ASTM_D_8296_-_19.pdf

Designation:D829619Standard Test Method forConsolidated Undrained Cyclic Direct Simple Shear Testunder Constant Volume with Load Control or DisplacementControl1This standard is issued under the fixed designation D8296;the number immediately following the designation indicates the year oforiginal adoption 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 defines equipment specifications andtesting procedures for the measurement of cyclic strength,number of cycles to liquefaction or cyclic properties(Modulusand Damping)of soils,after one-dimensional consolidationusing a cyclic mode of loading.1.2 The cyclic shearing can be applied using load control ordisplacement control.It shall be the responsibility of theagency requesting this test to specify the magnitude andfrequency of the cyclic loading.Other loading histories may beused if required by the agency requesting the testing.1.3 This test method is written specifically for devices thattest cylindrical specimens enclosed in a wire-reinforced mem-brane or a soft membrane within a stack of rigid rings(this testmethod applies to Teflon coated rigid rings as well).Othertypes of shear devices are beyond the scope of this test method.1.4 This test method can be used for testing cohesionlessfree draining soils or fine grained soils.However,this testmethod may be followed when testing most soil types if care istaken to ensure that any special considerations required forsuch soils are accounted for.1.5 The shearing phase of this test is conducted underconstant volume conditions.Since the lateral confinementsystem prevents radial specimen strains,the constant volumecondition is accomplished by preventing specimen heightchange during shear.Shearing under constant volume can beperformed on dry or saturated specimens.The constant volumecondition is equivalent to the undrained condition for fullysaturated specimens.Cyclic direct simple shear testing withtruly undrained conditions(restricting pore water flow fromand into the specimen)can be performed using some simpleshear devices,but is beyond the scope of this standard.21.6 The cyclic strength of a soil is determined based on thenumber of cycles required to reach a limiting double amplitudeshear strain or a single amplitude shear strain,while liquefac-tion is more commonly defined as 100%change in verticalstress ratio(change in effective vertical stress during shearingdivided by effective vertical stress at end of primary consoli-dation).The change in vertical stress ratio in constant volumeshearing is equivalent to the excess pore pressure ratio(excesspore pressure during shearing divided by effective verticalstress at end of primary consolidation)under undrained con-ditions.The strain criterion is only applicable when performingload controlled tests;100%change in vertical stress ratio canbe used for both,load and displacement control.For displace-ment control testing,the criterion to stop the test could be aspecified number of cycles.1.7 This test method is applicable to testing intact,reconstituted,or compacted specimens;however,it does notinclude specific guidance for preparing,reconstituting or com-pacting test specimens.1.8 It shall be the responsibility of the agency requestingthis test to specify the magnitude of the consolidation stressprior to shear and,if assigned,an unloading consolidation stagemay be required for over-consolidating the specimen.1.9 All recorded and calculated values shall conform to theguide for significant digits and rounding established in PracticeD6026.1.9.1 The procedures used to specify how data are collected/recorded and calculated in this test method are regarded as theindustry standard.In addition,they are representative of thesignificant digits that shall generally be retained.The proce-dures used do not consider material variation,purpose forobtaining the data,special purpose studies,or any consider-ations for the users objectives;it is common practice toincrease or reduce significant digits of reported data to be1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.09 on Cyclic andDynamic Properties of Soils.Current edition approved Nov.1,2019.Published November 2019.DOI:10.1520/D8296-192Tests sheared under truly undrained conditions should be performed exclusivelyon saturated specimens.Therefore,backpressure saturation is required to ensurecomplete saturation of test specimen.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by t