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1、Analyticalmodelsforrockbolts.C.L*,StillborgAbstractThreeanalyticalmodelshavebeendevelopedforrockbolts:oneforboltssubjectedtoconcentratedpullloadinpullouttests,oneforboltsinstalledinuniformlydeformedrockmasses,andoneforboltssubjectedtotheopeningofindividualrockjoints.Thedevelopmentofthemod
2、elshasbeenbasedonthedescriptionofthemechanicalcouplingattheinterfacebetweentheboltandthegroutmediumforgroutedbolts,orbetweentheboltandtherockforfrictionallycoupledbolts.Forrockboltsinthepullouttests,theshearstressoftheinterfacesexponentiallywithincreasingdistancefromthepointofloadingwhent
3、hedeformationiscompatibleacrosstheinterface.Decouplingmaystartfirstattheloadingpointwhentheappliedloadislargeenoughandthenpropagatetowardsthefarendoftheboltwithafurtherincreaseintheappliedload.Themagnitudeoftheshearstressonthedecoupledboltsectiondependsonthecouplingmechanismattheinterface
4、.Forfullygroutedbolts,theshearstressonthedecoupledsectionislowerthanthepeakshearstrengthoftheinterfacewhileforfullyfrictionallycoupledboltsifisapproximatelythesameasthepeakshearstrength.Forrockboltsinstalledinuniformlydeformedrock,theloadingprocessoftheboltsduetorockdeformationhasbeentake
5、nintoaccountindevelopingthemodel.Modelsimulationsconfirmthepreviousfindingsthataboltinsituhasapick-uplength,ananchorlengthandneutralpoint.Itisalsorevealedthatthefaceplateplaysasignificantroleinenhancingthereinforcementeffect.Injointedrockmasses,severalaxialstresspeaksmayoccuralongtheboltb
6、ecauseoftheopeningofrockjointsintersectingthebolt.1.IntroductionRockboltshavebeenwidelyusedforrockreinforcementincivilandminingengineeringforalongtime.Boltsreinforcerockmassesthroughrestrainingthedeformationwithintherockmasses.Inordertoimproveboltingdesign,itisnecessary:tohaveagoodunderst
7、andingofthebehaviourofrockboltsindeformedrockmasses.Thiscanbeacquiredthroughfieldmonitoring,laboratorytests,numericalmodelingandanalyticalstudies.Sincethe1970s,numerousresearchershavecarriedoutfieldmonitoringworkonrockboltsinstalledinvariousrockformations.Freemanper