第十二届国际岩石力学大会主题论文3

Fifty years of the ISRM and associated progress in rock mechanics E.T. Brown

HarmonisingRockEngineeringandtheEnvironment–Qian&Zhou(eds)

©2012Taylor&FrancisGroup,London,ISBN978-0-415-80444-8

Multi-parameterresponsesofsoftrocksduringdeformationandfracturingandtheir

implicationsingeomechanicsandgeoengineering

Ö.Aydan

DepartmentofMarineCivilEngineering,TokaiUniversity,Shizuoka,Japan

Y.Ohta

JapanNuclearEnergySafetyOrganization,Tokyo,Japan

H.Tano

DepartmentofCivilEngineering,NihonUniversity,Koriyama,Japan

ABSTRACT:Themulti-parametermeasurementsysteminvolveselectricpotential(EP)variations,electricalresistivity,acousticemissions(AE),rocktemperature(RT),accelerationinadditiontotheconventionaldisplacement(strain)andload(stress)measurements.Thisstudyisconcernedwiththemulti-parameterresponseofsoftrocksduringdeformationandfractur-ingprocess.Someofexperimentswerecarriedoutunderpurelymechanicalmanualloadingwithoutusingtheloadingdevice,whichmayutilizeACcurrentaspowersource.Therefore,theloadingsystemisfreeofelectricnoise,whichmaybecausedbytheloadingsystem.Theauthorspresenttheoutcomesoftheseexperimentsanddiscussoftheimplicationsofmulti-parameterresponseingeomechanicsandgeoengineering.Subject:Keywords:

Rockmaterialandrockmasspropertytesting

rockfailure,labtesting,dynamics,monitoring,rockstress,rockbursts

Theloadingsystemismanuallyoperatedandithasthecapac-ityof10tonf.Astheloadingismanuallyperformed,theelectricalnoisecausedbytheloadingsysteminpreviousexperimentsisabsent.

Theappliedloadandinduceddisplacementwereauto-maticallymeasuredandstoredontheharddiskofalaptopcomputerthroughanelectroniclogger.Electricpotentialsinducedduringthedeformationofsamplesweremeasuredthroughtwoelectrodesattachedtothetopandbottomofsam-plesusingavoltmeterandloggerunit(AGILENTA8670A)anddataweresimultaneouslystoredontheharddiskofthelaptopcomputer.Theelectrodeswereisolatedfromloadingframewiththeuseofisolators.Electricpotentialsweremea-suredeitherasDCand/orAC.Twoaccelerometerswereusedtomeasuretheaccelerationresponsesduringfracturing.Figure1showsanexplodedviewofatypicalexperimentalset-upforsamples.Inadditiontotheabovemeasurementsys-tem,acousticemissions(AE)deviceswereusedtomeasuretheacousticemissionsduringfracturingandslidingofsamples.

1INTRODUCTION

Whenrockstartstofail,thestoredmechanicalenergyinrocktendstotransformitselfintodifferentformsofenergy.ExperimentalstudiesbyAydanandhisgroup(Aydanetal.2001,2003)showedthatrockindicatesdistinctvariationsofvariousmeasurableparameterssuchaselectricpoten-tial,magneticfieldacousticemission,resistivityetc.besidesloadanddisplacement,whicharecalledmulti-parameters,duringdeformationandfracturingprocesses.Furthermore,somein-situmonitoringschemesweredevelopedforstruc-turalsafetyoftunnelsaswellasforearthquakepredictionstudies(Aydanetal.2005).Thesevariationsmaybeusefulinpredictingthefailuresofrockstructuresingeoengineeringwellasearthquakesingeoscience.

Theauthorsundertookanexperimentalstudytomakefur-thercontributionstotheunderstandingofmulti-parametervariationsincludingelectricpotentialandelectricalresistiv-ityduringdeformationandfracturingprocessofgeomaterialswhichrangesfromcrystals,gouge-likematerialstorocksunderdifferentloadingregimes(Aydanetal.2001,2003).Inthisarticle,theauthorsdescribetheoutcomesoftheexperimentalstudiesonmulti-parametervariationsduringthedeformationandfracturingofgeomaterials.Theloadingframeisfreeofelectricalnoisesothattheeffectofelec-tricfieldoftheloadingsystemisentirelyeliminatedfromsamples.Onthebasisoftheoutcomes,theauthorsdiscusstheirpossibleimplicationsingeo-mechanics,geo-scienceandgeo-engineering.

2EXPERIMENTALSET-UP

TestswereperformedusinganuniaxialcompressiontestingmachinesatRockMechanicslaboratoryofTokaiUniversity.

3EXPERIMENTSONROCKSAMPLES

SoftrockswereOyatuff,Yuisandstone,AsuyamatufffromJapan,tuffsofAvanos,Zelve,DerinkuyuofCappadociaregionofTurkeyandsoapstone(steatiteortalc-schist).Soapstoneparticularlycontainsnopiezo-electricsubstance.

Sampleswereloadedbyincreasingtheloadinsteps.Insometests,short-termconstantloadingwasimposedinordertoobserveelectricpotentialresponseduringloadincreaseandcreeploading.Figures2to7showtheexperimentalresultsonthemulti-parameterresponsesofrocksmentionedabove.Asseenfromtheexperimentalresults,thedeformationandfracturingofrockcausethedistinctvariationsofelectric

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