analyses of de-confinement mechanisms of unstable failures ... · fric@on angle and dilaon angle...

AnalysesofDe-confinementMechanismsofUnstableFailuresinUndergroundMiningCondi<ons

RuixiangGuandUgurOzbayColoradoSchoolofMines

Preparedforthe33rdInterna@onalConferenceonGroundControlinMining

July29-31,2014,Morgantown,WV

PresentedbyRyanGarvey

•  Unstablefailure•  S@ffnesscriteria•  Jointandblockcons@tu@vemodels

§  Con@nuouslyYielding(CY)jointmodel

§  Mohr-CoulombstrainsoTening(MCSS)model

•  De-confinementmechanismsandsimula@onresults§  Unstableshearfailureatinterface§  Weakregionsalonginterface

•  Conclusions

Contents

UnstableFailures–RockBurstsandCoalBumps

Stablefailure Unstablefailure

Stablefailures(b)andunstablefailure(c)inshearalongdiscon@nuity(Rice,1983)

Unstableandstablefailuresincompression,modifiedfromCook(1965)

S<ffnessCriteria

§  Cook,N.G.W.1965.Anoteonrockburstsconsideredasaproblemofstability.JournaloftheSouthAfricanIns3tuteofMiningandMetallurgy65:437-446.

§  Rice,J.R.1983.Cons@tu@verela@onsforfaultslipandearthquakeinstabili@es.Pageoph121(3):443-475.

DynamicEjec@on

SeismicEnergy

JointandBlockModel

•  Mohr-CoulombstrainsoTening(MCSS)model

Anexamplestress-straincurveofsoTeningmodel. Aconceptualrepresenta@onofvaria@onsofcohesion,fric@onangleanddila@onangleintheMCSSmodel.

•  Con@nuouslyYielding(CY)jointmodel

JointandBlockModel

Thetypicalshearstress-sheardisplacementcurveoftheCYjointmodel(ItascaConsul@ngGroup,2010)

Shearstress-sheardisplacementcurveoftheCYjointmodelunderincreasednormalloading(GuandOzbay,2014)

§  ItascaConsul@ngGroup.2010.UDECmanual,version4.0.Minneapolis,MN,USA.§  Gu,RandOzbay,U.2014.Dis@nctelementanalysisofunstableshearfailureofrockdiscon@nui@esinundergroundminingcondi@ons.

Interna3onalJournalofRockMechanicsandMiningSciences,68:44-54.

De-confinementMechanism

Mininggeometryusedformodelingde-confinementinducedunstablecompressivefailuresinsidewalls(miningadvancesperpendiculartotheplanecausingshearstressincreasesattheinterfacesclosetothesidewalls).

NumericalModelandResults

Modelforthestudiesofde-confinementresultedfromunstableshearfailuresattheinterfaces.

NumericalModelandResults

Shearstress-@mecurveoftheinterfacemeasurementpoints

Ver@calstress-@mecurveofthecoalmeasurementregions

MCinterface(stable)

CYinterface(unstable)

De-confinementMechanismandModel

Modelforthestudiesofde-confinementresultedfromtheexistenceofweakregionsattheinterfaces.

NumericalModelResults

Ver@calstress-@mecurvesofthemeasurementregionsinthesimula@on.

•  Unstablefailuressignifiedbysuddenlossesofloadwhilestablefailuresfollowarela@velysmoothandgradualreduc@oninload.

•  Suddenslipalonginterfaceledtorapidde-confinementandstrengthreduc@onofcoal->coalbumpcondi@ons

•  Weakpor@onsinrock-coalinterfacecouldleadtogreatervolumesofaffectedcoalandlargermagnitudecompressivefailures

Conclusions