1、Designation: D 6243 08Standard Test Method forDetermining the Internal and Interface Shear Resistance ofGeosynthetic Clay Liner by the Direct Shear Method1This standard is issued under the fixed designation D 6243; the number immediately following the designation indicates the year oforiginal adopti
2、on or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a procedure for determining theinternal shear resi
3、stance of a Geosynthetic Clay Liner (GCL) orthe interface shear resistance between the GCL and an adjacentmaterial under a constant rate of displacement or constantstress.1.2 This test method is intended to indicate the performanceof the selected specimen by attempting to model certain fieldconditio
4、ns.1.3 This test method is applicable to all GCLs. Remolded orundisturbed soil samples can be used in the test device.1.4 This test method is not suited for the development ofexact stress-strain relationships within the test specimen due tothe nonuniform distribution of shearing forces and displace-
5、ment.1.5 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establis
6、h appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 698 Test Methods for Laboratory Compaction Character-istics of Soil Using Stand
7、ard Effort (12 400 ft-lbf/ft3(600kN-m/m3)D 1557 Test Methods for Laboratory Compaction Charac-teristics of Soil Using Modified Effort (56,000 ft-lbf/ft3(2,700 kN-m/m3)D 2435 Test Methods for One-Dimensional ConsolidationProperties of Soils Using Incremental LoadingD 3080 Test Method for Direct Shear
8、 Test of Soils UnderConsolidated Drained ConditionsD 3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD 4439 Terminology for GeosyntheticsD 6072 Guide for Obtaining Samples of Geosynthetic ClayLiners
9、3. Terminology3.1 DefinitionsFor definitions of terms relating to soil androck, refer to Terminology D 653. For definitions of termrelating to GCLs, refer to Terminology D 4439.3.2 Definitions of Terms Specific to This Standard:3.2.1 adhesion, ca, nthe shearing resistance between twounlike materials
10、 under zero normal stress.3.2.2 angle of friction, n(angle of friction of a material orbetween two materials, ,) the angle whose tangent is the ratiobetween the limiting value of the shear stress that resistsslippage internal to a body or between two solid bodies at restwith respect to each other an
11、d the normal stress across thecontact surface.3.2.3 atmosphere for testing geosynthetics, nair main-tained at a relative humidity of between 50 and 70 % andtemperature of 21 6 2C (70 6 4F).3.2.4 coeffcient of friction, na constant proportionalityfactor relating shear to normal stress for a defined f
12、ailurecondition.3.2.5 cohesion c, nshear strength of material, or theinterface between two materials, at zero normal stress; thecomponent of the shear strength indicated by the term c,inCoulombs equation t =c+ sntan (f).3.2.6 direct shear friction test, nfor GCLs, a procedure inwhich the internal GC
13、L or the interface between a GCL andany other surface, under a constant normal stress specified bythe user, is stressed to failure by the relative movement of one1This test method is under the jurisdiction of ASTM Committee D35 onGeosynthetics and is the direct responsibility of Subcommittee D35.04
14、on Geosyn-thetic Clay Liners.Current edition approved July 1, 2008. Published August 2008. Originallyapproved in 1998. Last previous edition approved in 2006 as D 624306.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annu
15、al Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.surface against the other for interface strength and by internalshear for in
16、ternal strength.3.2.7 GCL, na manufactured hydraulic barrier consistingof clay bonded to a layer, or layers, of geosynthetic materials.3.2.8 residual strength, nvalue of shear stress at suffi-ciently large displacement that shear stress remains constantwith continued shearing.3.2.9 post-peak strengt
17、h, nvalues of shear stress at somedisplacement beyond the peak shear strength where the shearstress approaches a constant value with continued displace-ment.4. Summary of Test Method4.1 The shear resistance internal to the GCL or between aGCL and adjacent material, or between any GCL combinationsele
18、cted by the user, is determined by placing the GCL and oneor more contact surfaces, such as soil, within a direct shearbox. A constant normal stress representative of field stresses isapplied to the specimen, and a tangential (shear) force isapplied to the apparatus so that one section of the box mo
19、vesin relation to the other section. The shear force is recorded asa function of the horizontal displacement of the moving sectionof the shear box.4.2 The test is performed for a minimum of three differentnormal stresses, selected by the user, to model appropriate fieldconditions. The peak shear str
20、esses, or shear stresses at somepost-peak displacement, or both, are plotted against the appliednormal stresses used for testing. The test data are generallyrepresented by a best fit straight line through the peak strengthwhose slope is the coefficient of friction for peak strengthbetween the two ma
21、terials where the shearing occurred, orwithin the GCL. The y-intercept of the straight line is thecohesion intercept for internal shearing or adhesion interceptfor interface shearing. A straight line fit for shear stresses atsome post-peak displacement is the post-peak interfacestrength between the
22、two materials where the shearing oc-curred, or the post-peak internal strength within the GCL. If thepost-peak shear stresses have reached a constant value less thanthe peak strength, the post-peak strength is the interfaceresidual strength or the internal residual strength.5. Significance and Use5.
23、1 The procedure described in this test method for the shearresistance for the GCL or the GCL interface is intended as aperformance test to provide the user with a set of design valuesfor the test conditions examined. The test specimens andconditions, including normal stresses, are generally selected
24、 bythe user.5.2 This test method may be used for acceptance testing ofcommercial shipments of GCLs, but caution is advised asoutlined in 5.2.1.5.2.1 The shear resistance can be expressed only in terms ofactual test conditions (see Note 1 and Note 2). The determinedvalue may be a function of the appl
25、ied normal stress, materialcharacteristics, size of sample, moisture content, drainageconditions, displacement rate, magnitude of displacement, andother parameters.NOTE 1In the case of acceptance testing requiring the use of soil, theuser must furnish the soil sample, soil parameters, and direct she
26、ar testparameters.NOTE 2Testing under this test method should be performed bylaboratories qualified in the direct shear testing of soils and meeting therequirements of Practice D 3740, especially since the test results maydepend on site-specific and test conditions.5.2.2 This test method measures th
27、e total resistance to shearwithin a GCL or between a GCL and adjacent material. Thetotal shear resistance may be a combination of sliding, rollingand interlocking of material components5.2.3 This test method does not distinguish between indi-vidual mechanisms, which may be a function of the soil and
28、GCL used, method of material placement and hydration,normal and shear stresses applied, means used to hold the GCLin place, rate of horizontal displacement, and other factors.Every effort should be made to identify, as closely as ispracticable, the sheared area and failure mode of the specimen.Care
29、should be taken, including close visual inspection of thespecimen after testing, to ensure that the testing conditions arerepresentative of those being investigated.5.2.4 Information on precision between laboratories is in-complete. In cases of dispute, comparative tests to determinewhether a statis
30、tical bias exists between laboratories may beadvisable.5.3 The test results can be used in the design of GCLapplications, including but not limited to, the design of linersand caps for landfills, cutoffs for dams, and other hydraulicbarriers.5.4 While the peak strengths and post-peak strengths mea-s
31、ured by this test are generally reproducible by multiplelaboratories, the displacement at which peak strength andpost-peak strength occurs and the shape of the shear stress-horizontal displacement curve may differ considerably fromone test device to another due to differences in specimenmounting, gr
32、ipping surfaces and material preparation. The userof results from this standard is cautioned that results at aspecified displacement may not be reproducible across labora-tories and that the relative horizontal displacement measured inthis test at peak strength may not match relative horizontaldispl
33、acement at peak strength in a field condition.6. Apparatus6.1 Shear DeviceA rigid device to hold the specimensecurely and in such a manner that a uniform shear forcewithout torque can be applied to the tested interface. Thedevice consists of both a stationary and moving container, eachof which is ca
34、pable of containing dry or wet soil and are rigidenough to not distort during shearing of the specimen. Thetraveling container must be placed on firm bearings and rack toensure that the movement of the container is only in a directionparallel to that of the applied shear force.NOTE 3The position of
35、one of the containers should be adjustable inthe normal direction to compensate for vertical deformation of the GCL,soil and adjacent materials.6.1.1 Square or rectangular containers are recommended.They should have a minimum dimension that is the greater of300 mm (12 in.), 15 times the d35of the co
36、arser soil used in thetest, or a minimum of five times the maximum opening size (inplan) of the geosynthetic tested. The depth of each containerD6243082should be at least 50 mm (2 in.) or six times the maximumparticle size of the coarser soil tested, whichever is greater.NOTE 4The minimum container
37、dimensions given in 6.1.1 are guide-lines based on requirements for testing most combinations of GCLs andadjacent materials. Containers smaller than those specified in 6.1.1 can beused if it can be shown that data generated by the smaller devices containno bias from scale or edge effects when compar
38、ed to the minimum sizedevices specified in 6.1.1. The user should conduct comparative testingprior to the acceptance of data produced on smaller devices. For directshear testing involving soils, competent geotechnical review is recom-mended to evaluate the compatibility of the minimum and smaller di
39、rectshear devices.6.2 Normal Stress Loading Device, capable of applying andmaintaining a constant uniform normal force on the specimenfor the duration of the test. Careful control and accuracy (62%) of normal force is important. Normal force loading devicesinclude, but are not limited to, weights, p
40、neumatic or hydraulicbellows, or piston-applied stresses. For jacking systems, thetilting of loading plates must be limited to less than 2 from theshear direction during shearing. The device must be calibratedto determine the normal force delivered to the shear plane.6.3 Shear Force Loading Device,
41、capable of applying ashearing force to the specimen at a constant rate of horizontaldisplacement. The horizontal force measurement system mustbe calibrated, including provisions to measure and correct forthe effects of friction and tilting of the loading system. The rateof displacement should be con
42、trolled to an accuracy of 610 %over a range of at least 6.35 mm/min (0.25 in./min) to 0.025mm/min (0.001 in./min). The system must allow constantmeasurement and readout of the applied shear force. Anelectronic load cell or proving ring arrangement is generallyused. The shear force loading device sho
43、uld be connected tothe test apparatus in such a fashion that the point of the loadapplication to the traveling container is in the plane of theshearing interface and remains the same for all tests. (See Note5).NOTE 5The operating range of normal stresses for a device should belimited to between 10 a
44、nd 90 % of its calibrated range. If a device is usedoutside this range, the report shall so state and give a discussion of thepotential effect of uncertainties in normal stress on the measured results.6.4 Displacement Indicators, for providing continuous read-out of the horizontal shear displacement
45、, and if desired, verticaldisplacement of the specimen during the consolidation or shearphase, or both. Displacement indicators, such as dial indicators,or linear variable differential transformers (LVDTs), capable ofmeasuring a displacement of at least 75 mm (3 in.) forhorizontal displacement and 2
46、5 mm (1 in.) for vertical dis-placement are recommended. The sensitivity of displacementindicators should be at least 0.02 mm (0.001 in.) for measuringhorizontal displacement and 0.002mm (0.0001 in.) for measur-ing vertical displacement.6.5 GCL Clamping Devices, required for fixing GCL speci-mens to
47、 the stationary section or container, the travelingcontainer, or both, during shearing of the specimen. Clampsand grips shall not interfere with the shearing surfaces withinthe shear box and must keep the GCL specimens flat duringtesting. Gripping surfaces must develop sufficient shear resis-tance t
48、o prevent non-uniform displacement of the GCL andadjacent geosynthetics. Gripping surfaces must develop suffi-cient shear resistance to prevent tensile failure within anygeosynthetics material outside the specimen area subjected tonormal stress. Where the internal shear resistance of the GCLis to be
49、 measured, rough (textured) surfaces must be used onthe top and bottom of the GCL to force internal shearing withinthe GCL. These surfaces must permit flow of water into and outof the test specimen. Work is still in progress to define the besttype of rough surfaces. Selection of the type of rough surfaceshould be based on the following criteria:6.5.1 The gripping surface should be able to mobilize fullythe friction between the gripping surface and the outsidesurfaces of the GCL:The rough surfaces must be able toprevent slip between the GCL and the gripping surf
