Designation:D7608−18´1StandardTestMethodforTorsionalRingShearTesttoMeasureDrainedFullySoftenedShearStrengthandStressDependentStrengthEnvelopeofFine-GrainedSoils1ThisstandardisissuedunderthefixeddesignationD7608;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.ε1NOTE—ThestandardwaseditoriallyupdatedinJanuary2022.1.Scope1.1Thistestmethodprovidesaprocedureforperformingatorsionalringsheartestunderadrainedconditiontomeasurethefullysoftenedshearstrengthandstressdependentstrengthenvelopeoffine-grainedsoils(usingareconstitutednormallyconsolidatedspecimen).Thefullysoftenedstrengthandthecorrespondingstressdependenteffectivestressstrengthenve-lopeareusedtoevaluatethestabilityofslopesthatdonothaveapre-existingshearsurfacebuthavebeensubjectedtoenvi-ronmentalconditionsandshearstressesthatleadtosoilsoftening,deteriorationofthesoilfabric,andstrengthloss.Ithasbeenshown(Skempton19702and19773)thatundertheseconditionsandwithinthedepthzonesthathaveundergonesoftening,first-timeslopefailurescanoccurateffectivestresslevelsthatcorrespondtoafullysoftenedstrengthenvelope.Ithasalsobeenshownempirically(Skempton19702and19773)thatfullysoftenedstrengthoffinegrainedsoilscanbeapproximatedbythepeakstrengthofareconstitutedandnormallyconsolidatedspecimen.Inthistestmethod,reconsti-tutedandnormallyconsolidatedspecimensareshearedatacontrolledandconstantdisplacementrateuntilthepeakshearresistancehasbeenobtained.Generally,thedrainedfullysoftenedfailureenvelopeisdeterminedatthreeormoreeffectivenormalstresses.Aseparatetestspecimenmustbeusedforeachnormalstresstomeasurethefullysoftenedstrengthotherwiseapost-peakorevendrainedresidualstrengthwillbemeasuredifthesamespecimenisusedatthesameoratanothereffectivenormalstressbecauseoftheexistenceofapriorshearsurface.1.2Theringshearapparatusallowsareconstitute...
