ASTM_D_7625_-_10.pdf

Designation:D762510Standard Test Method forLaboratory Determination of Abrasiveness of Rock Usingthe CERCHAR Method1This standard is issued under the fixed designation D7625;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 covers the determination of the abra-siveness of rock by the CERCHAR Abrasiveness Index(CAI)method.The test method consists of measuring the wear on thetip of steel stylus with a cone shape and known RockwellHardness,caused by scratching against a freshly broken or sawcut rock surface for a prescribed 10 mm distance using one ofthe two test apparatus.1.2 This test method is intended for freshly broken rocksurfaces;however,saw cut surfaces are covered for when asatisfactory rock surface cannot be obtained.1.3 Stylus Rockwell Hardness(HRC)can have a profoundeffect on the results and the focus of this test method is an HRCvalue of 55 for every test(1,2).2However,there are situationswhere stylus with different Rockwell Hardness can be usedTherefore,this test method includes discussions on stylus withdifferent Rockwell Hardness.1.4 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D6026.1.5 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.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 ContainedFluidsD2216 Test Methods for Laboratory Determination of Water(Moisture)Content of Soil and Rock by MassD3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD5079 Practices for Preserving and Transporting Rock CoreSamplesD6026 Practice for Using Significant Digits in GeotechnicalDataE18 Test Methods for Rockwell Hardness of Metallic Ma-terials3.Terminology3.1 DefinitionsFor definitions of terms used in this testmethod,refer to Terminology D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 abrasiveness,nthe wear or loss of material whichthe rock produces on contact with another material such asTBM cutter or drill bit.3.2.2 Rockwell Hardness Scale(HRC),na hardness scalebased on the indentation hardness of a material,which corre-lates linearly with its tensile strength.The Rockwell testdetermines the hardness by measuring the depth of penetrationof an indenter under a large load compared to the penetrationmade by a preload.The results,as a dimensionless number,arenoted by HR followed by the designation letter fromA-F basedupon used scale.For current standard,letter C is used as thescale letter for hard steel.4.Summary of Test Method4.1 A steel stylus having a 90E conical tip with its axisperpendicular,and in contact with a rock surface,under a totalconstant force of 70 N,is scratched in a direction parallel to therock surface over a distance of 10 mm.4.2 Basically,the CERCHAR test is a measurement of therelative different hardness of stylus tip and rock specimensurface.The stylus tip is made of steel having a knownRockwell Hardness.Experiments have shown that CAI variesinversely with stylus hardness.Test results with the same steel1This 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 May 15,2010.Published July 2010.DOI:10.1520/D762510.2The bold numbers in parenthesis refer to a list of references at the end of thisstandard.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 type stylus but with different hardness need to be normalized tostandard stylus hardness(3).4.3 After the test,width of the wear flatness is measured onstylus tip surface in units of 0.1 mm and number of unitsreported as the CERCHAR Abrasiveness Index,0.1mm(=1CAI).4.4 The scratch distance shall be limited to 10 mm.A CAIof 85%is achieved after the first 2 mm of the scratchs length,and 15%of the change in CAI is achieved on the last 8 mm ofthe testing length.Deviations in CAI due to variations ofscratch length shall not be significant when the variation intesting length is kept between 60.5 mm in len