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Japanese Geotechnical Society Standard (JGS1437-2014) Method for dynamic cone penetration test

タイトル Japanese Geotechnical Society Standard (JGS1437-2014) Method for dynamic cone penetration test
著者 The Japanese Geotechnical Society
出版 Japanese Geotechnical Society Standard (JGS1437-2014) Method for dynamic cone penetration test
ページ 発行 2021/03/15 文書ID os202103150002
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  • Japanese Geotechnical Society Standard (JGS1437-2014) Method for dynamic cone penetration test
  • 著者
  • The Japanese Geotechnical Society
  • 出版
  • Japanese Geotechnical Society Standard (JGS1437-2014) Method for dynamic cone penetration test
  • ページ
  • 発行
  • 2021/03/15
  • 文書ID
  • os202103150002
  • 内容
  • Japanese Geotechnical Society StandardJGS1437-2014(E)Method for dynamic cone penetration test1ScopeThis document covers the determination of the resistance of soils and soft rocks in situ to the dynamicpenetration of a cone.A hammer of a given mass and given height of fall is used to drive the cone. The penetrationresistance is defined as the number of blows, Nd, required to drive the cone over a defined distance. Acontinuous record is provided with respect to depth but no samples are recovered. Nd can be used toestimate rigidity and degree of compaction of soils.This document is applied to medium and heavy types of dynamic cone penetration test (DCPThereafter) having different values of specific work per blow as follows:medium DCPT: DCPT with specific work per blow equal to 98 kJ/m2.heavy DCPT: DCPT with specific work per blow equal to 196 kJ/m2.NoteMedium DCPT is equivalent to DPM (medium) an heavy DCPT is equivalent to DPSH(super heavy-A) specified in ISO 22476-2 Geotechnical investigation and testing -Field testing- Part2: Dynamic probing, 2005.The test results of this document are suited for the determination of a bearing stratum. They are alsoused for detecting very loose soils, cavities, fills and refilled soils. They may also be used for thedetermination of the soil properties together with direct investigations (e.g. soil sampling).2Normative referencesNone.3Terms and definitionsFor the purpose of this document, the following terms and definitions apply.3.1Dynamic cone penetration test© JGS 2021 – All rights reserved1 test to drive the cone into the ground with a specific work per blow3.2Drive-weight assemblydevice consisting of the hammer, the hammer fall guide, the anvil and the automatic drop system3.3Hammerportion of the drive-weight assembly which is successively lifted and dropped to provide the energythat accomplishes the penetration of the cone3.4Hammer fall guideportion of the drive-weight assembly which leads the free fall of the hammer to the anvil3.5Anvilportion of the drive-weight assembly that the hammer strikes and through which the hammer energypasses into the drive rods3.6Cushion; Dampermaterial placed upon the anvil to minimize noise and damage to the equipment3.7Automatic drive-weight assemblydevice consisting of the hammer, the hammer fall guide and the drop system, which provides the freefall of the hammer3.8Height of fallfree fall of the hammer after being released3.9Drive rodsrods that connect the drive-weight assembly to the cone3.10Conepointed conical probe used to measure the resistance to penetration and the mantle (see Figure 1)3.11Nd-valuenumber of blows required to drive the cone the defined distance of 200 mm© JGS 2021 – All rights reserved2 Note 1As the specific work per blow is different between the medium and heavy DCPTs, theresulting Nd-values are different.Note 2Nd-value specified in JGS 1433(Portable Dynamic Cone Penetration Test Method) is numberof blows required to drive the cone the defined distance of 100 mm. As specific work per blow of theportable dynamic cone penetration test is different from that of the medium DCPT or the heavy DCPT,Nd-value obtained in the portable dynamic cone penetration test is different from those obtained in themedium DCPT or the heavy DCPT.3.12Specific work per blowEnvalue calculated byEn = m×gn×h/Awherem is the mass of the hammer;gn is the standard acceleration due to gravity;h is the falling height of the hammer;A is the nominal base area (calculated using the base diameter D)3.13TorqueMvdevice consisting of sensors for measuring number of blows, penetration length and torque, andrecording system3.14Automatic measuring and recording devicedevice consisting of sensors for measuring number of blows, penetration length and torque, andrecording system3.15Penetration lengthtotal length of the cone and the rods that penetrated into the groundThe distance between the cone base to the cone tip is not included in thepenetration length. The penetration length does not necessarily coincide to the depth ofcone base when the verticality of the rods are not maintained.Note4EquipmentAn example of dynamic cone penetration test equipment is shown in Annex A.© JGS 2021 – All rights reserved3 4.1Driving deviceDimensions and masses of the components of the driving device are given in Table 1. The followingrequirements shall be fulfilled:a)hammer shall be conveniently guided to ensure minimal resistance during the fall;b)automatic release mechanism shall ensure a constant free fall, with a negligible speed of thehammer when released and no induced parasitic movements in the drive rods;c)steel drive head or anvil should be rigidly connected to the top of the drive rods. A looseconnection can be chosen.4.2AnvilThe anvil shall be made of high strength steel. A damper or cushion may be fitted between thehammer and anvil.4.3ConeThe cone of steel shall have the geometrical properties shown in Figure 1 and Table 1. The cone shallhave an apex angle of 90 degrees and an upper cylindrical extension mantle and transition to theextension rods. The cone may be either recovery or disposable type, which have the sameconfiguration.NoteThe recovery type cone can be recovered when the rods are extracted after the test. It isrecommended to use the recovery type cone that is free from the rotation of the rods duringmeasurement of the torque. The disposal type cone cannot be recovered after the test and isremained in the ground. When using a disposable cone the end of the drive rod shall fit tightly into thecone. Alternative specifications for the cones are given in Figure 1.4.4Drive rodsThe rod shall have dimensions and masses given in Table 1, and shall be of a high-strength steel withthe appropriate characteristics for the work to be performed without excessive deformations andwear.The rods shall be flush jointed, shall be straight and may have spanner flats. The deflection at the midpoint of an extension rod measured from a straight line through the ends shall not exceed 1 in 1000(0.1 %), i.e.1 mm in 1 m.4.5Torque measuring deviceThe torque necessary to turn the driving rods is measured by means of a torque wrench or similarmeasuring device. Spanner flats of a rod may be used when using the torque wrench. The apparatusshall be able to measure a torque of at least 100 Nm or 200 Nm and be graduated to read at least in 5Nm or 10 Nm increments, respectively, for the medium and the heavy types of DCPT.A sensor for recording the torque may be used.© JGS 2021 – All rights reserved4 Table 1 - Dimensions and masses for the medium and heavy types of dynamic conepenetration testing apparatusDynamic ConePenetration TestApparatusDriving devicehammer massheight of fallmaximumtotala)massAnvildiameter b)mass (max.) c)Conenominal base areabase diametermantle lengthlength of cone tipDrive rodsmass (max.)diameter ODrod deviationSymbol UnitMediumHeavymhkgmmkg30.0± 63.5 ± 0.50.3500 ± 10350 ± 10 11570dmmmkg50 < d < Dh 50 < d <a)0.5Dh1818ADLLcmm2mmmmmm1 05236.62.069.03.018.32.01 590± 45.0 ± 2.090.0 ± 2.0± 22.5 ± 2.0±kg/m 5.06.7mm 28.0± 32.0 ± 0.4%0.40.10.1Note a) hammer mass that is applied to the rod after blowNote b) Dh is the outer diameter of hammerNote c) guide rod included© JGS 2021 – All rights reservedmdr5 dr1drdr51153L44LKey1: Rod凡例2: Cone tip1:ロッド3: Cone2:コーン先端4: Mantle3:コーン5: Rotation free4:マントルconnectionL:Mantle length5:差込み接続D:Base diameterL:マントル長さdr:Rod diameterD:底部直径5dr:ロッド外径Key1: Rod2: Cone tip3: Cone4: Mantle5: Rigid connectionL:Mantle lengthD:Base diameterdr:Rod diameter3390゜2L42D(a) recovery type290゜D(b) disposal type90°90°Figure1-Alternative forms of cones for dynamic cone penetration testD4.6Optional equipment4.6.1 Automatic measuring deviceA device to count the number of blows of the hammer by measuring mechanical or electricimpulses can be placed on the system. The penetration length may be measured using a sensor thatshall have a resolution better than 2 mm.4.6.2 Device to control rod string deviation from the verticalA system or guide for supporting the protruding part of the rods should be in place to ensure andcheck that the drive rods are maintained in a vertical alignment.4.6.3 Rod extraction deviceRod extraction device is used to extract the rods after the test, and shall have a sufficient capacity ofextraction.© JGS 2021 – All rights reserved6 55.1Test procedureSelection of DCPT deviceThe test shall be carried out with the appropriate selection of either of the medium or the heavy DCPTapparatus, according to soil conditions, site conditions and purpose of the test.5.2Equipment checks and calibrationsPrior to each test, a check of dimensions shall be made to ensure that they are within the valuesgiven in Table 1. The straightness of the rods shall be checked once on each new site and at leastevery 20 penetration tests at that site. After each test, a visual check of the straightness of the rodsshall be made.At the test site, the rate of blows, the height of fall, the friction free fall of the hammer, the propercondition of the anvil and the mechanical release devices shall be checked for satisfactory operationwhich is to be ensured for the whole test series. In addition, the proper functioning of the recordingdevice has to be checked in case automatic recording equipment is used.The precision of the measuring instruments -if applicable- shall be checked after any damage,overloading or repair and at least once every six months, unless the manufacture's manual requiresshorter inspection intervals. Faulty parts shall be replaced. Calibration records shall be kept togetherwith the equipment.5.3Test preparationIn general, DCPT is performed from the ground surface.DCPT equipment shall be set up with the penetrometer vertical, and in such a way that there will beno displacement during testing. The inclination of the driving mechanism and the driving rodprojecting from the ground shall not deviate by more than 2 % from the vertical.Trailer-mounted DCPT equipment shall be supported in such a way that the suspension travel of thesupport trailer cannot influence the test.The equipment shall be set up with appropriate clearance from structures, piles, boreholes etc., inorder to be certain that they will not influence the result of the DCPT.When carrying out DCPT in situations where the rods are free to move laterally, for instance overwater or in boreholes, the rods shall be restrained by low-friction supports in order to prevent bendingduring driving.5.4Test execution© JGS 2021 – All rights reserved7 The drive rods and the cone shall be driven vertically and without undue bending of the protrudingpart of the extension rods above the ground. The verticality of the rods should be less than 2 % fromthe vertical. If the verticality of the rods exceeded 5 %, this situation shall be reported.The penetrometer shall be continuously driven into the ground. The driving rate shall be kept between15 and 30 blows per minute. All interruptions longer than 5 minutes shall be recorded.The number of blows, Nd, shall be recorded every 200 mm penetration.In cases of DCPT in soft clays where the driving resistance is very low, penetration distance per blowmay be recorded.Penetration distance of the cone due to the self-weight of the equipment shall be recorded, ifoccurred.NoteIf the cone is penetrated during successive blows due to the self-weight of the equipment,the next blow shall be conducted after the penetration due to the self-weight almost ceases.The rods shall be rotated 1½ turns or until maximum torque is reached at least every 1.0 mpenetration. The maximum torque required to turn the rods shall be measured using a torquemeasuring wrench or an equivalent device and shall be recorded. During heavy driving, the rods shallbe rotated 1½ turns after every 50 blows to tighten the rod connections.If the penetration distance does not reach 200 mm by 200 blows for the medium DCPT and by 100blows for the heavy DCPT, the test may be terminated. The penetration distance at the terminationshall be recorded. In cases where Nd greater than 100 for the medium DCPT and Nd greater than 50for the heavy DCPT is successively recorded 5 times, the test may be terminated.After the termination of the test, driving equipment shall be dismounted and the rods shall beextracted using rod extraction device. Visual inspection of the rods shall be made after the test.5.5Safety requirementsNational safety regulations shall be followed.6Test resultsThe test results shall be reported as values of Nd and Mv with penetration length.77.1ReportingField report7.1.1 General© JGS 2021 – All rights reserved8 At the project site, a field report shall be completed. This field report shall consist of measured valuesand test results, if applicable.All field investigations shall be reported such that third persons are able to check and understand theresults.7.1.2 Record of measured values and test resultsAt the project site, the following information shall be recorded for each test. Note that item with *symbol shall be included. The other item should be included, if applicable.a)general information:1) name of the client;2) name of the contractor;3) job or project number;4) name and location of the project;5) * name and signature of the test equipment operator in charge;b) information on the location of the test:1) * date and number of test;2) field sketch (to scale or not to scale);3) * ground elevation referred to a fixed point;4) x, y, z co-ordinates of the location of the penetration test;5) operation on land or water;c)information on the used test equipment:1) * type of dynamic probing (medium or heavy);2) manufacturer, model and number of the test equipment;3) type of cone (disposable or fixed);4) type of anvil(fixed or loose);5) use of dampers or cushions;d) information on the test procedure:1)weather condition;2)documentation of the equipment check and calibration conducted in accordance with 5.1;© JGS 2021 – All rights reserved9 3) *test record with:- Nd-value with penetration length;- Mv-value with penetration length;- penetration distance per blow, if applicable;- penetration distance, if the test was terminated before the penetration distance did notreach 200 mm;- penetration distance due to the self-weight of the equipment, if occurred;4)blow count frequency when operating the equipment;5)groundwater level, artesian conditions, if known;6) *all unusual events or observations during the operation (e.g. malfunction of theequipment);7)observations on the recovered cone and/or rods;8) *all interruptions during the work, with time duration and change of rod;9) *reasons for early end of the test;10)* observations for the rods when the verticality of the rods exceeded 5 % (e.g. penetrationlength, reasons).7.2 Test reportFor checking the quality of the data, the test report shall include the following in addition to theinformation given in 7.1:a)field report (print out);b)graphical representation with respect to depth of the following data:- graph of Nd in the horizontal axis and penetration length in the vertical axis;- graph of Mv in the horizontal axis and penetration length in the vertical axis;c)any limitations of the data (e.g. irrelevant, insufficient, inaccurate or adverse test results);d) name the field manager.The test results shall be reported about in such a fashion that third persons are able to check andunderstand the results.© JGS 2021 – All rights reserved10 Annex A(informative)Example of dynamic cone penetration test apparatus.An example of dynamic cone penetration test apparatus is shown in Figure A.1.貫入量スケールパイプPipe for measuring(200㎜間隔)penetrationlengthマストMast(200 mm scale division)レベルLevelハンマーガイドHammer guideハンマーHammer打撃カウンターBlownumber counter緩衝材 materialCushionアンビルAnvilロッドRodガイドローラーGuide rollerコーンConeFigure A.1-An example of dynamic cone penetration apparatus© JGS 2021 – All rights reserved11 Japanese Geotechnical Society Standard (JGS1437-2014)Method for dynamic cone penetration testPublished byThe Japanese Geotechnical Society4-38-2 Sengoku, Bunkyo-ku, Tokyo 112-0011, JapanE-mail: jgs@jiban.or.jpURL: https://www.jiban.or.jp/e/C 2021 The Japanese Geotechnical Society○All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means electronic ormechanical, including photocopying, recording or any information storage and retrieval system now known or tobe invented, without written permission from the publisher.ISBN978-4-88644-115-7
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