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@[email protected](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)
§ [email protected],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
