ASTM_D_4623_-_08.pdf

Designation:D462308Standard Test Method forDetermination of In Situ Stress in Rock Mass by OvercoringMethodUSBM Borehole Deformation Gauge1This standard is issued under the fixed designation D4623;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 the determination of the ambi-ent local stresses in a rock mass and the equipment required toperform in situ stress tests using a three-component boreholedeformation gauge(BDG).The test procedure and method ofdata reduction are described,including the theoretical basis andassumptions involved in the calculations.A section is includedon troubleshooting equipment malfunctions.NOTE1The gauge used in this test method is commonly referred to asa USBM gauge(U.S.Bureau of Mines three-component borehole defor-mation gauge).21.2 The values stated in inch-pound units are to be regardedas standard.No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety problems,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 ContainedFluidsD3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD4394 Test Method for Determining In Situ Modulus ofDeformation of Rock Mass Using Rigid Plate LoadingMethodD4395 Test Method for Determining In Situ Modulus ofDeformation of Rock Mass Using Flexible Plate LoadingMethodD6026 Practice for Using Significant Digits in GeotechnicalDataD7012 Test Methods for Compressive Strength and ElasticModuli of Intact Rock Core Specimens under VaryingStates of Stress and Temperatures3.Terminology3.1 DefinitionsSee Terminology D653 for general defini-tions.3.2 Definitions:3.2.1 deformationdisplacement change in dimension ofthe borehole due to changes in stress.3.2.2 in situ stressthe stress levels and orientations exist-ing in the rock mass before excavation.4.Summary of Test Method4.1 The overcore test measures the diametral deformation ofa small-diameter borehole as it is removed from the surround-ing stress field by coaxially coring a larger diameter hole.Deformation is measured across three diameters of the smallhole,spaced 60 apart,using a deformation gauge developedby the U.S.Bureau of Mines.With knowledge of the rockdeformation moduli,the measured borehole deformation canbe related to the change in stress in a plane perpendicular to theborehole.This change in stress is assumed to be numericallyequal,although opposite in sense to the stresses existing in theparent rock mass.Deformation measurements from threenonparallel boreholes,together with rock deformation moduli,allow calculation of an estimate of the complete three-dimensional state of stress in the rock mass.5.Significance and Use5.1 Either virgin stresses or the stresses as influenced by anexcavation may be determined.This test method is writtenassuming testing will be done from an underground opening;however,the same principles may be applied to testing in arock outcrop at the surface.5.2 This test method is generally performed at depths within50 ft(15 m)of the working face because of drilling difficulties1This 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 1986.Last previous edition approved in 2005 as D4623 05.DOI:10.1520/D4623-08.2Considerable information presented in this test method was taken from Bureauof Mines Information Circular No.8618,and Hooker,V.E.,and Bickel,D.L.,“Overcoring Equipment and Techniques Used in Rock Stress Determination,”Denver Mining Research Center,Denver,CO,1974.3For 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.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 at greater depths.Some deeper testing has been done,butshould be considered developmental.It is also useful forobtaining stress characteristics of existing concrete and rockstructures for safety and modification investigations.5.3 This test method is difficult in rock with fracturespacings of less than 5 in.(130 mm).A large number of testsmay be required in order to