CAVERISKCONTENTSTypesofriskMajoroperationalrisksBlackhatactionstrategiesTypesofriskHeslop2000DesignrisksOperationalhazardsDrawrisksTechnologyrisksDesignrisksEconomiceffectBasedonincorrectgeotechnicaldataAbovecollectedyearsbeforePoorassessmentofgroundconditionsCommonexample-partiallyloggedcore(egUCS&RQD)-Forcedtousebecauseoflackoffunds-Resultsotherparametershavetobeguessed-uncertaintyindesignparameters-Undersupportofdriftsby25%CommongeotechnicalfailuresNostudydoneStudymissingLackofdetailforstudylevelDetaildefaultScopingstudydetailacceptedforDEFSClassificationdesignusedonlyNotaddressingthekeyissuesmentionedatearlierstagesConceptualstagenotcorrectNotunderstandingimplicationsofrecommendationsNotunderstandingdesignphilosophyNotreadingstudyreports-80%donotreadreport-15%executivesummary-5%reportPracticalmeasuresFocussstudy/reasonablenesstest-Reviewandcompileotherstudies-Readextensively(take1week)-Literaturestudy-Benchmark-developfeelfortheproject-FindingsFindout(Summers2000):-Whatweknow-Whatwedon’tknow-Whatweknowwedon’tknowStudystandards(AusIMM)UnresolvedissuesUnresolvedissuesAspectsthatcannotberesolvedduringthestudySpecialbridgingstudies(i.e.caving)Ruleforspecialstudies-Impactonprojectgreaterthancontingency-Infrastructurestability-Cavability-dilutionanddilutionblanketsIfnocashortimeforspecialstudy-Runprojectonbluesky-Sensitivityonworstcase-opinionrequiredOperationalrisksHeslop2000LossoflifeClosemineorsectionofthemineRockburstsAirblastsMudrushes/floodsRock/strainburstingStressincreasesasundercutisdeveloped.Stressesincreasesfurtherbeforepropagation.PerimeterstressesincreasewithareaundercutandheightofundercutRock/strainburstdamagegreatestbeforepropagationRockburstingrelatedtocavingRockburstingrelatedtomanagementofcavingprocessRockburstcavepronecaves>300-400mHightectonicstressesMountainsMRMR>35DifficultyinpropagatedthecaveRapidratesofadvancesofpre-break/UCEl-Tiente1976RockburstingFracturedzoneexistsaroundthecave50mfromthecavefaceAsthecaveprogatesthiszoneincreasesFracturezoneincreaseduetostressrelaxationDuringthisstagesareasupto500mfromcaveeffectedStrainburstscanoccurinplaceslikecrusher,plats,cribbroomsStrainbursting,ejectionRockburstingBurstsoccurwithcavepropagationHighlevelsofseismisitybeforepropagation.MagofuptoRichter3.6Largecaveshaveupto6largeburstsifnotmanagedSeismiceventsduringpropagationareshearrelatedCommonareasforbursting20to40mfromcaveface/frontStrainburstingandrockejectionatbreakaways/intersectionsupto500mfromcave100mbelowthecaveLargeexcavationswith50mfromorebodyPillarsbetweenconferencingcavefrontsBeforepropagation.RockburstpreventionstrategiesMeshwalls/backsofintersections/largeexcavations500mfromcaveConeboltintersections/breakawaysInstallyieldingsupportwithin40mfrompropagationfacepositionReduceblockcavedrawrates<2000/tons/daybeforepropagationReduceblockcave/SLCpre-breakadvanceratesbelow3000m2/month.Propagatethecavefirst.SLC<45mvertical/m/yrMinetowardsthesolidMajorairblasts4conditionsAgapbetweenthemuckpileandcavebackCavinghasslowedorstoppedAlargevolumeofcavebackmustbeunstableAirescaperoutesGeotechnicalHardintrusivethroughtheorebodyHardorezonesaboveuclevelNeckingortaperingoforebodyNopitsubsidenceHistoryofcontactorewedgeformationHistoryofstallHardcavesMuckpileCavegapNorealhardrulesExperientialCriticizedOldminingrule200mm/daydrawrateRealisticcavebackgapsarebetween2mto15m2mto5mgoodfornormalproduction15-30mdrawrategreatercavingrate30m>problemofdrawcorrection/airblasts30m-50mofmuckpileAllabovewrongiftunnelsintocaveCavestallCavingstopsorslowsVerticalMRMR>thanUCHRCavinghoopstressesstrengthrockmassBlockheight2xfootprintwidthDrawrategreaterthancavingrateHardcaves<44mm/daySoftcaves<75mm/dayType1collapse(Bell1999)MUCKPILEAIRGAPSurfaceBackFailsType2collapse(Bell1999)MUCKPILEAIRGAPSurfaceBlockfallsfrombackType3(Flores1993)wedgeSTRUCTUREAirsources&escaperoutes2mainairsourcesroutes-airinmuck/cavebackgap-airinmuckpilevoidsAirescaperoutes-Viaundercutdrawpoints-Muckpiletodrawpoints-OldworkingsholedincaveeffectsLossoflifeSuddensubsidenceCollapseofblockcontactareaPointloadingondriftsHang-upsDestructionanddamagetoservicesLossofproductionDriftrehabPreventionDefinerockmasscondition100mverticalintervalsHRdesignedhardgeotechnicalunitMajorwedgestructureassessmentCorrectdefinitionofdrawrateKeepdrawpointsfullGooddrawcontrolCSMcaveifpossible/3ddrawprofilesPlugalltunnelsintocaveSiteplugsoutsidebreakbackzoneTele-remotedrawpointsDrawpointsfullMonitorcavebackEvacuatemineinfailure/dangertimesMUDRUSHESButcher(1999-2000)Effects-Lossoflife-Lossofmine-Productionloss-Airblasts-majorrehabMudrushconditionWaterMudmaterialsDischargepointDisturbanceMudformingmaterialsCavewasteswithshaleTailing/slimesormuddepositedingloryholeWeatheredoverburden/soilSuspectedTKBKimberlitematerialGypsum/claymineralsFinecavewaste20%sandsizematerialMoisture>8.5%MUDMudformingmechanicsShale/mudformingmaterialdrawnintocave.AbovematerialisgrounddownmuckpileactionGroundmaterialliesinmuckpilevoidsWatermixeswithmaterialtoformmudMudisdrawnoutorflowsoutMudcanbeforcedoutbycollapsingmuckpilevoidsDischargepointsTYPE1DRAWPOINTSMudtransportexcavationsMTE’sMudtransportexcavationsMufairia-morepeoplekilledfromMTEcut-offsCut-offonlowerlevelsandbehindMTE’s-Orepasses-RAP’’s-Declines-AccessesFactsTailingsinrushesgreaterdangerWidedrawpointsgreaterdischargeSLCpoorcontrol2miningblockslostwithSLCPoormuckpiledrainagegreaterdangerAirblastsoccuraftermudrushesFloodingoccursDestructionofservicesMudrushprevention3D’SPRINCIPALDistance-keepmudformingmaterialsoutofmuckpileDrain-keepmuckpilesdryDraw––gooddrawcontrolstandardsMeaningGooddrawcontrol-Uniformdrawdown-drawdisciplineDrainage-Minepumping-Surfacepumping-keepundergroundworkingsdry-Preventinflowsinmuckpilefromundergroundandsurface-Hydro-geologicalstudyDistance-bottom-upcavingmethods(reduceSLC’s)-Sitetailing/slimesdamsawayfromgloryhole-Donotdisposeofminingwasteingloryhole-removemudformingmaterialifpossible-correctopenpitslopedesignMeaningUsesmalldrawpointsize(3.8mx3.8m)SealoldpassesandworkingsInstallmorepumpsInstallwaterpreventionstallsMudrushalarmsMonitoringpumpinglevelsLowerinpumpingmeanswaterinmuckpileTele-remotesClosedboggercabswithoxygenRe-inforcedboggerca