ASTM_D_3967_-_08.pdf

Designation:D396708Standard Test Method forSplitting Tensile Strength of Intact Rock Core Specimens1This standard is issued under the fixed designation D3967;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.Scope*1.1 This test method covers testing apparatus,specimenpreparation,and testing procedures for determining the split-ting tensile strength of rock by diametral line compression of adisk.NOTE1The tensile strength of rock determined by tests other than thestraight pull test is designated as the“indirect”tensile strength and,specifically,the value obtained in Section 9 of this test is termed the“splitting”tensile strength.1.2 The values stated in SI units are to be regarded as thestandard.The values in parentheses are mathematical conver-sions and are provided for information only.1.3 All dimension and force measurements,and stresscalculations shall conform to the guidelines for significantdigits and rounding established in Practice D6026.1.4 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:2D653 Terminology Relating to Soil,Rock,and ContainedFluidsD3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD6026 Practice for Using Significant Digits in GeotechnicalDataE4 Practices for Force Verification of Testing MachinesE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.Terminology3.1 Refer to Terminology D653 for specific definitions.4.Significance and Use4.1 By definition the tensile strength is obtained by thedirect uniaxial tensile test.But the tensile test is difficult andexpensive for routine application.The splitting tensile testappears to offer a desirable alternative,because it is muchsimpler and inexpensive.Furthermore,engineers involved inrock mechanics design usually deal with complicated stressfields,including various combinations of compressive andtensile stress fields.Under such conditions,the tensile strengthshould be obtained with the presence of compressive stresses tobe representative of the field conditions.The splitting tensilestrength test is one of the simplest tests in which such stressfields occur.Since it is widely used in practice,a uniform testmethod is needed for data to be comparable.A uniform test isalso needed to ensure that the disk specimens break diametrallydue to tensile pulling along the loading diameter.NOTE2Notwithstanding the statements on precision and bias con-tained in this test method;the precision of this test method is dependenton the competence of the personnel performing it,and the suitability of theequipment and facilities used.Agencies that meet the criteria of PracticeD3740 are generally considered capable of competent and objectivetesting.Reliable testing depends on many factors;Practice D3740provides a means of evaluating some of these factors.5.Apparatus5.1 Loading Device,to apply and measure axial load on thespecimen,of sufficient capacity to apply the load at a rateconforming to the requirements in 8.3.It shall be verified atsuitable time intervals in accordance with Practices E4 andshall comply with the requirements prescribed therein.5.2 Bearing SurfacesThe testing machine shall beequipped with two steel bearing blocks having a Rockwellhardness of not less than 58 HRC(see Note 3).NOTE3False platens,with bearing faces conforming to the require-ments of this standard,may be used.These shall be oil hardened to morethan 58 HRC,and surface ground.With abrasive rocks these platens tendto roughen after a number of specimens have been tested,and hence needto be surfaced from time to time.5.2.1 Flat Bearing BlocksDuring testing the specimen canbe placed in direct contact with the machine bearing plates(orfalse platens,if used)(see Fig.1).The bearing faces shall notdepart from a plane by more than 0.0125 mm when the platens1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.Current edition approved July 1,2008.Published July 2008.Originally approvedin 1981.Last previous edition approved in 2005 as D3967 05.DOI:10.1520/D3967-08.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandardsvolume information,refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this