煤矿软岩巷道支护强度优化外文文献翻译中英文翻译.docx
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煤矿软岩巷道支护强度优化外文文献翻译中英文翻译
英文原文
Theoptimalsupportintensityforcoalmineroadwaytunnelsinsoftrocks
C.Wang*
MiningEngineeringProgram,WesternAustralianSchoolofMines,PMB22,KalgoorlieWA6430,Australia
1.Introduction
Theessenceofundergroundroadwaysupportistoprovidethesurroundingrocksofanundergroundroadwaywithassistancetohelpthemachievestressandstrainequilibriumandultimatelystabilityofdeformation.Theapproachestothisgoalareeithertoreinforcetherockmassbyrockboltingorinjection(internalrockstabilization)ortoprovidethesurroundingrockswithasupportresistancewithamagnitudebeingdescribedasthesupportintensity(externalrockstabilization).
Whenanundergroundroadwayislocatedinsoftrockswhicharetoosofttobereinforcedbyboltingand/orunsuitableforrockinjectionbecauseofrestraintsimposedbyeithertherockmassimpermeabilityorrockmassdeteriorationwhenwaterisencountered,externalrocksupport,suchassteelsets,thereforebecomestheonlyoptionforthestabilitycontroloftheroadway.Underthiscircumstance,thesupportintensitymeansasupportforceactingperunitsurfaceareaofthesurroundingrocksoftheroadway.Insoftrockengineeringpractice,thedesignofasupportpatternforaroadwayinundergroundcoalminingisnormallybasedonrulesofthumb.Inmostcases,heavysupportmeasuresareadoptedtosecureasuccessfulroadway.
Fig.1(a)demonstratestheexcellentconditionofasub-levelroadwaywithinsoftrocksatanundergroundcoalmineinnorthChina,whereanexcessivecapitalcostwasappliedfortheachievementofroadwaystability.Insomecases,suchasaserviceroadwaydriveninsoftrocksatthesamemine(Fig.1(b)),insufficientsupportintensitywasspecifiedasaresultofalackofrelevantexperienceanddesigncodes.Consequently,failureoftheroadwaystabilitywasinevitableandanextracostwasincurredwhenthesubsequentroadwayrepairorrehabilitationwasundertaken.
Thecriticalissueinbothcasesliesinthedeterminationofanoptimalsupportintensitywhichisthefunctionofthegeometryanddimensionofaroadwayanditsgeotechnicalconditionsincludingrockmassproperties,stressconditionsandhydrologicalstatus.
Physicalmodellingusingsimulatedmaterialsbasedonthetheoryofsimilarityprovidesadirectperceptionalmethodologyformininggeomechanicsstudy[1-6].Usingsimulatedmaterialsofthesamecompositiontoconstructaroadwayanditssoftsurroundingrocks,applyingacertainmagnitudeofsimulatedsupportintensitytothesurfaceofaroadwayundersimulatedstressconditions,thethree-dimensionalphysicalmodellingmethoddepictedinthisNoteemonstratesaquantitativesolutionforstrategicdesignofroadwaysupportconcernedwithsoftrocks.Arelationbetweenthesupportintensityanddeformationofthesurroundingrocksofaroadwayhasbeenestablishedafteraseriesofsimulationtestshadbeenconducted.Adiscussionontheoptimalsupportintensityforaroadwayinsoftrocksisalsogiven.
Fig.1.Examplesofsuccessfulandunsuccessfulsupportofundergroundroadwayswithinsoftrocks:
(a)Goodconditionofasublevelroadway,(b)Unsuccessfulsupportofaserviceroadway.
2.Featuresofthethree-dimensionalphysicalmodelling
Aphysicalmodellingstudyoftheinteractionbetweensupportintensityandroadwaydeformationwascarriedoutusingthethreedimensionphysicalmodellingsystem(seeFig.2)attheCentralLaboratoryofRockMechanicsandGroundControl,ChinaUniversityofMiningandTechnology.Featuresofthissystemaredescribedinthefollowingsub-sections.
Fig.2.Three-dimensionalloadedphysicalmodellingsystemattheCentralLaboratoryofRockMechanicsandGroundControl,ChinaUniversityofMiningandTechnology.
2.1.Sizeofthephysicalmodel
Theeffectivesizeofaphysicalmodelis1000mmwide,1000mmhighand200mmthick.
2.2.Threedimensionalactiveloadingcapability
Sixflatjacksareusedtoapplyloadstothesixsidesofthephysicalmodelintheformofarectangularprism.Eachflatjackwasdesignedtocoverthefullareaofoneofthesixsidesandbecapableofapplyingapressureofupto10MPaontothesurfaceofthesimulatedrockmass.Thismeansthattheflatjacksarecapableofapplyinganactiveloadofupto1000tonnesand200tonnessimultaneouslyonthefrontandbackfacets,thetopandbottom,andthetwosidefacetsofamodel,respectively.
2.3.Long-termcontinuousloadingcapability
Ahigh-pressure,nitrogen-operated,hydraulicpressurestabilisingunitwasemployedtomaintainaconsistentmagnitudeofloadappliedtothemodelsothatthephysicalmodellingtestisabletolastcontinuouslyforweeks,monthsorevenyearswithoutinterruption.Thisfeatureensuresthatthestudyofthelong-termrheologicalbehaviourofsoftrockscanbecarriedout.
3.Physicalmodellingtests
Physicalmodellingofanundergroundroadway/tunnelwithinsoftrockswithahydrostaticstressconditionwascarriedout.Thesamesimulatedmaterialswererepeatedlyusedsixtimestoconstructsixphysicalmodels.Eachroadwaymodelwasprovidedwithadifferentmagnitudeofsupportintensity.
3.1.Geotechnicalconditionsfortheprototypeandthemodellingscale
Aspecifiedundergroundroadwaywithinsoftrockswasassumedtobetheprototypeforthemodellingstudy.Detailedgeotechnicalconditionsoftheroadwayanditssurroundingrocksare:
circularroadwaywithadiameter(D)of4.5mandcross-sectionalareaof16m2;
UCS(Rc)ofthesurroundingrockwas20MPa;
bulkdensityofthesurroundingrockwas2500kg/m3;
depthoftheroadwaylocationwas500mbelowsurface;
rockmassstress(s0)was12.5MPainalldirections;
supportintensity(pa)tobeappliedtotheroadwaywas0.1,0.2,0.3,0.4,0.5and0.6MPa,respectively.
Thegeotechnicalmodellingscale(Cl)determinedwas1:
25.Thebulkdensity(gm)ofthesimulatedrockmassmaterialswas1600kg/m3.Therefore,alltherelatedsimulationconstantsare:
similarityconstantforbulkdensity:
Cg¼1600/2500=0.64;
similarityconstantforstrength:
Cs¼ClCg¼0:
256;
similarityconstantforload:
CF¼CgC1¼4:
09610ÿ5;
similarityconstantfortime:
Ct¼Cl:
5¼0:
2:
Geotechnicalconditionsofthesimulatedrockmass
androadwaywerederivedfromthoseoftheprototyperockmassaspresentedbelow:
strengthofthesimulatedrockmass:
Rm=RcCs=0.512;
diameterofthesimulatedroadway:
Dm=DCl=180mm;
loadintensityonthefacetsofthemodel:
pm=s0Cs=0.32MPa;
Simulatedsupportintensity:
pam=paCs=0.00256,0.00516,0.00768,0.01024,0.0128and0.01536MPa;respectively.
3.2.Realizationofsupportintensityinphysicalmodelling
Duetotherestraintsofthesmalldimensionsofthemodelroadwayonthesimulationofsupportstructure,thesupportpatternandstructurewereunabletobesimulated.Instead,anequivalentsupportintensitywassimulatedandappliedtothesurfaceofthesurrounding
rockofthemodelroadway.AStaticWaterSupportandDeformationMeasurementSystem(SWSDMS)wasdesignedspecially.Fig.3illustratestheSWSDMSbeinginstalledinthemodelroadway.ThemechanismofSWSDMSistouse4separatewatercapsulestoapplyasupportintensitytothesurfaceoftheroadwayroof,twosidewallsandfloor.Fourrubbertubes,eachofwhichwaslinkedtoawatercapsuleandfilledwithwater,wereusedtogenerateawaterpressureatthecapsule/rockinterfaceandmeasureitthroughthewaterlevelreading.
Acertainconstantsimulatedsupportintensitywasachievedbyapplyingacertainheightofstaticwaterpressure.Achangetosupportintensitycouldbemadebychangingthewaterheightintherubbertube.Thevolumechangeofeachofthefourwatercapsuleswasmeasuredattheduetimebycollecting
andweighingthewateroverflow.Thevolumeofwatercomingfromeachofthefourwatercapsuleswasusedtocalculatetheradialdeformationofroadwaysurroundingrock,i.e.,roofsubsidence,wall-to-wallclosureandfloorheave.Theproposedsimulatedsupportintensities,i.e.,Pam¼0:
00256,0.00516,0.00768,0.01024,0.0128and0.01536MPa,wereachievedbyadjustingthestaticwaterlevelto256,516,768,1024,1280and1536mmhigh,respectively.
Fig.3.StaticWaterSupportandDeformationMeasurementSystem(SWSDMS)beingaccommodatedinaroadwaymodelinthereal3-Dloadedphysicalmodellingsystem.
3.3.Constructionofphysicalmodel
Thecompositionsandpropertiesofmaterialstobeusedfortheconstructionofphysicalmodelswerestudiedpriortothephysicalmodelconstruction.Giventhesignificantrheologicaldeformationofroadwaysexcavatedinsoftrock,sandandparaffinwaxwerechosenforthesimulatedsoftrock.Thepropertiesofaseriesofsand/paraffinwaxmixtureswerestudiedinlaboratoryandarepresentedinTable1.
Table1Compositionsandpropertiesofsand/paraffinwaxmixtures
Accordingtothegeotechnicalconditionsoftheprototyperockmassandthemodelscale,amixtureofsand/paraffinwaxof100:
3wasselectedtoconstructtherockmassmodel.Theproceduresinvolvedinthemodelconstructionincludecoldmixingofthesandandparaffinwax,ovenheatingthesand/waxmixtureandconstructingthephysicalmodelusingthehotsand/waxmixture.
3.4.Processofphysicalmodelling
Therealprocessofanundergroundroadwayexcavation,supportinstallationanddeformationofthesurroundingrockswithtimewassimulatedinthelaboratoryphysicalmodelling.Afterthemodelhadcooleddown,prestressingthemodel,excavationoftheroadwayunderpressure,installationoftheSWSDMSdeviceandmeasurementoftheroadwaydeformationwerecarriedoutstepbystep.Thewholeprocessofmodellingwass