη9。，JGS，1001−1002（lnJapanese）． fac玉1ity（in Japanese）H） Nuc菱ear V》7aste1〉lanagement Organ玉zadon of Japan（2003〉＝Geolo9一3）JQ，M、，AQki，丁。，Ogawa，T．a跳d Ya磁abe，丁．（2005）＝E琵ect Qf tem− 玉cal dispQsa玉，cQnsiderat玉Qn Qn safety，NU！ヤ10，！50（in Japanese）・ peratureon由e鵬echaRlcalbeわaviorsofadiatomaceousmudsto麟e，12） S｝1玉bata，K．，TaRi，K．and Okada，T，（2004）：Uncon島職ed creep test Plo‘． 34∫h 5）ワηρ， oη 1∼ocん ∫、ゲθchθ11’c5， ，ISCE， 177−182 （in Japanese）。 of tu鐸 at ｝1玉9ぬ 芝empera【ure， P！ηc、 ．39’h ノ‘47α11 八7‘7’． Co〃プニ oπ （｝θo∼θごh・五π17g・，571−572（玉n．lapanese）・4）Kato，Y．，Tanl，1く、andOkada，T．（2004）：U獄con且nedcreeptes葛of soft sedimen【ary rocks at higll こempera【ure and proposal of夏3）S短bata，K．，Tanl，K．and Okada，T、（2005〉：Uniaxiai creep test of prediαion model for creep beぬav1or，P1’oご、33擢Sダη1ρ．oηRoごん st面n raεe and creep parameters一，Pヂoご。34∫h S）ア〃∼μoηRo欲 Ohya s【one at hig猷emperaωre−Relat1o且ship beしween min三mu礁 西∫εchα刀1c5，JSCE，25−32（玉簸，Iapanese）． A4echρηκ5，，ISCEラ玉一8（玉n Japanese）．5）Kodama，N．，ヂujil，Y．and Isllijlma，Y．（2005）：Ef￡ects ofτempera−14）Thlmus，J．Fr．and De B田yn，D．（1998）：Long−term由ermo− me麟anlcalbehaviorofBoomclay，ThθGεo！θ‘ノ1’7’c50ブHθπ1 ture on creep beむavior of Inada granite a臓d S頴rabama sandsto鷺e， Pノ曹o（r． 34∫h S．｝ワηρ． oη Ro（汝 」、グθc1∼αη’c5， JSCE， 183−188 （in ，Japanese）． So’Z∫一Soゾ∼Roごん5，Balkema，337弓41．15）Yamabe，1〉1．，｝vl圭yamoto，A．，ho，F、and Tan玉，τ．（2001）：Evalua−6） Kurロmura，丁．，Tani，K，and Okada，丁．（2003）＝Experimental sヒudy t1on of creep be赴avlor ofsoft rock u鷺der non−iso由ermal co疏d三t1on andmodelingofscalee牙ectonstre澱g由c擬aracteristlcsofO簸ya and i1s apPl套cab玉1i［｝r for numer三cal analys玉s，Pノ’oc。31∫1＄yn1μ 011 sto鷺e，Proo．32η‘1Syllrρ．oηRocたム4θ（7hαη’c5，JSCE，107−112〔in Rocたノ》θ‘ノ7θη1c5，JSCE，231−235（in、｝apanese）． ∫apaRese）、
- ログイン
- タイトル
- A Thermo-poro-visco-plastic Shear Band Model for Seismic Triggering and Evolution of Catastrophic Landslides
- 著者
- N. Gerolymos・I. Vardoulakis・G. Gazetas
- 出版
- soils and Foundations
- ページ
- 11〜25
- 発行
- 2007/02/15
- 文書ID
- 20976
- 内容
- SOILS AND FOUNDATIONS¥!ol 47, i¥ O_ l,l25, Feb2007Japanese Geotechnical SocietyA THERMO-PORO-VISCO-PLASTIC SHEAR BAND MODEL FORSEISMIC. TRIGGERING AND EVOLUTION OFCAT'ASTROPHIC LANDSLIDESNIKOS GEROLY rosi), IOANNiS VARDOULAKlsii) and GHORGE GAZHTASiii)ABSTRACTThe goai of this paper is to develop a constitutive model for the rapid deformation of clay-rich shear zones. Such amodel ¥vould be necessary to descr'ibe the seismic triggering and evolution of catastrophic landslides. The model isbased on: (a) the ¥vell-documented in the literature strain-softening and viscoplastic behaviour of saturated clays,and (b) the concept of frictional softening due to heat generated pore-water pressures. T'he inelastic stress-strainrelationship is described with a 1-dimensional cyclic constitutive model of the (Bouc-Wen) type, coupled ¥vith aCam-Clay frictional la v vith hardenin_ : and a set of equations that govern the mechanism of heat-generated porewater' pressure build up. Calibration of' the model parameters is accornplished through laboratory tests, ¥vith the helpof artificial neural net¥¥'ork analysis. The infiuence of key variables on the behaviour of a rapidly deforming shear bandis thoroughly investigated and the resuits of the analysis are critically discussed.Key words: catastrophic landslide, clay, heat generated pore-¥vater pressures, neural net¥vork, shear band, thermoplasticity, thermo-poro-viscoplasticity (IGC: B3 /E8/E14)particles present in the soil:INTRODUC1'10N(a) A turbulent mode, in soils ¥vith high fraction ofDynamic deformation of a saturated clay-rich shearrotund particles (i.e., with cla)' fraction lower thanband involves strongly coupled material nonlinearities,20-25010), or vith platy particles of high interparticlesuch as: (a) strain softening (s!ow residual strength), (b)friction. The slo l' residual friction angle (the shearstrain-rate dependencyst residual strength), (c)thermo-viscoplastic softening due to heat-generatedstrength at slo v displacement rates) is hi**h anddepends mainly on the shape and packin*' of t.herotund particles, rather than the clay mineralogypore-¥ 'ater pressures, and (d) hysteretic stress-strainbehaviour.Numerous experimental results in the literature sho¥vthe relationship with the aforementioned mechanisrns of(kaolinite, illite, montmorillonite, etc).(b) A sliding mode, in soils ¥vith high platy clay (lessthan 2 ft/m) fraction generally larger than 400/0500/0 .of platy particles, clay mineralogy, pore water chemistry,coefficient of interparticle friction, overconsolidationratio, mean normal effect.i¥'e stress, fraction of rotundparticles, existence of particle orientation, etc).The residual strength of soil at slow drained shearin*"A Iow-strength shear band of preferred platy particle orientation develops. Slo¥v residual str'ength ismainly controlled by the interparticle friction ofclay minerals, clay rnineralo*'y, pore water chemistry, and normal effective stress. Skempton (1985)suggested the followin*' typical values for represen-rates has been studied extensively during the last fourtative clay minerals: 15' for kaolinite, 10' for illitedecades. Various correlations between slo v residualstrength and index properties have been proposed (e.g.or clay mica, and 5' for montrnorillonite.(c) A transitional mode, in ¥vhich there is no dominantLupini et al., 1981; Bishop et al., 1971; Skempton, 1985;particle shape (platy or rotund), ¥vith clay fractionBromhead and Curtis, 1983; Tika and Hutchinson,bet¥veen 200/0 and 500/0. Shearing involves both1999). Lupini et al. (1981) utilised the r'esults of a largeturbulent and sliding behaviour at different iocationsnumber of ring shear tests on natural soils to study theof the shear zone. In this mode, slow residualseveral index properties of a clayey soil (e.g., the fractioncontrolling mechanisms of residual shearing. Theystren*'th is sensitive to srnall chan*'es in soil grada-pointed out that three modes reflect the quantity of platytion.i}i,iii)Post-Doctorai Research Civil Engineer, National Technicai University of Athens, Greece (gerolymose*mycosmos.gr).Professor of' Applied Sciences, dittoProfessor of C ivil Engineering, ditto (gazetas@*ath,forthnet.gr).The manuscript for this paper vas received for revielv on July 7, 2005; approved on Juiy 26, ,-006.¥Vritten discussions on this paper should be submitted before September l, 2007 to the Japanese Geotechnical Society, 4-38-,_, Sengoku,Bunkyo-ku, Tokyo 1 12-001 l, Japan Upon request the closing date may be extended one month.11 CJEROLY 'IOS ET AL.12The infiuence of pore ¥vater chemistry upon the residual strength of pure and natural clays, exhibitin_ : thePe k tr ngthq,sliding shear mode, has been studied by several researchers (e.g., Moore, 1991; Anson and Ha¥vkins,lf1998). They demonstr'ated that the type and concentra-Fast res du3 Sta'e(at large veloeities)102400Displ cement : mmFig. 1. Idea]ized evolution of the mobilized friction angle during t il esiiding process in a ring shear apparatusfriction an*･le of about '-', for a calcium-exchangedkaolinite compared ¥vith a sodium-exchanged kaolinite.The increase is larger, reaching 5', ¥vhen the predominantclay mineral is montmorillonite. Salt concentration ¥vasalso found to influence the residual strength. An increase,of about I ' to 2' in the residual friction ang:le of L,ondon3sTU TRSSh5 r, Q eeo2s20and ¥Veald Clay (¥vith illite the predominant mineral),respectively, Ivas reported by Moore (1991).IsAlthou h numerous studies ha¥'e been carried out10regarding the residual strength of clayey soils tested in the5Pt8teE eCOrin*･ shear apparatus, only a fe¥v of them ¥vere dedicatedto the fast residual strength, i.e., the ultimate strength atAccording to their research, three types of rate effect onthe residual strength are identified:(a) A positive rate effect,in soils sho ¥*ing a fast residuali (prOC ciayresults of a series of ring shear tests on saturated clays,sho¥ved that alteration in residual shear strength (causedfast displacement rates. Tika et al. (1996) studied thefast shearing response of pre-existing shear zones andpresented results for a ¥vide range of natural soils.SleYi residu 1 si t(Pr sresidual shear strength. Moore (1991), exploiting theparticles. He reported an a¥'erage increase of the residuale{gt large dispiaeemenis)tion of cations in the pore ¥vater significantly affects theby the presence of exchangeable cations in pore ¥vater)increases with increasing specific surface area of clayCri e { SlO 200ROEO100Clay r 0t:en C*Fig. 2. Dra"rammatlc correlat on of sloll resldual fr]ct]on angleththe cla)' fraction: The three regions of different sl]ear mode bel]av-iour (TU. TR, S) and the tl]ree regions of different consequences(neutra], negative, positive) of the rate of shearing on residuaistrength, are: The error band of the single experimental pointrepresents the effect of pore'ater chemistry on residual strengthstrength higher than the slo¥v one This type ofviscous behaviour is associated only ¥vith the sliding(even enormous) velocities are developed in catastrophicshear mode.landslides. For example, referring to the disastrous(b) A negative rate effect, in soils sho¥ving a significantdrop of fast residual stren_ :th belo¥v the slo¥v resid-Vaiont slide, back-analysis indicated that the sliding massual str'ength, when sheared at rates higher than ato 40m/s (Mench, 1966; Habid, 1967, 1976; Goguel,moved some 400 m, reaching a maximum ¥'elocity of ,_Ocritical value. Soils with transitional or slidin shear1978; Muller, 1964, 1968; Ciabatti, 1964; Voight andmode may exhibit this type of behaviour. In someFaust, 1982; Vardoulakis, 2002). It is thereby evident thattests, fast residual strength was measured to be asthermo-poro-mechanical behaviour of clays is a criticalissue in the evolution of catastrophic landslides. Nevertheless, it is pointed out that frictional strain-ratelo¥v as 600/0 of the slo¥v residual strength.(c) A neutral rate effect, in soils sho¥ving a fast residualstrength nearly equal to the slo¥v residual irrespecti¥'e of displacement rate, associated ¥vith the turbu-lent shear mode.Tika et al. (1996) clarified that: (a) the fast residualstrength is reached ¥vhen the displacement rate surpassesa critical value; (b) stren>'th is sli*･htly affected by excesspore ¥vater pressure arisin*･ from the contractivebehaviour or from heatin_9: of the clay, and (c) thenegative effect on residual strength results from theincreased soil flo¥v potential due to ¥vater absorption bythe shear band, caused by its diiati¥'e behaviour.Ho¥vever, the critical velocity required to reach the fastresidual stren th ¥vas measured to be in the order of O^005m/s to O.1 m/s. This is far smaller than the one requiredfor initiation of heat generated por'e ¥'ater pressures,¥vhich can be of the order of fe¥v meters per second foroverconsolidated clays (Vardoulakis, '_002)^ On the otherhand, it has been proven by several researchers that largesoftening ¥vithout heat-*･enerated pore-¥vater pressuresmay, under cer'tain conditions, Iead to accelerated creep(Vardoulakis, '-OOO). This means that frictional ratesoftening behaviour is by itself a significant destabilizingf actor.The abo¥'e conclusions on shear behaviour of clay areelucidated in Fig:s. I and 2.It is ¥vell documented in the literature that clays arethermo-viscopiastic materials (Campanella and Michell,1968; Nova, 1986; Hueckel and Baldi, 1990)Hicker(1974), Despax (1976), Modaressi (2002), and L,aloui andCekerevac (2003) reported that some clays demonstratethermoplastic softening behaviour, r'efer'ring to theirfriction coefficient in the critical state, ¥vhile others ar'epractically unaffected by temperature. Modaressi andLaloui (1997) pointed out that ¥vhen a clay sample isheated slo¥vly enough to allolv complete draining, t¥vophases of behaviour can be distinguished: SHEAR BAND ivIODEL' a reversible phase, termed "thermoelasticity", dueto diiation of the miueral cornponents, and' an irreversible phase, termed "thermoplasticity",caused by both dilation of clay minerals and collapseof the absorbed ¥vater, resulting in failur'e of someinterparticle ties.Exper'imental vork identifies that the response of anoverconsolidated (OC) clay in thermal loading is differentfrom that of a normally (NC) to slightly overconsolidatedclay. In an OC clay, thermoelastic dilation during theheating phase is followed by thermoelastic contractiondur'ing the cooling phase. In a NC clay, thermoplasticcontraction during the heating phase is usually followedll)va- ( )T (t)Ut)v )d ti] 8(t{t' u{t} __' iIl--:--. / oS e rFig. 3.ndSchematic illustration of the shear band modelby additional thermoelastic contraction during thecooling phase. Ho¥vever, Sultan (1997), and Laloui andCekerevac ('-003) sho ved that at high temperatur'es,above a critical value, overconsolidated clays sustainthermoplastic contraction as ¥vell.In drained loading conditions, therrnoplastic contrac-the forrnation of the shear band (at the critical state), and(iii) a visco-plastic model for strain and strain-ratesoftening at large displacements (residual state).A comprehensive methodolo_ :y for calibration of thetion. Under undrained conditions, the natural trend ofmodel parameters, is also presented by resorting topublished experimental data. Closed-form expressionsare developed from correlation of the key parametersthe soil for thermoplastic contraction _g:ives rise to anwith characteristic index soil properties, making use ofincrease in pore ¥vater pressure, ¥¥'hich in tur'n results inartificial neural network analysis.The objecti¥*es of the paper are (a) to de¥'elop a sheartion results in shear strength increase due to soil densifica-frictional softening. On the other hand, thermoelasticdilation either would not affect at ail or ¥vould only slight-ly increase the soil shear strength. The preconsolidationstr'ess is also affected by temperatur'e, being a decreasingfunction of it. Thus, under drained loading conditions astemperature increases the br;ttle and dilati¥'e behaviourof an overconsolidated clay alters to a more ductile andless dilative (or even contractive) behaviour.Vardoulakis (2000) starting from a set of axiomaticprinciples, rcformulated the equations that govern themotion of a rapidly and monotonically deforming shearband. The soil vas considered as a t'o-phase mixture ofsolids and fluid, and the governing equations werederived from the corresponding conservation la¥vs ofmass, momentum and energy. The resulting governingequations are t¥vo coupled difttrsion-generation partialdifferential equations, containing t¥vo unkno¥vn functions: excess pore-¥vater pressure and te nperature insidethe shear band. The ¥'elocity field is consider'ed as anband model for the analysis of seismic triggering andevolution of catastrophic landslides, (b) to present amethodology for calibrating the model parameters ¥vhenrelevant experimental data is scarce, and (c) to per'for'm a(limited) parametric analysis of a dynamically deformingshear band.The ps'oposed model aims at joining theoretically theinitiation of a landsllde due to seismic loading and ther'esponse of the slide at extremely large deformations.According to the authors' knowledge only a limitedamount of studies is devoted to this issue, including ther'ecent ¥vork of Chang et al. (200) ).CONSTITUTIVE MODEL: EQUATIONS ANDPARAMETERScalibrated the model parameters on experimental data,Prob!eln DefinitionThe problem studied is that of a deformin*' shear bandconsisting of saturated clay, subjected to shear loading.The shear' band is considered of' infinite length and ofthickness db (Fig. 3). Both of its boundaries are assumedexternal loading, and therefore is presumed known.He applied his model to analyse the Vaiont slide, havingfrorn the literature. Strain and strain-rate induced fric-impermeable to fluid fio¥v and nonconductive to heattional softening was also considered in the analysis byflux. This means that the field ¥'ar'iables in the shear band,utilising results from ring shear tests on Vaiont clay speci-namely excess pore vater pressure p, temperature 6, andshear strain y, are 'unctions only of time t. Such boundary conditions imply undrained and adiabatic response,mens conducted by Tika and Hutchinson (1999).In this paper the governing equations of heat-generatedpore pressures inside a rapidly deforming shear band, aresummarised. Their forrnulation is limited to adiabaticand undr'ained response conditions. Then a constituti¥'emodel is developed consisting of the aforementionedequations, coupled with: (i) a 1-dimensional Bouc-Wenwhich is realistic ¥vhen the shear band is deformed at largevelocity, as it is generally the case in a catastrophiclandslide. Excess pore water pressure and heat would nothave the time to dissipate rapidly, especiaily vhen thethickness of the shear band is relatively lar'ge.We assume the shear band thickness to be constanttype constitutive model (Gerolymos and Gazet.as, 2005)for the hysteretic stress-strain behaviour of the shearband in cyclic loading, (ii) a Cam-Ciay model with aduring the slidin_"_. process. It is noteworthy that theevolution of shear band t.hickness with displacement ishardening rule for' the frictional behaviour of soil beforenot well documented in the literature (Otsuki, 1978; 14 CJEROLY+¥,iOS ET AL.Waterson, 1986; Drescher et al., 1990). It is assumed hereb*05considered. The behaviour before shear band formationis modeled ¥vith a Cam-Clay frictional law (ModaressiLb=05et al., 1995). In that stage, volumetric strain rate is alsoconsidered. Eventually, the hysteretic stress-strainbehaviour of the shear band is described ¥vith a BoucWen type model such as the one presented by Gerolymosand Gazetas (2005)..bson=1Mode! ,fol' F/'ictiona! BehaviourA versatile one-dimensional macroscopic model isutilized to describe the shear stress-strain relationshipinside the shear band. The model is capable of reproduc-Fig. 4.versus normalized displacement u/ul curves for differentvalues of parameter n for monotonic louding and different b valuesfor unloading-reioading h,.Tsteresis loopsing an almost endless variety of stress-strain for'ms,monotonic as ¥vell as cyclic. Based on the originalproposal by Bouc (1971) and Wen (1976), the model ¥vasextended by Gerolymos and Gazetas (2005) and appliedto cyclic response of soils. A simple version of the modelis briefly outlined here.The shear stress r at a particular time t is expressed as:r(u( t )) = r.(u( t ))(u( t )) ( I )Equation (6) implies that the ratio r. /uv is the initial stiff-ness of the shear band (in units of kN/m3). From Eq. (i)it is obvious that the ultimate shear strength, r+, isreached when tends to 1. For monotonic loading themaximum value of ( is obtained by settin_9: d /du = O, andby virtue of Eq. (3) this maximum takes the value:i¥vhere u is the lateral displacement (tangential to thesliding surface), r+ is the ultimate shear strength of soil,and = (u(t)) is a dimensionless "hysteretic" parametercontroiling the nonlinear response; it is expressed ¥viththe follo¥vin_ differential equation:dI - l-=- b - i 1'"+(1 -b) du I ) JI [[4(_(*,** I = I (7)From Eqs. (3) and (7) it is obvious thattakes valuesbetween - I and I .Parameter n governs the sharpness of the transitionfr'om the linear to the nonlinear range, during initialvir*'in loading. It ran*'es from O to eo , ¥vith elastic-perfect-d t/(2)ly-plastic behaviour practically achieved ¥vhen ll takesvalues *"reater than 10. Values of n bet¥veen 0.6 and 1in ¥vhich: tt is the lateral velocity; uv is a parameter signal-have been found to better fit experimental resultsing the end of elastic slip (a rigid plastic behaviour is ap-(CJerolymos and Gazetas, 2005). Parameter b controls theshape of unloading-reloading curve. Its range of values isbetlveen O and I . When b =0.5 the stiffness upon loadin_"*.d tproximated by assuming a very small value of u*, say lessthan < 103 m). n and b are dimensionless quantities thatcontrol the shape of the hysteresis loop. Equation (2) isobviously of a hysteretic rather than a viscous type.Hence, its solution is not frequency dependent. Byeliminating t, it can be rewritten in an incremental d -duform:dcI {1-1 i"[b (1 b)slgll (u )]} (3)dt/ u)By differentiating Eq. (1)displacement u:vith respect to the lateraldr dduand obviously that ¥vhenr), du (4)tends to O. Eq. (3) reduces to:parameters, the reader is referred to the recent publication of Gerolymos and CJazetas (2005).The shear strength T. is given by a Cam-Clay frictionlaw ¥vith hardening rule (Modaressi et al., 1995),appropriately modified to be used in conjunction with thehysteretic Bouc-Wen model, and Terz,aghi's effectivestress principle:r+ = !lF(T,'* (8)du u+in ¥vhich /1 is the mobilized friction coefficient, expressedSubstrtutmg Eq. (5) into Eq. (4) one obtains:dT r. _o uc!ureversal equals the initial tangent stiffness, and theMasing criterion for loading-unloading-reloading arises.Monotonic loading curves for different values of ll arepresented in Fig. 4. Hysteresis loops of the parameterversus the normaliz,ed displacement u/u. for selectedvalues of h are plotted in the same figure. For moredetails on Eq. (2) and calibration of the associatedin terms of Coulomb friction an*"le in direct shear:(6)/! = tan q? (9)and SHEAR BAND lvIODEL15is bein_._O formed, at approximately u=0.01 m, the rate of'o evertical displacernent is practically becoming equal tozero.As described in the introduction, the mobilized frictiono e4:coefficient /! is a function of both displacement and¥'elocity. It can be approximated by the follo ving set of'o 02equations:O(a) oo 02c olo Os/t = min {min [(t< to)l/! =! l+ 1-1!r e "uOG04lico ee03p (t = tO) }(14)(15)Ilc* Pc+0.0e02//r _1! , d+ I /1r,de _P'O GeO1( 1 6)ktr,s flr,s /tr,sO-O ) O1where v*0.0002the criticai state, residual, slo v residual, and fast residual-O G 03(b)oo 02o olO 03(= Lt) is the velocity, and ,1* , pl*, p*,= and /1*,d arefriction coefficients, respecti¥'ely. The residual frictioncoefficient pl*, varies bet veen the two extremes: !/*,* andf/, d. The parameters a and control the state of softeningFig. 5. (a) Shear force-tangeutial displacement and (b) normal versustangential displacement, computed with the developed Bouc- Ven-and of rate-softening/hardening of the frictionalCam-Ctal.' mode] (Model parameters: n= 1, b=0.5, k=0.2, ;.=tional sof'tening is irreversible, so it is not recoveringduring cyclic sliding. In other ¥vords, the value of the4000, (1,;0=0.1 MPa, (1*0= 0.3 MPa, and ep= 25')(T,'* = (7,;o(1 - r*), /'= P (10)a,',aresistance, respecti¥'ely. Equation (14) indicates that fric-mobilized friction coefficient /! is computed as theminimum bet¥veen the value of p at current time step(t= to) and the minimum value of p during the previoustime steps (t<to). The critical state coefficient p.. isdefined for a possible state, in which shear' is at constantwhere o',;o is the initial effective stress normal to the shearvolume but with random particle orientation, ¥vhereas theband, and rresiduai friction coefncient /1* Is defined for the state in¥vhich shearing takes place is at preferred particle orienta-the ratio of excess pore water pressure pnormalized to o',',o. The term F in Eq. (8) is introduced toprevent the irreversible volumetric strain from increasingunlimitedly on a dilatant slidin*" surface. It is expressedtion (Lupini et al., 1981).The original Cam-Clay model is not valid after thecritical state point (after the shear band has formed),as :F=1-kln cr,', (11)(T*¥vith(7* = cF*oe ;-,, (12)where }v is the vertical displacernent (normal to slidingsurface), k is a shape parameter, and ), is the volumetrichardening parameter. cT*o is the initial critical pressurewhich is by definition one-half of the pr'econsolidationstress. The evolution of vertical displacement is describedby the following dilatancy rule proposed by Modar'essi( 1 995):dw= -tan /+･,,,,,,,,,,,･･････-Til i !dul (13)¥vhereas the proposed Bouc-Wen-Cam-Clay model isvalid even for displacements larger than those required toreach the residual state of the soil. Furthermore, drainedsoil behaviour is assumed before the formation of theshear band. This is true under the assumption that pore¥vater pressures are generated only due to temperaturerise. As it will be shown in the sequence, heat generatedpore water pressures ar'e associated ¥vith large displacements ¥vhich are usually of the order of Im.Calibration of the aforementioned parameters shouldbe achieved through laboratory t.ests (e.g. ring shear).However, a rnethodology is presented herein for relatingthose parameters to key index soil properties or stressvariables (e.g. clay fraction, plasticity index, effectivenormal stress, etc.).a,',in which v/ is a parameter for dilatancy, taken equal tothe mobilized friction anglein this study. Details on thecalibration of the Cam-Clay model parameters can befound on the ¥vork of Modaressi (1995).As an example, Fig. 5 illustrates curves of shear stressand normal displacement versus tangential displacementfor an overconsolidated clay subjected to monotonicshear loading, as computed with the proposed BoucWen-Cam-Clay model. Notice, that vhen the shear bandEquations fo/' Heat Generated Pore Presstt/'eStarting from the principles of mass and energy conservation in a tlvo-phase soil element, Vardoulakis (2000)re-formulated a set of t¥vo coupled equations that governthe mechanisrn of heat generated excess pore-waterpressure. In the limiting case of undrained shearresponse, the equation of pore water pressure generationis:i GEROLYMOS ET AL.16Poisson's ratio v and of C* on temperature, ¥ve (tentative-81ly, at least) assume that they are both independent ofo;oOC ci ytemperature.( ccANotice in Eq. (18) that the coefficient ), is either nuH orpositive, dependin*' on ¥vhether the temper'ature surpassesa critical value e**, and whether the clayey soil is behavingDS:*ah: y OC el3y;: -o 5NC c!ay ..... Ethermoelastically or is collapsing in a thermoplastic_1manner. We also note that Eq. (17) is not valid as soon asvapor'iz,ation takes place. This happens ¥vhen the temperature surpasses the critical value for vaporization, ¥vhichis approximated by the solution of the follo¥vin_g: equation(Vardoulakis, 2002):1*1 sO 40 5O 10e 120O20TemQerEture e 'CFig. 6. Idealized ;sotropic thermal volumetric deformation of anormalh. consolidated (NO, a slightly overconsoiidated and aheavih_ overconsolidated (OC) cla¥.': The following branches aredeutified: OC Clal.': ( ) Heating phase: A-B, thermoelasticex pansion: B-C, thermop]astic contractton anti (ii) cooling phase:C-D, thermoelastic contraction: NC clay: (i) Heating phase: A-F,,tt]ermoplastic contraction and (ii) cooling phase: E-F, thermoelastic contractionlc p = ).**d edt cJt(1 7)in ¥vhich ),* is the pore-pressure-temperature coefficient(in units of stress per temperature) given by the followingtwo-branched expression:},OeJ ,;Lm:::; Cecr(18)e_rvep+ v +Ceec*(7,,o (62e+16926) exp ) - 4650(20)Oe + 273In the limitin*' case of adiabatic loading conditions thetemperature profile inside the shear band is considered tobe uniform and only variation ¥vith time is assumed. Inthis case the governing equation of heat generation is:deDdt 1j(pC)(21)¥vhere j ( = 4.'_ .J/cal) is the mechanical equivalent of heat,and (pC) represents the specific heat multiplied by themass density of the soil-¥vater mixture. Picard (1994)proposed thatj( pC)m = 2.85 MPal'C,Eq. (19) below. In this limit the shear band boundariesfor ¥vater-saturated clays. D expr'esses the r'ate of mechanicai vork due to frictional heatin : of the soil inside theshear band. By neglectin*' all dissipation in the fluid, Dcoincides with the rate of ¥vor'k of the shear stress deform-are pressure-shock surfaces and it is meaningful toing the soil skeleton:¥vhere ( :: and (x. P are illustrated in Fi_9:. 6 and c is given inassume that the excess pore-¥vater pressure p is uniformlyD = r,, cdistributed along: the thickness of the shear band. In(22)other ¥vords p is only a function of time.As illustrated in Fig. 6, the thermal volumetric strain ina drained heating test under constant isotropic stress,may be expressed as a bilinear function of temperature.Since preconsolidation stress is also a function of temperature, the bilinear behavior is only an approximation. c :is the slope of the volumetric thermal strain-temperature(g) curve, associated ¥vith thermoelastic expansion ino¥'erconsolidated clay and with thermoelastic contractionin normally to slightly overconsolidated clay. Similarly,(x:P is associated with thermoplastic contraction in bothin whichis the rate of shear strain measured after theshear band formation. The shear strain y is expr'essed as afunction of lateral displacement u and shear band thickness dboverconsolidated and normally consolidated clay.The parameter c in Eq. (18) is the oedometric compres-active only after the development of shear band.sibility of the ¥¥'ater-saturated drained soil, approximated(after some algebra) by:y = <z! - u*> (23)c!b¥vhere u*+ is the lateral displacement at critical state(corresponding to zero rate of volumetric strain). Thesymbol < ･ > in Eq. (23) are the Macaulay brackets:<x> = x, if x : O; <x> = O, ot/1e/'Tvise. Therefore, Eq. (21) isEVOl,IJTION OF SHEARING RF.SISTANCF.DURING SLIDING1c (1+ v)eo cf (19)3 ,,oIn i(1+ O)As elucidated in Fi**. 7, the sliding process can be divided into the follo¥vin*" three phases.¥vhere v is the Poisson's ratio of the soil skeleton under(a) Pre-shear-band bellaviou/': The behaviour of thefully drained conditions, e. is the initial ¥'oid ratio of thesoil at first shearin*' should follo¥v the path A-B-C insoil, and C* is the re-compression index in a reloadingcycle, assumed here for simplicity to be identical to theFig. 7. The peak stren*'th is mobilized at the veryearly stage of displacement, and then drops to the"s vellin*"' index in a unloading cycle. Due to lack of anycritical state, triggering the creation of shear band.significant information on the dependence of theBeyond this point, the volumetric displacement is 17SHEAR B、へND MOD薮LP鷲 溺国τ二） C藷蕪壽弘・1磁：心 、F、B憩＼C俄ボq3i5【猷韓〔τo．）ら 語綿ε＝訟鴬of 丁c ＿』τ貿∠二1τツ，，．、、鋸鴇，．抑．．㎡壽鰍爾 r or 噛￥9譜Fρ「暫5sur奪 rさ壱Fas象噂S ／ D芝 ⑳みごりるに ロ きヒ むさヨぬ（b〉 lτヨ財“『3（1−P偏） c心∫ 欝r3コレ》n 〔c、】A置 篇D15p泊qe爬nヒ uFig、7． Idealized evolu重ion of the mobl旦ized shear b謎nd res韮s1ance duri翻9 Ihe shd童ng Process： lhe fo“owing P貰肇ases are idenI董6ed： Prε一5hεαr一加ηゴわ8hα｝・iαθ倉：ApB脚C，Mα勘・1α1∫oゾ’θノ∼〃∼g；C−D，and r1∼θ’7ηo一ρo’じo−1ηθch側’cα150ゾ’θπin8＝D・￡ I I 鐵 雛・ 鑓彦 灘 謙壽 C糖1 直論犀丁翔1高） C凋ダ Fr鵡n IC7（al銀 黛 ・ 、、 ／＼ z・ク 榎 ’N、〆づ数レ■（c）↑↑C． assumed to vanish．The so主I be致aviour in this pぬase 7㌣齢h is governed by Eqs。（1），（2），an（i（13）．（b） Mα1θ1’iα15砺∼εηing： During this phase，the evolu−Fig，8． Schem飢ic 飛usIr飢ion of mu紅i−layer perceptron neura畳 tion of she＆ring resistεしnce玉s depicted by pat｝1C−D． ne霊worksdevebpedforcorrelaIionofthemodeiparame重ersw髄量1 The material insi（ie the shear band is fl甲ictionally softening dueto s宅ra呈nandstrainrateincrease（ifthe key i聡dex soil properIies；Ail重hree neIworks consist of重葦1ree Eayers withthehyperbolictangenねs錘1etransfer“acIiv飢lon”釦臓c芝ion of their neurons material ex紅ibits Ilegative rate e狂ect）．丁銀s frictional softening is accompanied by temperature rlse．The soil behaviour ill this phase is governed by Eqs．（ユ）， （2），and（14）．（c） Thθ1●〃10一ρ01’o−117θchα11icσ15砂1θnillgl This phase，Iayers，is schematically i11ustrated in Fig．8．As shown inFig．8（a），the input Iayer comprises two illput neurons（1n凱2）representing the followi119Parameters（pattems）： corresponcl圭ng to patぬ D−E，starts as soo…1as the ●竜he clay fraction CF，and temperature lnside the sぬear band surp＆sses a 。毛he clay act量vity／1 cri重ical value、Beyond this critical po玉nt，hea重gener−The lat￡er is related to plasdcity index lp： ated pore water pressures deve至op，caus圭ng further1P＝！4CF frictional softening． Eventually a residual stead》7 state condition is I’eac員ed，because： ・excess pore 、vαter pressures c＆nnot exceed 重he lnitl＆l e仔ectlve s重ress，σ看o，and（24）丁紅e “hidden” 1＆yer of the network consists of虚reeneurons （h漏3） arld the output 圭ayer of olle lleurol1，representing the s玉ow residual friction ang玉e ψ「，、． The 。ぬeat genera重ed pore water pressures dhn圭nishhyperbolic tangent function1s used as the‘‘activatiol1” graduallyduetofriαionalsoftenlng． The mecbanisms of this phase are govemed byac短eved with repeated重rials，using the mathematical E（ls、（1），（2），（17），and（21）．Phases （a） a11（i （b） are respons呈ble for the lands豆ide重riggering，but they also inHuence its evolution．On thecontrary，phase（c）a鉦ects only the1εしndslide evolutiol1；it is the major destabilizillg factor that con重ributes toaccelerated“c罫eep”andmaytransformaslopeinstab圭1−ity to a cεし芝astrophic landslide。function of al壼neurons．T1ηiniηg of the neural network iscomputer code MATLAB．The lnpuωata base used for tbis重raining，collsists of results from ring shear tests such asthose of Tika et aL（1996），Tik＆a勲d Rutchinson（1999），Lupini et aL（1981），Skempton（1985），Bishop（197i），andMoOre（墨991）． The mathematical formulation of the neural networkafter the tra量ning，is expressedεしs：＠・・一t ［蕩 h（激｝ヅ1醐）＋わ2］（25）CAL豆BRAT豆ON OF MODEL PARAMETERS A methodology is presented for the caiibration oギ由emo（1el parameters by utlllsing experimental data from the正iteratuIle．The nlethodology is based on correlatiHg wit封where w1，，ノand わ11are the weights and biases of thehidden layer，and w2，andか2the weightsεしnd biases ofα1eoutput layer，given呈n Tab豆e I．刃ノis the nom1εdized inputkey index soil properties，by means of arti最cial neur＆Ivector wlth respect to the minimum v＆1ues of the problemnetworks．parameters崎・（xlr4，x2；CF）．喝・isexpressed＆salinearfunction ofλr／according to：Pαノη〃1θ！θ1’56ゾFヂio！ionα1S〃ηin S（ガン∈∼11ing Aso−cαlled“multilayerperceptron’ラ（MLP）networkfor func｛ion apProximation was developed to correlatethe slow residua玉friction aロ91eψ，，、with key index soi至 拘㎜mm笛 喝篇2 ． 一1 （26） max濁一mm笛properties．丁紅e reader is referl聾ed to the MATLAB userラsThe（min，max）v＆lues of parameters x／are（O．4，4）and（0，80）for14and CF，respectively．The capability of them段nual for details in neural network anα1ysis（theory andneur＆l network 茎node星to ‘‘predict” the slo、∼・residualterm呈nology）、The neural ne￡work，consisting of threefrlction angle ofthe various experiments is demonstrated GJEROLYMOS ET AL.18Table 1. ¥Veights and biases foF the slow residual friction angle ep*_sOmput layerHidden layerbl,l,' 1,J1b2t')-i075'!O,254 O,747- 2 1 O,713,407 20_94 l5'Fl ,555- O.2083. 149- 5 009 O 435 O ;S(!)OTable 2. T)picai displacements at various stages of shear in intactclays having CF>30a/o and at (T,;0<600 kPa (Skempton, 1985)Displacement: mmStageO-C_ NCPeak 0,5-3 3-6Rale of voiume chan_ e approximately zero 4-lOAt30)_OO*.+ Io1 OO- 500Siolh' residuai ep*O 02 03 0405O1G6Dispi30ement I mFig. 10. Slolv residual friction coefficient ratio (norma ized with thefriction coefficient p*, at critical void ratio) versus displacement:Comparison betlveen me8sured in ring shear apparatus and computed behaviour, for a=67: The ex perimeutai points taken fromTika and Hutchinson, 1999, correspond to Vaiont clal.' vith plasticrtl.' index I, = 22, cla¥_ fraction Cr=30, effective normal pressure (T,'*o=0.5 MPa, and criticastate frtction coefficieut p*, =0.4840d A=075* 1 2e, 351'cA=15*43; 30aIF25O A=0*0820,,,5"aOAAo A'.; Ae. 5u,Oo20 40 50Jfioi1$ogjstic8e1 OOSigmoidClay fr ction C*Fig. 9. Sto v residual friction angle versus cla .' fraction and clay activi*/r' '; ';S*: '#*t)': Comparisou bctween experimental data and the arrificiai neuralnet vork approximatton: Data points taken from Tika et al., 1996;Tika and Hutchinson, 1999; Lupin et al., 1981; Skempton, 1985;Bishop et a ., 1971 and Moore, 1991in Fi . 9.The subsequent task is to calibrate the parameter Oi ofEq. (15) that governs the transition from critical to slo¥vresidual state. Skempton (1985) proposed typical valuesof displacement at various sta*'es of shear in intact clays;they are given in Table '- and are valid for clay fractionshigher' than 300/0 and effective normal pressures (7,,o lo¥verthan 600 kPa. These values are consistent ¥vith resultsfrom rin*' shear tests on sand-mica mixtures conducted byLupini et al. (1981). Note that, the displacement requiredto reach the slo¥v residual friction coefficient was 30 mmfor soil specimens exhibitin_g: turbulent shear mode, 100mm for transitional shear mode, and 400 mm for slidin*'shear mode. Evidently, the ma*'nitude of the effectivenormal stress (T,',o and the presence of structural discontinuities also ha¥'e a si :nificant influence on the shearbehaviour of clays. The reader is referred to the lvorks ofSkempton (1985) and Luplni et al. (1981). Figure 10compares analytical [computed ¥vith Eq. (15)] versusiaboratory (ring shear test) results for the Vaiont clayt,aken from Tika and Hutchinson (1999).A neur'al network ¥vas also developed for a shear modesoil classification (Fi**. 11). In this case the net¥vork,(,, .･･* ･;= )tanhiFig. 11. Schematic illustr tion of multi-la¥.'er perceptron neuralnetworks developed for classification of cla¥_ s according to shearmode behaviour and rate effect on residual strength, in terms of theclay fracrion: The networks consist of three la .'ers vith tl]ehyperbolic tangent and logistic sigmoid as tire transfer functions ofthe hidden and output neurons, respectivel,.,consists of one input neuron representin*' the clay fraction CF, t¥vo hidden neurons, and three output neurons,each corresponding to one of: turbulent mode (TU),transitional mode (TR), and sliding shear mode (S);"tar*'et" values are I for the correct class and O otherwise. The prediction of the neural net¥vork after training,is plotted in Fig. 12. Values bet¥veen O and I represent theuncertainty of the network prediction. Accordin*' to theresults, the possibility of a clayey soil to exhibit tur'bulentshear mode is high for CF<,200/0, Io¥v for 200/0 <CF<400/0, and z,ero for CF>400/0. In the same way, the possibility for transitional shear mode is lo¥v for CF<20010, SHEAR BAND19ivIODELlis,) 15' > ;"I '5 08"' :'1'"'F5 04e; 05oo20 40OCl y fr ction C=O80 100Fig. 12. Shear mode potential versus cla, fraction, computed withartific al neurai network anal Isisooeoe= l r)o aeu)ooaorlO naoiveo oOo8o20 40 8080100C[ y fr ctien CFI 9Fig. 13. Correlation of fast residual friction coefficient ratio (normalizedvith the slolv residual friction coefficient /i*.*) with clay frac-tion: Comparison between experimental tlata and artifieial neuralnetwork approximation: Data points taken from Tika et al., 1996high for '_Oo/0<C'F<400/0, and zero for CF>400/0.and Tika and Hutchinson, 1999Finally, the possibility for sliding shear mode is zero forCp < 400/0, and high f'or CF>400/0 .2As mentioned in the introduction, the slo¥v residualstrength depends also on pore ¥vater chemistr'y and- ieffective normal pressure. Unfortunately, theseparameters have not been incorporated into the proposedrnethodology, due to insufficient information provided byscarce experimental data.Several researcher's have sho¥vn that the critical statefriction angle ep*+ correlates with the plasticity index evenif with substantial scatter. One such relationship (¥vithlarge correlation error) has been proposed by Mitchell( 1 976) :,.* arcsin0.6 - O. 14 Iog (Ip- 5) J (27)In pre-existin*' shear surfaces ¥vith large clay fractionEq. (27) overestimates *.. Therefore, Eq. (27) is validonly for intact clays. A value of * close to the slo¥v*,= is more realistic when reactivation of an old landslide is anticipated.O:l 15 05OoO 08O 04o 12Ve[ocity : m / sFig. 14. Fast residual friction coefncieni ratio (normalized with thefriction coefficient p*, at critica! void ratio) versus vetocitl_ .Comparison bet,veen measurcd in ring shear apparatLis andcomputcd behaviour, for P=310, 20, and 452. corresponding tonegatl e neutral, and positive rate effect, espectively. Theex perimental points are from Tika and Hutchinson, 1999residual friction anglePa/'ameters oj' F/'ictiona! Strain-Rate BehaviourMultilayer perceptron neural net¥vorks were de¥'elopedfor the calibration of the viscous parameters of the model/1,,d, (Fi**. 8(b)) and(Fig. 8(c)). The latter, fi, controlsthe sharpness of the transition from slow residual to fastresidual state. The fast residual friction coefficient ratiord=pl,,d///,.* is correlated solely with clay fraction CF,¥vhereas fi is computed as a function of the effectivenormal pressure a,{o, clay activity A , and clay fraction CF.The computed parameter /1*,d is compared in Fig. 13, ¥vithexperimental data of Tika et al. (1996) and Tika andHutchinson (1999). Figure 14 demonstrates the agree-80) for a',;o, A and CF, respectively.In addition, a neural net¥vork was developed for soilclassification according to the rate effect on residualstrength. The output layer of the net¥vork consists ofthree output neurons, one corresponding to each class(neutral, negative, and positive rate effect), and targetvalues of I for the correct class and O, otherwise. Theprediction of the neural net vork after the training, isplotted in Fig. 15. According to the results, the possibilityfor neutral rate effect is high for CF< 100/0, Iow for 100/0< CF<200/0, and zer'o for CF> 200/0. The possibility forne*"ative rate effect is zero for CF<80/0, high for 80/0< Cp<400/0, and lo¥v to medium for Cp>400/0. Finally,the possibility for positive rate effect is zero for Cp < 400/0,ment bet¥veen measured (ring shear apparatus) andand medium to high for CF>400/0.computed [Eq. (16)] fast residual friction coefficient ratiofor' a wide velocity range. C'.alibration of fi ¥vas based onPol'e-Pressure- Tempe/'atu/'e Coefficien tthe neural net¥vork analysis. The expressions derivedLittle information is available for the pore-pressure-after training of the neural network are of the same formas Eqs. (25) and (26). The " veights" and "brases" of thenetwork layers are given in Tables 3 and 4, for the fastresidual friction coefficient ratio rd, and the parametertemperature coefficient, ). . Experimental data takenfrom Sultan (1997), Sulem et al. (2004), Baldi et al.ft, respectively. The (min, max) values of the input(1 991), Plum and Esr'ig (1967), and Laloui and Cekerevak('_003), identify the parameter ).* as str'ongly dependenton overconsolidation stress ratio OCR. Typical values ofpararneters xj are (O. 177 MPa, 0.98 MPa), (0.4, 4) and (O,(x:P (see Eq. (18)) for a norrrrally consolidated clay I .343GEROLYlvIOS ET AL.20Table 3. ¥Veights and biases for the fast residual friction coefiicient ra-overconsolidated clays are in the range of O.5 x 10-4 .C_- ltio rto I .5 x 10-4 .C-i. As sho¥vn in Fig. 6, the elastic thermal=/lr.d /p*..Hidden laverblIt' l,. J- I- 182,149¥vater pressure p. Ho¥vever, due to insufficient information pro¥'ided by scarce experimental data, it is considered as a constant in all the subsequent analysis.l 214526is a function of the overconsolidation stressratio OCR, ¥vhich in turn depends on the excess por'e-b2tiT)_ll . 0445- 1 97 87)_coefficient ceOutput layerO.418Critica! Tel7rpel'atureCritical temperature, e*,, is the threshold for ther-Table 4. ¥ reights and biases for parameterftHidden layerOutpll iayerIt'2i b2bl,l 1' ll,J- 7.408- S.556- 15 298-2)__158= 9. '_4 I6,601lO.8967.84868.73256^857O,31650 415-6 615= I .796moplastic "co!!apse" of an overconsolidated clay.Exploiting experimental data from Sultan (1997),Vardoulakis (2002) proposed the following expression forecr as a function of OCR:O '_02- 9 57 l?_6_444- 2 1 .4927 434l02 301[ OCR - 1420.6398.013ec*400 + 600 [ I - exp 10255 . 895¥vith- I .286OCR (T'fo (29)a,,o2PCon7p/'essibi!ity Incle_1'There is lack of information of any dependence ofthe recompression-s¥velling index, C*, on tempera-e, 08ture-hence our assumption is that C* is independent of04e. Based on the modified Cam clay. model, Wroth andcWood (1978) sho¥ved that C* can be obtained as a funceOtion of the plasticity index:20 40 eO80 100C! y r c ien CFC,= 37Po (30)IFig. 15. Rate effect potential versus cla .' fraction, computed lvitl]artificial neilral network anai .,sisSllea/' Band Thickl7essm*' functlon of OCR Results from drained thermalThe shear band thickness, db, is a critical modelin*'parameter, as it makes the strain-dependent Eqs. (17) and(21) of heat generated pore pr'essures compatible with thedisplacement-dependent Eqs. (2), (13), (15), and (16) ofthe viscoplastic frictional behaviour.loadin*" of illite (Plum and Esri_9:, 1967) and of Boom clayspecimens at constant isotropic stress (Baldi et al., 1991)indicate that the thermal volumetric strain vanishes ¥vithmicroscopic structure of shear bands in Kaolin specimensin direct shear tests, and also proposed that the shear-increasing OCR, reaching zero at OCR=2. Vardoulakisband thickness can be estimated as a function of the('_OO'_) proposed an empirical correlation bet¥veen theparticie size dso, according to;(OCR= 1) are in the range of 1.5x lO4 .C i to 2.5><1 O4 .CI . For slightly overconsolidated clays(1 < OCR< 3) the coefficient a:P appears to be a decreas-Mor*'enstern and Tschalenko (1967) documented thecoefficient oe P and OCR for o¥'erconsolidated clays, utilis-c!b * '_OOd50 (3 1 )ing experimental data from Sultan (1997)::plO3; exp- (OCR12- 1)aiAs a matter of fact, Eq. (3 l) is considered to give a lo¥ver[oCll'bound estimate of db. Results from back analysis of thewell-documented Vaiont landslide, indicated that valuesof db in the range of 0.1 m to 0.2 m are quite reasonable¥vithOCR = (Tnoano(28)P(Vardoulakis, 2000). Such high values are justified if veassume that the active shear band thickness increases inthe course of slidin :Notice in Eq. (28) that (x:P is not a constant but a functionof the excess pore-water pressure p.The elastic thermal coefficient ais estimated to beabout 5 to 10 times smaller than the elastoplasticNUMERICAL FORMULATION OF THF, SHF.ARBAND MODF.Lcoefficient ai:P in normally consolidated and slightlyThe system of differential Eqs. (1), (?_), (13), (17) andoverconsolidated clays. Hence, typical values for' (x: of(21) describes mathematically the deformation of the SHEAR BAND lvIODEL'Table 5. List of materials and model parameters used in the anall05sisof shear band d .'namic deformation(a)oCase srudyParametersClay mineralA I A2Shear modeTRSRabe effectNEGPOSCF (0, )3070A0.4O_4c*, (deg)2S24c* , (deg),-5136* d (deg)16i7C,O.032O 075cKaoliniie(ommoriilonite Montmorillonite ' HliteTRiNEG =SPOS02, TRMontmori loniteiNEG= , 304i 8 41 0.95 267030zo16 50.32 i O.073eeO.22l, (O.2, O 5, 2, 5)o a5 i152, 5322s3urn(b)08O. 75a;,o (h,IPa)OCR04B2BlKaollnite Kaolinite21nte. Kaoiinitoel*5Montrno l:onitee4O."_)eo ('C)e*.p ('C)a ('Cu*l)(m)db (m)1002ISo, (1,_4, 154, 210, 256)7.4 Io ,<o oo_ooi5, (O.Ol, 0.05, O 1)ko.ol;.4aoOo100O osiSu mKao niie80e,nib0.5u. (m)O.OOl6040Only for case C*Montmorll on teH(c)20:: eefshear band. An explicit finite-difi rence algorithrn hasbeen developed for the solution of this system. TheG1algorithm ¥vas incorporated into a computer code, Dsc-LANDSLIDE (developed under the frarnelvork of theresearch pr'oject LESSLoss, 2005), for the analysis ofearthquake triggering and evoiution of catastrophiclandslides.a 05115,253253Um(d)08K ol niteo; oe( 04MontmoriiioniteSHEAR BAND DYNAMIC DEFORMATION:ANALYSIS AND DISCUSSIONThe developed model is utilised to study the dynamico* 02O/ _lo 051ISdu: mdeformation of a shear band in clay-rich material subject-ed to a constant velocity of v=0.1 m/s. As alreadymentioned in the introduction, at such high velocity thefast residual strength ¥vill be fully mobilized. Four casesare considered of varying clay mineral and clay fractioninside the shear band:･ kaolinite ¥vith Cp= 300/0 and CF= 700/0,' montmorillonite with CF= 300/0 and CF= 700/0.The model and material parameters used in each case aresumrnarised in Table 5. Their calibration was based onthe aforementioned neural net¥vork methodology. It isstated however, that there are no available experimentaldata t.o support the validity of the analysis.The computed evolution ¥vith the progress of slidingdisplacement of: (a) the normalized shear stress ratio, (b)the apparent friction coefficient ratio, (c) the temperatureand critical temperature, and (d) the excess pore-waterpressure ratio are plotted in Figs. 16-17. The followingobservations are ¥vorthy of notice in these fi**ures:Fig. 16. Evolution ,vith displacement of: (a) the normalized s learstress ratio tl,r,10, (b) the apparent friction coefficient ratio plp,,,(c) the temperature e (black line) and the criticai temperature g**(gra .' Iine) and (d) the developing excess pore pressure ratio i'( = pl(I o), for cases A1 (Kaolinite with Cr=300/0) and B1 (Montmorillonite with CF=30010): Both soils exhibit transitional shear mode(TR) and ncgative rate effect (NEG)(a) In all cases, montmorillonite exhibited the slo¥verreduction in shear resistance. Although the peakstrength of montmorillonite is about 1.5 timessmaller than that of kaolinite, its mobilized shearresistance after 3 m of sliding is approximately t¥votimes larger than that of kaolinite when negativerate effect is involved and thr'ee times larger whenpositive rate effect is considered. The "ductile"shear behaviour of montrnorillonite, or the (more)"brittle" behaviour of kaolinite, is attributed to thefollo vin*' reasons: CJEROLYlvIOS ET AL.22051oO.e; 0.5(a)- 0404Kaoi niteS 030202*Montmori[ oniteC O1e,EZ:< OoO151103G2040sou mi08Fig. 18. Evolution of apparent friction coefficient ratio plp*. Ivith(b)displacement for values of initial effective normat pressure a 0=0.2, 0.5, 1, 2 and 5 MPa (Case C: I]lite lvith C_F=309/0)06Montrnorillonitev 04a further de-acceleration of the shear strength?: 02(b) The displacement u** at ¥vhich thermo-poro-mechan-softening.< O1 Oo15 25 3O 0580the landslide evolution, displacement is computed to(c) The infiuence of rate effect (positive or' negative) onthe evolution of shear resistance dur'ing the thermoporo-mechanical softening phase, is negligible in the6040case of kaolinite, but appreciable for montmoril-Montmorl on't's20(c)e = oc'05115u m1(d)and the shear band thickness d!' on the evolution of acatastrophic iandslide. The case considered is that of ashear band rich in illite with clay fraction CF=300/0,Kaolinite06, 04CL 02Montmori lon'teo oslonite.Parametric analysis ¥vere also carried out to investigatethe influence of the initial effective normal pressure a,;ooOthe rate effect on residual strength This critical, forbe appr'oximately 0.5 m in kaolinite and 1.4m inmontmorillonite.Kaolinite08ical softening is initiated, is practically unaffected by15 2 25 3ummoving at a constant velocity of z; = O. I m/s. The modeland material parameters used in the analysis (case C) arepresented in Table 5.Figure 18 illustrates the evolution of the apparent friction coefficient ratio ¥vith slidin*', at four levels of initialeffective pressure (T,,o (=0.2MPa, O.5 MPa, I MPa, 2MPa, and 5 MPa). It appears that the displacementFi**. 17. E,volution lvith displacement of: (a) the normalized shearrequired for temperature "explosion" decreases ¥vithincreasing (7,'*o In other words, the shear behaviourstress ratio r/(T e, (b) apparent friction coefi cient ratio ///p*., (c)becomes more brittle at higher values of (T,{o, increasingthe temperature O (black line) and tl]e critical temperature g*. (gra .'line) and (d) the developiDg ex cess pore pressure ratio r* ( =pl,f o),the potential of a catastrophic landslide. It is alsofor cases A2 (Kaolinite with CF=700/0) and B2 (Montmorillonitevith CF=70010): Both so ls ex'!]ibit sliding shear mode (S) andposit ve rate effect (POS)mentioned that the evaporation limit e*,p was not reachedin any of the cases. Figure 19 elucidates the displacementrequired for thermal "explosion" as a function of theshear band thickness clb, for selected values of initialeffective normal pressure cr,',o. It is demonstrated that at･ The small residual strength of montmorillonite,lo¥v levels of (T,'*o ( = 0.2 MPa), the mechanism of thermo-mobilized at the very early stage of sliding, resultsporo-mechanical softening ¥vould only be activated if dbin a si**nificant reduction of frictional heating¥vhich in turn slows down the excess pore-wateris of the order of felv millimeters. At greater values of (7,',opressure generation, and thus the shear stren*･threduction.heat generated pore pressures may rise even for the･ The larger compressibility of montmorillonite,the index of lvhich (C*) is an order of magnitudelarger than that of kaolinite, results in a smallerpore-pressure-temperature coefficient, Ieadin･ to(in excess of 2 lvlPa), ho¥vever, thermal "explosion" andextreme case of db= O. I m. It is noted, that Vardoulakis(2002) estimated an average value of a,{0='-.38 lvlPa asrepresentative for the Vaiont landsllde.The capability of the model is further demonstratedthrough analysis of the shear band response under cyclic 23SHEAR BAND ¥. ,10DELO105o 080 S* 006O1:, 004S, -Oi25{!)o )25- * = e 2 JPo-o sO 5 25 30 3S10Dlspl-O.s2015eement required fer t$mrature "exp:osior,' I･O 25 O O 25DisplacemEnt u :o.sTllFig. 19. Curves of shear band thickness db versus displacementrequired for temperature "explosion" (initrat on of pore waterFig. 21. Example of the effects of oscillaton. ioading: shear stress ratioversus disp acement h)'steresis toops (Casc C: Illite with C F= 300, ,dh= 0.0015 m, a,;o = I MPa)pressure rise) for vaiues of ini ial effective normal pressure c,;0=0.2, l, 2, and 5 MPa (Case C: llite with CF=300/0)1Oeo04oS- a204(a) OF:s oi2c-o 2c3oO 4*o 5-O 2S O O 250.5Dlsp!aoementu m-a 5o1234Fig. 22. Example of the effects of oscillatory loading: evolution of thefriction coefficient ratio with displacement (Case C Illite with CF =t seciO30 ./., db=0.0015 m, a,'rt = I IMPa)s10 1Eo1 O 03)> _5e) Io.ese.04-1 OO1234s1 o. 02t I s80Fig. 20. Example of the effects of osciilator) Ioading: imposeddisplacement and vehociry time histories (Case C: Illite with Cr=10-O 5-0,2S O 0.2505Dis lacement u : m300/0, db = 0.0015 m, e ,,o = I MPa)10ading. The shear band is subjected to a displacementtime history of incr'easing amplitude ¥vith time. TheFig. 23. Ex'ampie of the efrects of oscillator, IoadiFrg: evolution oftemperature with tlisplacement (Case C: Illite with C '=300!/., db =0.0015 m, (T o = I MPa)imposed displacerrrent and resulted velocity time histor'iesare portrayed in Fig. 20. The material and modelparameters used in the analysis are those of case C(Table 5). Unfortunately, according to the authors'knowledge there are no relevant experimental results inthe literature to compare ¥vith the prediction of theorientation has occurred, the shear resistance becomesinsensitive to loading history (Lupini et al., 1981).Fi**ure 23 sho¥vs that the temperature rise is practicallynegligible, meaning that heat generated pore pressures inthis case of cyclic loading do not develop even atmodel.velocities as large as 8 m/s. Such a value for velocity is farFigure 21 portrays the shear stress r'atio-displacementhysteretic loops. It is observed that the shear strength isprogressively de_ :rading lvith cyclic loading reaching anultimate level, which is the f'ast residual strength. Thecorresponding evolution of the friction coefficient ratio isdepicted in Fig. 22. Notice that, the shear strength is notrecover'ing at any time during loading, in agreement ¥vithlaboratory results sho¥ving that once preferred particlelar*'er than those developed in a stron*' seismic motion(which only rarely reach 1.5 m/s), revealing indirectlythat thermo-poro-mechanical softening is associated onlywith the high speeds developing in the course of sliding,driven by gravity for'ces; even if the triggerin_ : of suchsliding was provided by the seismic shaking-aphenomenon reminiscent of liquefaction-induced flo v ofslopes: the seismic shaking strains the material and high GEROLYiviOS ET AL24excess pore-water pressures develop leading to iiquefaction. But only if the residual strength of the liquefied soilis overwhelmed by the gravity-induced shear stresses ¥vill"flo¥v" and large deformation take place.CONCl,USIONbehaviour of Boom cla¥.' and clay-based buffer materials. Repor'!EUR J3365, Cornmission of he EuYopean Communities, NuclearScience and Technotogy.3) Bishop. A^ ¥V , Green. C. E^, Garga. V. K,, Andresen, A andBro¥vn, J. D. (1971): A nelv ring shear apparatus and ils applicationA constituti¥'e model for rapid deformation of a clayrich shear z,one has been developed utilizing the conceptof frictional softening due to heat generated excess pore¥"ater pressures. The model is incorpor'ated into a novelalgorithm named DSC-Landslide for the analysis ofearthquake-induced catastrophic landslides. A methodology is developed, based on muiti-layered artificial neuralnetworks, for' the calibration of the model parametersagainst published laboratory results. A sensitivity analysis is conducted for the influence of key model parameters(initial effective normal stress and shear band thickness)on the pore-¥vater pressure rise due to increase in temper-ature. The capability of the model is demonstrated in anumerical study leading to some interesting conjectures(1vhich, ho¥vever, are for the moment ¥vlthout experimental ¥'erification):(a) Clay activity has a decisive role in the evolution ofthe landslide: Iarger activity (e.g. montmorillonite) Ieads to less rapid slide.to the measurement of residual stren_ :th, Geotechnique, 21(4),273-328.4) Bouc. R^ (1971): Modele ma hernatique d' hysteresis, Acustica, 21,l 6-2 5 .5) Bromhead, E. N. and Curtis. R. Dalternative methods of measurin(1983): A comparison ofhe residual stFength of LondonC_Ia_v. Crotnld En*"ineering, 16, 39-416) Campanella, R. G. and lvlichell, J. K. (1968): Influence ofempera-ure variations on soil beha¥'ior, J. Soi! IV[ec/1. Fo!nlc!., ASC_E, 94,709734.7) Chang, K. J., Taboada, A^, Lin, ,J L. and C_hen. R. F. (2005):Analysis of landsliding by earthquake shaking using a block-on-slope thermo-mechanical model: Example of Jiuf ngershanlandslide, central Tai¥van, Engineering Geo!ogy, 80, 151-163.8) Despax, D. (1976): Influenc,e de la temperature sur les proprietes desargiles saturees. Docrora! Thesis, Ecole C_entrale de Paris9) Drescher, A.. Vardoulakis, I. and Han. C__ (1990): A biaxiaiapparatus for testing soils* Geo!ecll. Tes!. J_. GTJOD; 13,226-234.lO) Fodi . A , Alotllou, ¥¥r. and Hicher, P y. (1997): Viscoplasticbehaviour of soft clay. Geotecllnique, 47(3), 581591 .l l) Gero ymos. N, and Gazetas, G. (2005): C_oustitutive model for 1-Dcyalic soil beha¥*iour applied to seismic analysis of layered deposits,(b) The influence of the rate effect on residualstrength (positive or negative) on the landslideevolution increases ¥vith increasin_sodium montmoriHonite, Geoteclliliq,!e, 48(6), 787800.2) Baldi> T , Hueckel, A., Peana and Pellegrini, R. (1991):Developments in modeling of thermo-hydro-geomechanicalclay. activity.(c) The initial effective normal stress (7,',o and shearband thickness c/b greatly affect the evolution ofthe landslide, ¥vith greater values of (T,fo andsmaller ¥'alues of db, respectively, resulting inmor'e brittle and accelerated slides^(d) Thermo-poro-mechanical softening is associatedonly ¥vith sliding driven by gravity forces and not¥vlth earthquake-induced loading.Application of the proposed model to real case studies(e.g. the Jiufen*'ershan, 1999 Iandslide triggered by theC_hi-Chi Tai¥van earthquake (Chang et al., ?_005)) wouldstrengthen the validity of the aforementioned conclusions.Soil.s anc! Foundations, 45(3).17_) Habid. P. (1967): Sur un mode de glissemen des massifs rocheux,C_ R. Hebc! Seanc, Academy of Sc.ience. Paris, 264, 151-15313) Habid, P_ (1976): Production of gaseous pore pressu e during rockslides, Rock l lecllanics, ?, 193-197.14) Hicher, P. Y. (1974): Etude des proprietes mecaniques des argiles al' aide d' essays triaxiaux, influence de la vitesse et de ia emperaure, Report Soi! M:ecJ1. Labo., Ecole C_entral, de Paris.15) Hueckel, T and Baldi, CJ. (1990): Thermo-plasiici y of saturatedsoils and shales: constitutive equatious, .J. Georech. En*"rg., 116,17651777.16) Hueckel. T.. Pellegrini. R. and Del Olmo, C (1998): A cons itutivestudy of thermo-elas o-plasticity of deep carbonatic clays, In!. J__,¥r2i,,1. Ana!. " feth Geomech., 22, 549-574.17) Laloui, L. and Modaressi. H. (2002): ,Iodelling of the thermohyd,o-plastic behaviour of clays, H.1'c!romechanica! (vlc! Thennohydronlecllanica/ Bellaviour of Deeo A, i!laceou.s Rock, (eds b .,Hoteit et al.). S¥vets & Zeitlinger, Lisse, 161-17318) Laioui, L_ and Cekerevac, C. (2003): Thermo-plastici y of clays:An iso ropic yield mechanism, Compu! Geotech , 30, 649-660_19) LESSLOSS Integrated R&D Project of the EC_ (2005): RiskACKNOWLF,DC.MENTSThis paper' is a par'tial result of the Projectllvlitiga ion of Ear hquakes and Lands ides. EU sixth FramelvorkProgram, Comract number: GOC_E-CT-)_003-505448, http: //¥1'¥¥'¥ '.lessloss.or_ *.PYTHACJORAS I/EPEAEK 11 (Operational Pro-20) Lupini, J. F., Skinner, A. E. and Vaughan, P,, R. (1981): The_2:ramme for Educational and Vocational Trainin*' II)[Title of the individual program: lvlathematical andexperimental modeling of the generation, evolution and181213,2 ) ¥. {ATL,AB (2000): The Language of Technicai Computing,termination mechanisms of catastrophic landslidesj. ThisProject is co-funded by the European Social Fund (7507lvo)of the European Union and by. National Resources (25070)of the Greek Ministry of Education.RF.FF,RF,NCF,Si) Anson, R ¥V. ¥¥; and Halvkins, A^ B (1998): The effect of calcivrnions in pore ¥va er on the residual shear strength of kaolinite a lddrained residual strength of cohesive soils, Geotecllnique, 31(2),Copyright 1984-2000 The h,1ath¥Vorks, Inc.2,_) i¥,lench, V. (1966): ,Iechanics of landslides vi h nonciFcular slipsurfaces ¥vith special reference to the ¥raiont slide. Geotechnique,16, 330337_3) Mitchel , ,1. K. (1976): Fu,Idalne,1!a!s ofSoi! Bellaviour, John ¥Vile .'and Sons. Nelv York, 4'_224) iModaressi, H.. Faccioli, E., Aubr.¥', D. and Nore , C (1995):Numerical modelling approaches for the analysis of earthquaketriggered landslides, Pr'ocGeorecJ13rd hl!. Co,ifEarthquake Engrg. Soi! DRece,1! Ac!v(7,1ces in,nclnl., St. Louis. ¥i ,Iissouri, Il(IiNVLE.03), 833-843?_5) N,10daressl, H. and Laloui, L. (1997): A thermo-viscoplastic FS懸EAR BANDλ｛ODEL constim｛lve model for clays，1nf、ノ、N‘’〃1．〆4’∼α1、A／αh．Gθo’ηεc1∼、， 21，313−335．26）Moore，R、（1991）：Tぬe cねemical a鷺d斑ineralogical con【rols upon the res1dual strength of pure a蹟d naエura量 days， 0θo∼（∼（〕hη’（1μθ，25 Pressurization，So’Z∫α’1ゴ」Foμn4α’io∼15，45（2），97−108．35） Sultan，N，（1997）＝Etude d目coπ1r）ortementエhermo−mechan玉que de rargile de Boom：exper1ences et modeiisatlon，7ノ∼θ5θ4θOoαorα∫， ENPC，CERMεS，Paris． 4玉（1），35−47、36）T1ka，T．E．，Vaugねan，P．R．andLemos，L、J，（1996）：Fastshear三ng27）Muller，L、（1964）：TherocksHdeinこheVaiontValley，Rocん ofpre−exis【ingsむearzoneslnso員，Gθo’θc11’∼罐e，46（2），197−233， ！、4θご1∼σ耽5五n9〃1θθ”〃∼gGθ0109v，2，王48−212、37）Tika，笛む．E、and Hutchinson，L N。（1999）：Ringsheartes器onsoil28）Muller，L．（1968）：Newconsideraτionson嶽eVaion［slide，Rocん from l騒e Vaio真da息dsiide slip surface，Gθo’θぐノ∼’∼’gど’θ，49（1），59−74． A／θぐhα’∼ic5En9’nεθ1カ∼gGθ0109！y，6，1−9王．38）Vardoulakis，L（2000）：Catasエrop緬clandsiidesduetofrlctional29）Nova，R．（1986）＝Soil models as a basis for modeling由e behaviour heating of tbe fla員ure plane， 1、／ec1∼α’がc5 0ゾ噂Co1∼θ5’v（∼一∫丁’一’c”oπ01 of geop難ysical mater玉als，〆王ασλ∫εchαπiご01，64，31一一44．30）Otsuki，K、（1978）：On由erdaζionslllpbeこwee頂hewidthofl由e shearzoneand由edisplacementalongthefεuk，ノ．0θ0109．Soご． Mα∼θノ』1α15P，5，443−467．39）Vardoulakis，L（2002）：Dynamic由ermo−r）oro−mechanicalanab「sis ofcaこas【ro画dandshdes，Gθαθch吻正’θ，52（3），玉57−171 功ノ∼．，84，661−669．40） Vardo狙lakis， 1． （2002）： Steady shear and therma呈 run−a、vay in31）Plcard，」．（1994）：Ecroisageζhermique des arg員es sa撫r6es：apPlica一 clayey gouges，1’π、1．So1’4∫αnゴ∫’尺’cμ”て∼5，39，3831−3844． ξionaustockagedesd6cねetsradlQactifs，711ゑ5ゴ800α01『α’，1’Ecole41）Voi蜘，B．andFaust，C．（玉982）：Frictionalheaエandstreng由lossin 層ationaie des Ponds et Cha琶ss6es，Paris、 some rapid Iands1五desヲGεo’θchlz’（1μθ，32（1），43−54．32）Plum，R．L．andEsrig，M、L（1967）：Sometemperaturee窪ectson42）Wa［erson，」、（1986）：罫auk dimenslo！1s，dlsplacemem and grow由， soilcompressibiliζyalldporewaterpressure，H’9加の身Rθ5、80αヂ4 Pα9θoρ1義蝉c5，三24，365−373． （Sp、Rpζ），三〇3，231−242．43）Wen，Y．一K、（1976）IMe由odforraほdomv1bra［iono佳ysτeret1c33）Skempξon，A、W．（1985）：Residuals［reng漁ofclays in landslides， systems，／、勲gfg、ル∫θc11．，！1SC宏，102，249−263、 folded strata and tねe laboratoryンGθo’θc1∼1∼i（1ε’ε，35（1），3−18．44） V▽roこh，C．P．and V》ood，D．N・1、（1978）＝丁むe correla【ion of index34）Sulem，」、，Vardoulakls，1 ，，Ou籏oukh，H．and Perdik飢sls，V． proper［ieswiτhsomebasicenglneerlngPropertiesofso11s，Co17． （2004）：Thermo−Poro覗ec姓anicalprope痴esofthealglonfault clayeygouge・apPlica仁ion［o由eaaalysisofsねea出eatlngand員uid Gθo’（∼ぐh、／、，15（2），137−145．
- ログイン
- タイトル
- stress-Dilation of Undisturbed Sand Samples in Drained and Undrained Triaxial Shear
- 著者
- s. Frydman・M. Talesnick・H. Nawatha・K. Schwartz
- 出版
- soils and Foundations
- ページ
- 27〜32
- 発行
- 2007/02/15
- 文書ID
- 20977
- 内容
- SOILS AND FOUNDA'TIONSVOI. 47,No2732, Feb. 2007lJapanese Geotechnical SocietySTRESS-DILATION OF UNDISTURBED SAND SAMPLES IN DRAlNEDAND UNDRAINED TRIAXIAL SHEARSAh( FRYDhiANi), ivIARK TALESNICKii), HANA NA¥¥*ATHAiii) and KEREN ScH¥¥*ARTZiii)ABSTRACTStress-dilation behavior of undisturbed sand samples tested in both drained and undrained triaxial shear has beenstudied. The stress-dilation relation is recognized as being a basic component of the stress-strain behavior of granularmaterials. The dilation angle, y/ commonly used to represent the dilation characteristics of the soil, is defined clearlyfor plane strain conditions. Ho¥vever, the paper discusses confusion regarding its definition under triaxial loadingconditions, and adopts the definition sin v/= -d8 /dy lax' Drained triaxial tests performed on specimens obtainedfrom undisturbed block samples of sand indicated that the undisturbed material exhibits a ¥vell defined stress-dilationrelation. By referring to plastic (irrecoverable) components of strain, it ¥vas found that this relation ¥vas alsocompatible to results of tests in undrained triaxial shear. Demonstration of this compatibility required that the smallmembrane penetration eff cts in the undrained triaxial shear tests, resulting from changing effective confining stress, betaken into account. From the results of the present investigation, and of other studies reported in the literature, it wasfound that the relation bet¥veen friction angle, c' and dilation angle, V/, under axi-symmetric conditions, as definedabove, can be reasonably expressed by the empirical expression: c' * O.4V/ c**Key words: dilatancy, drained shear, sand, tr'iaxial comp 'ession tests, undrained shear (IGC:D5/D6)principal cornpressive strain, and he developed his stressdilatancy relationship:INTRODUCTIONResearch on stress-strain behavior of _ :ranular materi-(?f l(7 = tan2 (45 ' - cr/2)(1 - de /del )als is, conventionally, based on laboratory testing of(1)lvhere cf is a function of the density of the sand, and liesreconstituted samples. The present paper presents resultsof part of an investigation of the constitutive propertiesof Israeli sands, ¥vhich included triaxial tests on bothundisturbed, and reconstituted samples, with the purposebetween the true, particle friction angle, c , and theof studying the effect of in-situ, internal structure, on thecritical state friction angle, c*+. Li and Dafalious ('-OOO)sug*"ested that cf is related to the state parameter (Beenand Jefferies, 1985) of the sand.behavior of the sand. Undisturbed test specimens wereprepared from block samples extracted in the Haifa Bay'epresents a stress-strain "la¥v" for gr'anular soils. If thisRo¥ve claimed that the stress-dilatancy relationregion. In order to improve reliability of stress-strainrelations, Iocal strain rneasurements ¥vere performed,rather than measurements performed external to the soilis the case, a difficulty may, at first sight, appear to arise,specimen. Equipment was developed for this purpose,ratio, (rf/(T , should remain constant throughout theallowing measurements to be made m the small tostraining process. In fact, Ro¥ve actually specified that themedium strain range.str'ains being consider'ed should be the plastic, or slipcomponents of the overall strain; however, he concludedsince Eq. (1) would indicate that during undr'ainedshearing, inIn this article, attention is concentrated on the stress-'hich volume remains constant, the stressdilatancy behavior of the undisturbed sand. It was firstsuggested by Rowe (1962) that the capacity of granularsoil to carry increasing shear stress (r'epresented by anincreasing ratio, ( f/(T , of major to minor principaleffective stresses) is related to the dilatancy rate in thesoil. Ro¥1'e defined the dilatancy rate as - de /d81, wherethat in drained shear, the elastic or recoverablecomponents of the strains are small enough to be8by Houlsby (1991).rgnored However, in the case of undrained shear, ¥vheretotal volumetric strain is zero, verification of the stress-dilatancy r'elation ¥vould require consideration of theplastic component.s of strain. This point ¥vas emphasizedis the volumetric, compressive strain and 81 is the majori)Prof ssor, Faculty of Civil & En¥'ironmentai Engineering, TechnionIsrael Institute of 'Technology, Haifa 32000,Israel (cvrsfsf @.tx.technion.ac,il).ii)iii}Senior Lecturer, dit o.Former Graduate Student, ditto.The manuscript for this paper ¥vas received for revie¥v on June 23, 2005; approved on Ocrober 2, 2006.¥Vritten discussions on this paper should be submirted before September 1, 2007 to the Japanese Geotechnical Society,Bunkyo-ku, Tokyo I 12-001 l. Japan. Upon reql es the closing date may be extended one month_274-38-2, Sen_cr,_oku, FRYD ,IAN ET AL.2sTHE DEFINITION OF ANGLE OF DILATION,sin v = - (2delSince Ro¥ve's pioneering ¥vork on stress-dilatancy, theimportance of considering not only the static, but also thekinematic aspects of the mechanics of granular media hasbecome ¥vell appreciated (e.g. Roscoe, 1970; Vermeer andde Borst, 1984). This has led to the definition of the angleof dilation, /, (actually originally introduced by Hansen,+ de )1(･-c]e- de )= - (2d8r + de )/(2de- de ) (8)The authors had initially felt that a third, more consistent approach to the definition of dilation angle may be tofollo¥v the convention adopted for c', ¥vhich is definedindependently of boundary conditions, as sin c' = (cr; (T )/((Tfa ), and to similarly definep, under all bound-1958), representing the kinematic equivalent to theary conditions, by. Eq. ('-b). Ho¥vever, under triaxialeffective angle of internal friction, c'. The angle ofconditions, this definition often yields negative values ofV/ although there is volumetric dilation (volume increase),dilation is conventionally defined for plane strain condi-tions (e.g. Hansen, 1958; Roscoe, 1970; Bolton, 1986;Houlsby, 1991), and is given as:sin/= - de, ldyP (2a)",**¥vhich, for plain strain conditions becomes:sin v = - (c/e+ cl8 )1(c!8- c!8 ) (2b)¥vhere y ** is maximum shear strain, 8 and 83 are the'' ,,principal compressive strains, and the indexp inchcates plastic strains.It is noted that a positive value of / corresponds toplastic dilation (plastic volume increase). Furthermore,the definition of / according to Eq. (2b) Ieads to theresult that for a mater'ial yielding in plane strain accord-and so its adoption would be unreasonable.The above discussion indicates that althou*'h Eq. (2b)is a universally accepted definition of angle of dilation forplane strain conditions, differ'ent definitions are in use fortriaxial conditions. It should be understood that definition of the functional form of / is arbitrary, and may bechosen according to convenience, although it is desirablethat one universally agreed- on definition be adopted, inorder to prevent confusion. For example, if v is evaluated from triaxial tests, and then used in plane strain finiteelement analyses, different definitions vould result in theuse of different values in the analysis. The commonlyused numerical codes Plaxis (1998) and Flac (Itasca,'_OOO), for example, su*'gest that / be estimated froming to the Mohr-Coulomb criterion in associated plasticity (i.e. obeying normality), /= c'.triaxial compression tests, according to Eq (7), and thenFor loading under other than plane strain conditions,other definitions have been sug_g:ested for v/. Continuingto adopt the definition given by Eq. (2a) (e.g. Houlsby,1991; Vaid and Sasitharan, 1992), V/ in triaxial compression loading, for example, is given by:calculated from the triaxial tests, according to Eq. (3), asin v/ = - (d8 + de + de )/(de - d8 )= - (de + 2de )/(d- de) (3)¥vhere 8* is the axial str'ain, and e* is the radial stra}n.Similarly, in triaxial extension,sin v/ = - (c!e/ is given by:+ -?de )/(de- de ) (4)An alternative definition of v/ has been suggested byVermeer (Vermeer and de Borst, 1984; Schanz and Vermeer, 1996), for plane strain and triaxial compressionconditions, of the form:sin v/= - (ds /(2cle- de ) (5)In plane strain, Eq. (5) degenerates to Eq. (2b):sin v/ = - (c]8? + d8 )1(deT - de ) (6)Consequently, for plain strain conditions, there iscompatibility bet¥veen the t¥vo definitions given byEqs. (2a) and (5). Ho¥vever, in triaxial compression,used in plane strain analysis. It the value of v/ weredifferent value ¥vould subsequently be used in the planestrain analysis. This confusing situation is undesirable.It is obviously necessary to have a univer'sally agreed ondefinition, preferably one which would give a uniquerelationship between v/ and c for all boundary conditions, representing a fio¥v rule for the material.In order to consider the relative suitability of thealternative definitions of / presented above, an analysishas been made of triaxial compression and extensionfailure data presented by Vaid and Sasitharan (1992).Figure I sho vs the relationship bet¥veen c and v/, basedon the results of 53 triaxial compression and extensiontests on Erksak sand, tested at various relative densities,under various confining stresses and follo¥ving variousstr'ess paths. It is seen that equally. good linear correlations are obtained bet¥veen c and / ¥vhen v/ is definedeither according to Eqs. (3) and (4), or by Eqs. (7) and(8), and neither definition of v/ for triaxial conditions isobviously preferential over the other. Assuming that thecritical state friction angle, cg+, of Erksak sand is of theorder of 3 1 ', the relationships bet¥veen c and / Shown inFig. I are of a form similar to the follo ving, su*'g:ested byBolton (1986) for plane strain conditions:Eq. (5) results in the follo¥vin*' definition of angle ofc' = 0.8 / + cg, (9)dilation:sin v/= - (de + 2d8 )1(c!8r - 2de )where cgis the critical state friction an_ :le of the soil.- -,c!8 ) (7)It is noted that the coefficients of v in the equations ofFig. 1, resulting from triaxial tests, are lo¥ver than theAlthou*'h Vemeer and de Borst (1984) did not refer tovalue 0.8 suggested by Bolton for plane strain. Thistriaxial extension, the form of their development leads tothe follo¥vin relation for triaxial extension:observation is reasonable considerin*' that the frictionangle in plane strain conditions is known to be higher'= - (d8+ _,de )1(c!e STRESS-DiLATION OF UNDISTURBED SAND SAivIPLES(a) 1 / from Eqs (3) and (4)LVZ)TLVDT arm ture plat orrn-4540 C-) )C35Outer magne ic slripo( )9)co o compnco(oa)e)', 9a E c = O.38 fLatex ¥.¥;extn31 .i30 - R2 :: O.8834i a 20-10e nb aneinner 1l gnetic strip ,1Specime 1 1!3a(b)IV (degrees)Fig. 2. Local axial deformation measurement system: (a) photograph(b) Ivfrom Eqs (7) and (8)and (b) schematic detail- 45coc40 -oC )(1)e))e)1:Fao )35e,oE c = 0.59V + 30.5830 -tests described in the present paper ¥vere perforrned onLEL,specimens pr'epared from undisturbed block samples,L'_OO mrn x 200 mmx7_OO mrn, ¥vith relative densities ofbetween 600/0-700/0. The laboratory test specirnens ¥vereprepared by freezing the ¥vetted block samples, and thenR2 = 0.8788coring 70 mm dia. specimens. Following cor'ing, the1 o 1 5 2a-5/ (degrees)specimen was held in a split tefion tube, and the ends cutperpendicular, resultin*' in a specimen length of 1 50 mm.The specimen ¥ "as then r'eturned to the freezer f'orFig. 1. c' versus Y/ at failu e from triaxial compression and ex'tcnsiontests (based on data of Vaid and Sasitharan, 1992)than that under axi-symmetric loading conditions. For/ defined according to Eqs. (3) and (4) for tr'iaxialconrpression and extension conditions respecti¥'ely, it isseen from Fi**. 1(a) that the relationship bet¥veen c' and vlfor Erksak sand rnay be expressed by:c' = 0.4 / + cg, (lO)The remainder of this article studies the relationshipbetween c' and v/ defined by Eq. (3), as obtained fromboth drained and undrained triaxial cornpression tests Onspecimens prepared from undisturbed block samples ofsand from t.he Haifa Bay region. The conclusions wouldbe equally valid if v/ were defined by Eq. (7). It should benoted that, as pointed out by Houlsby (1991), such afunction (fiow rule) may be used to express the relationship bet¥veen values at faiiure of friction and dilationangles obtained from different tests on the same material,as was done m Fig. 1, or to express the relationshipbet¥veen mobilized values of the friction and dilationapproximately one hour prio ' to placement in the triaxialcell.A special technique lvas de¥'eloped to allolv localmeasurement of small, axial strains during the tests.Vertical displacements lvere monitored at four, approxi-mately equidistant, points aiong the specimen height,using LVDT'S. As the specimens ¥vere frozen ¥vhen placedon the triaxial cell base, measuring points on the specimen could not be mounted by t.he usual procedure usingneedle points inserted into the specimen. Consequently, adifi rent mounting procedure ¥vas developed. At eachpoint, a measuring platform ¥vas assembled consisting ofa magnetic strip, 0.5 mm in thickness, 2.5 mm in ¥vidthand 25 mm in length, placed bet¥veen the latex confiningmernbrane and the specimen, and a similar magneticstrip, attached to a measur'ing platform, placed on theoutside of the membrane, held to the first strip by magnetic attr'action. A LVDT ar'rnature platform lvas gluedto the outer magnetic strip. Figure 2 shows the setup,together ¥vith a schematic representation. Calibrationsand initial testing on a rubber dummy sampie verified thest.ability and reliability of these mountings, and indicatedangles as a single test pr'ogresses. The latter appr'oach hasno slip at the rnagnetic strip-specimen interf'ace. Endbeen applied in the present investigation.friction bet¥veen the specimen and the end caps ¥vasminimized by spreading a thin layer of silicon greaseTHE SOIL TESTED AND TESTINGCONFIGURATIONThe sand tested ¥vas sampled from an ancient riverbedin the Haifa Bay area, in Nor'thern Israel. The sand isbetween the highly polished, stainless steel end cap, and alatex membrane (both 'ith central holes for drainage or'pore pressure rneasurement) in contact with the specirnenend. The specimens ¥vere observed to remain essentiallycylindrical during shearing.uniformly graded (SP) ¥vith 870/0 of its particles bet¥veenT'he specimen ¥vas confined in a latex membrane, and0.15 and 0.3 mrn dia.; its major constituents are quartztested using silicon oil as the confining fluid. Followin9:and some calcite. Maximum and minimum dry densitiesare 16.16kN/m3 and 14.03 kN/rn3, respectively. Theapplication of a small confinin*' pressure to the frozenspecimen, it vas allo ved to thaw. The specimen ¥vas then rRYDMAN ET AL.30p' (kPa)p' (kPaj100010010oooo,ool i100 200 30040 oIFev :s IE-05x - O e007O.OOI8v = O.0037LOG(p') - 0.0155R2 s: O 9937O.002 . LOAD R2 = 0.9899o'002 J:' JH UNLOAD-RELOADe'0.003o'003o'004 lev s 4E-06x + o OOi 8R2 :: O 9e90.004 -f ev = o.ool9LoG(P') - o.0053･ LOADo,005 - R2 # 0.99i9UNLOAD*RELOAD0.005o.006IFFig. 4. Isotropic consolidatiom, correctcd for membrane penetrationo,007Frg. 3. Isotropic consolidation, uncorrected for membrane penetra-ric strains, as seen in Fig. 4. A comparison of Figs. 3 and4 illustrates the importance of taking account of mem-tionsaturated under a relatively high back pressure, prior tothe application of consolidation pressure and shearing.brane penetration effects with changing effective confining pressure.DRAINED TRIAXIAl. SHEAR TESTSISOTROPIC CONSOLIDATIONIn order to divide strains into elastic and plasticThe result of an isotropic consolidation test performedon the sand is sho¥vn in Fig. 3. This figure indicates asemi-log relationship bet¥veen effective isotropic stress,p', and both total and recoverable volumetric strains, 8,components, a drained triaxial test ¥vas carried out whichincluded seven load and unload cycles, and the resultingstress-strain curve is sho¥vn in Fig. 5(a). It was found(Fig. 5(b)) that the irrecoverable axial strain, 8f, could beand 8 ,. In this work, reco¥'erable strains have beenrelated to the total axial strain, el, through the followin*'defined as elastic strains, and irrecoverable strains aslinear relationship, ¥vith a correlation coefficient, r2=0.999:plastic strains; this definition may need to be reconsideredin the framework of kinematic hardening plasticity, but isadopted here for simplicity. Figure 3 ¥¥*as based on volu-metric strain measurements, without takin*' account ofmerrrbrane penetration; however, ¥vith cell pressureincrease during an isotropic consolidation test, themembrane penetrates into the outer interstices bet¥veenthe particles, expelling ¥vater and indicating a specimenwater content change inconsistent ¥vith the actual volumechange of the specimen. Frydman et al. (1973) found thatthe membrane penetration volume/unit surface areaincreases, Iinearly,vith log ((T ), ¥vith a slope, g.*,expressed as a function of mean particle size, d. Forstandard, 0.3 mm thick latex membranes such as thoseused in the present study, and d in mm, this function wasfound to be given by:g(cm3/cm2) = 0.014 iog (d ) + 0.012 (1 1)8f = 0.98 1 681 (1 3)Fi*･ure 6 sho vs the relationships bet veen mobilizedvalues of sin v/ (as defined by Eq. (3)) and sin c', as ¥vellas bet¥¥'een v/ and c' , based on the results of three drainedtests performed on undisturbed specimens, at effectiveconfinin*' pressures of between 100 kPa260 kPa. In earlycalculations, it was found that values of sin v/ (or v/) indrained tests ¥vere almost identical lvhen based on eithertotal or plastic strains; consequently total strains ¥vereused for all later calculations, and the values sho¥vn inFrg 6 are based on these. From Fig. 6(a), the relationbetween sin v and sin c' is given as:sin vl=2.77 sin c' - I .45 (14)and the relation betlveen c' and v is given as:For the present sand (mean particle size 0.25 mm),c' = 0.4 / + 3 1 .9' (1 5)g+,* = O.0045, and for specimen dia = 70 mm, the volumetric strain as a r'esult of membrane penetration, 8 , due toEquation (15) is seen to be very similar to the relationobtained for Erksak sand (Eq. (10)). Considering that cg,a chan*"e in effective confining pressure from ((7 )* to (cr )bof Israeli sands may be taken as around 32' (Frydman,is given by:2000), it would appear reasonable, on the basis of8* = O.0023 Iog (((T ) /((7f ).) (1 _')When the membrane penetration effect in the presenttests was taken into account, the soil compressibilityvasfound to be significantly reduced, and relatively linearrelationships ¥ 'ere obtained bet¥veen p' and the volumet-Eqs. (10) and (15), to suggest the following relationshipbetween c' and v/ (defined according to Eq. (3)) for sandsunder axi-symmetric loadin ':*c' = 0.4 / + cg, (1 6)If the stress-dilation relationship is truly a basic FSTRESS-DILATIOiN OF UNDISTURBED SAND SA*lvIPLEScomponent of' the constituti¥'e behavior of the sand,12ao -Eqs. (14) and (1 5) should apply, also, in undrained shear.In the remaining portion of this paper, this principle is's 800oool600 l:+i;2<!c) 400 Jss;s:investi**ated.$$;!si',;2co 'UNDRAINED TRIAXIAL COMPRESSION TESTS$oa2a8412el oloT¥vo consolidated undr'ained, tFiaxial tests ¥vith porepressure measurement were performed at consolidationpressures of 80 kPa and 150 kPa. In addition, a test atconsolidation pressure of 180 kPa ¥vas car'ried out with10ad-unload cycles in order to allo¥v separation of axialstrain into eiastic and plastic components, as was done(a)for the drained test. The relationship between plastic (8f),ioand total axial strain (8 ), ¥vas found to be given, in this8case, by:es: e"nO1CLy = O,,9816x,l4= 0.9223el ( 1 7)In order to check if the stress-dilation relationshipR* = O.9997established for the drained tests (Eq. (14)) is also relevantto the undrained tests, the follolving procedure was used:(a) The development of effective stresses, (Tt and (T ,oo2s4108was calculated throughout each undrained test. Changes81 o/oin (Tf ¥vere calculated accounting for change in the cross-sectional area of the specimen under zero volume change,as ¥vell as membrane penetration as a result of changin*"pore pressure and therefore of effective confining stress.(b)Fic.5. (a) Load*unload drained,triaxial stress-straincurve and (b)Plastic versus total axial strain0,5stage of the test is gi¥'en by:8 8 +28 +8*=0 (18)(a)vhere 8* is the compressive volume strain due to membrane penetration, given by Eq. (12).(b) From known values of (Tf and a at each stage ofo 4>s'0,3e 100 kPaCl 200kPo,2A 250 kPaThe overall volume balance during the undrained shear( e;ethe test, sin c' was calculated.o 1(c) For each value of sin c', sin v/ was calculatedofrom the stress-dilation Eq. (14).(d) Incremental values of axial strain ¥vere calculated.1o3o;7o.6o .4.2from test measurements, and then plastic axial strainy = 2 77i9x . I .4486R2 = 0.9332),3increments, def, were calculated, using Eq. (17).(e) Incremental values of plastic radial strain, de ,),4¥vere calculated from Eq. (3).(f) Accumulated plastic axial and radial strains werecalculated from steps (d) and (e). Ieading to accumulatedsinc'plastic ¥'olumetric strain, 8. .(*･) Accumulated elastic volumetric strain, 8+*,, ¥ 'ascalculated, f'rom the expression:(b)40 COe,(D35OeF'.c(Dc' = 0.414,e,F*ioFig. 4, ¥vhich represents the elastic compressibility of thesand.Figur'es 7(a) and 7(b) show curves of' calculated eo102030¥V (degrees)Fig. 6. Stress*dilation relationshipobtained fromdrainetl triax'ial tcstso:1; undisturbed specimens= O (19)and p' was thencompared to the unloading consolidation curve shown in31 .9R2 = O 9322520+ 8*p + 8(h) The r'elationship between 8¥'ersus p', for the two tests analyzed. Although bothspecimens indicate bulk moduli of the same order ofma*"nitude, the sample tested at the higher confiningstress sho¥vs a lower bulk modulus. This is a result of thevariability of densities between test samples. The order of FRYDilvIAN ET AL,32tent with that observed in drained shearing may also beo o006,i'y =: 2E4Sx - 0.00i5 fo o004magnitude of the plastic strains, such analysis must bebased on results of tests in which local, small strainR2 s O.9978o o002identified in undrained shearin*'. Due to the smallmeasurement is performed, and membrane penetrationoIeffects must be taken into account.; -o o002Confusion exists with regards to the definition of-o o004dilation an*"le, V/, under axi-symmetric loading condi-*o o006tions. It has been found that using the original definition,V/= -d8, /dy **, the relation bet¥veen friction angle, c'(a)q; =80 kPa-o o008and dilation angle,-o ool200400600800/, under axi-symmetric loadin*'conditions, can reasonably be expressed as:c' = O.4v/ + cg,p' (kPa)REFERENCESo 0025o 002y = 7E4ex - O.0033F = O.999eO Ool 5l) Been, K. and Jefferies, M. CJ. (19S5): A sta e parameter f'or sands,Geotechniql!e, 35, 991 12.Io ool7_) Bohon, lvl. D. (1986): The strength and dilatancy of sands,Geotechnique, 36, 6578.3) Frydman, S. (2000): The shear strength of? o o005sraeli soils, Israe! ,J.EartJ1 Sciences, 49, 55-64.o4) Frydman. S., Zeitlen, J. G. and Alpan. I. (1973): The-o o005effect in triaxial testing of granular soils, ASrIVI J. Tesl(b)cF3= ISO kPa =-o oO 1;-o ool 5200600400800p' (kPa)nembraneEva!., l(1), 37-41^5) Hansen, B. (1958): Line ruptures regarded as narro¥v rupture zones,Basic equations based on kinematic considerations, Proc. Coiif.Eanh Pressure Prob!en7s. Bnl,sse!s, I , 39-486) Houlsby, G. T (1991): Ho¥v the dilatancy of soils affects theirbehaviour, Proc. lOth Eur. Conf^ on S1 /:fFE, Floreuce, 4,Fig. 7. 8versus p' from undrained tests calculated assuminer stress*dilation F,q. (14)the moduli, rather than their absolute values, should beconsidered.Figure 7 sho¥vs that for the two tests analyzed, theslopes of the relationships bet¥veen e and p' estimated inundrained shear on the basis of the stress-dilationrelationship found in drained shear, are of the same orderas the measured elastic (unloading) slope (4E-06 1 /kPa),sho¥vn in Fig. 4.l 1 89-1 202.7) Itasca (2000): FLAC-Fast Lagrangian Ana!ysis of Conti,It!a, Itasca Consuhing Group, Inc., ivlinneapoiis, Minnesota, USA^8) l,i, X. S. and Dafalious, Y. F^ (2000): Dilatancy for cohesionlesssoils, Ceotechnique, 50, 449-4609) Plaxis (1998): Firlite E!enlent Code,for Soi! and Rock Ana!.l ses, ¥'er-sion 7, (eds. by BFinkgreve, R. B_ J. and ¥rermeer, P. A.), A, A.Balkema, Rotterdam.lO) Roscoe, K. H (1970): The influence of strains in soil mechanics,Geo!echniql!e, 20, l'_9-i70.ll) Rolve, P. ¥V. (1962): The stress-dikuancy relation for staticequilibrium of an assemb y of particles in contact, Proc. Roya!Sociely. A. , 269, 500527.12) Schanz, T. and Vermeer, P. A. (1996): Angles of friction andCONCLUSIONSAnalysis of triaxial tests performed on undisturbedsand samples has sho¥vn that by considering plasticcomponents of strain, stress-dilatancy behavior consis-dilatancy of sand. Georecllniqlre, 46, 145l51 .13) Vaid. Y. P, and Sasitharan, S. (1992): The s ren_'*th and dilatancy ofsand, Can. Geotech. J > '_9, 52,_526.14) Vermeer, P. A, and de Borst, R (1984): Non-associated piasticityfor soils, concrete and rock. Her0,1, 29(3), 1-64_J
- ログイン
- タイトル
- Experimental Study on the Measurement of S-p Relations of LNAPL in a Porous Medium
- 著者
- Masashi Kamon・Y. Li・Kazuto Endo・Toru Inui・Takeshi Katsumi
- 出版
- soils and Foundations
- ページ
- 33〜45
- 発行
- 2007/02/15
- 文書ID
- 20978
- 内容
- SOILS AND FOLJNDATIONS¥Iol. 47, No .l33-4S, Feb. 2007Japanese Geo echnical SacietyEXPERIMENTAL STUDY ON THE MEASUREMENT OF S-p RELATIONSOF LNAPL IN A POROUS MEDIUMMASASHI KA ,IoNi), YAN Llii), KAZUTO ENDOiii), TORU INUltv) and TAKESHI KATSU¥. n+)ABSTRACTA simple and effective device for measuring saturation-capillar'y pressure relation (S-p relation) in LNAPL-¥vatersystem is designed ¥vith electrical conducti¥'ity probes, hydrophilic tensiometers and hydrophobic tensiorneters. Withthis device, the S-p relation in LNAPL-water system is characterized. The S-p relation in air-LNAPL system isobtained by a scaling factor method. At a given saturation of wetting phase, it is found that the descending sequence ofcapillary pressures is in the order of air-water, LNAPL-water and air'-LNAPL systems. The descending sequence ofentry pressure and displacement pressure is also in the order of air-¥vater', LNAPL-¥vater and air-LNAPL systems.Furthermore, the relative permeabillty of air is larger than the LNAPL in their corresponding aqueous t¥vo phasesystems, and the relative permeability of the LNAPL is slightly larger than ¥vater in their corresponding g:aseous t vophase systems.Key words: capillary pressure, degree of saturation, electrical conducti¥'ity probe, light non-aqueous phase liquid(LNAPL), relative permeability, scaling factor method (IGC: B121E7)¥'ertical movement and redistribution of mobile LNAPLSwithin the saturated and unsaturated zones. It is veryimportant to determine the characteristics of LNAPLSINTRODUCTIONNon-aqueous phase liquids (NAPLS) are hydrocarbonliquids and volatile organic compounds that are notmigr'ation in the subsurface with the fluctuation ofvaterreadily miscible vith ¥vater and air. Depending on theirdensities, NAPLS are typically classified as either lighttable in order to remediate the subsurface contaminationnon-aqueous phase liquids (LNAPLS) that are lightewater table fiuctuation on the distribution of LNAPL insubsurface, there are mainly three methods. One is aneffectively. In order to analyze and quantify the effects ofthan ¥vater, or dense non-aqueous phase liquidsanalytic method, in ¥vhich, the in-situ complicated(DNAPLS) that are denser than water.When LNAPLS are released into the subsurfaceproblem is simplified, and thus the analytic solution ofthrough spill or leak, they will migrate do¥¥'n¥vardthe in-situ problem is obtained, ¥vith errors to somethrough t.he vadose zone. The fate, flow and transport ofextent. One is a physical simulation, on lvhich, a proto-LNAPLS are governed by complex interactions amon_crcapillary, viscous and gravity force, mass transferbetween phases and chemical and biological reactions.These processes are also affected by factors such astype system (i.e., the in-situ cornplicated system) is simulated ¥vith a model-based system, i.e., an ex-situ device.The ex-situ device is a reductive in-situ system, ¥vhich isobtained by reducing the in-situ system to a scale asrequested by the theor'y of similarity. Another is anumerical simulation. With regard to this method, therelationship bet¥veen the ¥vater saturation and thetemperature, soil and fluid compressibility, soil heterogeneity, volume of spilled LNAPLS and geometry of thespill source. At a LNAPL polluted site, LNAPL forrnscapillar'y pressur'e (S-p relation) is needed. To measurethe capillar'y pressure as a function of ¥vater saturation,the free lens above the ¥vater table or is tr'apped in thepores in the subsurface. Some evapor'ates into the air(volatilization), some sorbs the sur'face of the soilfive main methods are kno¥vn, i.e., Iong column,particles (sorption), and some dissolves into the ground-centrifuge, vapor pressure, pressure cell and Brooks'water (dissolved plume). Fluctuation of ¥vater table,¥vhich occurs due to pumping of groundwater in a largemethod. Each of them has innumerable variations(Corey, 1994); however, the measurement of water saturation in a porous medium is a major task during meas-quantity or seasonal variety of rainfall, can also causeii)iii]IT]Prof ssor, Graduate School of Global Environmentai Studies, Kyoto University, Japan.Graduate Studem, ditto (Currently Lecturer, Sun Yat-sen Universit_¥', China).Researcher, Research Center f )r lvlateriai Cycles and ¥Vaste Management, National Institute for En¥'ironmental S udies, Japan,Assistant Prof'essor, Graduate School of (i lobal Environmentai Studies, Kyoto Unh,ersity, Japan (inui@*mbox.kudpc.kyoto-u_ac.jp).Associate Professor, ditto,The manuscript for this paper ¥vas received for reviel ' on September 24, 2004; approved on October '2, 2006.¥¥fritten discussions on this paper should be submitted before September l, 2007 o the Japanese Geotechnical Society, 4-38-2, Sengoku,Bunkyo-ku, Tok"vo ll2-001 1, Japan. Upon request the closing date may be extended one month.33- 34KAlvION ET ALurement of S-p relations. Although gravimetric samplin_"..electrical conducti¥'ity probes in L,NAPL-¥vater system.method for measuring ¥vater satur'ation is the mostThe other is to obtain the characteristics of LNAPLaccurate method, it can not provide rimely and accuratemigration in a porous medium to simulate accurately anLNAPL distribution in subsur'face.¥vater saturation continuously and automatically,because soil samples must be removed from a soil mass.In laboratory experiments, generally, the non-intrusive ornon-destructive methods should be used to measure fluidsaturation. Widely accepted in situ methods for measur-CONSTITUTIVF, MODF,LINGCapil!ary Pressul'e Headin*' soil ¥vater saturation are radioacti¥'e methods such asIn a t¥vo-phase porous medium system for monotonicthe neutron scattering method (Gardner and Kirkham,displacement of a wetting fluid j by a nonwetting fiuid i,the capillary pressur'e Pij can be given as:1951), X-ray or the gamma ray attenuation method(Host-Madsen and ,Iensen, i992; Illangasekare et al.,1995a, 1995b; Lenhard et al., 1993; Reginato and vanPjj = Pj - P(1 )Bavel, 1964; Tidwell and Glass, 1994). Time Domain¥vhere Pj is non¥vetting phase pressure; and Pj is ¥vettin-'Refiectometry (TDR) method (TOpp et al., 1980), and soon. These methods ar'e quite accurate anri non-destructive; ho¥vever, they require special caution to avoidpossible health hazards or higher investment. In thispaper', ¥vater satur'ation is measured ¥vith electr'icalconductivity pr'obes (Endo, '_002; Kamon et al., 2003).phase pressure.lvli**ration of a fiuid in a saturated porous medium isexpressed by Darcy's law, ¥vhich can also be extended todescribe a multiphase flo¥v (Bear, 1979; Sharma, '_OOO).lvhere p,. is the density of lvater; and g is the scalar magni-In a multiphase fio¥v system, flux of each fluid is afunction of its effective satur'ation (Brooks and Corey,1964). The unsaturated hydraulic conductivity, ¥vhich islinked with the saturation and capillary pressure, shouldbe determined to simulate accurately a L,NAPL, distribu-tion in an unsaturated porous medium. Ho¥vever, therelationships among capillary pressure, saturation andunsaturated hydraulic conductivity ar'e different durin_"._dryin*' and ¥vetting processes because of contact an*'1ehysteresis and non¥vetting fluid entrapment. Due to theInstead of pressures, it is con¥*enient to employ capilla-ry head, h*j , which is defined on an equivalent vaterheight basis by:/1,ji = Pji /p,.g (2)tude of **ravitational acceleration.In the case of LNAPL, and vater t¥vo-phase sy. stem,t¥vo kinds of probes for measurin*' the pore liquid pressures are required. One is hydrophilic tensiometer ¥vith¥vater-wetting ceramic cup to measure pore ¥vater pressure and the other is a hydrophobic tensiometer ¥vith aLNAPL-¥vetting ceramic cup to measure pore L,NAPL.pressure. The capillary pressure is simply the differencebetween the higher one and the lo¥ver one of the t¥vo pressure readin*"s (Dullien, 1992).practical difficulties encountered in measuring thek-STP Re!atiol7sThe relationship bet¥veen saturation of phase,j, Sj, andunsaturated hydraulic conductivity, considerable effortscapillary pressure head h, in unsaturated porous mediahave been made to estimate the value of unsaturatedwith immiscible fluid phases, pair i and,j, is referred to ashy. draulic conductivity from the relationships bet¥veencapillary pressure and saturation (Lenhard and Parker,a ¥vater retention curve or S-p relation, ¥vhere i and ,ji 987a) .tively. A ¥videly accepted empirical parameter form givenby van Genuchten (1980) ¥vas written as (Helmig, 1997):Furthermore, obtaining the relationship bet¥veen saturation and capillary pressure for a different phase in athree-phase system (air-LNAPL,-¥¥rater) is time consuming and no standard procedure is available for simultaneous measurements of the saturation and pr'essure of ¥vaterand LNAPL in a porous medium. Only a few results ¥verestand for non¥vetting phase andvetting phase respec-/1,ijI _ 1)1/" /1.jj>0 (3)= (Sj*l !"'aiEquation (3) refers to van CJenuchten model (VG model),where (x (1 /cm) and n are parameters, and ll7= I - I In.presented so far for the migration of L.NAPLS inThe effective saturation of the,j phase, S]* is defined as:unsaturated sand using large-scale tanks (Kechavarzi etal., 2000). Therefore, researchers have suggested the useSj* - Sj - Sj, (4)of STP relations in t¥ 'o-phase system to predict those inthree-phase sy. stem (Par'ker et al., 1987). Lenhard andParker (1988) developed an experimental apparatus tomeasure directly the relationships bet¥veen saturation andcapillary pressure in a three-phase system ¥vith unconsoli-dated porous media. Their results indicated a closeagreement bet¥veen ¥vater saturation in a three-phasesystem and that in a t¥vo-phase system as a function of¥vater-L.NAPL, capillary pressure.In this paper, there are two features that are bein_"._focused on. O_ ne is to measure the SiP relations lvith thei - Sj*¥vhere Sj* is the residual or the irreducible saturation ofthe ¥vetting phase j.Another famous empirical form ¥vas given by Brooksand Corey (1964) (BC model), and the equation was¥vritten as:/7,,J hdS i";- h.jj>/1(5)¥vhere ), indicates the pore distribution index and /?d is thedisplacement pressure head of the reference two-phasesystem, that is, the displacement pressure head from the; i 'r'.SRELATIONS OF LNAPLphase j to the other phase i.35LJ pL or waterJrIn a porous medium ¥vith multiphase flolvs, Darcy sLaw is extended as follows:Ivj = - (k*j ///j)(rpj - Pig) (6)¥vhere vj is defined as avera*'e velocity of fluid i; Pl ishydrostatic pressure of fluid i; /ti is viscosity of fluid i; pjand k*j are density and eft:ective perrneability respectively.The effective permeability, k,j, is _ :enerally expressed asa function of the intrinsic permeability k of the mediurn,¥¥'hich is defined as follolvs:k*j = kk*j (7)lvher'e k-*i is called relati¥'e permeability of fluid i.The method for predicting relati¥'e permeability is alsoproposed as the VG and BC models, and the value of therelative permeability is estimated from the parameters ofthe S-p relations fitted ¥vith VG and BC models.As for VG model, the relative per'meability of thenon¥vetting phase, k*j, and that ofbe described as follo¥vs:vetting phase, k*j, cani /""" 'k,j=SJ'*[1 -(1-Sj. ) J- (8)l/"""' (9)k,j = (1 - Sj.):.'[1 - S , J-Fig. 1. Experimeutal apparatus for measuring S-p relations in aLNAPL*lvater s, stemvhere 8 and y representing the conductivity of porestructure can be regarded as e = I /2 and y= I /3, respecti¥'ely (Helmig, 1997).As f'or BC model, the values of therri can be expressedas follo¥vs.The drainage process ¥vas continued until LNAPL beganto be pumped out from the bottom. After' draina*'eprocess had completed, the wetting process began. TheLNAPLk*j = S{･3･･),, (1 O)k,, (1 Sj.) (1-Sj･ -;. ,';) (11)vas purnped out of the column from thebottom, and same volume of ¥vater was infiltrated intothe sand sample frorn the top of the column simultaneously. The ¥vetting process lvas completed ¥vhen ¥vaterbegan to be pumped out of the column. Durin_g: theMATERIALS AND EXPERIMENTE.1"pei'iinen ta! ApparatusThe schematic for measuring S-p relations in LNAPL-drainage or the ¥vetting process, there ¥vas al¥vays a liquidlayer above the sand sample in the column to prevent airfrom penetrating into the sand sample. It can be assuredthat the testsvere al¥vays in a LNAPL-water systemwater porous medium system is sho¥vn in Fig. 1. Anacrylic column (35 mrn inner diameter, 45 mm outerduring both the drainage and ¥vetting processes.diameter, and 50 mm in length) was utilized, ¥vith t¥vopairs of tensiometers assembled along one side, and threeelectrical conductivity probes assembled on the oppositeside. A pair of tensiorneter's is composed of a hydrophobic tensiometer and a hydrophilic tensiometer' for meas-Matel'ia!s and Samp!es P/'eparationToyoura sand, ¥vith a particle density of 2.64 g/cm3,compacteci-state void ratio of 0.62, and saturated densityof 2.01 **/cm3, ¥vas used as a sandy porous medium forthe column test. The grain size distribution of Toyourauring the pore LNAPL pressure and the pore ¥vatersand is sho¥vn in Fi*･. 2.pressure respectively. At the same position of a pair ofA sodium chloride solution ¥vith the concentration oftensiometers, an electrical conductivity probe ¥vas utilizedO.05 mol/1 ¥vas used as the initial pore ¥vater to raise theto measure water saturation. Only the pore liquidat the sarne position ¥vere adopted for S-p relationreactivity of the electrical conductivity probe and toavoid the formation of condenser cornponent in the sandsystem (Kamon et al., 2003). The full water saturation ofdescription. A rotary pump ¥vas utilized to pump the poreliquid out of the column.A testing program is cornposed of the drainage processmethod. The sand sample lvas poured into the column viaa funnel in uniform layers. Then, the pore ¥vater lvasand thevetting process. During drainage process, firstly,induced from the bottorn of the column, and thesand sample ¥vas fully saturated ¥vith water. Then porecorresponding volume of the sodium chloride solution¥¥'as filled into the sand medium from the top of thecolumn. Thus, before the drainage process began, thesandy mediurn had been fully saturated with the sodiumpressure, Pj and Pj, and ¥vater saturation data measuredwater ¥vas pumped out of the column at the bottom.Simultaneously, same volume of the LNAPL ¥vas infiltrated into the sand sample from the top of the column.sandy mediurn was achieved by an underwater falling KAl¥,ION ET AL36chloride solution. Paraffin liquid was used as a substitutefor L.NAPL, due to its very lo¥v volatility. at room temperature, negli_9:ible solubility in ¥vater and safety tohealth. In order to distinguish visually the downwardmigration of the inter'face bet¥veen the L,NAPL and the¥vater during the drainage process, LNAPL, Ivas dyed¥vith Sudan 111 ¥vith the ¥veight ratio of 10000:1. Theproperties of materials used in this test are sho¥vn inTable I .WATER SATURATION MEASURF,MENTE!ecti'ica! Conductivity P/'obeConductance (reciprocal of resistivity) of sands ismostly due to the presence of ¥vater, and electrical resistivity is a function of water content since it is the majorconductive material of the soil matrix. In a multiphasesystem composed of NAPL,, air, ¥vater, and pure sand,laboratories. Due to the dif iculty of designing a multichannel system and several seconds needed for measurin_one signal for a four-electrode probe, in this paper threeelectrode electrical conductivity probes ¥vere utilized toestimate the ¥vater saturation via the measurement of theelectrical conductivity of sand system under immisciblet¥vo-phase flow condition. Althou_ :h this electrical con-ductivity probe ¥vas ori>*inaily developed to measureDNAPL saturation in a porous medium, it can also beused to measure the saturation of LNAPL, which alsoacts as an insulator in the L,NAPL,-water system.Compar'ed to FDR and TDR, the electrical conductivity probe designed by Endo (2002) is very cheap and easyto make by oneself. It is feasible for a column test due toits small size. The electrode of the electrical conductivity,¥vhose diameter is about 1.0 mm and length is about 15mm, is almost non-destructive to the sands. Each of themhas three parallel electrodes. Thus, there is no interfer-¥vater ¥vill be the principal conductor of electrical currentence bet¥veen t¥vo adjacent probes. The disadvanta*･es of¥vhile air, sand particles, and NAPL, which have a largerthe electrical conductivity probe are also obvious. Themeasurin** accuracy of this electrical probe for' ¥vatersaturation is slightly lolv. The electrical conductivityprobe is only feasible for the porous media, ¥vhose pore¥vater is electrolyte. When this electrical conductivityresistance, ¥vill act. as insulators. Thus soil system ¥vithhig:her wat,er saturation is endued ¥vith a lower electricalresistivity. The ¥vater saturation in a porous medium canbe measured by the changes in electrical resistivity of thismedium as described by Archie (1942, 1947). Since then,a four-electr'ode probe has been the standard for theprobe is utilized for the measurement of lvater saturation,electrlcal investi**ation of soil system in both fields andnecessary. Thus this three-electrode electrical conductivity probe is not feasible for in-situ situation.the initial voltage of the resistance attached to it is100Ca!ibration of E!ectrica! Collductivity p/･obes.eu,u,Prior to the calibration, it ¥vas confir'med that theconductivity values of the LNAPL, air', and sand ¥verene*'1igible compared to that of the O.05 mol/1 sodium80,15S:.60e)chloride solution by measuring the volta*"e of theSresistance attached to the probe inserted in the pure,,)u),U40LNAPL, and dry sand samples.a)For measuring the ¥vater saturation, po¥ver source of1.0 Vpp (Peak to peak volta*'e of AC) in output voltage:.)=,OG,,20and frequency of O.1Hz,, provided by a Functiono ol 0.1 IoooiSynthesizer, ¥vere selected. Lo¥v volta*'e of AC was usedso that probes could not interfere ¥vith one another, andelectrolytic reactions in the vicinity of the electrodescould not happen either. Data recorded by a data logger10Equivalent Grain Size, D (mm)Fig. 2. Grain size distribution of To,oura sandTable 1.Properties of materials used for measuring S-p relations in LNAPL-,vater systemFormulaAppearanceBoiling point,Ielring pointE¥'aporation rateSpecific gravityPara in liquidSudan 111¥¥raterC_olorless, odorlessC..Hl6NsORed powderColorless> 300'C_< - 10'CViscosity (mPa s)Hazard na ureSurface tension (mN/m)3 1Interfaciai lension (mN/m) 1)Eleclrical conductivity (mS/cm)l) ¥^ ,Ieasured by Ring method (Huh and ivlason, 1975)l OOo C100'COoC_Non¥*olatileO.87InsoiubleI 70 O (20'C)¥¥rater solubilitvH. Ol .OO<0.1 gllNon toxic07 (25'C)6,_.06 (25'C_)OO7'_.75 (7_OoC_) S*p RELATIONS OF LNAPL37io.60.55O.8o.5,:> 0.45CVOL O.GS,De)f:f 0.4CVU,:xa, 04>o o.35.,:lo.30.2o.250.2o 5 1 o 251520Time (min.)Fig. 3. Variet)' of oiltput voltage during a drainage processooo Voltage2 0.4Index,o.6R/Roo.81Fig. 4. Output voltage index-water saturation relation in air*watersystemwas only the output voltages across the resistanceattached to the electrical conductivity probe. In order toestimate the ¥¥'ater saturation of the sand sample, it isnecessary to get a relationship bet¥veen output signals andvater saturations. Generally, this kind of probe needs tothe charging process has gotten its balance then thedrainage process begins.Till point C, the sand sample around the electricalconductivity probe is still fully saturated ¥vith ¥vater.be calibrated for every porous medium sample.After the ¥vater table passes through the electricalAccordin*' to the Ohm's la¥v, if the resistance across thesand sample has a good relation with its ¥vater' saturation,conductivity probe, the output volta*'e decreases ¥vith thereduction of vater saturation of the sand sarnple nearbythe volta*"e across the same sarnple must have a goodrelation ¥vith its vater saturation. Thus the outputthe electrical conductivity probe. At point D, pump anddata logger ¥vere stopped, and the sand sarnple aroundthe probe ¥vas obtained fr'om the column for measurin*'¥vater saturation with a gravimetric method. Durin*" thisvoltage across the resistance attached to the probe couldbe utilized as an important parameter to estimate the¥vater saturation.drainage process, the output ¥'olta*"e at point C, Ro (V) isThe output voltages across the resistance attached totaken as a reference value. Namely, Ivater saturationthe probe, recorded by the data logger with a sampleequals to I if the output voltage, R (V), recorded by theperiod of 0.5 second, are of sine ¥vave. Cosine function,data logger is equal to or bigger than Ro under abased on the fitting method by Chapra and Canalehydrodynamic condition. It is also tested that the watersaturation is zero when R is equal to zero.(1998), was selected to fit the data to obtain the amplitudes of the output signals.The variety of output voltages across a resistanceattached to an electrical conductivity probe in a porousmedium during a whole drainage process is sho¥vn inFig. ,3. Until point A, the sand sample is under aA ir- Water SystelnIn order to obtain the sand sample lvith its 1'ater satu-hydrostatic condition, and fully saturated with the sodium chloride solution. The output voltage firstly decreasesslowly to achieve its equilibrium, due to charging of theration known and its corresponding output voltage valueacross the attached resistance, the drainage process wasimposed by a rotary pump to extract pore water out ofthe column frorn its bottom. When there was no water toflow out of the column, the sand sample located aroundsand sample (Iitani and Masuda, 1975). When waterthe probe was extracted as a specimen for measuringbegins to be pumped out of the column, the water flowincreases the conductivity of the porous medium. Thusthe voltage of the resistance attached to the probeincreases suddenly to point B. Then it maintains a con-water saturation with *･ravimetric method. Its correspond_ing output ¥'oltage value across the attachedresistance was also recorded with a data logger. Thisstant value or decreases slightly to point C, which is theoutput voltage value ¥vhen the water table fell down justabove the electricai conductivity probe. With re*'ard todraining periods to *'et sand samples ¥vith different ¥vaterthe line B to C, it is normally parallel, and the volta*･e atconditions. From Fi*･. 4, a good relationship between S,any point on the line is almost constant. However, if thechargin_ : process has not reached its balance at point Aand the voltage of point A has not got its stable value, theequation shown in Eq. (12). This indicates that a relationship between S, and R/Ro is not significantly affected byline B to C will slightly decreases due to the further charg-the ¥vater fiow condition.procedure was conducted with different draining rates orsaturations. Figure 4 shows the relation between outputvoltage, and ¥vater saturation under different ¥vater flowand R/Ro is observed and expressed ¥vith the empiricalin*' process. Accordin*"Iy, after the sample preparation isfinished, and before the drainage process begins, the sandS++ = A(1 .O - eB!?/R.) (1 2)sample fully saturated with water should be placed forseveral hours under a hydrostatic condition. Only whenwhere S,+ is water saturation; and A and B are fittingparameters respectively. KA*¥*iON ET AL.381t S rnple (S nd, LNAPL &Water), W ,Mixed wi h EtheThen ltrated v th 0.22 m iteO.8::Ol Sand (W*), W ter&EtherCU OGLNAPL (WL), Ether & WaterL .::Heated atHeated at 60 'CiO"CSar d (W=)C1:U)LNAPL(WL), jrnount of w ter fa,D.4i.':l:A small0.2Dehydrated wi h Siiiea GelWashed with EtherFiitr ted with O 22 m ilteoLNAPL (WL), Ether0.2o 4 o.8Voitage Index, RjRoo=Lk r i "o.6He ted at 60 'c *Fig. 5, Method for measuring the lvater content of a sand samplecontainina both LNAPL antl waterFig. 6. Output voltage index*wa:ter saturation relationwater system¥ llLNAPL- Water System'In L,NAPL-water system, it ¥vas found that, to controll)¥:v . i' Ceramlc Cup¥ , ' Sprayed withdifferent drainin*' rates and dr'ainin*' periods in theWater-Proof Materi aleffective. After LNAPL-1vater interface passes a fullysaturated sand sample, most of the pore vater is com-l'pelled out of the sample, and the ¥vater saturation of themeasure the ¥vater saturation, because the sand sample.lol: se;calibration of these electrical conductivity probes ¥vas notthe sand sample ¥vas removed from the column, thenormal gravimetric method could not be utilized toin LNAPL-¥¥;the ¥vater saturations of the sand samples by usingsand sample is nearly constant. It is more effective toobtain sand samples ¥vith different water saturations bycontrolling the LNAPL-¥ *ater interface position. After1.lPressu re Transd ucerFig. 7. Schematic of modif ) ing a h .'drophilic tensiometer to be ah) drophobic oneof the electrode, the pore ¥vater may not form ¥vater filmwas composed of pure sand, LNAPL and ¥vater. Thus aaround the electrode. In addition, there would be amethod sho¥vn in Fi**. 5 ¥vas designed to separate sand,possibility to change the we ability of the electrode fromLNAPL. and water out of the sand sample.¥vater-¥vet to oil-¥vet.In order to testify the feasibility of this separationmethod, two blank tests ¥vere conducted. For' the testCapi!!ary Presstll'e Measuren7e/7tsample preparation, sand, water and LNAPL of kno¥vnTensiometers (SWT5, Delta-T Devices Ltd.) ¥vereweights were mixed together and kept for '_4 hours. Theaverage error between the water saturations determinedby this method and the reai ones is only 1.660/0.utilized to measure pore liquid pressure. Generally, aThe S, -R/Ro relation in LNAPL-¥vater system isshown in Fig. 6. On the basis of Figs. 4 and 6, it can befound that the SwR/Ro curves in air-¥vater and inLNAPL,-water systems are simiiar. The difference is thatthe curvature in air-¥vater system is somewhat bi*_ger,although the conductivity of the L,NAPL and the air isne*'1igible compared to that of the sodium chlor'ide solution. This ¥vould be caused by the wettability. ofthe gildedtensiometer is designed to measure the pore waterpressure, and a hydrophobic tensiometer suitable formeasuring the LNAPL pressure, ¥vas not available. Thus,a ceramic cup of a normal tensiometer should be modifiedto be hydrophobic. There are some modification methodsproposed, one is spraying water-proof material to theceramic cup (Endo, 200'_; Kamon et al., ,_003) and theother is soaking the ceramic cup in a Glassclad 18 solution for 20 minutes, then oven-drying it at 1000C for I .5hours (Busby et al., 1994). The former method ¥vas select-electrode of the electrical conductivity probe (Kamon eted in the experiment. The schematic of a hydrophobical., 2003). Assuming that the vettability of the electrodeis'ater-¥vet in the water-air system, and the pore airtensiometer is sho¥vn in Fig. 7. The hydrophobic tensiometer consists of a porous cup sprayed ¥¥*ith the ¥vaterproof material, saturated with LNAPL., and a shaft filledhaving no excess pressure, the pore ¥vater forms ¥vaterfilm around the electrode, and the contact angle bet¥veen¥vater and the electrode becomes less than 90'. In the¥vith LNAPL and de ･aired ¥vater for the prevention ofLNAPL volatilization from the scre¥v-type connection¥vater-LNAPL system, Ivhen the pore LNAPL invadesbet¥veen the shaft and the pressure transducer, and theinto the water-saturated pore space ¥vith the pressurestabilization of the output signal from the pressure trans-hi**her than the pore ¥vater pressure and hits to a surfaceducer. S ) RELATIONS OF LNAPL39o-204'1!'L(3.5a,403CaCL2.5-60L:(Q, 2L=u'Q, i-5<-80a,L i,L-i o o20oo.5o408060100Voitage (mV)-25 - .1o -5 o I oVo[tage (mV)-2015Frg. 8. Calibration results of h)drophilic and h¥5Fig. 9. Calibration result of the tensiometer under negative air pressuresdrophobic tensiome-tersDuring measur'ement of pore liquid pressure, the signalfrom tensiometer recorded by the data logger was outputvoltage. A relation between voltage and pressure could beobtained in the calibration test (Fig. 8). The tensiorneteris calibrated under a positive pressure condition. It is verydifficult to calibrate a tensiometer' with ceramic cup fullysaturated with water or LNAPL under a negativepressure condition, because it is very difficult to measurethe variety of negative pressure of the ¥vater or LNAPL ine,U)Drain gs,,,,L':L(f5Opd/pe---We ingSlr_Shthe ceramic cup of a tensiometer ¥vith present testingtechniques.oSaturation1In this colurnn test, four tensiometers were usedtogether with one power supply. The output voltages oftensiometers are recorded by ¥vay of a data logger.However, the output signals from these tensiometers ¥villinterfere with each other due to the limitation of the data10gger, ¥vhich is a singie end data logger. Thus the isolation amplifier (Endo, 2002)'as utilized between thesetensiometers and the data logger. It resulted in the voltage of zero pressure of every tensiorneter being different.Ho¥vever' their slopes of relation between the voltage andthe pressure are almost the same. If the isolation amplifier is not used, the output voltage of every tensiometer atzero pressure is zero.When liquid was filled in the column ¥vithout. sand atdifferent liquid levels, the hydrostatic or LNAPL-staticpressures and their corresponding output volt.ages fromhydrophilic or hydrophobic tensiometers were measured.It was also found that ¥vhen liquid ¥vas purnped out of thecolumn (hydrodynamic or LNAPL-dynamic condition),the voltage from a tensiorneter is slightly different fromthat in a liquid-static condition even at the same liquidlevel. Figure 8 indicates that the correlation coefficientsrange from 0.9997 to 0.9999. Voltage-pressure relationsof hydrophilic tensiometers in hydrostatic condition andthose of hydrophobic tensiometers in LNAPL-dynamiccondit.ion ¥vere selected for Slp relation measurement.Although ¥ve can not calibrate under a negative liquidpressure condition, ¥ve could calibrate the pressuretransducer of a tensiometer under a negative air pressureFig. 10. Definition of p* and pd during drainage and wetting processes(Core .', 1994)condition. The calibration result is shown in Fig. 9. It isfound that the slope of the voltage-pressure relation is0.96, and it is very close to those of tensiometers calibrat-ed with the positive pressure. Moreover, the relationbet¥veen pressure and output ¥'oltagae is linear. From theseobservations, it is acceptable that the negative pressure isextrapolat.ed based on the voltage-pressure relationsho¥vn in Fig. 8.RESULTs AND DISCUSSIONSS-p Re!ations in Air- Water and LNAPL- Water SystelnsThe displacement pressure head, pd, is the capillarypressure at which the first desaturation on a drainagecycle occurs. At a pore space initially f'ully occupied withwater, a finite value of capillary pressure, designed as p*,must be exceeded before non¥vetting fluid can intrudeinto this elernent of the pore volume. The value of p* iscalled entry pressure. The definition of p* and pd is sholvnin Fig. 10. pd is some¥vhat smaller than p* (Corey, 1994).The measured S-p relations in the LNAPL-'atersystem under the drainage/wetting process are shown inFig. I I , 1 'here the one in the air-water systern under thedrainage process (Kamon et al., 2003) is also plotted.These STP relations are obtained at the same test condi- KAMON ET AL.40O:::160leoi40140O:C1 20Ec,_c,c'_100oLi*::u,co2u'Q,8ooo80SCLZ,:60CL40,v1 20B'LQeo40c5OO20oo,e 0,8 io.2 o,4Water Saturation20oo o.4 o.8 1o 2o.6Water Saturation(b)(a)Fig. Il. Measured S-p relations in Toyoura santi: (a) Fitted lvith VG model and (b) Fitted lvith BC modelTable 2. Parameters of Slp relations fitted lvith VG and BC models intlvo*phase sl.'stems¥IG modelA ,? S RBC model) h ;. S* R ! }OO'_1 7 37 O.15 O 78 39.21 4.15 O.14 O 770.039 7.77 0.lO O.91 18.21 2 71 0043 0.90LNAPL*¥va erAir-LNAPL2)O,,043 7 37 O.lO16.67 4.15 O.043Scaled parameters3) 0.021 7.51 O.OO O.90 38.04 3.79 0.00 O.85Air-¥vaterl) R is a correlation coefficient2) The Slp rela ions are obtained ¥vith scaling factor method3) Scaled S-p relation is obtairled aTnong aiF-1va er, LNAPL-1vaterinto the pore, is trapped with a degree of saturation evenwhen the water infiltrated again.Prediction of STP Relation in A ir-LNAPL Systel71The electrical conductivity probe can not be utilized inair-LNAPL system for measuring Slp relation becausethere is no pore water with some electrical conductivity inthe system. For a rigid porous medium it is only necessaryto measure STP relations for t¥vo of the three t¥vo-phasesy. stems (e.g., air-water, air-organic or organic-water).S-p relations for the third system may then be predictedtions including the type of sand used, the porosity of thesand samples, pore ¥vater, test equipments. The capillary(Lenhard and Parker, 1987b). In the scaling procedureproposed by Parker et al. (1987), S-p relations of twophase air-water, air-organic and organic- vater systemsare adjusted to obtain a unique scaled function for agiven porous medium after applying a linear transforma-pressure head in LNAPL-¥vater system at a _ :iven watertion to capillary heads such that:and air-LNAPL systemssaturation is slightly lower compared to that in air-¥vatersystem. This tendency is consistent ¥ 'ith the results byS, .(fi /1 )=S*(h*) (13a)Parker (1989) and Sharma and Mostafa (2003).S, .(ft ,./1To obtain the residual water saturation, t¥vo methodscan be utilized. One is to define residual ¥vater saturation,*+* ***. ) = S * (/7 *) ( 1 3b)S .(fi.. h.. ) = S *(h *) ( 1 3c)more or less, objectively by extrapolation using measur'edwhere a, o, and Tv refer to air, or'ganic substance, e.g.,data, and the other is to determine residual ¥vaterLNAPL,, and water phases respectively; Sj*=(Sj-Sj*)/saturation at some arbitrarily large capillary pressure(Corey, 1994). To define the residual ¥vater saturationwith extrapolation method, it should be noted that thisprocedure can become quite elaborate when only a smallportion of the soil-water retention curve is measured (vanGenuchten, 1980). In this paper, measured S-p relationdata ¥vas fitted to VG and BC models respectively withmodified Gauss-Ne¥vton method (Hartley, 1961). Thefitted S-p relations with VG and BC models are alsosho¥vn in Fig. 11. Fitting parameters of VG and BCmodels are sho¥vn in Table 2.Figure 1 1 also indicate that the S-p relation of ¥vettinprocess is much different to that of drainage process, andthe hysteresis is clearly observed, as reported in pre¥'iousresearches. This is because LNAPL, ¥vhich has infiltrated(1 - Sj*) is the effective saturation of ¥vetting phase j; Sj* isthe irreducible saturation of ¥vettin_9: phase j;ij is a fluidpair-dependent scalin_ factor; and S*(h*) is a scaledfunction bet¥veen the saturation of ¥vetting phase andcapillary pressure head. At a _g:iven saturation of wettingphase, Eq. (13) indicates that:fi*, /1*, =P･, h.,, p*.ll.. (14)For a rigid porous medium, scaling coefficients are relat-ed by Lenhard and Parker (1987b):1 , 1 1 (15)fi*,. ' fi*. p*wAccordingly, if fi*. is kno¥vn, at a gi¥'en saturation ofwetting phase, h** can be obtained depending on Eq. (14),, rS-p RFLATIONS OF LNAPLiso160o 140O 140So 120o 120:c41::'D'l'L:5su) Ieoq,u)iOO,,,a'tae'a* 80iL 80.60' _-, 60.015 40O 40's'S:,:2Q'g 2020oU)O0.6 1o 0.4 0.8oo.20.2o.6o.4o.81Effective Satu rationEffective Saturation(b)(a)Fio. 12. Scaled effective saturation-capillan.' pressure relations in To .'oura sand: (a) VG modei (p**,, = 1.942. P= 2.062) and (b) BC. model (P<,,* =l.739, fta*' = 2.352)OIsoIGO140140O1201 20::::Eo loo100*CDo:co 80:s80'LGo,,,CD,* eO:S*-40O 20,40ce20o0.2o.4 0.8 1Saturation(a)Fig. 13.ooo.2o.4o G08Saturation(b)Slp relations in Toyoura sand fitted lvith: (a) VG motlel and (b) BC modeland S-p relationship in air-LNAPL system can be¥vetting fluid is assumed to be a constant for all two-phaseobtained. The procedure for predict.ing STP relationshipin ail'-LNAPL system is described as follows:(1) Taking the air-1vater syst.em as a reference fluidpair system, and setting fi*w= 1.0;systems according to Lenhard and Parker (1987b), whichindicates that the residual saturation of wetting fiuid,(2) Fitting SrP relationship data in the air-¥vaterdata, in LNAPL-water system. Furthermore, the relationsystem to obtain S*(/7*);(3) Obtaining P･*+ depending on Eq. (13b) and fi*.depending on Eq. (15);(4) calculat.ing S.* and h** depending on Eq. (13c).where S.*=(S.-S.*)/(1 -S.*), and S.* is the residualsaturation of lvetting phase (LNAPL) in air-LNAPLsystem.In the air-¥vater and the LNAPL- ¥'ater systems, ¥vateris a ¥vetting phase fiuid; both air and LNAPL are nonwetting fiuids. Compared to air. LNAPL is a wetting phasefluid in air-LNAPL system. The residual saturation ofLNAPL in air-LNAPL system is assumed to be 0.10,which is the residual sat.uration of ¥vater fitted with testamong the scaling coefficient (Eq. (15)) is of a theory. Inthis paper, the S-p relation in the air'-LNAPL can not beobtained experimentally. Thus Eq. (15) is utilized to esti-mate the S-p relation in the air-LNAPL system.The VG and BC parameters of predicted Slp r'elation inthe air-LNAPL system are sho¥vn in Table 2. The scaledeffective saturation-capillary pressure relations are sho¥vnin Fig. 12, and all the fitted S-p relations in air-water, air-LNAPL and LNAPL-¥vater systems are shown in Fig. 13.It can also be found that descending sequence of capillarypressure head at a given saturation of wetting phase is in KAlvION ET AL.42i1o.8i3, O.8o 6.aCVCD O.e,:gG,>e, O.4o.4.>t*,:,a,o(O( O 2o-2oo-2e.4 o.8o,so1oWater Saturationo.2o.6 e.8LNAPL Saturation1(b)(a)Fig. 14.o 4Estimated k-S relations in To¥.'oura sand: (a) Lr ITAPI,*1vater s}stem and (b) Air*LF {'APL sl.'stemthe order of air-¥vater', LNAPL-¥vater and air-LNAPL,represented ¥vith a group of parallel capillary tubes lvithsystems. This tendency is also consistent ¥vith the resultsdifferent radiisho¥vn by Parker (1989) and Sharma and Mostafa (2003).conjunction ¥vith the more complicated pore geometryIn air-water and LNAPL-¥vater systems, the entrymodel of Mualem (1976). Due to the differences inparameters bet¥veen Burdine model and Mualem model,pressure and displacement pressure of air-water systernare larger than that of L,NAPL-water system. This resultsug (7ests that, in their corresponding aqueous t¥vo phaseThe van CJenuchten model is applied Inthe relati¥'e permeability of BC model is al¥vays smallerthan that of VG model (O_ ostrom and Lenhard, 1998).systems, L,NAPL is easier to displace ¥vater than airWith regard to the relative permeability, fe¥v literaturesduring the draina( ge process. In air-¥vater and air-LNAPL,are found on the differences bet¥veen the relativesystems, the entry pressure and displacement pressure ofair-¥vater system are larger than that of air-LNAPL sys-permeability measured by ¥vay of test and that predictedtem. This also suggests that LNAPL is easier to beby ¥vay of BC and VG models in porous media in ¥vhichLNAPL exists. Ho¥vever some simplified researches havedesaturated than ¥vater in their correspondin( - gases t¥¥'obeen made. In a fracture net¥ *ork, it ¥vas found that, bothphase systems.the VG and BC models *'enerally underestimate relatlvepermeability values, ¥vhile the BC model gives betterresults than the VG model (Liu and Bod¥'arsson, 2001).In porous media, the predictions based on the BC modelalso agreed better ¥vith exper'imental observations thanRe!ative Pernleabi/ity-Satu/'ation Relations in LNAPLWater anc] A ir-LNAPL SystelnsBased on Eqs. (8) to (11), a relation between therelative permeability and the saturation of ¥vettin*' phasecan be estimated based on the SrP relations obtained. Theeffective saturation of wetting phase j here is described as;Si* = Sj - Sj* ( 1 6)1 - Sj* - Sl*¥vhere, Sj* and Sj* are the irreducibie saturations of ¥vettin_"._phase ,j and non-¥vetting phase i, respectively. . Sj* can beobtained ¥vith extrapolation method and a good estimateof S;* for homogeneous and isotropic media is 0.15(Corey, 1994).the predictions based the VG model (Schroth et al.,1998). It can also be found that the BC model used byengineers successfully predicts the relative permeabilitycur'ves (Dana and Skoczy. Ias, 1999). In addition, modifiedprediction methods for the relative permeability includin*' the effects of ¥vettability, contact angle of soiiparticles, and DNAPL entrapment under ¥vater-DNAPLtwo-phase condition have been also developed (Demondand Roberts, 1987; Morro¥v et al., 1985). Ho¥ve¥'er, further research is required to develop the model to deter'mine the relative permeability of NAPL and evaluate itsThe relatlve permeability-saturation relations (k-Srelations) estimated for air-LNAPL, and LNAPL-¥vatersystems are sho¥¥'n in Fig. 14. The values of relativevalidity.permeability of nonwetting fluids (e.g. , air in air-L,NAPLFig. 15. It indicates that the relative permeability. of air issystem and LNAPL in LNAL- vater system) estimatedlar*'er than that of LNAPL m therr correspondmgwith BC model is slightly smaller than that estimated ¥vithaqueous t vo phase systems. It also sug*'ests that theThe differences of k-S relations bet¥veen alr-¥vater,LNAPL-¥¥'ater, and air-LNAPL systems are sho¥¥'n inVG model at a given saturation of ¥vetting phase (e.g.,relative permeability of the LNAPL is sli_2:htly lar*"eT thanwater in air-¥vater system and LNAPL in air-LNAPLthat of ¥vater in their correspondin_g: gaseous t¥vo phasesystem). On the other hand, the relative permeability ofwettin_g: fluid estimated with BC model is nearly the sameas that estimated ¥vith VG model.estimated based on Eqs. (8) to (1 1), these differences areThe Brooks-Corey model is applied in conjunction¥vith the Burdine theorem (1953), in ¥vhich, pores aresystems. Since these relative permeability values aredue to the shapes of S-p relation, ¥vhich includes theeffects of many factors (dynamic interfacial tension,viscosity, and so on) on the multiphase infiltrations rSlp RELATIONS OF LNAPLi1i , c.8? 0.8..:a''43'SG)g O.6o.6ha,o'La,> 0.4G)> 0.4!o)Ce 02a( o.2o0.6 1oo 0.2Saturation of Wetting Phaseo 4o.2 0.6 o.8 io.4o 8Saturation of Wetting Phase(b)(a)Fig. 15.Differences in k*S relations between air*water, LNAPL-water, and air*LN 7APL s)'stems estimated using. (a) VG model antl (b) BC modelproperties, obtained for the corresponding phase system.CONCLUSIONSIn this paper, the experimental system for' the measure-ment of migration character'istics of LNAPL (i.e., S-prelation) in LNAPL-water system in the porous mediumis described. Using this system, SrP relation in theLNAPL-¥vater system is characterized, and that in theair-LNAPL system is determined by the scaling factolmethod. The main results obtained are as follows:(1) A simple experiment device system ¥vith electricai(6) The k-S relation is obtained with parameters fitted¥vith VG and BC model in LNAPL-water and airLNAPL systems. The relative permeability of'LNAPL obtained using BC model is slightly smallerthan that obtained using VG model, and the rclativepermeability of ¥vater obtained using BC model issimilar to that obtained using VG model in bothLNAPL-¥vater and air-LNAPL systems.(7) The entry pressure and displacement pressure ofair¥vater system are larger than that of LNAPL-watersystem. It suggests that, in their correspondingaqueous t¥vo phase systems, LNAPL is easier toconductivity probes and tensiometers is effective fordisplace water than air at the beginning of drainagemeasuring S-p relation in LNAPL-¥vater systern.process. The entry pressure and displacement(2) Relations betlveen ¥vater saturation and outputpressure of air-water system are larger than that ofvoltage across a resistance attached to a calibratedelectrical conductivity probe were determined in theeasier to be desaturated than ¥vater in their corre-laboratory calibration tests. The output voltage¥vater saturation relation in LNAPL- vater system isslightly different from that in air-¥vater system. Inair-water system, the curvature of the relation isslightly larger.(3) The method for modifying a hydrophilic tensiome-air-LNAPL system. It also suggests that LNAPL issponding gaseous two phase systems.(8) The relative per'meability ofair is larger than that ofLNAPL in their' corresponding aqueous two phasesystems. In addition, the relative permeability of theLNAPL is slightly larger than that of water in theircorl'esponding gaseous t¥vo phase systems.ter to a hydrophobic one is proved to be effective formeasuring the pore LNAPL pressur'e even in thecase of a highly-viscous LNAPL such as paraffinliquid used in this study.(4) A method to separate sand particle, LNAPL andwater from the sand sample collected from thecolumn test ¥vas designed and pr'oved to be effectivein the laboratory experiments.(5) At a given water saturation, the measured capillarypressure in LNAPL-water system is slightly smallerthan that in air-¥vater systern. In reference to scalingfactors, Slp relation in air-LNAPL system is obtained. The descending sequence of capillary pressure is in the order of' air'-water, LNAPL-water andair-LNAPL systems. This is consistent ¥vith theresults by Kamon et al. (2003) and Sharma andMostafa (2003).I -ACKr l OWLEDGEMEN1'SThe authors vould like to acknowledge Dr. HuyuanZhang (Former JSPS Research Fello¥v, Graduate Schoolof Global Environmental Studies, Kyoto University,Japan) for his support in the laboratory test.NOTATIONA: fitted parameterB: fitted parameter": '-raviiationai accelerationh* j: capillary pressure head bet veen fluid pair of i and jJld: displacement presst re headh*+*: capillary pressure head in air-¥vaier systemho**: capillary pressure head in LNAPL-water systemh* : capillar_v pressure head in air-LNAPL s.¥'stem 44KAMON EτAL．permeab三1i［y of a med1し1m ん：eEective permeabi蕪t》・of i pl｝ase玉n muitiPhaseβow caseんci：んrilん『」＝reiatlvepermeabilityo顛o鷲wet￡ingP鼓ase’relatlvepermeab1lltyofwe［ヒingPhase／9） Dana，E．and Skoczy歪as，F，（玉999）：Gas relat玉ve permeability and porest田c田reofsandstones，／1π．ノ．RocんMθ‘h．M∫η．5ご．，36， 613−625．10）Demond，A，H、and Roberts，P．V．（1987）l An exam膿atlon of ’η：parameter臨ed wl漁van Genuc厩en model n：parameter撫edwl出、評anGenuchtenmodel μ勿α1∼ε∫α〃’．βε〃．，23，6王7−628．ρc：entrypressure11）Dullien，r．A。L、、（1992）：Porous Me嵌a：F1置”ゴ71／wη，∫poπ017ゴPo肥ρd：d呈splacement pressure S’ri’‘1∼’ヂθ，2nd ed、，Academ圭c Press，Califor鷺ia，USA。nonwe！t玉ng P蝕ase pressure12）Endo，K．（2002）：C負aracter1stics of DNAPL mlgration andwet亘ng phase pressure assessment of DNAPL distrlbu【lon1n a contam魚ated s1te，PhO P監：Pj： rela謡ve permeab玉韮ty relatio鷺s for two−phase負ow in porous me（i玉a，1㍉：capillary pressure between phases pa1r of’a職d／ D’55θ’”θ’ioη，KyotoUnlverslty，Japan（1nJapanese）．Pa、∼：cap玉11ary pressure bet、veen a玉r and、、「ater13） Gard扇er， 、V、 and Klrkham， D． （1951）l De葛ermlnat1o臓 of so11Po、、：capillary pressure be［、veen LNAPL and wa葛er 磁o1sture by neu［ron scatter玉ng，So’1Sc’．，73，39玉一40LPユo：capmary pressure betweeR air and LNAPL夏4） ｝｛ardey，H．O。（196王）：丁血e modi最ed Gauss−Newto【叢metbod for theharmonlc mean radius of curvature ofτ｝1e interface bαween 倣tingofno曲nearregresslonfunctlonsbyleastsquares，rθ‘1η10一 り R‡l凶aselandphase／ 〃1（∼’r’c5，3（2），269−280，harmonlc1nean rad沁s of cur、’ature of由e interface15）｝｛elml9，R．（1997）：M’〃fψhα5召r101∼レα1∼ゴ乃ηノ1∫ρo’トrP／oご8∫5θ∫’17r加 R：outPU［vo韮tage Ro＝referenceOUtpu置voltage S∼め5ど〃プiαごθ，Springer，Berhn．16）Host−Madsen，，」、and Je騎sen，K．冠．（1992）：Laboratory and S、、：watersaturation 3、、ご：e餌ect玉ve water saturation ∫ノyd∼ o1．，135，13−52． So豊：effect1ve saturatiou of LNAPL玉7） Huh，C．and 置〉lasoR，S、G． （1975）：A r玉gorous t飯eory of ring ∫」：saturation of wett魚9P翁ase／ Sβresidual satura首on tenslometrycolloldpolymer，S惚∼‘θ，253，566−58018）Iitanl，K，andM臓suda，H．（19フ5）：Au［omatlcprocessofpowder，efぞective sat雛rat1on of we−t玉厳g pbase 賜じ： Slrlresidual saturation of nonwe柱ing Pぬase’ 畠r＝ res玉dual saIuralion of wett玉ng Phase／S＊（1ブき）1scaied saturat玉oa＿cap玉艮ary島ead func“onvelociこyof伽ldinaporousmedium ど「i＝ 鷺umerical invest1gation of lmΣn玉sc1b叢e rnul【ip員ase 録ow in so貢，．ノ， Thθノ〉’んんα11ノぐ09』yo5hi111Z）置〃1ゐ’ゴ．，Japa鷺（in、lapa鷺ese）．19）Illangasekare，丁．H．，Ramsey，」．L，Jensen，K、H．andBut［s，M． B、（1995a）：Experimenta夏study of movement a録d distribution of denSeOrganlCCO飢amlPantS魚ぬe芝e1っge臓eOUSaqUlferS，ノ．CO’π． H』ド（1r．，20，1−25，total we玉ght of sample includlng sand，LNAPL and water20）Illangasekare，T、H、，Armbruster III，1…，ト，L and Ya葛es，D．N． 耳1s：welghtofsand （1995b）： Non aqueous pilase 翻uids 玉n heterogeneous aqulfers， rFLlwei黛嬢of LNAPL Experimental Study，／．E’1vかoη．五πg。，571づ79． α1parameter且貰ed wiI｝宝van Genuc｝1Ien（VG）model2玉）KamonM．，E陰do，K．andKatsumi，丁。（2003）：Measuringtheた一S一ρ βユ、、：a1卜water gu玉d pa玉卜（玉ependent scaling factor relaξions oR DNAPLs m玉gr飢ion，Eηg。Gθ01。，70，351−363、 β。、、：L醤APL−water丹uid palr−depende瓢scali鷺g factor22）Kecbavarzi，C．，Soga，K．and黛彗art，P。（2000）：Mult玉spectral玉mage β急Q：alr−LNAPL f沁ld palr−dependen重scalingねctor ana｝ys玉s職et簸od to de葛ermlne dynam玉c織u玉d satura額on distrlbution ρ、∼：dens貢y Qf waτer in two−d圭mensional threeイluid pbase flow labora覧ory experiτnents， ！｝1parame【er fitted w琵ぬBrooks and Corey（BC）model ノ。Co1π．κ．yゴ1㌦，46，265−293， ε1parame【erofVGmodel23）Len｝1ard，R，」．and Parker，」．C、（1987a）：A model for hysteretic μ1：viscosity of l P｝1ase coRst1tutive relaこ圭ons governing multip｝｝ase fiow＝2、 Permeability− rvloIall σi｝＝1nterfac玉al tens玉on between pぬases’and／ saturat玉o簾relatio取s， 昇■‘πθr∫∼θ50μ1一．Rθ5．，23，2197−2206． σ藷、∼：i磁erfaclaヒens沁nbetweenalrandwater24〉 Lenhard， R． 」． and Parker， ．L C． σo、、＝ln！erfaclal tension beτwee臓LN．A。PL a簸d waτer Pred玉ct玉o員 of saεuratio鷺一pressure relat1ons短ps in three−phase σ301 i鷺terfaclal tenslon between alr and LNAPL（王987b〉： r〉leasurement and pQrous media systems，ノ．Co11’．劫ノゴ1ト．，1，407−424．25）Lenilard，R．J．andParker，」．C．（1988）IExperimentalvaiidaこlonofREFERENCES1〉Arc為ie，G．E。（玉942）：Theelectrlcalresistivitylogasa蹴a1dindeter− mining some reservolr￠haracτeris【lcs，71四αη，∫、擁，1，λ4、E．，茎46， 54−6玉．2）Arc駐le，G、E．（1947）；Eleαrlcalres1stivityanaidlncQre−a鷺alysis i厭terpreta【ionヲ βμ”． 〆玉1η． ！1550c． Pαr． Gθ01．， ！1、1、ハ4，五二， 31（2）， 350−366．3）Bear，J．（1979）：Hアゴ1’σ疋イ1’050∫（｝rα’ηゴw醒θ1明，McGraw−Hl蹉，New the tぬeory of extePding two−P喪ase saζuration−pressure relat1o【1s芝o three−flu玉d p｝｝ase systems for 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nonaqほeQus−P註ase 1重qし1id in sandy E1∼9118，198，71−77。 porous med三a，〆窪ゴV、 HZα∼（∼1剛Rθ5α’11。ン21量145−157、6）Busby，R、D、，Lenhard，R J and Rolston，工）．薦．（1994〉l An invesヒ1−3玉）Parker，，」．C、，Le陰員ard，R．」．an（孟 Kuppusamy，T．（！987）l A ga賛on of saturation−capillary pressure reiations in two−a鷺d−t｝1ree parametric model for const貢u“ve propert玉es govern圭ng mult玉phase 恥ld systems for several NAPLs ln d簸erent porous medla，（yノ明α！副 肋∫α，33，570づ78。7）C駐apra，S．C，and Canale，R．P．（1998）l N∼〃ηθヂicα1z、4α11045、弄01「 織ow魚porousmedia，P伽θノ明Rθ50∼〃曙．Rθ5．，23，618−624．32）Parker，J．C（1989）：Mu1ゆぬaseβowandtransportinporous med三a，Rθv．Gθoρh．y5．，27（3），31B28． E∼19〃1θ（∼’3w∫f17P〆ogrα〃1111’119α1∼ゴS（∼ノ㌘wαノ’∈∼／4ρρ11‘θ’io115，3rd ed、，33）Reglnato，R、」．aRd van Bave1，C。H．M．（1964）：Soil water 508−5玉1， measure磁e蹴wl出gammaa［【enua［ion，Sol1Sd．So‘．，4’η．P’門oc，，8）Corey，A．丁、（1994）：漉‘hα鷹∫oゾ∫1η1ηZ5ごめ1θF1〃iゴ∫1ηPo1一α1∫ 28，フ21−724． ル1θ伽，WaterResoロrcesPublications，4レ43、34）Schro由，M．H．，Istok，｝．D．，Selker，，1、S．，Oosξrom，1〉L and濫 匿S一ρRELAτIONS OF LNAPL 、Vh玉te，M．D。（1998）：Muk澄uid痕ow in bedded porous medla＝ labOratOryeXperimen菰SandnUmeriCalSimUlaエiO鷺S，，4ごソ．肋’θ1’，，22，169−183． 1∼850μr35） Sharma，R．S．（2000）＝Keynoteぎ）aper：migra《ion of non−aqueous4537）TidweU，V。C ，and Glass，R、1。（玉994）l Xイay and vlsible11ghτ traPSmiSSiOnfOrlabOratOrymeaSUremen｛SOftWO−dimenSlOnal saturation痘eldsiluh1R−slabsys｛e磁s，μ／α1θノ｝Rε50μ1’、Rθ5、，30， 2873−2882． S‘’々α∼∼α！θoゾ0〃∼αノ∼，Balkema，Rotterdam，Tむe Netherlands，2，38）τopp，G．C ，，Davis，」、L、andAnnan，A．P．（1980）：Electromagnet− ic determination of soil water content：measureme瓢s in coaxial 571−583． transmlssion lines，研01θr1∼85α’”、Rθ3、，王6，574−582． pねase呈iquids玉n subsurface，1π乙（1〕oη∫Gθo一θn、アiノηπ1ηθn∼，八／μ5ごαf，36）S麺arma，R、S、andMostafaH、A、（2003）：Anexperimentalinvesti−39）vanGenucllten，M．τH．（1980）：Adosed−f−ormequa【ionfor ga亘on of LNAPL migratlon in an unsaζura［ed／saturated sand， predic［ing｛れe員ydraulic conductivity of uエ1saturated soils，So〃5ぐ乙 E1∼9、Gθo’．，70，305弓B． Soc、，〆4ルf，／．，44，892−898、
- ログイン
- タイトル
- A Comparative Study between the NGI Direct Simple Shear Apparatus and the Mikasa Direct Shear Apparatus
- 著者
- Hideo Hanzawa・N. Nutt・T. Lunne・Y. X. Tang・M. Long
- 出版
- soils and Foundations
- ページ
- 47〜58
- 発行
- 2007/02/15
- 文書ID
- 20979
- 内容
- rSOILS AND FOUiNDAT ONS¥rol. 47, No,4758, Feb 2007Japanese Geolechnicai SocietyA COMPARATIVE STUDY BETWEEN THE NGI DIRECT SIMPLE SHEARAPPARATUS AND THE MIKASA DIRECT SHEAR APPARATUSHIDEO HANZA¥VAi), N GEL NUTTii), Toivl LUNNEiii), Y. X. TANGl ) and MICHAEL LONG )ABS1'RAC1'A comparati¥'e study of the NGI Direct Simple Shear Test (DSST) and the Mikasa Dir'ect Shear Test (DST) isreported. Samples from Nor¥ve..*aian Drammen clay and Japanese Ariake clay vere subjected to both types of' test. Anevaluation of these test results and a theoretical considel'ation on the different shearing rnechanisms has sho¥vn thatalthough the DST give generally higher stiffness and strength than the DSST, these differences can mainly be accountedfor by the different shearing mechanisms and shearing rates. Sample disturbance due to transportation and handlingmay also be the reason for some of the diftbrence. A technique for evaluation of sample disturbance in the DSST ispresented and evaluated. Tests on undisturbed and remoulded Drammen clay consolidated to stresses much higherthan the in situ effecti¥'e overburden stress give almost identical r'esults. Thus the effects of sample distur'bance and insitu structur'e in the clay ¥vere eradicated.Kev words:direct shear test, direct simple shear test, Iabor'atory tests, sample disturbance, soft clays (IGC:C6/D6)ences in the shearing mechanism; techniques for extrusion, preparation and mounting of the sample; the reconsolidation process; sample dimensions; rate of shearing;the infiuence of remoulding; and testing of overconsoli-INTRODUCTIONLabcu'atory shear testing has become an integral partof many soil investigations for the determination of thestrength parameters of a soil. In Norlvay preference isgiven to the use of the Direct Simple Shear apparatus,¥vhich was developed by Bjerrum and Landva (1966). Forexample the mode of failure in the DSST is similar to thatdated soil. The pr'evious study showed that sampledisturbance was a likely cause of the difference bet¥veenthe sets of results. In this paper a technique for evaluatingsample disturbance in the DSST is pr'esented and evalu-encountered theoretically under the base of offshoreated.gravity structures or in translational type slope stabilityproblems. In Japan, the Improved Direct Shear appara-VALIDITY OF SHEAR TESTINGtus, developed by Mikasa in 1960 and described byTakada (1993), has gained increasing Popularity. TheDirect Sinzp!e Shear Test (DSST)In the direct simple shear t.est conditions of simpleshear strain are imposed to the specirnen, as shown inextensive application of the DSST and DST to bothonshore and offshore investigat.ions warrants a study intothe differences between these two tests. Such a study ispresented in this paper based on a programme of tests onFig. I (a). The verticai normal and horizontal shear forcesduring shear are measured and the shear strain, y*y, isgiven by u/ho for a shear displacement, u, and an initialt¥vo normally consolidated marine clays: Ariake clayfrom Japan and Dr'ammen clay from Norway. Tsuji et al.consolidated specimen height, ho. For simplicity undrained tests are simulated by holding the volume of thespecimen constant. In constant volume shear testing, it isassumed that the change in applied vertical stress as the(1998) have previously reported on tests carried out inJapan on both clays.This previous work is no¥v extended through a ser'ies ofcomparative tests in both apparatuses for the two clays,¥vith ¥vork carried out both in Nor¥vay and in Japan. Thisspecimen height (and hence volume) is maintainedconstant during shear is equal to the excess pore pressurethat ¥vould have been measured in a truly undrained testwith constant total vertical stress. This procedure wasstudy is aimed at identifying any differences in themeasur'ed test results and determining the causes for thesedifferences. Consideration is given to theoretical differj)ii:iiJ, ,used with the introduction of the DSST (Bjerrum andDeceased, formerly Technical Research Unl , Toa Corporalion, ,Japan.Apis Consulting Group, Canberra. Austraiia (formerl ,, Nor vegian Geotechnical Institute, NGI, Oslo, Norway).Nor¥vegian Geotechnical Institute (NGI), Oslo, Nor¥vay.Kanmon Ko¥van Construction Co , Ltd.. Japan (formerly Toa Corporation, Japan)_University C*oiiege Dublin (UC D), Ireland (i¥,iike.Long@'ucd.ie).The manuscript for his paper ¥vas received for revie¥v on August '-9, 2005; approved on July -'6, 2006,¥¥rritten discussions on this paper should be submi ted before September l, '_007 to the Japanese Geotechnicai Society, 4 38-2, Sengoku,Bunkyo-ku, 'Tokyo 1 12-001 l, ,Japan. Upon request the closing date may be extended one month.47 RHANZA¥VA ET AL.48yl cundrained tests are simulated by holding the volume ofthe specimen constant and recordin*' the chan_ :e ine:1!_ __vertical stress.ihf(aj Djrectsimple Sheav(b) Direct shear'The relative displacement, u, of the t¥vo halves of thespecimen is r'ecorded. Often this value is converted toa shear strain, y*.=ul/1, where h is the height of theelement of the specimen which is assumed to be under'*"oing the shear deformation, as pointed out by Wroth(1987). This value is conveniently taken as ho, the initialF g. 1. Conditions of (a) direct simple shear and (b) direct shearLand¥'a, 1966), and ¥vas confirmed in a comprehensivestudy on normally consolidated Drammen clay reportedconsolidated height of the specimen, although such anassumption must be given consideration ¥vhen interpretin*' stiffness par'ameters from direct shear data.The primary criticisms applied to the direct shear testrelate to the non-uniformity of stress and strain through-out the sample (Saada and To¥vnsend, 1981). This occursby Dyvik et al. (1987).Dur'ing shea distortion, the soil experiences a non-the specimen. Stress concentrations occur at the frontuniform shear stress distribution on the top and bottomfaces. For practical purposes, this state of stress isnormally considered close enough to the state of pureand rear edges of the lo¥ver and upper blocks respectively,giving rise to progressive failure alon*' the plane of shearing, so that the full shearing stren>'th of the specimen isshear to justify the inter'pretation of the test as under pur'enot mobilised simultaneously. Takada (1993), ho¥vever,uses photographic evidence from tests on alluvial clay tosho¥v that up to the point of failure, specimen deformations are remarkably uniform, and only at greater strainsdo non-uniformities become increasingly e¥'ident. Pottsshear stress conditions. To justify this assumption, Luckset al. (197,_) performed theoretical linear elastic analysesof the NCJI type DSST, sho¥ving that 700/0 of the samplevas uniformly stressed. Ho¥ve¥'er Saada and Townsend(1981) criticised some of the assumptions used in suc.hanalyses, particularly concerning the amount of fixity atthe boundaries, and cite the results of Wright et al. (1978)who used photo-elastic methods to illustrate a nonuniform specimen stress distribution. Nevertheless,results from tests conducted by Vucetic and L,acasse(1982) in the NGI apparatus on medium stiff clay atdifferent hei tht to diameter ratios have sho vn that thenon-uniformities do not significantly affect the measuredsoil beha¥'iour'. Airey and Wood (1987) per'formed directsimple shear tests on normally consolidated specimens ofkaolln using a specially instrumented apparatus. In thisway the stress strain behaviour of the central core of aspecimen could be determined representin*' that portionwhich most closely experiences a state of pure stress (orideal simple shear). The results ¥vere then compared ¥vithsimilar tests using a standard NGI type DSST ¥vhere onlythe a¥'era*'e stress-strain response throughout the ¥vholeas a result of the ri*･id platens ¥vhich are used to confineet al(1987) used finite element analyses to determine thestress state ¥vithin the rectangular shear box test, andcompare the stress-strain behaviour ¥vith that of idealsimple shear, shown in Fig. 1(a). An elastic-plastic soilmodel ¥¥*as used and the infiuences of volume chan'*e,initiai stress and strain sof'tening were examined. Theseanalyses indicated the propagation of highly stressedzones from the edges of the box, which gro¥vs and rotatesdurmg shear. This type of behaviour confir'med theexperimental rcsults of Morgenstern and Tchalenko(1967) ¥vho used optical examination of samples of kaolinin the direct shear box. Ho¥vever, despite such anomalousbehaviour, Potts et al. (1987) concluded that for the novolume chan*'e condition, the ultimate strength in idealsimple shear is only overestimated by direct shear byabout 60/0. Similarly. , Ioad displacement behaviour wassho¥vn to be consistently stiffer than for ideal simpleshear.specimen can be measured. Airey and Wood (1987)sho¥ved that the values of shear stren9:th and shearmodulus determined from the average stresses underpredict ideal simple shear values by about 100/0.Dil'ect Shear Test (DS T)In the direct shear test, t¥vo halves of a block of soil,rigidly confined, are forced to translate relative to eachother in the horizontal direction, as sho¥vn in Fig. 1(b).The vertical normal and horizontal shear forces appliedto the specimen are measured, and converted to average¥'alues of direct total stress, (T ' and shear stress, r* .These vaiues are then assumed to apply to the forcedplane of shear in the specimen and to be representative ofthe stresses experienced in the localised region ¥¥'herefailure occurs. In a similar procedure to the DSSTTHEORETICAL MECHANISMS OF SHEARAs shown above, evidence suggests that for tests inclay, the DSST underpredicts both the strength and stiffness of ideal simple shear, ¥vhile the DST overpredictsboth the strength and stiffness of ideal simple shear.Differences bet¥veen the DSST and DST can be attributedto different failure mechanisms. In the DST, failure ofthe specimen is forced along the horizontal plane. In theDSST, two possible mechanisms can occur; one oftranslation along a series of horizontal planes, sho¥¥'n inFig. 2(a), or one of translation aion*" vertical planes ¥vithan associated rotation of those planes, as shown inFig. 2(b). In the DSST either mechanism is possible, butan element of soil vill choose that mechanism 1 'hichs DIR照CT SH醸AR、へPPARATUS婆9鴨ξ葦第 びじ ソy陰 07 06 1 ／ 0508』☆1，』二『『『『『006 ノ軒・・2／ジイ篇i／ レ／ 04plusrot∂tion ／l I 〆／ 盤善 ／「 1 1021Q2040 3050∈詳ecヒ匹ve fRctio臼a翻91e p一 （dε9）FiG 3． ’lheo『e“ea鳳 rela重ionshipbetweenund『alned shea『 s｛『enαth DSST and DST （b）（a）σ‘o is the in situ vertica重effective stress，∫くb重s the in situFlg。2。 Possibleね蓋lure mecha臓ism during she食r（a）horizontgl planess芝ressratio，φ〆isthedrainedfrictionangleand（二』εmdC。are the swelling and compression lndlces respectively、 and（b）ver“c田planes Oh重a et a1．（1985）supPort their tkeoly by citing（iatεしfrom Ladd（1973）and Bjerrum（三973）forclays ofv＆r》・ingplastlci書y，includlng the plastic Drammen clay，used inrequires the least resistance，Le。the second one．Thisargument was 倉rst presented by de Josselin de Jong（1972），and taken up by∼Vroth（1984），who、veut on tosuggest that at重he ultimate stage oεa test，after fallure，the element resorts back to the且rst！nechanism．VVroξh｛his study．h圭s interesting to note that the expression forthe DSST（1温ers￡rom that for the DST by the term cQshβimhe dellomlnator．Hence coshβcan be considered＆sa theoretical correction factor bet∼∼ヂeen s封eεしr strengthsdetermined from DST and DSST．Wroth（1984）showscited experimentα玉resu蛋重s fronl Ladcl and Edgers（1972）that，for mosξclays，zi c＆n be well estimated as O．8．Thean（i Bor重n（i973）to confirm this behaviour．The imp正ica−variation of coshβwithφ’forεしrallge of Ko va至ues istlon is that w勤ile the DSST should give lower peakstrength童han the DST，the ultimate strengths should besimilar．presented in Fig．3． It is，however，difacu正t to quantify such（1星fferences iaTESTING PROGRAMMEstrength，because重he standard DSST and DST ap−正）θ5α●iρ1io110ゾ141’iα左θC1αyp＆ratuses（reported ln重his study）do not allow me＆sure− The site of Ari＆ke ls located in Hizen−Kashima，Saganlent of all the normal stresses。Hence it呈s not poss呈ble toPrefecture in Kyushu ls正and，Japan．Extensive use hasbeen ma（ie of the deposit for Ilesearch purposes．Forex＆mple a de重ailed descriptioll of lts mecha且lca1＆nddetermine the Iargest Mo封r’s circle of stress and corre−sponding shear strength．Using e星asto−plastic constitutiveequations， O紅ta et a1． （1985） （ieveloped theoreticalchemical properties is presented by Hanzawa et aLex夢resslons for the normα1ised unclrained strength（1990），Ohtsubo etε毫1．（1995）and Tanaka etεと1．（1996）．（τゼ／σ‘o）ofκo consoli（iεしted clays under P璽ane strain condi−So1ne圭ndex properties of the material used呈n this studytions，for the t、vo test types，as foHows：are shown on Fig．4（Tang et a豆．，1994）。1重is possible todivi（1e the deposit illto t∼vo stratal the upper clay，from O τr（1＋21ζ。）ルf〆 DSST 一； （1） σ〈℃3∬c・shβ重012m（1epth，an（1thelowerclayfrom12to18mdepth． τf（玉÷2κづ）ハ4θ｛■1than 150％near the surface to abouξ120％。TheI畠e玉s aIu the upper clay uatural water content falls fl’om more DST 一； 一 （2） σ〈・。 3∼百where： キ月「η。！1 β富 （3） 2ルノ（4） 1十2Ko Cs14響1一一一 Cc 3−sinφ’tionrαtlo（OCR）ofabout3．5closeξothesurface，（1ecreαsing with（iepth to a value of about1．5，sεθFig．4．（5）The water table is at about O．8m depth．Z）θ5α甲ip∼ioη0ゾ㌧乙）1藺α1η1nθ11C1αッ 6si11φ’ハ4置tively．Forboth strata the natura重wa重er content is greaterthan the liquid limit．Strain conn’oHed oedo1neter tests，reported by Tang et aL（1994），revea圭an overconsolida−3（1一κo）ηo薫corresponding increase in unit weight from aboud25kN／m3ξ013kN／m3．1航he lower clay重he water contentand unit weight are close to100％and14kN／m3respec−（6） The site where Drammen c玉ay samples were obtained islocated about45km south west of Os王o in毛he clty of HANZ,A¥VA ET AL50unit ¥veight of the soil is on avera_ e 16.7 kN/m3 and 19kN/m3 for the plastic and lean clays respectively. Fieldvane test results sho¥v significant scatter but typicallyincrease from about 22 kPa in the plastic clay to 30 kPaWater content(','.) , 't(kN '/Tn3)OO F-*Ho100 12 14OO 10H･-lo}=oh-Hoo ooeoeOeH-loh--HoI*-lo:)c::HHOhHOoOHohHOHHOHhCHOFig. 4. Basic physicaAriake clayO emg oedometer tests, reported by Lunne and Lacasse(1999) and sho¥vn on Fig. 5, indicate an overconsolida-Otion ratio of I .5 in the plastic clay decreasin*' to I .2 in theOHH) ¥v Wn w20OOOOh-Ho15values are lo¥v and typically increase from about 500 kPain the plastic clay to 900 kPa at 25 m.Preconsolidation stresses (pO from incr'emental load-O eh-- oo- 10PH HHThe field vane sensitivity averages7 in the upper clay and 3 belo¥v 10 m. Cone resistanceoeH-IoH-HoC:in the lean clay at 25 mlean clay. Measurements from in situ total stress cells andhydraulic fracture tests as ¥vell as special laboratory testssug:gest Ko Values of about 0.5.o : O R1 2OCR3 4properties and degree of overconsoiidation ofEquipment,for Direct Sill7p!e Sllear Testillg (DSST)These tests ¥vere performed at NCJI using the simpleshear apparatus ¥vhich is described in detail by Bjerrumand Landva (1966). The specimens ¥vere 67 mm in diwater cent nt (o 20o[f':)40 50OFw 'w., {kN/m})ameter (ar'ea of 35.3 cm2) and 16 mm in height, ¥vhich is ai 6 1 8 20height to diameter r'atio of 0.24. The specimen area isr = l1L Oe Qc¥'ertically and in simple shear. At the top and bottom ofi ',, ' )IoThis membrane allolvs the specimen to be defor'medas:kept constant by means of a reinforced r'ubber membrane, ¥vhich provides constraint in the radial direction.the specimen are filter plates. The filters and the draina_ :ef- eee ae a10tubes ¥vere saturated ¥vith water of the same salinity as thepore water in the clay. At the beginning of the test thespecimen is subjected to Ko consolidation stress in steps.Tests can be performed drained or undrained (as has beenaaoo p: stio cl yr- --J:)oTransition zon8Lean 'L r:ai1 5 c! aySrso20 L oao1oeeS20lL L"Jexplained earlier).eQaeooeEquipmellt ,fol' Direct S/7ear Testing (DST)eO 05 OCR1 is 2Fig. 5. Soi] profile at Drammen 'luseum Park/Danvikgnta si eFor this study DST tests were carried out at the TOACorporation in Japan, using Mikasa's Improved DirectShear apparatus. The apparatus is described in detail byTakada (1993). The cylindrical specimens ¥vere 60 mm indiameter and 20 mm in helght, ¥vhich is a hei**ht todiameter ratio of 0.33. The upper shear box is fixed to aDrammen. The site has been used by the Nor¥vegianloading plate ¥vhich is horizontally guided by a set of rigidGeotechnical Institute (NGI) for several earlier researchprogrammes on site investigations including samplin_-piezocone, Iateral stresscone, self-borin_ : pressuremeter,dilatometer, seismic cone, cross-hole seismic and fieldvane testin_g:, see for example L,unne et al. (1976). Anoverview of the ¥vork and a description of the characteristics of the clay are given by Lunne and L,acasse (1999).Several test site were used by NGI over the years but thesamples obtained for this study ¥vere from close to therollers. The lo¥ver shear box surrounds a loading plate ofslightly smaller diameter, fixed to a ¥'ertically guided rigidloading rod, through which the vertical normal load isapplied. Porous stones of rough silicon carbide are usedto transmit the shear force effectively from the loadingplates to the specimen surface. Loading is applied bytranslating the upper box over the fixed lo¥ver box at acity. centre at the lvluseum Park/Dan¥'ikgata site. The soilconstant rate. The apparatus ¥vas desi*･ned in such a ¥vaythat friction bet veen the upper and lo¥ver' shear boxes,bet¥veen the inside of the shear box and the loadin_ : plateprofile and some characteristics of this site are sho¥vn onand tilting of the loading plate could be minimised.Fi**. 5. In the top 5 m, sand and silty sand are encountered. Below this, the marine deposit consists of 5 m-7 mof soft, plastic clay o¥'erlying 35 m of soft to medlumstiff, Iean clay. The plastic clay has a natural ¥vatercontent bet¥veen 500/0 and 550/0, and the plasticity indexaverages 280/0 . The underl .,ing lean clay has ¥vater contentof about 300/0 and plasticity index of 100/0 to 150/0. TheSoi! San7p!il7gUndisturbed sampling of Ariake clay ¥vas performed toa depth of 15 m using a stationary piston sampler. Thesample tubes were made of brass, with a ¥vall thickness of1 .5 mm, an inside diameter of 75 mm and length of I m.On extraction, the undisturbed samples ¥vere carefully rDIRECT SHEAR AP P RATUSsealed ¥vith plastic film and placed in metal boxes.Paraf in 1¥'ax ¥vas used to seal and support the samples inthe boxes. The samples for testing in Nor vay ¥vere sent by5110 minutes immediately follo¥ved by a shear'ing load. Therate of shear under constant volume conditions ¥vas 0.25mm/minute (about 1.'_50/0 shear strain per minute).air freight. Undisturbed sampling of Drammen clay wasFifteen tests ¥vere carried out in thisalso perforrned using a piston sampler. The sample tubes¥vere made of steel, vith a ¥vall thickness of 2.6 mm, aninside diameter of 96 mm and length of I rn. On extraction, the tubes were sealed vith paraffin ¥vax. Thosedepths ranging from 6 m to 19 m.In the second series of TOA tests, the trimmings fromthe samples taken from depths from 6 m to 9 m (i.e.plastic Dramrnen clay) ¥vere remoulded and then consoli-samples f'or testing in Japan ¥vere sent by air freight.dated to a vertical effective stress of ,392 kPa o¥'er oneSalnp!e Prepa/'ationThe procedures used by TOA C*orp. for the DST differsorne¥vhat in preparation and mounting of the samplesfrom those used by NGI for the DSST. In the TOA Corp.method, the extruded sample is tr'immed by a ¥vire sa¥v toa diameter I mm greater than the specified diarneter for'ay on samples fromday, using the NGI procedure. On the follo¥ving day thespecimens ¥vere unloaded correspondin*' to a predetermined OCR. The rate of shearing under constant volumeconditions of 0.1 mm/minute (about 0.50/0 Shear strainper minute) was used. Seven tests ¥vere carried out in thisvay, at laboratory OCR values bet¥veen I and 40.In the third TOA ser'ies of DST tests, undisturbedthe direct shear test A metal ring, 20 mm lon' of exacttest diameter, and ¥vith a cutting edge is pushed do¥vnsamples of plastic Drarnmen clay were used, from depthsgently into the clay. The top and bottom ends of therespectively. The consoliciation procedure and the rate ofshearing ¥vere the same as those described for the secondTOA series of tests.specimen are trirnmed, and the ring is placed on top ofthe upper shear box. A circular disc is then pushed byhand through the ring, thus pressing the specimen intothe shear box.In the NGI method, the extruded sampie is pressed intoa cutting cylinder, mounted on ver'tical guides. Duringthis operation, the excess clay is cut a vay by a ¥vire saw orspatula. Top and bottom filter stones are mounted, andthe specimen is pressed gently into a suction cylinderholding the reinforced rubber membrane. The specimen,of 6m, 7m and 8m at OCR values of 1, 3 and lONo additional DSST tests were performed by NGI onDrarnrnen clay for this programrne. Rather, use wasmade of previous tests performed in Drammen clay for anumber of research projects. A selection of t¥vel¥'e tests¥ 'as gathered from these projects, corresponding to thetests per'for'med by TOA. In six of these tests (on bothplastic and lean Drammen clay) the specimens ¥vereconsolidated to in situ stresses using 4 Ioad steps, oversupported by top and bottom caps and the reinforcedone day, ¥vith shear testing performed on the f'ollo¥vin_"*.membrane sealed by o-rings, is then transferred to thedirect simple shear apparatus.day. Procedures of sample extrusion and preparationTest Procedti/'esplastic Drammen clay ¥vere first consolidated up to amaximum stress of 400 kPa over one day, follo ved byTests ¥vere performed ¥vith both the DSST and the DSTon specimens of upper and lo¥ver Ariake clay, and plasticand lean Drammen clay. For the Ariake ciay NGI carriedout 7 DSST tests and TOA carried out 14 DST tests. Thedivision bet¥veen uppez' and lo¥ver' clay occurs at 12.1 m.Prior to testing, all specimens ¥vere Kb consolidated up to(y(o, the estimated in situ ver'tical stress. This value was¥vere similar. Average str'ain rate varied bet¥¥'een 0.004and 0.080/0 Per minute. In a further six tests specimens ofunloading on the second day to a vertical str'ess corresponding to a predetermined OC*R, ¥vith shear testing onthe third day at a standard strain rate of about O.080/0 Perminute.estimated based on the values of soil unit ¥ 'eightEVALUATION OF SAMPLE DISTURBANCEmeasured for' each test. Consolidation of the NGI specimens was carried out with 4 Ioad steps; each load stepsug :ested that sample disturbance ¥vas a possible cause ofbeing applied for a minirnum of 30 minutes. The fullyloaded specimen ¥vas then left o¥'ernight before shear'ing.A rate of shear of about O. I o/) shear strain per minute ¥vasapplied to the specimens. In comparison, consolidationIn the previous study by Tsuji et al. (1998) it ¥vasthe difference bet¥veen the t¥vo sets of results. Here asimple technique for evaluarion of sample disturbance inthe DSST' is presented and evaluated. The same techniquecan be applied to the DST.of the TOA specimens ¥vas carried out ¥vith one load stepMany techniques are available for the assessment ofo¥'er 10minutes. Shearing ¥¥'as then immediately performed at a r'ate of 0.25 mm/minute (corr'esponding tosample quality. These include X-ray photography,about I .250/0 shear strain per rninute).son of shear ¥va¥'e velocity measured on the specimen ¥vithThe Drammen plastic and lean clays are separated by athin layer of sand/gravel at a depth of about 10 to I I m.TOA carried out three series of DST tests on this clay. Inthe first series, a consolidation procedure was used thatwas the same as that used for the tests on Ariake clay, i.e.undisturbed specimensvere reconsolidated to theirestimated in situ overburden stress, in one load step, formeasurements of initial suction in the sample, comparithat obtained in situ and the assessment of the stress/strain curves and par'arneters measured in oedometer ortriaxial tests (see for example Lunne et al., 1997; Hightet al., 1992).Early ¥vork (e.g. Andresen and Kolstad, 1979) arguedthat the volumetric strain, 8*., induced ¥vhen consolidating a sample back to the best estimate of in situ stresses 1HANZA¥VA ET AL.52'as a useful indicator of sample quality. For a highpiston (composite type'ith plastic inner liner) samplesquality sample 8,, should be close to zero. Lunne et al.(1997) e¥'aluated ¥vhich soil parameters were most systematically influenced by sample disturbance. The conclusion¥vas that the change in pore volume relative to the initialpore volume, Aeleo, is the best parameter t,o use, becauseit is reasonable to assume that a certain change in pore¥'olume ¥vill be increasingly detrimental to the particleskeleton as the initial pore volume decreases. Over theand on hi*･h quality Sherbrooke block samples. Fromlast seven years NGI has used Ae/eo to evaluate sampledisturbance on a number of onshore and offshore consulting projects according to the sample disturbancecriteria given in Table 1. Note for a particular clay¥vhereas the 54 mm composite samples are mostlymultiply Ae/eo by eo /(1 + eo) to get the criterla in terms ofFig. 6(a) it can be seen that the response of the blocksamples is stiffer, the peak shear stress is higher and thestrain to peak is lower than for the 54 mm compositesamples. Values of Ae/eo for these tests are plottedagainst maximum shear stress (ri, max) and strain atfailure (yf) on Fig. 6(b). The block samples fall in the"very good to excellent" or "good to fair" categories,classified as "poor". Peak shear stress r'educes and yfincreases systematically ¥vith increasing Aeleo. Theseresults confirm the applicability of this criterion to thetest results presented here.e+..Previously unpublished DSST results for the very wellcharacterised Ons y clay are sho¥vn on Fig. 6. The Ons ytest site is presently the main soft clay research sitecurrently used by the NGI. Like the Drammen siteTESTS ON ARIAKF. CLAYTest results from the DSST and DST tests on Ariakeclay are shown on Fig. 7. This includes the normalisedextensive research ¥vork has been carried out on the sitesince the late 1960's. It is located about 100 km southeastof Oslo, just north of the city of Fredrikstad. The site isunderlain by ¥'ery uniform soft to firm marine clays of theorder of 40 m in thickness and it is described in detail bystress at failure (rf/(7(o), the strain at failure (y ), thenormalised large strain strength (t,lcr(o) and the rigidityL,unne et al. (2003).parameters are sufficient to evaluate safety factor ofResults are presented for tests on standard 54 mm fixedindex (G50 /rr). Failure in the DSST and the DST has beendefined as the first point at ¥vhich the maximum shearstress is attained. In traditional design shear stren :_thstability. Currently numerical analyses, such as FEM, arebecoming more popular and in these analyses someTable l. Criteria for evaluation of sample disturbance (Lunne et al.,1997)measure of shear stiffness (or rigidity) is needed. Therefore stiffness some stiffness data in the form of G o/r isalso presented here. G50 corresponds to the secant shear1 e /eoO¥*erconsobdarionratio, OCR Very _'.-ood to GoodPoor*to Veryex'cellent* poor*f air1 2< O.04 O.04-0_07 O.07-0. 14 > O 142-4<0.03 O.03-0.05 : O 05O,lO >0.lOThe description refers to the use of the samples tor measurement ofmechanical properties.35from the t vo tests is smaller, especially for the lowerAriake clay. The contribution of severai factors to theobserved differences in stren*"th are no¥v gi¥'en consideration:S4 mm composit--"r35 rSherbrooke b!oek3af**'#25L f"'_ .' ,r"f' *L!ffF;: 20 '20i}r'{ Denotes peakT_i-' '- [ /)r""modulus at 500/0 of the failure stress.It is clear that the peak failure strengths from DSST aresignificantly lower than for the DST. Consistent ¥vith thediscussion above, the difference in large strain stren*'thsl30 -}e* +* *.¥ ¥ky.[I * i '25'' j{iii i!i20ixrl$!'L IS12>l ci158icOO!fr" " ?.55ii{-a; T [ I [ : T i12She r 5tr :in (*.) ((a))o5ii **i[l poor ii*Very good toexce *ntFi('.)i4Good to fairf I If i f I lo o 04 o 06 o 14o 08o 02olOo 2e f eG(b)6. Results of DSST for 54 mm conxposite piston samples and Sherbrooke block samples of Onsey clay: (a) stress-strain curves and (b) assessnlent of sample qualit .'i ;r;DIRECT SHEAR APPARATUSShear strengt ratio :f(' vO S r in to f i[ure, Vf ('/*)oO 02 04 06 08 Oo 3 6 9 12 IS4rge strain strength ratio, r(: 'a 02 a4 a6 08O I i [ l:oo4oeo4QOaF:8812oLi J8e)c1220$P6}2eo'*oe o o ,ler)16P20 -20Aele,differences in Ae/eo bet¥veen the DSST and DST do nota o 04 O 08 O 12 O 16 O 2clearly echo the differences in shear str'ength exhibited inFig. 7. However, variations in the testing procedures ¥villrnask the effect of disturbance: firstly, at similar depthsllboiIIIIIIlIIliI6)11I IIlaolol llll IolI Ariakei ol o I( I Il clayoa ill II ltIIII f¥1 li . I poor I Very poor20o Arlake8Shear strength and stiffness data for DSST and DST tests in Ariake clayI II Il Ariakeolower16acla yol o I I upperle I o I clay:(16 r4aoo) Ariake16204300aO OOe o clayFig. ?.1 OO 200cOe a :owero412 o- QOo Ariake16G !*faeOo o12Rigidity index,uppee oC:!oe a claye o oiayCQoovoOo o Ariakeo upperS53Very good toexcellent Good tofa'rthe consolidation stresses in the DSSThigher. Secondly, the consolidation tinlevere slightlyvas lon*'er; 1/'2to one day for DSST compared to 10 minutes for DST.An aiternative assessment of disturbance is acomparison of the shear strains to failure as plotted inFig. 7. Shear displacement in the DST has been conver'tedto a shear strain, as discussed above. In this plot, a moreconsistent trend is apparent showin*' a slightly higherstrain to failure for the DSST in all but one test.Qualitatively, this could be due to a larger degree ofsample disturbance in the NGI samples, possibly causedby the air frei**ht transportation.Collso!idation TiineThe effect of consolidation time was studied by Berre(1985) who sho¥ved from constant ¥'olume DSS tests inDrammen clay that a consolidation time of 40 minutesresulted in a shear str'ength that ¥vas only I . 50/0 Io¥ver thana similar test performed lvith a consolidation time of 18hours. Ho¥vever, from Fig. 7, the DST tests with theshorter consolidation times are exhibiting higherFig. 8. Assessment of sample qualrty of Ariake clal_ using qualit･.criteria of LunFre et al., 1997SalTlple Disturbancestrengths than the DSST. Hence the effect of differentconsolidation times is considered less significant thanother factors in assessing differences between DSST andDST.Values of Ae/eo during consolidation for DSST andDST are plotted in Fig. 8. For the upper clay, these dataplot mostly in the "ver'y good to excellent" or "good tofair" categories and there is a clear decrease in qualitywith depth. For the lo¥ver clay most of the specimens fallin the "very good to excellent" category and there is littledifference in quality with depth. The TOA specirnens aremarginally better than the NGI samples (average Ae/eo =0.043 compared to 0.046). It is evident however that the-,Rate of TestingHanzawa et al. (1990) investi**ated the effect of strainrate on Ariake clay from Kb consolidated triaxialcompression tests on undisturbed samples. Their resultsare reproduced in Fig. 9. Although the actual strain ratealong the failure plane (¥vhich ¥-vould be comparable tostrain rates in DST and DSST) will be different to thetriaxial results shown in Fig. 9, the effect on the shear !HANZA¥VA ET AL.54Shear strength ratio, T (; vO1O 02 04 06 08 1O l*= O9*o4r08*n_o8-07O OO1+*o.oo O1Strain rat5 (E1!min ):,,cLAriake c]al.'*oo*oo*othe DST (1.250/0/min) was approximately one order ofma*'nitude hi**her than DSST (0.10/0/min), and hence,from Fig. 9, the shear strengths for DST should beu ppercia yodto" IAr'akeel r o*astrength of tests carried out at strain rates of a differentorder of ma*"nitude should be similar. The strain rate forfactored by about 0.88 in the upper clay and 0.86 in thelo¥ver clay to compare with the DSST results. The use oftriaxial strain rates as a measure of rate effects in sheartesting is arguable, and it should be noted that thesecorrection factors are bein*' applied in the absence ofmore appropriate shear test data.[OFig. 9. Effects of strain rate for Ko conso]idated triaxia tests one*acroooAriakeiowercla yDSSTDSTDST Madifted =20Flg 10. ?, ormalised strength from DSST. DST and DST mod fied totake into account strain rate and shearin" mechanism effects forAriake cla¥_'from DST tests should be factored by 0.85 to give T,*, b.Shearing MechanismAs discussed above, O_ hta et al. (1985) present ananalysis ¥vhich can be used to quantify the difference inshear strength bet veen the DST and the DSST. Hanz,a¥vaet al. (1990) sho¥v that Ko for Ariake clay above 12 m is0.54, and belo¥v 12 m is 0.49. Also from Hanzawa et al.(1990) c{**) rs estimated to be approximately 27' and 28'for the upper and lo¥ver clays respectively (tc=triaxialcompression). Hence from Fi**. 3, the DST strengthsshould be factored 0.92 in the upper clay and 0.89 in thelo¥ver clay to compare with the DSST results.Combining the effects of strain rate and the shearingShear 1 fothdusComparison of shear moduli from DSST and DSTdepends, as discussed above, on the conversion of theshear displacement, in the DST to an equivalent shearstrain. Tan*" et al. (1994) argue that photographic resultsfrom a series of direct shear tests, performed by Takada(1993), verifies uniform specimen defor'mations up to rr.Values of G50 repr'esenting the secant shear moduluscalculated at 500/0 of the maximum shear stress, normalised by rr (i.e. G50/rf the rigidity index) are sho¥vn onand compared to the DSST strengths in Fig. lO. Theagreement is greatly improved. Ho¥vever, even theFi**. 7. The t¥vo apparatuses appear to be in good agreement, including the detection of the more rigid behaviourat 15 m depth. The avera*'e value of the rigidity index(excludin*' the test at 15 m) for DSST is 97 ¥vhile for DSTat corresponding depths it is 1 10. This suggests that bothmodified DST strengths are larger than the DSSTare similarly sensitive to the combined effects of r'ate andstrengths. It is concluded that the remaining discrepancyis most likely due to differences in the quality of the soilsamples, although it is also possible that the rate effects¥vere, in fact, Iarger than estimated, or the correctionfactors of the Ohta et al. method ¥ver'e too small.shear mechanism.mechanism, the DST strengths have been muitiplied by afactor of 0.81 in the upper clay and 0.77 in the lo¥ver clayCorrection Used in P/･acticeHanza¥va (199'_) studied the shear strength valuesTF,STS ON DRAMMEN CLAYSpecimells Conso!idated to in Situ StressesA summary of test results from the DST and DSST onspecimens of Drammen clay reconsolidated to in situstresses is shol¥'n on Fig. 1 1. Some¥vhat fe'er' tests werefor mobilised shear stren*･th (r**b) to be applied foravailable from the NGI sources than ¥vere performed byTOA. Nevertheless, a similar procedure of analysis hasbeen adopted as ¥vas discussed above for Ariake clay.example in design of embankments on soft ground. HeFrom Fi**. 11 again it is clear that unmodified DSTconcluded that in order to overcome the combined effectsstrengths are hi**her.obtained from three tests for three different marine clays.His objective vas to determine ho¥v best to obtain a valueof disturbance, shearing rate and anisotropy, results DIRECT SHFAR APPARATUSShear strength ratio. Ttc vO Strain io f i[ure .f ('/.)O 02 04 OJS 08 1 O 3 6 9Oa I f]f]ll fOoCorrected strength ratio2 15oRigidity irldexe vOO 02 04 Oe 08OoJ iGfT100 200300[ 1 1400r8141 vr'4ooe8ooO Piastio) Drarnrnen8F:p*Ooe eP astic8Drammen8l oeoelay44o:elayo' eo6)o,c:12:12e-51 -1212 r' s'l ' 'Lear?Dr mmenoo16elayoo16ooooooo20 ioFig. 11.o,ooO2048E:aaIIi11l04o 36l034l: 032l:DiE:c, 03lQ,l* 028e,'U) 026io 24eP_ o il olI PlasticiotI eo Pl DramrTlenj clayl li ll ll Le nl ll DrarT menlll t oooiayI lo ltI It o GblIo ll ll I o ( lo 2202O ooO1rT 5= 1==20l * l¥Very goad toexce lentlOO1O110iStrain rate ('/*Imin)e DSST results (NGl, 1972)Aver3ge sirai:FieF.oa, po0 very poor(300d toarFig. 12. Assessment of sample quatit) of Drammen clal.' using qualit)criteria of Lu Ine et al., 1997;;; __o ooili6oo 38i12a20'bShear strengt 1 and stiffness data for DSS'I and DST tests in Drammen claO 04 O 08 O 12 O 16 O 2Illil,lr *9oaOOe O*. :e/e,oocia y16e ooeooo20ooLeanDrarnmenr8te for!il DST fesvlts irpfesenstudy13. Effect of strain rate on the DSST shear stren"th ratio ofDrammen clav (N 'Gl, 1972)the two highly disturbed specimens at 18m to 19m).Similarly, the average value of shear strains to failure forDSST is 3.lo/o, and for the DST it is 4.20/0. This sug*'eststhat specimens tested by TOA ¥vere possibly some ¥'hatmore disturbed than those tested by NGI, i,e. theopposite to the finding for Ariake clay. Again this suggests some disturbance was caused during transportationSample Distu/'banceValues of Ae/eo during consolidation for DSST andby air freight.DST are plotted in Fig. 12. For the plastic Drammen clay,these data plot mostly in the "*"ood to fair" category. Aswould be expected the quality of the lower plasticity leanRate of Testingclay specimens are ¥vorse and Ae/eo Values for thismen clay using fast (O. i20/0 /min), medium (0.01 1 o/o /min)material fall in the "poor" category. The avera*･e le/eowhen consolidated to in situ stresses for DSST specimensand slo¥v (0.000360/0 /rnin) rates of strain. The specimensin both plastic and lean Drammen clay is 0.07. In com-stren*'th ratios at failure of these three tests are plotted inparison, the average value for DST is 0.09 (not includingFig. 13 a*'ainst the strain rate on a logar'ithmic scale.In an early study of the DSST, Lucks et al. (1972) performed three direct simple shear tests on plastic Dram-had been consolidated to in situ stresses. The shear *HANZ,A¥VA ET AL56From the figure, it can be seen that the change in stren*'th¥vith the lo*"arithm of strain rate is approximately linear,120ocR = Iof"and hence Fig. 13 can be used to give an approximate rate80correction factor for each test, although this ¥vill in¥'ol¥'ean extrapolation to account for the strain rates used ¥viththe DST series. The shear strengths for both DSST andDST, therefore, have been corrected for a test ¥vith a40;i -e- unstandard strain rate of O. Io/o/min.tLil --} 1m: ido{o254Disp!8eern nt (mm)Shea/' MlechanismKo for both plastic and lean Drammen clay, determined300from labor'ator'y triaxial tests (Berre and Bjerrum, 1973)200is 0.49. Plastic Drammen clay has c '*=25' and for leanDrammen clay c*'.= 26'. Hence using the chart in Fig. 3,the DST strengths have been corrected by a factor of O.871 oethe shear mechanism leads to corrected shear streng:thsas sho¥vn in Fig. 1 1. In this case, the corrected DSSTstrengths lie marginally above those for the DST. Thesmail discrepancy is possibly due to the slightly greaterdisturbance sho¥vn in the DST specimens. On thisrl acp2 s 3in the plastic clay and 0.88 in the lean clay.Combinin the effects of both the rate of testin( _ and+o *:L- i-1 ooo264Displ (;erTlent (mm)Fig. 14. Comparison of DST tests on remoultied and undisturbedspecimens of plastic Drammen clayevidence alone, the conclusion can be dra¥vn that thecauses for the sample disturbance in both the Ariake clayand the Drammen clay may be the result of sample transportation and handlin._,_a (due to air freightin_4ea) as opposedto variations in the sample preparation, mounting andQ2testing techniques.e_Sllear Moduhls- - eeA comparison of the rigidity index, Gso /rf, is also made10plastic and lean clays ¥'aries significantly ¥vith depth,Specinlens Conso!idated to Predete/'inined OCRSThese tests involved both undisturbed and remouldedspecimens of plastic Drammen clay, which ¥vere consolidated to about 400 kPa and then unloaded to predeter'mined OCR values. This value is much higher than the in3c4e3c40;e200150This similarity in results from both the DST and DSSTproperties.20ocR250 otrend is exhibited by both DST and DSST, but a closerall ciays, but ¥vill instead vary depending on the soilDSSTsOOreaching a maximum at about 12 to 15 m depth. Thistests ¥vas also found for Ariake clay (Fig. 7). Ho¥vever itis unlikely that the coincidence of the results ¥vill apply toDST rr:e(!= *eOin Fig. 1 1 , ¥vhere it Is e¥'ident that the rigidity of both theexamination of the differences in rigidity measured by thet¥vo apparatuses is difficult to make without further data.DST -oe1-o,)=ea100oo(50 -aQOO1020OCRFig. 15. Comparison of shear strength ratio at failure and rigidityindex for overconsolidated specimens of plastic Drammen cla)'cussed above. It is concluded that at preconsolidationpressures of 400 kPa any structural effects that may havesitu overburden stress and thus these series of tests are ofbeen present in an undisturbed specimen have beenvalue in deter'minin*' ¥vhether the same correctionsapplied as to the tests on undisturbed specimens consolidated to in situ stresses. A comparison has been made ofremoved. The consequence of this conclusion is that itshould then be reasonable to compare directly the DSSTresults from undisturbed specimens ¥vith DST resultsDST tests on undisturbed and remoulded specimens offrom remoulded specimens.Drammen plastic clay at O_ CR vaiues of 1, 3 and 10, andShear strength ratios at failure for DSST and DST areplotted against OCR in Fi**. 15. It should be noted thatthe tests plots are sho¥vn in Fig. 14. It is clear that there isno consistent difference in the measured stren*"ths or porepressures for the three OCR ¥'alues used. Note that herepore pressure is taken as the change in vertical stressrequired to maintain constant volume, as has been dis-most of the NGI DSST tests ¥vere performed on largerspecimens (50 c.m2 in area, 16mm hei_ :ht) than in theprevious series. Before any corrections due to shearingmechanism or strain rate have been made, the results;1 rDIRECT SHEAR APPARATUSreveal that there is not a significant difference between thet¥vo tests. At lo v OCR values, narnely I and ,-, the DSTgives slightly, higher strengths than the DSST, ho¥vever atOCR ¥'alues of 3 and greater, the DSST sho¥vs slightlyhigher strengths. This change in relative strength occurs5Tof shear strain, some disturbance in the clay samplestested ¥vas apparent. Since this disturbance vas moreevident in the Ariake specimens tested in Nor¥vay andthe Drammen specimens tested in Japan, it is tentatively concluded that the transportation and handlingapproximately at the OCR value when the Drammen claybe*'ins to exhibit negative rather than positive poreof' samples vas the primar'y cause of any such disturb-pressures at failm'e (Fig. 14). The analysis of Ohta et al.(1985) designed for cor'rection for' shearing rnechanism5) A simple sample disturbance assessment criterion,involving the normalised void ratio change (Ae/eo)bet¥veen DST and DSST ¥vas originally intended forrequired to consolidate the sarrrple to in situ stress, isintact OCR = I to 2 clays. It is not clearvhether it appliesto larger OCR cases. Gi¥'en the lack of an alternati¥'e thesame approach as used above (i.e. determination ofance.sho¥vn to lvork ¥vell for the DSST.6) Direct shear tests on undisturbed and remouldedspecimens that had first been consolidated up to1 /cosh fi using Eqs. (3) to (6) and Fig. 3) ¥vill be appliedstresses of 400 kPa resulted in stress strain plots andfor illustrative purposes. Furthermore in the absence ofreliable data, the correction for rate effects discussedstrengths that were almost identical. Hence, it isabove lvill also be applied. This correction corresponds toconcluded that after experiencing such high stresses,the efi cts of sample disturbance and in situ structuredifferences in rate of shear of about half an order ofmagnitude, Ieading to a correction factor of 0.93. Thein the clay ¥vere eradicated. Comparisons betweenundisturbed direct simple shear tests and remouldedmodified DST strengths are also plotted in Fig. 15. It candirect shear testsvere therefore considered valid.be seen that the DST and DSST strengths match ¥vell atOCR of i, but otherwise the DSST stren*'ths are somewhat higher.Values of rigidity index G50/Tf for the range of OCR7) After rnaking corrections for diff:erences in thevalues tested ar'e also shown in Fig. 15. Despite a consis-in fact, corresponded approximately to the OCRtent dift rence in stifihess between DST and DSST,values where pore pressures at failure became negative), the DSST gave some¥vhat greater stren_g:ths.Variations in stiffness for the range of OCR valuesprobably due to the fundamental difference in the shearing mechanisms, the variation in stiffness ¥vith OCR isremarkably similar for the two tests.Cor TCLUSIONSThe comparative study into the differences bet¥veen theDST' and the DSST has revealed the follo ving conclusions:1) For clays consolidated to in situ stresses, the directshear test (DST) gives higher estimates of strengthand stifihess than the direct simple shear test (DSST).The difi rence bet¥veen the tests can be accounted forby the different shearing mechanism imposed toshearing: mechanism and rate effects in the DST andDSST, shear strengths were similar for OCR valuesof I and 2. For OCR values of 3 and greater (¥1'hich,tested ¥vere remarkably similar.8) It should be noted that the modif'ying factorspresented here, 'hich are used for DSST/DSTcomparative purposes, are not necessarily applicableto pr'actical strength determination in Japan. In theauthor's experience, and as detailed in Hanza¥va(1992), DST shear strengths are actuaily used indesign by multiplying by an overall correction factorof 0.85.REFEREN_ CESspecimens, the difi r'ent rates of strain used, andpossibly sorne contribution due to different degreesl) Airev. D. ¥¥t. and ¥¥*ood, D .¥e. (1987): An evaiuation of direclsimpie shear tes s on clay, Ceorechnique, 37 (i), 25-35'_) Andresen. A and Kolstad, P (1979): The NGI 54 mm samplers forof distur'bance in the clay samples tested in Japan andundisturbed sampling of clays and representative sampling ofNor¥vay.2) The different shearing mechanism bet veen the DSTand DSST can be quantified by adopting an analysisproposed by Ohta et al. (1985) formulated for Kbconsolidated clays under plane strain conditionscoarse material, Proc. Int. S_1'inp.. Singapore, 13-'_1. Also in NGJusing elasto-plastic constitutive equations.3) The eft ct of performing tests at different rates ofstrain is difficult to compare accurately when assessing the DST. This is because there r'emains uncertainty in conver'ting shear displacement to shear strain.Nevertheless, in Ariake clay, corrections based upontriaxial strain rates result in an improved agreementbetween DST and DSST strengths.4) Evidence f'rom the tests in Ariake and Drammen claysuggests that, after making appropriate correctionsfor the shearing mechanism and differences in ratesPub!ication No. 130.3) Berre, T. and Bjerrum, L. (1973): Shear strength of normallyconsolidated clays, Proc. 8th ICS_iVIFE, i¥,losco¥v, 1.1, 3940.4) Berre, T. (1985): Eff ct of consoiidation time on triaxial and directsimple shear tests, JVGI Intenla! Report. No. 56103-29_5) Bjerrum. L, and Landva, A. (1966): Direct simple shear tests on aNor vegian quick clay. Geotechnique, 16 (1), l'_)O.6) Bjerrum, L (1973): Problems of soil mechanics and constructionon soft clay, Proc. 8tll ICS_,VFL', ivlosco¥v, 3, 109l59.7) Borin, D_ L. (1973): The beha¥'iour of saturated kaolin in the simpleshear apparatus, PllD Thesis, University of Cambridge8) de Josselin de Jong. G. (197'_)): Discussion. Proc. Roscoe -'Venloria!S_v,np. Stress-Strain Behaviour of Soi!s, Cambrid**e, '-58261 _9) Dy¥'ik, R., Berre, T , Lacasse, S. and Raadim. B. (1987): Compari-son of truly vndrained and constant volume direct simple sheartests, Geo!ec'hnique, 37 (1), 3-lO.lO) Hanza¥va. H.. Fukaya, T. and Suzuki, K. (1990): Evaluation ofengineering properties for an Ariake clay, Soi!s and FbLindations, 58HANZ、AWA ET AL、 30（4），玉1−24． 613−6王6．11）Hanzawa，賛．（1992〉＝Anewapproac厭odetermlnesoilparameters22） Ohtsubo，i〉L，狂gas簸玉ra，K。a【1d Kas｝1玉ma，K．（1995）＝Depos辻玉onai free from regio鷺al varia亘ons in so涯 behaviour and 【ec自nical a職d posトdeposi“onal geoc簸em玉slry，and 玉ts correlat1on 、、・ith the quality，So’Z∫αη4Fα〃1ゴ副o’∼5，32（1），7レ84． geotechn藍cal properties of marl鷺e clay 玉n Ar玉ake bay， ，lapan，12）封lght，D W．，Boese，R、，Buτc蝕er，A．P．，qayton，C．R、至．and Sm紅血，P．R．（1992）：DisturbanceoftめeBo“1kennarclaypriorto 0θo∫θchη’（1ε’θ，45（3），509−523． laboratory testing，（フθo∫θ（｝h1∼1（1∼’θ，42（2），圭99−217． ele磁e窺a鷲alysisof由edirect5員earbox【esτ，Gθo’θchηゆθ，37（1），13）Ladd，C．C、a“d狂dgers，L、（1972）＝CQRsolidatedundra鎗eddlrect simples鼓eartestsonsatし王ratedclays，M／7Rθ5θσκhRθpor’， R72−82、 王1−23，14）Ladd，C C、（1973）：Dlscussion，mai糞session，8∼h／（フS1》E万， 740，7−77． Moscow，4，108−115，15）Lucks，A．S，Christian，J．τ、，Brandow，G．E aΩd Hoeg，K23）Potts，D．M，，Doun茎as，G、T．a簸d Vaughan，P．R．（1987）：F鮫玉te24〉Saada，A，S．a賞d Townsend，F、C．（1981）＝State of the art： Iaboratorys【rengthtestlngofsoils，．4S7MSρθc．τθ‘h．Pゆ1．，No、25） Takada，N。（1993）：！〉likasa’s direct s員ear appara1us，test pro（：edures and resu置亡s，（｝（ヲo’θ（ン11． 71θ5f．／．，16（3），3茎4−322． （王972）＝S【ress cond虻ions重n NGI simpie shear test，1’∼∼．Co’∼∫．So’126）Tanaka，｝｛．，S｝玉arma，P．，Tsuchida，T、and Tanaka，NI．（1996〉： Mec1；．FoHηゴ。0’v、，ASCE，98（SM1），155一玉60、 Comparat隻vestudyonsamplequahtyusingseveraldl琵ere瓢types16）Lunne，T．，Eide，0．anddeRulter，」，（1976）：Correlat1onsbetween of samplers，So’Z∫σ1∼ゴFα“1面∫’0115，36（2），67−68． cone reslsIance and vane s晦ear strength1n some Scand1nav茎an soft27）Tang，Y．X．，Hanzawa，H，andYasuhara，K。（1994）＝Dlrectshear tomediumclays，Cαη．Gθorθch．／．，13（4），430−44玉， and direct s王mple shear test resuks on a Japanese marine day，1S−17）Lu孤e，T．，Berre，τ。a職d S［randvik，S．（1997）：Sample dlsIurbance Hoκたα’ゴo’94． e餌eαs玉n sof110w plast玉c Nor∼、7eg玉an clay，Pro‘．R8ご8’π1）θveloメ？一28）■suji，K，，Tang，Y．X．andL犠nne，丁．（1998）＝Acomparatives【udy ’ηθノ∼’5’η50”‘7ηゴPovθ1刀θn∫ル1θご11αn’c5，Brazi1，June，8レ102． onshearstre篇gthofmar1neclaysbydirectsllearandd量rectslmple18）L凱ne，τ．andLacasse，S．（玉999）：GeotechnlcalcharacterisIlcsof s簸eauest，，∫．Geo鷹11．Eη9喀，JSCE，589（III−42），275−285（iR low plas重圭city Drammen c蓋ay， Chα1ηcrθπ∫σ”011 0ゾ「Soゾ1’ 1》α’’”1θ Japal｝ese）． αのン5（eds．byTsucぬidaandNakase），Balkema，Rotterdam，33づ6．29） Vuce百c，1〉L a盤d Lacasse，S．（1982）：Spec1men size effeα玉a simple19）Lunne，τ．，Lon9，M．and罫orsberg，C、F．（2003）：Character1satlo鷺 sllearIest，1ηr．Gθ01θc11．E119，ρ’v．！13Cど，108（GT12），1567一玉585． and eng1neering ProperIies of Onsのy cIay，ノニ》ヂoc．1n∼、rIzo∼κ5hoρon30）Wrig壌，D．K．，Glibert，P、A．and Saada，A、S（1978）：Shear Chθ’「βαθ”なα’io〃 01∼ゴだπgi11θθ1”〃7g Pro∫7θ∼’1θ5 0ゾNα11〃門α1So’Z∫ devlces for determlning dynamlc soil properties，P’Poぐ．Sρθc．Co’4． r？〉α’置〃wl So〃52002，ワ（eds．by Ta鷺，丁．S．et aL），NUS S1ngapore， だσπ1∼（∼μακθEη9’ηθθパ179α’1ご50’1Z）Lγ∼101η’c∫，ASCE，Pasadena，2， December．Pubhs致edbyBalkema，1，395−428．20〉Morgensξem，N．R．and Tc負alenko，1．S．（1967）：Mlcroscoplc 1056−1075， strucIures呈n kaolin subjected to direct s鼓ear，（二7θo∼εch∼∼’（1∼∼θ，17（4）， Rankine Lecture，0θo∼θchη’‘7μθ，34（4），449−489．3烹）Wro由，C．P．（1984）：The1nterpretat1onoflns1tusoihests，2紬 309−328，32）Wro由，C．P．（1987）：丁鼓e be瓦aviour of normally consolidaIed cla｝・2玉） Ohta，H．，N1s益貸ユara，A．and r〉lor疑a，Y．（1985）：Undra呈員ed stab玉1iζy as observed1鷺undra玉ned direct shear tests，Gθo’（アご11η’（1∼’θラ37（1）， ofκo consohda【ed cla》βs，」D∼oご． 11’1∼1CSA4Fだ，San Francisco，2， 37−43、甕
- ログイン
- タイトル
- Induced Swelling of Kaolinitic Soil in Alkali Solution
- 著者
- P. V. Sivapullaiah・Manju
- 出版
- soils and Foundations
- ページ
- 59〜66
- 発行
- 2007/02/15
- 文書ID
- 20980
- 内容
- rSOILS AN. D FOUNDATIONSVol47, Nol, 59-66, Feb. 2007,Japanese Geotechnical SocietyINDUCED SWELLlNG OF KAOLINITIC SOIL IN ALKALI SOLUTIONP. V. Sl¥'APULLAIAHi) and MAN'JUii)ABSTRACTUnexpected s¥velling induced in foundation soils can cause distress to structures founded on them. In this paper, thes velling of kaolinitic soils due to interact.ion ¥vith alkali solution has been reported. The induced swelling is attributedto the formation of new minerals, ¥vhich has been confirmed by X-r'ay diffraction patters and SEM studies. Tounderstand the effect of alkali concentration and duration of interaction, two series of consolidation experiments havebeen carried out. In series I , the specimen were r'emoulded ¥vith ¥vater and inundated ¥vith alkali solutions and in series'_, the specimen ¥vere remoulded and inundated ¥'ith same alkali solutions. A steep compression during loading cycleand no abnormal swelling during unloading cycle has been noticed for the specimen remoulded ¥vith water andinundated ¥vith I N NaOH solutions. The steep compression is due to the segregation or break down of clay mineralsdue to alkali interactions. In case of specimen inundated ¥vith 4 N NaOH solutions, abnor'rnal swelling has beenobserved durin*' unloading cycle of the consolidation test. Ne¥v minerals are for'med on interaction of soil ¥vith 4 Nsolution as confirmed by X-ray diffraction patterns. These minerals are kno¥vn to have very fine pores and possess high¥vater holding capacity. The differences in the amount of s velling of samples remoulded ¥vith vater and r'emoulded¥vith alkali solution are due to variations in the concentration of alkali and duration of interaction.Key words: alkali, consolidation, kaolinite, mineralogy, swelling, zeolite (IGC: BIO/D2/D,3/D5)industries such as i) Paint and dyes ii) Paper and pulpindustries iii) Cotton mills iv) Aluminium industries andso on. From an engineering point of vie v, understandingof the mechanism of heave is essential if distress due toIN1'RODUCTIONThe soils in the bases of buildings and struct.ur'es ofindustrial plants, dams, and dikes of industrial se¥vagedifferential s¥velling/settlement has to control.collecting canals are frequently subjected to the action ofdifferent solutions of salts, acids, and alkalis, as a resultof ¥vhich their composition, physico-chemical properties,Numerous researchers have explored that kaolin clayinteraction with alkali solutions leads to the formation ofzeolit.e (Aznar and La lglesia, 1985; Madani et al., 1990;and geotechnical behaviour under*'oes significantchanges. Unexpected volume chan*'es occurring inRocha and Klinowski, 1991; Gualtieri et al., 1997;on thern. Depending on the composition and propertiesAkokelar et al., 1997; Demortier et al., 1999). Zeolitesare hydrated aluminosilicates 1 'ith symmetrically stackedof the soils and of the solutions penetrating into them,alumina and silica t.etrahedral, with open and stable threethe soil may swell or settle.dimensional honeycomb structures ¥vith a negativefoundation soil can cause distress to structures foundedThe volume changes caused by applied stresses andcharge, neutralized by ions such as sodium. The phys-moisture changes, ¥vhich are very significant for soilscontaining expansive minerals, are less important foricochemical conditions under ¥vhich zeolites are obtainedfrom kaolin are ver'y similar to those used in geopolymerization. Geopolymer is the name that has beensoils containing non-s¥velling clay minerals such askaolinite. Ho¥vever, the volume changes in these soilsapplied to a ¥vide range of alkaline or alkali-silicateactivated aluminosilicate binders . The geopolymeric bind-due to chan*'e in chemical environment may becomeer phase is often described as "X-ray amorphous".important. It is kno¥¥'n that the non-slvelling soils canexhibit higher s¥velling in fluids ¥vith low dielectricHowever, many authors have noted formation of phasesdescribed as either semicrystalline or polycrystalline(Palomo et al., 1999; Van Jaarsveld et al., 2002; Rowlesand O'Connor, 2003) in geopolymer. Provis et al. (2005)constant such as carbon tetra chloride (Sridharan andRao, 1973; Chen et al., 2000). Rao and Rao (1994),Sinha et al. (2003), and Sivapullaiah et al. (2004) havereported the swelling of kaolinite rich red soil due tointeraction ¥vith caustic soda. Contamination of foundation soil with alkali solutions can occur froui varioushave reported that *･eopolymers actually containnanocrystalline zeolites. Hence the difference bet¥veengeopolymers and zeolites is rather small." Associate Prof ssor, Departmem of C*ivil Engineering, Indian Institute of Science, india (siva@civiLiisc,ernc ,in).**Research Student, dittoThe manuscript for this paper ¥vas received for revie v on September 17, ,_005; approved on September 5, 2006.Written discussions on this paper shou d be subrnitted befbre September 1, 2007 to he iapanese Geotechnical Society, 4 38*2, Sengoku,Bunkyo-ku, Tokyo I 12-001 1, Japan. Upon reques the closing date may be extended one month_59 I 1SIVAPULLAIAH AND60,lANJUTable '-. Chemical composition and cation exchange capacrt¥.' of theTable 1. Ph)'sical propert¥.' of ti]e soilssoilsPro pertySpecific gravit¥.-Red earth soil Kao]inite2 67Clremicai composition (O/･)Atterberg's limitsLiquid limit (LL), '/-38Plastic limit (PL), ollo19Non-plasticPlasticit .' index (PI), o/o19Non-plasticShrinkage limit (SL), 9'-55036Slvell bet]aviourFree slvell index, g/ccl .214Grain size distributionSilica (SiO.) 62.358^05Ferric (Fel03) 2.61Titanium (TiO.) O 21Potassium (K.O) O_42Sodiurn(Na20) O.32*Magnesiurn (N'IgO) I .67Alumina (Al.O )7 )15Silt content, 75 ;!m-2 um (ollO)4464Fine sand content, O,,_7 mm-75 !!m ( /e) 3421CL49 7041 .80Calcium (CaO) 5 91Loss on ignitian S.41O .30l .OOO.40O_30O OOO.057.40Cation exchange capacity, (meq/lOO g)TotaExchan**eable ionsClay contem, <7-,!m (0/6)Unified soil classificationRed earth KaoliniteParametcr,-,55I O . 84Sodium,82Potassium,NaK OO.38Caicium, Ca 6^86Magnesium, ivlg I .783 ,, 700.40o_502.00o.80CLverted other primary minerals into clays oxides. TheStandard proctor's parametersMax dry unit ¥veight, (kN/ms)17.813 5Optimum ¥ 'ater content, o,fo1828Singh and Kolay (2002) ha¥'e reported the effect ofz,eolitization on the engineering properties of fly ash^Sivapullaiah and Manju (2005) have studied the effect ofzeolitization on the basic properties of kaolinitic soils.Ho¥vever, the eff ct of z,eolitization on the engineerin aproper'ties of kaolinitic soil is not been studied so far.Invesngatron has been carried out to understand theextent of volume change in kaolinitic soils under theactlon of high concentrated sodium hydroxide alkalisohrtions. Understanding the mechanism of changes isnecessary to su_g_gest remedial measures to overcome thedistress caused to structures founded on these soils.physical properties of the soil used are reported in Tablel . Silica, alumina, iron and other chemical constituents inthe soils ¥¥*ere analyzed according to standard methods(Hillerbrand and Lundel, i953). The r'esults have beenpresented in Table 2 and ar'e based on the oven-dried¥veight of the soil at 105'C. The cation exchange capacityof the soils ¥vas determined as per' Jackson (1958), alon_g:vith the type of cations, are reported in Table 2.F!uic!s UsedChemically pure sodium hydroxide pellets ¥vas obtained from Glaxo L,aboratory, India. The fluids used¥vere 1) Distilled water, 2) i N Sodium Hydroxide and 3)4 N Sodium Hydroxide. Concentrations of sodiumhydroxide that many industrial processes use are near 4N. Aluminum extraction plant (Whittington and Cardile,1996) and nuclear ¥veapons industry (Qafoku et al. , 2004)are using approximately 4 N sodium hydroxide solutionMATERIAl,S A_ND MF,THODSSoi! UsedA natural soil, red earth and commercially avaiiablepure kaolinite were used. The red soil used in the study¥vas collected around the soil mechanics iaboratory,Indian Institute of Science, Bangalore, India. The soil¥vas collected by open excavation, from a depth of onefor their different process. When there is any leakage atthese industrial sites, soils at closer surrounding becomecontaminated with a high concentrated sodium hydroxidesolution. And considering the field condition, the contaminants become diluted due to the seepage of surfacemeter to natural ground ievel. The soil ¥vas air dried andwater and rain¥vater into the soil. And hence to study thedifferent concentration effect, I N and 4 N concentratedsolutions have been considered seeing the possible level ofalkaii in the actual site. Sodium hydroxide solution wasused after sievin9: throug:h Indian Standard 4･_5-micronprepared by dissolvin*' the required amount of Analarsieve. The grain size distribution of red earth, andGFade sodium hydroxide pellets in distilled ¥vater.kaolinite has been carried out as per Unified classificationsystem and are presented in Table 1. X-ray diffraction ofboth the soils has sho¥vn peaks at 7.,_ A, 3.6 A and 1.49A, which are diagnostic of the twolayered kaolinitemineral. The major minerals present in red ear'th,ho¥ve¥'er', is quartz and sho¥ved stron*" peaks at 3.36 Aand 4.,_8 A. It is not surprising that quartz is present asthey are the most ¥veathering-resistant primary minerals(Dixon and Weed, 1989) and tropical ¥veathering has con-M:ethoclsX-Ray Diffraction AnalysisRandomly oriented samples ¥vere prepared by manualgrinding in a porcelain mortar and pestle to powder formand subsequently pressing the material lightly into r'ectan-( -ular _ lass holders. Samples were scanned from 3'2e to80'26 using Philips X-Ray diffractometer model P¥V3710i, ri'".INDUCED S¥¥,ELLING OF KAOLINITIC SOILemploying CuK.,, radiation and using 0.04' steps andle- I Red esrlh + ¥ ater I" W terI"I Retl carih + WaSer lrN nOHcounting for at least 0.4 slstep. The mineral compositionh-ir¥¥'*' REtl esrth + IY; er "' 4 N "Iof each sample ¥vas deter'mined using the XRD peakpositions and intensities (JCPDF, 1990).61O l,i*Scanning Electron Microscopy (SEM) StudiesA Cambridge S360 Scanning Electron MicroscopeL -(SEM) interfaced ¥vith a Polaroid camera and an EDAXX-ray analysis system ¥vas employed for characterizingJhand examining the untreated and treated soil and reactionproducts. A very small amount of oven-dried and finelypolvdered sample is mounted on to the tape glued to thefiat surface of SEM stub and sputter coated with goldprior to scanning (White and Dixon, 1995). The terminology used to describe the micrograph has been noted fromSmart and Keith (1981).Free S¥vell IndexThe free swell is the sediment volume per gram of soilin water and is determined using the method of Rao andSridharan (1985).OneDimensional Consolidation TestsIn order to obtain the effect of ingress of alkali solutioninto the soil, experiments were desi**ned to be conductedin different series. Two series of experirnents ¥vere done tobring: out the effect of concentration and duration ofInteraction with alkali solution on the consolidationbehaviour. Soil was statically compacted to the maximumdry density and optimum moisture content of uncontaminated soils as determined from Standard Proctor's test.The maximum dry density and optimum moisture*9iO Con50lid2!ion Prt sure l 0( kPa ,lOO{lFio. l. Volume chanoe be laviour of red earth remoulded with waterand inundated lvith alkali solutionsof 24 hours or until prirnary consolidation ¥vas completed¥¥'as adopted. The samples ¥¥'ere loaded up to a pressure of800 kPa and unloaded to 6.25 kPa.Conventionally, the consolidation test data arerepr'esented by void rati0-10g pressure relationship. Sincethe specific gravity of the materiais might have changed,the data are represented by vertical strainagainst vertical consolidation stress in this paper.Vertical strain 8 is calculated as follo¥vs.Vertical strain 8 = zllllHoWhere: Ah = Ho-HiH0=initial height of the specimen.Hi = height of the specimen at any loadin*' interval.After completion of the above tests, the soil samples wereremoved and oven-dried. The samples ¥vere po¥vdered andthe X-Ray diffraction and SEM studies were conducted.content are 17.8 kN/m3 and 180/0 for red earth; and 13.5kN/m3 maximum dry density and ,-80/0 optimummoisture content for kaolinite. In series 1, the soils ¥vereRESULTS AND DISCUSSIONSmixed ¥vith ¥vater at respective Proctor's optimum watercontent and kept for equilibrium for 2 days. Later soilearth samples compacted ¥vith ¥vater (series 1) and com-samples were statically cornpacted into consolidationpact.ed ¥vith alkali solutions (series 2) has been presentedrin*'s to Proctor's maximurn dry density. The inundatin_"_.fluids ¥vere I N and 4 N sodium hydroxide solutions. Thisseries ¥vas designed to bring out the effect during contami-and the mechanism of the effect of alkali has beendeduced from detailed X-ray diffraction and scanningnation. The sample preparation for ser'ies 2 experimentsis the same as the previous case except that the samplesvere mixed ¥vith the I N or 4 N alkali solutions and keptfor equilibration for one ¥veek before inundating with thesame alkali solutions. This se 'ies ¥vas designed to brin-'out the effect of continued contamination. For compari-son, the consolidation tests on soils compacted andThe volume change behaviour of kaolinite and redelectron microscope studies.Series I-Effect oJ' Alka!i So!utions on Vo!ulne ChangeBehaviour of Samples Colnpacted with WaterFigures I and 2 sho¥v the plot of vertical strain 8 a*'ainstvertical consolidation stress for the compacted red earthsoil and kaolinite ¥vith ¥vater respectively and inundated¥vith ¥vater, I N and 4 N NaOH solutions. Both r'ed earthinundated ¥vith ¥vater were also conducted. Repetition ofthe oedometer tests ¥vith identically prepared specimensgave consistent data.Remoulded samples after' equilibration was staticallyand kaolinite specimen inundated ¥vith I N NaOHcompacted to the Proctor's maximum dry density in a 60mm diameter and 20 mrn high consolidation ring, to aabnormal s¥vell (rebound) during unloading. Thethickness of 14mm. The ring ¥vas then mounted in aunloading in case of red earth soil. It has even crossed itsconsolidation cell and positioned in the loading frame. Atinitial height. Kaolinite specimen inundated ¥vith 4 Na nominal pressure of 6.25 kPa, the sample ¥ 'as inundated with the required fluid. In all the experiments, aNaOH solution also exhibited higher swell duringload increment'atio of one with load increment durationexhibited steeper compression than specimen inundated¥vith ¥vater or 4 N NaOH solution. Ho¥vever', the red soilspecimen inundated ¥vith 4 N NaOH solution exhibitedcompression strain has been completely recovered uponrebound than specimen inundated ¥vith ¥vater and I NNaOH solution but the compression strain has not been j,SIVAPULLAIAH AND i¥,iANJU62compression during loadin." cycle in any pressure rangeunlike the specimens compacted with ¥vater and inundat-,2 loed with I N NaOH solutions. Red earth soil remouldedand inundated ¥vith 4 N NaOH sho¥ved steeper compression during loading as ¥vell as steeper rebound duringunloading as compared to the soil remoulded and inun-l,:!i"11"dated ¥vith water (Fig. 3). It is to be remembered that inthis series, after mixing with contaminant, the sample hasbeen cured for one week before starting the consolidationtest. Durin** the time between mixing and staring the test,silica ¥vould have leached out from kaolinite due to the' -io [K olinitt - 11 ster t I .Isr- 2 *l- KaoTinite - IY,rrI N Ih;sOr hso F,ite-Wster + 4 " ¥.OHIs-[e 1IOtConsolitistion Pressur?(kP2)ooOo{)Fig. 2. Vo]ume cbange behaviour of kaolinite remoulded lvith lvaterand in ndated ,vith a]kaii solutionspresence of 4 N NaOH solutions. And hence, strength ofthe soil would decrease. Thus, more compression hasoccurred in this series compared to soil remoulded withwater and inundated with 4 N NaOH solutions. Whenkaolinite is remoulded and inundated ¥vith 4 N NaOH,compression is same as kaolinite remoulded and inundat-3,led ¥vith water. Ho¥vever, it has also sho¥vn a steeprebound during unloading. The compression strain hasbeen fully recovered during unloading in case of.[kaolinite. The swelling during unloading in case of redearth appears to be less in this series as compared to soil*3remoulded ¥vith ¥vater and inundated with 4 N NaOH>(Fi**. 3). But unlike red earth sample, in case of kaoliniteRed earth + WH,er - Wster* 4-Red esrthJ X. N. Or +A Red esrth*XaOIswelling durin*' unloading appears to be more in thisN.'aOH- 4 ,,. ,,.OH-9lOFig.Conselida tion Prs5surc(kP2}c(icOo3. Volume chanoe behaviour of red earth remou ded and inun*dated lvith a]ka i so]urioTlsseries as compared to kaolinite remoulded ¥vith ¥vater andinundated with 4 N NaOH (Fig. 4). This difference in thebehaviour of red earth and kaolinite could be due to thedifference in cry. stal structure of kaolinite minerals. Inkaolinite the particles are strongly bonded by hydrogenbond than in red earth (the hydro*'en bonding disruptedby presence of non kaolinite particles) and due to hi**heramount of kaolinite, reaction is taking place at slo¥verrate than that of natural red earth soil.,J-1It is reasonable to conclude at this sta*"e that the overallcompressibility (especially s¥velling during unloading) ofsoil/kaolinite is quite different from the untreat.ed redl4*so- '-1Fiso･ Xs(,- i ,, ,,l0 f - I ,,A h:a{, n-4,,:¥ O -{:¥OFOH-16o CQoti s,ion Pr s;ure(kPa)os!ooeFlg 4. Volumccl]ano*ebehaviourofkaoliniteremoulded and inundated lvith alkali solutionsfully recovered during unloading as in the case of redearth soil.earth/kaolinite. To understand this unusual behaviour,the knowledge of the particle-level interactions at themicroscopic level is needed. Thus, to understand thechanges in soil structure and composition of soil due toalkali interactions, X-ray diffraction patterns and Scanning electron microscopic examination of soil particles¥vere obtained on soil samples after consolidation tests.XRD Studies on Red EartlllKao!i,1ite Sa/7lp!es afterCollso!idation TestsTo understand the extent of changes in the soil miner-alogy after consolidated tests, the X-ray diffraction(XRD) patterns ¥vere analy2:ed. Figures 5 and 6 sho¥v theXRD patterns of consolidated samples of red earth andSeries 2-Effect of A !kali Sohrtiolls on Vohlrne Changekaolinite respectively. Untreated samples of red earth andBehaviour of Samples Compacted with A!ka!i Solutionkaolinite sho¥v the peaks mainly due to kaolinite c.layFi**ures 3 and 4 sho¥v the plot of vertical strain 8 a*･ainstminerals. In red earth, kaolinite mineral peaks are of less¥'ertical consolidation stress for red earth and kaolinitespecimen respectively when compacted and inundated¥vith I N and 4 N NaOH solutions in the consolidationcell. Both red earth soil and kaolinite remoulded andinundated ¥vith I N NaOH solutlons exhibited no steepintensity and quartz sho¥vs maximum peak intensity.Change in concentration of alkali used for inundationhas shown significant variations in XRD patterns. In thesamples inundated ¥vith I N NaOH solution during consolidation testing, the intensities of peaks due to kaolinitek:; INDUCED S¥¥,ELLING OF KAOLINITIC SOILr :: Red earth +4N N aoH +4::' ijl - ':;'2:I, !.;z'< ;r!o.: ; QL ' r-- d !*J'vY-'e'I. )' !'y'l*.LJ' ,iNaoHl*.,*.Jt. r:: Red earth +'flQ1i=rYater + 4 N NaoH$rfle;': . < 'vz-i-f-/1J-_.tl_)1/-': -Y,I_irj,-/ *_!" J'-Red earth +1 N NaoHI N NaoHI ;,; '= I!h,' ;*) '- l'r¥'--'Y=" j -'- '! *4J JLlvi_.YY!QRed ear;h +¥Yater + I N' Nao iI' JL_/ JII i ' _ i:J"J__ _ti ;Q Kii;f .h_Jl -._JY,f' . ! J_ ' _J._J ''-tion test: Q=quartz, K=kaolinite, N TASH=sodium altunirwm[ :[< '-II "' Kaolinite + 4N NaoH + 4N NaoH!1' '<'i il 'I':' UJll! " '1""IvlL"I "'e :IT 1 t'jr'vJ¥Jlrjlt !LhfJ '"' :Y v ' I 'r/1'¥-Y"' rvrjh/"I-" t"J:;r l t;1'Y/'YT iL" " L Kaoiinite + ¥¥rater+4N NaOH"I' 1'; i i {:1 '1' l"'!iremoulded ¥vith ¥vater and inundated with I N NaOHremoulded and inundated ¥vith I N NaOH solution didthe literature.Sample rernoulded and inundated with 4 N-alkalikaolinite has been distorted and decomposed in kaolinite.il ; : IlI' !' I'__J V"ItY flL l ";1:Red earth soil remoulded and inundated with I N7.4 A with lesser intensity indicating that the struct.ure oftJ:; :)INa6 4A16 4Si9 60,2.4.6H20 and I .08Na20.Al203. I .68Si02._.l:/! jll"'_1' izI(fLI1 .08Na20 .Al203 . I .68Si02. I .8H20 (NASH) ( JCPDF,1990) in the case of red earth soiL Both the mineralsi;<fL:'? jf' t":':< 1 f ' "tI'r)of composition Na6 ;A16.4Si9.6032.4.6H20 and NaA12(AISi03)lo(OH)2, have been identified in the case ofsolution showed ne¥v peaks correspondin*" to Zeoliterninerals. The peak due to kaolinite mineral, which isnormally been observed at 7.2 A, has been observed atsilicate h,.･tlroxide h _･dratet ttThis is due to participation of kaolinite miner'al inchemical reactions ¥ 'ith alkali in both red earth andkaolinite. The peaks due to sodium alumino silicatesnot match ¥vith the any of the kno¥v patterns of zeolites,and the kaolinite alkali interaction products available inFig. 5. X-ral. diffraction pattern of red earth samples after consolida-fkaolinite minerals have disappeared compietely in case ofred earth, they have broadened in the case of kaolinite.solution. The ne¥v peak appeared in kaolinite specimenrlIcan be noticed that ¥vhile the peaks corresponding toNaOH solution has not showed any si**nificant changesin the X-ray diffraction pattern compared to sampleUntreated red earth'J Iserved in both red earth and kaolinite. At the same time itl .8H.O ar'e zeolitic minerals.o*':rpeaks corresponding to Zeolite rnineral have been ob-kaolinite and sodium aluminum silicate hydrateQY))63: KaolinitelY;"I[rNaoH+ NN 1-"IOHb'vY 'rY"IrvtY_1 _!vi "_v' lY' 'YvYt 'YII: :: IJJ _;;L_ _wl"'-'1-It ¥vas noted in previous section that the peak corresponding to kaolinite mineral is only broadened up inkaolinite remoulded ¥'ith ¥vater and inundated with 4 NNaOH solution. In red earth, the peak corresponding tokaolinite minerals has disappeared completely in both thespecimens remoulded with wat.er or 4 N NaOH solutionbut inundated ¥vith 4 N NaOH solution. Peak due tomineral NaAISi04, first order maximum at 2.47 A Ivithmaximum relative intensity ¥vas observed in the kaoliniteJspecimen remoulded and inundated with 4 N NaOH"_ 'I 'l- _tv fvf 'tsolution, ¥vhich were not observed in kaolinite remouldedj[ .1"! Kao"' :nne ¥¥'ater+1NNaol;4J /¥YIIJIe L i t l-1: :: i'l'YJUliJvYv"J Jr"__"I''tY Ylvl" J _1'Jlj i Untreated Klaolinite4! _¥¥JJr ' ivi[ ' I' 'JJfJ1lt'- JFig. 6. X-ral.' diffraction pattern of kaolinite samples after consolida-tion tcst: Q=quartz, K=kaolinite* NASH=sodium aluminum1 .08Na20 .A1203 . I .68Si02. I . 8H2 O (NASH) has also beenobserved in the kaolinite specimen remoulded and inundated ¥vith 4 N NaOH solution. X-ray diffraction patternof red earth specimen rerrroulded and inundated with 4 NNaOH solutions indicated the formation of (NASH),1.08Na20.A1203.1.68Si02.1.8H20, similar to the XRDpattern of red earth specimen remoulded with ¥vater andinundated vith 4 N alkali solutions.Slight differences in the type of minerais formed in redearth and kaolinite could be due to the differences at thesource material and conditions. Mohnot et al. (1984),Choquette et al. (1991), Chermak (1992), and Qafokusilicate hl_'droxide h･.･dratehave not showith water and inundated with 4 N NaOH solut.ions.Apart from the peak due to NaAISi04, peak due to'n noticeable changes in both red eart.h andet al. (2004) had reported that type of Zeolite is highlykaolinite. The intensity of peak due to quartz hasdependent on sour'ce material, chemistry of t.he poreincr'eased in kaolinite. No other major changes are seen.fluids, temperature and time.In samples inundatedvith 4 N NaOH solution, new 1SI¥rAPULLAIAH AND MANJU64Fig. 7(a). SEM photograph of consolidatcd sampie of uncontaminated red earthFig. 7(d). SEM photograph of consodated sample ofuncontarninat-ed kaoliniteFig. 7(b). SEM photograph of consolidated sample of red eartllremou ded lvith water and inundated lvith 4 N NaOH solutionsFig. 7(c). SEM photograph of consolidated sample of red earthFig. 7(e). SEM photograph of conso]idated sample of kaoliniteremou ded with lvater and inundated lvith l N NaOH solutionsFig. 7(f). SEM photograph of cousolidated sample of kao]initeremoulded and inundated lvith 4 N NaOH solutionsremou ded lvith water and inundated lvith 4 N ' NaOH soluttonsSEM Studies on Rec! Ea/'thlKao!i,7ite Sall?p!es afte/'Conso!idation TestsTo understand the morphological changes, the microstructures of selected samples after consolidation testswere examined by scanning electron microscopy (SEM).XRD studies have sho¥vn the formation of ne¥v minerals¥vhen red earth specimens are remoulded ¥vith ¥vater andinundated ¥vith 4 N NaOH solutions Similar patterns areobserved for kaolinite. Based on this observation, selected red earth soil and kaolinite specimens have been takenfor studying the morpholo_gical changes after' alkaiiinteractions. In case of red earth, samples remouldedwith water or 4 N NaOH solutions and inundated ¥vith4 N NaOH solutions ¥vere taken and compared ¥vithFig.?(g). SEM photograph of consolidated sample ofkaolinitcremoulded and inundated with 4 ¥_ * P 1'aOH solutions&, rINDUC ED S VELLING OF KAOLINITIC SOILuncontaminated red soil sample. Similarly, for kaolinitecase, specimen remoulded ¥vith water and inundated vithl N NaOH and 4 N NaOH solutions and as well as specimen remoulded and inundated lvith 4 N NaOH solutionshas been taken.From Fig. 7(a) it can be observed that the uncontaminated consolidated r'ed earth sample particles appear asuniform compact dense units. Figures 7(b) and 7(c) sho¥vclearly the effect of chemical interaction on the particlesof red earth sample r'emoulded ¥vith ¥vater or 4 Nsolutions and inundated vith 4 N NaOH solutions.paring these micrographs sho¥v that the particlesdegraded or ¥veathered completely and appear as veryparticles ¥vith uniform micropores.NaOHComhavefineFor kaolinite specimen also same changes in themicrostructure have been observed. Fi**ure 7(d) represents the micrograph of uncontaminated kaolinite. It canbe seen that kaolinite particles appear as if the plates arefirmly joined together and it can be obser¥'ed that ho¥v thecrystais of kaolinite tend to rner*'e to_g:ether on consolidation. This has been classified as inter-grown domain struc-ture. And ¥vhen the kaolinite r'emoulded ¥vith water' andinundated lvith I N NaOH solution, it appeared as if thesheets ¥vere getting separated out and a few discretedomain structures were formed, in lvhich the plate-likeparticles ¥vere arranged face to face in distinct domains,with distinct inter-domain voids (Fig. 7(e)).65studies. The formation of Zeolite minerals might be ¥'eryless and they might have been confined ¥vithin the ¥'oids ofred earth particles during the loading cycle. By the timethe loading of the sample is completed in the consolidation test and unloading starts after the lapse of considera-ble time during: ¥vhich more amount of minerals areformed leading to s velling during unloading cycle. Theabove conclusion that zeolites are responsible for s¥vellin_"_of soils is consistent ¥vith the observations made by otherresearchers. Kranz et al. (1989) reported that natur'allyoccurring Zeolite expands vhen hydr'ated and if rock iscomposed of lar_ :ely Zeolites, the entire rock may swellsignificantly as the rock becornes saturated. If such r'ockis constrained, significant stresses may develop as a resultof' hydration. Kruglitskii et al. (1985) had observed theintercrystalline swelling of zeolitic minerals systems dueto the formation of a gelatinous film. Heidug and Wong(1996) observed changes in the crystal dimension ofzeolitized tuffs due to ¥vater absorption that manifestsitself as a swelling of the rock. They reported that theses¥velling effects promoted tensile failure of thevell borevall .It can be termed that qualitatively the effects of alkalion red earth and kaolinite are similar. The relativedifferences can be expressed as follol¥'s based on relati¥'eease ¥vith lvhich the alkali reacts ¥vith different mineralsand consequent changes in the particle arran*･ement.The morphology of kaolinite particies remoulded ¥vithwater or 4 N NaOH solutions and inundated ¥vith 4 NNaOH solutions has changed completely (Figs. 7(D and7(g)) supporting the X-ray diffraction analysis that altera-tion of clay minerals has occurred or' new minerals areformed. Fr'orn the micr'ograph it is clear' that surface ofthe particles are getring cornpletely decomposed andchanging into very fine particles with uniform micro-IMPLICATIONS IN GEO1'ECHNICALENGINEERING PRACTICEIt is very clear from the above discussion that ¥vhenf'oundation soils of kaolinitic type contaminate lvithstrong alkali solutions, unexpected shvelling ¥vill inducepores.the soils leading to upliftment of the foundations.Without the knohvledge of mineralogy, mechanism ofMECHANISM OF VOLUME CHANGE BEHAVIOURsuch abnorrnal behaviour cannot be interpreted satisfactor'y. Therefore, as a general rule in the engineerin_"*.practice, such information on the mineralogy and micro-OF ALKALI CONTAMINATED SOILSFrom the above discussion, mechanism of the volumechange behaviour of alkali-contaminated soils can bededuced. The steep compression which has been noticedstr'ucture of a contaminated soil should al¥vays be pursuedas much as possible. It is necessary for geotechnicalin case of' red earth soil/kaolinite remoulded lvith ¥vateren*"ineers to understand the mechanism of soil pollutantinter'action to avoid problems such as landslides, groundsubsidence, settlement, erosion, pro*'ressive failures,and inundated ¥vith I N NaOH solutions could be moreundergr'ound structural stability, and f'oundation failuresdue to morphological chan*'es occurring durin*' the testby interaction of' soil particles ¥vith inundating fluid,and also to decontaminate the soils as ¥vell as to takeremedial measures.rather than the formation of ne¥v miner'als. It ¥vasbrought out from XRD studies that no new minerals orminerals ar'e for'med in the sarnples during the consolidation tests. The par'ticles became segregated due to interac-tion with I N NaOH solution as indicated by SEM studies. And this could be happening ¥vhen the soil/kaolitespecimen remoulded with ¥vater is inundated with I NNaOH solutions leading to sudden steep cornpression.The abnormal s¥ 'ell during unloading of both redearth/kaolinite r'emoulded ¥vith ¥vater or 4 N NaOH andinundated with 4 N NaOH soiutions is due to formationof' Zeolite minerals as confirmed by X-ray diffractionCONCLUSIONSA steep cornpression and normal swelling has beenobserved for the specimen compacted ¥vith ¥vater andinundated ¥vith I N NaOH solutions. This compression isdue to the segregation or break do¥¥'n of clay minerals dueto alkaii interactions,Due to f'or'rnation of' ne¥v rniner'ais, ¥vhich are havingfine pores and higher water holding capacity, on interaction of soils ¥vith 4 N NaOH solutions, abnormal swellinghas been obser¥'ed. The behaviour has been confirmed by 調66SIVAPULLAIAH AND MANJUX−ray di仔raction patter熱s and SEM photograp熱s． PetroIeu鵬Eng玉neers of AIlv1E，SPE13032・ The difference in the amount of swelling in the samples17）Palomo，A．，Blanco−Varela，M、丁．，Granizo，M．L．，碧uer【as，F、，compacted with water and compacted with alkali solutionbrings out the sensltlvity of the swelling to concentratloavariation and duration Qf interaction．REFERENCES1）Akokelar，D．，Cわaffee，A。and Howe，R．F．（珍97）：Tねe transfor− ma“on of kaoh践to low si三ica X zeo1琵e，Zθ011’θ3，19，359−365．2）Aznar，A．」．and La歪glesla，A．（1985）：Obtenclon de zeo巨tas as Vazquez，T．and Grutzeck，！〉置。V“。（1999）＝C丘1em玉cal stabil玉［y of cememitious materials based on metakao11n，Cαηθη’α’∼ゴCoηααθ Rθ5θακ1∼，29，997−1004．18）Provis，J．L．，Lukey，G．C、and Van Deve飢er，．｝．S。（2005）＝Do geopolymers actua1三y contain nanocrys｛all五ne zeolites？A reexam玉一 natlonofexlstingres縫1ts，Chθ’ηZ5砂oチル勧θ廟Z5，17，3075−3085．19）Qafoku，N．P．，Ainswor由，C C．，Szecsody，J．E and Qafoku，α S、（2004〉：Transporトcontro玉1ed k玉netics 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Zeolite Na−A（LTA）from natural kaolitines， Gθo’θch．Co11∫Gθ01ε凶．E’∼9ヂ9．117勇w5〃’疋’α疋’泥0θvθ10ρη7θ’∼’，Dec． P妙∫’c∫αnゴα∼θ1η’51’ツoゾM”1θノ門αZ5，24，191−199． 12−18，Roorkee，1駐d呈a，1，229−234，9）Heid駄9，W。K。aadWong，SW．（1996）：HydratlonsweUi取gof26）Slvapullalab，P、V、，Allam．M．M．and Sankara，G．（2004）： water−absorbingrocks：AcQns嵌面ve田odel，／η’．ノ」V∼”1L刈11α1． Struc【ura夏distort玉o【1due to蝕eavl簾g of foundation so員玉nduced by A4θr11．G20’ηθご11．，20，403−430． alkali contamination，P”oご， 1η！。Co’U〔 S〃”1！‘々〃剛α1‘7nゴFoμ刀ゴ‘π’01∼ Eoi1”rθ5，Augロst2−4，Sl鷺gapore，601−61L10） H1lierbrand，V》．F．a厭d Lunde1，G．篶．F．（1953）：〆委ρρ11θゴ1110rg‘7η’‘ 擁ノ10ケ豆5，John Wiley and Sons，Inc．，New York。11）Jackson，M．L．（玉958）：So’1Chθ1η’cσ1，4’7αヶ∫’∫，Prentice Hail Iaternatio鷺a1，1鷺c．，Londo鷺，12） ｝CPDF （1990）11》ow‘ノθ1’P卿ηc∫’on F’1θ ！4ψh‘zZ）（∼”c‘71117ゴaYθ5， 1η011gα’7’cρhα5θ5，In1emaεlonal Ce篇ter for d簸raction data，USA．27）Sivapu垂laiaぬ，P，V．andManju（2005）：1くaolin辻e−alkall魚teraα玉on and ef罫eαs on bas至c propert玉es， （フeologicα1 αノ1び （7θ01θ‘11ηκα1 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microscopyof面neralsinsoils，rεYσ550c、E1θα’Poηハ4’c1「05c。／、26， kaolin1tes1n負uence of乞無ermal preact玉vation，．入Phヌ∫iごα1Chθη1〆5一 9−11． ’17，94，760−765．32）W撫lngton，B，LandCardlle，C。M、（1996）：C鼓emls亡r》・oftrlcalcレ夏6）Mohnot，S。M．，Bae，」、H．andFoley，W．L， （1984）．As葛udyof uma1ロmlnatehexahydraterelatingヒotheBayerindustry，加．／、 鐙五neraレalkal呈react玉ons，59’h ！美1ηπ’α1 7セ（71∼1∼’（ンα1 Co17ゾ≧∼ノrθ11cθ α11ゴ Miηθ’η1Procθ∬’η9，48，21−38， 五xhiδ躍011，Housto離，Texas．，16−19September1984，Society of塾
- ログイン
- タイトル
- strain Localization in Solid Cylindrical Clay Specimens Using Digital Image Analysis （DIA） Technique
- 著者
- A. Sachan・D. Penumadu
- 出版
- soils and Foundations
- ページ
- 67〜78
- 発行
- 2007/02/15
- 文書ID
- 20981
- 内容
- SOILS AND FOUND．ATIONSVo1、47，No、1，67−78，Feb．2007Japa職ese Geotecilnical Societ》’STRAIN LOCALIZATION IN SOLID CYLINDRICAL CLAY SPECIMENS uSING DIGITAL IMAGE ANALYSIS（DIA）TEcHMQuEAJANT．A SAcHANi）and工）AYAKAa PENuMADuii） ABSTRACT The str＆in non−uuiformity due毛o the end restraint for a deforming specimen during triaxlahestillg of clay specimenswas minimized in this study uslng lubricatecl end platens．This rese＆rch presents童he eviclence of the occurrence ofstl畠ain loc＆llzation due重o shear banding withi！1the clay specimen by uslng DIA（Digltal Image Allalysis）techRique。ThevariationinstrainlocalizatlonpattemsofsoilspeclmenisalsostudiedforevaluatingtheinHuenceofconnningstress，loading conditions，stress history，dralnage conditions，a更1d so玉1’s microfabric（geometric arraugement of clay plate−Iets）by performing a series of lubricate（1−en（i trlaxial tests on solld cyhndrical speclmens of Kaolin clay。This paperpresentsacomparativestudybasedon由eobservedorientationofsぬearbandformation，andthein宅enslty・fstrainlocalization（by estimating the maxlmum local strain）wi由in重he specimell during its shear deformation process．Key wo雌s：compresslon，digital image a勲alysis，extensiol1，Kaolin clay，10calized deformatlon，lubrlcated ends，strainlocalization，trlaxial（IGC：D6）↓↓↓INTRODUC■10N When＆macroscopically homogeneous material ele−ment is subjected to a suf且cient至y豆ow homogeneous stress1□iapplied to its boundary，homogeneous（1eformationoccurs．As the deformation becomes larger，concentra−↑↑↑tion ofstra玉n at a loca圭zone within the element can occurbecause of the actual non−uniformity of mass density and（al Be∫bre b〔竃din9（b｝Uai50rmdc齢mladon（C｝S［rainlocaliza乳ioε1stl昼nessofthematerial，asshowninFl9．LFailureof！nαny engilleeriug materials is characterized by theformation and prop＆gatioll of zones of localized shearFig．1。Defom離ionof震soiielememunderextern窪1畳oadl“gco皿dl− tio難Sdeformation．The most typical loca王ized deformationIoca豆ization is caused by the imperfections inherent intransmisslon of micro−defects in the locallzation bandIeads to the formation of（iisplaceme飢discontinuity a難dthe soil specimen，the boundary constraints，and non−stress−free crack at macro正evel．Although出e localizationuniform loadlng conditions（Hvorslev，1960；Hl11，i962；Rudnicki and Rice，1975；Rice，19761Rice and Rudnicki，1980；Vardoulakis，1980；Desrues et aL，1985；Toklmatsuand Seed，19871Peters et a1．，19881Bardet，1990；B量gollitheory is considered to be well establishe（i ma重hematical−observed重n geo−materials is豆iuear shear ban（iing、Strainly，very limited experimental data on geo−materials havebeen Ileported（Vardoulakis，19801DesruesαaL，1985；Finno et al．，19971Lade and Wang，200i），mainly be−cause of the豆ack of exper圭lnental faci正ities to moaitor theand Heuecke正， 19911F玉nno et a至．， 1997；Szabo，20001Lade and Wang，20011Yimsiri and Soga，2002）．There−for鑓1ation of重he shear band an（i its orieutation．fore，strain玉ocalization ls considered to be a major Previous investigations reporte（1 由at the non−un玉一factor，whlch colltrols the overa110bserved mechanicalresponse of the specimen，at or near failure。Strai煎localization manifests in the fαm of a shear band，aheight of a specimell due to testing conditions can benauow zone of intense stra重ning（Jir＆sek，2002；Lai et aL，testing system（Rowe＆nd B＆rden，19641Barden and2003；Lade，2003）．Although，shear bandillg is one of theMcDermott，19651Sarsby et al．，1982）．It is now wellpossible defoImation modes，i巨s usually a precursor toknownξhat童he s重rai厳non−uniformity due to the endcatastrophic failure．The呈nitia歪thickuess of the locαliza一restra圭nt and the strain local量zation due to shear banding看ion band depends on the material’s micro−structure．Theare esselltlally dlfferent in mechanism，but confusion st圭11llil）fomltyofstressstateanddeformationmodealong塗heavoided by the use of正ubricated end platens in tri＆xia玉PosIdoctoral Fe“ow，HT Kanpur，正nd重a（ajantas＠iitk、acjl1）．Professor，Dept．of Civll and Environmental Engineering，Universi［y of Tenaessee，Knoxville，TN，USA（dpenumad＠u汰．edu）．丁負emanuscrlptforthispaperwasreceivedforreviewol｝July11，20051apProvedonSeptember25，2006．W煎endiscussionson由lspa葦）ershouldbesubmittedbeforeSeptember1，2007totbeJapaneseGeotechnica！Socieζy，4−38−2， Sengoku，BunkyQ−ku，Tokyo112−0011，Japan．Upon request漁e closing date may be extended one mon也．67 ISAC_HAN AND PENU *1ADU68exists on the role of end-restraint on the initiation andpropa*"ation of shear banding. In the past literature, It¥vas common to assume that triaxial experiments ¥vithlubricated ends on the specimens ¥vith slenderness ratio 1(height/diameter = 1) provide a more stable geometry andmuch greater uniformity of stress and deformationthroughout the test, and allo¥¥* the specimen to retain itscylindrical shape even at lar*'e strains. In the currentwell established, and they ¥vere applied to investigate thethin shear band type localization (Peters et al., 1988;Bardet, 1990; Bigoni and Heueckel, 1991; Sz,abo, 2000;Lade and Wang, 2001 ; Heueckel, 2002). The most typicallocalized deformation observed in geo-materials is linearshear banding.Most of the pr'evious experimental studies on strainiocalization were dependent on the visual obser'vationsresearch, all the experiments ¥vere performed on soilfrom the deformation profile of the specimens.specimenvith slenderness ratio I using a triaxial testin*'During previous investigation using triaxial testin*", thissetup ¥vith lubricated ends; thus non-uniform deforma-phenomenon was not studied in depth due to the lack oftions due to end restraints was assumed negligiblethrou*"hout the study. The focus of this study is toproper techniques for quantifyin*' the local strains ¥vith aevaluate the strain localization ¥vithin specimen of finegrained cohesi¥'e soil (clay) due to the actual non-uniformity of soil mass and stiffness of the material (not dueto the end restraints) at different testing conditions.It is important to note that clay specimens used in thecurrent research ¥vere macroscopically homogeneousmaterial before their shear defor'mation. If the stress andstrain states ¥vere interpreted at the stage of shear bandformation ignoring the fact that the strain localization¥vould have already taken place, the interpreted stressand strain would be inaccurate. Lin and Penumadu(2005) studied the strain locaiization patterns of hollo¥vcylindrical specimens sheared under combined axialtorsional loading conditions using digital ima_ :e analysis(DIA) technique. They developed an experimental setupfor DIA technique, a procedure for digital data processin*', and a pro_gram for data Interpolation; ¥vhich vasused in this study to produce the strain contour plots andstudy the initiation and propagation of strain localization¥vithin the specimen. This DIA technique ¥vas used in thecurrent research for' evaluating the impact of confinin :pressure, Ioadin*" conditions, stress history, drainageconditions, and soil's microfabric on the strain localiz,ation aspect for solid cylindrical specimens of Kaolin clay.PREVIOUS INVESTIGATIOl l?reasonabie degree of accuracy. Recent developments indi*･ital image analysis (DIA), to some extent, allo¥vs forthe capturing and studying local deformations within thespecimen as a function of global deformations. In thisstudy, many triaxial tests were performed to study thevariation in strain localization and pattern of shearbandin*' ¥vithin the clay specimens with respect to thechange in stress history of clay (normally consolidatedand heavily overconsolidated), inicrofabric of clay speci-mens (dispersed and flocculated), drainage conditionsduring shearing (drained and undrained), the type ofdeviatoric loading (compression and extension), and forvarying levels of effective confining stress. Particleassociation in clay suspensions can be described in theform of dispersed and flocculated microfabric. F!occu!ated microfabric refers to the platelets (or particles) thatare oriented in all possible directions; ¥vhereas, dispersedmicrofabric refers to the platelets that are aligned in apreferential direction (Sachan and Penumadu, '-006a).Durin*' the deformation process, a di**ital imageanalysis (DIA) was used to monitor the overall specimenuniformity, potential initiation of localization, and toquantify the specimen dimensions. Digitized data ¥ver'eobtained from digital images to perform the calculationsfor local deformation and strain profile, ¥vhich alsofacilitated the analysis for strain localization. Digitalimagin_2: technique ¥vas used in this research for all triaxialexperiments to study the evolution of shear bands ¥vithThe localization theory is recogniz,ed to be a mathematically ¥vell established concept for many years; ho¥vever,respect to the specimen and loading/boundary condi-only a few experimental studies including Rice andRudnicki (1980), Vardoulakis (1980), Desrues et al.behavior of cohesive soil.tions, which is important for evaluatin*' constitutive(1985), Finno et al. (1997), Lade and Wang (2001), havebeen performed using g:eo-materials. Hvorsle¥' (1960)observed shear bands and/or post failure bulging in aF.XPERIMF,NTAL PROGRAMseries of unconfined compression tests on clay specimens,and reported that the degree of non-uniformity at largestrains ¥vas much larger than theoretically expected non-the 1-D slurry consolidation method, which allo¥ved onlyuniformity due to the influence of frictional end restraint.Hill (1962) gave a general formulation for shear bands inelasto-plastic materiai using the concept of acceleration¥va¥'e in the context of a boundary value problem.Rudnicki and Rice (1975), and Rice (1976) proposedIn this study, solid cylindrical specimens of Kaolin clay(LL = 620/0, PI = 300/0, G==2.63) ¥vere prepared by usin__'vertical drainage at top and bottom of the specimen(Penumadu et al., 1998). Specimens ¥vith fiocculatedmicrofabric ¥vere obtained by mixing po¥vdered Kaolinclay ¥vith de-aired and de-ionized ¥vater at a ¥vater contenttion of shear band, considering a non-associated flo¥vrule. Based on Rice's ¥vork, the general principles ofof 1550/0, and then consolidatin*' the slurry under' Kocondltion at 207 kPa vertical stress in a slurry consolidometer (207 kPa pressure ¥vas applied in one step).The dispersed microfabric specimens ¥ver'e obtained byusin_g: the same procedure and by adding 20/0 dispersantlocalization of deformation into shear str'ain band ¥vere(Calgon) in the clay slurry of 1550/0 ¥vater content. Claycriterion for formation of shear band and critical orienta-si ; 'r,STRAIN LOCALIZATION N C LAY SPEClivIENS0718161412io06 - (a)¥05*C04-Peak (T-1 )peak (T-3)i 03Peak (T-2)02o':r416Axial strain (o/a)0,7 -(c)06o 5 - Peak (T-1 )(b)Peak (T-6)Peak (T-7)/ ,Peak (T :)08*06*04J02ooO O -Peak (T-5)o 4 8alr03-q = ( l'-O3 (d)16p:= ((J1'+(;2 +(J3f)/3Peak (T-3) peak (T-2)2428Peak (T-6)i4Peak (T-7)o 10CL* 08erPeak (T )02106-02-04q = (;1 -a3o i - p' = (ai +(5:2 +a3')13ooi6220Axial strain (olo)18-1,200469o o o.4 o 8 1 o0206p'/po'r/¥ peak (T-5)OO FoO 02 040608Iop'/ po12i416Fig. 2. Experimental data for triaxial tests (as listed in 'Table 1) performed on solid el. Iindrical specimens of Kaolin clay: (a) Norma!ized stressstrain curves for Tests I to 3, (b) F 'ormalized stress-strain curve for 'Tests 4 to 7, (c) Stress pat!]s for Tests I to 3 and (d) Stress paths for 'I'ests 4to 7specimen vith flocculated microfabric ¥ 'as obtainedafter 24 hours of consolidation; ¥vhereas, the dispersedspecimen was obtained after 330 hours of consolidation(Sachan and Penumadu, 2006a). The diameter (D) andhei**ht (H) of all the slurry consolidated specimens(dispersed, flocculated) ¥vas obtained to be 102 mm (H=D= 102 mm; slenderness rati0= 1). Initially these specimens were isotropically consolidated under 207 kPal276kPa/345 kPa of effective confining pressure. After'isotropic consolidation, the specimens ¥vere shearedunder compression and extension loading conditionsusing lubricated end triaxial testing device developed forthis study, and the measured data vere recorded on acomputer using a data acquisition system. The stressstrain relationships and stress paths for Kaolin clay for allthe tests are presented in Fig. '-. The Lubricated end triax-ial testing setup used in this study had a strain controlledloading frame, which ¥vas capable of applying compression/extension loads on soil specimen at desired axialstrain rate under different loading/boundary conditions;thus the global axial strain (8g) was directly obtainedgrease and pressed in such a ¥vay as to minimize theamount of entrapped air. A circular piece of filter paper,with much larger diameter t.han the platen is placed ontop of the latex membrane in a vay that the filter papercompletely covers the porous plastic strip on the sides ofthe platens. If excess pore pressure gener'ation is achievedto be zero during drained testing, drainage conditions ofthat lubricated end triaxial system are considered to be"good" drainage conditions. The other informationrelated to all drained and undrained triaxial testsperforrned in this study are summarized in Table I ; whichincludes axial strain rate for different tests, void ratiobefore shear deformation (eb=), specimen size beforeshear deformation (H *, Db=), Peak shear stress (o'p) andfor the entire height of the specimen. The other informa-failure location (8p) of each test.Penumadu (2006b).Lubricated ends require smooth and polished endplatens containing radial drainage ports at their outer* *(Sachan and Penumadu, 2006b). In order to prepare thelubricated end platens for testing the clay specimens, theend platens are cleaned thoroughly, a thin layer of highvacuum grease is spread uniforznly over each platen, anda circular piece of latex membrane is then laid on to theusing global displacements measured from LVDT datation about this lubricated end triaxial setup and itstesting procedure could be obtained from Sachan andJsurface. Porous plastic strip is extended circumferentiallycovering all radial drainage ports completely for achieving "good" drainage conditions ¥ 'ithin t.he testing systemDIGITAL IMAGE ANALYSIS (DIA)To address the strain localization and its impact on theinterpretation of test results, the deformation and strain SAC_HAN AND PENUh,IADU70(a)cameraSoft LightTriaxial SpecimenSoft LightTriaxiai specimen clampedDigitato the loading frameCamera(b)¥(c)50-¥e:f Z axis46e,xCLo42y = -O 0083x + 8 21 1R2 s OA9931X-CelibrationoruLL 38c:oCQjs 34Fac-¥¥¥torZ-Calibration Factor- Linear (X-Calibration Pactor)- Linear (Z-Calibration Factor)CQO 30400X a xisy s -O 0084x + 8 3523, > ¥¥¥ : =2 = O 9933500550Distanoe trom Cemera to Object, L (mm)Fig. 3. Strain iocalization }rsing digitai imageanalysis: (a) Digitai imaging setup, (b) Prepared Kaolin cla¥. specimen for digital imaging setup and(c) Caiibration factor using fiat plate anai)sisspecimenused for tr'iaxial testing, ¥vhich was confined in aare needed. Ho¥ 'ever, direct measurement of deforma-cast-acrylic cylinder filled ¥vith ¥ 'ater. The dots on thecomponents at various locations of a deformin_tion at various locations along the height of a specimen isa difficult experimental task. In the present study, digitalimage analysis (DIA) ¥vas used to evaluate the strain10calization in the solid cylindrical Kaolin clay specimenssheared by using lubricated end triaxial testing setup, asshown in Fig. 3. Digital imagin_g: technique in this studyuses a latex membrane (thickness 0.3mm) ¥vith dotsmarked in a grid pattern. CJrid points ¥vere spacedspecimen ¥vere tracked usin*' high resolution di**italuna*'es. To obtain the digital images of tr'iaxial specimens, a Digital camera (Kodak DC 290 "') ¥vith approximately. 2.1-million pixel resolution (1792 H: 1200V) wasplaced at 562 mm distance from the outer wall of cell, assho¥vn in Fig. 3(a). The digital camera vas mounted on atwo-axis controller, which allowed for precisely adjustingapproximately 10 mm apart, as sho¥vn in Fig. 3(a). Thecamera position in t¥vo directions. Images were thendownloaded in to a personal computer, and Ima*"e-Pro-latex membrane was placed o¥'er the cylindr'ical specimenPlus 4. I soft¥vare was used to measure the co-ordinates ofk ; FSTRAIN LOCALiZATION IN CLAY SPECI iENS7ithe points (dots made on the latex membrane placed onthe clay specirnen). The accuracy of measurement wastrue position and displacement of tracking dots on theO.'_ mm in vertical direction and 0.3 mm in circurnferen-used a similar technique for measuring volume changes intial direction. A soft light (Lo¥vell Softlite 2"-･ ') ¥vas used totriaxial testing.provide uniform illumination of the triaxial specimen andsignificantly reduced shadows in the digital images. Afterfinding the co-ordinates of the points on the specimen byusing Image-Pro-Plus 4. I software, the co-ordinates wereEVoLUTION OF SHEAR BANDsurface of cylindrical specimens. Macari et ai. (1997) alsothen used to get the shear band information by using acontour plot program made in pr'ogrammin*' Ian*'uageUsing the data from digital images, the strain components of a point on the soil specimen ¥vere caiculatedbased on the formulation developed by Lin ('_003). TheMAPLE (Lin, 2003).contour plots ¥vere developed to illustrate the strain field,Using irnage analysis software (ImagePro Plus**'), thedistance bet¥veen the specimen edges and the image edges¥vhich facilitated the visualization of the potential for the¥¥'er'e measured in terms of pixels. If these distances ¥verespecimen, such as those shown in Fig. 4, the verticalnot equal, then the carner'a ¥vas repositioned using thehor'izontal adjustment. The process ¥vas repeated untilboth distances are equal. The vertical position adjustment was used to bring the entire specimen into the fieldof vie v. The second horizontal adjustment ¥ 'as perpendicular to the image plane. This adjustment ¥vas also usedto ensure that complete specimen was in view and also foraccurate carnera calibration. The camera ¥vas calibratedto determine the true horizontal and vertical positions onthe specimen surface from digital images as a function ofdistance to image plane. A flat plate ¥vith grid pointsspaced exactly lOmrn apart ¥vas used to calibrat.e thecarner'a. This plate ¥vas fixed to the bott.om end platenstrain on the surface of the specimen is displayed and theintensity of color at certain point of the plot representsinside the triaxial cell, and ima*'es ¥vere obtained ¥vhilevarying the distance bet¥veen the carnera and the front ofthe ffat plate using the horizontal controller' of the camerairnages of specimen and corresponding local-strain-occurr'ence of strain localization. In a contour plot of soilthe magnitude of corresponding axial strain. It shouldbe noted that the X-coordinate of a contour plot isessentially the circumferential coordinate, so that thecylindrical surface of t.he specimen can be ¥'isualized in aplanar manner. The contour lines connect the points thatshare the same value of strain. It is more meaningful toread the pattern of a whole contour plot rather thanfocusing on a single point in a contour plot. Figure 4shows the deformation profile of Kaolin clay specimensheared under triaxial compression loading conditionsat the confining pressure of 207 kPa, which includes thedirection, ¥vere calculated for each image based oncontour plots at differ'ent global axial strain ¥'alues.Visual inspection of the images of specimen during sheardeformation can help in identifying non-unifor'mity ofdeformation ¥vithin the specimen but only ¥vhen the nonuniformities ar'e large enough in magnitude. An advancedtechnique such as DIA used in this research is requir'ed tomeasure the variation of local strains more precisely andstudy small magnitude of deformation that could lead tothe development of shear band type forrnations vithinr'epeated observations. The avera*'e calibration factor asthe specimen. As shown in Fig. 4, the images of claya function of' the distance between the camera and thespecimen at 60/0, I Io/o and 140/0 global axial strain did notirnage plane (corresponding to the front of the flat plate)¥vas obtained, as shown in Fig. 3(c).During the triaxial test, the specimen was confined in aexhibit a significant variation in the local deformationpattern by visual inspection throug)h naked eye. Aftercast-acrylic cylinder filied ¥vith ¥vater, as sho¥vn inFig. 3(b). The presence of confining cylinder and wateraround the specimen in a tr'iaxial cell caused multiplerefractions of light rays to occur, which needed to beaccounted in the analysis of digital ima*'es. Light rayscorresponding local strain contour plots indicated theformation of strong localized deforrnation zones at highbend, or r'efract, as they travel through media of differing¥'ere based on an element ¥vith maximum vertical dimension of approximately 10 mm; therefore, the accuracy ofmeasurement was 20/0 for' obtaining local axial strain.The contour plot at 60/0 global axial strain (Fig. 4(a))normal to the image plane. Using image analysissoftlvare, the observed distance bet¥veen any t¥vo pointscan be measured in units of pixels. The camera calibration factor was calculated from the observed distance, inpixels, and the known ¥'alue, in mm. Average calibrationfactors, one for the horizont.al and one for the verticalindices of refraction, ¥vhich can magnify or reduce theobserved size of the tar*'et object being analyzed. In triaxial testing, the refraction of light will cause the specimenprocessing these images using DIA technique, thestrain levels. It is important to note that the accuracy ofmeasuring displacements using DIA system was 0.2 mmin the vertical direction. The calculations of local strainsplied to the data obtained from digital ima*"es (Fig. 3(b))sho¥ved distribution of local vertical strains ¥vithin theaccuracy range, ¥vhich can be used to infer that within thein order to determine true specimen dimensions and *･ridpoint positions. By incorporating Snell's la¥v of r'efrac-constraints of the measurement system, the deformationwas relatively uniform until the global axial straintion, a 2-D cor'r'ection model (Parker, 1987; Lin andreached 60/0. Shear band with practically constant inclination emerged at 1 Io/o global axial strain and becamemore significant as the global axial strain increased. Theto appear enlarged. Therefore, corrections must be ap-Penumadu, '_005) Ivas developed to describe the relationship bet¥veen the observed and actual specimen measurements. This model lvas used in this study to obtain theshear band was observed to be fully developed at 140/0 !,SAC_HAN AND PENUN,1ADU72(a)8 oo'f /" ..* " <;'/ .r ' ..*--'oQ' (･;./e 5:/)ee/'/''// ' ji:__s)e5. ! ,o--OO)Q '1J 0 .//'i)+o0Specimen60/0 '" ;:.giobalaxia] atstrain- -0.0- -O'; -0.1, ' '*o.. ) e?j ]e_O. 1'/' {-O13.0O2J)e Re]atively Unifoml-+ +-O 1Deforrnation.5 oooo s eoContou-2 oo '-O 1o.oe I oo 2 oo s oooo4 ) ocal strainValueslobal axial strainIot for 60/0b3 ;.' . Specimen at llo/o : i$S- -o o7 cu* J o{ii -o'oo )'['j{i j!-ree'v/ol" # -o".i_*' #; '1 _o 1ee'i' "si"oo f;i'o "/;r . r.. ";/ iContOUr;'S'..__i-o 1/fr :f' ,5 ee 4 oo -e:oo' ') ei;r:-o 1-2 oo -1 oe o ooOt for 1 1 o/oiJSO 200 30e4J:) ocai strainiobal axial strainVaiuesSPecimen at 140/0S!. Si9:lobal axial strain*j '-i ti ;z;1(,( s :: ji'/::;:1:;1,:'1i;:/ !jii{Fig. 4Contoilr plots (X ax is: circumferential coordinate in cm, Z axis: vertical coordinate in cm) and the digital images for Test 1: (a) Uniformdeformation (reiatively). (b) Initiation of shear banding and (c) Shear band formation*-10bal axial strain, as sho¥vn by the contours of t¥vo localcausing an averaging effect in deforming local strainzones (Zone A and Zone B) in Fig. 4(c). Zone A shows amuch smaller values of local axial strains (8100/0) incomparison to Zone B (14160/0). The contour lines arevery dense in the Zone B as compared to Zone A, ¥vhichvalues.In Fi*･. 4(c), the Zone C represents a part of anothershear band, ¥vhich is approximately parallel to the shearband in Zone B. For local strain analysis, the imagestaken during shear deformation covered approximatelyimplies a dramatic transition of the axial strain values.Therefore, the z,one of intense straining (such as Z,one B)1 /3 of the perimeter of specimen. At the end of shearing,can be regarded as a shear band ¥vith an approximatelyconstant inclination. It should be noted that the localthe specimens ¥vere extruded from the triaxial cell andthen visually inspected to e¥'aluate the continuity andstrains in the shear bands could be much hi her than ¥vhatis depicted by the contour plots. This is because the shearinclination of shear bands around the specimen. Fi*･ure 5bandsvere much thinner than the distance bet¥veennodes of measurements (approximately 10mm grid)shows images of the specimens extruded after shearin*'under triaxial compression and extension stress paths.These images ¥vere taken from four orthogonal directions 73STRAIN LOCALIZATION IN CLAY SPECI夏MENSZone of measur鷺1easure【11ents‘1 i ir”1’ r一齢 胴儒榊欄 匹 F 匹講・ ・躍咽一 r、＿＿庸’彗 lShla「lan虫1『’1’、 暉 医 睾 匿 胸ノi 臨 1 ノ：Ψ 1 監 み 1 8、し ： 臼孟臼 真臼『『 1 ’L 庫！17』 1器踏；＝尋， ”1 i1 禰 『 尊 一 F（a〕3−DView ．融ddi【iQn註l zonビ（b）FrontVlew（c）TopViewFig．6．InterpreIa重ionofshearbandlnclin滋ion（4り oflocaUzごd defb㎜εゑ【io臓speclmen and global axial st三lain（ε，）applie（10n the speci−men by Ioading frame was more thaa4％．For examplelthe dif董（）rence inεm andε黛for Test l was1％in Fig．4（b）（玉nitiatio芝10fshear ba亘ding；ε9篇11％，εm＝12％）alld4％ Addi雨onal zone oflocalized dビ負）mlation呈n F皇9．4（c）（formation of shear banding；ε皇淀14％，εm灘18％）．Thus，the global axial strain at the stεしge of shearballd formation（εsB）was observed to be14％for Test1。 It shou1（l be noted重hat tbe observed inclination of theshear band in the contour plots（Fig．6）was not the trueinclination of the shear band玉n the3一王）space．Figure6i正1ustrates the conver・sion from the observed inc正ination tot紅e true inclinatlon oξshear balld with the3−D view（Fig。6（a）），front view（Fig、6（b））and top v呈ew（Fig、6（c））．Assumlng a shear band（＆n ellipse containing Points1，ノ，F藍9．5、She且rb謎紅di矧ginKao嚢董nclayspeclmensus員鶏glub罫ica重edend ωaxi段lsetup：（a）Compress眞on曲earlng（Test2）and（b）ExIension s董1earing（Test4）ん，and1）cut tを1rough the cylindrical specimen duli臓g atest，亡he true inc至ination should be the angleψ・（Fig．6（a）），wh呈c勤is the angle bet∼∼・een the vertical direc芝ion（r【1ajorP「圭nciPal s亡ress d重reαion） and the shear band plane．to completely observe the outer surface of specimen（fron毛，rear，rlght，and left views）．As shown in Fig、5，出e圭nc1圭nations of a至l the thin shear band formations in aAngleψ・can be calculated by uslng Eq．（至）： rtaガ1（4破） （1）sheared specimen were observed to be identical，and ltwas true for bot勤compress三〇n and extension tests．Thewhere‘1is the outer di＆meter of the speclmen an（1His thespecimens were also observed to have additiona豆zones ofpo呈nts i，ノ，ん，and l are in the p1＆ne of the shear band，thelocalize（1deformations as c＆n be seell in Fig．5．followingrelatlon曲ipholds： The stress−strainτe豆ationship for triaxia正colnpress圭o煎test on Kaolin clay specimen with Hocculated microfabricexhibited the peak shear stress互ocation at apProximate隻yvert呈ca至dist＆nce bet、veen point ／and ln （or 1）．Since H繍（π4／2減jk）・h （2）where h is the vertica玉（iis重ance be重ween points／andん，11％axial straln（εp），as shown in Fig．2（a）．It is im−and 14jk is the arc 至ength betweell points／ and ん inportant to note that sm＆11amount of localized deforma一F量9．6（c）．The contour plots ill Fig．4shows esse駐tiα1至y the重ions were observed bef』ore 11％ axial strain，an（i theinner dashed rectangle in F玉9．6（b）．Therefore，bot勤h andcleg茎lee of正ocalization increased as the shearing Process。4jk can be rea（I from the contour plots，Equation（1）ca獄colltillued．However，a clear shear b＆nd type foImationbe rewritten as Eq． （3），whic紅 is independent of thewas observecl start圭ng a｛ a global axial strain of 11％．specimen diameter：It cou豆d be reasonable to interpreεthat stra三n localizεしt圭oninitiated at peak shear stress 正ocatioa，＆nd the fεLi豆ure 一1（2鴇lk） （3）planes in the fornl of s圭gni負can重 shear ba亘ds weredeveloped in the post−peak response．Peak shear stress（σ卸）is the nlaximum value of devia重or stress experiellcedby the soil specimen du正’ing its shear（ieformation、TheThe value of true inc豆i！1atlon angle（ψ）fQr dl任erent triaxl。＆1tests perfomed on cylindrical specimens of Iくaolin clayare given in Table1．axia歪stra重n （globa1）at peak shear stress Iocatiou（εP）隻stermed as the“f＆ilure”of specimen in the current study．Stress paths （Figs． 2（c） εmd 2（（i）） showed clearly thefaiiure point ofeach test，which represents the peak shearstress level．玉n the current research，formation of shearbanding was exp正a星ne（i as the stage wheret紅ed隻fferenceinmaxlmum local axiαl strain（εm）experienced by the sollDISCUSSION ON LOCAL STRAIN ANALYSIS Table l suτnmarizes the information related toorientation ofshear band formationwithin the spec圭nlellsdurlngαseries of tri＆xlal tests performed under dlf罫erentloadi駐g／boundary colldit主ons．The contour plots of local 74SAα｛AN AND PENUMADU■ableL E∬ectofv部lousfacIorson1hes粟面nloc段iiza書ionp飢temsand芝heorien纏onofshe段rb蹴dsobservedin重hepa1IemsTeSt No．a）τeStingconditlonsb）Co面nlngstressc） Specimen typed）Ob、andHb、（P、獣私司02mm）e）eb、，Axials覧rainrateTrlaxlal S駐ear testStrain localizat玉on analys玉sPeakshearφ’StreSS，（deg）εSBεrn（％）（％）（％）εP ψ（deg）σ6（kPa）■esI la）Undrained，Compressionb）ρ‘讐σざ漏207KPac） NC，Floccuiated m圭crofabric12731、711．0王4．018．015430．111．514．019．03618629．514、O玉4、820．O3914735．211．013，026．0311062董．812．514．019．03244826，626．026．029．0NA25127，710、911、0夏7．03｝d）必）b、濡99J mm，Hb，筥1005mme）θb，竺1．03（θ1竺1．18），Rate聯0．05％／m撤Test2a） U鳶dra玉ned，Compresslonb）ρ‘竺σ‘漏276kPac）NC，Flocculated mlcrofabrlcd）Z二）b、繍98．7mm，乏ノb5置99．8mme）εb、筥LOO（ei罵1，i8〉，Rate竺0，05％／謡nTes重3a） Undra玉ned，Compress五〇nb）ρ6漏σご讐345kPac）NC，FIQcc温ated microfabyicd）Ob、竺98．3mm，κb598．8mme）θb、漏0．96（貯L18），Rate罵0、05％／翻nTes芝4a） Und】rained，Ex−ensio貰b）ρ許σ評276kPac） NC，Flocculaεed microfabricd）Pb、竺98、8mm，厚b、漏99．7磁me）θb、＝1、00（a瀟1．18），Raτe需0．05％／min■es重5a） Undrained，Compress玉onb）ρ‘需276kPa，σ‘竺28kPac）HOC，Flocculated mlcrofabricd）Pb，竺99．9mm，κbs司OLOmme）θb、司．07（θi繍1．18），Rate瀟o．05％／ml員τesl6a） Drained，Compressio録b）ρき翫σ‘罵276kPac） NC，Fiocculated m玉crofabricd）Pb、漏98．8mm，乏1ド9％mme）θb，竺1．oo（貯1．18），Rate竺o，oo5％／min■est7a） Undra玉ned，Compress1onb）ρ6瓢σざ竺276kPac）NC，Dlspersed mlcrofabrlc33d）Ob，竺100．2mm，κb、漏99．6m鵬e）θb、罵o，69（θ冊o．79），Rate罵o、oo8％／mlndeform＆tionsonthesurfaceofsolidcylindricαIKadinclay specimens were analyzed witむrespect to the variationin fonowing factors：Coafining Pτessure，Externa1歪oad−ing co賑ditions，Stress History，Drainage conditions，andkPa to study the impact of cQ面ning Pressure（）n stτain玉ocalization pattems of Kaolin c正ay．T｝1e effect ofanisotropic loading conditions and specimen7s stresshistory were also studied by perfoτming an mdrainedMicrOfabr隻c．tr三ax量al extension test on NC clay spec玉men atσざ薫276S〃πi11．乙oごα”《σ∫ioll Pθπθ1串175ρプCloッSρθ（フi117（∼175Shθθ1・θ4（OCR二10）atσ6＝28kP段．The contour plots of locaIkPa and compression test on HOC clay specimen‘！nゴθ1・Un4ズαiηθ4Coηごi！ion5stralnmeasuτementsduringtriaxialcompressiontestat The undrained triaxial compression tests were per−σ6＝207kPa weτe discusse（1earlier，as shown in Fig。4．formed on NC clay specimens with釘occulated micτo・fabric at the con封ning pressuyesσざof207，276and345Similar contour p至ots for the other incl量vidual tests areshown呈n the Fig．7to歪0．嚢 75STRA正N LOCAL夏ZAT正ON IN CL、へY SP匠CIMENS（a）（訊）瞭／頓飯ゆσ7 ・鱗心コGぴ・ 心田lqoアゆ ザコロア 鍵罵躯㍑ぞ 。辱呵 蓑一1心1しO喉、轄欄舳欄1ゴ㈱lio．嚇『c倒 『 繍 ヨ ロいく i ・o嘱 RelativelyU蓑i｛bm1節 De50磁ation 一G侭。。。1翫コ2。。。。 ヌzq 4野。ca夏s舳nさOQ −493 心Ga Contour Iotテor6％ lobal axial strain va匡ues Con重our 10ぜor6％（b）津田1喝1q讐2 0二 rマ 03 鵬ca1宙aiqiobal axial st『ain V副ロ￠S（b）Fig．7． Contour ploIs（X鍼is＝circumferentlal coordi簸a重e in cm，Z aXiS＝vertiCaiCOOrdin訊重einCm）and山edigiIalim謎geSfOrleS｛2：（a）Fig，8．Contourplots（λ1段xis：circumfere凱茎謎lcoord蓑疏atei臓cm，Z 瀬s：vert隻caicoordi戯eincm）andthedigit盆賎magesforTest3：（a） U臓iεorm deformation（re塵adve匪y）＆nd（b）S勧ear ba臓d forma“oI1 Un置orm deformatio聡（reia“vely）a毅d（b）Shear b扱nd form滋ionE価ectofCon且ningPressureoccur at thepeak value ofstress−strain curve，as shown in As shown in Figs．4，7and8，the distribution of localFig．2．It is thus reasonable to intelpret the s重ate ofstressaxialstralnonthedeformingtrlaxialspeclmensattheand s書ra重n froln measul−ed ex重erllaHoad and displacemen重t致ree con且ning Pressure values of207，276，and345kPaassuming a uniform state of deform段tion up to an axialwas observed to be uniform￡or global axial straln valuess重raill value of11％for compression stress path and ofup to6％．The shear ban（i emerged at11％of global axial11．5％forextension．Theshearbandformationwasstrain＆nd became more＆nd more sign呈ncant as the strainQbserved to be ful正y developecl at a globalεしxial stra圭n of正evel increase（i． Shear b＆11ding was observed at 14％I4％forcompression，and13％forextension重esting。Aglobal ax圭al stra重n forσ6凱207an（i276kPa（Fig．4（c）andsignific＆n重d呈f罫erence was noticed between the values of7（b）），and at14．8％g至oba玉段xial stra圭nξorσ6；345kPamaximum local axial straln（εm）for compresslon（19％）（Fig．8（b））．For al1亡he three cases，strai且10calizat圭on∼vasobserved to be initiate（1for stress state corresponding toand extension tests（26％），which illdicated tha｛the strainlocahzation was much stronger in the specimen subjectedthe occurrence ofpeak shear stress圭n the stress−strain plotto extens呈on s重1−ess多aξh．The orientatiou of shear band（Fig．2）。The intensity of stra玉n玉ocal量zαtion was observed（ψ）was obse11ve（1to be slgnif崖c＆ntly higher for compres−to be Inuch s案ronger ξor higher con負ning stressession loading（36。）in compariso11to extension ioadlngexhibiting an increase i且the value of maximum local axialstr＆in（18−20％）experieuced by the specimen with theillcreaseincon丘ningpressure（207−345kPa）．Atrendofincreasing ψ a【191e was observed with the increase incon丘nlng pressure，which vαried fromψ孟31to390forthe varlatlon in connnlng pl’essure from207to345kPa，（310），as listed in Table L The Ileason coul（1be attributedto the rotat圭on of major prillcip段l stress by900 fromvertical to horizontal d玉rection．Dur呈ng ex重ens玉on shear−ing，the specimen tends to hεしve a smaUer cross・・sectiona1＆rea（11ecking）＆t由e middle of the clay specimen com−parecl to tke area a芝top and bottom of t鼓e specimenas lis重e（1in Table里．（Fig．9（b））．The necking of specimen induced by theEf罫ect of Extemal Loading Conditions Co飢our plots for compressiou and extension stressinclination of sぬear bands，wh三ch was not a亘issue forextension loading con（1it三〇ns could ＆lso 量nfiuence thecompression loading．paths（Figs．7and9）showedthatlocaldefomationw＆smiformly distr圭bute（1up to6％global axial strain forboth重he loading conditions。Small zones of locaiizeddeformation were observed within重he c1＆y specimen after6％of g三〇bal axial strain and were connected with eachother in the process of further s｝玉ear defQr1nat三〇n。Strainlocalizations圭n the form ofshear ban（1s were observed toEffect of S宅ress History of C1＆y Speci∬1en For the HOC specimen，the g星obal axia豆strain （ε9）coτresponding to uniform distribution of strains （ε9蹴6％），initiationofshearbanding（ε9聯H％），aadfullycleveloped shear band（ε“14％）were the same as t難osefor NC specimen．They also shared重he same vεし1ue of SAC_HAN AND PENUMADU76(a)O(SPecimen at 6010I 0'2/9 Oe --O S.globai axia] straine 'o_e '$. . /ot2i.,.tf OChO he ,-. Oal}I xrl {f o 1; OT1O 2'Ft"T-ollS J Colli o e' Oi _ *-Relatively Uniform0Deformationo hoe -e oo5 OOo e-2 oo 1 ooContourI uo 2.0{) 3 Qo0ocal strains')lobai axial strainiot for 60/0Valuesb'oc'--0'12/ /' '!1/ ;'tl ' ;'1i(L2""'1li; ¥' ¥L___o l2 :;c-'1 ; .rSS?'4; ';''r'/' 1 l:!'* ' t '- : _Shear Band! !/_/ *' :':1T:7''t 'o' _'__li'o¥V-31! /o ' + ; - '^ * B ; S '_ ' *-- ZOne* =*i * -'5i; sQQs'¥!' -f2+t":--fiT:oo-_ i-/ ' ' '/://'!; 'J' ) : ! r -o'o: ! ;{ '_. ¥-^ '!:! + -*-*-'('/i #'t ss'- J: 'ilL :s' t:' !;{ s+j""'J2-'i{'i's' +"t **/'SSS't'';:i ? # :Zone A -/' ' i' 'x#s '- s ; I+ ¥ +--" !'' ' ': ' ""e/ S-s oo;tLiL- ,,S},:'gjobal axral stramIlllJi'; '!1 oooo -s io -2'oe-o ODI oo 2 oo 3 oo, ; . '!i':*"; " * "' ';o li"olh o 12'/ :'t- ,,'i'.ila i_ -J_*..i'_ '.Tl:f+-t!r',:i+ o -'e'__ ;1:j _ i#t#?-SSj x/ f"!Lt s:oQ'*- ' f f';it''!;o'/f *=f;""'fS!!'/:'O ' !;}i i'/S..-o=S "'!SS';j * SPecimen at 13'/o ' '.0'1al I005f;.i Li :oo,*h---4c ocal strainCOntOUr lOt fOr 1 30/0 lObai aXlal StralnV al ilesFig. 9. Contourplots (Xaxis:circumferentia! coordinate in cm,Zaxis: vertical coordinate in cm) and tl]e di*gital images for Test 4: (a) Uniformdeformation (relative!y) and (b) Shear band formationmaximum local strain (e**) ¥vhen the shear band ¥vas fullydeveloped at 8g= 140/0, as sho¥vn in Figs. 7 and 10. The(a)orientatlon of shear banding for NC clay (36') ¥vasobserved to be larger than that for HOC clay (32'), aslisted in Table 1.(b)ei;;;'{:'i:!:i;I ! 'i;!"I:;i't4';l'I{'t'1"_':/ "'i !_!' ;ii/;:;1!1:; !;i:!;::!;;::::i:i/:;j,; ;:.; ' sh ar 3B_.,aond''#+-ts +*; ss -;-^sf:;;;/l ;'1 !';i ;;/f; /'i ;;/'{fi!:t':;i:::!:;*!;s" ' $ i;i-Qe'::';' " i;""s"; "!;*' /;___ l '' _ i-"-*-' '; ' f:zone" 'B'Effect of Drainage ConditionsThe impact of drainage conditions on strain localization behavior of clay specimens was studied by repeatingthe triaxial compression test on NC clay specimen ofKaolin clay with flocculated microfabric at the confiningstress of 276 kPa, and by allo¥1'ing free drainage duringthe shearing stage of repeated test. The contour plots oflocal strain measurements durin*' drained compression" :; /;ss iLL_ ise; s-- '"'*"teIIS *QIe ttzone A''iTel**;1#;1# ss ='. ;%e {'---';;i';;:t; : ;i:" *-### 'ee ''1;'('"i -' ;'!r! "*" ;''i ' ;!;" ' " " +* ;'#t ;/"' ;:5CQs'i '';*' '+s #! *# 1so s ) -2co - I o oc2eo se'contour !otfor 140/0 Iobal ax 21 straln1 !'Loeai stl inVaiuGsPig, lO. Contour plots (.V axis: circumferential coordinate in cm, Zaxis: vertical coordinate in cm) and the digital ima**es for Test 5: (a)Uniform deformation (relatively) and (b) Shear band formationtest are sho¥vn in Fig. 1 1. The distribution of local axialstrain ¥vas observed to be uniform until 60/0 *'10bal axialstrain for undrained shearing and 130/0 for drainedshearing (Fi**s. 7 and 11). As discussed earlier, theundrained triaxial compression showed clear evidence ofshear bands ¥vithin the specimen at 140/0 global axialstrain (8sB). During drained triaxial c.ompression test, thespecimen did not shol;v linear shear band type localiz,eddeformation mode as observed during undrained testin*';however, it ¥vas observed to have many small z,ones ofhi_ :hly localized deformations at 260/0 of global axiaistrain. The reason could be attributed to the differentmodes of instability causing strain localization fors ( r. 1STRAIN LOCALIZATION IN CLAY SPECl IENS(a)77(a)e**e -* 1 07*J ;)" "IptRelatively UniformDeforrnationet -3eeContour2e+*1O O tei 2.Ge 2 !Ot for 4e/oS i!ob8i axiai strains Q5,,Local stra nVaiues(b)(b)# s ' { i" #" __; ' ;# cs s#"( S'xS-##!!--= '#f W '- ' ^ *" i"1' "s#soH;" '';i'/ #s; *+;;; /:!_ i- # *s;t; ;.. -#^ i"^- ' s#'#' ;;;;1;'S ##rTTiS#; i$; -'i-;-;r - '# t' ii'!'ix""x';# ;(' *'S ** ii# };;;:1;.#'-f t ;+ , 1 ;. ii.;j.#s* ;!!sl' i '/"#'SS's ; " i '*'/'# !' !;!S. ;lif ooHio-!"i '; : -"{' :; -L'!ft'* sj sQo*Lri':'; (i$;1ii's :S{ -;r' i{#ii!'.:;! ;" ; ': '"''" ;x '; 's'j; i' ;;;::::;:;'i!;ji';s ;*.";..s;*r 1i;t _ ._ -*s't_'-' '"'Zone ofLocalized' ;)' ;l "; ;:';! :; :i! ";;:-s s!#1 - i yZi'P:!'# ' ! '_' (;is:'i # SS ;'/s s ":' ii s :s "'t;" DeFfonn atron? s;; ' --i; x#:'1- ' "' ii:!'!# i' :s "#x"''S''r;i* -':s# # i-:;' ' ; ...;;:;:::; ;:;: .":tx;'#!--'5 oo 4 oo 'i Qo -2 ee-eQ e e s I Qe:;_";ii !!!"1' '##i" ;';;; :3 eoContour lot for 260/0 Iobal aXiai strainLoc tl strainVatuesFig. 11. Contour plots (X ax'is: circumferential coortlinate in cm, ZFio*. 12. C',ontour piots (X axis: circumferential coordiuate in cm, Zax, is: vertical coordinate in cm) and the digital images for 'rest 7: (a)Uniform deformation (relatively) and (b) Shear band formationaxis: vertica! coordinate in cm) and the digitai images for Test 6: (a)Uniform deformation (re!ativel .') and (b) Shear band formationvarying drainage conditions. During undrained shearing,the instability caused by pore pressure evolution couldplay an important role in the development of shear bandtype formations within the specimen, which apparentlydid not occur under free drainage conditions duringmicrofabr'ic sho ved a clear formation of shear band atpeak shear stress follo¥ved by a sudden failure response.A notable difference in v/ Value ¥vas observed for flocculated (,36') and dispersed (33') microfabric, as listed inTable 1.drained testing.CONCLUSIONSEffect of lvlicrofabriccylindr'ical specimens of fine grained cohesive soils (clay),A series of tr'iaxial tests ¥vere performed on solidIn this research, t¥vo extreme microfabrics of Kaolinand a technique with digital image analysis (DIA) wasclay vere used to study the effect of microfabric on strainlocalization behavior of soil. The r'esults of triaxialused to evaluate the initiation and propagation of strainlocalization ¥vithin the clay specimen due to actual non-compression test on Kaolin clay specimens withunifor'mity of soil mass density and stiffness of theflocculated microfabric at (7g =276 kPa were discussedearlier (Fig. 7). The same test ¥vas repeated using theKaolin clay specimen with dispersed microfabric, and thematerial at dift rent testing conditions. In the currentspecimen's ends; thus non-uniform deformations due tomeasurernents are sho¥vn in Fig. 12. The distribution ofend restraints were assurned to be negligible throughoutlocal strains ¥vas observed to be uniform until 60/0 globalthis study. The impact of confining stress, Ioadingaxial strain for flocculated rnicrofabric and 40/0 fordispersed microfabric. The initiation of shear' bandingvas observed at 9 and llo/o global strain for dispersedand fiocculated microfabric respectively. The shear bandconditions, stress history, drainage conditions, and soil'smicrofabric on the str'ain localization patterns and shearfor dispersed microfabric (8sB= 110/0) in comparison toflocculated microfabric ( sB=140/0), which indicated ahigher possibility of sudden f'ailure in Kaolin clay ¥vithdispersed rnicrofabric. As shown in Fig. 2, the peak shear'stress ¥vas observed at a global axial strain of 11.50/0for' flocculated microfabric and 10.90/0 for dispersedmicrofabric. Unlike the response of fiocculatedmicrofabric specimen, the specimen with dispersed_triaxial tests, ¥vhich significantly reduced the friction atcorresponding contour plots of local axial straintype formation ¥vas observed at much lo¥ver' strain le¥'els!study, Iubricated end platens were used to performband orientation ¥vas discussed ¥vith the follo¥ving keyobservations.1) Ilnpact of Confining Stress: A clear formation ofshear' banding was observed at the same strainlevels for all values of confining stresses. Muchstronger strain localization and a lar*'er value ofthe orientation angle of shear band were observedfor higher value of confining stress.2) Impact oJLoading Conditions: Str'ain localizationvas obser¥'ed to be much stronger for extensionloading conditions in comparison to compression. 璽78SACHAN AND PENUMADU The value of orientation angle of sheaτban（i was5）Finno，R．J．，Harris，W．W．，Mooney，M．A、a真d Vigglanl，G． estimated to be smalleゴor extenslon s員earing than （1997）：Shear bands in p玉ane s！ra茎n compress玉on of loose sand， thecompressionshe段ring．3）111脚α‘ゾS惚∬Hi3ガ01ア：Strainlocalizatlonpaト tern，shear band formation，an（i tむe orientation of Gθα8ch吻置’θ，47（1），149−165．6）H盗，R．（1962）＝Acceleraεion waves in sollds，ノ、Mθぐ1∼．P1∼）乳∫’‘∫o∫ So〃ゴ5，10，1一韮6、フ） Heueckel，Fr．（2002）＝Reactive plast玉c呈ty for clays dur1ng dd筆ydra一 shear ban（i were observed to be the same for both 巖on and rehydratiol｝．Part1：concepts and op“o職s，1n1、，ノ1 tke NC and HOC specimens oεthe Kaolin cl＆y ひ・，18（3），281−312． lndicatlng no signincant impact of stress hlstory。4） 11刀ρααρゾ01ηinθgθCoη4i∼ion5＝The（irained test− ing di（i not show the linear shear band type forma− tions as observed for undraine（i testing．5）乃7ψσαoゾMiσ磁めric：Dispersed microfabric showed the shear ban（i format量ons at豆o、ver stra三n Ievels in comparison to Hocculated microfabric．A notable difference in tbe orientation angle of sheaτ bands was obtained for both the micτofabrics．P1σ5∫ノd一8）き｛vorslev，M．．L（1960）：Physlca！componemsof【heshearstreng由 ofsaturatedclays，！1SCE1∼ε5εα’納Con∫onS／1θ01’S！・1θ’19’170∫ Cohε5’vθ So’Z5， Un呈vers玉ty of Coiorado， Boulder， Colorado， 69一一273．9） Jirasek， ∼〉1， （2002）＝ Object玉ve modeHng of strain loca巨zation， Rθη置’θ丹αncαZ5θびθGθπ’θαソ〃，6（6），匪120−H32（lnE鷺911sh）．10）Lade，勲、v。and wang，Q。（2001）：Analysls ofshea由anding i郎rue triax玉al tests on sand，∫．Eng1召．1》θch．，127（8），762−768．11）Lade，P．V、（2003）：Analysls and predlαion of sぬear banding聞der 3Dconditionsingranularmaterlals，So1なαノ’ゴFα’11伽ioη∫，43（4）， 161−172．12）La1，T．Y．，Borja，P．V．，D蟻vemay，B、G．and Meehan，R．L． （2003）： Capτuring strain local圭zat玉on be｝1玉nd a geosynthet玉c一ACKNOWLEDGEMENTS 【「e玉nforced so温wa冠，／1∼∼．／．∫01’ノ〉置〃11．〆11701．ハ4（∼∼h、Gθo〃∼θ‘h．，27， Financia歪SupPort from National Science Fouadat量on13） L圭n，簸．（2003）：Three工）imens圭onal Static and L》y鷺a漁ic be員av玉or of 425−45…，（NSF）由rough grants CMS−9872618and CMS−029611i Iくao1沁claywithcontrQlledmicrofabric貸singcomblnedaxlaレtor−is gratefully acknowledged．Any ol）inions，盒ndings，and slonaltest1ng，P砂．乃θ5Z5，Un至versltyofTenηessee，Knoxville、14）Lin，H．and｝》enumadu，D．（2005）：Strain Iocal1zat1o鷺i鷺axiaiconclusions or recommendations expressed in this torsiona王tes重ing，ノ、E119’召．Mθch．（accepted）．material are those of authors aad do not necessarily15）Macari，E．，1．，Parker，，∫，K．andCostes，N．C．（1997）lMeasurementτeHect the views of NSF、 ofvolumec益angeslntrlaxlahesτsusingdigltahmaglng［ecぬnlques． Gθo’θch。τθ5∼，／．，GT，10D、」，2（1），103−109．NOTAT10N pi＝In王t玉aL diame【er of spec圭men 五）b、漏Dlameヒer of speci螢en befbre s姦earl賞g（bs） 私竺1醸la出eigbt of speclmen Hb，漏Heig蹟ofspeclme曲ef』oreshearing（bs） θi讐1顧alvoldrat1oofspeclmen θb5Vold ratio before shearlng（bs）of specimen ε評Globalaxlals【rainapPlledon由especimenbyloadingframe εp讐Global axlal strain aヒpeak由ear stress Ieve1 εsB罵Globa盈ax玉al strain at the format1on of S』ear Band1ng（SB） εm竺M＆xlmum“Locai”axial stral簸experlenced by the soli at iIs local zones w叢tねin tぬe specimen dur玉ng its s｝玉ear deformation processOCR＝筥Overconso1韮dation Rat玉oHOC漏Heav員yOverco鷺so！idatedNC編NormallyConsollda【ed ρる筥Pre−coasoUdat玉on pressure σ‘漏Effectlve con丘n1ng pressure before shearing（bs） σ6竺Peak sbear stress w｝1玉ch correspondsし赴e max呈mum vaiue Qf sぬearstressexperlencedby由especlmend面nglEsshear deformation process φ’讐聞奄ctlvefrlctionangleatpeaksめearstressleve1 》罵Angle o∫Sぬear Ba麟d（SB）from vertical axis（Z axis）16）Parker， J． K． （王987）： 三磁age processing and analysis for 磁e me面anicsofgranularmaterlalsexper1me瓢，滋SM万Proc，19’h5ε S♪卿ρ．5卿θ’ηr舵oぴ，Na曲vlile。17）Penumadu，D．，Skandarajal1，A．and C鼓ameau，J、L，（1998）l Strainイate e舞ec【s in pressuremeter test玉ng us玉ng a cubo玉dal shear device：Experimems and Modellng曳Cα几θθo∼θch、ノ．，35，2742．18）Peters，、｝．F。，Lade，P．V．and Bro，A．（1988）：S鼓ear band forma− t玉on on triax玉al and plane s葛ra玉n teStS，！4ゴvα1κθゴr1ゴ￠Y’‘7！7ゑ∬加g oゾ So〃‘717〔ノ1∼o（ンた，AST STP，977，604−627，19）Rlce，，1．（1976）：τむe locallzatlon of plastic deformatio脈，Pノ”oぐ、14’h 11π．Coπ9．T11θoヂα．．4ρρ1．ル1θc17．，207−220．20）Rice，J。R，andRudnlckl，」．W．（1980）：Anoteonsomefeaturesof tねeoryoflocalizationofdeformatlQn，ノ．So〃ゴ5〃「 ∼嬬惚5，Great Brita叢n，16，597−605．21）Rowe，｝》、∼V，and Barden，L、（1964）＝Importance of free e騒ds ln triaxia亘test玉ng，ノ」50〃Mθぐh．ノ『o∼〃∼ゴ．01v．，ASCE，90（S八41），1−27。22）Rudn量ckl，」．anδRiceJ．（1975）：Conditionsfortねelocaliza置lonof deforma覧lon頭pressure−se駄sitivedila瞭nt materials，ノ．Mθごノ7、PhJ・∫， So1’ご5，23，371−394．23）Sachan，A．a鷺d Penumadu，D．（2006a）：E旺ect of繍crofabric oa s熱ear be盤avior Qf Kaoli鷺clay，ノ』Gθo∫θ‘h．Gθo一θm，i∼・o，1．ε，1grg。， ASCE，Tentatively accepted、24）Sachap，A。and Penumadu，D．（2006b）l Dralned sわear streng出 propert三es of Kao1霊n clay us玉ng蓋ubr量cated end tr玉ax圭al setup，C‘7〃． Geo’εoh。／．（1n Revlew）、25）Sarsby，R、W．，Kaltezlαls，N．and Haddad，E．H，（1982）： Compresslon of“Free−ends，，d麟ng語axiahestlng，／．Gθo’θ‘11．RE、FE、RENCES E1’g’g、P’v、，ASCE，108（GT1），83−107，26）Szabo，L．（2000〉＝Commenヒs on三〇ss of stroag elllpticity in1）Barden，L。and klcDermott，R．J．YV，（1965）：The use of free ends e茎astoplastic玉ty，／η’，／、So1’ゴ5σηゴS’ηκη’1ぞ5，37（28），3775−3806・ 1職trlaxlahesting of clays，／．So’1ルfθch．Fα〃1ゴ．0ハ・．，ASCE，27）Tokimaτsu，K．and Seed，B、（1987）：琵valuaτlon of settlements i鷺 91（S罫v16），1−23， sands due tQ ea貰簸qu＆ke s賊akま糞9， ／， Geo‘ec1！。 επgrg．， ASCE，2）Bardet，J．P．（1990）：Acompre蝕ensiverev1ewofstralnlocahzatlo靡 inelastoplast1csolls，Co’ηρε’rε1”nゴGeαθ01rπic5，10，163−188。 113（8），861−878．28） Vardoulak玉s，1。（1980）；S員ear band三nc1呈鷺at玉on and s短ear modulus3）Blgonl，D．andHeueckel，T．（1991）：U鷺lquenessan引ocalizaζlon・L of sand in biaxial teSts，／17’、／．ノV∼〃7∼．湘17α乙v．A4θ’h．0θo’nθ‘h．，4（2）， associat玉ve and non−assoc玉ative elastopiast玉c玉ty，1η∼．／．501’ゴ5αノ1グ 103−119． S瑠c’∼’ヂe5，28（2），197−213．29）Ylmsirl，S．and Soga，K．（2002）：Appllcation of mlαomec盤anlcs4）Desrues，」．，Lan1er，，1。and Stutz，P， （1985）：Loca巨zation of由e modeitostudyan玉soξropyofsoilsatsmallstrains，So1Z∫θηゴ deforma竃lon intests onsand sample，だ’∼gi1∼θθヂ’ngE1η‘’∼♂1’θ Foε∼11ゴαが01∼5，42（5），15−26． Mθch傭c5，21（4〉，909−92L萎塾
- ログイン
- タイトル
- Hydraulic Conductivity of Nonprehydrated Geosynthetic Clay Liners Permeated with Inorganic Solutions and Waste Leachates
- 著者
- Takeshi Katsumi・Hiroyuki Ishimori・Atsushi Ogawa・Kunihiko Yoshikawa・Kazuyoshi Hanamoto・Ryoichi Fukagawa
- 出版
- soils and Foundations
- ページ
- 79〜96
- 発行
- 2007/02/15
- 文書ID
- 20982
- 内容
- SOILS AND POUNDATIONS¥IOl_ 47,Nol,7996, Feb. 2007Japanese Geotechnical SocielyHYDRAULIC CONDUCTIVITY OF NONPREHYDRATED GEOSYNTHETICCLAY LINERS PERMEATED WITH INORGANICSOLUTIONS AND WASTE LEACHATESTAKFSHI KATSU ･lli), HIROvUKI ISHI 10Rlii), ATSUSHI OGA¥vAiii). KU +1HIKO YoSHIKA¥vAi+),KAZUvoSHI HANA¥. IOTO ) and Rvolc 'HI FU AGA¥¥,A+i)ABSTRACTTo investigate systematically the effects of electrolytic solutions on the barrier performance of geosynthetic clayliners (GCLs), a long-term hydraulic conductivity test for 3 years at longest ¥vas conducted on a nonprehydrated GCLpermeated ¥vith inorganic chemical solutions. The hydr'aulic conductivity test for ¥vaste leachates was also conducted.The results of the test sho v that the hydraulic conductivity of GCLS Significantly correlates ¥vith the swelling capacityof bentonite contained in GCLs. GCLS ha¥'e excellent barrier performance of' k < I .O x 108 crn/s when the free s¥vell islarger than 15 mL/2 g-solid re_ :ardless of the type and concentration of the permeant solution. In addition, when theresults of the hydraulic conductivity test ¥vith chemicai inorganic solutions wer'e compared to those ¥vith ¥vasteleachates, the hydraulic conductivity of GCL permeated vith chemical solution ¥vas almost the same ¥vithin the electricconductivity of O-'_5 S/m as that permeated ¥vith ¥vaste leachate having similar electric conductivity. The hydraulicconducti¥'ity of GCLS to be used in landfill bottom liners can be estimated by the hydraulic conduct.i¥'ity valuesobtained from the experiment using chemical solutions having the similar electric conductivity ¥'alues, if the chemicalsolution had the electric conductivity ¥vithin = 25 S/m.Key words: bentonite, chemical compatibility, geosynthetic clay liner, hydraulic conductivity, long-term hydr'aulicconductivity test (IGC: D4)ance of GCLS (e.g. Egloffstein, 1995). Therefore, thebarrier performance and chemical compatibility of' GCLSINTRODUCTlor lTGeosynthetic clay liners (GCLs) are efibctive barrielmaterials alternated or combined ¥vith compacted clayagainst electrolytic solutions must be evaluated so thatmeasures can be taken to prevent toxic contaminantslayers, vhich are mainly used as the component ofpresent bottom liner systems in vaste containmentfrom leaking to the outside of ¥vaste containment facilities.The efibcts of a..* gressive inorganic solutions on thebarrier performance and s¥velling of bentonite have beenfacilities because of their relatively lo¥v cost, easy installa-tion, and excellent barrier performance to ¥vater. GCLSare factory-manufactured clay liners consisting of a thinlayer of sodium or calcium bentonite glued to a geomembrane or encased by geotextiles. The barrier perforrnanceresearched (e.g. Petrov and Rowe, 1997; Ruhl andDaniel, 1997; Shackelford et al., 2000; Jo et al., 2001;Shan and Lai, 2002; Katsumi et al., 2004; Kolstad et al.,2004a). These studies conclude that the hydraulicof GCLS is attributed to the s velling of bentonitecontained in GCLs. Sodium betonite swells more thanconducti¥*ity and s¥velling capacity of bentonite is sensitive to the concent.ration and ionic valence of cation in acaicium bentonite, and sho vs the lo¥v hydraulic conduc-tivity value of k<1.0x 10scm/s to ¥vater (Gleasonfrom waste containrnent facilities obstructs the s¥1'ellingpermeant solution, in particular, an electrolyte firstexposed to bentonite dominantly affects the hydraulicconductivity value in an ultimate state. In addition, apermeant solution having a lower concentration requiresof the bentonite, and deteriorates the barrier perform-a longer testmg duration to stabilize the hydraulicet al., 1997; Egloffstein, 2001; Egloffstein, 2002).However, the exchangeable cation contained in a leachateI:iiiIYY]Associa e Professor, Graduate School of' Global Environmental Studies, Kyoto University, Japan (tkatsumi@*nrbox.kudpc_kyoto-u.ac.jp).Assistant Professor, Department of Civil Engineering, Ritsumeikan University, Japan (ishimori@"se.ritsumei_ac jp).Formerly Gradu:aie Student, ditto- (Curremly Okumura Co. Ltd., Abeno, Osaka 545-8555, Japall).Forrnerly ditto (C urrently NIPPO (, o_ Ltd.. Chuo-ku, 'Tokyo 104-8380, Japan).Formerly ditto (C*urrently ¥Vesco C*o. Ltd., Okayama, Oka.vama 700-0033. Japan).Professor, ditto.The manuscript for ihis paper ¥vas received ft)r re¥'ie¥v o l December i, 2005; approved on July 26, 2006,¥Vritten discussions on this paper should be submitted before September 1, 2007 to the Japanese Geotechnical Society, 4-38-2, Sengoku,Bunkyo-ku, 'Tokyo I 12-001 l. Japan. Upon request the cfosing date may be extended one month,,79_ ?!KATSUMI ET AL,.80conductivity value of the bentonite. A CaC12 solutiongradually the hydraulic conductivity of GCLS from I .O xSWF.Ll.ING AND HYDRAULIC BARRIER OFBENTONITF,10-9cm/s to i.OX 108 cm/s in 1-3 years (ShackelfordDeve!op/77ent of Swe!ling anc! Hydr'au!ic Barl'ierhaving a molar concentration of <0.02 M increasedet al., 2000; Lee and Shackelford, 2005b).In most previous studies, the permeant solution usedfor the hydraulic conductivity test ¥vas composed ofsingle-species of NaCl or CaC12, ¥vhich is mainly contained in real leachate from waste containment facilities.Thus, most previous studies have been confined toe¥'aluations from the aspect of the single-species solution.Kolstad et al. (2004a) investigated the hydraulic conductivity of GCL permeated ¥vith the multi-species sohrtionBentonite is primarily composed of the mineralmontmorillonite, which is a member of the smectite family. (Grim, 1968). Montmorillonite is composed of layerswhere a thin crystal interlayer (¥vhich thickness is approximately 9.8 A in desiccation state) consisting of two silicatetrahedral sheets and one alumina octahedral sheet isaccumulated. A trivalent AI contained in the octahedralsheet is partially replaced ¥vith a divalent Mg or' Fe so thatof LiCl-CaC12, NaC1-MgC12 or LiCl-NaCl-CaCll-this crystal layer has a permanent charge deficiency. Tosupplement this char*'e deficiency, there is a hydratedMgC12. However, there are still so fe¥v reports re*"ardin__'exchangable cation (e.*". Na, K, Ca, Mg) bet¥veen thethe hydraulic conductivity for the multi-species solutionthat the barrier performance of GCL,s against electr'olyticcrystal layers. Montmorillonite has a large specific sur-solutions having a complex component like ¥vaste(60-100 meq/100 g), and a high charge deficiencyleachate cannot be systematized quantitatively. Therefore, the hydraulic conductivity for the multi-species(0.7-1.3/leq/m2). These factors contribute to the hi_ hs¥vellin*' potential and lolv hydraulic conductivity ofbentonite to ¥vater. Bentonite used in GCLS typically hassolution must be further in¥'esti**ated. It is also importantface area (770 ml/**), a high cation exchange capacityto investigate ¥vhether the barrier performance of GCLmontmorillonite contents of 65-900/0 (Shackelford et al. ,exposed by ¥vaste leachate having various chemical2000).The correlation between the hydraulic conductivity andthe swelling capacity of bentonite is generally attributedsubstances can be estimated from the results of previousstudies in ¥vhich permeant solutions easily made ofconductivity test ¥vith a ¥vaste leachate, the test duration¥vas short and only one kind of vaste leachate ¥vas used.to the volume of ¥vater molecules that are bound to theclay surface. These ¥vater molecules are considered theimmobile water phase ¥vhich behaves like the solid phaseobstructing the flo¥v. When the volume of bound lvaterThere have also been very fe¥v repor'ts regarding themolecules increases and the immobile water phasehydraulic conductivity for ¥vaste ieachate. To secure thebecomes thick, the eff ctive pore space comprised ofbar'rier performance of GCLS that ¥vill be applied to a realsite, the hydraulic conductivity of GCL,s for electrolytlcincrease in the bound water' means a decrease in thesolutions (in particular, the multi-species solution orhydraulic conductivity of bentonite (La*'er'¥verff et al.,inorganic substances such as NaCl and CaC12 ¥vere used.Although Ruhl and Daniel (1997) conducted a hydraulicfreely fio¥ving water decreases. At the macro-scale, an¥vaste leachate) must be further' investigated. In addition,1969; Mesri and Olson, 1971). The volume of boundit is necessary to systematize the barrier performancewater has traditionally been described in the electricagainst electrolytic solutions and to discuss the adequacyof the hydraulic conducti¥'ity test lvith a chemical solution such as a NaCl or a CaC12 solution, ¥vhich have beenused in previous studies.diffusion double layer using the Stern-Gouy theory(Lambe, 1958; Mitchell, 1993; Shang et al., 1994).This study investigates systematically the effects ofHowever, Stern-Gouy theory has significant limitationsand does not accur'ately describe the crystal interlayerexpansion, which is called the s¥velling (Norrish, 1954;electrolytic solutions on the barrier performance ofGCLs, and discusses the applicability of the hydraulicSposito and Prost, 1982; Lo¥v, 1987; Sposito, 1989;McBride, 1994).conductivity test ¥vith a chemical solution as the prediction method of barrier performance that ¥vill be exhibitedin a real site. This paper shows the results of the lon*"-The hydraulic barrier of bentonite significantly correlates with the crystal interlayer expansion of montmorillonite by the intercalation of ¥vater molecules. There aret¥vo types in the interlayer expansion of montmorillonite;the osmotic s¥velling and the hydration s ¥'elling (vanterm hydraulic conductivity test on a nonprehydratedGCL. permeated vith t¥vo types of solutions as follows;(1) the chemical solutions that consisted of the singlespecies and multi-species of NaCl, CaC12, or KCl, and (,_)Olphen, 1977; McBride, 1994; Prost et al., 1998). Theosmotic swelling occurs ¥vhen the exchange sites in thethe real leachates sampled from ¥vaste containmentinterlayer contain monovalent cations (Norrish andfacilities in Japan. The hydraulic conducti¥'ity test ¥vithQuirk, 1954; Posner and Quirk, 1964; L,o¥v, 1987; Changthese permeant solutions ¥vas continuously conducted for3 years at longest to achieve the chemical compatibilitypointed by Shackelford et al, (1999 and 2000), and thedifference in the hydraulic conductivity ¥'alues for thechemical solution and the ¥vaste leachate ¥vas in¥'es-et al., 1995; Karaborni et al., 1996). If the exchange sitestigated.are occupied ¥vith monovalent cations, the force wherethe monovalent cations attract the interiayer chargin_'¥vith negative electricity is ¥veak so that ¥vater moleculesare easily intercalated. The space of crystal interlay. ers ofmontmorillonite expands ¥vith ¥vater molecules (>40 A),and the bound water in bentonite is increased ¥vith hig:hL 断萎81HYDR、へUUC CONDUCτIViTY OF GCLSIab置e L Review on hydr且u賎c conduc醸vi重y正es症s of geosy臓糠le吐ic ci無y旺ners（GCLs）ReferenceSolutiOnType of GC「LEglogsエein（2001）GCL（Geo【extile−sandwichedben芝o煎es）｝oetal、（2001）GCL（GeoteXtile−Sand、viched granu三arSpeciai tesτing condit玉ons notedDI wa［er，CaCl・ Prehydra【ion，Na ben［iQni｛e，Ca benエon宜e，Sequence of permea｛io11DI water，Liα，NaCl，KC「1，benlonites）CaCiユ，Mgαユ，Znαユ，CuC12，LaC13，Base，AcidKa乞sumielal、（2004）GCLs（Geotexdle−sand、、PichedgranularDI water，Naα，CaCl2， Preねydratio隷orpowderedbentoni仁es），NaC1−CaClユN・lodi員ed beatoni｛eKatsumi and罫ukagawa（2005）GC「Ls（Geotext穀e飾sa11dwicねed granularorpowderedbemonltes）Dlw飢er，Naq，CaC12，Con恥lngs【ressNaC韮一CaC1、，1〉茎S∼VIeacha芝eKolsτad et ai．（2004a）GC取Geote畑e−sandwicねedgra“ularKols乳ad et ai、（2004b）GCL（GeOteXtile−sandwiclledgranularben［onites）ben【onites），Lee and Sねackdford（2005a）Dense−preねydra｛ed GCLGCL（Geotextile−sandwi面edgranularL玉C1−CaCl2，NaCl−MgCI3Lic韮一NaC1−CaC12一｝〉lgC1ユDlwater，Naq，CaC1二，Base，AcidCaC12Prehydra芝ionben【oni【es）Lee aほd Sllackelford（2005b）GCL（Geotext員e−sand、、・ic急ed granularDI water，CaCl二be飢onites）Peζrov and Rowe（1997）GCL（Geαextile−sandwichedgranularbenton玉tes）RuhlandDaniel（1997）GCL（Geαextiie−sandwichedgranularbenton玉tes）NaC1，Synthetic｝〉歪S、VCon自nings｛ress，Prehydraこionleac猶a［eTap water，Base，Ac1d，Syn段1e｛ic Ieac皇1ates，r〉IS、V leacねateSねackelfordαa1、（2000）GCL（Geoζextiie−sand、、「iched granularCaCi二be煎o蝋es）S｝｝an and￡ai（2002）GCL（Geo董ex工韮e−sandw玉ched granularbe【Ron王tes）Vaskoetal．（2001）GCL（Geotex工玉le−sandw1ched granularDI water，τap water，、へc1d，Sea water，脚IS、V leacねateC「aClユ Prehydrationbentonites）萎densまty． The osmot圭c swe豆lil19 Prov玉des the exceHentEαα013！4熊αing ∼hθ的41’躍ぜ1ic Co11ゴ己κ1iviぴoゾ’8εn一hydraulic barrier to bentonite．On t勤e other hand，the∼01zirθhydration swellillg appears in bentonite contain圭119multivε迄1ent cat圭ons（Norrish and Quirk，19541Posner T＆ble王shows the review of previous studies on the＆nd Quirk，1964；Kje1玉ander et al。，1988；Prost e毛a1．，1998）．The interca圭ation of water molecu正es is limited andthe space of crystal interlayers is narrow， becausehydraulic conductivity tests of GCLs．Fundamen芯alfactors a廷ecting the hydraulic con（iuct圭vity of GCLs are（1）quality of bentouite，（2）effective pressure coRfiningmultiv＆1ent cat圭ons attract the crystal interlayer moreGCLs，an（1（3）conceutration and type of chemical sub−stances dissolved ln permeant solutiol1．The（luallty ofstrongly than monovalent ca婁ions．Therefore，the hydra−belltonite used in GCLs is affected by several factorsl tぬetion swelHng cannot suf丑cie【1dy provi（ie t｝1e swe三ling aτ1（imlneralogical composition（in particular，montmoriレhydraulic barrier窒o bentonlte．Eglof￡stein（玉995）meas− lonite content），the surface al’ea aad part宝c豆e grain s量ze，ured由e free swell of sodium bentonite（the exc紅angethe surface charge （ie且ciency， the catiou exchangesites are occupied with sodium ions）and calcium ben−capaclty，and芝he composition＆nd amount of exchangea−tonite（the exchange sites are occupie（i wi亡h calcium ions），ble cations（圭n par重icular，sod量um cat量on）．The quali重y ofand showed over30mL／2g−solid for sodlum bentonltebentonlte ls substantially dependen重on the mlning siteandシ7mL／2g−solid for calcium bentollite，respectlvely．and the crushing Process of the bentonite．In general，the The sweUillg capacity and hydraulic b＆rrier of ben−tonite signi長candy correlates the space of the crys重a1super玉or barrier perforlnance of GCLs量s provided by the玉nterlayeτs expan（led by the illtercalation of watermontmori110nite content，smaller surface area andmolecules．When the exchange sites are occupied wlthparticle grain size， higher surface charge deaciency，higher catlon exchange capacity，and lager amount ofexchεしngeable sodium cation． Lee and Shackelforc至cεし重ions having重he stronger attraction force，the sp段ceof the crystal interlayers is narro、∼・er because waterbentonite hav圭ng the hig紅er qua正ity such as 五ig紅ermolecules are not lntercalated e＆sily。Therefore，if （2005b） 圭nvestigated t紅e impact of benton嚢e quality，bento虚e is permeated with electro墨ytic solu重ion havlngstτonger concentration， the beutonite cannot swe1正su伍cien￡1y and cannot form the superior封ydraulicbarrier．which di任ered in重he montmorilionite contents（77and86％in principal mlner31s of the be飢onite），on the hydrau−hc conductiv圭ty of GCLs，and showed｛hat t難e h量gh ben−tonite quality decreased the 勤ydraulic concluctiv呈ty foII *f'"KATSUh,{I ET ALs2water but adversely increased the hydraulic conductivityfor electrolytic solutions. Katsumi and Fukaga¥va (2005)Table 2. Properties of bentonite in GCL usedcompared the granular bentonite GCLS ¥vith thepo vdered bentonite GCL,s in the hydraulic conductivity,and sho¥ved that the significant difference appeared in thehydraulic conductivity of GCL,s permeated ¥vith stron_gelectrolytic solution. The po¥vder'ed bentonite GCL,s ¥vasmore chemically compatible than the _9:ranular bentoniteGCLs.Second factor, effective pressure confining GCL.s,si**nificantly affects the hydraulic conductivity of CJCL.S.GCLS that ¥vill be applied in bottom liners at ¥vastecontainment facilities are confined by the load of the¥vastes buried. The confined pressure consolidates thebentonite so that the hydraulic conductivity of GCL,s isPFopertyUnitPowderedStandard bentoni ein CJCLSoil particle densityNa ural vater coutentPlastic lintLiquid limit[g/cm;] JIS A 120_?[q/.] JIS A 1203['･ ] JIS A 1205[9/.] JIS A 1205[mL/2 -solid] ASTlvl D5890Methylene blue consumption [mmol/lOOg] JBAS 107 91JIS ,i 8853C_hemical compositionSiO.S¥vell index) ,839lO.O51.0619.533.0l 04.0[','･]59.65Al.O_ s[ /.]l 8 .297_15O.41Fe. Os['/ ]TiO.[?･/.]CaO['/.])_.02[?!.]3.140.462.600.13'lgOdecreased. Studds et al. (1996) investi_g:ated the effects ofK.O[9/.]the confined pressure on the void ratio of sodium bentonite permeated with electrolytic solutions that areN a. O[e/.]P.O,['･/.]*lvlnO[ '.]O Ollgnilion loss[ ･6.15composed of different ionic valence. In addition, Katsumiand Fukagavva (2005) conducted the hydraulic conductiv-ity tests on the po¥vdered bentonite GCLS confined atO1'_56 kPa. Their researches sho¥ved that multivalentcations mor'e significantly decreased the void ratio ofbentonite or the hydraulic conductivlty of GCLS by theconifined pressure than monovalent cations.Lastly, the concentration and type of permeant solution are also an important factor affecting the hydraulicconductivity of clay liners including CJCLs. Strong acidsand bases decr'ease the s¥velling capacity of bentonite, andincrease the hydraulic conductivity. of CjCL,s (.Io et al.,2001). Strong acids promote the dissolving of carbonates,iron oxides, and alumlna octahedral sheets of clayJar'e further decr'eased. The pre¥'ious researches sho¥vedthat the hydraulic conductivity of GCL,s became higherfor the electrolytic solution ha¥'in_g: the stron*'er concen-tration. The multivalent cation increased the hydraulicconductivity more significantly than the monovalentcation according to the comparison that ¥vas scaled by themolar concentration of the electr'olytic solution (Lutz, andKemper, 1958; McNeal et al., 1966; Alther et al., 1985;CJleason et al., 1997; Petrov and Ro¥ve, 1997; Ruhl andDaniel, 1997; Shackelford et al., 2000; Jo et al., 2001;minerals. Strong bases promote the dissolving of silicaShan and L,ai, ,_002; Katsumi, et al. 2004; Kolstad et al.,tetrahedral sheets of clay minerals. These effects increase2004a). However, most previous studies ha¥'e been con-the hydraulic conductivity, but reprecipitation of thedissolved compounds might clog the pore of bentoniteand decrease the hydraulic conductivity of clay liners(Mitchell and Madsen, 1987). Nonpolar fluids or polarfined to evaluations from the aspect of the sin_gle-speciesfluids having: Io¥v dielectric constants such as alcohols aresolution of NaCl or CaCl , and little studies were reported on the multi-species solution (Kolstad et al.,2004a; Katsumi and Fukaga¥va, 2005). It is necessary toevaluate the hydraulic conductivity of GCLS permeatedalso a factor to increase the hydraulic conducti¥'ity of clayliners (Shackelford et al., 2000). Ho¥ve¥'er, no significant¥vith the multi-species solution or' theincrease in the hydraulic conductivity occurs ¥vhen theconcentration of or*'anic chemical compounds is lo¥verpatibility.than 500/0, because the dilution ¥vith ¥vater increases thedielectric constant (Mesri and Olson, 1971 ; Bowders andDaniel, 1987; Fernandez and Quigley, 1988; Shackelford,1994). In addition, an increase in the hydraulic conductivity by the permeation of electrolytic solutions is of*'reat concern to use CjCLs in the sea areas or ¥vastecontainment facilities. When the electrolytic solutioncontaining exchangeable cations permeates into GCLs,the space of cry. stal interlayers of clay minerals (in par-ticular, montmorillonite) is narrolved by the attractionforce of the cations, and the s¥velling volume and thebarrier performance of bentonite are decreased. In thecases of the electrolytic solution having the multi¥'alentexchangeable cations, moreover, the multivalent cationsreplace the monovalent cations occupied in the exchangesites of montmorillonite so that the barrier performancel¥'aste leachate inorder to systematize quantitatively the chemical com-EXPERIMENTAL MF,THODSMateria!s UsedCJCL (Bentofix NPS 4900-1) ¥vas used in evaluatingbarrier performance a*"ainst chemical attack. This is atypical GCL ¥vhere the po vdered sodium bentonite isencapsulated bet¥veen a poly. propylene ¥voven geotextileand a polypropylene non¥vo¥'en _9:eot.extile by needlepunching fibers. The mass per unit area of GCL. Ivasapproximately 4.73 kg/m2, and the initial thickness ¥vas6.0-7.0 mm. The basic properties of these materials aresummariz,ed in Table 2. The evaluations of these properties were based on Japanese Industrial Standards exceptfor the methylene blue consumption and the swell index.s HY[)RAULIC CONDUCT ¥,ITY OF GCLSNa1'nfluent1 o*ve1 02K+8VAcr ylicS042-10'c ylinder' Iaoaeotextile16.1and1 0-2filter paperMembranec a 2+N03-Unit : mMEftluCr>H*-WasteWasteW8steW8steleachate A (pH = 6 50, EC = O 93 Slrn)leachaie H (pH = 6 9 , EC = O 24 S!rn)leachate S (pH = 1 1 8, EC = 4f- S/m)leachate K (pH = 7 7S, EC = 29 3 SlrT1)Flg. 1. Chemical component of lvastc leachatesPennean t So!utiol7sThere ¥vere two types of permeant solutions used; (1)the inorganic chemical solutions and (2) the ¥¥'asteleachates.The chemical solut.ions consisted of the single-speciesor multi-species of the inorganic chemical substances;NaCl, CaCll, and KCl. The ionic strength, I, and thelvall permeameters: GCL specimen was 6 cm in the diameter, andapprox'imately 0.7 cm in the thickuesssoil material used in this test was the po¥vdered bentoniteobt.ained fr'om GCL. T vo grams of the dry po¥vderedbentonite ¥vas dusted into a permeant solution in a 100mL graduated cylinder filled ¥vit.h 90 mL solution. Afterthese '_ g of bentonite ¥vere placed into the graduatedcylinder, this cylinder ¥vas filled up to 100 mL. The graduated cylinder ¥vas carefully covered ¥vithout disturbance,The sample stood for 24 hours before taking a reading.ratio of monovalent to divalent, RMD, were used asLiquid Lin7it TestThe soil mater'ial used in the liquid limit test ¥vas theindicators of the chernical solution. The ionic strength I ispowdered bentonite obtained from GCL. After thecalculated from I=0.5 ciz , where cj and zi are thebentonite lvas soaked ¥vith a permeant solution for I day,concentration and the valence of the i-th ion, respectively. The ionic strength was calculated using only thecations contained in the chemical solution because theswelling and barrier performance (in particular, thede¥'elopment of the electric diffusion double layer) ofthe liquid limit test ¥vas conducted according to JIS Al'_05. The bentonite soaked ¥vith a solution was coveredby lapping with a polyethylene sheet so that the moisturein the sample could not evaporate during the test.bentonite are significantly dependent on the exchangeableHyc!rau!ic Colrductivity Testcation. The other pararneter', ratio of monovalent toThe po¥vdered bentonite GCL was used for thedivalent RMD, is calculated from RMD=c 1/(2cD)05hydraulic conductivity test. The hydraulic conductivity¥¥'here c l and CD are the concentration of monovalent andtest ¥vas conducted according to ASTM D 5084 "Standard Test Methods f'or Measurement of Hydraulic Con-divalent cations. The chemical solutions used in thisstudy ¥vere prepar'ed by parametrically changing theselFig. 2. Apparatus for the h,draulic conductivit)･ test using fiexible-ductivity of Saturated Porous Materials Using a Flexibletwo par'arneters.Wall Permeameter"'. The test ¥vas performed by usingThe ¥vaste leachates used in this study ¥vere sampledfrom 4 vaste containment facilities (A, H, S, and K) inJapan. The chemical component in each ¥vaste leachate isflexible-¥vall permeameters ¥vith a cell pressure of 20-30kPa and an average hydraulic *'radient of 90 in a constantsho¥vn in Fig. 1. This component showed the chemicaltus for the test is sho¥vn in Fig. 2.substances that ¥vere detectable with Sequential PlasmaSpectrometer (ICPS-8000; Shirnadzu Co., Ltd.) and lonspecimen for the t.est, GC L was cut to a diarneter of 6 cm.Chrorrrato*'raphy (PIA-1000; Shimadzu C*o., Ltd.).The GCL used ¥ 'as approximately 7 mrn in thickness,Many other chemical substances ¥vould be contained ineach waste leachate besides the substances sho¥vn in thisfi**ure. The lvaste leachate S had a high pH value, and the¥vaste leachate K had a high electric conductivity.0.87 g/cm3 in bulk dry density, and 100/0 in vater content. Next, the specimen ¥¥'as sandrviched ¥vith the filterpapers and the woven geotextiles, and ¥vas placed in theapparatus. The side of this specimen ¥vas restrained ¥vitha rubber mernbr'ane. This membrane received a hydraulicFree Swe!1 TestA free s¥vell test ¥¥'as performed according to ASTM Dpressure of 2030kPa by filling an outside cell ¥vithwater, so that the solution could permeate through the5890 "Standard Test Method fol S¥ ell Index of Cla)Mineral Component of Geosynthetic Clay Liners". Thespecimen without a leaka*'e on the side of the specimen.For the specimen permeated vit.h chemical solutions, thetemperature room contr'olled at 20 degrees. The apparaThe procedure ¥vas as follo ¥'s. In order to make the !EKATSUMI ET AL.84solutions ¥vere directly permeated from the influent point¥vithout prehydration ¥vith the deionized water. The testplots sho¥¥' the free s¥vell for the multi-species solution.As the *"lobal trend, the free slvell of the bentonite ¥vas¥vas continuously performed for 3 years at longest inorder to investi**ate the long-term change in hydrauiicconductivity and to achieve the chemical compatibility.smaller for' the solution ha¥'ing the str'onger ionicThe flolv volumes, the thickness and the hydraulicconductivity of the specimen ¥vere measured over thetesting: duration^strength. The free s¥vell of the bentonite becameapproximately 7 mL/,- g-solid when the ionic strength ofthe chemical solution exceeded 0.5 M. For the effects ofthe difference in the type of cation, the solution containing KCI affected a gr'eater decrease of the free s¥vell forthe same ionic strength levels than any other solutioncontaining NaCl or CaC12. The free s¥vell for the singlespecies solution of KCI ¥vas appr'oximately a half of thatfor the single-species solution of NaCl. Figure 4 sho vs aResultsFree S}ve!lFigure 3 sho¥¥'s the results of the free swell test lvith thefree swell of the bentonite for the various permeantchemical solutions. This figure indicates the rclationbet veen the free s¥vell of the bentonite and the ionicsolutions of I=0.1 M. This figure sholvs that the electrolytic solution obstr'ucts the s¥velling of the bentonite.strength of the chemical solutions. "Na(X) K(Y)"Also, the single-species solution of KCI obstructs moreseriously the s¥velling of the bentonite than the singlespecies solution of NaCl. Therefore, the effect of thesho¥vn in this figure means the mixin*' of volumetric ratioNaCl solution and KC_1 solution. For example, "Na(2) :K(8)" indicates that NaC1 solution and KCI solution ¥veremixed under the volumetric ratio NaC1 : KCI = 2 : 8. Theopen plots sho¥v the free s¥vell for the deionized water andelectrolytic solutions on the free swell is different even¥vhen the valence and ionic stren th is the same in eachsolution.the single-species solution, and in contrast, the closedO GCL wlth D1 w ter35C] GCLwith N CA GCLwith CaCl,GCLwith I<Cls5r 30o:40O GCLwith NaC CaC12 (RMD = O 20 M=f2)") 25JNext, Fig. 5 sho vs the results of the free s¥vell test ¥viththe waste leachates. Figure 5(a) indicates the free swellvalues for the ¥vaste leachates A, H, S, and K . The ¥vastef8< !::jfii;,/i l1 7I }<(2)::i::;/lA GC with NaC CaC!2 ( MD=a50 M'! ); i; -l._))1' '; fJ(K{4:s;20v GCLwith NaC CaC1hJ ro) K(:))(RMD = I aO M1! )v' 30c GCLwith NaC KC:N {4) K{s)cnv,Q,20O:/ ;/"11';,c¥ti a{P? K{8)Hei8ht of B r - Fre8 s Y8il [m /2g- ;eilidjV !ve on sh top o Bar - Eleeirie e<)rxivetivity [S!mjo 02''///'// ; ;';;o 5,* <// ;'t Se)h< <(5) : i((S)'///= :;,J,90e, ID;LLOoe0408oC5l.: _':110 107/ .:/i//;( '';'1u''//p;;i;'/t(;//.;//'ii,;'',,.t;.;. ;r*o(:, )(5c) 5t*5o jc:,O(J',sZQ(tErQZO( :Z r:Fig. 4. Effect of the electrolytes on the free slvell of polvdered ben*tonite in GCL under I=0.1 M403530:::a25o)c¥Ici20E1535302520IsOQ,Q;e't:11 2;://:;,1No J;*Yoo-solution were mix.-ed under the volumetric ratio r l aCl:KC = 2:8JE14 oli s115- - - a)( -XC5 ,C5L"OX ( r)X c'i･t X o (-O :e- ZZ-O-t)-V( ) 11 V n C ) El ZZZ ::::Z2:(5example, "Na(2):K(8)'* indicates tl]at Na:CI solution and KClo)' '*o : oFrg 3. Relation betlveen tl]e free slveil and ti]e ionic strength forchemical solution: "N 'a(X):K(Y)" sholvn in this figure means tllemix. ing volumetric ratio of r ;*aCl solution and KCI solution: For;; ;+ 21614 i(1 :,lonic streng h forc tion [M]a{6 4/'1///;Oe't5soo5 xl!)**(!)Qo<o {!)(1)(!)Q) e)(ocD: Ie,(1':::g!r'( 1eiv It il v ll [1 V i[ [1 v ll ll1)coJ J :C LLI:o J 10l :2.LU1:,::c: c::s, Q,:F 1Q) Q,:, l:,e,q,:,:), 1:; I I)1Q;Lf):,C(1)t (IC;lOCOC¥COXaLSJ(a) Waste leachatesA H S and Kr ig. 5.(b) Waste leachate K and its diluted solutionsrree s,veil of powdered bentonite in GCL for lvasteeachate' rHYDRAULIC CONDUCTI¥,1'TY OF GCLS7ao700O GCL with D water600600C:] GCLwith NaClA GCLwith CaCi.500::: "oO GC with NaCl-CaC12 (RMD= O 20 M1,2)A GCL with NaCI-CaC12 (RMD= O 50 Mlt2)V GCL with NaC[-CaC12 (RMD = oa M1,2)E_ 400E'1:,:sJ500400300:300crJ2001 oo852001 aoo a2o040885< :::ionicstrength forcation [M]ESS OC l a' o)cD(c;C:; : :oCQ :::Oc V{t :iFig. 6. Relation between the liquid l mrt and the ionic strength forchemical solutionJ ' uJ J(1'Fig. 7.5(D* (:) tQ)(QJ:V(Qe,;: ;!:J IOQ,ExC LlcQ:o(o(1)J5Lf)coC;h:Cil ll:OCLLL!Liquid limit of polvdered bentonite in GCL for was e leachateleachates with and vithout filtration ¥vere used. Thefiltration ¥vas conducted by using 6 pm mesh filter paper.The free s¥vell of the bentonite was the same regardless ofthe filtration of the ¥vaste leachate, and vas significantlymaterial can be investigated approximately by evaluatingthe liquid limit, vhich indicates ho v much ¥vater can bedependent on the electric conductivity of the ¥¥'asteleachate. The free s¥vell shows the lower value for thetest with the chemical solutions. This figure indicates therelation bet¥veen the liquid limit of the bentonite and theionic strength of the chemical solutions. The liquid limit¥vaste leachate having the higher electric conductivity.Figur'e 5(b) indicates the free slvell values for wasteleachate K and its diluted solutions. The open bar indicates the free swell that ¥vas measured immediately aft.ersampling, and in contrast, the hatched bar indicates t.hefree swell that was measured after an interval of I year{I{jthe ¥vaste leachates. The filtration of the vaste leachatehardly affected the liquid limit value of the bentonite, andthe liquid litnit lvas decreased for waste leachate havin*'high electric conductivity.to the pore volumes of flo¥v, PVF. Here, the poreis the immobile water layer formed by attracting watermolecules to the surface of a montmorillonite mineralwith an electrostatic gravitation. The thickness of thisvolumes of flo¥v, PVF, is the dimensionless parametercomes in contact ¥vith a montmorillonite mineral, theimmobile water layer becomes thick by attractin*" thewater molecules to the montmorillonite mineral, then thebentonite swells. Ho 'ever, when water including electro-iI,lytes such as NaCl or CaC12 comes in contact'ith a mont-morillonite mineral, the immobile ¥vater layer becomesthin because the electrolytes are attracted to the montrnorillonite mineral together. Therefore, the swellingcapacity of bentonite deteriorates for the electrolytic{j,solution.{(1) the hydraulic conductivity, k, (2) the thickness ofthe stronger electrolyte (Mitchell, 1993). The double layerbarrier performance of bentonite. When pure ¥vaterjHyc!l'atl!ic ConductivityThe changes of the hydraulic conductivity o¥'er time areshown in Fi**s. 8 to 18. These figures sho¥v the changes ofspecimen, H, and (3) the volumetric fio¥v ratio, Q..*lQi ,layer is si**nificantly related to the swelling capacity and{Figure 7 sho¥vs the r'esults of the liquid limit test ¥vithdouble layer of bentonite becomes thinner by attracting{,in the permeant solution did not appear clearly on theslightly than the ¥vaste leachate that was left alone for lyear. Also, the ¥vaste leachate diluted with the deionizedstronger concentration .The electrolytic solution obstructed the swelling of thebentonit.e for the following reasons. The electric diffusion{bentonit.e was exposed to the strong electrolytic solution.For the effect of the difference in the type of cation on theliquid limit, the difference in the type of cation dissolvedliquid limit ¥'alue.becomes lower for an electrolytic solution having the{of the bentonite contained in GCL decreased ¥vhen thefrorn sampling. The ¥vaste leachate immediately aftersampling obstructed the swelling of the bentonite morewater increased the free swell because the concentrationof the solution vas decreased by dilution. Taking thesefindin*'s together, the swelling capacity of the bentonite{held in a soil. Figure 6 shows the results of the liquid limitregarding the elapsed time, and this parameter' is a valuein ¥vhich the accumulated flow volume is divided by theporous volume of the specimen. Figures 8 to 15 sho vs theresults on the polvdered bentonite GCL permeated withthe chemical solutions. On the other hand, Figs. 16 to 18sho¥vs the results on the polvdered bentonite GCL permeated with the waste leachates.Figures 8 to 10 sho¥v the results of the hydraulicconductivity test with the single-species solutions ofNaCl, CaCi2 and KCl, respectively. The closed plotsindicate the case of usin*' the deionized water, in cont 'ast,the open plots indicate the cases of using the electrolyticsolutions. The hydraulic conductivity of the po vderedbentonite GCL was very low: k =2.2 x 10-9 crn/s for thedeionized ¥vater. Ho¥ve¥'er, the hydraulic conducti¥'ity of*Liquid LinlitThe swell and the hydraulic conductivity of a soilGCL becarne higher for the electrolytic solutions havingstronger ionic strength. As shown in Fig. 8, the hydraulic{*{J KATSUMI ET AL.86Pore volvrnes of now PVF [-]o 20i0-1(T5oso Go 2014e 15050o0o S1 OO1 20i01 O;e 20 s 80 IsoPere vo!ume*sof fle v_ PVF [ ]100 1801 o,"- -!* pi-rFT7; CCr Q ,Z'* ** =1 o's,, C.X{::: :C ?10 'X:i:O:}rT1 o-- ecL with Dl ,!faterl *-20eCLvilth r;_Ct GCL 1'iTth N C- eC'iTth N C(i = O 10(i = O 2SA?*'*D =F10 *':)20;:,.r D = - P* ', )(1 = O Se q,D = * M ': }Is15Test f10dvfat}on : I - 3 ye rs104J':J' :0505ThicknSs--s Yi s me sL r$H'{ s5 frequ8,r-n r?jdr3Lie cor u:SiY :yoososo404eo 'La30a･_o>va-(O : + C}{ )irl_10oo 2040 eO 2080Pofe10140>2010Oeo2e80Pore YC?lvTT s O,0lumes oS Sel', FVF j-1Fig. 8. The changes of the hl.'draulic conductivitl.', tl]e tl]ickness offOO>¥*J PVF {-]Fig. 10. The changes of the hydrau ic conductivitT.･, the thickness ofspecimen anti tlre volumetric fiolv ratio for powdered bentonitespecimen and the volumetric fiow ra:tio for polvdered bentoniteGCL with DI water and NaCGC.1, 11'ith DI Ivater and KCI soh tionso utionPore Yoiumes ef fiew PVF04oios¥velling capacity of bentonite means that the GCL, speci-[*]20300men became thicker and its barrier performance issuperior. The deionized'o 5o10¥vhen an electrolytic solution that could not s¥ "ell bentonite sufficiently ¥vas permeated into the specimen, thecrio t20thickness of the specimen ¥vould be almost the same asIsthe initiai value, and this specimen ¥vould sho¥v inferiorobarrier performance. This figure sho¥vs that the number:of total plots for the thickness, H, ¥vas less than that forOsthe hydraulic conductivity, k. This ¥vas because thethickness of the GCl, specimen ¥vas not frequentlyoso40measured in the testing duration. The thickness could be30obtained by measurin_g: a distance bet¥veen the color filterpapers, whose sides ¥vere colored ¥vith red ink; set up on'L;acvater could s¥vell the bentonite,so that the GCL. specimen became thick by the s¥vellingand sho¥ved excellent barrier performance. Holve¥'er,*o '>30:,o10oO102030the upper and the lo¥ver sides of the GCL specimen using:a micr'oscope. The thickness of the CJCL, specimen ¥vas40PQre voiurne-s ef Ael'i PVF [-]Flg 9. The changes of the l]1.'tlraulic conductivity, the tl]ickness offrequently measured at the ear'ly stage of permeation,because the thickness changed ¥vhen exposing the speci-specimen and the volumetric fl017 ratio for powdered bentoniteGCL with DI watcr and CaCl, solutionmen to the permeant solution. After the early stage, Iittlechange in the thickness ¥vas obser'ved, and the thicknessconductivity value ¥vas k=2.1 x 10-s cm/s when NaCl¥vas not frequently measured. The hydraulic conductivity¥vas calculated using a latest measured thickness. Thevolumetric flo¥v ratios in any of the cases ¥vere almostsingle-species solution of I=0.5 M ¥vas permeated intoconstant over time during the tests. Therefore, the satura-GCL. The electrolytic solution decreased the barrier per-tion of the specimen ¥vas almost constant over time.formance of GCL,. For the change in the thickness ofNext, as sho¥vn in Figs. 9 and 10, the hydraulic conductivit ., for the single-species solution of CaC12 or KCI alsoGCL specimen, the thickness for the deioniz,ed ¥vater'vasincreased from the initial thickness of H=0.5 cm by thes¥velling of the bentonite contained in GCL, and ¥vasreached to approximately H= 1.0 cm in PVF>5. Thisthickness ¥vas larger than that for the NaC1 solution. Thisis because the bentonite cannot s¥vell sufficiently for theelectrolytic solution as shown in Figs. 3 and 4. The largerdecreased ¥vhen the ionic strength of the permeant solu-tion was strong. The hydraulic conductivity values ofGCL, permeated with the single-species solutions of I=0.5 M ¥vere k= 2.1 x 10-5 cm/s (NaCl solution), k= 5 3 x105 cm/s (CaC12 solution), and k･= 6.7 x 10r, cm/s (KClsolution), respectively. rHYDRAULIC CONDUCTl¥,lTY OF GCLSO 20104 *SgO 1Pore vo:urTleef flow. PVP 1-]OeOS7Pore Yo lrr s o2010ele" L_O 40SO:ow PVF [-]o 'OO?O240230120 2402801 *O320i,,,, IoI0 --iot?::H102. OEeGL wi+h Di w ier- GC w;th NaC CBC(1 = D 10 M R D = O 20 M*1):1020eCt w:t NaC C Cf- (1 = O.?O, R' D = O.SO' j- eCLw;th N C C C(1 = 0.10 r.1 R D = I OO ,+ 1 :)Is15Bstir d r ix: n 1 1 - 3 ye ro-Y, :05tTh; ck-;:1 : 1ss .'/as F?1easL e{1 iess fr**' verEtiy th-Ein by ra e eenciLcti* tyo*oso'so'o40O_ 30r* 20LF:a20-=aIJ>30!10>oO 20oSOOPore voi*Jmesof1 OOO40180sO1ew. PVF i-]Pore Ye!ul?1es o20032Gfiow PVF l iFig, 11. The changes of the h _･draulic conductivit) , the tl]ickness ofFig. 13. The charrges of the h)draulic conductivit) , the thickness ofspecimen and the volumetric fio v ratio for powdered bentoniteGCL Ivith DI water and NaCI-CaCl, solution of I=0.1 Mspecimen and the voiumetric flow ratio for polvdered bentoniteGCL with DI vater and NaCt-CaCl. solution of I=0.5 Mo 4010Pore ve Jme-s oBO1 20Pefe volvrne-s o fio v PVF [-]f ow PVF [-1ISO20010*1:! - IQf'40 eo12* 480OC7Co:is_ O 20?4 o::140oO180: : : : '-･rrrr?fl*._,'--.1lo-i 0-3H10'o20ecL wlih Dl w tere = 0.20 t, ,*;- ecL ,Y, h r 3e e8Cli {1 = I oe,*: GCL Wf:h N$C C Cl* l*1eo ,1 RF C; = o so ,41 -)* GC Yl: NaC CaC = {{ = I Oe , , D = I ee lT)IsteF:- Ioo-os:::>oho!20Oloo 4080120 200 240160Pore ve Jme-sof f ow. PVF [-]20'v ' J ' i･,':;1'110oo 20oeO 120aoOo140IsoPore voiume-s of now PVP j-]Fig. 14. The ctlanges of the h,.'draulic conductivit)', the thickness ofspecimen and the votumetric flo,v ratio for powdered bentoniteGCL with DI water and ¥. *aCI-CaCl. soliltion of I=0.2 Mspecimen and the volumetric fiow ratio for powdered bentoniteGC.L with DI water and NaC.1-CaC12 solution of I= 1.0 Mthe hydraulic conductivity of GCL permeated withon the hydraulic conductivity of' GCL, the hydraulicconductivity value became high ¥vhen a large amount ofCaC12 was contained in the permeant solution (namely,NaCl-CaC12 multi-species solution having a certain ionicstrength, the permeant solution havinga the strong ionicRMD ¥vas small) under the lo¥v ionic strength as shown instrength decreased the barrier perfor'mance of GCLsuch as calcium attracts the crystal layer, ¥vhich hasnegative electricity, of bentonite more strongly than agreatly. This reason closely relates to the above-describeds¥ 'elling capacity. That is, when the ionic strength of the;>soFig. 12. The changes of the h,_'draulic conductivit･.', the thickness ofNaC1-CaC12 or NaC1-KCl. As shown in Figs. Il to 14,i* ,****-***. :i40Flgures 11 to 15 shows the results of the hydraulicconductivity test ¥vith the multi-species solutions of{2 - 3 yearsso40oduratienTr :d(ness hvas fT Bas red i -gs reqver :'/ jh :'-n r,ldr8v; e eerK Lcll' ty* 3 )o_* ZososoeT stin10Frg 1 1 . In general, the multivalent exchan*･eable cationmonovalent exchangeable cation such as sodium, andpermeant solution was stronger', the bentonite could nots vell sufficiently hence the bentonite specirnen sho vedinferior barrier performance. For the effect of the mixingdecreases the swelling capacity of the bentonite because itbecomes difficult for ¥vat.er rnolecuies to enter bet¥veen theratio RMD of the NaC1 solution and the CaCl, solutionered to deteriorate when a large amount of CaC12 iscrystal layers. Thus, the barrier performance is consid- KATSUivll ET AL.88Pore voivmes of fiow- PVF {-iior*Pore veivrnes of ow. PVF [-]O 20 SO 100 140; r; lc-4080i201 o'Ei: i:: ' Io>0::ovv oF'-'*10sOS 2So'{r: : r :rr:L L !::l;10 "' , ,,io s-leecL v,Ith waste !e cbate ,e ( itered}4- GCL '/1Sh ,, s e {e eh te A10(: 2'oecL 1'iit" Is5F; Q'swfth w ste Isach SeoTe t ng dLJ? :x)n : 2 ye rsTr :kr)e-sso:: 4040: 3'oe;a20a15> io40 80 I0BoPore Ye vmes o{ f:ol'i, FVF i-)140t n trydrJ x; corx uotF, tyso2.0eJ.*,_(o 20vS s measuT;d 18ss fr querlo50a' '(f,itef d)+ GCL with was'e * cbat* K0_5:50o- GC10ote H { iteredjl - GCL wfth Yia5 e :8ach tB S (nlt redjC with ,ias e leeeh;te S,,,o- Io.･/ ste IB eilHF GCL w:th IYas e le chate h20e'{s300 3502001 O-e)_1!O 501 ooio>o1 20o soooSoPe,e voiumes ot200250soo 350ow, PVF l-]Fig. 15. The ehanges of the lu_'drauiic conductivit)', the thickness ofFrg 16. The chano*es of the h¥.'draulic couductivit¥.', the thickness ofspecimen and the volumetric fiow ratio for polvdered bentoniteGC_L vith Dl water and NaClKCI solutionspecimen and the volumetric fiolv ratio for powdered bentoniteGCL with vaste leachates A, H, S, and Kcontained in the permeant solution. Ho¥vever, under' thehigh ionic strength as sho¥vn in Fig. 14, the hydraulicconductivity value became small adversely ¥ 'hen a largeamount of CaC12 ¥vas contained in the permeant solution.In addition, from comparison of the hydraulic conductivity values for the NaCl single-species solution and theNaClCaC12 multi-species solution of I= 0.5 M in Figs. 8and 14, it can be stated that the hydr'aulic conductivity forthe NaCl sin.ale-species solution is much hi_ :her than thatfor the NaCI-CaC12 multi-species solution. These findingslead to a conclusion that sodium becomes more sensitiveto an increase in the hydraulic conductivity than calciumwhen the ionic str'en_g:th increases. As the proof of thisconsideration, sodium decreased the free s¥vell of ben-tonite more than calcium at a high ionic stren*'th assho¥vn in Fig. 3; the free s¥vell values ¥vere 6.5 mL/2g-solid for NaCl solution and 7.9 mL/2 g-solid for CaC12solution at I= 0.5 M. In part, the hydraulic conductivityvalue in the case of per'meation ¥vith NaC1-CaC12 solutionhaving I=0.5 M and RMD= 0.2 Mi/2 as sho¥vn in H 13¥vas much decreased at PVF>280. This is because theGCL pore might be blocked by the migration of thecolloidal matters contained in GCL. On the other hand,Fig. 15 sho¥vs the hydraulic conductivity of GCL permeated with the multi-species solution of NaCI-KCl. Inthis figure, the hydraulic c.onductivity for the single-Pore voiumes o ilow. PVF {-i101a so1 OO 200SO^o 501001 SOi300 350･50300 3soIo::c:v s loI0:E10 *2.0u Is0 , Ie'; 05o5_ols 40= 3a_*12.0"'**.=a>sloo1502eOPore Yotunles of f ow PVF [-]F g 17. Tl]e changes of the hl.'draulic conductivitl.', the thickness ofspecimen and the volumetric flol ' ratio for powdered bentouiteGCL Ivith vaste knchate K and i ts diluted solution ( x 1.5 and x2.0)in the type of cation appeared in the hydr'aulic conductiv-ity value, even ¥vhen the valence and concentration ofspecies solution of NaC1 and KCI under I=0.1 M iscation dissolved in each solution ¥vas the same.shown as a reference value. When the permeant solutionconductivity for KCI solution ¥vas highest, and theFigures 16 to 18 sho¥vs the results of the hydraulicconductivity test ¥vith the ¥vaste leachates. Figure 16shows the hydraulic conductivity of GCL permeated withhydraulic conductivity for NaCl solution ¥vas lo¥ver thanthe ¥vaste leachates A, H, S, and K. The hydraulicthat for NaC1KCI solution. This may be due to theconductivity values for the ¥vaste leachates A, H, and Swere as lo¥v as k< 1.0x 10 8 cm/s, and in contrast, thehydraulic conductivity value for ¥vaste leachate K becameof I=0.1 M was permeated into GCL, the hydraulics¥vellin_ ., capacity for the electrolytic solution as sho¥vn inFigs. 3 and 4; namely, it ¥vas because the KCI solutionobstructed t,he s¥velling of the bentonite more seriouslythan NaCl solution. It ¥vas concluded that the differenceas hi_g:h as k= 6.4 x 10-7 cm/s. This was because the wasteleachates K had a higher concentration than any otherj 89｝｛YDR．へULIC CONDUCTIVITY OF GC「LS 100 Pore volurnes o『移ow PVF Erl1。70 10 2。 30 4。 50 6G一851αさ工“GCい，V、Lhx4dr獄ξ｝dwa5【e陸ξcna幅K（轍εrεの噸h GC」w壇h x8dllL詫3d wa5に匠設d旭監a K（篠ヒerεd） 20門岱rGCLWヒhx16qぼεdwastel5憾dr凄憾Kσ誼erεd）E→ロ』GCL、v、竃hx32d置 戚醜wasteleヨ鵬にK（f・磁r館）燈r GCしW、匙hx64d言戯eGwa5【e海aα旧ヒeK（硫ereのo− 10Testi㎎d甑欝匙｝on 2years1・・職翠∼lll 諜§ ！甚1・・ノ 1窪 05Dl waterNaCI so［utionCaCb＄o！utionKCI solutionNaCトCaClっsoiutionNaCトKCl so臨bnWa＄te leachate〔）i賦ed waste Ieachate丁園㈱SSW尊號a購d睡ssf剛鉱晩吻σ「蹴C図戯M亡y− 0 50田 じ o0 20 40 60 80 歪00 ∈ヨectrlc condcutivitity of inぎluent ISlm】鳴 403山ε 。 30．§9巷著2DFl9．至9．Comparison…n揺1eelectricconduc症ivltyof e撮uenねccordi購9吐oASTMD6766……o苔 1D〉i臓翁uen【 and 00 1G 20 30 40 50 60 Pore yo塁り露短S D”low PVF 日F韮g．18。 The d臓nges of the hydraUic conductiviIy，霊he thicl｛ness ofof GCL．In any testing cases，t量1e hydrau星ic conducξivityof GCL was evaluated as approximatelyん撚2．0×10−9 specimen 段nd the vo雇umetric 行ow rat韮o for powdered ben吐onitecm／s in PレF聯7，bu重the hydraulic conductivity increased GCL wlth waste ieac掴症e K a賑d its diluIed so藍uIio臓（x4。O to×gra（iua正ly over t圭me in Pレ労＞7．For the waste leachate 64．0）wlth the dilution m＆gni長catlon factor of4．0，ln particu−lar，the紅ydraulic conducti、・ity increase（i from左；2，0×1each飢e；the electric conductivity values were O．24S／m（waste le＆chate A），o．93S／m（waste leacha重e H），4，17S／m（waste leachate S），and29．3S／m（waste leachate K），respectively。Tぬe nltrεしtion of the waste正eachates har（墨1yaffected the hydraulic conductivity value of GCL数ydraulic conduct量vity apPeared in the cases of using tぬewaste leachates having the e豆ectric conduct宝v主ty of聯8．58wαste leachate K w圭｛hout負1tration．The reason for thisS／m，which had a value for the waste leachate wlth thewas because the GCL pore speclmen migh重be blocke（1bythe colloidal matters contained in the waste leachate。dilution magni且cation factor of4。O．rθノ7ηinα！ion Cl−iオε’婚iα（λブ1Loη9−Tθη11乃rアゴ14αμ1iぐCon4己κ一がvめ7Tε3∼I7and王8show the hy（irauiic conductivity of GCL per− As a general crite11ia to termlnate the hydraulic conduc−tivity test，it is necessary to satisfy the fo至10wing threeFig。17，the closed circle plots indicate a test玉ng case thatpoints；（玉）the hydraulic conductivity value圭s stab正e overwas conductecl immediately after sampllng waste Ieacha重etime，（2）the volumetric How ratiQ ls approximately l，andK，εしnd on the other halld，the open circ正e plots in（iicate a（3）the pore volulnes of f董ow of aξ1east20r more are per−test圭ng case that was conducte（i by using waste leachate Kleft alone for l ye＆r from lts sampling．The difference of lorder magnitude appeared in the hydraulic conduct重vityevaluate（i from each testing case．Probably，the organicsubstances contailled may be deteriorated by至eaving thewaste正eac負ate alone for l year．For the effects of themeate（1into the bentonlte specimen。It is also one of芝heimporta互1t criteria to establlsh the chem量cal equl1量briumst叙e before the test is terminated（Bowders，19881Sむack−elford et al。，1999）．Shackelford et a1．（1999）suggest t数atthe electric conductivity ofthe inHuent and ef巳uent can beused as indicators of t紅e chemical equ圭libriunl state，andd童luted solution on the ぬydraulic coHductiv量ty， therecolnlnend tha重（4）the electric conduct圭vity ratio of thehydraulic conductivity for the（ii正uted waste leachate wasinHuent an（1efHuent fall with量n O。9−1．l before the test is王ower than that for the und玉1uted ∼vaste leachate，terminated．ASTM D5084explains in detail about theHowever，the difβerence beξween the dilu塗ion mαgnihca．criteria described in the above−mentloned（1）to（3），ontion factor of1．5an（i2．O h段rdly＆PPeared in the hydrau1−the other hand，ASTM D6766“Standard Test Methodic conductivity value．The test呈ng cases of using the wastefor Evaluation of Hydrαulic Properties of GeosyntheticIeachate dilute（i Yvith more deiol1玉zed∼vater is shown inClay Liners Permeated with Potelltia旦y IncompatibleFig．i8．This且gureshows＆nimpressivepro負1e。Whenthedilution maglli丘cat玉on factor was more than4，0，thelong−term change appeared l鮭he hydraulic conductlvity多CONSIDERATIONSIeachate was use（i for the書est without且1tratlon。Figuresmeated wi宣h was重e leacha重e K and its dlluted solution．王n，Lpermeated with芝he e至ectric solut玉on having＆low concen−tration． In this study， the 豆ong−term change of thedecreased in PVF；250as sho∼vn in the testing case to usemauce of GCL might be evaluated excessively due toc圭ogging of the colloidal matters when the raw waste韮Therefore，辻was necessaly to be careful for the long一毛erm cぬange of the barrier pel齢εQrm＆nce w勤en GCL wasHowever，出e hydraulic conductlvity of GCL w＆s muchTherefore，it should be noted重hat the barrier perfor−萎10−gcm／stoえ；8．7×10㎜gcm／sveryslowlyin2years．L呈（lu圭ds”explains the cri｛erion regarding（4）。 Most hydraulic conductivl重y values obtained in thisstudy had already satisfied the criteria described in ASTM 90KATSUMI ET AL。＿ lo一の◇のA△セ口繍 10『PM＞）O GCしwilh Dl wate「口 GCLwlth NaC『◇ GCL with Caαっ△10おoコoq△ GCL wi匙h KCloo1αプコ10¶ε◆GCLwit贈aC1−Caα2（RMD司OOMtf2）A GCL w詫h Naα一Kα（Na（5）；K（5））雲ロコで＞ヱ讐盆番・oO GCL wlth Naα一Caα2（RMD＝020M∼12）圏 GCLwlth Naα一Caα2（RMD＝050M笠ノ2）1α902 04 06 08 て〔）lonlcstrenglhforcation岡F童9・20・Rel戯ionbeIweenthehydraulicconduαM重y鋤d芝heionlcs｛reng重hforchemicaisolu芝ionTable3・Res醸soflong・重ermllydraulicconduαivi重ytes重forpowderedbenIoniIeGCLPermeant solut重QREndoftes巖照ChemIcal compoundsType of solutlonDeionlzed、vaterNasOlutionCa sok星証on11Mlノ∼ハζ∫Z） Na聖 conc， Ca” conc． K学 conc．［M雛1 ［Ml 【MI ［へ｛］0．000。100、250，500．200。501、00K soIUtlonNa−Caso1面o陰0．100．250．500。100．三〇りooりqり0．000。000、00ccQりつc・0．200．50〇、101．000．200．200．200．500、500．500、200，501．00王．00Na−K solu［めa0．001．000．200。501．000．200、501．001．000．圭0劣0、50∼Vasτe leac｝1a【e．AWaSteleacha！eA（飲ered）Wasleleac鮭ateHWaSteleacha【eH（食1tered）、Vas［e｝ea（：hateS、VasteieacぬateS（f灘tered）りc0．000，200．50玉．000，000。000、000．000．000．000．050．110．150．080，170．260、130．300．500．190．440．780．100。500．00000、0，000、000．玉00．250、500．00G，000．000．040．020．010．080．060．030．220．180，…30．450．390．310．000、000．000．000、000．000．000、000、000．200．501．000．000．000．000．000，000．000、000、000．000．000．000．000、100。50pH EC［一1 ［S／ml7．045．68TimelyearlPI乙F pH ECl−l H ［S／ml 0，02く320．66 8．0518、43く259．17 8「0742．10く20．31 んlcm／sl2、、24x10＝918．0王4．61×10鼎94！．80玉．41x10皿s17．8韮1．83x10−s5，425．368．568、889．2476．80く158．61 一16．85く藍 三2、22 8．1935．90く1 5．15 ＿62、40く123，72 6．5766。002．80x10づ7．9321、60＜2129．04 8．1724．203、30XlO−s7．577．3749．10く1 5。G795，40く127．69 −11、48く369．69 7．1611．311、ア0×10而s14．22三．52×10略17．8夏6．40×10−9フ、59144．85 7．692、13×10づ5，25×10柵52．76×10鼎66．69×10』614．OIく3！10、70 6、65I6，43く362．97 6．8820、10く3213，80 7．432王、403．12×10糟823．80＜3157、58 7。5126．201．37x互〇一s1，75×10『呂24．60く3互72．10 7、1129．6040．40〈3296．93 8．6143、502．55×10㌣947、60＜392．95 7．4948．804，37×10−854．30く394、74 7、0459，402。86×10憎s71，30く2135．13 7．1078．008．17XIO−885。20く2145．29 7，2982．708．63×10楠s92、40く284．99 10．95く218．20 8、227．1099．003．王2x10一胃11．424．26x｝0』91，47X lO−91．16×10榊5〈127．97 ＿〈210．26 7．94豆．32 0．25く211、04 8．482．031、00x王0府9 0．93く2！4、2．392、384．274．231、96x10−95．986．50128．806、917．977．85 0．2429 8．08 0、79＜214．34 7．7211．79 4．17く210、87 7、7211．74 4．08く211、28 7．47i．95x10−92、17×10”91．89XlO−97、757．3i29，30く2315．59 70329、806，38×10鼎7WaSteleachateK（魚eredソ29．70〈2322．04 7．6429．406．16x10学7Wasteieac駐ateK（飛ltered）こ6，4030、30＜2210、99 7．4229．玉05．三9x10−s ×1．5d玉luted（負1【ered）26、3120．50く252．92 20．601．23×10榊s ×2di1厩ed（丘ltered〉ユ6、256．356。4515．76I．09×玉〇一§、、1aste leachate K ×4d1luted（翫ered）肝 x8dlluted（丘ltered）ユ x16diluヒed（最1tered）2 ×32曲ted（飾ered）ユ x64diluted（負ltered）ユ6．466．396．547．4816．26＜260．67 8、57 8、58く250．01 8，078。538．66×10憎9 4．34＜23王叫49 8．101、20x10−s 2．32く233．19 8、、394．242、25 1．46く230．20 8．531。558．14XIO−9 0．60く217．62 8， 242．135．50×10柵9互．圭7×10榊sused immediately after sampllngusedaf｛erlyearfromsampling韮 fHYDRAULIC CONDUCTIVITY OF GCIS91- 10-7c"_v1 O -3o_i>'$(>>o:; I O10476 835 9; ;128 895 4i O 5;;B1::1 0-6c:c:oo::::1):>:Heig t of Bar - Pree swe!i [mL/2g-soiiid]Valve on the top of 88r - Eiectric condvctivity [S/rn]';47 6i O-B>10:c:a1 O-9oV::(QoooO :i zzi g (Q cT ('dO :!(U(' trQCQa a acQ:rQa)e)OCQ2:o( zo( zc :;a,oC554 3'40 4;;/////.o';O 02e)+co' ; ; ;:.iO-':;c5Lf):,::,tf)oo a:o(oO oo) aoQ(:oo(oC:tr)a:Z:o((b) J = O.5 M(a) I = O I MFig. 21. Effect of the electrol .'tes on the h)･draulic conductivit¥. of GCL: note that the electric conductivit¥.' of each solution is quite different even ifthe ionic strength is the same. In actualit¥. , the electric conductivity values of the solutions of I = 0.5 M Ivere 76.8 S/m (N 'aCl solution), 35.9 Slm (CaCl. solution), and 95.4 S/m (KCI solution), respectiveh.'D 5084. However, in the cases of using the permeantsolution of the lo¥v concentration, the hydraulic conductivity values increased gradually as shown in Fig. 18. Thebarrier performance of GCLS must be evaluated inconsideration of a long-term change of the hydraulicconductivity. Figure 19 sholvs the electric conducti¥'ityof influent versus effiuent at an ultimate state of thehydraulic conductivity test. According to ASTM D 6766to achieve the chemical equilibrium, the hydraulic conductivity test is required to be continued until the ratio ofthe electric conductivity of' effiuent over the electric conductivity of influent falls into 0.9-1 . I . Figure 19 indicatesonly the monovaient cations of NaCl and KCI made thehydraulic conductivity as high as k= 1.2 x lO5 cm/s atI=0.5M. In the hi**h ionic strength of ; 0.5M, thehydraulic conductivity values to the single-species solution ¥vere approximately k = I .O x 10 5 cm/s regardless ofthe difference in the valence of cation. However, themulti-species solution composed of the monovalent anddivalent cations increased the hydraulic conductivityvalues to k=i.OX 10-7 cm/s in the same range of theionic strength. Although the hydraulic barrier of bentonite to the single-species solution has been traditionallyexplained from the thickness of electric diffusion doublethat the most hydraulic conductivity tests conducted inthis research satisfy the termination criteria of ASTM D6766. Most tested GCLS achie¥'ed a chemical equilibriumlayer' and the size of hydrated ionic molecule, thehydraulic conductivity to the multi-species solutioncondition before the tests were terrninated.kno¥vled**e re*'arding the hydraulic conductivity to theSunllnaly oj'Long-Term Hydrau!ic Conductivity TestThe results of the long-term hydraulic conductivitytest are summarized in Table 3. This table shows theelectrolytes on the hydraulic conductivity of GCL undercannot be simply predicted from the traditionalsingle-species solution. Figur'e 21 sho¥vs the effect of theproperties of the permeant solution used, and the resultsat the end of the hydraulic conductivity test using its solution.{Figure 20 shows the relation bet¥veen the hydraulic,;conductivity of GCL and the ionic strength of thechemical solutions. The open plots indicate the hydraulicconductivity for the deionized water or the single-species{solution, and the closed plots indicate the hydraulic{,conductivity for the multi-species solution. The hydraulic;{{I=0.1 M and I=0.5 M. The hydraulic conductivity ofGCL fo ' CaC1, solution of I=0.1 M ¥vas referred to thedata reported by Lin et al. (2000). The hydraulic conducrivity for the deionized ¥vater was as lo¥v as k = 2.2 x 109cm/s, in contrast, the hydraulic conductivity for theelectrolytic solution ¥vas higher than that for' thedeionized water. For the hydraulic conductivity to thepermeant solution of I=0.1 M, the KCI solution increased the hydraulic conductivity of GCL more slightlythan any other solution. On the other hand, the electrolytic solutions of I=0.,5 M sho¥ved that the hydraulicconductivity of GCL permeated with the electrolyticsolution became higher when the ionic strength of theconductivity with the single-species or multi-species solu-solution was stronger'. The infiuence on an increase in thehydraulic conductivity significantly differed bet¥veen thesingle-species solut.ion and the multi-species solution.siderably higher than those ¥'ith the multi-species solu-tion containin*' only monovalent cations became con-tion containing divalent cation for the same ionicstrength.Most of the hydraulic conductivity values to the multi-Next. Fig. 22 shows the hydraulic conductivity of GCLspecies solution ¥vere lower than those to the single-spe-permeated ¥vith the ¥vaste leachates. As sho¥vn incies solution, and these values ¥ver'e smaller' than k-= I .O XFi**. 22(a), the hydraulic conductivity of GCL became107 cm/s. In part, the multi-species solution containinghigher for the ¥vaste leachate having the higher' electric lKATSUh41 ET AL.92conductivity. This reason can also explained by the s¥velling capacity of bentonite as sho¥vn in Fig. 5. On the otherby leaving the ¥vaste leachate alone for I year.hand, Fig. '-2(b) sho¥vs the hydraulic conductivity forApp!icahi!ity ofEva!uatioll Mlet/70ds }vitll Chenlica! Inor-¥vaste leachate K and its distilled sohrtion. The hydraulicganic So!utionsIn this subsection, the results obtained by using thechemical inorganic solutions lvere compared lvith thoseobtained by using the real waste leachates. Here, thechemical solution means the permeant solution that waseasily made of inorganic substances such as NaCl, CaC12,or KC1. All experimental data obtained in this study ar'esummaTized in Table 4.conductivity for the diluted waste leachate was lowerthan that for the undiluted waste leachate, and ¥vasdecreased with the increase of the dilution magnification.In addition, the waste leachate that was left alone for 1year from sampling sho¥ved the lo¥ver hydraulic conductivity than the ¥¥'aste leachate immediately after sampling.The organic substances contained might be deteriorated1 OI O e(,)v_v_! ( 10>:; 10 f:>o:;Oo:el:;:'c:ooae) I O-::=o IO1:'I> 10:hI 10<5 c/)I hco v'o;Lf)cccio :l:o :0'c:FV fi ll :z:oo f] Ilhaio r(c[1 llf::( :oUJ J :l:oLIJ 810cLLuo n liJl:)1Q, Q,(Lr)l :,(1)1:)1):: c¥1:: ,t : t)1:,Ls) 1:,e)Q,a,q,::::co1lc:)(OC Jcf) ( )xJ c LIJ(a) Waste leachatesA H S and K(b) Waste leachate K and its diluted solutionsH .'drau]ic conductivrty of CCL forFicF. 22.vaste knchateSummary of results for pol"dered bentonite GCLTable 4.Permeam solutionTesting FesliltsChemical compoundsI RM:D Na conc. C_a2Type of soiution [lM] [lM *2j [iM]Deionized ¥vaterNa solu ionO.OOO.02O . 04O 05O.060.08O 10O_ ,_OO.2SO 50l .OOC_a solutionK solutionoc-O.OOO 040.08*f*0. I O'-f-O.12c=O. 1 6O.OOc:'c*f_cc]coc:.O.200.50O.OOO.OOO OOl OOO . OO0.02ooO . 04*f_O. I OO.05O.06O_08O.10O.20O.25O^501 .OOc.,':*c_,c:'c'c=f_:*0.20O_40O.501 ^OO2 OOO.OOO.OOO OOO OOO_OOO.OOO.OO0.00O OOO.OOO.OOO.OOO OOO OOconc. K conc.[ivl]O OOO.OOO OO0.000.00O_OO0.00O.OOO.OOO.OOO_OO0.05O. I OO 25O.50O OOO.OOO OOO OOO OOO OOO OOO OOO.OOO.OO[lv. 1]pH EC Free s vell. Liquid limit Hydraulic cond[ - I [S/m] [InL/" sol d] [o! ] k [cm/s] "33 O23 2619 5 2 24x lO 9OO7 . 040.0,_O.OOO.OOO.OO6,686.364 2069.91O . OO5,7)1 ,_ 09O_OOO.OOO.OO5.665.68l 5 .095 . 4434.30O . OO5.4,42. I O8.lO .OO5,365^18766 5111 '-6,09 O8.07 97 815 O98.5OO^OOO.OOO.OOO_OOO.OO050. I O8.568 889,247.577.366,89O_ 1 26_81O_ 1 66.687.937 747.577.377.32O . 04O.08O.200.40O_501 .OO2 . OO8 . 061 8 .4380l 29. I O9.0316.8535.9062^405 . 059 7612.0613.5517^7719,018.518.016.015_991185.0136 2l 14-92.13 x 10l.83 x lO s5 25 x lO '2.80 x lO )9.27 27,l7. l41.lO5,049. I O5.04*54.0169.80I 41 x lOsll.l2 1 _6095 ^ 404 61 x l0 9181.03.30 x lOs)_.76 x lO66 69 x l0 6Table 4^ coutinued on next page セ93｝｛YDRAULIC CONDUCτIVITY OF GC「LS…hble4．con韮inuedfromprevlouspageTes“n黛 resu玉tsPermea瓢soluτionCねelnicalcompounds Free swel1 王jquid limit H｝『draulic cond、1 RMP Na一conc．Caユ甲conc、K廟conc、 P｝｛ EC ［M】 ［M1 ［MI 卜1［S／m】 lmL／29−solidl ［％】 たlcm／slTypeofsoiutionlM】 ［M匪〆3】翼a−Ca solution0．040．070、05 0．200。05 0、500、05 1．000，090．10 0、200，050．10 0、500．玉10．000、040、020、10 1、000．150、010、20 0．200．080．170．080．20 0、500．260、130，300．500．20 1．000．50 0．200、50 0、500、50 1 ．000．191．00 0。20…0、10 つつ0、440．780．040、080、100．120、10 」つ0、三60．50 0c0、、501．00 0．501．00 墨．00Na−KSdutlon0．王0 コつ0．10 つ￠0．10 フつ…韮き妻妻韮0．020」010、060，030．220、180．130、450．390，310、000．000．000．000．000、000．000、000．000、000．000，000．000．000．000、000．000．000，000．000、000．160．120、100、080、040．5014．017．Ol9、01、70×10−s9．5 11、48 14．0110、5 16．4314．01、52x10蘭s6、40×10甲9 20、108．2184、玉3、12×10一＄ 23．808．5179、「71、37x10略 24．60 40．4010．0玉80、41．75×王〇一sB1、68．02，、55×10瞭9 47、608。2127．74、37×10酔s 54、308、5127．72、86×10−s 7玉．307、2122．98．17x10酬s 85、208、0i1368，63x10−s一一 92．408．2102．23，12x10一薗7．23 1！．4711、97．35 王1、167，59 io、9513、0147．68 10．7314、27．83 10．5416、94．26×王0｝9，05。98 王28、804、8WasteleachateA6、50 0．24WasteleachateA（丘ltered）6．91 0，25Waste！e段chateHWasteleachateR（創tered）7．97 0、93、Vaste leacねate S11，79 4．17V》as［eleacむateS（f灘｛ered）11．74 4，0828、028．026．026、023．025．07．85 0．791、16x10僧5580．61，47×10−9629、91、00×10簡956521、96×10−9562、31，95×10皿9523．52．17×10｝9517．71、89×10−9∼Vaste leac｝1a【e K7、75 29．36．0165、56，38x10一「WasteleachateK（丘1tered）IWasζeleachate駁（脈red）ユ7、3玉 29、75。9165、66、40 30，307．06、16x10｝「5、19x10−s ×1．5diluted（負ltered）26．31 20．507．1玉．23x10備s ×2diluted（自ltered）ユ6、25 16、268、5I、09×10FS ×4diluted（51tered）26．35 8、，5812．i8．66×10−9 ×8dlluエed（自1ζered）26．45 4、34l7、41、20x10欄8 ×玉6dil凱ed（負ltered）26、46 2．326．39 1、46 x64diluted（翁ltered）ユ6．54 0、6024、727．529，51、17×10−s ×32diiuted（負ltered）ユ814×10−95、50x10榊9usedimmedla芝elyaftersamplingused after l year from sa臓1Plings700600 1＿ 104 働、 O≧ 亀，鐙③、9500Oの鋤ノ○ ○￡ 10『5Oメ 催oむ㊤彗．だ 400∈○呈 噛〇一ア2oσ 3005コ 200、．爵joo OO Oも ○oコ、A−h8re x瓢Free5㌔ve目〔mし／29−solldl0 10『9着き0工 1α鴇5 10 15 20 25 3035 Free swell lmL129・solid】Flσ23．嘩0 1α5藍 y＝LlqUld II醸t［％］0 ⑧のy酋206x （R篇0．97｝びo○どRelaIio“between芝heliquid疑mitandthefreeswell020 40 60 80 100 120 140 Eヨectric conduCtM鞍 IS！m】Fig。24．Rel郎ionbetweenthehydr旦騒licconductM｛ya臓d象heelectric conduc症ivity KATSUMI ET AL.94ate the hydraulic conductivity of GCL from the ionic1 aOi O-sv_qq, h r>o i a'T]hn o ::):,c:I O-G,,c:,,>O-9x ;; Fr e Ewe:; [mL;29 sQi:dj', O bse>r rstren*'th, ¥vhich is the parameter considering the type andconcentration of the solution, is not practicable. In orderL e p( ix bJ) j :;QB3)y s: Hydreu;io co{ItiL;c v'ty_ iOot)le)3.0= -e 31ern"5irnL/2e-solidx io ? crn's (H' 'alJi=c conducifY'tys x to Inf:ntty'e-OQ Oee----d -------iO eO ee 8JO W ste :eachate0-1a 1 5 20 25 30SPree sv i! [m /2g-soiid]Fig. 25. Relation between the hl.'draulic conduct vit)' amti the free slvellfor GCLS confined at 29.4 kPsFigure 23 sho¥vs the relation bet¥veen the liquid limitand the free s¥vell. The liquid limit tests were conductedon '_4 types of permeant solutions as sho¥vn in Table 4.These index values ¥vere almost in a linear relation regar'dless of the type and concentration of the permeant solution. Figure 24 sho vs the relation between the hydraulicconductivity of GCL and the electric conductivity of thepermeant solution. The electric conductivity was used asto evaluate practicably the hydr'aulic conductivity ofGC_L, the hydraulic conducti¥'ity should be indirectlyestimated from the relation bet¥veen the free s¥vell and thehydraulic conductivity as sho¥vn in Fig. 25. Even if thetype and concentration of the permeant solution cannotbe specified, the free s¥vell to the solution will derive thehydraulic conductivity. This method to evaluate thehydraulic conductivity of CJCL, permeated ¥vith an inorganic solution is especially available in investigating thebarrier performance of GCL that had been applied at a¥vaste containment facility. The barr'ier performance ofGCL, can be estimated by (1) sampling the r'eal vasteleachate from the waste containment facility, then (2)conducting the free s¥vell test with the waste leachate, andfinally (3) evaluating the hydraulic conductivity from theobtained free s¥vell using the regression curve:lo*' y = exp (a(x - b)) ( i )c¥vhere, x is the free swell of bentonite in GCL, (mL/2g-solid), y is the hydr'aulic conductivity of the GCL (cm/an indicator of the permeant solution because the ionics), a is - 0.31 , b is 8.69 mL,/,- g-solid, and c is 3.09 x 109strength, which is ¥videly used in permeation problems, ofthe ¥vaste leachate could not be calculated correctly. Thecm/s ¥vhich is the hydraulic conductivity at x to infinity. .tendency of the hydraulic conductivity for the chemicalsolution ¥vas similar to that for the waste leachate in therange of the lo¥ ' electric conductivity. Therefore, it ¥vasconcluded that the hydraulic conductivity of GCLS to beused in landfill bottom liners can be estimated by thehydraulic conductivity values obtained from the experiment usln*" chemical solutions having the similar electricc.onductivity values if the chemical solution had theelectric conductivity ¥vithin =25 S/m. In contrast, ¥vhenthe chemical solution or the ¥vaste leachate has the highelectric conducti¥,ity of >25 S/m, the hydraulic conductivity value may be significantly increased and scattered.CONCLUSIONSThis study investigates systematically the effects ofelectrolytic solutions on the bar'rier performance of geosynthetic clay liners (GCL,s), and discusses the adequacyof the hydraulic conductivity test ¥vith the chemical solution as the prediction method of barrier performance that¥vill be exhibited in a real site. The long-term hydraulicconductivity test ¥vas conducted on a nonprehydratedCJCL permeated ¥vith the chemical inorganic solutionsand the ¥vaste leachates, and showed the follo¥vin_"_.results.Figure 25 sho¥vs the relation between the hydraulic(1) The hydraulic conductivity of GCL, significantl .,conductivity and the fr'ee s¥vell. The hydraulic conductivi-correlates to the s¥vellin*" capacity of bentonite containedty tests ¥vere conducted on 40 types of permeant solutionsin GCL, and GCL sho¥vs excellent barrier performance ofas shown in Table 4. The hydraulic conductivity of GCLcould be given as a simple function of the free s¥vellregardless of the type and concentration of the permeantsolution. This relation is very useful in estimating thek< I .O x 10 s cm/sbarrier performance of GCLS or bentonite permeatedvith the inorganic solution, because the barrier perfor'mance can be easily estimated by the free s¥vell, ¥vhich canbe evaluated much more rapidly than the hydraulic conductivity. GCLS have excellent bar'r'ier performance ofk< I .O x 10-8 cm/s ¥vhen the free s¥vell of the bentonite inGCLS is lar*･er than 15 mL/2 g-solid.The type and concentration of the chemical permeantsolution has a significant influence on the barrier perfor'mance of CJCL. However, it is too difficult to predictthe type and concentration of the permeant solutionbefore CJCL is applied to a site, because the solutionpermeated into GCL is unspecified. Therefore, to evalu-vhen the free s¥vell, ¥vhich is an indexof the swellin*' capacity, ¥vas lar'ger than i5 mL,/2 g-solid.('_) The effect of the electrolytic solution on the hydraulicconductivity of GCl, could be explained by the ionicstrength for cation contained in the solution. Ho¥vever,the sensitivity of the ionic strength to the hydraulic conductivity was dependent on the type of cation. Potassiumhad an influence on the increase in the hydraulicconductivity more than sodium, even ¥vhen the valenceand concentration of cation dissolved in each solution'as the same. (3) The hydraulic conductivity for themulti-species solution containing the divalent cation ¥vas10¥ver than that for the single-species or' multi-speclessolution containin*' only the monovalent cation for thesame ionic strength. (4) The long-term change of hydraul-ic conductivity appeared in the cases ¥vhere ¥vasteleachates having the electric conductivity of = 8.58 S/m PHYDRAULIC CONDUCTI¥,ITY OF GCLS¥vere used. The permeant solution having the lo v electricconductivity intercalated a fe¥v exchangable cationsslo vly into the space of crystal interlayers of clay minerals. 'The exchangeable sites in clay minerals ¥vere gradual-ly occupied ¥vith the cations so that the volume of bound¥vater ¥vas decreased ¥vith time. As a result, the permeantsolution having the lo¥v electric conductivity graduallyincreased the hydraulic conducti¥'ity of GCLs. (5) In therange of lo¥v electric conductivity, hydraulic conductivityfor the chemical solution vas almost the same as that forreal ¥vaste leachate having similar electric conductivity.Therefore, the hydraulic conductivity test with chemicalsolution, which ¥vas easily made of inorganic substancessuch as NaCl and CaC*12, had a good possibility to4) Chang, r^, Skipper, N. and Sposilo. G. (1995): C*omputer simufation of interia¥'er molecular siructure in sodium montmorillonitehydrates, Lan*"muir, Il (7), 273427415) Fglofi tein, T. A,, (1995): Properties and tesl methods to assessben onite used in geosyntheric clay liners, Geo yn[hetic Cla_T'Liners. Baikema, Rotterdam, The Netherlands, 51-72.6) Egloffstein, T. A. (2001): Natural bentonites-infiuence of the ionexchange and partial desiccation on permeability and self-heaiincapacity of ben onites used in GCLs. Geotexti!es aird Geomellibranes. Elsevier, 19, 427444.7) Egloff ein, T. A. (2002): Bentonite as sealing materiai in geosynlhetic clay liners - Infiuence of the electrolytic concentration, theion exchange and ion exchange ¥vith ¥vith simultaneous partialdesiccation on permeability. Cla_v Geosynthetic Barriers (eds. byZanzinger. H., Koerner, R. ivl. and Gartung. E.), Slve s &Zei linger= Iisse, The Nelherlands, 141-153,,S) Fernandez, F. and Quigley, R. i¥,1 (1988): Viscosity and dielectricestimate the barrier performance of GCLS that ¥ 'ill beconstant controis on the hydrauHc conductivity of claye_¥' soilspermea ed lvith water-soluble organics. Can,, Geo[ech. J., 25,582-589.applied in an actual site if the chemical solution had theelectric conductivity ¥vithin = 25 S/m.Improvement of the chernical compatibility of ben-959) Gleason, ilvl. H.. Daniel, D. E. and Eykholt, G . R. (1997): Calci lmand sodium bentonite for hydraullc containmeu applicalions, J.Geotech. Geoenviron. E,,gr*"., ASCE, 123 (5), 438445.tonite is one of the important subjects to apply GCLS tobottom liners in ¥vaste containment facilities. ApplicationlO) Griln, R. E. (1968): C!a_v IV;finera!o*"_1'-2nd edition, McGra v-Hill,of multiswellable bentonite or prehydrated bentonite isNe¥v York.ll) Jo, H. Y., Ka sumi, T., Benson, Cconsider'ed an effective method of improving t.he chemicalresistance (Onikata et al., 1996; Shackelford et al., 2000;Vasko et al., 2001; Katsumi et al., 2004; Kolstad et al.,2004b; Katsumi and Fukagawa, 2005; Lee andShackelford, 2005a). In addition, the barrier performance of GCLS that ¥vill be applied in bottom liners isconsidered to be improved by the load of the ¥vastes bu-ried (Petro¥' and Ro¥ve, 1997; Katsumi and Fukaga¥va,2005). The barrier performance of modified bentonitesand the effect of confined pressure acting on bentonitemust be investigated in order to use GCLS Securely as aH and Edll, 'T. B. ('_OO1):Hvdraulic conductivity and s¥velling of non-prehydrated GCLSpermeated ¥vith single species salt solutioris, J. Geotecll. Geoenvi-ron. En*"rg., ASCE, 127 (7), 557567.12) Karabomi, S_ Smit. B.. Heidug, ¥V., Urai, J. and van Oort. E.(1996): The s¥velling of cla.vs: Molecular simulations of thehydralion of montmorilioni e. Science, 271, I i02-1 104.13) Katsumi. T., Oga va. A. and Fukagalva. R. (2004): Efi ct ofchernical solutlons on hydraulic barrier performance of claygeosynthetic barriers. Proc. 3rd Ltlr Conf. Ceosynthetics,70 1 -70614) Ka sumi, T_ and Fukagawa. R. (2005): Fac ors afi cting chemicalcornpatibility and barrier pertormance of C} CLs. Proc. 16thICSllfGE, ivlillpress Science Publishers. Ro terdam, Ne herlands,barrier material in ¥vaste containment facilities.228522S815) Kjellander, R., ivlarcelja, S. and Quirk. J. (1988): Attracrive doublelayer imeractions betlveen caicium clay particles, J. Co!!oid andAC.KNOWLEDGMENTSHelpful comments and discussions were provided byProfessor Craig H. Benson (University of Wisconsin),In!e!face Science, 126 (1), 194-21 1 .16) Kolstad, D. C., Benson, C . H and Edil, 'T. B. (2004a): Hydraulicconductivity and s¥vell of nor)prehydra ed geos_vnthetic clay linerspermeated ¥vith mul ispecies inorganic solutions, J_ Geotech.Geoenviron. Eng/ " , ASCE, 130 (1'_), 1236l249.Professor Masashi Kamon (Kyoto University), Dr.Masanobu Onikata (Hojun Co., Ltd.), and Mr. MitsujiKondo (Hojun Co., Ltd.). The GCLS ¥vere provided byMarubeni Tetsugen Co., Ltd. Thanks are due to Dr.Katsumi Mizuno (Hojun Co., Ltd.) and Dr. KazutoEndo (NIES) for providing the waste leachates for thestudy. Assistance ¥vith the experimental work ¥vas provided by former students of Ritsumeikan University includin_2: Shinya Hasegawa, Shugo Numata, and MasatoYokoi.REFERENCESl) Alther. G_, Evans, J_ C., Fang. H Y. and ¥ritmer, K_ (1985):Influence of inorganic permeants upon the permeabilit,.v ofbentonite, Hydraulic barriers in soil and rock, S'T'P 874 (eds. byJohnson. A . Frobel, R. and Petterson, C.), ASTllvl, ¥¥restConshohocken, Peunsylvania, 64-73.2) Bo 'ders. J J. and Daniel, D. E. (1987): Hydraulic conductivity ofcompacted clay o dilu e organic chemicals, J. Geotecll. E'ngrg,,,113 (12), 1432-1448.3) Bo vders, J. J. (1988): Discussion of terminarion criteria for claypermeability tesring. J. Geotech. Engrg., ASCE, I14 (8), 947-949.17) Kolstad. D. C., Benson, C. H., Edil, T. B. and Jo, HY_ (2004b):Hydraulic conductivi y of' a dense prehydrated G CL permeaiedvith a gressive inorganic solutions, Geos_T, 'nt/tetics Internationa!, 11(3), 233241,18) Lager¥verff. J. V , Nakayama. F S. and Frere, iM. H(1969):Hydraulic conducti¥'ity related to porosity and s velling of soll. Soi!Science Socier_v of Anlerica Proc. , 33, 3-1 1 .19) Lambe, 'T. (1958): 'The structure of compacted clay, J. Soi! J,ifech.Fbulrd. Div., ASCE, 84 (?-), 1-33.20) Lee, J. h,1_ and Shackelfbrd, C. D. (2005a): C*oncemrationdependency of the prehydration efi ct for a geosynthetic clay liner,Soils and Foundation5, 45 (4), ,-741 ,,21) Lee J, i¥,1. and Shackelford, C D. (2005b): Impact of ben onitequality on hydraulic conductivity of geosynthetic clay liners, J.Geotec!1_ Geoenviron. Engrg., ASCE, 131 (1), 64-7722) Lin, L , Katsumi, T.. Kamon, ,1_, Benson. C. H.. Onikata, l¥,L andKondo. N'I. (2000): Evaluation of' chemical-resistant bentonite forlandfiH barrier appiication, Disaster Prevention Research Institt/teAnllua!s. Kyoto University, (43 B-2), 5,_5-533.23) Lolv, P. (1987): S ructurai componem of ihe s¥velling pressure ofclays, Lall*"nu!ir, 3 (1), IS2524) Lutz, J F. and Kemper, ¥V. D. (1958): Intrinsic permeabilhy ofclay as aff cted by clay-1va er imeraction, Soi! Science, 88, 83-90.25)"lesri, G, and Olson, R. E. 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- ログイン
- タイトル
- Characteristics of Scanning Curves of Two Soils
- 著者
- D. Tami・H. Rahardjo・E.-C. Leong
- 出版
- soils and Foundations
- ページ
- 97〜108
- 発行
- 2007/02/15
- 文書ID
- 20983
- 内容
- rSOILS AND FOUNDATIONS¥'ol47, No. 1, 97l08 Feb 'OOlJapanese G eotechnical SocietyCHARACTERISTICS OF SCANNING CURVES OF TWO SOILSDFiNNY TAhi i), HARIA *TO RAHARDioii) and ENG-CHOON LFo*¥,Giii)ABSTRACTScanning curves of two different soils ¥vere obtained from three series of infiltration and drainage experiments ontwo physical models of soil slopes in the laboratory. The first slope model consisted of a fine sand layer overlying agr'avelly sand layer, vhile the second siope model involved a silty sand layer overlying a gravelly sand layer. Each soillayer had a thickness of 200 mm and both slope models had an inclination angle of 30'. The slope models ¥¥'eresubjected to artificial rainfalls of different intensities, followed by draining ¥vhere no rainfallvas applied. Var'iousinstruments ¥vere installed to continuously measur'e the changes in matric suction, volumetric water content and thewater balance of the slope models during the experiment. Scanning curves ¥vere then constructed using the rnatricsuction and water content data measur'ed at the bottom, middle and top parts of the slope models and ¥vere cornpared¥vith the primary drying and primary ¥vetting soil-¥vater char'acter'istic curves that were measured separately. It ¥vasfound that the scannin*' curves follo ved the primary ¥vetting cur¥'e during the adsorption process and then follo ved theprimary drying curve during the desorption process. During the transition period, over ¥vhich the scanning curvemoved from the primary dr'ying curve to the primary ¥vetting curve (or vice versa), the path of the scanning curve had arelati¥'ely flat slope as cornpared to the slope of' the primary curves, and sometimes it ¥vas almost horizontal. Holvever,the slope and the path of the scannin*' curves ¥vere found to be similar for the cases ¥vith similar initial conditions.Key ,vords: hysteresis, scanning cur¥'es, soil-¥vater characteristic curve, unsaturated soils (IGC: D4/E6/E7)due to its non-uniforrn pore size distribution. There areIN1'RODUCTIONthree specific mechanisms causing hysteresis (I¥vata et al. ,Hysteresis in the relationship between negative pore¥vater pressure or matric suction and water' content is1995): (i) dift rent por'e sizes of the soil in difi rentmoisture states, (ii) adsorbed lvater on clay surfaces andcommonly obser¥'ed for many unsaturated soils in the(iii) differ'ent contact angles bet¥veen the air-¥vater inter-laboratory. The path of the matric suction ¥'ersus waterface and the soil solid surface.content plot for the desorption pr'ocess (i.e., decrease inThe plot of water content or degree of saturation¥vater content) and the path for the adsorption processversus matric suction of soils is kno¥vn as the soil- ¥'ater(i.e., increase in water content) are different, as a result ofcharacteristic curve or SWCC. The ¥vater content of' thehysteresis. This phenomenon can be described usin*' thesoil decreases as its matric suction increases follo ving a'ink bot.tle effect' . When an empty capillary tube is placedin a water bath, the ¥vater table lvithin the tube ¥vill rise updrying (desorption) path and the reverse cycle ¥villincrease the ¥vater content along a ¥vetting (adsorption)path. The soil-¥vater characteristic curve is hysteretic;until ¥vater reaches an equilibrium state. In this case, thewetting cycle occurs. On the other hand, when the tube isfilled up ¥vith ¥vater, water ¥vill be drained out until itreaches an equilibrium state. The case refers to the dryingcycle. The equilibrium state achieved thr'ough a wettingcycle and through a drying cycle is the sarne lvhen thetube is straight. However, ¥vhen the tube has an expandedthat is, f'or a specific matric suction, the water' content ona vetting curve is always lo¥ver than that found on adrying curve. The drying curve that starts from saturation is comrnonly called the primary drying curve (Fig. l).Similarly, the vetting curve that starts from a dry (orrelati¥'ely low ¥vater' content) condition is commonlycalled the pr'imary wetting curve. The region enclosedwithin the primary drying and primary ¥vetting curves iscalled the hysteresis region. Besides the primary cur¥'es(or bounding curves), the "scanning" cur¥'es are series ofspace in the middle, the equilibrium state may bedifferent. The expanded portion of the tube is empty inthe wetting cycle, while it is filled with water in the dryin*'cycle. As a result, the water contents obtained from thewettin*' and dr'yin*' cycles are not the same. The abovesoil-water characteristic curves that start from a particu-lar condition that is neither saturated nor dry. Thesecapillary tube analogy applies to soil conditions in natureFormerly Research Scholar, School of Civil and Environmental Engineering, Nanyang Technological Universiiy, Singapore.*'* Professor and vice Dean, ditto (chrahardjoC"n u,edu,sg).Associaie Professor and Head of' Geotechnical and Transportation Engineering Division, ditto.The manuscript for this paper ¥vas received ft)r revielv on November 17, 2005; approved cul July 26, 2006¥Vri ten discussions on this paper should be submitted before September i, 2007 to the Japanese Geolechnical Society, 4-38-2, Sengoku,Bunkyo-ku, Tok.vo 1 12-001 l, Japan. Upon request the closing date may be extended one momh.j)=ii*C).l 98TA ,11ET AL.The focus of this paper is to compare and analyse60scannin*･ curves that vere obtained from a series ofinfiltration and draina*･e tests on a physical model of soil=0slopes in the laboratory. Both ¥vetting and drying40scanning curves of two different soils (i.e., fine sand andoa,silty sand) are presented Scanning curves measured atthe bottom, middle and top parts of each slope model¥vere constructed and compared ¥vith the primary dr'yingand primary ¥vettin_g: curves that ¥vere measured inde-o:IS 20E:,>opendently, to sho¥v the processes (i.e., drying or ¥vetting)oi lOo 101 0203Matric suction, (ua u ) (kPa)Frg 1. Primar¥_' soil-1vater clraracteristic curve and scanning curvesscanning curves are different depending on the state of thereversal point in the process of successive ¥vetting anddrying (see Fig. l).Researchers In the soil physics field have tried tomeasure and construct the primary and scanning curvesof a porous specimen in the labor'atory for a long time(e.g., Topp and Miller, 1966). Topp and lvliller (1966)measured the scanning curves for a poorly graded glassbead sample. Many other researchers have measured therelationships bet¥veen ¥vater content and pore-¥vatersuction for different soils (e._g:., Talsma, 1970; Watson etal., 1975; Topp, 1971; Poulovassilis, 1970; Poulovassilisand Childs, 1971; Vachaud and Thony, 1971; Nimmoand lvliller, 1986; Hogarth et al., i988, Feng and Fredlund, 1999; Pham et al., '_003). Ho¥vever, their main concern ¥vas the primary or bounding curves, rather than thescanning curves, in studying the hysteresis phenomena inunsaturated soils.A number of simple analytical solutions have also beendeveloped to provide forms for the primary curves thatexhibit hysteresis. In the early stage, the independentdomain theory. Ivas used to model the hysteresis of ¥vaterin soil. The soil pores are vie¥ved as independent domainthat have only t¥vo states, either full or empty, and eachdomain has t¥vo corresponding matric suctions for eachin an unsaturated slope under different flux conditions.The differences obser'ved in the scanning curve of thesetwo soils as well as the characteristic of the scanningcurve are analysed and discussed.MATERIALS AND METHODSDescription and Parail7eters of Soi!sT¥vo-layer soil slope models ¥vere constructed in thelaboratory to elucidate the mechanism of water flo¥v inunsaturated slopes. The soil slope consisted of relativelyfine soil over relatively coarse soil layers. Sllty sand andfine sand ¥vere used as relatively fine materials, ¥vhilegravelly sand ¥vas selected as a relatively coarse material.The silty sand is a local residual soil from the BukitTimah formation (Public Works Department, 1976).Bukit Timah Granitic residual soils vary from silty orclayey sands to silty or sandy clays, depending on thedegree of ¥veathering, but ar'e commonly sandy clayeysilts (Rahardjo, '-OOO). The fine sand ¥vas a sand used inthe Changi reclamation projects. The light grey to lvhitegravelly sand ¥vas crushed from fresh granite. These threesoils ¥vere selected to provide t¥vo-layer soil slope models¥vith contrasting hy. draulic parameters.The silty sand was ¥vell-graded ¥vith a coefficient ofuniformity, U* of I 120 and a coefficient of curvature, C*of 1.58, and was cate*"orized as an SM soil according tothe Unified Soil Classification System (USCS). The finesand ¥vas poorly-graded (U* of 2.1 and C* of 0.89). Thegravelly sand was a poorly-graded, uniform soil ha¥'ing50.10/0 of grains passing the No. 4 ASTN/1 (4.75 mm).state. Poulovassilis (1970) reported a theory that is applicable to glass beads and sands. Ho¥vever, other' re-Both the fine sand and _ :ra¥'elly sand ¥vere categorized assearches observed considerable discrepancies bet¥veensaturated coefficients of per'meability, k*, for the siltysand (at a dry density of I .47 Mg/m3), the fine sand (at apredicted and observed scanning curves (TOpp andpoorly-graded sand (SP according to the USCS). TheMiller, 1966; Topp, 1971; Talsma, 1970; Vachaud andThony, 1 97 1 ) . Muaiem ( 1 974) then pro posed aconceptual model of hysteresis that simplifies thecomputational procedures but _g:ives better agreementdry density of 1.56 Mg/m3), and the gravelly sand (at adry density of 1.62 lvlg/m3) were 2.2x 10-6, 2.7x 104with observations. Subsequently, Parlange (1976)proposed a model that corresponds to a special case ofto the dry densities used in the slope models. The basicparameters of the soils used in this study are sho¥vn inMualem's hypothesis, ¥vhich requires a knowledge ofTable I .only one primary cur¥'e. Hogarth et al. (1988), Viaeneand 7.6 x 10-2 m/s, respectivel}.,. The dry densities of thesoils in the permeability tests ¥vere controlled to be similarThe primary dryin_curves of the soil-¥vater character-(1995), Si and Kachanoski (,_OOO)istic curves of the soils ¥vere measured using a Tempeand Braddock et al. (2001) applied the classical Brooksand Corey (1964) and ¥'an Genuchten (1980) soil-1vater'characteristlc curve models to the Parlange hysteresismodel and reported that the predicted curves agree ¥viththe laboratory observation.pressure cell (Model 1405 BOIM3-3, Soilmoistureet al. (1994), L,iu et alEquipment Co., USA), ¥vhile the primary ¥vetting curves¥vere measured using capillary rise tubes. The Tempepressure cell operates on the same principle as the pres-sure plate apparatus as described in ASTM D 2325-68 r99SCANNING CUR¥'ES OF T¥¥*O SOILSTable l. Index and !1)draul c parameters of the soilslOO, l='ff'¥'==SoilsPropertiesll 1Fine SiltyUnlt Gra¥'ellysand sandsandUnified Soil ClassificationSpecific gravit}'SPsPSlvl2 622 652.595O.35O.230.17O.56O.O00521l 120Crain-size analysis resultsD6{)Inm 5 -D<0D orllm 3.6Smnl 2.7319Coef cient of uniformity, C*,Coef cient of cur¥'ature, C*Gravel contenl (>4.75 mm)Fines content (<0.075 mm)0.96o*/a 49.9OOI*lj ifi i_'I II]iil' iI' i: 50 11""""""""""_"'_'_'_ijt:i,i= * 'l=I =i *i i [,: [ rr'i'irT1 . I =';' j ' ILill ; i*===*i"4e20to*l{l¥ ,1= =:ilty=*d' l = :i iiir"^ -> 'IfiLiljfjl..-- 'I Ij!i '=i-= - 1f!II't llI02 10.89Ol.580.838 9l!!1 i" "Il__ =='' =L_;:i jU{ Illltol e*.:lly'' j_'* d spFi * =*nd sp-lllil1002o 1 o'ol o'ooiGr in size (mm)Atterber_ * IimitsLiquid limitOj'OPlastic limitO!!OPlastici y index, PIO/ IO4827Fig. 2. Particle size distribution curves of soils used in the stud,21Relative density test results'I".._ /ms I .42*,,Iaximum dry density, Jzd**.* N,Ig /m; I 7 1,Iinimum dry densitv, 7zdO.845O 532,iax'imum void ralio, e ,<>l¥,Iinimum ¥'oid ratio, e**xi**Compactionest results,Iaximum dry densi y, izd*****Optimum water conlent, T,'*, *Saturated permeabiliiy, k,,at dry densitv, Jzcii .341.21l 61l 56O.978O_646l 1400.660e_03N'Ig /m' - I _S502lom/s 7 6xlO 2 2,7xlO -' 2.2x lO6N'Ig/m; I .62 1 .47l .56(1994) and the method using capillary rise tubes can befound in Lambe (1951) and Fredlund and RahardjoeJa.1OOa.ol aI ooo I oooMat c suctian, (u_-u*,,j (kPaj(1993). The measured volumetric water content and thecorresponding matric suction for both the primary dryin_O._and pr'imary ¥¥'etting soil-water characteristic curves ¥vereFig. 3. Primar) soil-water characteristic curves of soils used in thestud) (W antl D indicate wetting and drying data, espectively)fitted using the Fredlund and Xing (1994) equation. Thecor'rection factor for the fitting equation, C(V/), was setto I as recommended by Leong and Rahardjo (1997). Thevolumetric water content data, the scanning curvesmain purpose of the curve fittinga ¥vas to obtain smoothand full-range primary drying and lvetting soil-wat.erdeveloped during the exper'iments ¥vere constructed.characteristic curves. The dry densities of the soils used inPhysical Model of' Soil Slopethe tests f'or the determination of the primary soil-1vatercharacteristic curves were controlled to be similar to thech'y densities used in the slope models.The grain size distribution curves of the soil samplesThe general arrangement of' the physical model isshown in Fig. 4. The rnain components of the physicalare sho¥vn in Fig. 2, vhile the primary drying and theprimary vetting soil-water characteristic curves areinfiltration box was 2.45 m in length, 2 m in height andpresented in Fig. 3.table, Ivhich also functions as an enclosure for a ¥vatersurnp tank ( vhich provides the rainfall and recycles itusing the ¥vater' circulation system) and a ¥vater' pump.The rainfalls vere applied through a rainfall simulatorlocated on top of the infiltration box. The intensities anddurations of the simulated rainfalls ¥vere controlled usinga magnetic flo¥vmeter, ¥vhile the amount of ¥vater flowsLabol'atory ExperimentsSoil slope models were designed and constructed in thelaboratory to study the mechanism of ¥vater flo¥v inunsaturated soil slopes. The two-layer soil slope modelsconsisted of a 20-cm thick layer of relatively fine soil(i.e., fine sand or silty sand) over a 20-cm thick relativelyicoarse soil layer (i.e., gravelly sand), and were con{structed inside an infiltration box and subjected to simulated rainfalls ¥vith varying intensities and durations.The changes in matric suction and ¥'olumetric ¥vater content at various locations along the slope model, as ¥vell as{ii{;ichanges in vater balance, ¥vere monitored continuouslyduring the experiments. From the matric suction and themodel are: an infiltr'ation box, a rainfall simulator, a¥vater circulation system and rneasuring devices. The0.4 m in ¥vidth. The infiltration box is supported by a steelfrom the model ¥vas measured using electronic weighingbalances. A detailed explanation of the apparatus andtest procedures adopted are given in Tami et al. (2004).Measuring DevicesA tensiometer-pressure transducer system and timedomain reflectometr'y (TDR) ¥vere employed to continu-ously measure the changes in matric suction and ?:TAhJI ET ALlOO2c022sc c-25 ce' 02"f.,+ee e2 ･7ce c )_ 28c :'02j:/r;i:{( j;/':,::'.iJ*l iSlity sani '_=2i!i1Tr *,2Jui 02 21 J ; 02 2S22 J022J02! a * 2S i ! 02111T 1eFrg 5. Daih., fiuctuation of tensiometer readings in sihy sand and finesand after the correction madeFig. 4. A vielv of laborator)' sct-up for the experiment (RS: rainfalsimulator, IB: infiltration box, DAS: data acqilisition s.vstem, ¥VB:colleetion tanl{ above electronic lveight balance, TDR: Irasesl.'stem and accessories, T: tensiometer body tube and pressnretransducer attac!led, FS: fine sand la .'er, GS: gravelly sand layer(magnetic fiolv meter not sho vn in photograph)volumetric ¥vater content alon*' the slope model duringthe experiments. The experimental data vere stored in aand as a result, the accuracy of the tensiometer'-transducer system used could reach 0.1 kPa.This correction was especially effective and useful in along-term experiment or in a steady-state experiment,¥vhen the change in the matric suction of the slope model¥vas not large. Without the correction, it ¥vould bedif cult to analyze the experimental data since thechanges in matric suction observed could be at similarorder to the fluctuations. Figure 5 presents a relativelypersonal computer via a data acquisition system, forsmall daily fluctuations of matric suctions from thesubsequent analyses.tensiometer-pressure transducer readings in the fine sandand the silty sand after applyin*" the correction.Tensiometer-Pressure TransducerSmall-tip tensiometers, with flexible coaxial tubing,from the Soilmoisture Equipment Corp. were used in thisstudy. The pressure transducer can measure negativeTime Domain Refiectometry (TDR)The TDR system used in this study was manufacturedby Soilmoisture Equipment Corp. The system consists ofand positive pressures (i.e., - 100 to 75 kPa) and ¥vasa step-pulse generator (i.e., namely Trase BE) that comesattached to each of the tensiometers for automaticwith a 4-megabyte memory card for data storage pur-data recording. The pressure tr'ansducers ¥vere calibratedagamst water pressure and each pressure transducerposes, a coaxial cable and three-rod standard buriable¥vave-guides ¥vith r'od dimensions of 3 mm in diameterreadin*' ¥vas rechecked or verified again prior to theand 200 mm in length. A 76-channel multiplexer en-ex periments .closure and two 16-channel TDR switchin9: boards ¥verealso used to allo¥v simultaneous measurements of volu-During a trial run prior to the experiments, it ¥vasobserved that the tensiometer-pressure transducer systemused could give almost an instantaneous response (i.e.,within one minute) to the changes in matric suction in thesandy soils and needed a maximum five minutes tomeasure matric suction in the silty sand soils. The differ-ence in response time of tensiometer-pressure transducersystem ¥¥'as due to the difference in ¥ 'ater content of thefine sand and silty sand used in the slope model at thetime of the trial run. The response time of the tensiometer-pressure transducer' system decreased as themetric ¥vater content for up to 31 ¥vave-guides.The relationship bet¥veen the dielectric constant (K*)and the volumetric water content (e,,,) of soil for thestandard buriable ¥vave-guide used was provided by theTDR's manufacturer and it ¥vas already integrated in theTrase BE. The maximum deviation of the measurement is20/0 of the volumetric water contents (Soilmoisture,1996). In this study, the accuracy of the TDR used in themeasurements was verified prior to the experiments. Thevolumetric water contents of soils measured by the TDRde*'ree of saturation of the soils increased.It ¥vas observed that the tensiometer-transducer system¥vere compared ¥vith the volumetric ¥vater contentsused exhibited daily fluctuations of up to I kPa. Themagnitude and pattern of the daily fluctuations of thetest ¥vas conducted on ail soiis used in the study over thepressure tr'ansducers' readings ¥vere similar for each datalogger. Therefore, these fluctuations could be eliminatedby using a reference transducer in each data log_ er. Thereadings of the other pressure transducers ¥¥*ere correctedbased on the readings of the reference pressure transducermeasured by. the oven-drying method. This verificationran*･e of ¥vater contents. Figure 6 presents the verificationcurve of the TDR measurement. Unlike the tensiometertransducer readin_ , the TDR reading did not exhibit dailyfluctuations.A total of 18 tensiometers ¥vas installed along 6 crosssections ¥vith 3 tensiometers located in each ro¥v. Similar-: SCANNING CURVES OF T¥¥,O SOILS101It ¥vas suspected that the lvater phase in the gr'avelly sand: K.'- iOOc')¥vas likely discontinuous due to the lo¥v ¥vater content ofQ)the gravelly sand layer (i.e., 3 to 40/0 at the initial stage of?;) 80,::experiment). Once the tensiometer lost contact with the¥vater phase in the soil, the tensiometer reading ¥vould1:'e:e)>o 60o= 40become unreliable. The relatively large size of the gravellye)sand grains and the tensiometer tip ¥vould not besand grains also contr'ibuted to the poor performance ofthe tensiometers since good contact between the *･ravelly:oo{S 20achieved. As a result, only the scannin*･ curves frorn the;relatively fine soil layer (i.e., fine sand or silty sand) ¥vereI 5>o 20 40 1 oo60Vol water content from TDR80Ieasurements (o/o)Verification of TDR measurement against oven-drying methodFig. 6.T* 4*L53il5Locahon ot scan ing curvesB (T-24: TDR-32)T44T43T4M CT-34; TDR-52)T-44:DR-72)T*34T･3BT-3eM ,T-24T-23c)T*･BT*i 4T-} 3:coOR*1 2D - 1eflne soil :ayerOR*32TQ *31:ns vmenta'Jon iD:along ro¥¥"-3 (i.e., T-,_3, T-33 and T-43), because theirlocations ¥ver'e closer to the locations of the corre:bottom, middle and top part locations of the model,respectively. The tensiometers and the TDRS used ¥verealso highlighted in bold type.# TDR , ve-guideo ensiome 8rtipAs can be seen fr'om Fig. 7, the locations of the2002 OO mmSOsponding TDRS (i.e., TDR-32, TDR-52 and TDR-72).The locations vhere the scanning cur¥'es measured arepresented in Fig. 7 as indicated by B, M and T for theTOR*S1TOR42TOR4T-14'-4 (i.e., T-24,T-34 and T44) ¥vere selected, instead of those locatedeTDR-T1c DR･72R.22roR*2Ve ic l di +t nee [o su ce (mn ):T-34 and T-44 and the volumetric water content datameasured by TDR-52 and TDR-7,_ ¥vere used, r'espectively. The tensiometers located along roRelativelycoarse soilayerTDR-Se1 50Fig.T?OeTDR･S2OR-52o*#o*#eeRelative:yavailable from the experiments.For the scanning curves located at the bottom part ofthe model, the matric suction data measured by tensiometer T-24 and the volumetric ¥vater content data measuredby TDR-32 vere used. Similarly, to construct the scanning curves located at the middle and top parts of themodel, the matric suction data measured by tensiometersDR* '2-24 TD -321 OO50 100T-34 TDR-S2 T44 TDR-7235 1 OOSO i OO7. Location of measuring devices and the points where thescanning curves lvere measured (B,middle and top parts of the model)M and Tindicate bottom,ly, a total of 14 TDR ¥vave-guides ¥vas installed along 7cross-sections vith 3 TDR ¥vave-guides located in eachtensiometers used to construct the scanning: curves arelo 'er than the locations of the corresponding TDRs.Ho vever, in terms of vertical distance to the surface ofthe slope model, the tensiometer locations are nearer tothe surface of the model compared to the cor'respondin*"TDRS Iocations. These arrangements of the locations ofthe tensiometers and the TDRS Ivere consistent for thethree sets of scanning curves analysed in this paper. Theerror that could be involved in the construction of thescanning curves due to the different locatrons of thetensiorneters and the TDRS are discussed in Erl'or illcross-section. The arrangement of the tensiometer tipsand the TDR ¥vave-guides along the slope model is sho¥vnEstilnation of Scanni/7g Curves due to the Dlfferent Loca-in Fig. 7.tions oj' Tensiometer Tips and T'DR Wave-Guides of thispaper.Constructioll of the Scanning CurvesThe matric suction and volurnetric lvater content datarecorded by the tensiometers and TDRs, r'espectively,from locations at close proximity are plotted together onthe same graph. This plot can be used to investigate thepath along the soil-¥vater characteristic curve that ¥ 'asRESULTS AND DISCUSSIONThe experimental data frorn the t¥vo infiltration testsare presented and analyzed in this paper in order to studythe characteristics of' the scanning curves for fine sandfollowed during the experiment. These paths define t.heand silty sand. The infiltration tests involved bothscanning curves for the soil-¥vater characteristic curve.adsorption (i.e., application of simulated rainfall for a**iven intensity and duration) and desorption (i.e., noapplication of simulated rainfall ¥vhile infiltrating lvater¥vas allowed to drain out from the slope model). Hence,Three sets of scanning curves frorn the experimentaldata from the bottom, middle and top parts of the slopemodel were constructed for each series of experiments.suction in the relatively coarse soil layer (i.e., gravellythe volumetric vater contents of the soils increasedduring the adsorption process and decreased during thesand) and the tensiometers gave erroneous readings.desorption process.Difficulty was encountered in measuring the matric l02ETTA *11AL .Prior to the experiment, t,he slope model ¥vas leftexposed to ambient conditions for about one ¥veek afterinfiltration test, where A and D indicate adsorption anddesorption processes, respectively. The draining processthe previous infiltration tests had ended. This ¥vas done tominimize the effect of the previous test on the current testas well as to obtain a relatively dry initial condition forthe model. Each infiltration test compr'ised of three sta*"esof Stage 111 (i.e., Stages 111-D) for the experiment on theslope model consisting of fine sand over *'ravelly. sand(i.e., the first infiltration test) ¥vas carried out for about60 hours. Ho¥vever, due to the difficulty of draining thesilty sand (i.e., the silty sand has a significantly lo¥vercoefficient permeabilit}., compared ¥vith the fine sand),Stage 111-D consisting of silty sand o¥'er gravelly sand'ith different rainfall loading being applied. In eachstage, a t¥venty-four hour simulation ¥vas conducted,starting ¥vith 5 hours of adsorption (i.e., application ofrainfall or ¥vetting process) and subsequently followed by(i.e., the second infiltration test) ¥vas continued up to 12days.i9 hours of desorption (i.e. , no rainfall applied and ¥vatervas allo¥ved to drain from the model or drainageThe underlain *'ravelly sand layer used in the slopeprocess). The average intensities of the simulated rain-model, apparently acts as a capillary break similar to thatin a capillary barr'ier system (i.e., relatively fine-grainedlayer over relatively coarse-grained layer). Under certainfalls applied during Stages I. 11 and 111 of the first infiltra-tion test ¥vere 8.1, 19.2 and 8.0mm/h, respectively.Similarly, in the second infiltration test the averagecircumstances, the relatively coarse-grained layer pre-intensities of the simulated rainfall applied were 7.8, 15.8vents do vn¥vard ¥vater movement. In the infiltration testsand 7.5 mm/h during Stages I, 11 and 111, respectively.The duration of the application of the simulated rainfallspresented in this paper, no breakthrough (i.e., penetration of vater to the relatively coarse-grained layer) vasobserved as the matric suctions and ¥vater contents of thein the second infiltration test was the same as in the fir'stgravelly sand layer remained unchan*"ed throughout theinfiltration test. Fi**ure 8 sho¥vs the intensities anddurations of the simulated rainfalls applied in the firstStage I Stsge IIS = =E: 2 +itests.Genera! Shapes of the Scanning CurvesScanning Curves of Fine SandStage illFigure 9 sho¥vs three sets of scanning curves measuredin the fine sand at locations B, M and T (see Fig. 7).The solid symbols (i.e., diamonds, circles or squares)D'l.s'S i_ 'represent the experimental data from the adsorptionprocess, ¥'hile the open symbols represent the experimen-tal data from the desorption process. The time intervallapsed tme (h)bet¥veen measurements lvas 5 minutes. The primaryFig. 8. Intensiries and dursrtioms of simulated rainfali applied in thedrying and the primary wetting soil-water characteristiccurves as obtained from independent measurements (i.e. ,first and second infiltration test seriesI40!¥ {i¥ i l-+' "' l-A I-D- er li-A Il-D;il1f;X iiI :1i ; Primacurves:> o(cr30i;iii'Ji;j :;';i; ('fiiY'1r'i I-oF(Di!i!felJ[[-A I -D¥Primary Curves:Drying}r*X ,T= ,We=t n=¥ il' PrimaryCurves} = _E5;Il1 Irioj '...¥! = ¥= X)0=/ " 'r" " ri*FItj;:_'=:p':i ･,..**+*+**''; ';;;;"* *!* 'i : ": ' ii;ii. ; ii I '- _ "i '*....l ]1l ;I ¥i i :T W, ett ingl" , l,¥i oo;= '.' .**i*=*+ ** * *(1)Drying,1 i ; ,*"- :o-+<>- l-A -Di--l-A l-D¥i ¥ i _ jll-A l[1-D, ,, vK)20>I-A -D¥"ii-A i-DC>*-¥=[Yc L!'Hi}; r'i't'lco{: - i!1-A i!1'rD--+ -¥Y' {' { YPf='-/1::# i' ;" fr_ 't # ; " ' i¥Y¥; ! =i=" s YO i 2 3 4 5 60 1 2 3 4 5 60 1 2 3 4 5 6Matric suction, (ua uw) (kPa)Matric suction, (ua uw) (kPa)Matric suction, (Ua uw) (kPaj(a) at bottom part of the model(b) at midd]e part of the model(c) at top parts of the model(location B)(location M)(location T)Fia. 9. Primar¥.' soil-water characteristic and sca:nning curves measured in the fine sand dtlring the first infiltration test series (1. II, IH indicate thestages, 11'h le A and D indicate adsorption and desorption, respectivei)) rSCAN. NINGCURVESTempe pressure cell test or capillary rise test) are alsochanges in the second stagepresented in Fi_･... 9.those in the other stages (see Fig. 9).The scanning curves follo¥ved the primary wetting soilwater characteristic curve during the adsorption processand follo¥ved the primary drying soil-¥ 'ater characteristiccurve during the desorption process (see Fig. 9). Sincethe adsorption exper'iments vere started frorn a drycondition, the scanning curve lvas initiated from theprimary drying curve. At the initial state of the experiments, the scanning curves fir'st moved from the primarydrylng cur¥'e to the primary ¥vetting curve, ho¥vever thepath did not move horizontally since both matric suctionsand volumetric ¥¥'ater contents changed. The scanningcurves then follo ved the path of the primary ¥vettingcur¥'e to some extent, depending on the intensities of thesimulated rainfall applied. It ¥vas also observed that therates of matric suction and volumetric vater contentchange decreased as the scanning cur¥'e data pointsbecarne closer to each other since the acquisition timebet¥veen two data points vas the sarne.Once the simulated rainfall ended, the scanning cur¥'esmoved back to the primary drying curve. However, thedevelopment of these drying scanning curves ¥vas slowercompared ¥vith the development of the ¥vetting scanningvere notlceably higher thanIf the scanning cur¥'es from different locations arecompared, it can be seen that those measured at locationB ha¥'e the largest matric suction and volumetric ¥¥*atercontent variations, ¥vhile those measur'ed at location Thave the smallest matric suction and volumetr'ic ¥vatercontent variations. Even though the simulated rainfall¥vas distributed uniformly over the surf'ace of the model,the difference in terms of the size of scanning curves stilloccurred since the infiltrated ¥vater flo¥ved along the finesand and accumulated at the lower part of the slopemodel, resulting in the larger changes in matric suctionsand ¥'olumetric vater content in the lower part of theslope model.Scanning Curves of Silty SandAnother thr'ee sets of scanning curves measured on thesilty sand ar'e presented in Fig. 10. The intensities anddurations of the simulated rainfall applied in theexperiments lvere similar to those applied in the experiments on the fine sand (Fig. 8). Ho vever, the data plottedin Fig. 10 ¥vere taken from measurements with a timethe drying curves. This observation indicated that theinterval of 10 minutes.Unlike the scanning curves measured for the fine sand,the scanning curves measured for the silty sand vere onlydecrease in matric suction and the increase in volurnetricin a form of horizontal paths bet¥veen the primary¥vater content occurred rapidly during the adsorption¥vetting and the primary drying soil-¥vater characteristicprocess. In contrast to the r'apid changes in matrlc suctioncurves. This happened since the volumetric ¥vater con-and volumetr'ic ¥vater content observed in the adsorptionprocess, the increase in matric suction and the decreasevolumetr'ic vater content observed during the desorptionprocess occurred gradually.The difference in the rate of development of the scan-tents of the silty sand did not chan_._"e during the t venty-cur¥'es, as the plotted data ¥vere set in a closer distance inning curves between those observed on adsorption andthose observed on desorption was related to the changesin the coefncient of perrneability of the soils. In theadsorption process, the permeability increased during thetest since the matric suction decreased and this caused arapid increase in the ¥'elocity of water flo¥v in the soil. Onthe other hand, the permeability decreased during thedesorption process since the matric suction increased andthis caused a slo¥ving down of ¥vater movement along theslope model. As a result, the changes in matric suctionoccurred gradually in the desorption process.It lvas also observed that the matric suctions and volumetric ¥vater contents in the fine sand returned to theirinitial values (i.e., prior to the application of the simulated rainfall) after 19 hours of drainage. As a result,f'our hour simulation. The scanning: curves moved f'romthe primary drying cur¥'e to the primary ¥vetting curvedurlng the application of' rainfall (i.e., adsorption process) and returned to the primary drying curve again after19 hours of drainage (s'ee Fig. 10).In order to obtain a full-100p scanning curve forthe silty sand, one additional series of unsteady-stateinfiltration tests ¥vas conducted. Prior to this additionaltest, the slope model ¥vas left under ambient condition forabout 50 days to achieve a relatively dry condltion in thesilty sand. The rainfall loadings in this test ¥vere alsoreduced (i.e., by reducing the duration of the sirnulatedrainf'all to I hour) to rnaintain a lo¥v degree of saturationof the silty sand. There were four infiltration stagesinvolved in the additional test. In the first stage, theintensity of the rainfall applied was 9.9 mm/h and followed by a 3 days draining pr'ocess. In the second, thirdand fourth stages, the intensities of the applied rainfallswere I 1.1, 10.3 and 69.0 mm/h, respectively, follo ved bydulmg the t¥venty-four hour simuiation, complete7 days of' drainage. Fi*aure 11 illustrates the prog)ram¥vetting and drying scanning curves could be obtained.The scanning curves from the first and the third stages(see Fig. 8) were alrnost the same for both adsorption andadopted in the additional series of infiltration tests.desorption, while those f'rom the second sta*･e variedFig. 12. The time interval used ¥vas 10minutes. Themore ¥videly but still exhibited the same trend. Thematric suction and volumetric ¥vat.er content data wereintensity of the simulated rainfall ¥vas higher during thesecond stage than those applied in the other t¥vo stages,taken from the readings of tensiometer T-14 andthereby producin*･ a longer path for the scannin*･ curves.The matric suction and the volumetric_103OF 'T¥¥*O SOILSvater contentThe scanning curves obtained frorn the additionalseries of unsteady-state infiltration tests are presented inTDR-12, respectively. The scanning curves at iocation T(see Fig. 7) ¥vas not available since the matric suctionsobserved in this part of the model vere beyond the range ヱ04τAM茎ET AL．一・卜A l−D一一 秘〈〉 1トA lレD 鰯く）一 鷺一｛｝ ［ll−A 擁i−D己♂40芒￡1−A l−D口1 1「一一㈱＿1、All−A ll−D lll−A l目騨D i i1−D 翻〉 ll−A・i 鰍｛｝ 目1−A聾一D【ll−D 巽i PrimaryCurves．ll −r纏馬、 lii燕iili皿oQ i PrrmaツCurves． i l 田 i I 1i i ［）rylng㊥綿ti I l l i 劇…1唱li P ξ脳輪奪li…・￡O」35ヨ＼Φ…≡…田田用N、9… ＼凝o＞＼額 30PrimaツCu四es寧騨iπ源 Dryingl l網一一We賞ini目…0 4 8 12 16 20 24 0 4 8 12 ↑6 20 24 Matricsuction，（αθ一Uw）（kPa）Ma重ricsuction，（σ∂一Uw）（kPa）（a〉at bottom partofthe modeI （bcationB〉04812162024Matricsuction，（αθ一1／w）（kPa）（b）at middle partofセhe model（c）attop Par重s ofthe modeI （locationY） （iocationM）Fig。10． Primary solレwa重er ch賢rac1eris重lc and scanning curves measured i癩the siky sand dur董ng Ihe second in行ltratio訊est series（1，II，III i鶏dic飢e Ihest段ges，whileA段ndDi鳳dica重eadsorption段nddesorption，respeαive】y）T44vsτDR42（ex甘emele負Grosssec廿on）5g o．L蔓38εε… AI103昌匙O窩 O多ε暴C琵S職］1ε1εd隊l 5c5馨卜oじr08Feb2003，09100： ←く一調トA同レD 8目d ofmeasurement24Jaa363108ぷ泊nFebざli 僧醐 一 l alc㎝d、l…農c34虫弦〔103隈繭lorIhour｝ 澱読 1アJan2003，雀6：GO：applica冒onoぎr謝ヨ！1悪…爆I驚E（掘mm加めr籍our｝マ1麗讐轡 タ戸／ ξ 、30 were not complete，since the suctlons in the middle and14Jan2003，1410αappricatめnofrainr副E（99m輪forlhour｝ 驚。哩 toP Parts ofthe slope mo（iel were also relatively hig勤after（cavitations in the tensiometer）in most of the experi−appllca勧ofra輪匪観i盤32a long Period Qf drainεしge an（i cou1（i not be measu影ed2尋Jan2003，16：30：セ S畷e董nmIr段｛io磁IestserieskPa）．Similarly，thescanuingcurvesatlocationsMandB（690mn》hfodhDロr） 1FigほL ExperlmenI段l program adoPIed in the謎ddition騒hmsteady−of measurement of the tensiometer（i．e．，greater than玉OO3iJan2QO3，萱6，Q厭言ppl…calbnDfrainlallt−配 14 17 Jan Jan 梱ン il−A li甲D P》琶 9、9 額1l i i l銅．D28 Dゆg SWCC一一We穎ng SWCCo爆Inl恒ヨl condi匠on（aRer50・d§ydrainrng） ¶0 20 30Ma願csuction，（uθガ謄）（kPa）ments． As can be seen in Fig．12，the scannlng curve startedfrom the dry重ng Primary curve slnce the model ex−perienced（1τying prior to the experiments．During theapplicatlon of tbe simロlated rainfall ln the nrst stageFig、12、Scanningcurvesfromtheresul重sofIlle段dd韮重ionaluns霊e段dy− s畷ei洲症ratloηIheseriesmeasured茎n纏1esiltysand（IJI，夏夏IJV lnd釜cateIhestages，、、・hileA鮒dDindicateadsorp芝lonand desorp重員on，resPec重iveコy）（dated14Jan），there was no s圭gnincant cむanges in bothmatric suction and volumetric wαter content．However，additionεし1series of tests （Fig． 12） were found to haveafter the simulate（i rainfal至ended，it was observed thatdi価erent shapes compare（i with the scannlng curve fromthe matric suction started to（iecrease and the volumetricthe typical innltrat呈on test．Unhke the scanning curveswater content to increase，resalting in the scann量ng curvepresente（i in Figs．9and10，where the volumetric water（ieveloping a path from the drying primary curve to thecontent decrease（i once the matric suction increased，thewett圭ng primary cur∼7e（even t｝10ugh there was no rainfallscanning curves shown in Fig．i2had a different shapeapplied）．The delay in宅he（ievelopment of the scaming（量．e。，‘humpy’shape），since the volumetr圭c water contentcurve was due to the time needed by the in且ltrating waterto登ow from the surface of the slope model to the loca−tion of the instrumentat量ons． In terms of the shape，the scanaing curves from theof the silty sand kept lncreasing alt紅ough its matricsuction started to increase．Th量s observation was sas＿pected to be due to the di登erent mechanlsms（i，e．，ad−sorption and （iesorption） experienced b》7the soil sur一温 SC'ANNING CURVES OF T¥Vo SOILSrounding tensiometer T-14 comparedl051'ith those ex-perienced by the soil surrounding TDR-1'_ (Fig. 7). Thematric suction as recorded by Tensiometer T-14 ¥vasMstric suetion eentours (kPaj :- oon our fnten!a = 0.10 kPa* max. pressvre = 0.44 kParTlin ressure = 2.ee Pa"+*;¥ .-i,FLl ･ 1 *'!*-r'--1 _1,*_4Se--e]' '/'recovered (i.e., increased) after the infiltrating ¥vaterf'rom the surface of the model flo¥ved and passed thetensiometer tip. Ho¥vever, the volumetric water contentof the soil surrounding TDR-12 stiH increased, due tolateral drainage from the upper part of the slope model.The ¥vater from lateral drainage did not pass tensiometer' 1l O1_ Oe '**-_vir"'* .e .^+'11 )/;T-14 since its location ¥vas in the extreme lef't of the slopet/ ;-'O*' ._"'r.; 1model (see Fig. 7) and the water from lateral drainagelr.../e Te lsiome er pflo¥ved to the drainage outlet at the bottom of the slopeTDR*/ave guidemodei. The volumetr'ic ¥ 'ater content measured byTDR-12 decreased a*'ain (i.e., r'ecovered) once there vasno more ¥vater fiolv from lateral drainage, and as a resultthe scannin*' curve began to follo¥v the path of theprimary drying cur've.The effect of lateral drainage as discussed above(a) st wet eondition (i e. end of Test ll･A)M trto suction oentours (kPa) :- contouf intervai * O.10 kPa* max. pressure * 2.T5 kPa- min pressure = 5 )T kPs.!'//i: :;il/･4/..* : rli_ /･ r r/.!!' ii 1.* *appears to be due to the initial dry condition of the siltysand. If the initial condition of the silty sand was relatively ¥vet (see Fig. 10), the 'hump' shape of the cur¥'e./. + "!･･1$･･i;/ " -1/i:;; : /" ;,*!'* /:; ..-.-...//'would not occur, even ¥vhen the duration of the rainfall¥vas short (e.g., I hour'). When the initial condition of thesilty sand was relatively wet, the water phase in the soilvoids vas continuous, and as a result the matric suctiondecreased once rainfall ¥vas applied. In addition, theeft ct of lateral drainage on the shape of the scanningcurves would not exist if both the tensiometer and TDR¥vere at the same location. In this case, the scanningcurves wauld be similar to those presented in Fig. 10.The same scanning curve trend ¥vas also observed in theother stages conducted in the additional series of infiltration test (Stages II, 111 and IV). It should be noted thatthe intensity of' the simulated r'ainfall applied in thefourth stage'as significantly higher than that applied inthe first three stages. Howe¥'er, the amount of ¥ 'aterinfiltrating into the model remained the same, since theadditional water from the simulated rainfall ¥vas transformed into runoff.As was mentioned earlier, the scanning curve followedthe primary lvettin*' curve of the soil-water characteristiccurve even thou*'h the simulated rainfall had ended. Thisobservation indicated that the path of the scanning curveduring the experiment did not depend on the flux bound-ary applied to the slope model (i.e., precipitation orevaporation), but on the process exhibited by the soils(i.e., adsorption or desorption). During adsorption, thescanning curve follo¥ved the primary lvetting soil-¥vatercharacteristic cur've, while during desorption, the scannin*'curve followed rhe primar'y drying soil-¥vater characteristic curve.! t･-!･-{C5*+-'1･i) +,T :/r--IF:/ ***e Tensiometer tpTDFh･/ ve 9uide(b) at dry eondihon (i e , end of Test lii-D)Fig. 13.Matric suction contours measured in the fine sandmagnitude of the errors that could be invol¥'ed in theconstruction of the scanning curves due to the differentmeasurement locations, the matric suction data werecontoured and the magnitude of the matric suctions atthe exact locations of the volumetric ¥vat.er contentmeasurements were estimated from the matric suctioncontours. Using the same technique, the magnitude of the¥'olumetric water contents at the exact location of matricsuction measurements could also be estimated by contourin*' the volumetric ¥vater content data. Holvever,since the nurnber of measurement locations of matricsuction was larger than the number of measurementlocations of volumetric vater content, the matric suctiondata were selected to be contoured r'ather than thevolurnetric water content data. The matric suction contours ¥vere created using the computer program. Surfer'RVer.6 (Golden Soft¥vare Inc., 1997).T¥vo sets of matric suction contours were created foreach soil; one r'epresented a dry condition and the otherrepresented a wet condition. The measurement data usedError in Estilnation of'Scanning Cun'es c/ue to the Dlffe/'-to construct the matric suction contours at the wetent Locations of Tensiolneter Tips and TDR Wave-condition was taken at the end of Stage II-A (indicated byGuid espoint X in Fig. 9), ¥vhile those used to construct thematric suction contours at the dry condition ¥vere takenfrom the end of Stage 111-D (indicated by point Y inThe scanning curves presented in this paper ¥vereconstructed from the matric suction and the volumetricwater content data that were measured at the same timebut at slightly difi: rent locations. In order to quantify theFig. 9). Fi_g:ure 13 presents the contours of matric suctionsmeasured in the fine sand, ¥vhile Fig. 14 presents the l 06TA N*1 IET AL.Table 2. Differeuces in matric suction data between those Ineasured b _'Mstris suetion c0 1 ours (kPa) :* oQntov int5 val = 0.01 kPathe tensiometer and those estimated from the matrie suction contours* max. pTessure * 0.22 kPa- Fnin pressure * O 5e kPah,iatric suctions (kPa)i ; s *-Q: s_ f･ 1; 1; .-=;._._*.+;:: -.F JSoilLocatiorSoiltype condition (see Fig;'/ ,".*,t. r. .* ;･ , ',._/ ;; ,_'++.･; ..(at ¥vet iu9:IF ･+Finesand,*at drying:･ TensiometertiMat c suction contQurs {kPa>- eentour interval s O,50 kP* max. pressure :; 3.54 kPa- min pressure :2S 49Tl _59l . 85B4.264.734.534,, 1 5O. I l4 404.45O.33O.080.40O 33O.40O 34O.30O 32lO.8019.6024 OOO.06O 03O.08Ml¥*lT1, ** *comoursO.65O.95Mdryintens ometero 88BaEs imatedfrom he Differenceso.81TSihysandbyBBat ¥vet ing(a) at wet eonditlon (i e , end otTest i]･A),leasuredl¥*lTTDR wave uide8)8 9118 7524.49O.160.07O 26I .89O.852 49Pa-2:. +¥ *(.1･?: ,t ; ;: :B-'2 :l_;+: *:30_..:-*-'v es:cJ : t"*+*(,,*¥*tc:o 20o:5u'c'e TensiometertipTDR w ve guideIISSl ,:' iOc(b)tdryeondition (ie end ofTestili-D)Fig. 14. Matric suction contours measured in the silty sandcontours of matric suction measured in the silty sand.The matric suction contours sho¥vn in Fi**s. 13(a), 13(b)and 14(a) have a small range bet¥veen their maximumand minimum values, indicating that the matr'ic suctiondistributions ¥vithin the slope model ¥vere relativelyuniform. However, this ¥vas not the case in Fig. 14(b),¥vhere the differences bet¥veen the maximum andminimum valuesvere quite significant. It ¥vas alsoobserved from the experimental data that the gradient inmatric suction ¥vas lar_ e in Fig. 14(b), indicatin*' that thesilty sandvas still experiencing draina*'e. In other ¥vords,the matric suctions in Fig. 14(b) were still changin_ ,ho¥vever the rate of matric suction or volumetric ¥vatercontent changes ¥vas r'elatively small.From Figs. 13 and 14, the matric suctions at thelocations of the TDR ¥vave-guides could be estimated.The matric suctions obtained from the contours (i.e.,Figs. 13 and 14) were then compared with those measuredby the tensiometers (i.e., used to create the scanningcurves). By comparing these matric suction data (asshown in Table 2), the magnitude of errors involved in.E;LuoO 5 1 O i 5 20 25 30fvleasured mairic suctions (kPajFi**. 15. Comparison of matric suctions*bet vee lmeasured andestimated data (refer to Table 2)comparison of matric suctions measured by the tensiometers and those estimated from the contours are presentedm Frg. 15. The resulting scanning curves ¥vould be in thesame region and would have the same shape as sho¥vn inFrgs. 9, 10 and 12, ¥vhen the matric suction data ¥verecorrected according to Table 2.Effect of Fine Content on Scanning CurvesFigure 16 presents the scanning curves for both finesand and silty sand measured at the middle of the slopemodel (i.e., point M). The matric suction and volumetricwater content data ¥vere obtained from tensiometer T-34and TDR-52, respectively. The infiltration tests used toobtain both scanning curves ¥vere also the same (Fig. 8).The primary drying and primary wet,ting curves of thethe matric suction data used to create the scanning curvesdue to the different locations of the tensiometer tips andsoil-¥vater characteristic curve are also sho¥vn in Fig. 16.TDR ¥vave-guides can be estimated and quantified.As can be seen from Table 2, the difference inscanning curves at the bottom and top part of the slopemodel (i.e., points T and B).magnitude of matric suction (in kPa) obtained from thedifferent methods ¥vas relatively insignlficant. Theexperiments, the changes in volumetric ¥vater contentsSimilar observations were found ¥vhen comparing theFor the matric suction ranges observed during the SCANNING CUR¥,ES OF T¥VO SOILS¥vettin_ : cur¥'es, but also rnoved along the primary- 40 '. --___;i_/ (siity s nd - W):; *'¥'_-' " _:*i¥ Scanning*-''' '*.,*rl _ ourvess:ov(1)-/;r^ ' ' ' ' ' ';t 'i::･tf/f'allprim ry wetti g curve(silty s nd -D)20c,{ ne s nd - W)E:: 10/¥¥¥ (L¥//)"'i "Prlm8ry dryjng cvrve'n'vas transferred to infiltration.Numerical methods such as the finite element or finitedifference techniques ha¥'e become a necessary tool for, primary Y/ettlng curveQ)vertingcurve during adsorption and along the primar'y dryin_( ._cur¥'e during desorption. This observation was consistentvith the ¥vater balance measurement, and there ¥vas norunoff observed in the experiment. In this case, all rain-Pfimary drylng curvel:;aJ 30107solving infiltration problems. Numerical analyses are"D")'S>usually preformed using the drying soil- vater characteristic curve, because the soil-1vater characteristic curve isO10O2aMatrie suction, {u -ut') (kPajFig, i6, Comparison of scanning curves measu ed on siltl.' sand andfine sand (from experimental data at location of point M)observed in the fine sand ¥ 'ere significant as comparedthan those observed in the silty sand. This difference ¥¥'ascommonly determined follo ving a drying process. In thecase, ¥vher'e both drying and ¥vetting soil-¥vater char'acter-istic curves are available, numerical analysis of theinfiltration process ernploys the ¥vetting soil-¥vater charac-teristic cur¥'e while the drying soil-¥vater characteristiccurve is used to sirnulate e¥'aporation.By examinin_g: the scanning curves obtained from theexperimental data presented in this paper, the use ofdue to the difi rence in the amount of free ¥vater in thesoil skeleton. Free ¥ 'ater is the soil ¥vater that can ber'emoved from the soil by applying a difference in totalhead or a hydr'aulic gradient. For a specific volume ofsoil, the amount of free ¥vater in the fine sand was largerthan that in the silty sand.drying or wetting soil-¥vater characteristic curves in theUnlike the changes in volumetric water content,desorption process, the scanning cur¥'e follo¥ved the primary drying soil-¥vater characteristic curve, regardless oflvhether the soil ¥vas subjected to precipitation or evapor'ation. Therefore, the appropr'iate hydraulic parametersof the soils (i.e., drying or wetting) should be used according to the process that the soils actually experience(i.e., desorption process or' adsorption process).lvlost of the available numerical rnethods sol¥'e thechanges in rnatric suction observed in the silty sand had alarger range compared vith those in the fine sand. Inother ¥vords, the changes in matric suction lvere moresensitive to changes in volumetric 'vater content in finegrained soils compared with those in coarse-*'rained soils,especially in the high water content/lo¥v suction regime.This is due to the fact that in the lo¥v suction re*'ime,¥vhere the soil has a hi**h volumetric vater content, thelvater phase in the soil skeleton ¥vas continuous. As amodelling of vater flo¥v in unsaturated soils can berevie¥ved. During the adsorption process, the scanningcurve follo¥ved the prirnar'y ¥vetting) soil-¥vater characteristic cur¥'e, regardless of vhether the soil was subjected toprecipitation or evaporation. Similarly, during theseepage problem in terms of pressure head, and thencalculate other necessary parameters, such as waterresult, an increase or a decrease in pressure from thecontent, flo¥v rate or' water storage, based on the pressureinfiltrating ¥vater ¥vill be transferred directly to a changehead obtained. Figure 17 illustrates the error that couldin matric suction of the soil.take place in the calculation of the volumetric lvatercontent when the drying soil-water characteristic curveFrom the abo¥'e observation, for the matric suctionran*'es observed dur'ing the experiments, it can beconcluded that a small chan*･e in the volumetric watercontent of the fine-grained soil does not mean that thematric suction does not chan*"e significantly. On the otherhand, a small change in the matric suction in the coarse-grained soil does not mean that the volumetric ¥vatercontent does not change si**nificantly.In terms of the water storage capacity of the soils, itwas observed that the longer the scanning cur¥'es formedduring infiltration, the larger the amount of ¥vater ad-sorbed by the soil. During the twenty-four hour simulation, the scanning curves of the silty sand only movedbetween the primary dryin*･ and the primary wettingcurves in an almost horizontal direction, indicating smallchan*'es in the volumetric water content of the silty sand.This observation ¥vas consistent ¥vith the water balancemeasurement, where most of the rainfall applied ¥vastransformed into runoff in the silty sand. On the otherhand, the scannin*' curves observed for fine sand did notonly move bet¥veen the primary dryin*' and the primarywas ernployed in t.he simuiation of infiltration in unsaturated soils. For the same matric suction changes (initialcondition at point O), the volumetric water' contentsmeasured using the drying soil-¥vater characteristic curve(indicated by point Q) were significantly higher comparedhvith those measured using the scanning curve (point P).The error in the calculation of the volumetric watercontent ¥vill lead to an error in the calculation of the¥vater balance.CONCLUSIONSThe scanning curves and the primary soil-¥vater char'acteristic curves of t¥vo soils (i.e., silty sand and fine sand)have been presented in this paper. It ¥vas found that thescanning curves followed the primary ¥vetting curvedurin*' the adsorption process and then f'ollowed theprimary drying curve during the desorption process.During the transition bet¥veen the t vo primary curves(i.e., dr'ying and 1¥'etting), the scanning curve had a rela- 禰108TAMI ET AL。606）Fredlund，D．G．and Xlng，A．（1994）：Equations for thesoil一、、・ater characteristlccurve，Cσ∼7、Gθo∫θch．ノ．，31（3），521−532． 7） Golden Software Inc、 （1997）： U5θ1巴∫ G∼”oFθ 、ノ10ヂ S1〃プセ1門 vθr。6，i Q界鷹の一 40鵬 旺πor incalculatior…ofoo ￥ （1988）：ApP玉ication of a s玉mple so1レwa【er bysteresis model，／α！η1θ1、vwater con皇ent弦8）Hogarth，W，Σ．，Hopmans，J、，Parlange，」．・Y、and｝｛averkamp，R． ￥volumet舜Cの駕 Golden，CO。、￥、￥ 0ゾHア4rology，98，2ま一29、99）王wata，S。，Tabuch玉，T．and、Varke距t1n，B、P，（1995）：30’1JVα∫θノ「お 20 11πθ1ηα’oη5，NewYork，Marce1Dekker，Inc．Pi殉哨、』胃隔 0εヨ10）Lambe，T．W．（1951）：So’1rε∬加g，弄oノ’￡ng加θε1写，New York，Jo自no＞ ∼V員ey and So【｝s夏鷺c．01びn）Leong，E，Change恥ma象jcsuctionC、an（i Ra｝1ardjo，H，（1997）；Revlew of soi1−waτer characteristlccurveequatio跳s，（｝θαθ‘11．Gθoθηvか017．E119’“9．，100101壌02103Matricsuction，（Ua−Uw）（kPa） ASCE，123（王2〉，1三〇6唄17．12〉Liu，Y．，Parlange，」、一Y、，Stee！出uls，T．S．and擁averkamp，R （1995）：Asoll−wate出ystereslsmodelfor負ngeredao、、’data，μ■鯉ヂFig．17， 葦deβ鷺ized pa重h of so蓋1幽waIer ch貸ra（：terist量c curve used in重he numericaisimulaIionofin61芝r謎110nprocess（dec臓sei臓m9亘rlc suαion） 1∼ε50ε〃℃ε5ノ∼ε5a7ヂch，31，2263−2266．B）Mualem，Y．（1974）：A concep田al of無ysτeresis，｝殉’θr Rε∫α’κε5 ノ∼e5α71でh，12，514−520．14）Nimmo，J．R，and Ml11er，E．班．（1986）：The temperaωre depende賢ce of1sotbermal moisture vs po【ent玉al c員aracter玉s“cs oftively Ha毛slope compared with the slope of the pr量marycurves，an（i sometimes it was almost koτizontaL solls，So〃Sc’θ刀cεSoc’θひ》11ηθ’“’cρ／0置’r〃α1，50，1105−HI3．玉5）Parlange，．1、 一Y、（1976）：Cap玉貝aryむysteresis and relationsh玉p be一 芝weendrylngandwett玉ngcurves，肋∫σ1∼θ50縦ε51∼ε∫θαrc1∼，12（2），However，the s至ope and path of the scanning curves were 224−228。found to be similar for the cases wlt熱simllar initial condi−16）Pわam，員．Q。，Fredlund，D．G．andBarbour，S．L（2003）：Apractl−tions． 1t was observed from the scanning curve of the且nesand that a small change in matτic suction can cause a ca1ぬysteresis modei for dle so11−wa乞er characteristic curve for so琵s wi由negliglble volume c目ange，Gθ01θごh11’σ∼’θ，53（2），293−298．17）Poulovassi1玉s，A．（1970）：Hysteresis of pore water 1n granular porousbodles，／α’η1α10∫So〃S‘1θ17cθ，1G9（1），5−12、signi負cant change in water content。On tぬe other hand，a18）Poulovass澁s，A、and C翻ds，E C（圭971）：丁鼓eねysteres1s of porelarge change ln the matric suction in the silty s＆nd might water＝t員e no玲一independence of doma圭ns，．10∼’η∼α10ゾSo〃S（ゴ（∼ηα∼，not change its water content signi且cantly． 112（5），30レ312、玉9）Publlc Works Department（互976）＝丁瓦e Geology of tbe Republic S1ngapore，Si鷺gapore，20）Rahardjo，H、（2000）l Ralnfalhnduced slope fa賛魏res，NSTB Rep．ACKNOWLE、DGMENT 17／6／16，scl曳ooiofclvllandstructuralEngineerlng，Nanyang The work（iescribe（i is supPorted by researc鉦9τant No． Tecぬnological Univ．，S玉ngaPo「e．RG7／99 from Nanyang Technologlcal Unlversity，S量ngapore，The貴rst author ackno、v正edges the discussion21）Si，B．C．and Kachanosk圭，R．G．（2000）＝Un玉且ed sdut玉on for in一 丘hra亘on and drainage w玉tぬ熱ysteres玉s；τheory and ae豆d tes【，5011 Sc’ε17cθ50c’θひ㌧4’ηε1ブcα／0置〃’nσ1，64，30弓5．and the advlce glven by Prof．D．G．Fredlund from t熱e22） Soilmo1sture Equ圭pment Corp、（1996）＝OPθ1’αf’η9／’15〃P∼’α’o’∼ノ101’University o郵Saskatchewan，Canada，especially at t熱e 7γθ5θβE6050κ1，Santa Barbara，CA．beginning of the study，and also t薮e research scholarshiρfrom the Nanyang Technologlcal Unlversity，Singapoτe．23） Talsma，丁．（1970）：Hysteresis 玉n two sands anc玉tbe玉adepeI｝dent domaiamode1，肋’θ1ト1∼ε5α〃℃ε51∼θ5θακ11ほ5，95−102，24）Taml，D．，Rahardjo，H．，Leong，E、C andFredlu【1d，D．G．（2004）l Apねysicalmodelforcaplliarybarriers，Gθo’θご1∼．rθ5∼．／．，27（2），REFERENCESi） 、ASTNI D2325−68，（1994）：S芭andard Test N歪etぬod for Nleas廿reme鷺t 王73−183．25）τopp，G．C．（1971）：Sollwaterhystereslsinslldoamandclayloam soils，蹄■θごθ71∼θ50μヂcθ51∼ε5θμノ・c1∼，7（4），914−920、 ofMolstureC鼓aracterlstlcCurveUsi貸gaTempeCe11，加11μα126）τoPP，G、C、and MiHer，E．E（豆966）1｝｛ysteresls moisturecharac− Booんo勇4S7ン》S∫σηぬr4∫，04．08，Soll and Rock．American Society terist玉cs and ねydraulic conductivi亘es for glass−bead 職edia， Soil for Test塗g and Maεerials（ASTM），峯》賊adelphla，Pa． Sc’θ17cθSo‘初屑’ηθノ加Pro‘．，30，三56−162．2）13raddock，R．D．，Parlange，J．7Y．andLee．，9．（2001）：Appllcation27）Vachaud，G、andnony，，L−L（1971）：擁ysteres1sduringin最kration of a so玉i water蝕ys【eresis mode蓋to simple water re監e【玉tion curves， and red1stribution in a so玉1column aτdifferen置玉aitial water content， 1二1’‘7’1，∫poヂ∼”∼Po1’oま’∫A（1（∼グiα，44，407−420。 肋’eノ’ノ∼θ50置’κθ51∼ε5θσκh，7（1），11H27、3）Brooks，R．H。aadCorey，A．L（玉964）：Hydraulicpropertiesof28）vanGe照chten，M．丁短．（1980）＝Aciosedformequat1onforpred1α一 porousmedia，∫かゴrolo＆yP叩θβ，ColoradoS職eUnlversity，Fort 玉ng t1｝e｝1ydrat王1玉c conduct圭v玉τ呈es of u【玉saturated soils，Soll S〔ゴθn（コθ Colllns，CO，1−27． Soc’θり厚11ηθr’oα／α’1’nα1，44，892−898．4） Feng， 氏4． and Fredlund， D． G． （1999）： Hystere［ic inf至uence29）Vlaene，P、，Vereecke鷺，H，，Diels，J．andFeyen，」．（1994）：Astat1stl− assocla【edwl由由ermalconduαivltysensormeasurements，Pノ呼oc． calanalysisofslxhystereslsmodelsfor撒emolstureretePtion ヵ’01η7＝hε01ッfO11∼θP辺α’ごθo∫Uη、∫硫〃’α紹ゴSo〃Mθ‘1∼θ1∼1c5，ln c員araCter玉St玉c，30〃Sc’θ7cθ，薫57，345−355． assoclation w玉th52nd Canadlan GeQtec姓nical CGnference＆30）Watson，K．K．，Reglnato，R．」、and Jackson，R．D．G9フ5）＝Soil Unsatura芝ed So註Group，Reg玉na，14：2＝14−14：2：20． wa芝e出ystereslslna員e！dso録，So’1Sぐ’θηc8Soc初屑1ηθノf‘αP1’ocθ．，5） Frediund， D． G，and Ra｝｝ardjo， ｝｛， （1993）： So’1／》8chθ’1’o∫ノio1’ U’1∫α躍1’σ’綴SoiZ∫，New York，John Wlley and Sons Inc． 39（2），242−246．
- ログイン
- タイトル
- Improvements in Nuclear-Density Cone Penetrometer for Non-Homogeneous Soils
- 著者
- M. Karthikeyan・T.-S. Tan・Mamoru Mimura・Mitsugu Yoshimura・C. P. Tee
- 出版
- soils and Foundations
- ページ
- 109〜117
- 発行
- 2007/02/15
- 文書ID
- 20984
- 内容
- SOILS AN D FOUl¥,DATIONS Vol47, No1,l09- 1 1 7,Feb2007Japanese Geotechnical Societ}IMPROVEMENTS IN NUCLEAR-DENSITY CONE PENETROMETERFOR NON-HOMOGENEOUS SOILSMUTHUSAh, Y KARTHIKEYANi), THIAhl SOON TAN'ii), MAi¥,roRU MI*¥,IURAiii), MITSUGU YosHih,1URAi+)and CHooN. PENG T E )ABSTRACTIn Singapore, the use of clays from mar'ine dredging and land-based construction activities as fill for land reclamation provides a solution to the problern of disposal ¥vhile turning such un¥vanted soils into rnaterial of economic value.A major problem ¥vith such fill is the formation of very hi**h degree of heterogeneity in the *･round. The characterization of such ground at different stages of land reclamation ¥vorks poses a major challenge as many traditional in-situtests ¥vhich provide point values are based on solutions deri¥'ed assuming the ground is a continuum. A major sitecharacterization program ¥ 'as carried out as part of a research project. The Nuclear-Density Cone Penetrometer isemployed for site investigation to measure the continuous changes in density together with other usual coneparameters. The tests have been conducted at var'ious stages of land reclamation vorks. In the present paper, theproblems faced in marine based investigations associated with the use of an existing Double Probe Nuclear-DensityCone Penetrometer are briefly discussed and this limitation has led to the development of a ne¥v Single Probe NuclearDensity Cone Penetrometer lvhich is the main focus of this paper. The wet density profiles obtained from the SingleProbe Nuclear-Density Cone Penetrometer' are compared ¥vith the double pr'obe and the comparison sholvs a verygood agreement.Kev words: land reclamation, Iumpy fill, natural radioactivity, nuclear-density cone penetrometer, vet density (IGC:C3/D3)INTRODUCTIONDred..,*Oing ¥vorks in the coastal areas and excavations inSanti Fiurban areas produce large quantities of unwanted soils inSingapore. As ther'e are no land fills in Singapore, thedisposal of such soils pose an almost intractable problembecause of' the ver'y large volume involved. The use of""*;* /"""; 1'rl/" (e 'o, :/' t /'Fio.･,･ f;i;ua/ '(':(/=_.1;/""/1';rl",_.1" '1 1:<)O:u//; ;; , 'Aj 4TS2t/7(*.j''' ; ',; :////;;f ' ': ;e j'."'Dredged Big C[ays:Lumps: .(l /' .:1" . ;. ' s .F;.."j""_*//;;(: i ,'( e.'//'/ ' f/// ' =//. .![nte r-lump voidsfilled w'th smallclay lumps andwater1. Schematic profile of reclamationlyitilcla . Iumps(af terKarthikeyan et al., 2004)with large voids bet veen them, the inter-lump voids.These inter-lump voids can be filled vith small claythat there is little information on the behavlor of thelumps, slurry and/or water, as sho¥vn in Fig. 1. A majorchallenge in this project is the characterization of suchtype of "lurnpy" fill. A revie¥v of the literature suggestslurnpy fill in the field, except surface settlements(Casa*'rande, 1949; Whitman, 1970; Hartlen and Ingers,i981; Bo et al., 2001).Visiting Scholar, Department of Civil Engineering, Nationai University of Singapore, Singapore.Associate Professor, ditto.Associate Profcssor, Disaster Prevention Research Institu e, Kyoto University, Uji, Japan (mimura * :eo ech dpri.kyoto-u,ac.jp)-General l¥,lanager, Soil and Rock Engineering Co. Ltd., Toyonaka, Japan_Surbana Internalional Consultams Pte Ltd., Singapore.The manuscript for this paper was received for revie¥v on June 8, 2006; appro¥'ed on September lO, 2006¥Vritten discussions on this paper should be submitted before September l, 2007 to the Japanese Geotechnical Society, 4-38-,-, Sengoku,Bunkyo-ku, 'Tokyo 1 1'_-OOI 1, Japan. Upon request he closing date may be extended one month.109,' "; jSeahedsite. The resulting fill is highly heterogeneous, characterized by a structural matrix formed by large lump of soils,Y.*o' G : '" " *"'/''<effective, they were dumped directly into the reclamationJ* )'/r/// : /(. i;//"i/ ;>rl//f e / e (: 7 0<:s' / i ;li :e :': "'^ ,;1( o ' / f ' '/ : ]' 'i;' '///(';);///i (/.'i'/.for land reclamation, pro¥'ides a sensible alternat.ive andiii7l,J """".g,*,',:=is no¥v implemented in the 1500 hectares Pulau Tekongreclamation project ofl' the northern eastern coast ofSingapore.For such innovative use of unwanted soils to be costi;'/'/;//z/'; ' ii. . ･such soils as fill for' Singapor'e continued growing appetiteii)' KARTHIKEYAN ET AL.llOFor a lumpy fill, retrieval of undisturbed samples isnear impossible especially at the early state ¥vhen inter-<1)- t 1lump voids are big. Most in-situ tests are based on theresponse of a continuum to a simple probe such as a conepenetr'ometer or a fiat plate (dilatometer). The existenceof a loose lumpy matr'ix with large voids makes meaning-ful interpretation of the obtained point ¥'alues verydifficult. One parameter' that can complement the usual****Fig. 2. Diagram of Nuclear-Densit) Cone Penetrometer: (a) Cableleading to data collection s .'stem, (b) Preamplifier, (c) Photomultiplicr tube, (d) Lead (Pb) sl]ield, (e) l;7cs gramma-ral.' source: Alldimensions are in milli leters (after Shibata et al., 1993)cone parameters to provide a deeper insi*･ht to the gr'oundcondition is the density of the fill.A Nuclear-Density Coue Penetrometer (ND-CP) hastional Society for Soil Mechanics and Foundationbeen sho¥vn to be able to measure reliably in-sltu ¥vetEn_g:ineerin*' (ISSMFE, 1989) for' cone penetration test-density of a soil (Shibata et al., 199'-; 1993; 1 994; Mimuraing, namely the diameter is 35.6 mm, the apex angle iset al., 1995; 1999; Mimura and Shrivastava, 1998;60', the base area is 10 cm2 and the area ratio is 0.75. AShrivastava and lvlimura, 1998). This cone penetrometerporous ceramic filter is located just behind the cone tip.The total length of the shaft housing the sensors is 258mm. After this, the shaft tapers out¥vardly at an angle of¥vill provide information of the density of a small volumearound the probe, over and above the usual coneparameters of cone resistance (q*), sleeve friction (f*) andpore pressure (u2).These researchers have focused on the use of theextensively ND-CP in naturally deposited clayey andsandy formations. Since then, this tool ¥vas used toprofile the **round in a reclamation project in Singapore,in ¥vhich the fill is formed by clay lumps and is highlyheterogeneous (Karthikeyan et al., 2001, 2004; Dasariet al., 2006). The interpretation of the results from suchNuclear-Density cone penetration test (ND-CPT) ischallenging (Karthikeyan, '-005) but ¥vhen done properly,can produce meaningful results.The existing design of the Nuclear-Density ConePenetrometer requires t¥vo probing for every single15'. The tapered portion of the shaft is 49 mm long andbeyond this, the shaft has a constant diameter of 48.6mm and extends for a total length of 896 mm. This upperpart houses the radioisotope source, the detector, and apreamplifier. The gamma ray source used in the construction of the Nuclear-Density Cone Penetrometer is theCesium (Cs!37) isotope (primary source of radiation is a3.7 MBq) ¥vhich has a half-life of 37.6 years, and thedetector is sodium iodide activated ¥vith thallium (Nal(TI)) scintillator mounted on a photomultiplier tube. Thelen*"th of the Nal scintillation detector' is 10.2 mm. Theseparation distance bet¥veen the source and the center ofthe :amma detector is 25 . mm.The ND-CPTs ¥vere performed according to thelocation; first, to obtain the background count of natu-procedure for standard piez,ocone penetration tests, asrally occurring gamma photons and then to measure thespecified by British Standard, BS 5930: 1999. During test-actual nuclear density (RI) count. The natural radioactiveing, the ND-CP was pushed into the ground at a rate ofapproximately 1-2 cm/s and cone resistance (q*), sleevefriction (f*), pore pressure (u2), RI count and back-count (background; BG) is inevitable and needs to besubtracted from the total count measured to give a countthat is better correlated to the density to be measured.The natural background count itself is also related to thesoil that is being: studied and this issue is also examined inthis paper. This requirement for two probings causes anumber of serious practical difficulties in the investigation ¥vhen the surface of the fill is belo¥v sea-level (sub-marine condition) and the tests need to be carried outfrom barges. In searchin*' a solution to these practicaldifficulties, a ne¥v Nuclear-Density Cone Penetrometer¥vas designed ¥vhich requires only a single probing. Thispaper ¥vill discuss the issues involved in this development,DESCRIPTION OF NUCLF,AR-DF.NSITY CONEPF.NF.TRATION TEST (ND-CPT)The Nuclear Density Cone Penetrometer used in thepresent study is based on the design of Shibata et ai.(1993). Fi**ure_ sho¥vs major components of the Nuclear-Density. Cone Penetrometer. The lo¥ver part of the conehouses ¥'arious sensors to measure the three typical coneparameters, namely, cone resistance (q*), sleeve friction(f*) and pore pr'essure (u2). The size of the lower partconforms to the standards recommended by the Interna-*'round (BG) count ¥vere recorded continuously. Thedetailed description and working procedure of ND-CPT¥vas reported in Shibata et al. (1993) and calibrationissues have also been discussed by Shibata et al. (1993)and Dasari et al. (2006).LAND RECLAMATION USING BIG CI,AY LUMPSAs part of the construction of the bunds surrounding:the area to be reclaimed, Iar*"e dredged clay lumps of upto about 8 m3 in volume ¥vere exca¥'ated usin9: clam-shellgrabs to form a trench for the construction of a sand key.A typical clay lump dredged from the seabed is shown inFig. 3. The physical properties of these stiff clay lumpsconsists of about 50/0 Sand, 550/0 Silt and 400/0 clay sizedparticles. These stiff clay lumps have a natural moisturecontent of 600/0, Iiquid limit of 770/0 and plastic limit of360/0 . These dredged clay lumps are placed in a bar*"e andtransported to a reclaimed site, ¥vhere the lumps aredlscharged on to the seabed up to l-2 m belo¥v the sealevel. This depth is needed to cater for the draught of thebarge dumping the lumps. Sand is then used to cap the filland to provide the surcharge to accelerate the consolida- fNUCLEAR-DENSITY CONE PENE'TRO*METERlllW!arillB Cone Penetration S stemD'mensions ofPiatfor t: 80 ftx2S ftCounter wetght =O tonDlame er of Counter weight = 3.4mContro Un't/ }iil:;!';i:::: i: s T:::j Hydraulic penetration systemReaction frame or Tawer andS;SSSS-' '-"""? S;'Frg. 3. A typical big clay lump obtained using clam-shell grab^ =isFig. 4. Photographic view' of the Marine Cone Penetration S1.'stemused in Staee 1tion. A schematic section of the reclamation site ¥vithdredged clay lumps and sand surcharge is sho¥vn in Fig. I .crawier was used to carry out the ND-CPTs.During the early stages of reclamation, there would belar_ e ¥'oids bet¥veen the big dredged clay lumps and theseinter-lump voids (void bet¥veen lumps) could be partlyfilled ¥vith small lumps, slurry and/or water. The keyproblem vith a lumpy fill is the very high degree ofheter'ogeneity due to a very porous structural matrixformed by the lumps (Karthikeyan et al., 2004). Thecharacterization of such a ground at different stages ofiand reclamation works poses a major challenge, and theND-CP has proven to be an effective tool to character'izesuch a ground (Dasari et ai., 2006).FIELD INVESTIGATION LAYOUTIn this paper, the results from one of the 3 field pilottests (TA 2) will be discussed in greater detail. The pilottest area (TA 2) is 100 m in length and 100 m in width.The clay lumps ¥vere placed directly on the seabed whichis about - 1,3 to - 14 mCD by bottom-opening barges toform an 8 m to 9 m thick lumpy fill layer from June toAu*'ust 2002. 120 numbers of marine ND-CPTs wereconducted from August to November 2002 (Stage 1).Subsequently, 7 m of sand was placed in several lifts upSITE INVES1'1GATIONto +4 mCD over a period of 10 months. Then, another120 numbers of ND-CPTs were conducted fromThe field ¥vorks to be described ¥vere carried out at theDecerrrber 2003 to March 2004 (Stage 2) with the inten-1500 hectares Pulau Tekong Reclamation project off thetion to be over the same location as in Stage I . However,northeast coast of' mainland Singapore. The projectit ¥vas impossible to ensure that the ND-CPTs werecarried out in exactly the same locations because ofbegan in 1999 and is still ongoing. Thr'ee field pilot tests(TA 1, TA 2, and TA 3) were conducted in this project.inevitable surveying setting-out errors of about d: 0.5 m.The site investigations ¥vere carried out using a Nuclear-While such a small deviation usually does not pose anyDensity Cone Penetrometer. Thus far, the state of theproblem in a site investigation, in this project, this is aproblem due to the lumpy nature of the fill.The investigation plan carried out at TA 2 for Stage 1and Sta*'e 2 is sho¥vn in Fig. 5, which consists of a smalldense grid set vvithin a big grid. The big *"rid is 99 m x 100m and the small grid is 10 m x I I m. The small dense gridis highlighted as 'A' in Fig. 5. The big grid consists of I lOlumpy fill at t¥vo different stages has been profiled. Thefirst stage is immediately after placing the dredgedmaterials in the reclamation area up to -3 mCD (metreabove chart datum; chart datum is taken as mean sealevel) and the second stage is immediately after dumpingthe capping sand, up to +4 mCD. The third stage will beat the end of consolidation, ¥vhich has not been reachedyet .In Stage l, as the surface of fill is below sea level, ND-CPTS vere performed using a Marine Cone PenetrationSystem, as sho 'n in Fig. 4. The control unit and thehydraulic po¥ver unit were placed on a barge. A hydraulicpenetration system, which was mounted on steel frame ortower, was lo¥vered on to the surface. The reaction forcewas provided by the dead lveight of the steel tower. TheND-CPTs and the small dense *'rid has 10 ND-CPTswithin a 10 m x 1 1 m ar'ea, an extremely closely spacedarrangement. This arrangement ¥vas designed to provideadequate information to characterize a representativevolume of lumpy fill and also to provide sufficient idea ofthe variation.barge is equipped with a four-point anchor mooringPROBLEMS FACED IN SUB-MARINEINVESTIGATIONsystem to secure the barge in position and to maintain itsstability during operations. In Stage 2, Iand is alreadyProblems in the sub-marine investi*･ation in Stage lcome mainly from the fact that the current desi**n of theformed above the sea level and thus a conventional CPTNuclear-Density Cone Penetr'ometer requires t.wo prob- 噸112KARTHIK狂YAN ET AL． 等 2 3 4 1： 1∼ 13 ¶4 7 5 9 10Background count（CPS）Background count（CPS） 1 0 ！00 200 30G 0 100 200 300 1 I 21 22 2ユ 2‘ 25C 27 23￠ 圏 3000t ∼5 17 ¶8 当9C 2P55 1 響 3¶ 3z 320 34 言喜0 37 33 コ9 磁c ［ 1輔m l 41 42 4コ 4‘4 4ξ 47 48 49 50警，， ，2 53点1．㊦ 1硲麺 1 引 52 53 64 1 76 77 78 75 εO 5I B2 B3 94 ε6 5ア 33 8肇 50 1ぎ 1 田c 92 閃 寺 94十雲 1桶｝ ＄1mゆ 1CI lO2 IO息 104Eε彰15・二 15ボ審αooo5’ ε5 67 53 63 70 1 1 7！C 72 73 7‘101020202525（b〉（a）30309 56 97 雪a 馨oo l ∼05 107 ｛oa lo9 110鋸釣一Drammenαay（Norway） Kinkai Bay（Japan）一Hachirougata（Japan）9曾m一Holmen Sand（No四vay） ・Vancouver Sand（Canada）一Kamigawa Sand（Japan）一Higashi Ohgishima Sand （Japan）（a）Fig，5（無）． Laぎoul of ND・CP■i臓site lnvesIig寂Ilon飢TA2（Stages lFig，6． Typic田backgrou臓d coun重pro61es obtained forhomogeηeo糊s so韮ls：（謎）ciay deposi重and（む）s段ndy depos董重s（Nobuyama，2000） and2） RI count（GPS）Background count（GPS）0o備◎則O600 800 1000 1200 50 董OO 150 20025030045一一一一RI45 −R葦111 1 F己115一一一一RI116一一Ri45−R！111 隠115一…R捌6一一RI118●働卿RI120− Rl｛18繭。。 Fご120−AveragεBG一5一5 ND−CPT 1至5 121 1−1 ，．画笥 1 ，！Qo篶ooE） 一10） 一105￡一一一“一一→o 気＿ 辱 ．ぎ器＄Ωぐ（b）』葦偽旧ρ一15・土！メ≧・∼ンFig．5（b）． De臓iled ND−CP■1段you｛郎10c謎tlon‘A少iη重he si題e invesIト一15 胤 ’ o’ 9段llon 鍾（a）一20穫1二驚（b）一20ing for every sing至e measur量ng Point，負rst to obta量n theb＆ckground count of natural rad量ation an（i then theFig。7、 Typic朗promes ob絵lned for highly heIerogeneous lumpy欄1；actual nuclear density（RI）count，so as to obtain the net （a）魏ckgroundcounωnG（わ）Rlco蝋gamma−ray count to determine the act疑al nuclear densitymeasurement．The backgroun（i count is measured using acone which contalns only a detector and no gammasource． Figure6shows the typ圭cal bεしckgroun（i count profi重esw量th（iepth obtained for a number of natura至soils．It canCPTs are very closely spaced within a 5，0m×5，5msquare grid，very s量gni負caat var量ε珪ion圭n RI and back−groun（1count pro盒星es can be observeci，a consequence oξ由e fact that the lumpy且11is highly heterogeneous，Withtむ藍s degree o￡var圭at圭on in tむe backgrQund count，the usebe seen that for these natural soils，there are里ittleHuctua−of any averaged backgrouncl count pro盒重e is likely to betions with depth．豆f the soil is homQgeneous and thevariation in the backgroun（i count prof涯e1s neghgibleproblematic．Figure7（a）s勤ows an average backgroundwithin a test site，then（ioub重e probes are notτequ呈re（i，aserrors from slight var量ation in location wiII be negligible、Figure7 s｝10ws the backgroun（i an（i RI count profilescount pronle obtainecl for the above six茎）ronles．If theaverage backgroun（i count pro釘le is use（i together withthe actual RI counts shown in Fig、7（b）to determlne thewet density，then an error o｛about10％is observe（i圭n theobtained郵or the lumpy負II slte＆t locations R互45，RI lH，estimated wet density as shown in Flg．8for locations RIRI115，RI116，RI H8and RI120，which arein the small45and RI115．To reduce the error in such a highlydense grld，s紅owll ln Fig。5．Althoug封all the six N五）一勤eteroge勲eous豆umpy盒11site，it is necessary to carry out NUCLEAR-DENSITY CONE PEN ETRO¥.,IETERoWet Oen$ity (kN/m3)Wet Density (kN/mG)12 1412 14 Ie 8 20-RI56 18 20o*- R145-Ave ge BeCLO200=oOE-oErQ(ce>o*__101 o1 ooo800600Maxir lum r dius o400io-2020O3a40Distance frorn edge of cham er (cm)1 5Filg.-20Jer ce200O1 5iTlzone s abovt23 e cmuJeoc:1 4aoc:(::aoEv1 600(1'- Average BG-o1l _9. ¥_ ,Iaximum radius of the influence zone ofment in water (a:ftcr Karthikeyan, 2005)Fig. 8. Comparison of esrimated wet densit) using actual measvredbackoround count and averaoe backcrround count400eND-CPTmeasure-Kaoiin Claycl)fO 300t¥vo probings at every single measuring point, and the t¥voprobings need to be located precisely at the sarne hole.In a sub-mar'ine investi**ation (Stage 1), it is ¥'erydifficult, time consurning and expensive to ensure that thet¥vo probes conducted at two different timings are pusheds::soO 200c:::soS OO:through exactly the same hole due to operationalCQdifficulties. In reality, the variation in the t¥vo differento100probings ranges from O. 15 m to I .5 m. The data shown inin location. This high sensitivity to location ¥vill affectseriously the accuracy of the measured density for the1 2040eO80 200 220 240 260Water Oontent ( .)Fig. 7 sho¥ ' very large variation e¥'en ¥vith small variationFrg 10. Laborator) results sholving variation in the BG count vaiuewitb various water content of soilhighly hetero*･eneous fill encountered here.Befor'e discussing the new development, at this juncture, it is important to have a better understanding of thenat.ur'al radioactivity in soils. Ther'efore, an investigationwas carried out to e¥'aluate the fact.ors infiuencin9: thenatural radioactivity (background count; BG) in soils andthis is discussed next.Therefore, a stainless steel chamber of' diameter 700mm and height 1000 mm vas used to carry out theexperiment. In the first series of tests, onl), kaolin clay¥vas used and slu 'ries of dift rent ¥vater contents ¥vereprepared. The physical properties of the kaolin claysho ved that it consists of about 870/0 clay fraction andINFLUENCE OF NATURAL RADIOACTIVITY(BACKGROUND COUNT)Radioacti¥'e elements are found naturally in air, waterand soil. There is nowhere on Earth that we cannot findnatural radioactivity. The amount of radioactivity level(background count) in soil varies greatly depending onthe soil type, mineral makeup, density of materials andits *'eoiogical history (Eisenbud, 1987). To evaluate thevariation of the background count in soil, Iaboratoryexperirnents lvere carried out using the calibration130/0 Silts. The calibration chambervas filled ¥vith slurryand the background count ¥vas measured using a dummycone, in ¥vhich only the detector is placed at the centre ofthe calibration chamber to rneasure the BG count. TheBG counts f'or clay slurries vith ¥vater content rangingfrom 1250/0 to 2,_50/0 'ere measured and the results areshovvn in Fig. 10. This figure sho vs that the BG countvalue decreases vith increasing hvater content of kaolinclay.Next, the BG counts from field tests ar'e examined.chamber. One of the controlling factors is the size of theFigure ll shows the variations in the BG count ¥ 'ith ¥vetdensity for ciayey and sandy soils. These BG counts datalaborat.ory calibration chamber. Based on the theory ofwere obtained from Nobuyama (2000), for different soilgamma scattering and neutron methods (Homilius andLorch, 1958; Olgaard, 196)) the "measurmg volume"types namely, Kinkai Bay clay, Hachirogata clay,Holmen sand, Higashi Ohgishima sand and Vancouversand. The data from Pulau Tekong and Punggol Timoraround a source ¥vas found to be about 30 cm in radius.Based on experimental results, Karthikeyan (2005)deduced that the maximum radius of the infiuence zonefor the ND-CP used in the present study is about 23 .6 cm,are obtained as part of the present research 1¥'ork. FromFig. 11(a), it can be seen that for clayey soils, the BGcount varies depending upon the physical properties andas shown in Fig. 9, and it was found that the radius ofinfluence zone decreases with increasing vet density ofits depositional history of the sediment. The BG countthe material.cps (counts per second). The intensity of' natural gammaf'or naturally deposited clayey soils varies from 30 to 7-50 ljKARTHIKEYAN ET ALll4(a);300TS5 5 jjO Kink i Bay (Japan)Hachirogata (Jap n)c/) 250OP AA Pvl uTekong (Singapore)A:o50AOo* 100toj;J!/* *(:f/108eA Single Probe Nuclear-Density Cone Penetrometer isWet Density (kNlm3)developed by modifying the double probe ¥vhere the(b)300gamma-ray section is extended so as to insert an additional detector' that is outside of t,he gamma-ray zone emittingo Ho:men sand(Norway)e Higashi Ohgishima sand (Japan)Pu!au Tekong (Singapore)(/) 250aOfrom the source. With this, the cone is able to measureboth the background and actual RI count during theA Vancouver Sand(C nada)c 200same probing, thus removing the need to do t¥vo prob-Punggol Tirnor(Sing pore)ings, a real challenge ¥vhen carryin..*,a out such characteri-150zation under sub-marine condition.+ +r ),::erig. 12. Diagram of Single Probe F i*uclear-Densit) Cone Penetrometer(AU the dimensions are in mi]limeters)IMPROVEMF,NTS IN _NUCLF,AR-DF,NSITY CONF,PF,NETROMF,TF,R:"*O=}e'eetcr*2' A5OO 50o..i fTJLSSJ;DEteet'ef'i /AA)o )^#) JCAL f(c:j" * iGa 1rtl153s $v : 200OO'+*+' 'AtaQ___"__'/T.__ )_>.:i!'o"S,_A {i'i'l"'-. -:"__.-....=..J'i"____Description of Sing!e P/'obe ND-CPc:' EnCn 'vFigure 12 sho¥ 's major components of the Single Probeo14Fi('.} sf ;155 17 18 19 2120Wet Density (kNlm3)Nuclear-Density Cone Penetrometer (ND-CP). The lo¥verpart of the ne¥v cone is similar to the old ND-CP ¥vhere ithouses various sensors to measure the usual conell. Typical variation in the BG count with vet densit) forparameters, namely, cone resistance (q*), pore pressuredifferent soils from the field studies: (a) claye)' soils and (b) sand)(u2), and the sleeve friction (f)･ The upper part of thecone section is extended so as to insert an additionalsoilsdetector to measure the naturally occurring gammaray (BG) mainly depends on the concentration ofphotons. This upper part houses the radioisotope source,radioactive minerals present in soil, such as potassium(K). As the content of the radioisotope minerals variesdependin*' upon the soil types, hence the value of BGand t¥vo detectors. Detector-1 is used to measure thecount is also different for each clayey. soils. Figure 11(a)_',_amma photons.also sho¥vs a rou zh correlation bet¥veen the backg:roundcount and ¥vet density, ¥vhich could be a useful preliminary profilln_ indicator. However, for the sandy soils, theSepa/'ation Dista/7ce betTveen Detector-1 alld 2BG count values vary ¥vithin a relatively narro¥v bandfrom 40 to 120 cps, as can be seen in Fig. 1 1(b). The BGcount for sandy soils also does not vary much with its ¥vetdensity.Clearly, the intensity of natural radioactivity (back-ground count; BG) depends on ¥vet density of soil, thusthe background count profiles are also useful to classifythe soil type ¥vhen other more conclusive information isnot available. As a general trend at the same densities, thebackground count profile is ¥ 'eak in sand as comparedwith clay and thus it can be used as a rough guide toidentify the boundary bet¥veen clay and sand strata.These results also confirm the necessity of taking intoaccount the backg round count for accurate determination of ¥vet density in characterization of a hi_ :hly heter-o*'eneous lumpy fill. To¥vards this purpose, the existin_"*,double probe ND-CP needs to be impro¥'ed to measureboth the RI count and BG count ¥vith one probin*'.actual nuclear density (RI) count and Detector-2 is usedto obtain the background count of naturally occurringIn this ne¥v de¥'elopment, the important issue is toensure that the separation distance bet¥veen the twodetectors (Detector-1 and -2) is sufficient, so that theadditional detector (Detector-'_) is able to measure thebackground count accurately ¥vithout being influenced bythe gamma-ray source that is placed in the cone. Therefore, experimental in¥'estigations were carried out todetermine the minimum separation distance neededbet¥veen the t vo detectors. T¥vo different sets of laborato-ry experiments ¥vere conducted using a stainless steelcaiibration champer of diameter 600 mm and hei**ht 2000mm. In the first set of experiments, the calibrationchamber ¥vas filled ¥vith water and the upper part of thecone ¥vith the radioisotope source and detector units ¥verekept inside at the centre of the calibration chamber. Inthe second set, experiments were conducted ¥vithout theradioisotope source unit but only the detector ¥vas keptinside at the centre of the chamber. In both experiments,the detector' is moved up vertically inside the cone shaftlvith the help of a pull-up motor and at the same tlme, thegamma counts detected were recorded continuously.Fig:ure 13 sho¥vs the results obtained for the measuredJ i¥TUCLEAR-DEl¥*SITYCONE PENETRO ,1ETER20035R p 7 5477 4 9967 p t + o 9 1 Oe p t2180O((s 140o'(N=446.vYlcr' ' "' 'f"r;･ O 8)!rx^'2c:120::oOG){3d 25160o115i5>loo'+'_(" ;oe,z; 80,oO6005,eJapan Seils-Deuble ProbeSingapore Cl y-Deuble Probeaboratory Calibration T*or Singie Probeo40e1.246822Wet Density, p t (tlm3)20O(3amma-ray200 Count300400Rate (cps)OOFlg. 14. Improved catibration chart obtained for Sin"le Prober l'uclear-Densit) Cone PenetrometerFig. 13. Reiationship between the gnnlma-ra) coilnt rate lersusdistance for ,vo 8borator) experimeutsEffecti¥'e gamma count = RI Count - 1 .0353*BG Count(1)gamma counts versus distance in the t¥vo different sets ofexperiments. This figure sho¥vs that there are significantdifferences in rneasured gamma counts for a depth ofCalibration of the Sing!e P/'obe Nuc!ear-Density Coileabout 600 mrn, clearly suggesting that the minirnurn sepa-Penetrol 1 1 eterration distance required between the tlvo detectors isabout 600 mm. Subsequently, this calibrated separationCone Penetrometer needs to be calibrated before it can bedistance is used for the design of a single probe Nuclear-Density Cone Penetrometer. Another issue that needs tobe investigated is the applicability of field calibrationThe ne¥vly developed Single Probe Nuclear-Densityused to obtain an accurate relation bet¥veen the lvetdensity to the count rate ratio. For this purpose, theNuclear-Density Cone Penetr'orneter' which is discussed incalibration chamber vas filled ¥vith ¥'ater and the ND-CPwas placed at the centre of the charnber' to measure bothRI Count and B(3* Count. Similar'ly another configurationa later section.was made ¥vith Sodium Silicate chemicals ¥vith a ¥vetchart obtained for the Double Probe to a Sing:le Probedensity of 14 kN/m3 instead of ¥vater. The ¥vet densitiesDeptll Col'rectionsBecause of the fact that diftbrent sensors and detectorsare placed at different locations along the probe, there is aof' these liquids are kno¥vn and the calibration chartsrelating the density to the count rate ratio were thenobtained. These t¥vo data are incorporated into the fieldneed to adjust the depths so as to be able to produce theparameters at the same depth. For' the Single Probe NDCP, the measurement center for the cone is considered atcalibration chart obtained for Double Probe Nuclear-the cone resistance sensor just like in the original ND-CPand then the other sensors readings are adjusted accordingly. The depth corrections for pore pressure (0.04 m),sleeve friction (O. 1 1 m) and RI Count (0.60 m) remain theratio and the ¥vet density regardless of ¥vhether the NDCP is single or double probing. Finally, the applicabilityof the calibration charts in Fig. 14 against field data isdiscussed next.Density Cone Penetrometer, as shown in Fi*･. 14. There isa unique and consistent trend bet¥1'een the count ratesame as in the original ND-CP while the BG Count dataneeds to be shifted up by 1.20 m.Detector Efficiency RatioAs described earlier, in the single probe ND-CP, twodetectors were housed in the same probe to measure boththe actual nuclear density (RI) count and the background(BG) count of naturally occur'ring garnrna photons simultaneously, ¥vhereas, in the double probe ND-C*P, the RICOMPARISON OF SINGLE AND DOUBLE PROBEND-CPTThe development of' the single probe is to overcome theneed for t¥vo probing in the same hole in a marine basedinvestigation. As a br'and new tool, its performance needsto be compar'ed against the double probe device ¥vhichhas been extensively calibrated and used to dat.e. Thecount and BG count are measured by the same detectorbut in tlvo separate probings. The counting efficiencycomparison of the double and single probe ND-CP ¥vas(numbers of counts r'ecorded per unit time) of these t¥vodetectors in the Single Probe ND-CP are not similar andremoves any ambiguity about the position and it iscarried out when land is formed above the sea level. Thisit ¥vas found that the ratio between Detector-1 andpossible to ensure that the t¥vo probings conducted atdifferent timings are pushed through exactly the sameDetector-2 is I .0353. This dift'erence in detector efficiencyhole. Out of a total of 120 tests in Stage '_, 10 testsmust be accounted for while calculating the effectivegamma count f'or the Single Probe ND-CP. The ef ectivegamma count is calculated as belo v:used for this purpose. The focations are 19C, 28C, 33C,36C, 40C, 6) C, 71C, 91C, 109C and 121C in Fig. 5. 10verenumbers of double probe ND-CPTs ¥vere conducted Fu 12-Single Probe121-DoubleProbeT1KARTHIKEYAN ET AL_l 16Wet De sity (kN/me)O12 14 16 18 20 22o24W*t Density (kN/**)W*t D*nsity (kN/m')12 14 16 18 20 2212 14 16 18 20 2212 14 16 18 20 22O24Sand F' I.E_ 10Lumpy Fill12E_ 10E_ Io'S* 12Fig. 15.Lumpy Fill141416161618181820Lumpy FiilSeabed2020SeabedSeabed(07 O1.2004)- RI 91-Doub e Probe2.2003)" 12* i2Lumpy Fi:I- RI 9 -Single Probe( 2Sand Fi lSand Fi l6E_ Io222004)488(1 5.014816222814Seabed261420Sand F'Io68'Wet Density (kNlm3)(09 02.2003)2222- RJ 71-Singie ProbeFu 28-Single Probe(09.01.2004)(09 OI 2004)(G9. 1 2.2003)(1 O.1 2.2003)Fil 28-Double ProbeComparison of wet density profiles measured b, the Double Probe ND-CPT Ivith tl]e Single Probefrom 4th December to 12th December 2003. Unfortunately, the single probe ND-CPT could not be performed immediately after completing the double probetests due to some practical problems encountered. Thethe spikes bet¥veen the single probe and double probe forthe highly hetero*'eneous lumpy fill in bet¥veen the sandand seabed. The small variation in lvet density spikes maybe attr'ibuted to the average measurement of ND-CPTproblems arose mainly because the incr'ease in the length¥vithin the measuring ¥'olume. In a ND-CPT, theof the single probe ND-CP to accommodate the additional detector led to bending: Ivhen the cone encountered adense sandy layer above the ground-¥vater table. It tookabout a month to modify the cone str'ucture. To avoidpotential damages to the nelvly modified equipment, ameasuring sphere of the radioactive source is about 23.6cm in radius, and thus the density measured refiects theaverage around the central polnt of the radioactive sourcehole ¥vas pre-drilled about 6 m from the ground level forthe remaining: ND-CPT Iocations in Stag:e 2. The loss ofinformation for the first 6 m of the sandy layer is notcritical to this study as the aim is to profile the hi_g:hlyhetero*'eneous lump"¥' fill belo v. The single probe NDCPTS usin*" the ne¥v cone lvere conducted in the same holeprofiles measured by ND-CPT to reduce statistical fluctu-from 5th .Januar'y '-004 to 15th January '-004. As this ¥vasdouble probin_ : and the uncertalnties that are involved inensurin*" that both probin*'s are along the same location,a real challen :e in a sub-marine environment. The use ofcarried out one month after the double probe tests,durlng this tnne some additronal settlement ¥vasobserved in the ne¥vly reclaimed land. As the settlement¥vas measured, these readings ¥vere used for adjusting thedepth of the measured ¥vet density profiles accordingly.The ¥vet density profiles obtained from the doubleprobe ND-CPT are compared ¥vith the sin*'1e probe NDCPT, using the same calibration chart and the resultssho¥v ¥'ery good agreement, as sho¥vn in Fig. 15. Theand detector confi_g:uration. In addition, it is also necessa-ry to carry out averaging or filtering of wet densityations. In spite of these small differences, it is clear thatthe single probe ND-CPT has performed very ¥vell inmeasurin_g the ¥vet density profiles.One of the main advantages of this ne¥vly de¥'elopedSingle Probe ND-CP is that it eliminates the need fora single probe device in a sub-marine investigation is asignificant improvement to the design of ND-CP.CONC_LUSIO l+SNuclear-Density Cone Penetrometer ¥vas extensivelyused to evaluate the early state of the lumpy fill formed byseparation distance bet¥veen the t¥vo detectors isthe dredged clay lumps. In this paper, problems faced¥vhile performing ND-CPTs in sub-marine investigation¥vere hi_ hlighted. Experiments conducted in soils tosuf icient, so that Detector-2 is able to measure theinvestigate the influence of natural radioactivity (back-background accurately. As a further result, there is a veryood agreement in the measur'ed lvet density profiles forboth the sand fill at the top and the soft clayey seabed atthe bottom. Ho¥vever, there are some small differences inground count) sho¥ved that the natural radioactivityresults from only four out of the 10 ND-C_PTS are sho¥vnin Fig:. 15 for illustration. This result also means that the(background count) of soils greatly depends on the vetdensity of soil. Thus the background count profiles arealso useful to provide a rough classification of the soil rNUCLEAR-DENSiTY CONE PENETRO iE'TERtype ¥vhen other more conclusive inforrnation is notavailable. As a general trend at the same densities, thebackgr'ound count profile is ¥veak in sand as compared¥vith clay and thus it can be used as a rough guide toidentif'y the boundary bet¥veen clay and sand strata.These findings clearly demonstrate the importance of thebackground count in the characterization of a highlyheter'ogeneous lumpy fill for accurate determination oflvet density of soils.An important contribution in this paper' is thedevelopment of a ne¥v Sin*'1e Probe Nuclear'-DensityC*one Penetrometer. This new sin*'1e probe is developedby modifying the double probe ¥vhere the gamma-raysection is extended so as to insert an additional detectorthat is outside of the gamma-ray zone emitting from thesource. With this, the cone is able to measure both thebackground and actual RI count durin*' the sarneprobing. The comparison of the wet density profilesobtained from the double pr'obe and the single probeND-CPT is conducted ¥vhen land is formed above the sealevel. The measured results from the single probeND-CPT agree very well with that from the doubleprobe. This implies that the separation distance bet¥veenthe t¥vo detectors is sufficient, so that the additionaldetector is able to measure the background count accurately. This ne¥vly developed single probe ND-CPelirninates the need for double probing and the uncertainties that ar'e involved in ensuring that both probings arealong the same location, a real challenge in a sub-marineenvironment. Commercially, this is also important especially in sub-marine measur'ement ¥vhere each test is timeconsuming. This ¥vill mean significant cost saving.ACKNOWLEDGEMENTSThe authors ¥vould like to thank Housing and Develop-ment Board, Singapore, Surbana Internationai Consultants Pte Ltd, Singapore, TOAJDN (PUT) JointVenture, Singapore and Kiso-Jiban Consultants Co.,Ltd, Singapore, for their support during site investigationand laboratory testing. The authors have benefited great-ly from the many discussions on the details of ND-CPTwith Mr. M. Nobuyama of Soil & Rock Engineering Co.LTD., Japan. The authors are also grateful to theNationai Science and Technolo*"y Board (NSTB)(Presently kno¥vn as A* STAR) of Singapore for fundingthe present research ¥vork under grant NSTB/MCE/99/003 .11T2) British Standards Instilurion (1999): Coc!e o.f Practice for Sitelllvestigations (BS 5930), Brirish Standards Insritution (BS1).London3) Casagrande, A. (1949): Soil mechanics in he design and construcrion of Logan Airport, JBos!on Societ_1' of Cil'i! E,t*"ineers, 36 (2),l 76-2054) Dasari, G. R., Karthikeyan, l¥1 , Ta, T. S., i¥,iimura, iivl. andPhoon, K_ K. (2006): In-situ evaluation of radioiso ope conepenetrometers in clays, GeotechT s!. J_, ASTlvl, 29 (1), 4553.5) Eisenbud, ivl_ (1 9S7): E,,vironinent(d Rac!ioac!iv!f_v.' F,-om N(Itura!.Industri(7! and JTfi!ilar}' Sourc"es, 'Third EdiLion. Academic Press,475 .6) Hartleu, J and Ingers, C_ (1981): Land reclamation using finegrained dredged ma erial. Proc 10fh ICSI :fFE. Stockhol n, l,145-148.7) Homilius, i, and Lorch. S_ (1958): On the theory of gamma rayscattering in boreholes. Geophysica! Prospecting. VI, 342364.S) ISSivIFF (1989): Interna ional reference est procedure for conepenetration test (CPT), Report of the ISS_,VIFE T chnica! Colnini!!ee on Penerra!ion Testing of Soi!s- TC 16, Is'ith References ro TestProcedures. S¥vedish Geotechnical Institule, Linkoping, Information, 7, 6-16.9) Kanhikeyan, lvl. (2005): Applicarion of radioisotope conepenetrometer to characterize a lumpy fill, Ph D Thesii, NarionalUniversity of' Singapore, Singapore. 219p,lO) Karthrkeyan, M., Dasari, G. R,,, 'Tan. T. S., Lam, P_ ¥!.. Loh. YH.,¥rei, Jand Mimura. N,1. (2001): C haracterization of areclaimed land si e in Sirrgapore, Proc. 3i･cl Int. Conf･ Sofi Soi!Engineering, Hong Kong, 587) 92.ll) Karthikeyan, l¥,1.. Dasari, G. R. and Tan 'T S. (2004): In-situcharacterization of land reclaimed using big clay lumps. Can.Geotech. J., 41 (2), 24,_256.12) ilvlimura, ivl. and Shrivastava, A. K. (1998): RI-Cone penetrometersexperience in naturall.v and artificiaHy deposited sand, Proc. Ist Int.Conf. Site Characterisation-ISC'98, Atlanta, 1, 575-580.13) .¥,Iimura,/1., Shrivasrava. A. K , Shibala, Tand Nobuyama. N'I(1995): Perf'ormance of RI cone penetrometers in sand deposits,Proc. Int,, S_vnlp. Cone Penetration Testin*" (CPr'95), 2, 55-60.14) ivlimura, M., Shrivastava, A. K., Shrba a, 'T. and Nobuyama, N'I.(1999): In-situ measurement of vet density and natural ¥valercontent vith RI-Cone penetrometers, Proc. 5th Int. S_1'nlp Fie!c!1' leasurenlents irl Geo,nechanics, Singapore, 559564.15) Nobuyama, lvl. (2000): The result of the RI cone penetration tests,NUS Inrerna! Report No 6004998/264, Soil and Rock Engineerin_"..C o., Japan16) Olgaard, P. L. (1965): On the theory of the neutronic method formeasuring the lvater con ent in soil. Danish Atomic Energ_1'C'oinmission Research Estab!isllrnent. Denmark, Riso Report No97 .17) Shibata, T., iMimura, ivl., Shrivastava, A. K. and Nobuyama, ivl.(1992): ¥. toisture nleasurement by neutron moisture cone penetrometer: desi**n and application, Soils anc! Foundatiolls, 32 (4), 58-67.18) Shibata, 'T., h,iimura, iM. and Shrivas ava, A. K. (1993): RI ConePenetrometer experience in marine clays in Japan, Proc 4!hCanadian Conference on A;farine Geotechnica! Engineering, 3,1 024 I 033 _19) Shibata, T , lvlimura,,1. and Shrivastava. A. K(1994): Use of RIconc penetrometer data in f'oundation engineering, P,'oc. 13thICSMFE, Ne¥v Delhi, 1, 147150.REFERENCES20) Shrivastava, A K. and h,Iimura, i¥,1. (i998): Radioisotope conepene rometers and the assessment of foundation improvement,l) Bo, M. ¥¥r., Ba¥vajee, R. and Choa, V. ('_OO1): Reclamation usingdredged materials, Proc. Int. Coilf. Port and Maritiine R & D andProc. Ist Int. Conf. Site Characterization-ISC'98, Atlauta, 1,T chno!ogy, The ivlaririme and Port Authority of Sin_ apore,21) ¥¥r}ritman, R. ¥r_ (1970): H_vdraulic fills to support structural loads,455-46 1 .60 1 606J. Soi! IV[ech. Fbunc!. Div., ASCE, 96 (SM l), '_3-47.
- ログイン
- タイトル
- Effect of Specimen Size on Unconfined Compressive Strength Properties of Natural Deposits
- 著者
- Takaharu Shogaki
- 出版
- soils and Foundations
- ページ
- 119〜129
- 発行
- 2007/02/15
- 文書ID
- 20985
- 内容
- SOILS AND FOUNDATIONSVol_47 ,No.It19- 129,F eb2007Japanese Geotechnical Socie yEFFECT OF SPECIMEN SIZE ON UNCONFINED COMPRESSIVE STRENGTHPROPERTIES OF NATURAL DEPOSITSTAKAHARU SHOGAKli)ABSTRACTIn order to use the ad¥'anta*'es of unconfined compression tests, a ne¥v testing procedure using S (or Small size)specimens (15 mm in diameter and 35 mm in height) is proposed and a ne v por'table unconfined compression tesapparatus ¥vith suction measurement is outlined. The efi ct of specimen size on unconfined compressive strengthproperties of natural deposits is discussed fr'om laboratory tests. The standard deviations of the ratios of q and E50values of' the S specimens to O (or Ordinary size) specimens (35 mm c! and 80 mm h) ¥vere in the range of 0.09 to O. 16.The 100/0 variation from the mean value refiects the hornogeneity of soils since the coefficient of variations of theundrained shear strength for the undisturbed and reconstituted soils were 80/0 to 170/0 (Matsuo and Shogaki, 1988). Inan en_ :ineer'ing sense, there ¥vas no difference in shear str'en*'th and deformation characteristics bet¥veen the S and Ospecimens for soils having plasticity indexes ranging from 10 to 370 and unconfined compressive strengths of 18 kPa to1000 kPa, that vere taken from 26 dif erent sites in the United Kin*'dom, Korea and Japan. These soils consisted ofHolocene and Pleistocene clays plus diatomaceous mudstone and highly organic soils.Kev words: clay, organic soil, specimen size, strength properties, suction, unconfined compression test (IGC: C6/D5)automatically ¥'ia electronic instruments.IN1'RODUCTIONA srnall diameter (45-mm) and a cone sampler vith at vo-chambered hydr'aulic piston have been developedThe unconfined compressive strength (q ) is ¥videlyused in Japan for stability analysis of clay foundationsunder undrained conditions. This is mainly because themean ¥'alue of q. /2 clearly describes the undrained shearand their applicability for natural Holocene andstrength on the failure surface in a specific area (Nakase,Shogaki et al., '_004a, 2004b, 2006. The effect of specimensize on the unconfined compressive strength properties isnecessary f'or the examination of strength properties of aPleistocene clays, or'ganic and sand deposits were sho¥vnby Shogaki, 1997a; Shogaki and Sakamoto, 2004;1967; Matsuo and Asaoka, 1976; Shogaki et al., 1997),and in addition to this, the testing pr'ocedure for theq -value is simple and economical. The specimen sizeusually used in Japan for unconfined compression tests(UCT) is the O (or Ordinary size) specimen, 35 mm indiarneter and 80 mm in height.The thin-walled t.ube sampler normally used in Japansample obtained from the 45-mm and cone samplers.In this paper', an outline of the portable unconfinedcompression apparatus (PUCA) for rneasuring the suction and q is shown and the eflbct of specimen size onunconfined compressive strength properties of naturalfor obtaining undisturbed soil samples is the 75-mm (JGSclay, organic and diatomaceous mudstone deposits is1221-2003) and double tube (JGS 1222-2003) samplersdiscussed based on laboratory tests.having an inner diameter of 75mm and a length of1 meter. The reasons for using O specimens in Japan arethat two specimens can be taken from a sarnple 75 mm indiameter and 100 rnm in height and the stress calculationREVIEW OF STUDIES FOR THE EFFECT OFSPECIMEN SIZE ON UNDRAINED STRENGTHPROPERTIESis easy because the cross sectional area of the specimen isabout 10 cm2. However, for O specimens, the number' ofIn the studies for the effect of specimen size on unconfined compressive stren*'th properties, Yoshinaka (1976)and Lo (1970) mentioned that the stren*'th properties ar'einfluenced by the specimen size for rock materials andspecimens is limited and their preparation for testing isdifficult due to latent cracks or homogeneity. In addition,undisturbed sampling for hard soils like Pleistocene isdifficult. Therefore, the small size specimen is better foreffective use of samples because its size facilitates stresscalculations and it is not necessary to retain the samplefissured clays respectively. Kamei and Tokida (1991)per'formed the UCT with specimen sizes of 10 mm, 20mm, 35 mm and 50 mm in diameter and 10- 100 mm insince calculations and measurements can be doneheight for reconstituted clays having plasticity indexesi] Associate Prof'essor, Narional Def nse Academy, Japan (shogakie,nda.ac,jp).The manuscrip for this paper vas received for revielv on August '-4, 2005; approved on Oc ober 2, -,006.Wrhten discussians on this paper should be submitted before September l, 2007 o lhe Japanese Geotechnicai Society 4-38-2, Sengoku,Bunkyo-ku, Tokyo 1 12-0011, Japan. Upon request the closing date may be extended one mor th.ll9 120SHOCJAKlfrom 19 to 36. They showed that there is no effect of¥specimen size on strength and deformatlon characteristicsif the ratio of specimen height to diameter' is 2.0 fordiameters greater than 20 mm. Ho¥vever the q* and secantmodulus (E50) values increase gr'eatly if the diameter is 10isplacementtransducerLoad cellmm under hlc!=2. They made the specimens by usingsmall size sampling tubes of 10mm and 20 mm in di-Perspexeylinderameter and then by a trimmer only for 35 mm and 50 mmSpecimendiameter specimens. Shogaki and Maruyama (1995)[d ISWTI Jpointed out from the test results of reconstituteddisk platePressuretransducerMatsui et al. (1994) developed a triaxial apparatususing a small size specimen, 22.5 mm in diameter and45 mm in height and discussed its applicability forS eed POtYerasxpcontrOller oundisturbed cla}.' in Osaka city. They sho¥ved fr'om theorganic and diatomaceous mudstone deposits.The S (or Smail siz,e) specimen (15 mm in diameter and35mm in height) can be used for measurin*' theundrained strength anisotropy ¥vith a different an*"le ofinclination to the vertical (Sho*'aki et al., 1997) and also200mmL,ength250mmMass70kNSpecimend l5-3Srnms zeh=3S-80rnrnLoadingspeedclay deposits that specimen size has no effect on the shearstrength. Fr'om these tests, they found that drainage timeeffect of specimen size on strength properties for the ¥viderange of strength and plasticity in various soils, includingHeightoad cel]Load'r powertriaxial compression test on Holocene and Pleistocenebecomes shorter during the consolidation process.The effect of friction bet¥veen specimen and pedestalcap on stren*"th properties diff rs by specimen size (e.g..IGS 0530-2000). Many researchers repor'ted that there isno effect of specimen size on strength properties underh/d 5 2. Ho¥vever, there are no systematic studies for theh 3smnCeramiclKa¥vasakl clay that the q and E50 values increase as thediameter decreases is caused by the problems in specimentaking, concerning Kamei and Tokida's test (1991).500-5000ki¥O 15-2 OOmm/minValead slvitcsl itchC_urrentDirector AiternatingFig. 1.La _'out of the portab e unconfined compression apparatushard soil ¥vith latent hair cracks (Shogaki, 1997b). Thevalue of q* ¥vas deter'mined to be the maximum stresscorresponding to axial str'ain of 150/0 or iess. The Eso isgiven by Eq. (1), in which 850 is the strain at the value ofq*, /2 .E50(q.l-') ( I )8<0Ko-consolidated triaxial compression (CKoUC) andextension (CA'OUE) tests (Shogaki and Nochikawa, 2004)for samples taken from the 75-mm sampler. Using the45-mm and cone samplers having an inner tube diameterof 45 mm produces a smaller specimen, which is moreadvantageous for measuring mechanical and statisticalproperties. Therefore, the strength and deformationproperties of the O and S specimens are discussed fromthe effect of specimen size in this study.PORTABl.F, IJNCONFINF.D COMPRF,SSIONAPPARATI JSThe PIJCA and its specifications for measurin_thesuction and the q values are sho¥vn in Fi_9:. 1. In thisapparatus, the load is applied by the linear head and isSOIL SAMPLES AND TEST PROCF.DURF SThe undisturbed soil samples used in this study aresho¥ 'n in Fig. 2. The 75-mm rotary double-tube sampleridentified as 75R, in accordance ¥vith the JapaneseGeotechnical Standard (JCJS 1222-2003), ¥vas usedinstead of the 75-mm sampler normally used in Japan inthe Pleistocene clay deposits of Nagoya, Izumi, Osakaand I¥vai soft clays and or*'anic soil. The 84T sampler(JGS-1223, 2003) vas used for I¥vai Pleistocene clay.The method of core samplin*' (Core) used for thediatomaceous mudstone of Nanao ¥vas double tube coresampling using water pressure for drilling to minimizesample disturbance.The lvater content (}v ), Iiquid limit (1vL), Plastic limittransmitted through an AC/DC motor. This equipment(1vp), Ip, clay composition of less than 5/Im (CC),has a hei**ht of about 20 cm and a mass of about 7 k**.effecti¥'e overburden pressure (cr(*), overconsolidatedratio (O_ CR) (defined as the ratio of preconsolidationTherefore, since the equipment is portable, it is practicalfor field use. The UC_T ¥vas performed on specimens15 -35 mm in diameter and 35 -80 mm in heig:ht at astrain rate of lo/o/min, after specimen suction ¥vasmeasured using a ceramic disk plate. The air entry valueof a ceramic disc is about ?_OO kPa. The PUCA isequipped ¥¥'ith a Perspex cylinder to measure the suctionover one atmospheric pressure and also the q** value forpressure ((7 ) to ((T(.)) and qto*"ether with samplers usedin this study are summarized in Table 1. The lp and q*values range from 10 to 370 and 18 kPa to 1000 kParespectively, ¥vhich are very wide ranges. The Holoceneclays are classified as from normally consolidated toslightly overconsolidated clays since the OCR values arein the range of 1.0 to 3.09, except for Busan Ne¥v Port 12！SPECIN｛EN SIZ薮EF罫ECT 魯・ 〆75mm蜘←s＾鐸禦灘 100㎜・難舗s・ 瓢 35㎜ 玉5㎜A sample ob｛aiぬed罫rom75−mmε匙nd75R samplers（a） 小45mm Ψ無45mm5m⇒丁s 、鼠． 点Ariake 陶o45皿m90mm ↓議s鞍F董9。2。 S巨mpEi臓g siIes45錨 Ψclay，whlch has OCR values rallging from O。79to2。20．sBusan New Port clays were disturbed under soil sampling（b） A sanlple obtained frQm45−mm samplers（Shogaki et aL，2005a）．T｝1e OCR values of Pleistoceneclayラhighly orgaRic soil and diatomaceous mudstoneFig，3。 Location of specimens for a samp亘eraugefromLO玉to78．1andclassinedasfromnormallyconsolidated to heavily overconso1呈（iate（l clays． becomes constan芒，can be measured qulckly when芒he piezometer me＆surement iadicates a similar value to Figure3shows the location of specimens，for sanユPles75mm in diameter and100mm iH height and45mm indiameter and180mm in height，from the samplillgξubeof重he75−mm an（175R samp茎ers and45−mm sampler、Six 重he expecξed specimen suctio【1．2）asshownlnFig．3．Shogakie亡al．（i995α）shows重hatthe However，the possibi至ity exis重s重hat suction greater than that of the p圭ezometer measurement cannot beS specimens and one O specimen can be obtalned fromthe samples of亡he75−mm and75R samplers alld eight Sspecimens and one O specimen from重he45−mm sampler， accurately me＆suIled if all air ls not removed from由e pressure transducer pipe．3） If the alr iIUhe pressul』e transducer pipe is removedstrength and deformation properties of ten S specimens and the piezome重er seusitivity is hlgh，the measuredobtained from a sample75mm in diameter and45mm in So va茎ues are unrelated whell the spec三men is put onheight＆re similar in an engineering sense．The specimen the ceramic disc plate to get piezometer measure．site，as shown in Fig。3，is not hlnuenced by the samp正edistul−bance caused by tube penetration an〔i fr玉ctionbetweell soil and tube during sample extruslon。This wascon倉rmed by using a Scannlng Electron Microscope（Shogaki and Matsuo，1985）and a color laser three（iimensioual pro負le microscope（Shogakl，2006a）．Eachspecimen was she＆red at1％／min after suctioll measure− ments．4） However，the time in which suction becomes constant is less when the suction drops from a王arger value to specimen suction．The maximum time for measuring suction w＆s six For the e貸ec重of measuring suc重ion before＆ndminutes．after shear on strength and deforma重ion propertles o郵ment uslng PUCA ln accordance with the Japa！1esespecimens，lt was con貸rmed by Shogaki et aL（1995b）Industrial Standar〔l for unconfined compression tests oεt紅at there∼vas no efモect for natur＆1deposits．Namely，thesoils（皿SA12164993）． The procedure for measuring由e suction is simiiar todecreasesinwatel’contentofspecimensduringsuctionthat reported in other Iiterature（Shogaki etε迄L，1995blconsidered tha重t難is smal至cbange il1∼vater content doesShogaki and Maruyama，1998）．It is important that themeasurement and shear were less than I％．It wasnot affect the strengthεmd deformation properties．suction be measured quickly重o mlnimize stress cQnditio亘changes，whichdirectlya登ecttheundrainedshearstrength＆nd secan嘘modulus values。The specimen suc−EFFECT OF SPECIMEN SIZE ON SUCTION，based on亡he author’s expe11iα1ce，as foliows：RELATIONSHIP BETWEEN STRESS AND STRAINAND EFFECTIVE STRESS PATHS1） The suction（So）of＆specimen，in which the suction Figures 4（a），（b），（c），（d），（e），（f） and （9） show thetlon was measured using a larger piezometer point value， JSHOGAKIi22Table 1.Geotechnicaproperties of soil samp]es used in this studl_C_ (kPa)* a( (kPa)q(o/o)lp C_OC_RSamplerIt'n It'L Tt*pNo. Site(O/o) (O/o) (o/o)(Holocene)1 Shizunai5062291 36209S93 Urayasu81 - 85i04 - 1 144 Kalvata4836) 65 Tokyo4649327_ Hachiro :a a6 Kalvasakil05 - 108l 13 - 120444933 41 29_)l 50 6 1 36l .20l 07l .2360 - 65 50 - 5)_ 232 - 45710 15 77l 7 _, I , 245, 51, 23 - I .19 12/l952. I O-7759l08 - 320464864 - 73 47 - 54 160 - 223l OO - l.08 66 - 189333638-41 16-26195-211l .06 - ?_ 02 100 - 1977 = Yokohama57-61738 Hekinan60 - 9374 - 10731 -3845-7225-43 6-124O 99 - I .37_ 60 - 14534 - 7151 - 952538'-6-57 i 3-30 99-7_051 , 1 7 - 2.94 92 - 2204759 - 10526 - 4133 - 69 30 - 54 191 - 241l .O_7 - I .36 130 - 138 75-mm96 - 107293459-71 3'_-42 = 51-92l.OI - l 12 23 - 778,_ - 150294819-lO)_ 36-42 =l.05 - 3.09 : 15 -27390 - 1 154447469 Ku¥vanaIO Amagasakil I Ashiya6812 j Tokuyama8968 - 1301 3 AFiakel 2014 Kahoku a a16 Kimhae (Kr)4613850883460803050441 026653 - 70I 8 Yangsan (Kr)l 9 I ,f ai64 395798 - 10939(Kr)68 5581 7415 Bothkennar (UK)17 Busan Ne v Por7)7464358592577560 - 86l .26135l .9612131 35)_6 - 40 30 - 35 95 - 154l 02-1_51 = 91 -l072832 - 54 36 - 60 59 - 175O 79 - 2.20 48 - 1296167 - I 18l .03 - I 13 26-323,34) 733446586l 03S434-74 = 34-63 18-23l .OI - 2.04 16 - 20(Pleis ocene clav)20Nagoya34 - 73 63 - 78 -75 - 4033 - 47 8 - 26 1 95 - ,_412.44 - 4^2521lzumi28 - 60 49 - 96 2_, - 2827-6S 5-28 = 8-1364^5 - 78. 1 347 - 578, 2Osaka (Bay area)23Osaka (h,Ial2: Inland area)63 -73 75 - I 18 31 -444424Ilvai74-83 = 101-lll 41-5158-7440 60274S3378 3966 32473034640-66 66-681 1658 - 76275R44 21.832.08 362-585 45-mm. Cone1 ,,OI - I ^90 25 - 3584T(Highl¥.' organic soil)25 I¥vai393-592 380-655 : 164 )8)l 99 - 37023 - 35 14 - 15 8.03 - 1 1 42 25 33 75-mm(Diatomaceous mudstone)26 * Nanao87 - 187 143915,1 3542 =22.32335 - 1070 C_ore*: C_lay composition of less than 5 l!mresults of the suction measurement for Bothkennar,Kimhae, Busan Ne¥v Port, Yangsan, Hachirogata, I¥vaiorganic and Holocene clays respectively. . These specimens¥vere put on the ceramic disc plate when the piezometerpoint indicated about 80 kPa, dependent on type of soiltested. The time, in ¥vhich the specimen suction becameconstant, varied slightly for each specimen and this timewas independent of specimen siz,e. The suction valuedecreased ¥vith sample disturbance (Shogaki, 1995). Theeffect of specimen trimming on suction is unrelated tospecimen size since the So Values of both specimen sizesare similar, as sho vn in Fig. 4. The suction values of 1¥vaiorganic and Holocene clays, as sho¥vn in Figs. 4(f) and(g) respectively, are as small as 3 -5 kPa since the (T(values are as small as 14 -23 kPa.Figures 5(a), (b), (c), (d), (e), (f) and (g) sho¥v therelationships between the pore water pressure measuredat the base of the specimen, the axial stress and the axialstrain (8*) for the same specimen, as shown in Fi**. 4. Thesuction under shear is represented as the pore ¥vaterpressure (u) in Fig. 5 since the suction under shearbecomes zero to plus for an O_ specimen and a small So¥'alue for the S specimens. Therefore, the u Values at thee*=00/0 are So values. The w , q , E50 and axial strain at 123SPECIN{EN SIZE EFFECTooIlc ]Bothkenuar20C,¥60'[4 1 . 8]CIiO[39 8]+ o specimen:;Cl)V)1 _ 3 4 6,40Hachirogata[ l: Suction (kPa)60O:;A S2 specimeno[lO.3 jiSi[ l:Suction (kPa) o S specirnen80[8.412037.9]¥40Oc ;o o specimeno SI specimen805Time, t (min)o(a) Bothkennar cla)'o1 Time,2 3t (min)456(e) Hachiroga a da)'[1)1 6] ¥ [30.0]c t 20c(o40ioc20c/c,o40S0=(3'4 5.4)kPa[31.5] [ l:Suction(kPa). 60+ o specimeno Slspecimeno:sKirnhae A S2 specimen(') 80o+0' Sl ' S4^ S, ' S5o 601 _ D 4 5 6' S(/) 80,Time, t (min).o(b) Kimhae cla}'･ S6lwai (Organic)1 _ 3 4,56Time, t (min)(f) Iwai organic soilBusan New Portc:;cloo:$C/o37^91l/50[47.7]100c:$CCO+05:O 60A S2 specimenoS0=(3'O-4.9)kPal 40[41 3]+ o spesimeno Slspecimen[ l: Suctron (kPa)20:o_,o Sl a S3A S2 ' S480C,D7lwai (Holocene clay)100Time, t (min)o(c) Busan New Port da)'- !).7I'ime, t (min)56(g) I vai (Holocene da)')lce 1/ [22.6]20Fig. 4.Relationships betlveen suction anti time' 4¥J40Cl)iO[24.2Yangsanfailure values of each specimen are also given in Fig. 5.The q60[ l: Suction (kPa),O 80:$Cl)100o+ o specimeno S specimen1 2 Time,3 4t (min)5 6 7(d) Yangsan d*yand E50 values and the relationships bet¥veenstress and axial strain for each soil are almost the same,unrelated to specimen size. However', pore water pressureunder shearing differs by specimen size, namely the porelvater pressure of O specimens changed from minus to8plus under an axial strain of from 0.50/0 to lo/o beforemaximum axial stress and the amount of change of porewater pressure was greater than that of S specimens. Asdescribed in the previous chapter, the strain rate of bothspecimens ¥vas lo/o/min. The pore water pressure valuesmeasured at the specimen bottom are smaller than thosearound the shear band and caused by the delayed SHOGAKI1_ 4100'Ce*1 OOb, ,bSlmbol.Cl50Cl): S ecimenkPa)olo):SCl)ooE *oq*T'* n*50t-( MP a)(o/o)Scl)Ol60l7 9 15 559I 0.0 12 g2733S.s927 2 13 534O20Q)h::51:5v)(,)c,)e,l^ c1'o(L)/c9 -4vonL1)v+e :Oaf)¥d'AAAA-20,,13 5-40)e)O-40hoBothkennaroCL2 4 6 8 10olOO80¥J60eb_ 60c:;k) 40S mbol. * i S ecimen40'D )'Cl)t$' no20*slS2O1)')cl)(,DF soq(qt)kPa)70656476 574 l76 2CMPa)e'(" )42 4135 3639 6Gf)20Svmbol. $*: S ec imeD$oe; 1020s15a(o/o)(c) Busan Ne v Port cla}'(a) Bothkennar cla)*lCe105Axial strain,Axial Strain, 6a (o/o)q*Es )Sre/elkPa)(Oloo65(MPa)54 o, 5s6653 o33530$$w alhsoorOc8uo)1cs vn,eh '{e) / lO4q)¥l* sec:lN -20Q,e)oKimhaeo -AnvCL-20-3 oOo510Yangsanc155lOAxial Strain, g a (o/o)15Axial strain, aa (o/o)(d) Yangsan da)'(b) Kimhae cla}'mi**ration of pore water pr'essure, as shown in Fig. 6. Thealmost similar for the O and S specimens. However, thereundrained condition under' shear for both specimen sizesis a large difference in the effecti¥'e stress paths bet¥veenwas sufficient since the decrease of ¥vater content ¥vas lessthe O and S specimens of Bothkennar, Kimhae, Yangsanthan lo/o by calculating specimen ¥veight before and aftershear for both sizes. For' I¥vai organic soil and soft claydeposits, the effective stress paths of UCT using S speci-and I¥vai Holocene clays ¥vhich is caused by the delayedmens are consistent ¥vith those of the CKoUC except thecontent are as high as 150-3700/0 and 136-59,_o/odifference in the initial stress condition (Shogaki, 2006b).respectively and the qTherefore, the UCT ¥vith suction measurement using Sspecimens is suitable for the measurement of effectiveHachirogata clay had many diatoms and the samplesmigration of ¥vater' content. In Hachlro*'ata clay and I¥vaiorganic soil, the plasticity index and natural ¥vatervalue is as small as '-5 -33 kPa.¥vere saturated by ¥vater (Tanaka and Locat, 1998) andstress paths under undrained conditions.The effecti¥'e stress paths concerning Fig. 5 are sho vnin Fig 7. From the relationships bet¥veen axial stress andI¥vai or_9:anic soil had a hi*･h ¥vater content of 3700/0. Theaxial strain, as sho¥vn in Fig. 5, the deviation stresses arecan be ignored.delayed migration of pore ¥vater pressure forHachirogata clay and l¥vai organic soil is so minor that it Ti25SPECll¥,lEiN SIZE EFFECT30c30c tC20{-b 20bcl O lOc o 10:S%: Svnlbolc')$$: S eaimenwnaeolo)OoSoq,133133q*kPa22 925 5Cl:E soMPa)3030Cf(0/5437oq)h:5 O:5 O(,/?')ODof_ cee)1c ce, ; -5*ce: , -5'*ceoe'o -lOe*o -lOHaehirogatao510e*15o5lOAxial Strain, 8a (o/o)Axial Strain, 6a (o/o)(e) Hachirogata cla)'( fi)Fig. 5.15I¥vai (Holocene cla}')RelationshiPs between u, a ancl 8*40c s30Loadbe 20c')lc'10larger u.1..OMigration of u""""'¥V""""'a'I:' 5E,)smaller uu)),^ce-}'-'4 OPressuretransduceree sCeramic disca)oe 5Fig. 6.o105Axial Strain, Ca (o/o)Concept on migration of pore water pressure under shear15against lp and q(f) 1lvai organic soilThe relationship between axial stress and axial strainfor Osaka and lwai Pleistocene clays is sho¥vn in Figs. 8(a) and (b). The UCT usin*" S specimens is applicablein Figs. 9 and 10 respectively. The ratios(REso) of E50 Values are also sho¥vn in Figs. 11 and 12.The plot symbols are classified for Bothkennar, Kimhae,Busan Ne¥v Port and Yan*'san clays in order to distinguish f'rom Osaka Mal2, I¥vai Holocene and Pleistoceneclays and or_ :anic soil and other Japanese Holocene andunder JIS A1212-1993, as well as the triaxial test using SPleistocene clays and diatomaceous mudstone. The Rq*specimens (Shogaki and Nochikawa, 2004) since therelationship between axial stress and axial strain isvalues ar'e in the range of 0.91 to 1.25, unrelated to thelp = 10 - 370 and q = 18 - 1000 kPa values, and the meanunrelated to soils, as sho¥vn in Figs. 5 and 8.value is I .02. The RE50 values are also in the range of 0.77to I .24 and the mean value is 0.99. The q** and E50 Valuesobtained from the O and S specimens are almost similar,unrelated to t¥venty-six different sites in the UnitedEFFECT OF SPECIMEN SIZE ON q. AND EsoVALUES. '_Km*'dom, Korea and Japan and also Holocene andvaluesPleistocene clays, organic soils and diatornaceousof S specimens to those of O specimens are plottedmudstone. Ho vever, the RE50 of I¥vai organic soils ¥ver'eThe ratios (Rq ) of the mean value (q.(s)) of q SHOGAKIl 26201 OOBothkennar80rHachirogatafScclc')60ce C40hceS:: :vO*'S'c') QlOje'C20O-(ce+ o specimen.o S specimenA S specimeno+ o specimeno s specimeno20 40 60 80 1 OOoEffective stress, q,,/2 - u (kPa)O lO(a) Bothkennar da)'C*20Kimhae50･ ') e40u)lwai (Organic)_101 30(5Ce¥20+0o Sl-c+ o specimenq)o sl specimenA S2 specimen10Oee.->a)ovA S2a s3i6020oeeS4s5s6O 5151020EffectiVe stress, 0/2 - u (kP a)Effective stress, d2 - u (kPa)(f) hvai organic soil(b) Kimhae cla)*8020+" 60os",AO specimenlwai (Holocene clay)Busan New PortSl specimenS2 specimencle'_ce-c')s - 40$::o 10-(::;c¥'ee- 20o30(e) Hachirogata clay60l20Effective stress, d2 - u (kPa)>e)o4060;+ OoAOoSl DS2 vS3s4' , -l (O )20Effective stress d2 u kPaEffective stress, d2 - u (kPa)(c.) Busan Ne v Port clay(_ ,*) hvai (Holocene cla)')40cFig. 7. The effective stress pathsYangsan_ 30s^ceu)s:'in the range of 0.67 to 0.91 and the mean value vas 0.76.This is caused by soil homogeneity, as shown in Fig. 5(f).Namely, the q and E50 values of the O, Sl and S6 speci-ono 4v-cce lS.Cq) 10o+ o specimeno s specimeno1 O 20 3 O 40 50 60Effective stress, d2 - u (kPa)(d) Yangsan claymens under similar w* values are similar. The UCT testfor hi**hly or*'anic soils is very difficult since theundrained condition under shear cannot always be confirmed. However, it ¥vas judged from the effective stressbehavior for the UCT and Ko consolidated-undrainedtriaxial compression tests (Shogaki et al., 2004b) that theUCT test for I¥vai organic soils could be accuratelyperf ormed.It ¥¥'as shown in Figs. 9 to 12 that the qand E50 Valuesobtained from O and S specimens are unrelated to sampling sites and various soils. Based on this fact, Figs. 13 TSPECllvIEN SIZE EFFECT127Osaka Mal 2600llcO1' eF ¥ql 400k),D$)200+ooA'S;'sls3oo12AS cimenquwn･$4+q8: S bo , *:fcnEsosfolekPaMPao/e6868542.643,2539.043.36966524.937 8534.038.2o1O2118;23223Axial Strain, 6a (olo)50806(a) Osaka Pleistocene (iMal2) clay50 200 600 1000(kPa)lOO150Unconfmed compressive strength, qF'io. 10.Relationships bet,veen Rqand qulwai (Pleistocene clay)400'c:S¥/ 30014b1" Smbo,,*+ooAslDvs3(1c' onne) 4vvC'l OO2 4oOS2s4**: S cilnenEsOq*wnookPaa23 7360 29385848984ef:: Io/o378 4312 4351 l22 9202519 62.19.6303 1 1.221.32.26 8102Ocl I .O.¥vlQl O,oAxial strain, 6a (olo)06(b) I¥vai Pieis ocene cla)'Fig. 8.Relationships betlveen er and e2300500Plasticity index, Ip (o/o)Fio, Il.Re!ationships betlveen RE_.-o and lpFigs. 9 to 12 are the mean ¥'alue for several specirnens.1 .4The mean values of the Rq and RE50 Values using thesespecimens ¥vere similar to those of Figs. 13 and 14. Themean vaiues of the Rq and RE50 are in the range of 0.99e< I ,2to I .03, unrelated to Holocene and Pleistocene clays. Thestandard deviations (s) of Rq* and RE50 are in the rangeof 0.09 to 0.16. The 100/0 ¥'ariation from the mean valueO_:20 40 60 go loo1,0.Cl)reflects the soil homogeneity since the coefficient of:variations of the undrained shear strength for theundistur'bed and reconstituted soils, excluding soilO,8o.6'_O 40 60 80 iOO 300 500Plasticity index, Ip (o/o)strength, stiffness and sampling methods, ¥vere 8- 17010(Matsuo and Shogaki, 1988). Therefore, the strength anddeformation properties of the O and S specimens aresimilar for undisturbed clay and organic soil deposits andFig. 9.Relationships betlveen Rqand Idiatomaceous mudstone ha¥'ing plasticity indexes from10 to 370 and the unconfined compressive strengths are1 8 - 1000 kPa. The undrained strength propertiesand 14 show the histograms and their norrnal distributioncurves for the Rq and RE50 for Holocene and Pleistoceneclays respecti¥'ely. The number (n) of S specimens inFigs. 13 and 14 are 93 for Holocene and 37 forPleistocene clays for specimens having similar wet densities and wvalues since the q*(s) and E50(s) for each plot inbetween the ordinary and small specimens are also similarsince the effects of specimen proportions on the strengthproperties are similar.The unconfined compression test using the S specimenwith suction measurement is better for effective use ofsamples and measuring strength properties and determin- SHOGAKI1_･860o Bothkeru,arA Osaka la 2o Hoioceneclay D KisT'haec hYai (H)A pjeistocene elay a Busan ¥. 'ew Port A Iwai (P)A Diatomaceous mudstonehYai {O)a YangsanPleistocene clayRq*50l .4RE'¥' 40Mean value ofRE O * O.99cn37oMeanal .020.090.990,lOa' Standard deviationLr)oC: 1.'O1rlr)e)h_" 30VecPA Ab--J -Ar-A--c-AA ,X- o. -9Ao:O ) o1 O6-- i< ec Do'¥lOoc')or ) O_8q,:'cr fl' ."AAOAl.5 0.5O.50.6lOO 150 200 600 100050oUnconfined compressive strength, qFio. 12.Relationships bet veen RESO and q*nHolocene clayRqRE50)K.' 4093Mean0.lOl 020.1630that ¥vere taken from 26 different sites in the UnitedKingdom, Korea and Japan. These soils consisted ofHolocene and Pleistocene clays plus diatomaceousmudstone and highly organic soils.ACKNOWLEDC.F,MENTThe author wishes to express his sincere *'ratitude toMr. Yoshikazu Maruyama, Syuji Shirakawa and Ryos)Sakamato, ¥vho ¥vereDefense Academy, forworks and also to thethe Port and Airports)c･* 20lOO0.5RquFig. 13.The statisticai properties of Rq* and RESO (Pleistocene clay)al .03(T Standard deviation0:l.5(kPa)6050Fig. 14.1RE50Rqul.5 O.5l.5RE50The statistica properties of Rq and RE<0 (Hotoceue cla)')graduate students of the Nationaltheir cooperation in experimentalGeotechnical Survey L,aboratory ofResearch Institute for the use oftheir Bothkennar and Yangsan clay samples in hisresearch.NOTATIONCC: clay composition of less than 5 !!ming statistical properties.E50: secant moduluslp: Plasticity indexOCR: oveFconsolidated ratios defined as the ratro of effectl eCONCLUSIONSThe conclusions obtained f'rom this test are summarized as follo¥vs:1) The unconfined compression test using S (or Smallsize) specimens of 15 mm in diameter and 35 mm inheight ¥¥'ith suction measurement is better for measuring strength properties and determining statisticalpro perties.2) The standard deviations of the ratios of q and E50values of the S specimens to O (or Ordinary size)specimens (d35 mm and /780 mm) ¥vere in the rangeof 0.09 to 0.16. The 100/0 variation from the meanvalue reflects the soil homogeneity since thecoefficlents of variations of the undrained shearstrength for the undisturbed and reconstituted soils¥vere 8 - 170/0 (Matsuo and Shogaki, 1988).3) In an engineering sense, there ¥vas no difference inoverburden pressure (a( ) to preconsolidation pressure ((T;)q : unconfined compressive stren_ thSo: specirnen sucrion before shearu: pore ¥vater pressureIt'L: Iiquid limitst' : natural ¥vater contentT4'p: Plasticity limit8*: axial strainef: stFain at failurecr: axial stress(T(*: effective o¥'erburden pressureREFF,RF,NCF,S1) Japanese CJeotechnical Societ¥.' (2000): Preparation ofSpecinlens ofCo(?rse Gramdar Materials for Tria_1'ia/ rest. JGS 0530-2000,454-46,_ (in Japanese).2) Japanese Geotechnical Society (2005): The method for obtainingsoil samples using a thin-¥valled sampler ¥vith fixed piston, JGS12_,1-2003. Standards of Japanese Geo,ecJlnica! Society forbet¥veen the S specimens and O specimens from soilsObtaiiling Soil Sanlp!es -Srandarc!s arld E_rp!anations- ( Eng!is/7version), 1-9.3) Japanese Geotechnical Society (2005): The method for obtainin_"..soil samples using rotary double-tube sampler (JGS 12,_,_-2003),ha¥'ing plasticity indexes rangin*" from 10 to 370 andStandards of Japanese Geotechnia7! Societ.v for Obraining Soi!unconfined compressive stren*'ths of 18 - 1000 kPaSanlp!es -Sta/7dards anc! E. p!anations- ( Eng!ish versi0,7), I O- 14.shear strength and deformation characteristics 可SPEC獄1EN SIZE EFFECτ4） Iapanese Geo［echnical Society （2005）：τ麺e metむod for obtaining三29 samplers，（｝θo∼εchnicα1Si∫θC1∼α’｝ααθ舵α”o’∼，Atlanζa，419−424、 so㍊samplesusingrotar｝’trlple−mbesampler，／G51223−2003，19） S｝10gaki，丁．andで〉latsuo，茜1，（玉985）：Factor analysis apProac酒to 5fαηゴα1噌450ゾ／αμznθ∫εGθo∼εc1∼’1iごα！Soご’（∼ぴ∫io1『0δ’α’∼∼iπg So〃 賦consoildated undralned sbear strength oll clay wi由 some Sα〃∼με5−S∼αn面酪α1∼4疎P’αノ∼副0135一（だ∼∼9”5hソθ老5’oη），15−2L co…1sideration on m王croscopic struc【ures，Pro（フ．Sy〃2ρ．Sα〃∼ρ1”∼9，5）Japanese Sこandard Associatlon（1993）：Me由od flor uacon負ned 三〇9−116（in∫apanese）、 compressionζests，／1S〆1／2／6−1993，王一王1（in Japanese）、20） Shogaki， T．， ｝vloro， ｝｛． and Kogure， K、 （1995a）： Stat玉sこ呈cal6）Kamei，T、andτokida，M．（1991）II浦uenceofspecimensizeon properしies of so員da【a with111乳hin一、va11ed sa荘1plers，P∼oc、5rh∫n∼、 題ncon負ned compressivestreng家h and deformation cむaracζer玉stics of C喚1∼o’■θ‘η∼oF po1αノ’」薮1∼9．Co1∼∫，406−413，Hague． co執esive so盟s，Proぐ． 45’1∼！1’1’1、 Co’1ゾ1． ／SCE， No、436， HI46，21）Shogaki，τ、and Kaneko，M、，Moro，｝｛、aad Mi員ara，S．（1995b）＝ 131−134（ill Japaaese）． Me般10dforpredictlngi’∼一蜘’undralneds［reng【hofclaysby uncon員nedcOmpressio旧es［withsuctiomneasurements，Proご、7）Lo，K、Y．（1970）：τむe oPζical s甘eng由of臼ssured clays， Gθαθぐhnゆθ，20（2），57−54、 ⑤y〃1ρ．So〃Sα’nρ1’n9，95−102（ln、lapanese）．8） N｛atsui，T．，Oda，K．and Nabes員i斑a，Y．（1994）：Deve皇opmellt and22）Shogak玉，T．，へ・loro，｝・｛、and L4atsuo，｝v玉．（1997）：A slope stabi韮ity apPllcationsforna〔uraldepOsitsofmlnimu磁triaxialcompresslon analys玉s co真sidering undrained stre疏9【h anisotroPy of natura里c蓋ay apParatus，7寵κh1∫oκ’50，42（H），17−22（in Japanese）、 deposits，T51ごch’イo−1ぐ’30，JGS，45（8），13一王6（in Japanese）．9）Matsuo，M．and Asaoka，A、（1976）：A statlstlcal study on a conven一 芝ional safセty factor meζhod，Soiたrαηd「Fo∼〃1（ノαだoη5，玉6（1），75−90．10） Nlaτsuo，N’i、and Shogak玉，T、（圭988）：E廷壱αof−Plasticity and sample23｝S員ogaki，丁．and Noc鼓ikawa，Y．（2004）：Triaxial stre119重妓properties ofnaturaldepositsaτκoconsolidaこiOnsエaヒeuslngaprecislOntriaxi− aL apParatus w註h sma賦size specimeus，So〃∫απグFヒ）μnゴα’101∼∫，45 disturbanceonstatlsticalpropertlesofu痘drainedshearstreng出， （2），41−52、 So’Z5α∼∼ゴFoπηo「（rがo／15，28（2）， 14−24・24）Shogaki，一、and Sakamoこo，R，（2004）l I妓e applicab瓶ty of a sma賊11） Nakase，A、（1967）：τheφu二〇allalysis of sζab重販ty and uΣ1con且ned compressioΩstrengt騒，SoiZ5姻ごF加ηゴα1io1∼5，7（2），35−50、12） Shogaki，T、（1995）：E9琶c【ive stress be姓av1or of days玉n uτ1con且ned compressiontests，So11∫oπゴFαご11伽’01∼5，34（4），169−171．王3）Shogaki，T、（1997a）：Asma麺diametersamplerwi芝hatwo−chaτn− diameter sa磁Pler witね a エwo−cむambered ぬydrauまic piston for 、laPanese clay dePosi工s，So’Z5α’∼ゴ’δ置’nゴα’io刀sシ44（1），113−124、25）S熱ogaki，丁、，Sakamoto，R ，，Kondo，E．andTac撤bana，H．（2004a）： Slnall diameter cone sampler and its apPHcabih【y for P韮eistocene Osaka氏／1a 正2clay，So’Z5απ‘ゴFo直〃1ゴo”oη∫，44（4），119−126． bered hydraulic piston aad￡he quality of its samples，Proc．14’h26）Sむogaki，τ、，Sakamoto，R．，Kanno，Y、and Nakano，Y．（2004b）： lCSM■五，Hamburg，201−204、 Small diameter cone sampler and iτs apr）licab11ity fo由ig恩yorganlc玉4） Sねogaki， τ， （1997b）： Strengtむ prope賞ies of c里ay by portable uτ1confined compression apParatus， P1’oご、 1／r∫。 Co17ゾニ G（∼o∼（∼ご1∼． 石ngrg、、弄o〆Co鯉α1P8vθ10ρ、，85−88．15） S轍ogaki， T． （2006a）：亙〉1玉crostructure，strength and consolidation properties of Ariake clay depos1ts obIained frQm samplers，／． 〆is7’闇ル望「11πθ1’、，3（5），98一王05．16）Sむogaki，T、（2006b）：An improved meτhod for estimat沁g ln一誼ε’ clayeysoils，Pヂoc、11π．S｝，〃∼ρ。E119’nθ帥1gPrααicθθn4P師01・ ’ηα1∼α∼oゾSoゾ1∫∠）θpo5’∫5（1S−Osαなα2004），153−158・27）Sむogaki，丁、，Nochikawa，Y、，Jeong，G．R．，Suwa，S．aRd K姓ada， N．（2005a）：S韮reΩgth and consdidation properties of Busan New PorζcLays，So’なα’1ゴノ＝oμn4α’10η∫，45（1），153−169、28）Sむogaki，T．，Sakamaこo，S．，Nakano，Y．and Shibata，A．（2006）：撫e appllcabiliζy ol’smaII diame菰er sampler for Niigata sand undrained shear strength of natural deposi［s， So”5 αηご deposits，So〃5σ∼∼4Fα’1∼ゴφo’1∫，46（1），1−15． Fo乱〃∼ご（πioη5，46（2），109−121．17）Sねogaki，丁．and Ma田yama，Y、（1995）：丁益eρortable uncon負ned29）Tanaka，H．and Locat，J、（王998）：Recollsideraζion of由e meanlng Qfplas￡icityindexingeotechnicalengineering，75ε’c1∼1一’o一幻50， compresslQII apparatus and iエs applicaこlon，Proc．40’1∼／GS＄γ〃∼ρ，， JGS，46（4），9−12（in Japanese）、 287−294（in∫apanese）、and Maruyama，Y．（1998）l Es芝imation of in一∫i∼‘’18）S藏ogaki，T undrained shear strength using disturbed samples witねt1｝in−waUed30）Yosむln＆ka，R。（1976）：E艶ctofspec1買1ensizeonsζrengthoflrock so玉1s，5θんoμgびε’！5μ，9，58−60（in∫apanese）。
- ログイン
- タイトル
- 3D-Visualization of Ground of New Runway at Haneda Airport
- 著者
- Masanori Tanaka・Yoichi Watabe・Masafumi Miyata・Saiichi Sakajo
- 出版
- soils and Foundations
- ページ
- 131〜139
- 発行
- 2007/02/15
- 文書ID
- 20986
- 内容
- TSOILS AND FOUNDATIONSVol. 47, No-1,131l39, Feb 2007Japanese Geotechnical SacleL)3D-VISUALIZATION OF GROUND OF NEW RUNWAY AT HANEDA AIRPORTMASANORI TANAKAi), Yolc ru WATABHi), MASAFU "{1 MIYA'TAii) and SAIICHI SAKAJO ii)ABSTRACTThe 4th rumvay of Tokyo Haneda International Airport is no¥ ' under planning. The distributions of lveak layer,bearing layer and their en*'ineering characteristics must be clarified to some extent. Prior to detailed foundationinvestigations leading to for detailed designs and constructions. Ne¥v soil investigations of boring, sampling andlaboratory tests ¥vere conducted in this area. Using these data and the past boring data frorn the database, the vhole3D ground was visualized by the 3D soil layer estimation system, that ve have proposed. Subsequently, the 3D groundfor the rum¥'ay could be successfully modeled. This 3D model is very useful to recognize the general soil layer compositions for planning the detailed soil investigations on their test items, depths and numbers. Furthermore, this result isexpected to reduce the costs regarding numerical analysis, design and construction.Key words: alluvial deposit, dilu¥'ial deposit, geology, Kriging, standard penetration test, visualized 3D ground (IGC:CO /C3 /C4 IC9)INTRODUCTIONThe Ministry of Land Infrastructure and Transport(MLIT) has started a committee on "Third Anpcut m theMetropolitan Area Survey" since 26th September, 2000to examine the shortage of air'port capacity in Tokyometropolitan area.O ayFollo ving that, the MLIT had offered a basic construction plan of the 4th run¥vay. This new r'umvay ¥¥'ill beconstructed ofishore to the south of the current Hanedaonnecting bridgeAirport. It ¥vill be parallel to the B runway in the north assho¥vn in Fi**. 1.In order to r'ealize this plan, full scale soil investigations ¥vill be conducted. Before this, the distribution ofthe weak layers and bearing layers must be determined ingeneral and their soil characteristics must be identified.Usually in case of the routine soil investigations, the*'eological features are drawn on the main 2D sections ofthe construction fields. Follo¥ving that, the geological¥lFig, l.Basic plan of re-expansion of HanedQ 1000nL-lAirportfeatures on their perpendicular 2D sections would bechecked additionally. However, in such a lar*'e scaie andlayer classification criteria obtained from multi-re*'ression analyses of soil parameters.Therefore, the ne¥v soil investi**ations were conductedin the construction area and alon*" axis of the connectingmassive area in Haneda Airport, the ¥vhole groundshould be classified and displayed in 3D.On the other hand, the authors have proposed the 3Dbridge between the new runway and the Haneda Air'por't.Finally, the ground for the ne¥v run¥vay vas displayed insoil layer estimation system in order to increase the utilityof the soil database in engineering practice. This systemhas been successfully applied on the various sites.This system can specify soil layers in 3D by inputtin*' aset of soil parameters estimated spatially into the soil3D by usin*' this system based on the nelv soil investigation results and the past boring database.The boring database used ¥vas developed by the Port*) Geotechnical and Geo-environmeut Division, Por and Airpor Research Institute, Japan (tanakam@pari go-jp, ¥vatabe@pari.go.jp).'*) Haneda Airport Expansion Project Section, Kanto Regional Developmem Bureau, Minis r¥ ' of Infrastructure, Japan (miyata-m92v2@pa,kur.mlit.*･o.jp).=**)Applied Information Science Center, Kiso-Jjban Consultants C*0., Ltd. Japan (sakajo saiichi@kiso.co jp).The manuscript for ihis paper vas received for revie¥v on January lO, 2006; approved on Jul_v 26, 2006.¥Vritten discussions on this paper should be submitted before Septernber 1, 2007 to the Japanese Geotechnical Society, 4-38-2, Sengoku,Bunkyo-ku, Tokyo 1 1'_-OOI 1, Japan. Upon request the closing date may be exiended one month131+ TANAKA FT AL.132from A-3 to A-7 and the sites from A-9 to A-13 arelocated alon*' the sea side and the airport side from theaxis of the runway respectively. The sites A-1 , A-2, A-14and A-8 are located on the axis of the new run¥vay. Thesites from B-1 to B-3 are located on the axis of the br'idgebetween the new run¥vay and the existing HanedaAirport. The distance bet¥veen these borin*" sites isapproximately 500 m. This distance is of course not closeenou*'h from the Japanese design codes. Ho¥vever, theaverage distance of the new borings in the area to bedisplayed in 3D is 750 m. Therefore, the authors used the26 old boring from the database of Port and AirportResearch Institute. Although they are not scatteredhomogeneously in the area, the avera*'e distance amon__'ail boring sites could be reduced to be 470 m.This value is still not close enough for the code of earthwork in .Japan. The Japanese Road Committee suggestsFig. 2. Area to display ground in 3D and atl soiinvestigationsthe appropriate distance to be 100 m for the preliminarysoil investigation of sounding and sampling. This is theand Airport Research Institute. It contains 22,000 borin_'reason why the acoustic explorations were conductedlogs ¥ 'ith SPT results and soil property data. In thisconstruction area, the 26 borin*" data ¥vere used from2,300 boring database in Haneda Airport.The main purpose of this research is to investigate ifthis soil layer estimation system can make a realistic 3D"_round model in such a large scale area. Subsequently, atogether ¥vith soil investigations. However, this distance3D **round model was successfully made because therewas adequate soil data available though not abundant.This implies the importance of soil database use inmodeling ground.AREA TO DISPLAY IN 3D AND AVAII.ABl,EBORINC. DATAof 470 m seems to be able to guarantee accuracy to someextent from the correlation of the soil parameters.Because the statistical result of soil properties su"-*'eststhat the maximum distance to estimate soil properties is470 m.Geo!ogica! I,ayers ii? TTvo Cross Sections a!ong t/1e MainA xisBefore conducting 3D soil layer estimation, the generaltrend of soil layer structures must be reco*'nized ft'om theboring lo*'s. Herein soil layers on the t¥vo cross sectionsaltitudes of ground surface and bedrock. Then, the soilalon*' the traverses, 1) airport side and 2) sea side aresho¥vn in Fi**. 3. These figures vere made from boringlogs by the geologists. These are not correct geometricallybecause they are projected on the same sections althou*'hthey are not on the same sections.From these figures, it is seen that four main layers, 1)Yuraku-cho layer, 2) Nanago layer, 3) Tokyo layer and 4)parameters would be estimated in the 3D space byEdogawa layer are deposited from the surface. Yuraku-Kriging. The criteria to classify soil layers would be calcu-cho layer is the upper half part of alluvial layer in Tokyolated by a multi-regression analysis of several kinds oflo¥v iand. It was deposited in the sea by the sea level rise insoil parameters. It is possible to define the soil layer nameat a specific point.layer is the lo¥ver' half part of alluvial layer in Tokyo lo¥vIn order to apply the three-dimensional soil layerestimation system, the available boring data and soilparameters must be re*"istered on the digital map. First,the 3D estimation area should be defined with theThe area to be displayed in 3D and all soil investiga-tions are marked on the di**ital map around HanedaAirport in Fig. 2. The target area is the inside of a rectan-gular square 4,300 m by 2,200 m. There is also the rectan-gular mesh of acoustic explorations. In this area, theJohmon era beginnin*' about 10,000 years ago. Nanagoland. It ¥vas deposited in the fresh¥'ater to sea water be-fore around 18,000 years ago. Tokyo layer is the diluviallayer ¥vhich consists of upper marine clay, middle sandand lower mixture of sand and **ravel. Edo*'a¥va layer isthe diluvial layer which consists of the upper sand and thelarge white circle ( - , ) sho¥vs ne¥v boring site and the blacklower sand containing clay. They both have bedrock ofcircle (o) sho¥vs old borin*' site in the database. Smallgravel. These layer boundaries ¥vere manually interpolated from the boring lo*"s. Furthermore, each layer consists¥vhite circle ( ' ) sho¥vs boring site out of the area. At theboring sites, SPT and samplin_9: ¥vere conducted. Severalof more than t¥vo sub-Iayers of clay, sand and gravel.kinds of soil tests lvere conducted at laboratory. SeaTherefore, the layer structures are actually very complicated.depth ¥vas measured in this area to investigate theThree traverses of sea side, airport side and bridge axisfor soil investigations are sho¥vn in Fig. 2. The 17 borin*'sHowever, the characteristics of these layers can beroughly understood from SPT results in boring logs.N-values for Yuraku-cho are too smail to be measured.vere conducted at A-1 to A-14 and B-1 to B-3. The sitesN-values for Nanago layer are 20-30 for sand and are less_9:eographical **round sur'face in the sea., TNE¥¥! RUN¥¥IAY A'T HAi¥'EDANanagoTama-Rivero()Jonan-Isl ndstrong. The forrner and the latter are ar'ound 50 and more;A-8[A-9 A-iOj ----{ A-iilA-i2] A-i3]A-2 A 1-10()-20 o133than 10 for clay. Tokyo layer and Edoga¥va layer areYu aku- ho layeFla yerAIRPORTthan 50 respecti¥'ely.Even though these t¥vo sections are only 400 m a vayfrom each other, some difference can be seen. Yuraku-l-30 o-40 O-50 ocho layer on the airport side is a little thicker than that on-60J) }the sea side. On the sea side, bet¥¥'een boring sites of A-5-70()-80 oand A-6, the boundary of Yuraku-cho layer and Nanago:-90 o-ioo o= 'Hgoes lower than on the airport side. Nanago layer on theiisea side is a little thinner than that on the airport side. OnH800 1,200 1,60c; 2,000 2.400 2,80a 3,200 3,600 (m)the airport side, Edoga¥va layer is much rnore intrudedbedrock Edogawa iayer Tokyo layerinto Tokyo layer' than the sea side. Therefore, the cr'osssection on the sea side seems veaker than that on theairport side. Such complexity was due to the Tama RiverEdogawa layer is muchintrudecl into Tokyo layeractivities over a long time with the many repetitions of sea(a)¥vater level changes in the glacial age.Any engineers regarding this project have to pay attention to the distribution of the bearing layers for designsand constructions. Therefore, the authors tried to definesoil layer constitutions in 3D r'ationally in this area. Theinformation used are 1) boring, sampling and soil properties, 2) acoustic exploration results, 3) soil database, 4)The boundary between Yurakv-cholayer and Nanago layer is lowerbetween A-S and A-6,Tama-R;verNanago layer Yuraku-cho iayerOOJonanIs!andO O-20 O-3 Osea bed depth contour map and 5) geological informa-O-40 Otion.50 O-60 OThis time, from an engineering point of vie¥v, it has-70 O-80()been requested to classify all layers into the ) Iayers, i)alluvial soft clay iayers, ii) diluvial clay layer mixed ¥vith-90{):'.*"-'" '><";',''sand, iii) diluvial sand layer ¥vith N-values of about 50,iv) diluvial gra¥'el layer with N-values of more than ,50and v) bedr'ock layer. These 5 Ia)'ers roughly are drawn":-100()400 f800.200 1,600 2,000 2,400i2,800 3,200 3,600 (m)Tokyo layerEdogawa layerbed ro cktentatively in this figure.It is actually a ¥'ery difficult task for geologists and civil(b)traverse and (b) Geologicai soil la¥. er constitutions on the sea sideengineer's to define the soil layer' boundaries experimentally. Especially, in determining the layer boundaries fortraversethe above Edogawa layer, the pre-defined results ¥vereFig. 3. (a) Geo!ogical soil la¥.'er constitutions on the airport sideTable 1.Data No.Soil data of A4AhitudeSoil layer(A.P.)(m)¥VaterPlasricit.vcontent t'**index lpFlnecontent F*(g /cm3 )(o/o)(o/o)(o/o)157.S146.2145.2138.9142.8i33.688.3S-'.360.446.898 699,799,799*499,799 4, 6.584 . 1SpecificN-vaiuegravit*Geolo vEng.YvcYucYucYucYucYucYucAcAcAcAc- 21 .032 . 662- 24.03- 28.53YlcYlcYlcAcAcAcDcDcDc2.6382.6362.6382.5932.6362 6192.7082 7512.712, 6ToclDc- 72. I l, 7Tos lDs- 72. 9428Toc7Toc _- 74, 1 11346789lO. 5.53- 27 .0331.53- 34,,53- 36.03- 37.53- 40.5379.272.259 l43 . 76. 153.144 842.3655764.9Z31Toc2Tog23,To :2DcDcDcDgDg33Eds2Eds2DsDs2930342.72123- 76, i l- 77.88- 78,32- 83.3388,37- 93,362.7322.6682.6752 661more than 50nore than 50more than 50more than 502.832.7372 7342 709X-coordlnate: - 960 rrl, Y-coordinate: - 57_,OOI m (Digital coordinate), En . Is engineermg name.44.827 3, 9,74)-.539*935.421 950. i29 78.7457.429.385.895.992.910.48.728.24 1 .216.518.5 134TANAKA ET AL .modified based on the acoustic exploration results andAn unknown value can be esrim tedthe *'eological fact, that the layer contains volcanic ash.from suri-ounding knol n¥'al uesColltents of Soi! Data on DatabaseIn this research, the database developed by Port andAirport Research Institute is used and all new soil investi-ation data ¥vere registered with the same database form.An example of the soil data at boring site A-4 is sho¥vn inTable i. In the database, geolo_ :ical soil layer names arerenamed to be alluvial layers and diluvial layers asengineering names. The former names are alluvial clay(Ac), sand (As) and gravel (A**) Iayers. The latter namesare diluvial clay (Dc), sand (Ds) and gravel (Dg) Iayers.¥Fig. 4.Target SpaceSpatial statistics tecl]nique by KrigingYuraku-cho clay layer and sand layer were renamed asAc and As layers. Yuraku-cho lower clay layer was re-technique, because any information obtained at manycategorized to be Dc because of its similarity ¥vith Nanagoclay layer. It ¥vill be explained later. Clay. of Nanago,seen in Fig. 4. These data should be in the target space tointerpolate them. This method also can be valid in 3D andhas been applied widely to the various fields in geo-technical and geological practices. The estimated value z (x) canbe expressed by the ordinary Kri_ging as follolvs summar-Tokyo and Edogawa layers ¥vere renamed to be Dc layer.Yuraku-cho lo¥ver clay layer ¥vas renamed as Dc, becauseIts characteristics are similar to Dc. This reason ¥vill beexplained in the later section.This database contains l) N-value, 2) ¥vater content w*,3) plasticity index lp, 4) fine content (percentage of smallparticle less than 75 /Im), 5) specific *"ravity and so on.Furthermore, it contains 6) X-Y coordinates (localcoordinate of Haneda) and 7) altitudes of ground surfaceand soil layers. And it is not explained here but thisdatabase also contains a fe v mechanical test results likeoedometer test, unconfined compression test and tri-axialcompression test.Each of these data is useful for the geotechnicaldesigns. This database ¥vill ho¥vever be much more usefulif some of them can be the criteria of soil characterization. Furthermore, the authors 'ill define soil layers byclassifying soil types. In this case, the applicability of soildatabase ¥vould increase very much.3D SOIL LAYER F.STIMATION SYSTEMpoints can be rationally estimated at a certain point asiz,in>" all the observed values (Cressie, 1993).z (x) =wjZ (xj) (1)where, z(x): estimated value at the location x, wj: weightfactor at the location x!, z(xi): the observed value at thelocation xj, N: number of observed samples.The above weight factor is calculated from thecovariance among the observed data. The weight factor isrelating mathematic,ally with the secondary order errory(/7), which can be calculated by the following equation.=1{z(xj)-z(. 'j)}22Nh i,jwhere, y(11): the secondary order error for the data thatare h far away each other, /7: the distance bet¥veen dataeither in horiz.ontal direction or vertical dir'ection, Nh:number of pairs of samples with a span of /1 among them,Z (xj): value of a sample at the distance of xi, z (xj): valueAny soil designers are required to define soil layers andtheir soil parameters rationally. This task can be achievedby this 3D soil layer estimation system.This system can judge ¥vhich soil layer a specific soillayer belongs to. It can be done by inputting a set of soilof a sample at the distance ofparameters interpolated spatially by Kriging method into¥vhere, y(h): the a, c and d are constants to express y(h).the classification criteria, ¥vhich is calculated throu*'h theIn the above equation, the y(/1) becomes a constant ofd at that h is O. On the other hand, the y(/7) becomes d+ cat that h becomes + oo. The cut d means a potential errormar*'in. From this equation, the larger a is or the smallerc is, the smaller y(h) is ¥vith the larger /1. Basically, themulti-re*'ression analysis of these parameters (Tanakaet al., 2002, 2004a).This system has been applied to the marine clay inOfunato harbor (Tanaka et al., 2004b) and the slopedi'Finally, the caiculated relation of y(h) and h can besimply assumed by the follo¥ving exponential equation.y(h) = d + c(1 - e }*/*) (3)g:round in the mountainous area of Shikoku Islandabove equation expresses a natural decrease of correla-(Tanaka et al., 7_005). If it could be linked with GIStion of data estimation with the horizontal distancesystem, this system ¥vould be more convenient and useful.increase. This relation is called to be variogram, ¥vhich(Sakajo, '_005).can be selected from various mathematical functionsEstil77atiol? of Matel'ia! P/'oper'ties by Kl-igingbesides the exponential curve in this system.As an example, the calculated y(h) values and horizon-The geologists and geotechnical engineers usuallyestimate the soil layers experimentally ¥vhen makingtal distance h on N-values at the Haneda district aregeological sections. In such a case, Kriginca seems a goodalso is shown in this figure. From this figure, it is seen thatplotted in Fi*･. 5. An approximate curve of the Eq. (3) NE¥V RUN¥ ;AYAT HANEDA AIRPORTl 35600Eva!uation of Estilnated Soi! P/'ope/'ties on the Main Axis500f'ol' the Present P!anFigure 6 sho vs N-value distribution in 3D estimated by400Krrging. Color index is that dark blue is less than 10, Iightblue is 10 to '-O, green is 20 to 30, yello¥v is 30 to 40, and>* 300200100oO 5002 500 3 Ooo1 ,OOO 1 500 2,000horizontai distance h (m)( s; )and Edoga¥va layers, but unf'ortunately these color' gradations are not ciear in identifying these layers. These colorsare changing at places and a green color area is seen in theLTalue500400Et :: c] Pr(h) * 150 - 200(1OQe = ** )300ha200 1_ t];.:;measured piasioityindex PI,- ap roxirnatB curve1 OOored area.To see more details, the 2D cross sections of N-value,plasticity index lp and natural ¥vater content }t' are sho¥vnin Fig. 7. These are the cross sections on the main axis ofthe ne¥v run¥vay, vhere the boring logs on the airport sidetraverse are projected as references.In the figure of N-¥'alue, it is found that the ¥'ery softground ¥vith N< 10 is deposited from the surface up too 5001 OOO500 2 OOO 2.500 3,000horizentai distance h (m)( b ) ptnstieitv_A.P.-35 m and the soilvith 10<N<'_O is depositedf'rom the bottom up to A.P. -50 m. Under thls, ratherstrong soil ¥vith 20<N<:40 is deposited up to A.P. - 55Qde: /1*m. Furthermore, strong soil1 200r(h) ･OO800>* eooOO(1 e * ' *)Q 'E=deposited almost horizontally below A.P. - 55 m.FJoF Q rTleasured water-content- approxirn te eurve200oO500 1,000 1 500 2 OOO2 500 3 Ooohorizontai distanee h (Fn)( c ) watcr conte t f'*Fig. 5.vith N-value of' rnore than50 is deposited belo¥v it up to A.P. - 80 m. These findingsare simpl.¥* summarized in Table 2.Generally, the soil vith N-values of mor'e than 40 isooO400red is 40 to 50 and more than 50 in N-¥'alue. The darkgreen means the bedrock. Therefore, the distribution ofbearing layer ¥vith N> 50 can be understood from the redcolor and dark reen areas.The yello¥v to red color areas seem to be in the TokyoVariogram of IV-valueHo vever, there are weaker' soils with small N-vaiuesbet¥veen A-10 and A-11 and through A-1 to A-13. Fromthe figures of l and w , the portion between A-10 andA-1 1 seems to be sand or intermediate soil because I+. isless than 20 and w** is less than 500/0 there. The soil fromA-1 to A-1,3 seems clay because lp is about 40 and 4'** isrnore than 500/0 there.Combinations of soil parameters, N-value, Ip and w'**can determine soil characteristics mentioned above. Theestimated accur'acy of these soil properties by Krigingvilly(h) increases ¥vith /1. It meets a turning point at h of 500be explained in a separate paper.m and it becomes a constant at /1 of 2.000- 3,000 m.Another reason for 500 m to be the maximurn reliableMu!ti-Re*"/'ession Ana!ysis of Soi! Data for Soi! Layej'distance to interpolate N-value, is that cyclic frustrationsof data are seen after h of 500 m in this figure. It may bethat the observed data are not enough in the target spacesaid longer than the 500 m. This means that the maximum distance to estimate N-value should be ¥vithin 500C*!asslficatiol7 Cl itel'iaHerein, the authors ¥vould like to explain soil classification criteria for the soil parameters. This is equivalent todefinin*' the soil characteristics. Multi-regression analysism. An average distance bet¥veen borin_g: distance is 470 mamong the soil parameters can produce these criteria.Then, by inputting the soil parameters estimated byin the soil investigation. The estirnation capability by thisKriging into these criteria, all soils can be classified to besystem is close to the limit. This conclusion was support-in the proper soil layers.ed by the same relations of y(h) values and horizontalExamples of criteria by regression analysis are, 1) acr'iteria from natural ¥vater content and fine content anddistance /1 on plasticity index and ¥vater contents.From this figure, it is interesting that N-value has anerr'or at that h is zero, ¥vhere the y(/1) is about 100 and itssquared value is 10. This implies that N-value might beabout 10 different at t¥vo very close points due to the inuniformity of soils. This is the resuit in the horizontalway. The vertical lvay also can be considered, althoughthe rather poor correlation with distance vould be used.2) another criteria from altitude and plasticity indexsho 'n in Fig. 8. Clay and sand can be separated clearlyand Ac layer and Dc layer can be separated clearly.In this lo¥ver figure, Yur'aku-cho lo ver layer vascateg:orized into Dc. 'The criterion ¥vhere itvas classifiedto be Ac, seems unnatural. Therefore engineering properties are very Important in classifying soil types. I OO. OTANAKA ET AL^136H#ntds A "Table 2.5D{_.';1;! 40Ct]aracteristics of the estimated soil properties bl.' KrigingPlasticity ¥Va erAltitude(A P.)soillp (o/o) Ts'** (O/o)( n)105rT)Supposedindex con emN-valuelayer{ .;.- -35 m10> 30O - 10(dark blue)Ac> 50(green lo (gTeen toyello¥v o red): yello¥v, red)ON-ve; e3) m - - 50 m< 30lO - 20Fig. 6. 3D distribution of estimated !¥r_value (SPT))O m - -55 m30 - 50(light blue(light blue)to blue)20 - 40AslDc(light blue) ,Ds/Dg< 30(green to(blue)yello¥v)Tama-RiverJonan- Isiand-55 m- 80 m1 o o i--0.0 --- A-8A*9 IA*iO I: AIi A i2 A 13 A-2･ A-iIT'ith 20 to 3050-*-30. O '----40. O '---40-50.0 *-"-; 30lOO2090IoSoSO O i-----70 O ----80 O J---e ool 200 1,800 2,400 3000 3.800 (m)O70-va ue60T m -RJverJo!A-9 : A-lOAAAA A1A AA ^ ^^L"a!)AASA4 4 ; " AAiOl ,, A,.( a)0.01 A 8Bedrock- 80 m --20 O T--ODs / D_",*(red)N-valuesOO--90 O> 40 - 6050oo40 oo c}30 ooo -'n-ls andA 11 A i2 A i3 A 2 A-1 !pisabout40.20 -- I 0.0 --s hdoA Clavo Sand- Boundan' Lineo ciO -- eoe;o-20.0 --o50o200150lOO1 '( )(a)70.0 ----Criter'a to set-80.0 l.__-90.0Yurakl'-che layer to Ae-- .O-1000*- -500 1 200lp is iess than-O1.800 2.400 3000 3,600 (m)fJonan-[slandTama-River230 1":'el'"".SltT"a"III II q' ' $- 'e8 vol"o.,?J't'P(b)l t; ,':l'l'e i'1 ･e'] o"' :rT ;dP';P:' e Ie'::Qe(po10 IfSo "' "-' T "' L :' ･ d""" t" ' , . f1 o{) +--OOA-8 [ A-9 [A-iO A-liA-12:A-i3-1- A-2 --- A-1 ti'n is more than 50- 00+-20 o !----soJe' 4I4 "I"'c ' AAAd:80A'_ ' ' I*'[ "!AI':;su-ehofwfle Ac(YUraku-co upper layeAoi J':A1 '1h'I l;- : '-90d L ., , ,A Dej BotJndsrye (A$)-ioo"' 8QundsryLiLine(De)-70 O '-O-800 t ---20sobedroek_;={ll: wn{ )200 1,800 2.400 3,000 3eOO (m)6080T OO!, (Cr{te a to set-1 OO O * ---O 600id<To i-90.0lll:. 'e -Yuraku-eho lewer layer ta De(b)t'rs is le_ s 50(c)Fig. 7. Estimated properties on main axis of the nelv runlval ' of thecurrent plan: (a) 1¥r_va ue (SPT), (b) Plasticity index (Ip) and (c)N. 'atural water content (,t' )Fig. 8. Examples of soil classification criteria: (a) Fine content (F*)and natura ¥vater content (w ) and (b) Ip and altitude level : ;,NE¥V RUN¥VAY A'T HANEDA AIRPORTTo generalize regression analysis, the following multiregression analysis is adapted employin*' the polynomialfunctions.The equation used is as follows:Y aa Xl+a2'X +a3 X +a X a X Ta6 X (4)13 fAg does not exist in this area. All soil classificationcriteria used are summarized in Table 3.In the actual computation, the computational area ¥vasseparated into boxy meshes as precise as 50 m by 50 m by,50 m. Then, each box was identified to be a proper soiltype by the above cornputations.Where, Y: objective variable, X: explanation variables; Xi: ground level or altitude (rn), X._: N-value, X3:natural lvater' content, w (olo). X4: Plasticity Index, Ip,X5: Fine content, F* (olo), X6: Specific gravity, G.As an objective va 'iable, Y should be set to be a specificvalue (for example, Y=0 can be set that clay is for Y> Oand sand is for' Y<0) and then multi-r'egression analysisis conducted.By inputting the parameters estimated by Kriging intothe above equation, the sign of Y ¥¥'ould be checked tojudge the soil layer.Soi/ Layer C!asslfication RestdtThe ¥vhole ground for' the ne¥v run¥vay is displayed in3D in Fig. 10. The 2D cross sections along the t¥ 'o soilinvestigation traverses and the connecting brid**e ar'esho¥vn in Fig. Il.First of all, from Figs. 1 1(a) and (b), it is found that theAc, Dc, Ds and Dg layers can be classified very clearly,although the layer boundaries ¥vere srnoothed (Shiono,2000). In these figures, the As layer ¥vas neglected becauseit ¥vas sholvn in a very srnall area. The Dg layer boundaries ¥vere rnodified by the acoustic exploration results assimilarly done in Fi*･. 3.SOIL CLASSIFICATIO_N CALCULATIONHere, the authors tried to define soil iayers compositions of the whole ground for the new r'un¥vay by inputting a set of soil parameter's estimated spatially into thesoil layer classification criteria obtained fr'om multiregression analyses of soil parameters.The classification calculation fiow is sho¥vn in Fig. 9.The 3D Iayers model is very useful because any crosssection can be generated ¥vith ease. This can correspondvery easily to the change of plan, even in the case ofchanging the main axis of the runway.To recognize the details, it is better to see the 2D crosssections. The t¥vo cross sections on the airport side andsea side traverses apparently resemble to those inAt first, soils are classified into clay or gr'avel extremely.Figs. 3(a) and (b). Ho¥vever, these fi**ures are very correctSecondly, the soils classified as clay are classified againin geometr'ical scale. These figures were not manuallyinterpolated based on experiences like in Fig. 3. And itlvas assured from the sorne triai calculations that themaximum difference bet¥veen the estimated soil layerboundary levels and those in Fig. 3 is about 2 minto clay or sand and soils classified as gravel are classifiedinto sand or' gravel.Then, the sedimentation types ar'e again classified intoalluvial or diluvial layer. Through these steps of soilclassification, all the soils can be classified as Ac, As, Dc,Ds and Dg. It was noticed that Ag ¥vas ignored because} grain siznsans Airpor(!c I ass i f ica t i anbv sedi entcl ass i f i c_e ! r'4t i Or･rFig. 10. 3D estimated soil la) rs of the ground for the new runwa .'Fig. 9. Calcu atlon flow for sorl classlficatron'Table 3.aealCtassification criteria and their parametersala3(7sa{ravel - O. 9920.000o ,ooo - 0.0990.000Clay-Sand I .5 1 80.000O.045 - 0. 1 20o ooo1 627O . OOOCla.v-(Jl.316C16Y>0Y< O0.000ClayGravelO.OOO ClaySandl 207 -O.OIOO. I I lo.oooAc-Dc0.081 - I .3780,0000,000o 567AsDcAs-Ds- O.7 10 - 0.885o,ooo,_. 1 99o oooAsDsAs D,:'(1- I .OOOo.oooo,oooo oooo.oooAgDgSand-Gravel(;- O. 104O . 3 Sand20 G ravel TANAKA ET AL.13SJonan-lslandTama-RiveOO-a fe¥v new boring data in Fig. 11(c).For the case of O_ funato harbor, the soil layer classifica-0.0-A-8A-9 - A-iOA._ -i_A. .-1._ 2A-13 A-2 - A-i .-1 0.0 --20 Otion was not precise enough because of the ambi..guousclassification cr'iteria due to the shortage of materialproperty data (Tanaka et al., 2004b). In this case,-30 Oho¥ve¥'er, the many soil properties from the soil databasecould be used here to obtain precise soil classificationcriteria. Therefore, it can be concluded that any database-40.050 O80 O-70 Ocould play an impor'tant role in the modeling of ground-80 Osoil in engineering practice.-90 o-1 oo oo600.2008002 4003 ooo3,eOO (m)(a)The follolvin_g: conclusions were developed in thisTama-River*Jonan-ls and100oo1 o O 'A-8 :] A-7 1 A-6A-5CONCLUSIONSA-4 :A-3A:-2A-i --20.0-30{) ;-40 o }50 O-60.0 s{research. Furthermore, the rational and precise 3Dground modeling developed could promise the moreaccurate numerical analysis like on FEM, ¥vhich canexpress ground behavior by the advanced constitutiveequations of soils.1) Ne¥v soil investigations ¥vere carried out offshore atHaneda Airport. By usin*' these data ¥vith the past boringdatabase, the three dimensional (3D) soil layer estimationsystem could clarify the basic soil layer compositions of-80 othe ground for the ne¥v rum 'ay of Haneda Airport.2) Although these borin*' distances lvere not close-90.0 *enough as recommended by the various design or-70 o --1000o600 1 2001 .8002 4003 ooo3500 (m)(b)construction manuals, the accuracy of the estimation canbe secured to some extent from the data correlations withdistance.3) Consequently, the 3D soil layers ¥vere classifiedNe ^/-RunwayAirportOO-B- 1h2B-3A-100.0 -into the follo¥ving five layers, i) the soft clay ground, ii)the alternate mixture layer of sand and clay, iii) thebearing layer with N-values of about 50, iv) the bearing-10(}clay layer lvith N-value of more than 50 containing-20 Opartially clay, v) the continuously ¥'ery strong bearinglayer' ¥vith N-value of more than 50.30.0-40()4) This 3D _g:round model wiil be very useful for a-50 Odetailed investigation to define the place, the depth, and-eO Othe number in preparation of constructing this run¥vay.70 OIn addition, since the soil layers were once clarified in 3D,80 Oit is possible to dra¥v any corresponding cross sectionseven if a present plan would be changed.-go o5) This 3D soil estimation system based on the soil-1 OO Oo 200 400 600800 l ooo.200 (m)(c)Fig. 11. Estimated soi] Ia: .'er classifications: (a) On the airport sidetraverse, (b) On the sea side traverse and (c) On the axis of theconnectin"* bridgeproperties estimated by. Kriging with the soil layer classifi-cation criteria from multi-regr'ession analysis is extremelyeffective to define en_g:ineerin*' Iayer compositions.6) The soil database used in this study developed byPort and Airport Research Institute ¥vas found to behighly applicable in geo-technical engineering practices,if used ¥vith this soil layer estimation system.The soil layers could be classified successfully by thefi¥'e layers, i) the soft clay ground, ii) the alternatemixture layer of sand and clay, iii) the bearing layer withN-values of about 50, i¥') the bearing layer clay ¥vithN-value ¥vith more than 50 containing partially cla}.', v)the continuously very strong bearing layer with N-valuetude to Mr. T. Nisioka at Kiso-.Jiban Consultants Co.,Ltd. and Prof. K. Shiono at the Osaka City Universityof more than 50.for their' helpful dlscussions.Furthermore, the soil layers are classified very clearlyon the axis of the connecting bridge, although there wereACKNOWLEDGEMF.NTSFinally. , the authors would like to show sincere grati- 139N鷺W RUNWAYAτHANEDAAIRPORT6） Tanaka， 猶・1、， Sakajo，S，and N三sむioka，T、（2004a）：A study onREFERENCES ra芝ional stratum estinlation usi鷺g soH database，39’h！1111r、Co1∼ゾニ1）Cressie（1993）：S∫α”5！’c5∫orSρα1’α1P徽，Wiley． ／G8（Niigala），181−182（lnJapanese）、2）Researc短Ins【imte of Civil…三ngineeri鷺g，Tokyo Govemme撚，Tokyo7） Tanaka， ！y董．， Sakajo， S、 ＆nd Nish玉oka， 丁，（2004b）： 3D Sにa￡ロm （districエ） （1996）：The deep underground geolog｝・， 710勘vo （3ε0109’（♪ εstlma［ion System Using So旦Da【abase，Cα∫θκ醜01二y qブU1カα’∼ ！VαρCo〃εご’io／1，（6）（in Japanese）、3） Sakajo，S，（2005）：New technolo9玉es fQr so員investigatio鷺s，P”oc、 Gθo−／’401F’ηα”c5，澱rC10Thailand，presented as an exこra paper．8）Tanaka，レ1．，Sakajo，S、，Nis短Qka，丁、and Sakai，τ．（2005）：A study 71θ6ノ∼∼泌θ1P／25θ〃1〃110n，／ノ1！、Co∼∼∫0θo！召納．zシ∼9！8．，Osaka，Japan． of creation of rational2D design cross sectio良in tlle mou撚ainous4） Shiono，K，，λ｛asumoto，S、，Sakamoto，∼1、and Yao，A，（2000）： areabasedo捻3Dgroundvisuallzationsysτem，40∫13・4肌Coπ≠ノG5 Geological sarvey and Ioglc of geologic map，Computer processing （Hakodate），31−32（in、lapanese）． anditsproblem，1吻〃∼顧o∼1Gθ010＆｝，，玉1（4），241−252（ln9）Watabe，Y．andTanaka，M、（2004）：Geotechnicaldatabaseforpor｛ Japanese）． and airport consζructlon ln Japan，Cα5θHi甜oぴo∫Uめα’∼θθo−5） Tanaka，∼1、，Sakajo，S，and Nis赴ioka，T．（2002）：S芝udy on use ofsoiI 1顧oηn如c3，パTα0，Thailand，72−83， da℃abase，57∼hパn1π∼α1／C五S，3，681−682（in Japanese），
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- タイトル
- Failure of Reinforced Earth as Attacked by Typhoon No.23 in 2004
- 著者
- satoru Shibuya・Takayuki Kawaguchi・J. Chae
- 出版
- soils and Foundations
- ページ
- 153〜160
- 発行
- 2007/02/15
- 文書ID
- 20987
- 内容
- R !'.SOILS AND FOUi¥'DATIONS¥rol47 ,Nol, 153l60, Feb 2007Japanese Geoiechnical SocielyFAILURE OF REINFORCED EARTH AS ATTACKEDBY TYPHOON NO. 23 IN 2004SATORU SHIBUYAi), TAKAvU}(1 KA¥¥*AGUcHlii) and JONGGIL CHAEiii)ABSTRACTIn October 2004, Typhoon No. '_3 attacked western part of Japan, causing severe damage to infrastructures over a¥vide ar'ea in Kansai. In the early morning on 2lst October, failure of a large Reinforced Earth lvall with the maximumheight of about 23 m took place in a mountainous area in Yabu city, Hyogo Prcfecture. The debris flo¥v from ther'einforced embankment attacked a ¥varehouse at the foot of the mountain, however, no casualties ¥vere reported.Immediately after the incident, an investigation committee ¥vas set up vith missions to investigate the causes of thiscatastrophic embankment failure and also to examine any possible occm'rence of' further slope disasters in this region.In this paper, the failure mechanism by considerin*' causes of the slope failure is discussed based on the results 0stability analysis performed using laboratory and field data, coupled ¥vith topological information and the rainfalldata. Some lessons learnt from this unique case study ar'e described ¥vith reference to the design and construction ofReinforced Earth wall in rainy mountainous ar'eas, in particular.Key words: design, in-situ test, Iaboratory test, Reinforced Earth, shear strength, slope disaster (IGC: B5/BI I /C*,3/D6/E6/H6)INTRODUCTIONThe design and construction manual of ReinforcedEarth Arm6e wall does not consider any ¥vater in andWa i*¥.adjacent to the reinforced soil. Similar'ly, Iittle attentionis paid to infiltration of rainfall ¥vater' from the surround-'; +･･}ing area. Nevertheless, the Reinforced Earth using metalstrips has been popular in use for constructing local roadsin mountainous area in Japan, ¥vhere the attack ofseasonal hea¥'y rainfalls is commonly encountered.Moreover, ¥vhen considering the need for reducing theconstruction cost, Iocal government is often obliged touse local soils ¥vith lo¥v permeability and low frictionFig. l.angle in constr'ucting Reinforced Earth ¥vall. Despite thatthe stability of reinforced ¥valls is usually threatened byrainfalls (e.g., see Kutara et al. , 1991), a proper drainagesystern around the wall tends to be optional, not obligatory, in the light of the current format of the desi**n andYabu city in northern part of Hyogo Prefecture in westJapan. The time of occurrence of the incident ¥vas quiteexact by the record of an emergency phone call from a10cal resident to Yabu local government office. Figure 1construction manual for this type of wall. Geotechnicalengineers have therefore been concerned with the shortterm stability of Reinforced Earth in the event of annualtyphoon attacks as they are constructed in a mountainousregion. Unfortunately, such a worry became a reality inshows a picture of the ¥vall failure that was taken a fe¥vmonths after the incident.The urgent matter that after required attention vas toensure short-term safety of neighborin*･ inhabitantsagainst occurrence of any further slope disasters.Accordingly, under the authority of Yabu city govern-the case study described in this paper.At around 1:40 am on 2lst of October' 2004, a hugelandslide involved vith a catastrophic failure of Reinforced Earth vall took place in the mountainous area ofi,ii)iii)Site after the collapse of Reinforced Earth wallrnent, comprehensive geotechnical site investigation ¥vascarried out over six-month period after the incident.Professor, Department of Architecture and C ivil Engineerin_ , Kobe University, Japan (sshibuya@kobe-u.ac jp).Associate Proftssor, Department of Civil Engineering, Hakodate National College of Technology, Japan.Gradua e Student, Graduate School of Natural Science, Kobe University.The manuscript for this paper ¥vas received for revie v oll May 9, 2006; appro¥'ed on N. ovember 17, 2006Written discussions on this paper should be submitted before September l, 2007 to the Japanese Geotechnical Society 4-38-2, Sengoku,Bunk.vo-ku, Tokyo I l'_-OOI 1, Japan. Upon request the closing date may be extended one momh.153 SHIBUYA ETl 54*+' ' - " )i' +*'"' rE;li Tl,] i [ l 0:. 'KOU ou ' "*'/ ::*= '+oo 20Cf' ': 1: ('"__50 oAL .::It::::' _ L: r ; :: : l- :;in---- awa-' -vvsar:ver -_ "'' 'Fi(g. 3.Cross section of the remainder of the lvallFig. 2. Topographica] map of tlle site immediatel¥. after the incidentSeveral key observations from comprehensive surveyper'formed immediately after the incident (Shibuya andIn addition, in an attempt to back-analyz,e properly theKa¥vaguchi, '_006) are:i)Parts of the ¥vall (i.e., concr'ete skins and metalstrips) reached to the end of debris flo¥v,stability of the collapsed ¥vall, a series of direct shear boxtests in simulating the mode of undrained shear of theii)foundation soil was carried out in the GeotechnicalEngineerin_2: Laboratory at Kobe University.In this paper, based on the results of geotechnical siteinvestigation, key factors responsible for the ¥vall collapse are manifested, and the scenario of the ¥vall failureis discussed in depth by performing a conventional stabil-iii)ity analysis ¥vith detailed soil profile and the stren*'th dataV)of the local soil.iv)Neither dama_,_"e of metal skins nor breakage ofmetal strip/concrete skin joints ¥1'as found,The remainder of the ¥¥'all stood in good shape,The metal strips remaining on the side ¥vall of ¥vallwere all inclined at an angle of 24-26 degrees fromthe horizontal that ¥vas equal to the supposed slipsurface an*"le on the foundation (Fig. 3), andRainfail ¥vater poured into the collapsed area duringrainfall.Regardin*' the remark iv), it lvas observed that theOUTLINF, OF THE WALL FAILIJREThe construction of the reinforced ¥vall ¥vas completedin the year of 2000, i.e., four years before the incident.Figure 2 sho¥vs a topographical map of the site sho¥vingthe condition immediately af'ter the failure of the vall.metal strips in the remained ¥vall aligned horizontally justlike the arrangement ¥vhen the ¥vall ¥vas constructed. Itshould be mentioned that the collapsed ¥vall ¥vas as highas 23 m. To the authors' best kno¥vledge, such a hu*"ecollapse as that of Reinforced Earth ¥vall has not beenreported in the liter'ature.The numbers shown in this figure refer to spots from¥vhere some pictures immediately after the incident weretaken in order to obtain any clues into the failuremechanism (Shibuya and Ka¥va_ uchi, '_006). The landslide took place over a length of about 150 m along theslope involved with the collapse of the vall over 80 mlength alon_ the road. It ¥vas obvious in the map that theslope over ¥vhich the wall failure occurred consisted of acouple of small valleys. Moreover, the road ¥vas inclinedabout 70/0 from West (right hand side in Fig )-) to East(1eft hand side in Fi_g:. 2). These topo*'raphical surround-RAINFALL RF,CORDAs mentioned earlier, the incident took place at 1:40am on 2lst October in 2004. Figure 4 sho¥vs the intensityof rainfall ¥vith time over three day. s befor'e and after theincident. It should be mentioned that the data ¥vasrecorded at an observatory ¥'ery close to the site. Heavyrain ¥vith the intensity in excess of 10 mm per hour con-tinued over eight hours (1 pm-8 pm) on 20th October.Note that the amount of 226 mm of rainfall ¥vas certainlyings ¥vould have brou*'ht about some concentration ofthe peak record over the past eight years in this region. Itsurface/_ round ¥vater into the collapsed portion of theroad durin*" the heavy rainfall.trig:9:er of the disaster.may ¥vell be postulated that this heavy rainfall ¥vas the 羅155FAILURE OF REINFORCED鷺ARTH塾ゆGξ ﹃ 蓬li纏護li髄際04110／19…1……馨筆顯ll， 照馨：コ？」『，一τ …尉：1竃菖 窯旧出［』甲．『9353界アo ） ℃ Φ↓…． i；，．li饒 ！liiiilii 罵瓢二5e3 のliU『 『p暁『9i 『iii難it の5G ① α、1鰭畷 t三1織隠1三諏嚢・η詰e，li鱒蕪葦04／10！2040 噂關『 ‘ ゆ訟 ］㊦P や〒門r讐酬 臼一Irr・叩■ r 71ε』甲liP， ：1：1：黙 ll……＝，2。3：：ll：設 甲 r卜乎昌一1 腰 甲』・…霞 臼 ・1eGヨ ロロコ の コTerre Arm6e Wali collapsed04110／21【01瓢，ili垂ii臨i臓にli湊揮匡搾 Grain size（mm）τ㎞εFines∈ンFig、6。Sa縞dGravelGra豆n size d韮str窪bu芝ion of so産夏α＝、． 、影コ奪．』』薦試葺誕ノ 轟1◇☆露Fig．4． R田ほfa畳l da瞼蜀＼ズ擁離爾 鐸糞謙藩毅鑛轟暴藩・灘1轡！購響罷響㌧』 ・萎鷲蒙蕎◎欝・ 匡嚢塾到Fig．7． Geo垂ecllnlcai si｛e韮nvesIigalion performedFig．5．CoロstrucIionseqロenceofthewa鍼er in order to secure prescr重bed friction between InetaIstrips an（nhe soiL As stated later， the soil stabilization●tyREINFORCED EARTH WALL COLLAPSEDtreatment has reduced the permeabiofiu−wallsoiltoaconsi〔ierable ex重ent． Figure 5 sho∼vs the sequence of cons重ruction of thiswa1正in the year of2000．Some features pertaining to thedesign and cons紅uction of芝he wa至1are su互nlnar三zed in theGEOTECHNICAL SITE INVESTIGATIONbelo∼v（Shibuya and Kawagucぬi，2006）：Soκ1π1in8i） Local geQmateri＆ls，1．e。，wea由eIled sllty so圭10rigi− The site is covered with heavily we撮hered soil origi− nate（i from yellow tu仔，with the丘nes con塗ent well innated from ye星10w tuff．Geotechnical site i煎vestigation excess of25％was employed for constructing theperforme（1is shown in Fig．7，The scheme consis塗ed of wal1，notillg that F圭9．6s紅ows t1｝e distribution curveSPT sou且ding and in−situ se圭smic survey to cover the of several samples from B21＆yer，survived as we至1as重he coilapsed portions of the wa1L Theii） Drain pipe with a small diameter of200mm wasSPT souuding a玉ong three survey lines from south to erllployed at t董1e bottom of the wa1正，but it did Ilotuorth involved with soll sampling by using the Japanese exten（i to cover an area behiIKI the、vall（5θθFig．5），thin−wall sampler．Spectrum aualysls of surface wavei圭i） The surface oぎthe road had been unpaved over the（SASW）（Stokoe et al．，1988）was＆lso carried out aξthe past four years，andsurvived parts of the∼v段n。iv） SPTノ〉一value隻n重he foundat重on ranged between15 and20，which was surprising星y low to supPor重the Crosssectionsoftkewalldepictedfromthesege− sollwallwith毛hemaximumheight of23m．Fig．8，the subsoils may be convenient至y characterized It should be meutiolled輩hat圭n the construction of thewal1，the IocαI soll was mixed with cement−based s宅abiliz一otechnic＆1investigations are showa in Fig．8．As seell lninto seve且layers as describe（I below： : F P's ' #SHIBIJYA ET AL.l 56a)E }EP }4e S EP NS 2ooeBP No 2L=15n20surf_'"' '-ilcer'** /(s3 /DL=140BF No 3!so= 'e JFd- _--*･,S･;;'ij;!2 i*II:;: i;;;Ge' s "I"rITT¥:_EP.1 ..- --- Y_# ;;1!!"YIT2 oi:4 oi ';::!{:{:::;:" "';SS"tB QOO 4a :le 200EOI*'2 fll DL='20 l"Z;,/'/.;:;;;::i;;:'::'_____4./-" ' ' '= '"i'':"'" '; //"' *' * /i ? / ･---///:'1i j!;{/;;:; ;t;::!;ji:':/"'1':; ;;;:! "i;lei " " """/ ; = ;;"'**S';*4* #^^i""i "_= ;"';;1"'TEs,# o ='s;o'2e oi2oo3PNOS - '"'* "*- 'N'v !u"f' #; - ; {)' 'j'*' :';' : ' "f"'-*-*'! "'*- 'o* **s o so oQ: '/' ;"" =:*._xp/"'Si=r ;'i"_";*;1'-_* .*_* .2eDKP-21I!so"; ;' ' ' ;;' ;"';';;i;';::;j L't5BP'No'4KP.3zs o 2s'o20KP's i b ): :e/:TS OEP F{O S1 iBP NS2;oo40Eo20 2 O 240 202 eo s o 400 4 o5 oDist r en tee 9iri)'Fig. 9.;";; '/' ""' '-Profile of shear wave velocit), from SASW* method ( 1'est side)iii) Foundation rock (W* -layer) ¥vith N>, 50.It is to be noted that the ¥vall rests on W*o-layer ¥vithN-value of 22 on avera9:e. It should also be mentionedC)BP'N0'7Q*' ' 'ls rfa :s' ! si r*/* e'!"* ' _1 ' l' ' #'' '#''/'( ; /';* B2 f '1 s't' '- : / '#x # ; ; ;i::( ;;!! ;; l;::;:';;:/ ! _';;:1;;;;:(;:!:! ;i!""'"i;t;';:: ;:;;' '1;;:i:;,: :;;!; ';/ ''_ /// ;'! W "W:/ _;iiSi;' ' 'i/#'e_ # ^i"!; ss##ss': i ;,,:'/;:''; :;1:IIll(: (1;;,:;::;1::!;:,: ' #; ;: i#$ $ '/ ;i'l:,::, .; ;;;j:(: :::;;::f i :" ;#s!/"'# i/i ; t'; ' ;" /''. f-#:;i"/ F**'-/'; ;"+**'+./- ' *'.'r -' ' :;' ;iiflli gre ;Fti /'e r''l*/on lit ¥vas smaller by one order of ma_g:nitude in the roadembankment (i.e., B1, B2 and B3 Iayers).!';;' ;LS ' 30m"":: ,!1:;;;;/'; ;i,!/'that the permeability from in-situ test ¥vas in the order of105 (m/s) for ¥veathered rock layer (W,o-Iayer), ¥vhereasDL* 2iPSpectrull7 A na!ysis of Sulface Wave (SA S W)SASW survey is a non-destructive method by ¥ 'hich theprofile of shear wave velocity, V*, ¥vith depth is easilymanifested down to the depth of about 20 m. Figure 9Q =tlOFT1Fig. 8. Cross section of the wall: a) Ivest line, b) central line and c) eastl inesho¥vs the result of the survey performed at west end ofthe remainin_g wall (see Fi_9:. 7). In this figure, the N-valueestimated using the following empirical expression is alsosho¥vn for comparison.Road E/7lbankl7lenti) Surface layer (B1-layer) with the SPT N-value rang-ing from I to il (N=5 on average), non-uniformand the fines content ran*'ed from 30 to 800/0,ii) Improved layer (B2-layer) with the SPT N-valueN= (V, /b)* (1)¥vhere the constants, a=0.314, b=97 (m/s) were employed (Imai et al., 1975).The follo¥vin*" may be noted:i)The shear ¥vave velocity, V , ranged from 150 mls to360 m/s as examined do¥vn to depth 20 m,ranging from 15 to 18 (N= 16 on average), relativelyuniform and the fines content ranged from 31 to460/0 ,ii)The profile of estimated N-value using Eq. (1) is simi-lar to the measurement, indicating that the N-valueof weathered r'ock (W*o-layer) is far less than 50iii) Behind the ¥vall layer (B3-layer) ¥vith the SPTN-value ranging from 2 to 5 (N=4 on aver'age),non-uniform and comprising *"ravel-size particlesThe efficacy of the SASW method ¥vas well demon-about 30-400/0 by lveight, andiv) Base layer (Fj-layer) with the SPT N-value averagestrated in this investigation that it provided 2-D picture ofN-value profile ¥vith depth, from ¥vhich the soil layeringof 17.Sulface Soi!lFouncJationi) Surface soil (D*-layer) ¥vith the SPT N-value rangingfrom 3 to 5 (N=4 on a¥'erage)ii) Weathered rock layer (W*o-layer) ¥vith the SPTN-value ranging from 5 to 50 (N=22 on average),t,hroughout the layer.shown in Fig. 8 ¥vas determined ¥vith reasonable confidence.I,abol'atoiy Sllear TestsTwo kinds of laboratory tests ¥vere performed in orderto obtain soil strength in use for back-analyzing the ¥vallfailure. In the first place, a ser'ies of unconsolidated-and a clear trend of N -¥'alue to increase ¥vith depth,undrained triaxial compression tests (i.e., triaxial UIJandtest) ¥vas carried out using intact samples fr'om different FAILURE OF REINFORCED EARTH157lable 1. Soil propertiesBulk DryDepth density densi .¥'GL-mp(g/cm3) (g/cm3)* PNatu,alSoilparticle¥vater ¥roiddensitycoment ratiop.(g /cm3)De ree ofsaturarione( ',S,(c)( 1O)55 _0-5 .7 1 .83 1 2 38.73798 . 5l .322107 l1 06495 ,, 97 .O8 .O I . 8 1 6 1 . 32 1 37.42 . 7272I .2050-2.6 1 .6342 .7 1 635.71261 77.6l .4683.03_7 1 .888 2.768 ･8 7 0.887 89 7O. 5 1 .723 l 2. 203.708 43 .2 1 .25 1 93 .5Table 2. Results of triaxial UU testBulk densiSoii layer p* (g/cm;)B2 and Fl.8Bl and B317Dt¥l .6181 r(TTotal stressc (kPa) c ( ' ) tan c;1;: Oirect46.3 7.77 0.136rive mator for horizont i !o68.0 o.0643,66, _f'l.T Load cell for ver ie ! Ioadirig* ' ,:Str in ampiifier08rd* "+.S :A/D board36.4 12.0S O.214Fig. 10. Direct(T cos- aNote that the soil samples from not only embankmentvas 46 kPa and 68 kPa for improvedlayer (B2) and unimproved layer (B3), respect.ively.Secondly, t¥vo series of constant-volume direct shear. 4;i;¥a10 shows the direct shear box apparatus developed atHokkaido Uni¥'ersity (Shibuya et al., 2001). The loadcontrol as well as data acquisition is fully automatedlear box apparatUS= 250h--'A(1 eosa sLnaW cos a: Crv COS2 aA!cosa' VH WIAwsinaAwco j f'I'lf""I w cosa//box tests ¥vere performed using reconstituted samplesretrieved from the slip surface. A block sample ¥vas firstprepared from the slurry with the initial ¥vater contentapproximately equal to liquid limit (i.e. , ,50600/0). Figure: petsen l oomputer7+.. L Linear rol{er waybut also the foundation were all close to full saturation.As a result, the angle of shear resistance c from triaxialUU test ¥vas small ¥vith the values less than 10 de*"rees., Load cell for hori2:ontai loading"4*.',: Qrive unit for vertieai ioadin' j,: Siiding uni41 .9 1 4.96 O.267:* : Shear hox('=9_. I Water containerin'-:)C*: Se aldepths. The results are sho¥vn in Table I and Table 2.The cohesion, c,ing2==: Qriv$ unit for herizont l lo ding'3,.*: Oirect drive motor for vertic l !oarW sinaA!cosa = (TV COSa sin aAFig. 11.Stress conditions a[ong the slip surface¥'it.han aid of PC. The nominal dimension of the specimenfor the long-term and short-term stability analysis,was 6 cm in diameter and 4 cm high. The gap between therespecti¥'ely. In the second series, in-situ stress conditionsupper and lo¥ver shear boxes ¥vas maintained at aon the collapsed slope were more closely sirnulated inconstant value of 0.5 mm during shear, noting the meandiameter of about 0.1 mm for the soil tested. The soileach sample by applying initial shear stress under draineddensity¥'as I .7-1 .8 g/cm3 bein*' very close to the in-situdensity.Regarding a sketch sho¥vn in Fig. 1 1, three samples inthe first se 'ies ¥¥'ere each consolidated to the verticalconsolidation stress, (T.* of about 200, 300 and 400 kPa,respectively. After'wards, the samples were sheared underconditions (refer to Fig. 11). In general, in-situ soilelement on a slope ¥vith angle ai from the horizontal issubjected to the initial stress conditions as sho¥vn in thef ollowin*";(Ti = (T.* cos2 ci = ((2), cos a sin a (3)constant-volume conditions by using a constant rate ofFigures 13 and 14 sho¥v the z'esults of five tests perforrnedhorizontal displacement of 2 mm/min. The undrainedin the second series. As can be seen in Fig. 13, eacheffective stress paths of this conventional consolidatedundrained (C*U) test are shown in Fig. 12, in which thesample was fir'st consolidated to a prescribed initial (andvariation of normal ( =verticai) effective stress is plottedstrength paramet.ers of (c' , c') = (O, 37.4'), together ¥vith25'), where the angle of 25' corresponds to the averagedangle of' the collapsed slope from the horizontal (seeFig. 3). The sample ¥ 'as then subjected to application oft.he tot.al stress parameters, S /(7.*=0.34drained initial shear to the ¥'alue of ti = 1 1 5 kPa ( = 300 xa*'ainst the horizontal shear stress, T. The effectivevere obtainedcommon) ¥'ertical stress of (7i=246 kPa (=300xcos2J SHIBUYA ET AL158I OOOOm inip' = 37.4'2003000minlOOmin200Ca)ip' = 37.4 'l Om inl m inl 1 5kPap)S" jOO*+.*' i; 100;.*Cl *l:19oo200I OOoo400300200l OO400300Normal stress. a(kPa)Norrna] stress, (7(kPa)Fig. 14. Undrained effective stress paths in direct shear box.' test vithb)en 200*c$ Le".'? 'ce)initiat sheaFlO.34!OO7300te209 kPac:s:':S OolOO 200300400 500b 200pNormal stress, (r(kPa)S*, = 4.88 In(t)+138 i"Pi('.12. Resu]ts of conventional direct shear test: a) effective stresspaths and b) undrained shear strength" 100I"4 _vears later i:)200Ol OoTim e.c:; 150:lOl Ot ( 111 i4Fio*. 15. Undratned shear strength versus duration of1 1 5kPainitialshearstress appliedJ"?) 100l 06)coristant shear stress":(3000min)* '50In itial shear i Reshearconsequence, the undrained shear strength S (i.e., themaximum shear stress) also increased ¥vith the sustainedperiod of initial shear stress. On the other hand, theI(constant stress) , (constant ¥'olume)oo,Horizontal disp lacement (mm )effective strength parameters of (c', c') = (O, 37.4') ¥1'erenot affected at all by the application of initial shear (referto Fi*･. 12). The significant softening behavior observed inthe second series suggests strongly that a catastrophicvith initial sheartype of failure ¥vould take place once the foundation soilexceeds the peak strength.Figure 15 sho¥ 's the S value in the second series whencos 25' sin 25') by using a slo¥ver rate of horizontal shearexamined against the sustained period of initial shear.Fig. 13. Relationship bet veen t]orizoutal shear stress and horizontaldisplacement in a testdisplacement of 0.0'_ mm/min. The initial shear stressBearing in mind that the ¥vall collapsed at 4 years after thewas then maintained constant over a prescr'ibed period ineach test. At this initial shear stage, the volume change ofthe sample ¥vas insignificant ¥vhereas the horizontal sheardisplacement developed as much as 0.2 mm (see Fi**. 13).construction, the value of 209 kPa for (T *=300 kPa,hence S./cr ,.=209/300=0.70, ¥vas attained by extrapolating the S ¥'alues from the laboratory test to aninstant after 4 years.The sample ¥vas finally sheared to failure under theconditions of constant volume by using a faster rate of2 mm/min. The initial shear stress was maintained overdifferent, but fixed, periods of 1, 10, 100, 3,000 andSCENF,RIO OF THF, WALL FAILURE10,000 min, respectively. Surprisingly, the effective stress_ :eotechnical investigation and comprehensive re¥'ie¥v ofpath ¥vas very much influenced by the duration of thedesign and constr'uction scheme of the ¥vall, itinitial shear stress application, showing that it rose moreconcluded that this particular ¥vall ¥vas properly designedand constructed in the light of the available "design andsharply as the duration increased (see Fig. 14). As aBased on the field observations, the results ofvas FAILURE OF REINFORCED EARTHsurface waterR=57.50m !embankment(Y=18kNlm3) Wslna W: Su:159surface was carried out by using the strength parametersfrom triaxial UU test and constant-volurne direct sheartest. Fi**ure 16 sho¥vs the short-term stability analysisperformed at the centr'al portion of the collapsed ¥vall(see Fig. 8(b)). The surface ¥¥'ater level ¥vas postulatedbased on in-situ measurement that ¥vas made immediatelyafter the incident. The results of back-analysis are sho¥vnin Fig. 17, in ¥vhich the back-calculated factor of safety,F*, is plotted against the total stress strength pararneter,S** IcT... Note that F, is close to unity (i.e., F, = I . 1) ¥vhenthe S. /(T.. ¥'alue of O.70 is employed, ¥vher'eas F= ¥vas farrock foundationFig. 16. Short･term stability a}lalysis,ldirect shear test is used for the calculation. The resultstrongly suggests that ¥ve should use soil strength fromdirect shear box test in vhich the magnitude as vell ashistory of initial stress conditions on the supposed slipsurface are closely simulated in the laboratory. In thestability analysis performed, it ¥vas assumed that the soilbehind the wall ¥vas saturated as a consequence of heavyrainfall over a short period of time. The effect of65 11,concentrated rainfall on the ¥vall stability ¥vas manifestedin the fact that the F* value ¥vith dry soil (i.e., S*=00/0)I.l) 08o 54 _104:o.7: o.34O O 2 O_6 O 8 lOO.4Su / C;:*Fig. 17. Back caiculated factor of safet .' Ivith S*/(T,*construction manual" (Ci¥'il Engineering ResearchCenter, 2003). However, it is the fact that the ¥vall faileddue to the heavy rainfall.Theless t.han unity ¥¥'hen S la., of 0.34 frorn con¥'entionalvall failure rnay be attributed to simultaneousoccurrence of sever'al, not a single, causes as listed belo¥v:i) C*oncentration of in-soil seepage and surface ¥¥'aterflo¥ ' into the collapsed area,ii) Relatively lo¥v permeability of embankment (BI , B2and B3 Iayers) as compared to the ¥veathered rockfoundation (W*o-layer) (see Fi**. 8),iii) Poor drain system behind the ¥vall in particular',iv) Lo¥¥' bearin*" capacity of the foundation, andv) Softening characteristic of the foundation soil assheared undrained (see Figs. 13 and 14).behind the wall ¥ 'as far greater than unity.Regarding the sketch sho vn in Fig. 18, the scenario ofthe ¥vall failure could be described as:i) A great deal of in-soil and surface water poured intothe collapsed area over a short period of time,ii) The ¥vater infiltrated into the embankment andgradually stored behind the v¥'all since thepermeability of the vall ¥vas relatively small,iii) Total load increased due to the ¥vater infiltration,i¥') Seepage lvater pressure in the ¥veathered rockf'oundation ha¥'ing relatively high permeability Increased gradually,¥') The overall stability of the embankment reducedsubstantially due to the vater storage in and behindthe ¥vall, together with possible development ofseepage pressure in the foundation soil,vi) The localized failure on the foot of the wall mayhave occurred due to the lack of' bearing capacity,andvii) A type of circular slip occurrcd across the foundation.The wall failure as such could be described simply as"the undrained shear failure of' foundation since the ¥vallacted as if a reservoir dam in the event of heavy rainfall" .It should be stressed that the first three possible causesFinally, it is strongly recommended that the design andconstruction manual should be revised properly so as tohave something to do with problems of in-soil seepageflow. As stated earlier, accordin*' to "design and con-prevent any future occur'rence of this type of failure. Thecase st.udy described in this paper also suggests the stron*'struction manual" in Japan like in other countriesneed for co-operation bet¥veen structural engineers andgeotechnical engineers.perhaps, any existence of water/water flo¥v is not considered at all in the design of the ¥vall. In fact, ho¥vever,rainfall water invaded the reinforced embankment in thiscase study. It was confirmed ¥vith the result of fieidobservation that the de*'ree of' saturation of the collapsedCONCLUSIONSThe Reinforced Earthvall that collapsed ¥vas properlyembankment soil ¥vas near'ly equai to 1000/0 ¥vhen ex-designed and constr'ucted in the light of "design andamined right after the incident.The short-term stability analysis assurning circular slipconstruction manual" in Japan. Unfortunately, it ¥'as afact that the wall failed during the hea¥'y rainfall as SHIBUYA ET AL.l 60Rainf i]l;:zi_.__Heavy rainfall by typhoani ' 7 7_v y'tf ;e' v1] hti: t::iff;i1(! Ll:Infiitratin of water from unpaved road ' l'//."'/' l"Embankment w th felatively-*S4- $4_# y:_; - .iow pe leability (i xi 0-7-5 mfs)Jl'.- Ctiff with TelativelyJl " ' - high Pe meability) /.____ ･"_ _ $_ y S'- - /'.'#;'.i'i^^- SSS(1xlO-5m/s)Cement-mixed soils/// ' Soil in embankment saturated/ '..";./;:>/ ; :/ i '(-$;?< ;''" ' ; {- )$ J/.･... ..*'"ri;Loss of bearing capaoity dueto seepage fiow/increaseof sustai'l t/' , ;;: :;' ';. !,;;;';;;''i. c:'.'*.(j:;*:*' ;i"-';' ""' :; ;' I r'; ' Instability of:;' ;"';_;'.;,' ';'. ';;'. "i;,;<,:,.';.! ' ',...", ";"'; "<,"'; ;,Block of. : 'ow to increasewate¥,,c!)SeepageFig. 18." embankment' // ;,'::{i :i '; j JCircular sliplevelof ground waterSeenario of the wa l fai!ureattacked by Typhoon No. 23 in October, '_004.Field obser¥'ations immediately after the incidentsimulated, and¥') Construction of this type of Reinforced Earth ¥vallcoupled ¥vith the result of the stability analysis corroborated the premise that the ¥vall itself stood in a good shapeneeds sound co-operation betlveen structural eng:ineer's and g:eotechnical en9:ineers.till the moment of the catastrophic failure. The ¥ 'allfallure in this case study could be described simply as"the undrained shear failure of foundation" since thewall acted as if a reservoir dam in the event of heavyrainfall. Simultaneous occurrence of several causes suchACKNOWLEDGEMENTas concentration of in-soil seepage and surface water fio¥vcity chaired by Professor Makoto Nishigaki, Okayamainto the collapsed area, Io¥v permeability of embankment, poor drain system behind the ¥vall, etc. ¥ver'esupposedly responsible for the failure. It is thereforerecommended that the design and construction manualshould be revised properly. so as to prevent any futureUniversity.occurrence of this type of failure induced by heavy rainfalls. In so doin*', every effort should be made to preventwater from seeping into and near the ¥vall.Other lessons learnt from this unique case study are:i) Drainage system should take care not only the ¥vallbut also the embankment behind the vall,ii) The wall should be placed on rock foundation lvithSPT N-value more than 50,Most of field data reported in this paper is referencedto the report issued by the technical committee of YabuREFERENCES1) Civil En_ineering Research Cen er (7-003): Desigll (z,Id Corl,structionMan!la! of Reinforcec! Soi! ,"t7!l !Vle[hod (in Japanese).2) Imai, T.. Roku. H^ and Yokota, K. (1975): Rela ionship bet veenshear ¥va¥'e velocity and mechanical properlies of Japanese soils,Proc- 5!/1 S.vn7p. Eartllqtrake Engineering (in Japanese).3) Kutara, K.,,fiki, H., Nakayama, K. and Fnjiki. H_ (1991):Beha¥*ior of prototype s eep slope embankment having soil-¥vallsreinf'orced by continuous fibers, J. Coilstruction IVlanagemen! (vrdEngineering. JSC_E, (4,_7, ¥rl-14), )_23-237_ (in Japancse)4) Shibuya, S , ¥. ,iitachi, T., Tanaka, H , Ka¥vaguchi, T. ar d Lee. I. h,J(2001): Measurement and application of quasi-elastic properties iniii) The surface ofthe road should be temporarily paved_ eotechnical site characterisation, Tllen7e Lecrure. Proc. Jlrh Asianeven in the course of construction by ¥vhich infiltra-Regiona! Conference on SMGE, Seolrl, Balkema, 2, 639-710.5) Shibuya, S, and Ka¥vaguchi, T. (2006): Lessons learnt from ation of surface ¥vater into the surroundings of thewall may be grossly lessened, andiv) In short-term stability analysis of the ¥vall involvin_",_cataslrophic failure of terre arm6e val due to heavy rainfall,Geomechanics II. Proc. Second Japa,1-U_S. ,Vorkshop 0,2 resting1lfoc!eling and Sinuda!ion in Geon7echanics, ASCE, Kyoto, 454-470the case of rainfall attacks, it is promisin_9: to employ6) Stokoe, K,, H , Nazarin, S., Rix, G. J., Sanchez-Salinero. I., Sheu,soil strength from direct shear box test, in ¥vhichthe ma_gnitude as ¥vell as history of initial stressconditions on the supposed slip surface are closelysoils by surface ¥vave method, Eallhquake Engineer'ing and Soi!D_ *namics II. Recen! Ac!vances !n Gr'ound !V[o!ion E1'a!uation,J. C. and ¥,Iok, Y. JASCE, 264-278.(19S8): In siru seismic testing of hard- o-sample
- ログイン
- タイトル
- Design Parameters for EPS Geofoam
- 著者
- D. Negussey
- 出版
- soils and Foundations
- ページ
- 161〜170
- 発行
- 2007/02/15
- 文書ID
- 20988
- 内容
- SOiLS AND FOUi¥'DATIONS Vol47 .No1161-170, Feb_ 2007Japanese Geotechnical SocietyDESIGN PARAMETERS FOR EPS GEOFOAMD. NEG*USSEYi)ABSTRACTOver the past 30 years, design vith geofoam has been based on either factored strength or limit strain approaches.Geofoam parameters for design ha¥'e been derived from unconfined compression testing of small laboratory samples.Closer examination of performance observations indicate extrapolation of small sample laboratory results can lead tomisleading interpretation of field results. The potential for creep deformations is exagger'ated and design modulusvalues are underestirnated ¥vhen based on small sample laboratory tests. Possible reasons for these shortcomings, inreference to field observations, are examined on the basis of creep tests on small samples, uniaxial loading of' Iar*'esamples, comp*ession tests using tactile pr'essure sensors and revie¥v of enlarged images of geofoam surfaces. C reepdeformations in geofoams under uniaxial loadin_g: remain mainly in primary stages where strain rates continuallydecrease. Modulus values for design that are deri¥'ed from small sample laboratory tests are about half of the valuesthat ¥vere estimated from field observations. Accordingly, the sug:gestion is made to increase small sample basedmodulus values from laboratory tests for design applications.Key words: compression, creep, deformation, elastic,geo f 'o am ,modulus, polystyr'ene,strain, stress, tactile sensor(IGC: K14/M9)density geofoam is taken as 100 kPa to provide up to 30INTRODUCTIONkPa allowable stresses from surcharge loadings. Thisdesign method constitutes a factor'ed strength approachbased on correspondence bet veen density and strength.The first documented use of EPS (expanded polystyr'ene) geofoam as light¥veight fill occurred in Nor¥¥'ay overTo allo v for ¥veight increases due to moisture pick up inser¥'ice, design densities are increased to 50 and 100 kglm3 for installations expected to remain above and belo¥v,30 years a*"o. The reconstruction of the approach fill toFlom Bridge, near Oslo, is a significant milestone inlight¥veight embankment construction (Frydenlund,ground ¥vater, respectively. These density adjustmentsare adequate to compensate for ¥veight increases due tomoisture absorption under field conditions (Esch, 1995;Frydenlund and Aab e, 1996). For buoyancy considera-1987). The motivation for the application ¥vas to betterrespond to the cycle of settlernents and grade adjustmentsof a road¥vay supported on ver'y compressible soil foun-dation. The top surface of the geofoam fill was coveredtions, the actual 20 k**/m3 is used without adjustment orthe geofoam ¥veight is neglected. A friction coefficient of¥vith polyurethane spray and the overlying pavementstructure ¥vas only 0.5 m in thickness. Under estimateddaily traffic of some 15,000 vehicles, the road sectionperformed ¥vell and settlements0.5 has been assurned for geofoam to geofoam andgeofoam to soil or concrete interfaces. The practice ofpro¥'iding the equi¥'alent of two double sided timber¥'ere *'radually arrested.Geofoam blocks installed in 1972 ¥vere recovered andreused when the road¥vay ¥vas reconstructed by 1996.fasteners per block bet¥veen geofoam layers was introduced in Nor¥vay and has become ¥vide spread. Forpurposes of pavement design, a modulus of 5 MPa hasbeen assigned for geofoam subgrades. Actual modulusVisual inspection and laboratory testing of samples fromthe exhumed EPS blocks further confirmed the durabilityof **eofoam in service and under conditions of periodicflooding. The design approach developed in Nor¥vay forthis project and many more that follo¥ved continues toinfluence practice around the world. Mainly, the allowa-values from project specific tests have not been requiredfor' design or product qualification.In the rapid and innovati¥'e development of **eofoamapplications in Japan since 1985, a design process hasble surcharge load over geofoam fill is restricted to 300/0of the compressive st.rength at 50/0 Strain as determined bylaborat.ory testing of small size samples at a strain rate ofevolved ¥vherein stress at a limit lo/o strain has become aworking load criterion (Miki, 1996). The behavior' ofgeofoam belo¥v lo/o strain has been considered to belinear elastic. The design standard adapted in Japanprovides a 50 kPa allowable compression load for 20 kg/100/0 Per minute (Frydenlund and Aab e, 1996). Themost commonly used density variety has been 20 k**/nf.The nominal design strength at 50/0 strain for 20 kg/m3i' Director, Geofoam Research Center, s)*racuse Universit)*, Syracuse, NY 13244, USA (negussey@syr.edu).The manuscript for this paper ¥vas received for revie v on August 22. 2005; approved on August 29, 2006¥¥rriuen discussions orl: this paper should be submitted before September 1, '_007 to the Japanese Geo echnical Society,Bunkyo-ku, 'Tokyo I i?_-OOI l, Japan. Upon requesl the closing date may be extended one monih.1614 3 8 2 ,Sengoku, l 62NEGUSSEYm3 density *'eofoam and thus the same modulus of 5 MPa25Q .as ¥vas previously assumed in Nor¥vay. Allo¥vable stressesto a lo/o strain limit remain below half of the r'especti¥'e33 kg!m20ecompression strengths at 50/0 Strain. Ho¥vever, as thestresses under a limit strain criter'ia account for bothsurcharge and live loading, the t¥vo desi_9:n approachesIse -IQe -developed in Nor¥vay and subsequently in Japan arecomparable (Ne*'ussey and Sun, 1996). In the latter>50method, the essential correspondence is bet¥veen densityoand modulus. Modulus values of the order of 10 MPaand Poisson's ratios generally in the range of 0.1 andlo¥ver have been assumed in analy. ses for geofoam of20 kg/mi density (Hotta, 2001). A slightly higher frictiono264Vef eal Str in (810)Fig. 1. Unconfined compression of 50 mm geofoam cubes of 12 and33 kg/m3 densitiescoefficient of 0.6 has been in common use in Japan for>"eofoam to geofoam and geofoam to soil interfaces.Also, Iarger (150 by 150 mm) double-sided fasteners areused instead of the smaller (100 by 100 mm) size ty. pes2eo lstr3;r r B = 10earlier introduced in Nor¥vay. The design procedureintroduced in Japan enabled consideration of deforma-200 *iJfo*i 1Ts Isotion or perfor'mance cr'iteria.o'Shear demand at *･eofoam interfaces from live loadingdue to vehicle stopping and acceleration is lo¥v (Sheeley,yeQS Sx *3 04A: = O 9e1*･'** vBrtie 1 s: in5v eal st irly = 7 4o*x - 41sOYee1 st iT,3F " = O eS1> 50x * 21 52:o lO Q5lD1ostrengths, their use in practice is not common. Residualfriction coefficient values of 0.5 to 0.7 have so far beenhigher friction coefficients as compared to geotextiles andper1202000). Although statlc geofoam to geofoam interfaceshear stren9:ths are hi :her than residual interfaceadequate. Ho¥ 'ever, ¥vhy geofoam interfaces develop50 r m cvbe 5 mpies240 ls201025soss40Derl S ty {kOfTn:}Fig. 2. Strength gnin at 1, 5 and 1001!o strain levelsgeofoam densitylvith increasinggeomembranes is not vell understood. Althou'h reported to be unnecessary (Sheeley and Negusse}.', 2000),12 ldouble sided timber fasteners and similar proprietary10 JsPldevices continue to be installed bet¥veen geofoam layers.Capping of _"*,eofoam fills ¥vith concrete slab for loads:i*! i10s;6-distribution and protection continues to be a commonpractice. Apart from minor differences in sample sizesJi':(e*D *F te{}2]and shapes, design practices in other' countries generally.follo¥v the state of practice developed in Nor¥vay andO.Iapan. The aforementioned geofoam proper'ties havebeen used for different geotechnical applications (BASFPlastic.s, 1998; Negussey, 1997). Poisson's ratio valuesattributed to geofoams, the infiuence of confining pressures and effects of temperature on geofoam performancehave not been closely investigated. The latter propertiesand effects are generally not important for common near5'o1 S 20 2DBr s :･oTF.s'f *}Fig. 3. Modulus values for different densities of 50 mm cube samplesofeofoam100/0 strain levels and geofoam density are as sho¥vn insurface and belo¥v ground installations of geofoam.Geofoam desi**n parameters and behavior re*"ardin_*'stren*'ths and moduli ¥vith density as well as cr'eepphenomena are of more practical significance and areFig. 2. Differences bet¥veen strengths at 5 and 100/0 Strainconsidered herein.geofoam densities are sho¥vn in Fig. 3. The data fromdifferent sources are for 50 mm cube samples tested at100/0 strain per minute. These results indicate modulusUNCONFINED COMPRESSION AND DENSITYThe geofoam base material or resin price closely follo¥vs the trend of oil futures and the cost of EPS blocksincrease with density. For large volume applications therecan be considerable savin*'s from specifying a lowerdensity geofoam. As sho¥vn in Fig. 1, it is clear' that boththe strengths and moduli of geofoam increase ¥vithdensity. Relationships bet¥veen limit stresses at 1, 5 andare relatively minor and both the 5 and 100/0 straincriteria have been used in factored strength design procedures. Initial moduli to lo/o strain and ¥vith inc.reasingvalues for geofoam, as a function of density, determinedby testin*' specimens of the same nominal dimensions, atthe same strain rate are reasonably reproducible ¥vithin+ /- 100/0. Provided the manufacturing process andfusion quality are good, density is a consistent indexproperty for strength and modulus as desi**n parameters. DESIGN PARAN,1ETERS1631dsn5Tty = 20 h =meSO rE Tt c }c s nl9?kPaj Ya5tr* : 1+00? S1 -ol{Q¥j l ** S¥･ It23*-SeJ:,a {?Q* 29>e3s,a t Qof stf : s T5gP{70-C- 4g Pa {sG' - 23Pa {sQ*:*e LF a)- - S ,,pa (Se j2* -Gap irnsest ¥1_)1 E 3s 3 F? }C3CLfSSS¥ ' _LPC;O'stre:1 tn- tr;: ¥ 1 ,I , e : sL･+ in1 E*Qstr; n-05¥¥S;1:; prm3rys ¥¥¥¥1+:er'*=3ry* F-esOO.CeO-yeenYent 2*i x}n} C:fe P st { ; esF )7O eO1 o ol O I10 IQO IeQeO COOI O ODI O O1O1T 1TILrne (d ,s)F'ig. 4. Creep strain developments in three geofoam samples stdifferent stress levelsThe main rationale for limiting allowable static pres-10oO1 ee ySFig. 5. Creep strain ratcs for geofoam samples of 20 kg/m densityand t)pical creep stagesseoCREEP BEHAVIOR OF GEOFOAMiJsso Jn!en r 9c eompr ssones../30 4 k !m: (0=?s 2 n :TI H=s1 35 lscoosures to 300/0 of strength at 50/0 strain or total stresses to'I3eo l10/0 Iimit strain has been to minimize potential creepdeformations. The behavior of geofoam is assumed to beelastic and deformations to be tolerable for ¥vorkingstress levels consistent with these criteria. Figure 4presents results of creep tests frorn thr'ee 50 mm cubesamples of nominal 20 kg/m3 density geofoarn. Each testsample ¥vas subjected to almost 2 years of sustainedunconfined compression loading of '_9, 49 or 68 kPa.These load levels correspond to about 30, 50 and 70010 oft.he unconfined compression strength at 50/0 Strain forspecimens of the same nominal dimensions and density(Sheeley, 2000). Initial strain of 0.5, 0.8 and 1.50/0developed on application of' Ioading at the respectivestress levels. Additional deformation of about 0.5. 0.6and 200/0 developed over the 2 years of creep loadingperiod. The extent of creep deformation ¥vas especiallyacute for the higher loading at 700/0 of the unconfinedt250JJ "t'52e,1 l''IEtfils5JL/!150$:tt:l/leoooO 2SO10Vattic ! S:t40eOTo:n (Fig. 6. Unconfined compression loading and unloading of 30 kg/m3densitlgeofoamreduction in loading or stress intensity, secondary andeven ter'tiary stages can re¥'erse back to primary. Thecreep deformations of geofoam remained in primary ordecreasing strain rate mode for all loading levels even asaccumulated st.rains exceeded 100/0, as in the case f'or the700/0 Ioadin*'. Continually decreasing strain rat.es implystrain increments diminish ¥vith time. This is furthercompression strength. Both the 30 and 500/0 Ioadingsubst.antiated by results sho¥ 'n in Fig. 6 Ivhere, underconditions resulted in creep strains in addition to theunconfined compression, geofoam continues to stiffeninitial or immediate deformations. The results sug:,_*aestand gain strength ¥vith plastic strain instead of approach-geofoams develop both elastic and plastic strains under10ading to lo/o limit strain. For 700/0 Ioading or ¥vhatin*' rupture. On unloading and re-loadin*', the proportional limit increases lvith accurnulated strain. The resultswould amount to a stress state above the presumedsuggest controlled pre-stressing of **eofoam fill can beproportional limit, 50/0 strain developed in 3 days and upto 200/0 strain over 2 years of constant. Ioading. Such largebeneficial in reducin*' initial deformations vhile improving the allo¥vable working stress range. This observationcreep defor'mation observations encouraged the practiceof setting strict limitation on allowable ¥vorking stresslevels in geofoam design.is for a higher, 30kg/m3, density geofoarn and lo verdensity geofoams tend to develop softer' reloadingmodulus (Elragi, 2000) but continue to strain harden andthe test results sho¥vn in Fig. 4. Depending on the sustained load level, common materials deform in stages ofstiffen. The iaboratory test results suggest creep deformations occurred at all load sta*'es but will tend to eventuallycease without inducin_9: shear rupture, regardless of theprimary, secondary and tertiary creep to ultimateamount of accumulated strain (Negussey and Jahanan-rupture. In the primary stage, strain rates continue todecrease while in the secondary, the strain rates becomeconstant. With time, secondary creep can t.ransit to atertiary stage of increasing strain rates and ultimatedish, 1993; Elragi, 2000).Figure ,5 presents the creep strain rates associated ¥vithrupture. Reducing creep strain r'ates in the primary stageimply continuing stability as in one dimensional compression loading of soils. Secondary creep is a transition stage¥vhile tertiary is a precursor to ultimate instability. WithFIELD OBSERVATIONSField monitorin*' of high geofoam fills at the I-15reconstruction pr'oject in Salt Lake City (Negussey et al.,2001; Bartlett et al., 2001), the NRRL (Nor¥¥'egian RoadResearch Laboratory) test embankment and accom- NEC.USSEY164Ti lS [O;yS;a 2Qe 250 4Qe 4SO505e･Q *cJ'20 *-l OO- I e4..... , . _ :; 41$1S･･･Fe ,S ,rS!S .:S:i*1 Oe tr:1 : tieS !*20 '11 - FteSS fe eeit "sf:rSe T-30･140 -25 *,:1' f :_' / deS -- 10:> O30 -S50Q'Ps1 s', s20 *15 *ID *"e:er S$"I-Se -S . O *70$Q r･ t e;; se,Itc Q O 50O 25'(Negussey et al., 2001)teeO1 2s,5v rt:ee: Str- e -Fig. 7. Loadi rg and deformation of a large geofoam embankmenteo)Fig. 8. Geof0 m deformations f rom labresultandfieldobservation(Negusse¥.' et at., 2001)panying field monitoring (Frydenlund and Aabc e, 2001)indicate development of limited creep settlements. Figure7 presents data from the long-term monitor'ing progr'amat the 100 South Street crossing of the 1-15 project(Negussey and Stuedlein, 2003). T¥vo duplicate sensortaken after the 150 mm thickness concrete load distribution slab ¥vas poured but prior to placement of the I .2 mpavement section. As construction of the pavement overthe load distribution slab began, settlements due to gapsets of base pressure cell and extensometer column at 14m separation represent the Nor'th and South instrumentclosure bet¥veen *"eofoam block layers occurred. Thearrays. The pressure cells installed belo¥v the geofoam fillfield observations are associated ¥vith such gap closur'es.Whereas the typical initial lag of the stress-strain curveregistered the construction loadin*'. Deformations ¥vereinitial lag evident in the stress-strain results derived frommonitored with ma*"net extensometer plates iocatedfor the small size specimen under uniaxial compressionbetlveen the natural subgrade and the geofoam fill andbetween rigid metal platen is commonly attributed to nonuniform contact interfaces or seating error at the earlystages of loading. Beyond gap closure and seating erroreffects and as loadings pro*"ressed, the highest estimatesalso at different elevations bet¥veen geofoam block layers.The top three curves represent the loading history on thebasis of the t¥vo pressure cell readings and estimates fromthe record of surcharge placement over the geofoam fill.of tangent modulus from the field results are 11.6 andThe corresponding bottom two curves r'epresent settle-13.1 MPa compared to 4.1 MPa for the small sizedments of the geofoam fill at the respecti¥'e extensometerlaboratory test specimen. The dashed line in Fig. 8represents the average of the maximum secant modulusfor the t vo field curves of about 4 MPa. This secantpositions. The settlements are total deformations of 9and 9.5 Iayers of geofoam at the South and Nor'th arraylocations. The nominal thickness of each layer ¥vas 0.83m, so that the initial geofoam heights ¥vere about 7.5 mand 7.9 m at the South and North arrays, respectively.A Iarge part of the deformations re*'istered by themodulus value is closer to what normally is considered tobe the elastic modulus derived from corrected stressstrain data from laboratory tests on small size specimens.The trend of the field observations su*" est the tangentextensometers during construction ¥vere inferred to bemostly a result of **ap closure bet¥veen block layers(Negussey et al., ,_OO1; Stuedlein et al., 2004). Theinstalled geofoam blocks ¥vere not trimmed and tightdimensional tolerance criteria ¥vas not enforced. Postconstruction creep settlements, beyond approximatelymoduli, at stages beyond initial gap closure and for300 days, are minimal if not evident even thoughto transient loadings in post construction.assessin*･ incremental deformations and fati**ue life;should be at least twice the maximum modulus derivedfrom the laboratory testing of small specimens. Thehi*･her modulus values sug_ested by the field observationswould be more appropriate for evaiuating responses dueestimated and recorded stress levels exceeded 300/0 ofstrength at 50/0 str'ain for the nominal 20 kg/m3 densitygeof oam .SAMPLE SIZE F,FFF,CTSThe self ¥veight of the geofoam fill ¥vas negligible asPrevious studies of geofoam engineerin_g behavior bycompared to the surcharge pressure of the pavementDu kov (1997), Elra*'i et al. (2000), O'Brien (2001) alsosug_ :est a higher modulus and a linear range less thanthe normally assumed lo/o corrected strain limit. Furtherstructure. Estimates of applied pressures and pressure cellreadings at the base of the geofoam fill wer'e comparable.Figure 8 sho¥vs average stress strain relationships basedsmall strain modulus evaluation on the basis ofon the field observations presented in Fig. 7. Typicalresults from unconfined compression testin*" of a standard 50 mm cube sample of geofoam installed at 1-15 arecompression ¥vave velocities ¥vith bender element testsalso included in Fig. 8 for comparison. The curves for thefield results manifest an initial lag stage and stiffening¥vith further strain like the compression test behavior ofthe small siz,e test specimen. The base line readin*' for thethan the ¥videly accepted value of 5 MPa (as from resultsshown in Fig. 3) for 20 k**/m3 density geofoam. An alter-settlement monitorin_g: ¥vith extensometer arrays ¥vas(Sivathayalan et al., 2001) su_g:*"est upper bound estimatesof *･eofoam elastic moduli of 14 to 22 MPa and highernative approach for evaluating modulus from small beamdeflection testing also indicates higher modulus values(Anasthas, 2001). 165正）ESIGN PARAMETERSaDL弓aとnx糊戯n「冊 難冊鷲『㎜酬曽，r一雫 ▼ ▼■押酌窄r聖聖糊罵’『？【綴雫P概停… eo；灘＿一甲甲騰際篇爺…燕薫ト湾atnx Hεigh： 卜r、猟雛黛無澱淵＿．節＿＿陶一＿”曽 ”＿叩＿ 胃瓢算 甲”』諺篇”：爾 ＿“＿ΩolumR〉“曲隅綿；蹄拡器器襯闇”触‘甜甲甲，ぞ肺rr4 甲剛r障榊酌 F『お4D ＼ や、§3タ 一 2D 』 瀦繋』潔 一 loTab Row糊G 2 4 8 凌O 團 Coiロmn Sρ3qng Ve鵬aS児昌｛葵 一諏±眉㎜㎜Fl9。9．Uncon伽edcompresslo日of50a賎d600mmcubegeoεo甕m samplesFig，11． Det＆iis of謎tactile pressure sensor（謎dapted from Ieksc露r1， 2002）25一鉛現謂c睡狙s 血き ホあぬおる20一from Iaboratory tests on small size samples are too smaH篭15『and rather unrea正is宅ic to be used 圭n des量gn。 Beyondadjustnlents for seating error，the reason for the noted篇 10一sig且i負cant di仔erence玉n mo（玉ulus obta圭ned fronl sma王l ancl匿large sized samples was assumed to be due to end e錨ects． Conditions of uniformlty in both stress and（ieform＆一tlon cannot be imposed simukaneously at the interface ofo0 5 10 15 20 25 30 35 40 Densとylk9励Fl9．10．Geofoammoduluswi吐hde紅sit》一，sgmplessizeandest韮m郎e from6e鳳d observ鼠Iion（E塵r盆gi et訊L，2000）two materia圭s tぬat have cQntrasting sti登ness．In＆labora−tory test，the王oading Platens impose uniform deforma−tlon across the section area of test samples．Therefore，the s蓄ress non−uniforn1量ty at the relative星y rigid loadingplatell and Hexible but co勤esive geofoεしnl samPle was When compared to typical（iesign values associ飢edwith d醗ren嘘types ofsolls，5MP役is in a range normallyinferred topro（iuce h玉gherstressestoward theedgesi鍛themanner discussed by Taylor（1948）．This reasouing wasassumed for interpreting results of stacked samplesassoci＆tedwi由verysofttosof竜clays（Das，1998）．（Eh・＆gi et a1。，2000）where the average deformat玉on neαrWhereas the over10MP＆modulus implied by the且eldthe rigid Ioa（iing Platen was shown to be higher thandata indicates20kg／！n3density geofoaln compares betterdeformations across geofoam to geofoam interf＆ces．Aswith stifモer clays．Even when the｝1主gher unit cost can bea result of h圭gher edge stresses over tぬe top and bottonljusti且e（1，the apParent e（lulvalence of geofoam moduluseud faces of geofoam test samples，crushing and localto very soft to soft clay soまls cαn be ambiguous for prac−y量e1（i三ng were envisionedεしs like董y mechanisms for the lowtit1oners less familiar with prior geofo＆m applications．modulus an（1exaggerate（1creep deformatlon of small slzeFlgUre9preSentS reSUltS and COmpariSOn Of UnCOn且nedcompression tests on50aud600mm cube samples．Bothsαmples．With development of tactile pressure sensors，an altematlve means for sensing an（1investigation of亡he smα11an（i large size cube samplesαre of noml照1iuterf＆ce pressure distributions became poss量ble．15kg／m3density geofoam au（i were teste（1at10％perminute str＆in rate。However，｛he st正’ess strain curve for重he large sample is based on deformaξio茎1s measured over夏NTERfACE PRESSURE DISTRI8UT豆ON亡he midd圭e third of重he height and aw＆y from possible Tactile pressure sensors consist of tYvo Hexible sheetsedge e鉦ects at the lo＆ding Platen boundar圭es．The resultsshow the large sample based modulus can be double thateach containing thin conductlng strips over semi−con−ducting coated surface．Two sheets are mated to form＆for the slnall sa…11ple of the salne density．However，芝hevery thiu sandwich of semi−conductlng surf＆ce bet∼veenstrengths at either50r10％strain criteria are about thecon（iucting strips．In forlning the sandw重c｝1，the upPersame for both sample sizes．A slmllar di廷erence inInodu正us values over a range of densit量es was reported byand lower conducting strips are orien重ed orthogonally toform a grid pattem or ma芝rix of pressure sensing elemelltsElragi et＆L（2000）and ls shown in Fig．10．Also includedcalledsense歪s，Fig．n．Arowof44strlpsismatedwitむain Fig．10aτe the modulus estimates from負eld observa−tions and laboratory testing shown in Figs．3an（i8．τhecolumn of44strips to form a ma芝rix of1936sense至s．modulus of about10MPa for600mm cube sαmples ofand shapes c＆n be custom made．The spacing of theStandard sens量ng P段d sizes are avai正able aud specif崖c sizes20kg／m3density geofo＆m is in better agreement withconducting strips is varied to matc歴he deslre（i slze of themodu正us est呈mates from且eld observations，provicle（i gapsensing area．The semi−conductor Iayer be重ween theclosure e鉦ects are viewed separately．The星arger height ofcon（1ucting strips changes in resistance in response to600mm cube san1Ples is closer to the 重hickness ofcommon fu1正size EPS b三〇cks．八40（iulus values derivedapplied pressures．Reslstances measure（I at each gridpoint＆re highest when no external pressure exists．The NEGUSSEYl 66Table 1. Maximum, average and minimum pressuree O-70O -* festates at 1 ,locorrected strain in 25 clusters over the base platen and *eofoam'SliIIX:Itl!lllli;,;St :tiXlllAinterface: E,ach cltrster contains 64 senselsSQ - IllilllSl:lllltll8 sensels in each of columns A Io BSett30 - tt .'t .･'iO ' l:tle t.Itl'ilFa'$$2o*/er:$ = S:rBlr,)Fig. 12. Comparison of average pressures from a load celand tactilepressure seusors>oVconducting strips are protected by fiexible polyestersheets and connect to a handle. The handle connects to adata acquisition board in a computer via a cable. Theoverall sensor thickness can be less than a millimeter. Thethickness of the semi-conductin_g: Iayer controls the sensoroperating capacity, ¥vhich can vary from a lo v of O to 14kPa to a high of O to 175 MPa. Pressure sensor calibra-3e,ABC_153S61587)0829ll171617OOOOO23039O89248113237OMax 15557i 14177 432OOOAve 35Min O1 70,4vO1 2037O28O12034O6S20O23OD9821El 1433Ol 178172) )7 8OOO898920O77oe)19O20Otion studies indicate errors in accuracy to be less than 10to 200/0 depending on the pressure range. Sequentialscanning of the pressure field is displayed and stored inreal time. The average sensor output is calibrated againsta kno¥vn force or pressure to establish an adjustmentfactor. Force and pressure time histories of each sensingpoint can be further analyz,ed by exportin*' the data toother soft¥vare. The sensor manufacturer provides boththe hard¥vare and soft¥¥'are for the system. Tactile sensortechnolo*"y is about 25 years old and is now used in otherfields and industries (Paikowsky and Hajduk, 1997;Sodhi, 2001).re_g:ion follo¥ved by apparent yleld and plastic deforma-tion. The corrected modulus of about 2.5 MPa, strengthat 50/0 Strain of about 60 kPa indicated by results fromthe tactile sensors and also the load cell ar'e inood ag:ree-ment ¥vith corresponding values for' 15 k**/m3 nominaldensity geofoam, shown in Figs. '_ and 3. There is _ :oodcorrespondence and consistenc.y bet¥veen the stress straincurves and moduli derived from the record of tactilesensors and load cell obser¥'ations, as sho¥ 'n in Fig. 12.Individual sensel pressure states of the tactile sensorA 56 by 56 mm pressure sensing pad, Iike the onepads ¥vere captured and stored for further analyses andsho¥vn in Fi**. 1 1, ¥vas placed at the top and bottom of agraphic output. In play back mode, different stages of thetest ¥vere vie¥ved separately, frame by frame, to observe50 mm cube *'eofoam test specimen. There ¥vere 1936sensels over the full sensor pad. Pressure states at about1600 Iocations over each sample end surface contact areapressure distribution patterns over the geofoam testwere detected. Thus the area coverage per sensel wasapproximately 1.6 mnf. The tactile pressure pads had aseatmg error sta*'e, the applied load induced contactran'*._e of O to 250 kPa. Standard unconfined compressiontests at a strain rate of 100/0 Per minute ¥vere performedsample end areas. At the be*'inning of loading and in thepressure on only about half of the sample end areas. Withcontinued loading, the contact areas enlarged to the sizeof the sample end surface. A 3D representation ofon geofoam samples of 15k**/m3 nominal density.pressure patterns over the geofoam test specimen andPressure distributions bet¥veen g:eofoam to g:eofoam interfaces ¥vere also examined by testing t¥vo stacked 50 mmcube samples ¥vith tactile sensors placed in bet¥veen thesamples and also at the interface of the lo¥ver block andbase pedestal. A Ioad cell and a displacement transducerrecorded the applied vertical force and resulting deforma-base platen interface sho¥ved scattered spikes and loadfree sensels. A summary of pressure states for all senseltion synchronously.Figure 12 shows a plot of vertical stress against strainfor a geofoam sample based on data from the tactilesensors and the load cell output. The lo¥ver curvepositions, as in Fig. 1 1, at a corrected strain of lo/o anda¥'erage adjusted pressure of 25 kPa (at approximately20/0 Vertical strain in Fig. 12) is presented in Table I . Eachof columns A to E contains 8 sensel columns and each ofro¥vs I to 5 contains 8 sensel rows. Thus clusters IAthrough 5E each represent 64 sensels for a total of 1600potential load bearing sensels at the base platen andgeofoam mterface. Maximum, a¥'erage and minimum ofrepr'esents the unad.justed average output from the top64 sensel pressure states within each of the 25 clusters areand base tactile sensor pads. With ad.justment or calibration, the average stress strain curve for the tactile sensorspresented in Table I . Maximum pressures vary from '_30matched ¥vith the load cell based stress strain resultsreasonably ¥vell. All three curves sho¥v the characteristicsure states in all clusters, except 3B, exceed 60 kPa or thestren*'th of the geofoam at 50/0 strain. In several clusters,bedding error stage at initial loading, presumed elasticmaximum pressure states exceed twice the 60 kPa refer-to 57 kPa ¥vith an average of 110 kPa. Maximum pres- DESIGN PARAMETERS167'T'able 2. Contact pressure statcs at 1?/o corrected strain for 64 sensels2 e s: *of cluster 3C, the middle clustcr in Table lRo¥vHh ssColumn3 . 1 29 24 1 2 27 99O1736o98oo45oooi5oooo50:363 6 O 29 101 50 56 O3.7 21 32 3- O O38 O 80 363341O15e*; J'J3sQ3.3o 33o 60 29 o o41ili+f fC I C ' C 3 C.4 C.5 C.6 C 7 C 8O,!_ 2ee +o1 O 20OSO eso3070QiS 1'**iPereerit e cf Cen s: J feFig, 13. Sensei pressure states at I and 5,,corrected vertical strain fortactile sensors at top and bottom geofoam and loading piateuinterfaces89250 -33x,*!s, s:S e es:n! 3 s :sF:slFISs;feesl ISsse :} rn ,ee* at3ee･SlTeC$]5BitTxxx)ecXxxefTe s ) (xx20 )JL=iS,f ses,･!e xxxxxxXX'(e LeSti e : ce e(XXxx:･.e(xxXxxxence strength for setting an allo vable ¥vorking stress.Average pressure states in the same 25 clusters range fromiSO xXXxxXxXxx xx39 to 11 kPa ¥vith a mean of 25 kPa. The mean of thelee *.faverage pressures is the global average of all 1600 senselsand is equal to the a¥'erage pressure deri¥'ed from the loadcell record at lo/o corrected strain. The 25 kPa giobalaverage pressure at 10/0 corrected strain constitutes theallolvable ¥vorking stress for the test sample geofoamdensity. Ho¥vever, maximum pressures of up to one orderof magnitude higher than the allowable ¥vorking stressx ia,"Y･･F･ .. .IU,ll･1'1･I ll !uf･･8.81 9'ell'>SOx e..*e""""""'･f･･･"IF････'･"""'e$ee,Fee#$$x ...O tSt AdL*t4 G #A.-2VertiGa' SL 2 n (Fig. 14. Contact pressutes betwee 1 geofoamlgeofoam and geofoam/end platcn surfacesdeveloped at discrete positions over the end contact area.Initial contact and loadin*' started along the left edge ofdecreased in the manner evident in the long durationthe sample. The highest contact pressures continued todevelop on the left side as loading progressed but zeroconstant loading r'esults sho¥vn in Fig. 5. As local stressstates greater than yield began to develop at the earliestpressure states existed in all 25 clusters and at all stages ofstages of loading and co-existed ¥vith states of zeroloading and strain le¥'els. Pressure states for all 64 senselspressure throughout the test period, elastic and plasticconditions remained current at a loading interface at allof the center cluster 3C at lo/o corrected strain are shownin Table 2. Maximum, average and minimum pressuresfor' cluster 3C hvere 101 , '_1 and O kPa, respectively. Bothtimes.Figur'e 14 sho¥vs comparisons of pressure distributionsthe rnaximum and a¥'erage pressures of 101 and 21 kPawere below the mean of maximum and avera*'e pressuresof llO and ,_5 kPa for the 25 clusters. Over l/3 of thebet¥veen a geofoam/sensorlgeofoam interface and at ageofoam/sensor/base loading platen for a test on twostacked ,50 mm cube geofoam samples. The interface atsensels in cluster 3C vere under zero pressure ¥vhile about420/0 of the sensels ¥¥'ere at pressure states greater than thethe bottom tactile sensor pad was between the metal baseallo¥vable ¥vorking stress of 25 kPa. Approximately 6010tactile sensor pad lvas located at the geofoam to geofoamof the sensels in cluster 3C ¥vere at pressure states equal orinterface between the two samples. While the trend ofcontact pressures for the upper and lower sensor padsgreater than the *"eofoam stren*'th of 60 kPa at 5010corrected strain.plate and the lo¥ver geofoam block end area. The top¥'as sirnilar, t.he upper geof'oam to geofoam interface ex-Frames containing pressure states for all sensels atcorrected strain levels of I and 50/0 were extracted toperienced a lower maximum pressure profile. Maximumfurther review the pattern of stress distributions. Figurebe lo¥ver, if detected ¥vith a more flexible tactile sensor13 shows the percentile of the contact areas that weresubjected to differ'ent tactile pressures at the top andbottom of geofoam to rigid plate interfaces. At the lolopad to closely approximate a geofoam to geofoam interface. This is because the sensor acts to bridge voids toinhibit cushioning of small area stress concentrations.strain le¥'el, about 100/0 of the end areas ¥vere subjected toThe interlocking of intact cells and void spaces is a likelypressures at or above the average pressure associated with50/0 global strain. On the lo¥v side, up to 300/0 of the endareas were under zero pressure at lo/o strain. About 100/0cause for observed good interface strengths at geofoamto geofoam interfaces. Figure 14 also shows that peakpressure states exceeding levels correspondin_ : to thestrength at 50/0 corrected strain began to develop nearzero corrected strain and at initiation of loading. Suchof the end areas were at contact pressur'e states belo vyield when the global st.rain reached 50/0 . With yieldingcontact pressures between geofoam surfaces should evenand pressure redistribution in the vicinity of localhigh stresses tend to infiuence laboratory test results butmaximum pressure areas, creep rates would ha¥'ewould not develop to the same extent to significantly NEGUSSEY168* ' "" ;.' **.*SS*' ",'!,!' ."Fig. 15, Resin beads, pre-puffs and a cut surface ex'posure of ageofoam blockFig. 17. Magnified (X30) image of fused pre-puffs and void labyrinthsat a geofoam surfacepufi) void spaces are visible. For' the sensel dimensions ofthe tactile sensors that were used, about 8 sensels coverthe field of view (about X30ma*"nification) in Flg. 17.Some sensels ¥vould therefore cover fully or partially voidspace ¥vhile others would come in contact ¥vith pre-puffelements. Ho¥vever, at a cut surface, as in the backgroundof Fig. 15, most pre-puff units become cut. The voidspaces become exposed to atmospheric pressure and onoccasion intact pre-puffs remain undama*'ed at or verynear to the cut surface. The fe¥v sensels that came in fullcontact with undamaged pre-puffs ¥vere likely positions atFig. 16. Magnified (X600) image of pre-stFessed ce!Is in a pre-puffaffect field performance.CONTACT SURFACE DETAILSA photograph of resin beads (the feed stock for¥vhich maximum pressures developed. Ho¥vever, even at acut pre-puff, some gas cells ¥vere open ¥vhile othersremained intact. The image in Fig. 16 covers a portion ofa cut pre-puff from a sample that ¥vas previously loadedto 100/0 strain. Most of the cells ¥vere open and thecollapsed ¥¥'alls formed hexagonal configurations. Closedcells are evident at the south east corner of Fig. 16. Inmating cut geofoam to geofoam as opposed to _"_.eofoam*'eofoam production), pre-expanded beads or pre-puffto metal surfaces, the maximum tactile pressures attogether vith a small cut sample from a *'eofoam block issho¥vn in Fig. 15. The spherical resin beads, on the lowergeofoam interfaces ¥vould be lo¥ver and less susceptible tocreep. Within the interior of the geofoam mass, pressur'eleft, are generally 0.5 to I mm in diameter and containtiny impregnated **as bubbles, pentane, as a blo¥vin-'in the discontinuous voids can increase in response toloading and deformation of the fused pre-puff particles.a*･ent. The gas bubbies are contained in a polystyrenematrix. In the pre-expansion stage, the resin beads aresubjected to steam and pressure. The polystyrene matrixThe initially spherical pre-puff particles tend to acquir'esoftens to allo¥v the gas bubbles to expand in forming thepr'e-expanded beads or pre-puffs, on lo¥ver right, thatacquire diameters of 3 to 5 mm. The resin type and extentof pre-expansion *'enerally determine the density gradeof the geofoam block. As nei_g:hboring gas cells act tocontain the expansion of adjacent cells, the sphericalbubbles ¥vithin a resin bead acquire polyhedral shapes¥vithin the pre-puff, Fig. 16. The field of vie¥v in thisscanning electron microscope image (about X600magnification) covers an area of about O 05 mm2. Theindividual cell units ¥vithin a pre-puff are too small to bedetected in isolation by a sensel of about 1.6 mm2 ar'ea.The pre-expanded beads are poured in a mold and aresubjected to steam and pressure under all around confine-polyhedrai shapes ¥vith loading and deformation. As thenetwork of fused pre-puffs contains the trapped air in thelabyrinths, pressure increases ¥vithin the voids contributeto stiffening and more uniform internal pressure distribu-tion. Along the outer perimeter surface, voids betweenpre-puffs remain exposed to atmospheric pressure. As aresult, the portions of geofoam in the proximity of theouter boundary surface ¥vould tend to manifest morecompressible behavior. When spherical pre-puffs anddiscontinuous void spaces come in contact ¥vith loadin_-'platen, higher pressures begin to develop at the spher'econtacts like for individual grains in a granular matrix.Ho¥vever, vhereas granular particles can rearrange, thefused pre-puffs remain relatively immobile. L,oad shedding ¥vould tend to be restricted and the intact pre-puffsand cells ¥vithin sustain pressure. The maximum stressesment to form a geofoam block. On further expansion andregistered by the sensels refiect the combinations offusion ¥vhile in the mold, the pre-expanded beads or pre-relaxation, as the ¥vall of closed cells expand, changes inpuffs become immobilized in a matrix of discontinuousgas volume occur and interaction ¥vith adjoining cellscontinue. Void spaces and open cells occur across a cutair ¥'oids. This is sho¥vn in Flg. 17 where individual preexpanded beads have fused and inter-particle (inter pr'e-face and their influences on creep defor'mation beha¥'ior DESIGN PARA *IETFRS 169become exaggerated ¥vith decreasing sample height,paper. Chuck McWilliams of Tekscan, Inc. assistedlvlodulus ¥'alues determined by testing small samplestactile pressure sensor tests. Huntsman Chemicalrepresent significant underestimates of the beha¥'ior ofCorporation, the Federal High¥vay Administration-NYfull sized blocks.Di¥'ision, NY State Department of Transportation, UtahDepartment of Transportation and the Foam PolystyreneAlliance of the American Plastics Institute pr'o¥'idedCONCLUDING REMARKSWith 30 years of field experience and resear'ch, somevithresearch support. The author is indebted to all mentionedand others ¥vho helped.changes in determination and application of geofoamdesign parameters appear to be in or'der. Density is a_ ood index property for design parameters and classifica-tion of geofoam. Both strength and modulus of geofoamincrease ¥vith density. Field and laboratory results indi-cate modulus values determined by testing small sizelaborator'y samples can be increased. Thus for thecommon 20 kg/m3 density geofoarn and the generic design value most often used, a modulus of up to 10 rather 5MPa is more consistent with actual behavior of larg:eblocks. The mix of closed cells and ¥'oids over a geofoamsurface and associated variability of contact pressureintensities evident from tactile sensor observations alsopr'o¥'ide insight into friction coefficients for geofoam togeofoam sliding. The interface friction bet¥veen geofoamsurf'aces is higher than values for geomembr'anes becauseof the surface conditions. Creep concerns pr'e¥'iouslyidentified on the basis of laboratory tests on small samples ha¥'e not been evident to the same extent in fieldobservations. Even ¥vhere excessi¥'e deformations undersustained pressures occurred in laboratory tests, the creepstates remained in primary stage and dld not lead tor'upture or failure. Field obser'vations indicate seating andgap closure mo¥'ements mostly occur' during construction. Post construction total and differential settlementsof geofoarn fills ha¥'e gener'ally remained tolerable. Byincreasing the design modulus and with better understanding of creep behavior in geofoams, Io¥ver densityand less expensive grades of geofoam can be jusrified forsome applications. Alternatively, more intense static andtransient design loads can be supported ¥vith higher'density geofoams. The increase in modulus improves thecorrespondence of design estirnates and performanceobser'vations for dead load or sur'char'ge loading. Fortransient r'esponse, such as from tr'affic loading on rigidor' flexible pavement structures, the combined action ofthe load distr'ibution slab and the geofoam fill should beconsidered. Additional effort has been directed to examine alternative approaches of representing concreteslab and geofoam composite subgrades for pavementdesign.ACKNOWLEDGEMENTSThe author ackno vledges the contributions of formerand current gr'aduate students A. Elragi, N. Anasthas, X.Huang, M. Sheeley, S. Srirajan, A. Stuedlein and M. Sunvhose individual and collective work has been the basisfor this paper. R. Chave, G. Gresovic and J. Banasassisted ¥vith setting up test equipment and data acquisi-tion systerns. P. Ford helped vith preparation of theREFERENCESi) Anasthas. N (2001): Young's nloduius by bending lest and otherproperlies of EPS geofoam relaled to geotechnical applicarions,iV[asrer's Thesis, Syracuse Universi ¥'. Syracuse, NY,2) Bartlett, S , Farnswor h, C., Negussey, D. and Stuedlein, A(2001): Instrumentatlon and long-term monitoring of geofoamembankmems, -15 reconstruction project, Sait Lake C*ity. Utah,EPS Geofoam 2001 , 3rd Int. Coirf EPS Geofoafn, Sah Lake City,UT3) BASF Plastics (1998): S!.vropor Techilica! Information, Ludlvigshafen, (i ermany.4) Das, 'l. D. (1998): Principles o_f Fozmc!ation Engineering, 4thEdirion, P ¥;S Publishir.5) Du kov. N'I_ (1997): EPS as a llght-¥veigh sub-base material inpavement s ructures, P/i.D Tliesis, Delft Universily of Technology. Delft, the Netherlands6) Elragi. A F (2000): Selected engineering properties and applica-tions of EPS geofoam, Ph.D. Thesis, State University of Ne¥vYork, Syracuse. NY_7) Elragi, A. F., Negussey, N. and Kyanka, G. (2000): Sample sizeeffec s on the behavior of EPS geofoam. Proc. Sof! Ground T cllno!o*"_v Conf , ASCE Geotechnical Special Publication I 12, IheNetherlands8) Eriksson, L. and Trank, R. (199 ): Propenies ofE.xpanc!ec! Pol_vstyrene. Laborato,y E"¥periments, Swedish (3 eotechnical Institu e,Link6ping. S¥veden,9) Esch, D. C. (1995): Long-term evaluations of insulated roads andairfields in Alaska. T,'ansportation Research Recorcl ! ' o_ 1481,Transpor ation Research Board, 1¥;ashingtorl. D.C.lO) Frydenlund, T_ E (1987): Soft ground problems, outline of alternative solutions arrd the various applications of ex.'panded polystyreneas a light fill material in Nor¥vay, Vegc!irektoratet, Norwegian RoadResearch Laboratory, lvleddelelse 61 .11) Frydenlund, T. E. and Aabce, R(1996): Expanded poly-styrene-the light solution. Proc Inf. S_vmp- EPS CollstructionIVlethoc!, 'Tokyo, Japan12) Frydenlund. T. E. and Aaboe. R (2001): Long term performanceand durability of EPS as a light¥veight fil ing material, EPSGeofoain 2001, 3rd International Conference on EPS G eofoam,Salt Lake C ity. UT13) Ho ta, H (2001): Aseismic design of expanded poly-styrol fil inJapan. E'PS Geofoam 2001, 3rd Internationai C onference on FPSGeofoam. Sali Lake City. UT,14) i¥,Iiki, O . (1996): EPS construction method in Japan, Proc. Int.S_vinp. JEPS C*onstruction !V[etllod, 'Tokyo, Japan.15) Negussey, D. (1997): Proper!ies anc! App!ic'a!ioiis of Geofoain,Society of the Plastics industry, Inc., ¥Vashington, D_C.16) Negussey, D. and Jahanandish, "I. (1993): A comparison of someengineering properties of EPS to soils. Transporta!ion Researc'/1Recorc! No. 14J8. Transporta ion Research Board, ¥¥rashing on,D.C17) Negussey. D. and Stuedlein. A. (2003): G eofoam fill performancemonitoring, Report No. UT-03.17, Ulah Departmem of Transporation Research Division, Salt Lake Citv. UT.18) Negussey, D. and Sun, .¥,1. (i996): Reducing lateral pressure b)geofoam (EPS) substitution. Proc. In[ S_ 'inp EPS Construc!ion_, ifethoc!. Tokyo, Japan19) Negussey. D . Stuedlein, A , Barrletl. S. and Farns vorth. C , 170NEGUSSEY （2001）：Performance of a geofoam embankmem at王00south，董一1524）Siva由ayala鷺，S．，Negussey，D．and Vald，Y．P、（2001）l Simple reconstruclion projec【，Salt Lake C紅y，U置a無，だP3Gθoゾ10σ1η2001， shearandbenderelementtestlngofgeofoa磁，EPSGθoゾoαη12001， 3rd I臓ematlonal Conference on EPS Geofoam，Salt Lake C琵y， 3rd王瓢ematlonal Conference on EPS Geofoam，Sah Lake Clty， uT． uτ、20）0，Brien，A．S．（2001）＝葺PS be員avior dur玉ng static and cyc巨c25） Sodhi，D、S、（2001）：Crush圭ng faHure during玉ce−structure interac− Ioad1ngfromO、 05％stra圭ntofallure，EPSGθoゾoσ1π2001，3rd tlon，動gi17θε’甲’ngF1’αc’三〃ぞル伽17傭c5，68， Intemationa亙Conference o貴EPS Geofoam，Sak Lake Clty，U■．2玉）Palkowsky，S。G、andHajduk，E．L．（1997）：Calibraほonan（玉useof h玉story ofεhe use of geofoam for bridge apProac｝1負裏玉s，Proc，5’h gri曲asedtactilepressuresensorsingra凹iarma面al，Gθo鷹1∼、 加．Co11∫Cα5θ甜5’01ブθ5’11Gθo’θchη’cθ’E119’ノ1θθ吻9，NewYork， ル5r．／．，GT．∫ODJ，20（2）、 NY．22） Sheeley，費1、（2000）：Slope stab簸呈zation u樋1iz玉葺99eofoam，A∫o∬θ∼門y Thθ5Z∫，Syracuse Universlty，Syracuse，NY．26）S葛uedlein，A，，Negussey，D．andMathloudakis，M．（2004）IAcase27）Taylor，D。W．（1948）：F∼〃ゆ’ηθηfθ150∫So〃Mθごhαn’c5，Jo盤nWiley an（玉Sons，Inc、，New York，NY。23）Sheeley，M， andNegussey，N。（2000）＝A鳶inves葛igationofgeofoam28） Tekscan， Inc． （2002）：11πノ々5’がα1Sθη501’Cα’α109，Sou【益 Bosto鷺， 玉Pterface stre澱gth behavior，P1”o（：．50ゾγG1’oμπゴ7セch’70109y Coπノ〔， MA、 ASCE Geotecねn玉cal Spec1al Publication ll2，こhe Net簸erlands。
- ログイン
- タイトル
- Initiation and Traveling Mechanisms of the May 2004 Landslide-Debris Flow at Bettou-dani of the Jinnosuke-Dani Landslide Haku-san Mountain, Japan
- 著者
- F. Wang・Kyoji Sassa
- 出版
- soils and Foundations
- ページ
- 141〜152
- 発行
- 2007/02/15
- 文書ID
- 20989
- 内容
- YSOILS AND FOUNDATIONS¥f ol47, Nol.141l52,F eb .2007Japanese Geotechnical Socie vINITIATION AND TRAVELING MECHANISMS OF THE MAY 2004LANDSLIDE-DEBRIS FLOW AT BETTOUDANI OF THEJINNOSUKE-DANI LANDSLIDE, HAKU-SANMOUNTAIN, JAPANFA ¥*U WANGi) and KYOJI SASSAi)ABSTRACTIn May 2004, a landslide occurred at the right flank of the Jinnosuke-dani landslide, and transfor'med into a debrisflow after fluidization. By analysis of the monitored video images of the debris flo¥v, field investigation on the sourcear'ea of the landslide, and a series of simulation tests ¥vith a rin_ :-shear apparatus on the initiation of the rainfallinduced landslide and its tra¥'eling process, the initiation and traveling mechanisms of the debris fio¥v traveling in thevalley were investigated. It is sho vn that concentrated ground¥vater flo¥v ¥vas the main reason for the landslideinitiation, and a rapid decrease of the mobilized shear resistance even under naturally drained condition caused therapid landslide motion. Durin*" the debris motion in the valley, high potential for grain-crushin*" of deposits inupstream and lo¥ver potential for the do¥vnstream deposits controlled the traveling and depositin*' processes of thedebris fiow. Different grain-crushing potential of the ¥'alley deposits played an important role in the debris flo¥vtra¥'eling and depositing processes.Key lvords: case study, fluidization, grain-crushing, ,: Oround¥vater, landslide, ring-shear test (IGC: D6)fINTRODUCTIONHaku-san Mountain is located at the boundary between Ishikawa Pr'efecture and Gifu Prefecture inHokuriku district, Japan (Fi**. 1). It is an active volcanoJapan Seawith a summit elevation of 2,703 m, and the ¥vholernountain is a national park. This park is famous for itsbeautiful scenery. About 50,000 mountain climbers visit*N 'r'¥¥"'_=' r¥^*this mountain in the period from 15 May to 15 OctoberTedori RiVer fr¥ Ka na wa!lrevery year'. Tedori River, the largest river in IshikawaPrefecture, originates in this area. The Jinnosuke-danilandslide (Fig. 2) is a giant landslide located on the'¥ I .,r. *Tedor idam(r_'r_ ?' ' _'"'vsouth vestern slope of Haku-san Mountain ("dani"Gifu"landslide designated as a "Landslide prevention area" byFig. 1.the "Japanese Landslide Prevention La¥v" in 1958.Meunta i nfi nnosuke lan i, 50 l 1 Iandslidec*!means valley or torrent in Japanese). It lvas also the first--;; :::.HakutsanFUku i ' * * - * -'/_"' !?vToyamaLocationmapof the Jinnosuke*dani landslideLandslides fr'equently occur in this area, and cornmonlytrigger debris fiows that tra¥'el long distances and damageproperties in the downstream valley of the Tedori River.right side is an active landslide, according to data obtained by rnonitoring, and is called the "Central RidgeIn the photograph of Fig. 2, t.he areas not covered byvegetation are local slope failures. For example, at theleft side of' the photograph, the main scarp and slidingBlock" of the Jmnosuke dam landslide (Frg. 3). The¥vidth and length of' this block are 500 rn and 2,000 mrespectively. Besides the "Central Ridge Block", thereare many other active landslide blocks in this area (Wangsurface of the Bettou-dani failure, which occurred in1934, is visible. In that event, a debris flow initiated by alandslide reached the Japan Sea after traveling for 7,_ km.et al., 2007). In Fig. 3, the blocks with arro¥v inside areThe upper part of the central ridge sand¥viched by thethe deformation of the Central Ridge Block, IocalBettou-dani at the left side and the Jinnosuke-dani at thelandslidesactive landslide blocks. In recent decades, accompanying'ith different volumes occurred at both bound-_ , Japan ( vangf¥v@landslide.dprl k}'oto-u,ac,jp).Research Centre on Landslides, Disaster Prevention Research Institute, Kyolo Universit}'The manuscript for this paper ¥vas received for revie v on lvlay 12, 2006; appro¥'ed on Nobember 17, ,-006.¥Vritten discussiorls on this paper should be submitted before September 1, 2007 to the Japanese Geotechnicai Sodet.v, 4-38-2, SengokuBunkyo-ku, Tokyo I l_7-001 1, Japan. Upon request the closing date rnay be extended one month.14i 142WANG AND SASS．A翁Fiα4． PhoIo o郵deb罫is rete凱io臓dams cons汀ucled ln the Jin鳳osuke・ danl、’＆lleydestroye（墨，and a loca玉road with a s量mple bridge utilizedfor debris−retention dam construction at the m量d（1至e ofBettou−dani was heavily（iamaged．Fortunate正y，nobodywas injured because there were not many mountainFig，2， Aeriai phoIog獄ph of the‘‘L聞薩s髄de Preven1董on Area”onlleclimbeτs passing through the vα11ey when the lan（i− Jin鶏os聴ke・｛韮ani Iandsl量de（Photo Cour吐esy of K謎癩段zawa Of罰ce ofslide一（iebris Row Qccurre（i．However，becαuse l＆n（1s正ides R韮vers段ndN飢io罰翫1｝｛ighways，MUT）with sim録ar behavior fre（1ue難t至y occur in this area，therisk for further 星an（islide and debris How activity still鰯．』蜜蓄歪㌻霧諺藁纂叢exists。As a national park，it should be absolutely safe forthe tourists．Even if some large Iandslides cannot becompletely stabi歪ized，understanding their potential risk，espec玉ally their motion behavior is a玉so very impoτtantfor disaster mitigation．Looking at the large parks ia themOUatainOUSareaSintぬewOrld，itlSeaSytO負ndaCOm−mon feature，th飢ls，steep topography with nice viewsoften has highτisk for landslide．This paper attempts toc1αrify the inltiation and trave1量ng mechanisms of theIandslide−debris flovv， aiming to supPly ins量ght for馨難難響難、察響 彦i馨馨藤麟 馨饗斐嚢∼ 際だ外♪、 ．驚』一至uturelandslidedisasterpreventioninsimilararea．GENEKAL CONDITIONS OF THE JINNOSUKE−DAM LANDSHDE ON｝｛AKU−SAN MOUNTAIN 丁紅e Haku−san Mountain area is characteτized by heavyprecipitation and由e Tedori River is characterized by itssteep gradient（Wang et aL，200410kuno et al．，2004）．InFig。3． Ac額ve kmds韮ide b置ocks in Ihe】遷謎ku冒s段睡mounI田臓area aroundIhe“Ce瞭alR韮dgeB皿ock”oヂ 1e Jinnosuke鼎da鳳i皿露ndslide（B段sedwinter，due to the s毛rong inHuence of monsoons fromSlberia，the accumulative snowfall may exceed12m ino臓 Kan段za、va O盤ce Qε Ri、rer and Natlon登1｝翌i毬h、、’段ys，MLIτ，the Haku−san Mountain area．In other seαsons，half of2004a）the days are rainy．For this reason，local annual averageprecipitatio鷺is3，295mm，about two times the nationaIaverage of1，700mm for Japan、In this area，snowmeltary valleys of the Central R．idge Block an（i causedgenerally begins in the middle of Maτc勤aad Bnisbes by〔iamage，althoug熱many countermeasure works熱avetむe end of May．互勲May2004when the landslidebeen imple搬ented in出is area for more than50ye＆rs．Figure4shows the debris retention dams constructed intive rainf段ll for three days be｛ore the歪an（isl量de occurredthe，linnosuke−dani valle》・．h May2004，a landslideoccurred at the upper part of the Bettou−danl from theOCCUrYed，SnOW melting WaS On−gOing，and the aCCllmUla−was216mm（F呈9．5）．It is also reasonable to consider thatt薮e effective water that infiltrated into the slope s封ould beCentral Ridge Block．This landslide was transfoτmed intomore than this value．Because the movement wasa debris How t勤at tra、7eled more嵐an2km after it slidrecoτded by a video camera of the Kanazawa O伍ce ofinto theBetto11−dani，A suspensionbridge was completelyRivers a熟d Natlonal Hlghways，Ministry of Land 2004 BETTOU-DANl LANDSLIDES-DEBRIS FLO Veo300:: 50250o: 40E:IlI 150! 30c:_(Q100>' 20:)Io Io50O o:1 ,900 m, and the elevation of the toe part of the depositof the debris flow caused by the landslide was about I ,2007sm. Figure 7 sho¥vs t¥vo aerial photographs taken beforec:cQthe event ((a): in the fall of 2003), and after the event ((b):e)on 24 May 2004, 7 days after the landslide-debris fiow),and the trace of the debris flo¥v with ele¥'ations at some)ce:!V<Voee ,e eo to ,O h hh143h hDateFig. 5. Hourl, rainfall before the landslide-debris flolv occurred(The rainfaH gnuge vas tocated at the ceutral ridge block ofJinnosuke-dani lantlslide, antl ,1'as measured b .' Kanaza va Officeof Rivers and National Highways, MLIT)key points (c). As shown in Fi**. 7(a), the source area is asteep cliff and there ¥vas no vegetation on the lo¥¥'ersegment of the landslide; ho¥vever, at the upper part, theslope is relatively gentle and is covered by vegetation. Formountain climber's, after leaving Bettou Deai, vhich hasfacilities such as parking areas, rest rooms, simplerestaurants, and a bus stop, most of the climbers have tocross the suspension bridge and access the Central RidgeBlock of the Jinnosuke-dani landslide to get to thesummit of Haku-san Mountain. At the middle of theBettou-dani, an access road for construction of debrisretention dams crosses the valley and enters the CentralRidge Block. As sho¥vn in Fi**. 7(b), both the roads andthe bridge ¥vere badly dama*'ed ¥vhen the debris fiow hitthem. The entire flowing process of the debris fiow lvasrecorded by a video camera (see Fig. 7(c) for the photo ofthe video camera set at the site), ¥vhich was set at anelevation of about I ,860 m for the purpose to monitor theFig. 6. Geologicai map of the area adjacent to the Jiunosuke-danilandslide (modified from Kaseno, 2003)important rivers, especially at the sites ¥vhich ha¥'e highInfrastructure and T'ransport, Japan (KORNH-MLIT)risk for landslide and debris flo¥v. The video cameramonitorin*" was conducted with a remote control system,and the ¥'ideo image can be r'evie¥ved in real time on the(2004b), the actual failure time ¥vas also exactly recorded,and the video image is very important for the study on theinternet. Because Bettou-dani is a valley ¥vith high potential for landslide and debris flow, it has been under con-motion mechanism of the landslide and debris flow.trol and rnonitored for 24 hours a day. Through analyz-As a part of the 1:50,000 geological map of theHaku-san mountainous area, a geological map of theJinnosuke-dani landslide and the nearby area wasing the recorded video images of this event, it is estirnatedHaku-san mountainous area is Lower Paleozoic Hidagnerss Overlymg this gnelss are Jurassic to Ear'lythat the velocity of the debris flo¥v may have reached amaximum of 20 m/s. As shown in Fig. 7(c), the relativeheight difference between the source area and the toe ofthe deposits of the debris flow (near No. 10 debris retention dam) ¥vas 700 m, and the horizontal travelin*" dis-Cretaceous sediments consisting of shaie, sandstone andtance was about 2,000 m. Based on these data, thecompleted by Kaseno (2001). The basal bedrock in theconglomerate, and lacustrine sediments kno¥vn as theTedori Forrnation. General descriptions of the geologycan be found in Kaseno (1993). Figure 6 sho vs thedistribution of strata in this area. Alter'nating layers ofapparent friction angle c. (defined as tan c. = H/L, IvhereH is the difference of elevation between head and toe of alandslide, and L is the horizontal distance from head totoe) of t.he debris flow is estimated to be 19.3 de*'rees.sandstone and shale of the Tedori Formation areFigure 8 shows the situation when the suspensiondistributed at the left side of the figure, and thebridge was completely destroyed. Large boulders 3-4 min diameter were transported and deposited near theCretaceous Nohi Rhyolites are distributed at the rightside. Both form the bedrock of this area. Volcanicdeposits, which erupted 100,000 years ago and 10,000years ago, overlie the strata of' the Tedori Formation andthe Nohi Rhyolites.THE MAY 2004 LANDSLIDE-DEBRIS FLOWAs mentioned earlier, the landslide occurred on 17 May2004 after conrinuous intense 'ainfall for two days. Theelevation of the source area of the landslide was abouts;debris fio v in the Bett.ou-dani valley by the KORNHMLIT (2004c). In Japan, under the leadership of theMinistry of Landslide, Infrastructure and Transport,monitorin*" video cameras are set at different parts ofbridge site. Some small debris vas deposited on the top ofthe left pillar' of the bridge, about 10 meters above thevalley bottom. This sho vs that even near the terminus ofthe debris flolv, the sliding potential ¥vas high andpowerful.Figure 9 sho¥vs a series of' continuous images takenfrorn the monitorin*' video of KORNH-MLIT. Thelocation of the video carnera was about 250 m downstream from the source area of the landslide. The time inseconds is shown at the top of each image. Fi**ure 9(a) ¥ rANG AND SASSA144s. ' Source j reiay. 2 004'i n' t"eTd- j!iide'lE]evation1 ,900 m*Beto" 1iIBet0-2_..,l,*{ S**"'*MonitoringVideo j* Si ;.:..-..,camera i;.i=',*; ;;;:{; Z{ Z,{'-Tota I iBeto-horizontal ;distance: i2,000 m iEleVation1 ,25,0 m-(-uspensi,onbridgBet1 O Deb isntion d mElevation1 ,200 m(a)(b)(c)Fi**. ?. The Mal ' 2004landslide-debns flo l 1 hrch occurred m theBettou dam from the Central RltigeBloek of theJlnnosuke dam landsllde (a)aerial photograph taken before the slope failure (in the falof 2003), (b) aerial photograph after the landslide (taken on 24 Ma)' 2004) and (c)trace of the debris fiow (Photos courtesy of th8 Kanazalva Office of Rivers and National Highlva .'s, MI.IT)there was fog goin*" alon*' ¥vith the sliding mass, indicating a hi**h traveling speed of the slidin*' mass. The secondwa¥'e ¥vas from (g) to (i), ¥vhich continued for 3 seconds.In this short period, a relatively. small sliding mass passedthe video very quickly. The third wave ¥vas from (i) to (s),which continued for 1 1 seconds. During this lon*' period,the slidin*' mass passing before the video ¥vas ver'y highand wide, indicating a large ¥'olume. As sho¥vn inFig. 9(s), an interrupt can be seen in the middle of theslidin*' mass. Actually, the flow of the slidin_ : mass shouldFia. 8. The suspension bridge that was completeh_' destro .'ed by thekeep continuous at the lo¥ver position of the valley (FromMa .' 2004 debris flow in the Bettou-dani (Plroto courtes .' of tl]ethe camera location, the bottom of the valley cannot beobserved). From 16:32:58 hrs, the dimension of the fio¥vbecame smaller, but sho¥ving a continuous flo¥v. For thisKanazawa Office of Rivers and ¥. *ationai Highways, Ml,IT)shows the situation just before the debris flow ar'rived.The vhite dotted lines in these ima'-es are the boundariesof the sliding mass in the Bettou-dani valley. The whitecolor in the images is snolv. The debris fiow passedthrou*'h the video from 16:32:37 hrs to 16:33:16hrs;reason, the fourth wave ¥vas defined from (/') to the end ofthe motion (at 16:33:16hrs), ¥vhich continued for 18seconds. The ima*"es after (x) ¥vere not presented herebecause the direction of the video camera ¥vas changed toobserve the situation of the upstream part. For all of thethus, the entire process continued for only 40 seconds infront of the video camera. By analysis of the video ima*'esima*'es includin*' the sliding mass, it is obvious that all ofsho¥vn in Fig. 9, the debris flo¥v can be di¥'ided into fourseparate ¥vaves. The first ¥vave vas from (b) to (g), ¥vhichcontinued for 7 seconds. As a frontier of the slidin_"_, mass,recognized in Figs. 9(d), 9(e), 9(r), 9(s) and 9(t), indicat-the debris included sno¥v, and muddy fog can being rapid motion durin_ : do¥vnstream tra¥'el.Figure 10 shows the situation at the source area of the "i2004 BHTTOU-DANI LANDSLIDES-DEBRIS FLO¥¥,FigF.1459. Continuous images of the May 2004 debris flow in the Bettou-tlani (Video courtesy of the Kanazawa Office of Rivers and NationalHrghwa,.Is, IMLII): Sliding mass is shown in white dotted iines: ¥Vllite color in thevhitc dotted lines is snowlandslide on 1 1 September 2005, more than one year afterwater flo¥v exited at W1, W2, and W3 at relatively hi**herthe landslide event. A man in the enlar'ged box can bepositions. On the other hand, at the lo ver part of L3,seen as a scale. According to the report of investigationthere ¥vere three ground¥vater exits ¥V4, W5 and W6.conducted soon after the event by KORNH-MLITThese groundwater exits ¥vere located in relative lower(2004b), the average slope angle was about 28 degrees,positions compared with W1, W2 and W3. It appearsand the average thickness of' the sliding mass ¥vasout into the valley. A cornmon phenomenon at the sourcethat the g:round¥vater level was different at the left andright parts, and the exits indicated the different ground¥vater veins. It is estimated that the phenomenon of thesliding mass in L3 not moving so far is due to the slidingmass at L3 being not fully saturated by the ground¥vaterflo v vhen the landslide occurred. This fact ensured thatthe debris, especially in the potential sliding zone, wasfully saturated and that high water pressure ¥vas suppliedto the back of the debris to make the slope unstable. Theground¥vater exiting at a high position at the head of theareas of these sliding blocks is that concentrated ground-debris ¥vas a major triggering factor for the landslideestimated as 30 m. In this figure, L1 , L,_, and L3 sho¥v therear boundaries of' three different sliding blocks, whichmoved for a limited distance from the rnain scarp;ho¥vever, most of these blocks did not move so far, butjust rested on the slope. At the middle block, bet¥veen L1and L3, most of the debris material slid out of the sourcear'ea, entered into the Bettou-dani, and joined the debrisflow. Also, at the lo¥ver part of' L2, most of the debris slid 2004 BETTOU-DANI LANDSLIDES-DEBRIS FLO¥¥*N1 " > 'l10Lead) .'Bet0-2 Bet0-3/:' ' 'ti hyt ' df 'f8OCQe)a)C(U6.- ,¥f ,,4 _fi,C::)l 47Beto-4(:a)Q)J:(a)2Toyoura silica sandCE/(Q/o'(/)l,2llllo 12 3 4 567Shear displacement (m)l1¥Fig. 14. Sample-height change with shear displacement duringI [] :'¥ /'f ete psrts Rots TsrtFig. 12. A half section of the sbear box and the close-up diagram ofthe edges (from Sassa et al., 2004a)constant-shear-speed dr _' ring-shear tests on samples Bet0-2Beto*3, Beto-4, and Toyoura silica sand: Normal stress =300 kPa,Shear vefocit) = 10.0 mm/s: The void ratios for the fouF samplesafter consolidation (before sl]earing) are 0.687, 0.760, 0.753 and0.901, respectivel)and is sensitive to pore-pressure monitoring, although themonitoring point is not at the center of the shear zone1 oo(Sassa et al., ,_004a).In this study, the rin_ : shear apparatus DPR1-5 wasemployed. The diameters of the outer ring and inner r'ingare 180 mm and 120 mrn, r'espectively. The sample, after) 80(!)>I*Q) 60placement in the shear box, had a donut shape with a:width of 30 mm. To avoid possible grain-size effects onthe shearing behavior, only grains ¥vith diameter smallerthan 4.75 rnm ¥vere included in the tested samples.Q)O)a 40C20ooi1ioGrain size (mm)Fig. 13. Grain-size distribution of soil samp!es taken from the sourcearea of the 2004 Iandslide and from the traveling path of the debrisflolvformation of the shear zone and the post-failure mobilityof high-speed landslides and observe the consequence ofmobilized shear resistance, as vell as the post-failureshear displacement and generated pore-water pressure(Sassa et al., 2004a). In this study, ring-shear tests wereconducted using ring-shear apparatus DPRI-5, Ivhich wasdeveloped by Sassa in 1996 (Sassa et al., 2003).One of the most important features in the developmentof the ring shear apparatus is the development of aneffective and durable pore-pressure monitoring system.To have a large inlet section and provide an averagepore-pressure value throughout the soil sample, porepressure transducers are connected to a gutter (4 x 4 mm)extending along the entire circumference of the inner vallof the outer ring in the upper box, as shown in Fig. 12.The gutter is located 2 mm above the shear surface and iscovered by t¥vo metal filters, ¥vith a filter cloth betweenthem. This system is quite durable in regard to shearingGRAIN-CRUSHING SUSCEPTIBILITY OF THEVALLEY DEPOSITS IN DIFFERENT PARTS OFTHE BETTOU-DANIIt is believed that the difference in grain-crushing sus-ceptibility should cause the difference in the travelingprocess of the landslide-debris flow. When the soil iseasy to be crushed, excess pore pressure ¥vill be easilygenerated durin*" the shearing process under rapid rnotion(means undrained condition), and in turn, the shearresistance will decrease and result in high mobility oflandslides. To check the grain-crushing susceptibility ofthe valley deposits, dry ring-shear' tests ¥vere conductedon the samples. The test conditions ¥vere: consolidate thesample at 300 kPa normal stress lvhich corresponds to theactual str'ess level of the landslide, and shear it underconstant speed of 10.0 mm/s until the shear displacementreaches 6.4m. For' comparison, Toyoura silica sand'hich is kno¥vn as a standard sandy soil that is difficult tocrush, ¥vas also sheared under the same test conditions.Figure 14 shows sample-height change during the dryr'ing-shear tests. Soil ¥vith high gr'ain-crushing susceptibi-lity generally has large sample-height change (contraction) during dry shear. The sample-hei_g:ht changes thatoccurred in the samples taken from Bett.ou-dani ¥verequite a bit larger than that of Toyour'a silica sand. ¥¥,ANG AND SASSA1481 oO(a)otted i le: ,before she ring80/'/se:id line: ;afiershearingo,5500CUJ*O!4.../'+"ll=/l '*>pore pre$sure (measured)e::0.350_*--ca,o40CQ$ _.././.,oQ)**･** Beto*3(DShear displ., ,21U)*CIS(1):50 1 oo 1 50 200 250 300 350 400o CDElapsed time (sec)400･ (b)Beto*4Residual failure lineoiGrain size (mm)CUCL:300Peak failure line2.70 33.7aa)(b)o(:oO(Uu)e)o) I200.-sta rtend TSP" 5(UooOEe)OBeto So olc:e)---= ･- h- Beto-2! ., /o**"'- Bet0-21 oo**･-･ Toyoura ss20 -15u,u)'-"- 8eto*4 ={$$s/ "/'.'Q)CL*･*･･ Toyoura ss/ .'::e)C:e)3C f200)c:cQa)4Shear resistance{60xPore pressure (appiied)300u)(t)ENorma! stre$s400e)/ "5(a)R101co(Da,ESP a=15.101 ooLllJ::(1)co)c IcO 1005c:(QO*200300 400 500Normai stress (kPa)300 (c)oToyourasil'esand8et0-2 Bet04endBeto-3semple sampie sampleF esidua tailure inexe) 200-Tested samples60033 7'oc:(UFig. 15. Grain crusl]ing occurred in the drl.' constant-shear-speed ringshcar tests on samples Bet0-2, Bet0-3. Bet0-4, and Toyoura si icasand: (a) Grain-size distribution of tlre tested samples before andt 100(Q(Dstart!:after shearing and (b) Marsal's grain crusl]ing susceptibtlit .･ Bp(defined b), Marsa , 1967)(1)oo I ooAmong the samples taken from Bettou-dani, Bet0-4 hasthe smallest sample-height change during shearing, sho¥vin,_,_a relatively lolver grain-crushing susceptibility.Figures 15(a) and 15(b) sho¥v the ,_._arain-size distribution200 400300Norrnal stress (kPa)500Fig. 16. Simulatiou test results of landslide iniriation tri( *gered b¥.rainfall under naturally drained condition: B )=0.96, Pore vaterpressure increasing rate = 0.5 kPa/s: (a) Time-series data, (b) Totalstress path (TSP) and pseudo effective stress path (ESP) and (c)Residual friction 2ngle of the tested soil sample Bet0-1 from theof the tested samples before and after shearing, and thegrain-crushing percentage Bp of all samples (Marsal,source area1967), respectively. Bp is the summation of the differenceof grain-size distribution at each sieve siz,e of the samplebefore and after dry shear (taken from shear zone), and itunit ¥veight of the slidin_g: mass, a avera_g:e ¥'alue of 18 kN/indicates the grain-crushing susceptibility of the soil. It ism3 was assumed in the test. Assuming the _"*,round¥vaterobvious that _ :rain-crushing susceptibility becomes lo¥vertable near the sliding surface, the initiai effective normalfrom the upstream part to the do¥vnstream part of theBettou-dani.stress ((To) and shear stress (ro) acting on the slidingsurface ¥vere 420 kPa and 224 kPa, respectively. Then,pore-water pressure acting on the element increased as theresult of rainfall and sno¥vmelt. The test ¥vas conductedunder the follo¥ving procedure:RING-SHEAR TESTS ON SOII, SAMPLES TAKENFROM THE SOIJRCF. AREAThe purpose of this test is to simulate the initiation ofthe landslide by vater pressure. The initial slope condition ¥vas simplified as bein*' 30 m in thickness (h) and 28degrees in slope angle (e). The landslide was triggered int,he ideal slope by rainfall and sno¥vmelt ¥vater. Throu_ghcT0=y*/1 cos2 e and r0=y*h cos e cos e, vhere, y* is the(1)Saturate the soil sample to a hi**h degr'ee of satura-tion with caTbon dioxide and de-aired water; it wasconfirmed that the BD Value (BD is a pore pressureparameter, related to the de*'ree of saturation in thedirect-shear state. It lvas propased by Sassa (1988))reached 0,96, sho 1'ing a high de_',_ree of saturation.(2)Consolidate the sample under normal stress of 420 ;.2004 BETTOU-DANI LANDSLIDES-DEBRIS FLO¥¥*kPa;149(a)(3) Apply the initial shear stress of '_'_4 kPagradually at41 .7 Pa/s to avoid pore-¥vater pressure generat.ion;!T d*fS:'/**' ;/;;･ i(x(4) Increase the pore-1vater pressure gradually at therate of 0.5 Pa/s through the upper drainage lineAalSlidingT Mass; "**WoFaDe r'sDe ositdirectly connecting to the upper surface of the sam-!,ople until failure occurs;(5) Measure the residual friction angle of the soil ¥vithconstant shear speed, ¥vhile increasing the normalstress gradually from a lo¥v stress le¥'el (about 90kPa) to a high stress level (about 400 kPa).Frgures 16(a) 16(b), and 16(c) present the test results.Figure 16(a) sho¥vs the time-series data for the ¥vhole testseries. From the beginning to nearly 200 sec, t.he normalstress and shear resistance were kept constant, vhile thepore pressur'e ¥vas increased gradually. From 200 sec toAAhlllCC _lllh=o(b)ACB cPAWO//BC=F<=Kd ' Aw330sec, srnail displacement occurred, and the shear'resistance mobilized a little bit higher, although the shear'stress lvas kept constant. The void ratio at 250 sec ¥vas0.350. After 330 sec, rapid f'ailur'e occurred, which can beconfirmed by the acceleration of the shear displacement.Corresponding to the rapidly increasing shear displacement, the shear resistance decreased rapidly to about I lO(,,c <; :?kPa. At that point, the apparent friction angle becamel jD/ :15.1 degrees, vhich is shown by the total stress path andeffective stress path in Fig. 16(b). The residual frictionangle of the soil ¥vas measured under complete drainedcondition as 33.7 degrees, ¥vhich is shown in Fig. 16(c),when the above test ¥vas finished. The procedure was toincrease the normal stress _ :radually (5.6Pa/s) fromabout 95 kPa to 405 kPa when keeping a constant shear4J:AecaNorrna stressFrg 17. Model for undrained loading of saturated deposits by adisplaced s:iding mass (Sassa et ai., 1997): (a) Illustration of themodel, (b) stress path of the torrent deposit during loading, a:angle of thrust bet veen the slope and the torrent bed, F : d,namicstress, kd: dynamic coefticient (Fd /A ;V)velocity. The shear velocity was set as slo¥v as 0.02 mm/szone. From the above test results, it is easy to calculateeffective stress state in the shear zone, because rhemeasured pore pressure is not directly from the shearthat the slope can remain stable at its initial slope angle ofzone. It ¥vas also affected by the supplied pore pressure.28 degrees, if there is no increase in pore pressure at theslidin_g: sur'face. In addition, from Fig. 16(b), it can beWhen pore pressure at shear zone is correctly measured,seen that the peak friction angle of the soil at initialfailure is much higher than 33.7 degrees.In Fi,.*,a. 16, there are some concepts that need to beresidual failure line. In the later part of this test, only theclarified. At first, naturally drained condition means thatin the test procedure drainage is not prevented and excesspore-water pressure can generate dependin_ : on materialThrough the above test aimin*" to simulate the failureprocess of a natural slope when the pore pressure actin*'to avoid excess pore pressure generation in the shearbehavior and loading rate, and it ¥¥'as referred to asnaturally drained conditions by Sassa et al. ('_004b).Under the naturally drained condition, it is easy to findout in Fig. 16(a), that there is a difference bet¥veen thepore pressure (applied) and pore pressure (measured).As sho¥vn in Fig. 12, t.he pore pressure transducer isconnected ¥vith the shear zone, also ¥vith the upperdrainage line through which pore pressure ¥vas supplied.When the pore pressure value from shear zone and upperdrainage line is different, the high value will be recoded bythe transducer. It is obvious that the high portion of thepore pressure (measured) was from shear zone. From thisdifference, it is estimated that high excess pore pressure_shear resistance should be replied on for data explanation.on the potential sliding surface was increased by theground¥vater table rise caused by heavy rainfail andsnowmelt, it is found that high excess pore pr'essure couldhave resulted, and in turn, the shear resistance of the soilat sliding surface could drop dol 'n rapidly. The resultantrapid drop-down of the shear resistance should causeacceleration of the landslide motion ¥vhen it moved downto the valley, and resulted in a high velocity lvhen itrushed into the valley.RING-SHEAR TESTS ON SOIL SAMPLES TAKENFROM THE LANDSLIDE TRAVEL PATH IN THEBETTOU-DAr '1was _ enerated in the rapid motion process after theThe above test simulated the initiation of rapid land-sample failure. Related to the above concept, the pseudoslide from natural slope. What lvill happen ¥vhen thefailed sliding mass rushed into the Bettou-dani valley,effective stress path (EPT) in Fi_ :. 16(b) is not the act.ualjthe effective stress path should move along peak or ¥VANG AND SASSA150Table l. Initial condrtion forundrained loadingon tl]evaile)' depositsfrom a rapid shding mass, Bettou-dani lands]ideho h**(m)(m)8 oorQas oo,,,,1;40ece)(deg.)Cl)Bet0-218)3lO30Bet0-318)3o7_oBet0-4))3o5(a)Normal stressShear stress20eoothe destroyed bridge; and Bet0-4 was taken below thesuspension bridge and near the toe of deposit of the800!(b)fr¥ N/1lf//V lLxFi**ure 17 is a model proposed by Sassa et al. (1997) todeposits by a rapidly sliding mass. The slidin*" massmoved do¥vn the slope (1), and applied load onto thetorrent deposits at the foot of the slope (II). Because asurface water stream or subsurface flow existed and someof the deposits ¥vere saturated, the torrent deposit ¥vas30,20E:r-¥': ¥ lNormal stressPoFe pressure:5u)u,a,400+1/510l'shear dispi1)E:rQu,(,) 200-Ce,Ea)V(U,:U):,lil,o 5 COe)Q)(1)Tesistance(1)o5 20o525oo30Elapsed time (sec){, (c) o: Ini al state1 oo L ESP TSP-- >; :1 ./ s!/ ... 2 6'2000+X*.l -f .･･" .-debris flo¥v.simulate the undrained-loading behavior of ¥'alley25Tirr}e (sec)e)* 500vhere thick torrent deposits ¥vere distributed? To simulate the landslide motion in the Bettou-dani, three other'samples (Bet0-2, Bet0-3, Bet0-4) from different parts ofthe Bettou-dani ¥vere sampled and used in rin_ -shear teststo show the fluidiz,ation process of the landslide (seeFig. 7(b)). Beto-2 was taken near the upper'most debrisretention dam in the Bettou-dani; Bet0-3 ¥vas taken near10 15 205(1)oo 600 700 80Dd oo200300400 500Norm 1 stress (kPa)Fig. 18. Simu]atton test results on sample Bet0-2 when sliding massrushed into the vallel_ and ioaded on the torrent deposits: (a)Applicd-stress signals (normal-stress and shear-stress increments),(b) Time-series data and (c) Effective stress path (ESP) and totalstress path (TSP), B =0.96sheared by undrained loadin*' and transported do vnstream together ¥vith the sliding mass (III). Here, acolumn ¥vith unit length of its sliding surface, ¥vhich is apart of the torrent deposit is assumed. In the position (1)of the sliding mass, the ¥vei**ht of the column (WO) ¥vas ineffect. When the sliding mass rode on to the torrentdeposit (II) ¥vith a certain velocity, it provided dynamicloading of the column. It is assumed that the appliedstress on the torrent deposits ¥vas the sum of the staticstress, W, (10ad due to the weight of the sliding mass) andthe dynamic (impact) stress, Fd, ¥vorking in the directionof motion of the sliding mass.At the Bettou-dani, the sliding mass moved down theslope (1), and applied a load to the valley deposits at thefoot of the slope (II). Because a surface-¥vater stream orsubsurface flo¥v existed and some of the deposits weresaturated, the valley deposit was sheared by undrainedloading and transported do¥vnstream together ¥vith thesliding mass (III) (Sassa et al., 2004a). The above testand Sassa et al. (2004a), it is reasonable for Kd to take avalue of unity. Then, the increment of normal stress andshear stress from the rapidly sliding mass to the depositscan be determined. The initial conditions for the threesampling points, ¥vhich were employ. ed in the rin*'-sheartests, are summarized in Table l. From the upstream todo¥vnstream, the slope angle ¥vas changed from 18de*'rees to 5 degrees near' the No. 10 debris retention dam.The initial thickness of the torrent deposits at the valley¥vas assumed to be the same value of 5 m, and the thickness of groundwater ¥vas assumed to be 3 m (ground¥vatertabie ¥vas 2 m below the torrent sur'face). The intrusionangle was assumed as 10 de*'rees for Bet0-2 sample nearthe source of the landslide from natural slope. It is thediff rence bet¥veen the slope angle of the initiated landslide and the slope angle of the valley bed.Arhen slidingoccurred at slope (1).To simulate the succeeding process, sample Beto-'- ¥1*asused to simulate the situation at slope (II), while samplesmass moved along the Bettou-dani valley, the intrusionangle became zero for Beto-3 and Bet0-4. Because of theeffect of the debris retention dam, the thickness of thesliding mass became thinner and thinner. Consideringthis phenomenon, the thickness of the sliding mass ¥vasBet0-3 and Bet0-4 were used to simulate the behavior atassumed to be 30m, 20 m and 5 m from upstream toslope (III), and the local slope an_ les of the valley at thedo¥vnstream.Figure 18 sho¥vs the results of the simulation test onsho¥vn in Fig. 16 corresponds to the landslide thatsampling points (Bet0-3 and Bet0-4) ¥vere considered.In Fig. 17, the valley deposit has a thickness of ho, aninitial slope an_gle of the valley g, and ground¥vaterthickness on the sliding surface /7, . The undrained10ading from a rapidly moving displaced landslide has athickness of A h, an intrusion angle of (x, and a dynamic(impact) coefficient of Kd. Based on Sassa et al. (1997)slope (II) using sample Bet0-2. Fi.･ure i8(a) sho¥vs theinput stress signals of normal stress and shear' stressbefore (0-5 sec), during (5l5 sec), and after the dynamicimpact process (15-30 sec). The signal ¥vas loaded on thesample under the undrained condition to simulate therapid loading of sliding mass on the torrent deposits, o）l）匙童9α隻9鼻轟ひ置）0 o 0躯ひωしノ1仁o）監oζω）亀o仁＞σ＞ぴ＞αo星9の口ごいooごご駆oΦω亘く吋①蹟7巽ヨヨ漏の聖9①σ帥一u。コ昌ヨ）ζ∫Q桝躍 竃 ヨの ㌦ → 謹． 7ゆハのΩ・誰，℃（窩o唱3弱器…：o轟帥諏ω聖→㌣虫尊肇①覧目鴇oビ ヨ 巴o①男器P（u弓釦ンずけロ鋤しウo → oooこ欝曽， oゑへけの（銭．o霞7野嵩に⇒ oo＝℃o鄭o鋤⊆L￠Lo） の鋤めドバ の の嵩塵仁 α §悪鐸 いしねの筥ヨぴQO Q弓の0り一の PG）の00り匂り旨。 図図O“｝0轡『q）ぐD I 匂り列 ロぐr鴇霞ε三 ε三”コ 僻ロリ（o 簾）篇♂羅蕗 ①臣uo 8§’星号 一零黛≦ （ωO＝匿 醐oリコo 臼nU噂嘉。諏 ”『 蕊 飴殺 唱臼請・守 くの・言 ①鶴一層 自o＝o写 嵩自o ”① 団一”o 角い『昌 雲露鴇さ＆言懇 o自謄昌ロハワ u羅ε≡i＝房 ゆ のや”三℃筥り のの撃蕪ハ の の怨ε魯富罫霧肩三i甥言巴包曽讐やあ ヨαQ囑 幽・跨【・σ灘題B緩号 ＝‘ro＝。 ハ ロゆ麟鎗 肇の＝’ 誰窺ど 鵠一唱浮 ののロけ 黛㌶覧守 ロしの ）彗ざo 閂鎚騒墾塁恥”顕再o「縛跨㌍ の この o薦ひコoo塁霧藝宅蕪騒箒：錯呂陀琶讐自・り房）三…．三竺欝 舅 りけ冨潟包霧PΩ‘r一く酔。・孚鼠o欝＿のQnりゆ ユロド儲Q岩πで（o器aδ蜂Noo 旧 o oΦ田ω猷鋤コ○でmω ゆ の6ヲ o oOi∋o里o9Φ ○ 『 ， ハ 富 りら 砿 → ω 自r ℃Shearresistance（kPa）oo㎝oo轟ZO訳貧8紹ωδ勉処∋8z9悼oo m の 刀 e’訴 r？・・1バ9 こン のS熱earresistance依Pa〉 一▲ 卜oOo ぐつ轟 し跨のの＃ヨZσo oShear dis診lacemenセ（★肇0”3m） ロ の こン の 8占o 一ム ヘ｝ ω σ肇1N一） lω沁1⑩OIO ｝ヨ1α例Φ一』1i“） 、て｝ 1ω父1o oへ》 ω … … …の ロ ロ oゆo8涙8鐸3z一一〇1 房 刃 しo 「 ［ ○ ジお ① ［o ＿ o o ＞ z 戸 ＞ z o しり ［ ε S葉ress（KPa〉 団 の ε 8 8 1 ⊂：N 切o 順 → → ○ ω ① 0 ￠ Φ 0 0つ o料盆oΦ①8 岬 ω嘗 仁）z ① ヨ〔D“譲ヨ量 OSセress and pressure（kPa〉一 N Nさi㊤iのωωζ 堺 裟i＄hear displacement（rn〉9鋤ω串』 σ｝o o oかQ Stress（kPa） 劇奮① ω o』一 ゆ ＼ l o t zlゴ 婁1幕一 σコ o の の ロooo盤ωP①o（Dヨ瞬冨℃ωΦ晶Ω，qo I 曾1 −l I o o oo ロ くつ こンStress and蓼）ressure（kPa〉 N 4』』 σ》，．．翻 152¥¥,ANG AND SASSAFrom the above simulation tests that reproduced rapidJoint Research Programme of Disaster Preventionloadin_ : on valley deposits, the impact process, the travel-occurred in May 2004 ¥vere ¥vell reproduced in the labora-Research Institute (DPRI), Kyoto University are highlyappreciated. Dr. Huabin Wang, Mr. Ryuta Saito, lvlr.Jozef Jurko, and Mr. Taichi Minamitani of the Researchtory.Centr'e on Landslides (RCL), Disaster Preventioning process, and depositing process of the debris flo¥v thatCONCLUSIONSThe May 2004 Iandslide-debris fiow that occurred inthe Bettou-dani of the Jinnosuke-dani landslide, Haku-san Mountain, sho¥ved a fluidization process fromResear'ch Institute, Kyoto University, joined the samplingand field investigatlon.REFERENCESl) Kanaza¥va Office of Rivers and Natioual High¥vays. Ministry oflandslide to debris fio v. By analysis of the monitoredLand, Infrastructure and Transporvideo ima*"es of the debris flo¥v, field investigation of theRepol't on Jjnnosl!ke-Dani Larlds!ic!e (in ,Iapanese)source area of the landslide, and laboratory. ring-sheartests that simulated the rainfall tri**_ :ering mechanism andthe fiuidization mechanism during the process of do¥vnstream travel, the follo¥ving vere concluded:(1) Concentrated ground¥vater flo¥vs ¥vere a main tri**gering factor for the landslide initiation by increasing water pressure in the slope;(2) In the ring-shear simulation test of the landslideinitiation, it ¥vas shown that even under naturallydrained conditions, the mobilized shear resistance ofthe ¥veathered soil in the source area sho¥ved a rapiddecrease after landslide initiation, and this should bethe instinctive factor for rapid landslide motionafter its initiation;(3) In the ring-shear simulation test of dynamic loadingon the valley deposits, it ¥vas shown that hi_ghpotential for grain-crushing of upstream depositsand lo¥ver potential of the do¥vnstream depositscontrolled the traveling and depositing process ofthe debris flo¥v;(4) The shear resistance at steady state under undrainedconditions is the same for the soil samples takenfrom different parts of the valley (Sample Beto-2, 3,4). A possible reason is that although the initialgrain gradations of these samples differ at the initialstate, the soil at the shear z,one ¥vould become thesame ¥vhen the shearing process reached the steadystate, ¥vhen all of the possible grain-cr'ushing iscompleted.of Japan ('-004a): Investigation2) Kanazawa Office of Rivers and Nationa Highlvays, lvlinistry ofLand, Infrastructure and Transport of Japan (2004b): Debris o voccurred on 17 h,1ay 2004 in Bettou-clani, NeTt J!etter SaboHakusan, 6, l4 (in ,Japanese)3) Kanaza¥va Ofnce of Rivers and National Hi_ h¥vays, lvlinistry ofLand, Infrastructure and Transport of Japan (2004c):http: //)_1 O. 1 3 1 .8. 1 2/ - kanaza¥va/mb5kouhou lpress /ne¥vs .html.4) Kaseno. Y. (1993): Geo!ogica! .,Vfapping of Ishika va Ceo!og.)'Bu[lelin (in Japanese)^5) Kaseno, Y (2001): Suppleme,u ofCeo!ogica! Jt(Iappi,1g oflshikalt'aGeo!o*"_v Bu!!etin (in Japanese).6) h,Iarsal, R. J. (1967) Large scale tes in_'* of rockfill materials, ASC_EJ. Soil l ifecll. Fozlnd. Div., 93 (S.M?_), 27-43.7) O_ kuno, T., ¥Vang, F¥Vand ivlatsumoto, T. (2004): Thedef'orming characters of he Jinnosuke-dani lands ide in Haku-sanmountainous area, Japan, Lands!ides, Eva!uation & Stabi!ization(eds. by Lacerda, ¥V., Ehrlich, h,i , Fontoura S_, Sayao, A.), P,-oc^I_X InrS.}vnp. Lanc!s!ides, Rio de .Janeiro, 2, 127917_85^8) Sassa, K. (1988): CJeotechnical model for he motion of landslides,Specia! I,eclure of 5rll Inr. S;*mp. LancJs!ides, Landslides, l0-15July, 1, 37-55.9) Sassa, K., Fukuoka. H^ and ¥Van_g, F. ¥V. (1997): l¥,iechanism andrisk assessmem of landslide-triggered-debris fio¥vs: Lesson from the1996.12.6 Otari debris fio¥v disasler, Nagano, Japan, Lands!ideRisk Assessnle,It (eds by Cruden D. ,i., Fell R.), Proc. Int-Tfibrkshop oil Lands!ide Risk A,ssessmenr, Honolulu, 9-21February, 347356.IO) Sassa, K., ¥¥rang, G. and Fukuoka, H. (2003): Performin_ :undrained shear tests on saturated sands in a ne¥v intelligentype ofring-shear apparatus, Geolech. Test. J., ASTi¥,1, 26 (3), 257-265.ll) Sassa, K., Fukuoka, H., ¥Vang. Cj. and Ishikalva. N^ (2004a):Undrained dynamic-loadin_ : ring-shear apparatus and its application to landsiide dynamics. Landslides." J. Int. Consortium orl L(!nc!s!ides, 1(1), 7-19.17_) Sassa, K., ¥Vang, G , Fukuoka, H., ¥¥rang, F. ¥¥r , Ochiai. T.,Sugiyama, lvl, and Sekiguchi, T. ()_004b): Landslide risk evaluationand hazard mapping for rapid and long-travel landslides in urbanACKNOWLEDC.MF,NTSDeep thanks are *'iven to the Kanaza¥va Office of Riversand National High¥vays. MLIT, for cooperation in thefield ¥vork and as a source of information on the May2004 Iandslide-debris flow. Financial supports byresearch **rants (No. 15310127, Representative: F. W.Wang) from the Ministry of E.ducation, Culture, Sports,Science, and Technology of Japan (MEXT), and 16G-03development area, Lanc!slides.' .J. Int. Consortiunl on Lands!ides, 1(3), 27_1-235.13) ¥Van_9:, F. ¥ r.. Okuno, T, and Matsumoto. T. (2004): Deformationstyle and infiuential factors of Ehe giant Jinnosuke-dani landslidein Japan. Proc. 15th Sout/1easr Asian Geotech. Conf., 1, 399-40414) ¥¥ran_ , F. ¥¥r., Okuno. T. and l¥,1atsumoto, T. (2007): Deforrnationcharacteris ics and influential f'actors for the ziant Jinnosuke-danilandslide in the Haku-san h,10un ain area. Japan. I,ailds[ides.' JIn!Consoriiinn on Lanc!s!ides. DOI lO.1007/sl0346-006-0049-9,4(1) (in press).
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