ASTM_D_7702_-_D_7702M_-_14.pdf

Designation:D7702/D7702M14Standard Guide forConsiderations When Evaluating Direct Shear ResultsInvolving Geosynthetics1This standard is issued under the fixed designation D7702/D7702M;the number immediately following the designation indicates theyear of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of lastreapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This guide presents a summary of available informationrelated to the evaluation of direct shear test results involvinggeosynthetic materials.1.2 This guide is intended to assist designers and users ofgeosynthetics.This guide is not intended to replace educationor experience and should only be used in conjunction withprofessional judgment.This guide is not intended to representor replace the standard of care by which the adequacy of agiven professional service must be judged,nor should thisdocument be applied without consideration of a projects manyunique aspects.Not all aspects of this practice may beapplicable in all circumstances.The word“Standard”in thetitle of this document means only that the document has beenapproved through the ASTM consensus process.1.3 This guide is applicable to soil-geosynthetic andgeosynthetic-geosynthetic direct shear test results,obtainedusing either Test Method D5321/D5321M or D6243/D6243M.1.4 This guide does not address selection of peak orlarge-displacement shear strength values for design.Refer-ences on this topic include Thiel(1)2,Gilbert(2),Koerner andBowman(3),and Stark and Choi(4).1.5 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard.The values stated ineach system may not be exact equivalents;therefore,eachsystem shall be used independently of the other.Combiningvalues from the two systems may result in non-conformancewith the standard.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 establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:3D653 Terminology Relating to Soil,Rock,and ContainedFluidsD5321/D5321M Test Method for Determining the ShearStrengthofSoil-GeosyntheticandGeosynthetic-Geosynthetic Interfaces by Direct ShearD6243/D6243M Test Method for Determining the Internaland Interface Shear Strength of Geosynthetic Clay Linerby the Direct Shear MethodD4439 Terminology for Geosynthetics3.Terminology3.1 DefinitionsFor definitions of terms relating to soil androck,refer to Terminology D653.For definitions of termsrelating to geosynthetics and GCLs,refer to TerminologyD4439.3.2 Definitions of Terms Specific to This Standard:3.2.1 adhesion,caor c,nthe y-intercept of the Mohr-Coulomb shear strength envelope;the component of shearstrength indicated by the term ca,in Coulombs equation,=ca+tan.3.2.2 failure envelope,ncurvi-linear line on the shearstress-normal stress plot representing the combination of shearand normal stresses that define a selected shear failure criterion(for example,peak and post-peak).Also referred to as shearstrength envelope.3.2.3 Mohr-Coulomb friction angle,nangle of frictionof a material or between two materials(degrees),the angledefined by the least-squares,“best-fit”straight line through adefined section of the shear strength-normal stress failureenvelope;the component of the shear strength indicated by theterm,in Coulombs equation,=c+tan.3.2.4 Mohr-Coulomb shear strength envelope,nthe least-squares,“best-fit”straight line through a defined section of theshear strength-normal stress failure envelope described the1This guide is under the jurisdiction ofASTM Committee D35 on Geosyntheticsand is the direct responsibility of Subcommittee D35.04 on Geosynthetic ClayLiners.Current edition approved May 1,2014.Published June 2014.Originallyapproved in 2011.Last previous edition approved in 2013 as D7702_D770213a.DOI:10.1520/D7702_D7702M14.2The boldface numbers in parentheses refer to a list of references at the end ofthis standard.3For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 equation =ca+tan.The envelope can be described forany chosen shear failure criteria(for example,peak,post-peak,or residual).3.2.5 secant friction angle,sec,n(degrees)the angledefined by a line drawn from the origin to a data point on theshear strength-normal stress failure envelope.Intended to beused only at the shearing normal stress for which it is defined.3.2.6 shear strength,nthe shear force on a given failureplane.In the direct shear test it i