本科生畢業設計（論文）題目：花園煤礦1.8Mt/a新井設計綜采放頂煤工作面采出率分析及提高措施摘要本設計包括三個部分：一般部分、專題部分和翻譯部分。一般部分為花園煤礦1.8Mt/a新井設計。花園煤礦位于山東省濟寧市金鄉縣，交通便利。井田走向（東西）長度最大約為5.454km，最小約為3.868km，傾斜（南北）長度最大約為3.252km，最小約為1.905km，總面積為13.97km2。主采煤層為15＃煤，煤層傾角為6~18，平均總厚度為12m。井田地質條件較為簡單。井田工業儲量為172.53Mt，可采儲量為114.5Mt。礦井設計生產能力為1.8Mt/a。礦井服務年限為49a，涌水量不大，礦井正常涌水量為86m3/h，最大涌水量為99.7m3/h。礦井瓦斯相對涌出量為1.732m3/t，絕對涌出量為6.866m3/min，為低瓦斯礦井。井田開拓方式為立井單水平開拓。采用膠帶輸送機運煤，采用礦車進行輔助運輸。礦井通風方式前期為中央并列式通風，后期增設2號風井通風。礦井年工作日為330d，工作制度為“三八”制。一般部分共包括10章：1、礦區概述與井田地質特征；2、井田境界和儲量；3、礦井工作制度、設計生產能力及服務年限；4、井田開拓；5、準備方式—帶區巷道布置；6、采煤方法；7、井下運輸；8、礦井提升；9、礦井通風與安全；10、設計礦井基本技術經濟指標。專題部分題目是綜采放頂煤采煤工作面采出率分析及提高措施，主要分析了綜放工作面煤炭損失及如何提高采出率的方法，從工程實例分析了煤層注水軟化致裂技術與深孔預裂爆破技術效果。翻譯部分主要內容關于頂板軟巖對回采巷道穩定性的影響，英文題目為：SOMEOFOUREFFORTSONTHEIMPROVEMENTOFMININGSAFETYANDTHERELIABILITIESOFMININGMACHINERIES。關鍵詞：立井；單水平；采區；中央并列式；中央分列式；綜采放頂煤ABSTRACTThisdesignincludesthreeparts:thegeneralpart,thespecialsubjectpartandthetranslationpart.Thegeneralpartisa1.8Mt/anewdesignforHuanyuancoalmine.HuanyuanislocatedinJinxiangofShandongprovince.Itisveryconvenienttogettothemineintermsofbothhighwayandrailway.Themaximumlengthofthecoalfieldis5.454km,andtheminimumlengthofthecoalfieldis3.868km,Themaximumwidthofthecoalfieldis3.252km,andtheminimumlengthofthecoalfieldis1.905km,andthetotalareais13.97km2.Thefifteenarethemaincoalseams,anditsdipangleis6~18degree.Thethicknessofthemineisabout3.43minall.Thegeologicstructureofthiscoalfieldissimple.Therecoverablereservesofthecoalfieldare172.53milliontons,andtheminablereservesare114.5milliontons.Thedesignedproductivecapacityis1.8milliontonspercentyear,andtheservicelifeofthemineis49years.Thenormalflowofthemineis86m3perhourandthemaxflowofthemineis99.7m3perhour.Therelativeminegasgushis1.732m3/tandtheabsolutegushis6.866m3/min,soitisalowgasmine.Themineisadoublelevelstodevelop.ThecentrallanewayusesBeltConveyortotransitcoal,andtrolleywagonsareusedforaccessorialtransportationintheroadway.Theprophaseventilationmodeofthismineiscenterjuxtaposeform,andthelateventilationmodeofthismineisdiagonalform.The“three-eight”workingsystemisusedintheTunliumine.Itproducesfor330daysayear.Thedeneraldesignincludestenchapters:1.Anoutlineoftheminefieldgeology;2.Boundaryandthereservesofmine;3.Theservicelifeandworkingsystemofmine;4.developmentengineeringofcoalfield;5.Thelayoutofpanels;6.Themethodusedincoalmining;7.Undergroundtransportationofthemine;8.Theliftingofthemine;9.Theventilationandthesafetyoperationofthemine;10.Thebasiceconomicandtechnicalnormsofthedesignedmine.Thetopicofspecialsubjectpartiscrossminingdriftwallrockdeformationregularityandsupportingtechnicalanalysis,thepaperanalyzestheacrossadoptdriftwallrockdeformationandthefactorsaffectingthedeformationregularity,andfromacrosstheroadwaydeformationcausedbymining,analysesthefactorsinrecentyearsinthecrossofroadwaysupportingtheoryandtechnology,fromengineeringexampleanalyzedthegruntingreinforcementtocrossminingroadwayeffect.TranslationpartisaboatLmprovementofMiningSafetyandtheReliabilitiesofMiningMachineries.TheEnglishtitleis“SomeofOurEffortsontheLmprovementofMiningSafetyandtheReliabilitiesofMiningMachineries”.Keywords:Verticalshaft;Singlelevel;District;Centralabreast;Centralboundary;Fullymechanizedminingwithsublevelcaving.英文原文SOMEOFOUREFFORTSONTHEIMPROVEMENTOFMININGSAFETYANDTHERELIABILITIESOFMININGMACHINERIESAbstract:Toimprovethesafetyofcoalmineandthereliabilitiesofminingmachineriesisthemainaspectofpresentscientificresearch.Thispaperintroducessomeofeffortsandachievementsinthisfield.Theyare:(1)Theselectiveearthleakageprotectionof6KVundergroundpowersupplysystemwithinsulatedneutral;(2)Thedetectionofminemethaneandpowersupplytrippingdevice;(3)Theprotectionagainstthehazardofundergroundstaticelectriccharge;(4)Theresearchofreliabilityoftheshearermotor;(5)Thetestandimprovementsofthereliabilitiesofminingmachineries.INTRODUCTIONInthelast50or60yearsthecoalminingindustriesallovertheworldmadegreatadvancesinmechanizationandsafety.Ourcountryhadalsolargeimprovementsinthesefields,butlargeamountsofworkshavetobedone.Recentlytheproblemofreliabilitiesofminingmachineriesdrewmuchattentionsofmanycountriesandwasconsideredasthemaindirectionofminingresearch.Formorethanadecade,inthesametimeofimprovingthedegreeofmechanizationofourcoalmines,weworkedalsoonminesafetyandreliabilitiesofminingmachineriesandgotsomeachievements.Letmemakesomesimpleintroductiononthem.NumericalmodellingoftheeffectsofweakimmediaterooflithologyoncoalmineroadwaystabilityAbstract:ThestabilityandassociateddesignofroofreinforcementrequirementsoftunnelsdriveninUnitedKingdom.CoalMeasuresstrataisdirectlyrelatedtotheengineeringcharacteristicsoftheimmediaterooflithologyandtheeffectsofredistributionofthein-situstress.Numericalmodellingcarriedoutbytheauthorshasbeenusedtosimulatethewidelyobserveddetrimentaleffectsofbothhighhorizontalstressandweakimmediaterooflithologyontunnelroofstability.Differentnumericalmodellingtechniques,suchascontinuum,discontinuumandhybridfiniteelement-discreteelementcodes,havebeenusedtomodelthedeformationalbehaviourofCoalMeasuresstrataandarediscussedinthecontextofspecificcaseexamplestohighlighttheirapplicationandsuitabilityformodellingofweakrock.Themodelledresultsdemonstratethatthethicknessoftherelativelyweakmudstoneintheroofofthetunnelhasasignificantinfluenceontheextentoffailureand,ultimately,theneedforadditionalreinforcement.1.IntroductionUntilrecently5minesworkedtheBarnsleyseamintheSelbyComplex(Wistow,Stillingfleet,Riccall,WhitemoorandNorthSelby).Theseamdipsatapproximately7°totheNorth-East,rangingindepthfrom250mWestoftheWistowMinetoinexcessof1200mEastoftheNorthSelbyMine.Typicalseamthicknessvariesfrom3.5mintheWestto1.8mintheEastoftheSelbyCoalfield.Theroofstratatypicallyconsistofanimmediate,relativelyweakmudstone(upto1mthick)overlainbymorecompetentsiltymudstones,siltstonesandsandstones.ThemudstonethicknessvariesacrosstheCoalfield,rangingfromnon-existentduetohighenergydepositionalriverchannelswherethesandstoneliesdirectlyabovetheseamtoanextensivethicknessofgreaterthan4m.Typicaltunnelorroadwaydimensionsare3.5mhighby5.0mwide.ThesuccessfulimplementationandsubsequentuseofroofboltinginUnitedKingdomcoalminetunnelshaveprovidedalargedatabaseoftunneldeformationmonitoringinformation,includingin-situmeasurementofstratabehaviour,tunneldeformationandreinforcementperformance.Kentetal.(1999)providedasummaryoftheanalysisandinterpretationofdeformationmonitoringdatafromacrosstheSelbyComplexduringtheperiod1988to1994.ThedatabaseprovidedanidealopportunitytoinvestigatehowgeologicalandstressvariationsaffectthestabilityanddeformationalbehaviouroftunnelsdriventhroughCoalMeasuresstrata.Thedatawereestablishedfortunnelsondrivage,priortofaceretreatandanyadditionaldeformationassociatedwithlongwallextraction.DetailedanalysisofthedatabaseconfirmedthatthestabilityandassociateddesignofroofreinforcementrequirementsoftunnelsdriveninUnitedKingdomCoalMeasuresstrataisdirectlyrelatedtothelithologyoftheimmediateroofoftheexcavationandtheredistributionofthein-situstresscausedbycreationoftheexcavation(Hurt(1992),Kent(1996),Kentetal.(1999)andSiddallandGale(1992)).Forexample,significantincreaseintunnelroofdeformationisobservedwhenexcavationsaredrivenperpendiculartothemaximumhorizontalprincipalstressdirection.Tunnelsdrivenatanangletothein-situstressfieldsufferasymmetricaldeformation,withpronouncedobservedstresseffectsthatrequireadditionalreinforcementforstability.Theseobservedeffectsincludetheformationof“guttering”orexcessivebulging/bulkingoftheimmediateroof.Thethicknessoftherelativelyweakmudstoneintheroofofthetunnelhasasignificantinfluenceontheextentoffailureand,ultimately,theneedforadditionalreinforcement.Recentnumericalmodellingcarriedoutby,orundertakenaspartofresearchsupervisedbytheauthorsoverthelastfifteenyearshasprovidedawiderangeofcaseexamplesanddifferentapplicationsofuseofnumericalmethodstomodelweakrockbehaviour.Thishasinvolvedtheuseofacombinationofcontinuum,discontinuumandhybridmethods,wherethechoiceofthenumericalmethodadoptedtookintoconsiderationthecapabilitiesandlimitationsofthesoftware.Thefactorsconsideredincluded:choiceofappropriateinputparameterssuchasmaterialconstitutivecriteria,whetherthereisaneedtomodeldiscontinuitybehaviour,whatfailuremechanismisbeingsimulatedandwhetherornotthereisaneedfortwoorthree-dimensionalanalysis.Themodellinghasbeenusedtosimulatethewidelyobserveddetrimentaleffectsofbothhighhorizontalstressandweakimmediaterooflithologyontunnelroofstability,usingspecificcaseexamplestakenfromtheSelbyCoalfield.Thedetrimentaleffectsofweakrooflithologyontunnelroofbehaviouraredemonstratedusingboth2and3-dimensionalnumericalmodelling.Theexamplesconcentrateonthemodellingoftunnelroofbehaviour,includingfractureinitiationandsubsequentpropagationofthefracturezoneintheimmediateroofoftheexcavation.2.Numericalmodelling:availablemethods—theiradvantagesanddisadvantagesTable1providesasummaryoftheadvantagesandlimitationsofthemostcommonlyusednumericalmethodsformodellingoftunnelroofbehaviour,whicharecontinuummethods,discontinuumordiscretemethodsandhybridcontinuum/discretemethods.ExamplesoftheapplicationofthesedifferentnumericalmethodstomodellingtheeffectsofrockfailurearoundundergroundexcavationsincludeAlvarez-Fernandezetal.(2009),BartonandPandey(2011),Cogganetal.(2003,2006),Curranetal.(2003),Eberhardt(2001),Galeetal.(2004),Islametal.(2009),IslamandShinjo(2009),MartinandMaybee(2000),Pineetal.(2006)UnverandYasitli(2006)andZipf(2006).2.1.ChoiceofavailablemethodsSuccessfulapplicationofthevariousmethodsavailableformodelingofcoalmineroofbehaviourrequiresasoundknowledgeofthecapabilities,advantagesandlimitationsofthevariousmethodsused.Alvarez-Fernandezetal.(2009),Islametal.(2009),IslamandShinjo(2009)andUnverandYasitli(2006)haveshownhownumericalmodellingtechniquescanbeusedtosimulatecoalstratadeformation.Cassieetal.(1999),Clifford(2004),Garrett(1997),Meyer(2002),Sharpe(1999)andSharpeetal.(1998)havealldemonstratedhownumericalmodellingcanbeusedtoprovideguidanceforreinforcementdesignincoalmineroadwaysintheUnitedKingdom.Itisimportanttomatchthecapabilitiesofthesoftwaretotheengineeringsituationbeingmodelled.Forexample,relativelysimplisticboundaryelementmodellingcanprovideusefulsimulationofstressredistributionandcoalstratadeformationaroundcoalmineroadways(IslamandShinjo,2009),butmoresophisticatedmodelsarerequiredtomodelthedetrimentaleffectsofprogressiverockfailureandfracturebehaviour(UnverandYasitli,2006).ResearchsummarisedbyClifford(2004)highlightstheuseofaboundaryelementapproachtoinitiallymodelthethree-dimensionalstressredistributionaroundacoallongwallpanelbeforeundertakingmoredetailedtwo-dimensionalfinitedifferencemodellingofroadwaybehaviour.Thestressoutputfromtheboundaryelementmodelisusedasinputforthesubsequenttwo-dimensionalcontinuummodelling.Thishighlightsthatresultsfromacombinationofmodelingmethodsmayprovideusefulinsightforaparticularproblembeingmodelled.Itisoftenbeneficialtoadoptamodellingphilosophywherebysimplemodelsareinitiallydevelopedtounderstandthemechanicsandimportantcriticalfactorsinfluencingthedesignpriortoundertakingmoresophisticatedmodels.Modelledoutputshouldalsobevalidatedagainstin-situobservationsand,whereavailable,datafromdeformationandstressmeasurementsfromappropriateinstrumentation.Oncetheappropriatemethodhasbeenchosenthenextkeypartofasuccessfulnumericalmodellingstrategyisthecorrectchoiceofsuitableinputparameters.2.2.ChoiceofinputparametersThedeterminationofinputparametersfornumericalmodellingisnotatrivialtask.Table1highlightsthatasmodelsbecomemorecomplexanimprovedunderstandingofconstitutivecriteriaandassociatedinputsisrequiredtotakefulladvantageoftheincreasedmodelcapability.Obtainingrepresentativeinputparametersisessentialforsuccessfulmodelling,particularlywhenscalingpropertiesfromlaboratorytoin-situorrockmassscale.Variousapproachesareavailableforscalingofrockmassproperties.Theseinclude:?Scalingoflaboratorytestdata—intactrockstrengthpropertiesareadjustedusingreductionorscalingfactors,suggestedbyWilson(1983)forapplicationtoUnitedKingdomcoalenvironments,?Useofpeakandresidualstressversusstraindataasinputforvariousconstitutivecriteriaincludingcohesionweakening,cohesionsofteningfrictionhardeningandubiquitousjointapproaches(FangandHarrison(2002),Hajiabdolmajidetal.(2002),Meyer(2002),Sharpe(1999)),?UseofGSI-basedHoek–Brownformulations(HoekandBrown(1997),Pineetal.(2006)andUnverandYasitli(2006)),?Useofadiscretefracturenetwork(DFN)(Pineetal.(2006),ElmoandStead(2010))orsyntheticrockmassapproach(SRM)(Pierceetal.,2007),wherebyrockmasspropertiesarederivedfrommodelledintactanddiscontinuitybehaviour.DerivationofmodelinputparametersfortypicalUnitedKingdomCoalMeasuresstrataisbasedonevaluationandcomparisonwithmultistagetriaxialtestdata.Acohesionweakeningcriterionisnormallyadoptedtorepresentthebrittle-plasticbehaviourandpeakandresidualpropertiesofthedifferentstrata.Sensitivityanalysesarethenperformedtoassessthepotentialimpactofvariabilityofinputdataonmodeloutput.GSIevaluationforderivationofrockmassqualityandrockmassmaterialpropertiesisnotroutinelyperformedfordesignofroadwaysinCoalMeasuresstrataintheUnitedKingdom.TypicalrangesofresidualcohesionvaluesforthedifferentroofstratacanbefoundinTable2.3.Numericalmodellingofcoalmineroadwayroofbehaviour3.1.ModellingtheeffectsofhorizontalstressdirectionRepresentativerooflithologyandin-situstressconditionshavebeenmodelledforatypicaltunnelorroadway(5mwideand3.5mhigh)driventhroughtheCoalMeasuresstrataoftheSelbyCoalfield.In-situstressmeasurementsandundergroundstressmappingobservationsfromtheSelbyCoalfieldhaveconfirmedthattheorientationofthemaximumhorizontalstressdirection(approximatelyNW-SE)isconsistentwiththenationaltrend(Bigbyetal.,1992andCartwright,1997),althoughvariationsmayexistincloseproximitytomajorfaults.Themaximumhorizontalstressistypically1.5to1.7timestheminorhorizontalstress,andoftengreaterthantheverticalstress.Theverticalstresshasbeenshowntobeafunctionofdepthbelowsurface(Kentetal.,2002).Previouselasticandsimplenon-linearmodellingcarriedoutbyMeyeretal.(1999a,b)usingFLAC3D(Itasca,1997),clearlydemonstratedthethreedimensionalnatureofstressredistribution,andtheassociatedfailurezone,arounda5mwideby3.5mhightunnelface-endattheNorthSelbyMine.Thein-situstressfieldincorporatedinthemodelshadamaximumhorizontalstressof25MPa,aminimumhorizontalstressof15MPaandaverticalstressof16MPa.ThemodelsalsoincorporatedrepresentativeCoalMeasuresrooflithologyandassociatedmaterialproperties,asshowninTable2.Theorientationofthisstressfieldrelativetothetunneldrivagedirectionwasvariedinordertoassesstheimpactofstressfieldorientationonroadwaydeformationandultimatelyreinforcementrequirements.Initialmodellingconcentratedonelasticanalysispriortonon-linearmodellingthatincorporatedsystematictunneladvanceandsupportinstallation.3.2.ModellingtheeffectsofmudstonethicknessintheimmediateroofPHASE2hasalsobeenusedtoshowthedetrimentaleffectsofanincreasedthicknessofmudstoneintheimmediateroofofthetunnelforthestressparallelcase(mostfavourablestressdirection).Fig.8illustratesthemodelledstressredistributionandextentoftheassociatedfailurezoneforamudstonethicknessof1,2and3mintheimmediatetunnelroof.Thefigureclearlyshowsthattheextentofthefailurezoneiscontrolledbythethicknessofmudstoneintheimmediateroof.ThiswasalsonotedbyKentetal.(1999),whoshowedthatincreasedroofdeformationwasassociatedwithtunnelroofsincorporatingincreasedthicknessesofmudstone(Fig.9).Fig.8alsodemonstratestheextentofthefailurezone“abovetheboltedheight”forthemodelled3mofmudstoneintheroof,whichsuggeststhatundertheseconditionscableboltingwouldalsoberequiredtostabilizetheexcavation.3.3.ModellingofprogressiverooffailureandfracturepropagationDependingonthenatureofthestressregimeactingonanexcavation,andtheassociateddeformationalbehaviouroftherockmasssurroundingtheexcavation,anumberofpotentialfailuremechanismscanexist.Thesecaninvolveacombinationofshearfailureonexistingjoints/weaknesshorizons,extensionofcriticallyorientedjointsandpropagationofnewfracturesthroughpreviouslyintactrock.Bothcontinuumanddiscontinuummodelsmaybeusedtosimulateprogressiverockfailurebyadoptingvariousconstitutivecriteriaassociatedwitheithermaterialbehaviourand/ordiscontinuityrelatedbehaviour.Forexample,usingacontinuumapproach,Meyer(2002)adoptedacohesion-weakeningcriterionfortheimmediaterooflithologyofthemodelledyieldzoneshowninFigs.5and6.Sharpe(1999),usingadiscontinuumapproach(UDEC(Itasca,1997)),wasabletomodeljointopeningaboveatunnelsitedadjacenttopreviouslongwallworkingswheninvestigatingtheeffectsofstressredistributionandgoaf-edgecavingconditionsontunnelstability.Galeetal.(2004)wereabletosimulaterooffailuremechanismsusingastrainsofteningpost-failurecriterionthatcanincorporateweaknessplanes,inasimilarwaytothestrainsoftening,ubiquitouscodewithinFLAC3D(Itasca,1997).Althoughbothcontinuumanddiscontinuummodelsprovideusefulanalysisforinterpretationoffailurearoundundergroundexcavations,neitherapproachisabletoeffectivelycapturetheinteractionofexistingdiscontinuitiesandthecreationofnewfracturesthroughfracturingofintactrock.Cogganetal.(2003),Klercketal.(2004)Pineetal.(2006)andSteadetal.(2004)highlightedthebenefitsofthehybridfinite/discreteelementcodeELFEN(Rockfield,2004)tomodelprogressivefracturedevelopmentinbothundergroundandsurfaceexcavationexamples.Thecodehasalsobeenusedbytheauthorstomodelprogressivedevelopmentofshear-relatedfailureintheimmediateroofofatunnel,asshowninFig.10.Fig.10depictsselectedstagesinthesimulationoffracturedevelopmentintheimmediateroofofacoalminetunnel.Themodelledrooflithologyisrepresentativeofatypicalmudstone.Thefigureillustratesprogressiveplasticstraindevelopmentpriortosubsequentfracturingoftheimmediateroof,whichcomparesfavourablywiththeobservedshear-typefailuredescribedbyAltounyanandTaljaard(2000),showninFig.11.Cogganetal.(2003)alsodemonstratedhowthehybridcodecouldbeusedtoinvestigateroofbeambehaviour.TheUDECVoronoimodel(Itasca,2011)hasbeenusedtoexplicitlymodelthegeneration,propagationandcoalescenceoffracturesaroundacoaltunnelsubjectedtoamajorhorizontalstressorientedperpendiculartotunneldrivedirection.IntheUDECVoronoimodel,materialisrepresentedasadensepackingofpolygonalblocksinteractingtogetherattheirboundaries.Micro-properties,suchascohesion,friction,andtensilestrengthareassignedtotheboundariesofthesepolygonalblocks.Fracturesareinitiatedwithintheintactmaterialwhenthestressesappliedonthecontactsexceedeitherthetensileorshearstrength.Pre-existingfracturescanalsobeincorporatedbycreatingcracksandassigningspecificproperties,suchaszerotensilestrengthandcohesion.Fig.12showsselectedstagesinthesimulationoffracturedevelopmentaroundamodelledcoalminetunnel.Beddingwasincorporatedinthemodel.Fracturegenerationstartsatthetunnelcornerswheretheinitialstressconcentrationoccurs.Fracturesthenextendintotheroofandfloor.Themodelrealisticallyproducedbeddingdeflectionintheimmediateroof,separationanddevelopmentofafailurezonearoundtheexcavation.Brittlespallingalsooccursinthesidewallsofthemodelledcoalmineroadway3.4.Modellingofroofbeambehaviorroofbeambehaviour.Snapshotsoftheearlystagesofroofbeamfailureprocessprovideinsightintotheresultantunderlyingfailuremechanisms.Onlythe0.2%plasticstraincontourandresultantmodeledfracturehasbeenincludedinFig.14forclarity.Fig.14aandbshowsdifferentfailuremechanismsforthestressconditionsmodelled.Fig.14ashowspreferentialstraindevelopmentintheroofbeamadjacenttotheedgeofthetunnelroof,whereasFig.4bshowsthedevelopmentoftensilefracturingatthebaseofthecentreofthemodelledroofbeam.Furtherdevelopmentofthemodelledfailureresultsinseparationoftheroofbeamawayfromtheupperroofhorizonatthecentreoftheroofspan.AnexampleofobserveddevelopmentoftensilecrackingintheroofofcoaltunnelisprovidedinFig.15.Themodellingresultssuggestthatthehybridcodemaybeusedtoinvestigatethesnap-through,crushing,slidinganddiagonalcrackingmodesofrooffailuredescribedbyDiederichsandKaiser(1999),andtheeffectsofvaryingcombinationsofthickandthinroofbeamsonexcavationroofstabilitydescribedbyGoodman(1980).4.DiscussionandconclusionsWhenvalidatedagainstin-situmonitoringdatanumericalmodelingcanprovideusefulinsightsintocoalminetunnelroofbehaviorandassociatedreinforcementdesign.Modellingcanbeusedtoconfirmthedetrimentaleffectsofadversein-situstressorientation.Tunnelsdrivenperpendiculartoahighhorizontalstressdirectionsuffergreaterdeformationandincreasedfailurezoneswhencomparedtotunnelsdriveninastress-paralleldirection.Theextentofthemodelledfailurezoneiscontrolledbythethicknessofweakmudstoneintheimmediateroofofthetunnel.Tunnelsdrivenatanangletothein-situstressfieldsufferasymmetricaldeformation,withpronouncedstresseffectsthatrequireadditionalreinforcement.Three-dimensionalmodellingisrequiredtoeffectivelycapturethethree-dimensionalnatureofthestressredistributionaroundatunnelface-end,particularlywhenthemaximumhorizontalstressisalignedatangletothetunneldrivagedirection.Table1providesasummaryofkeyadvantagesandlimitations/disadvantagesforcontinuum,discontinuumandhybridmethodsofanalysisappliedtomodellingoftunnelroofbehaviour.Thecorrectchoiceofmethodusedwilldependonthecomplexityoftheproblem,presenceofdiscontinuities,materialbehaviour,in-situstressregimeetc.Asignificantlimitationofmostpublishedmodellingofundergroundcoalminesto-dateisalackofconsiderationofintactrockfractureanditsimplicationforstress-redistribution,energyreleaseandchangesinkinematicconstraints.Akeyadvantageofmodellingisthecapabilitytorapidlyassesschangesinparameterssuchasthicknessofimmediaterooflithologyonextentoffailureandassociateddeformation,asshowninFig.8.Thetechniquesareextremelyuseful,butrequireduediligenceforthemodelingtobeeffective.Itisimportantthattheuserbefamiliarwiththepotentiallimitationsofeachofthedifferenttypesofavailablesoftware.Forexample,constraintsassociatedwithtwo-dimensionalanalysis(suchastheassumptionofplanestrain)canproduceanoversimplifiedrepresentationofsiteconditions.Significantfurtheradvancesinourunderstandingwillrequiretheuseofthree-dimensionaldiscreteelement/hybridcodeswithfracturepropagationalgorithms;this,however,willnecessitatefurtherresearchtovalidatethemodelledcasehistories.Improvementsinparallelprocessingcodingofsoftwareandcomputerpowerwillbeessentialtomodelmoredetailedlargescalethreedimensionalexamples.AcknowledgementsTheauthorswouldliketothanktheEditorandtwoanonymousreviewersfortheirhelpfulandconstructivecomments.TheywouldalsoliketothankthecontributionofseveralPhDstudentsattheCamborneSchoolofMinesincluding,BrianClifford,LewisMeyerandLeighSharpeandresearchcollaborationwithRockMechanicsTechnology(nowGolderAssociates)andRockfieldSoftwareLtd.ReferencesAlvarez-Fernandez,M.I.,Gouzalez-Nicienza,C.,Alvarz-Vigil,A.E.,HerreraGarcia,G.,Torno,S.,2009.Numericalmodellingandanalysisoftheinfluenceoflocalvariationinthethicknessofacoalseamonsurroundingstresses:applicationtoapracticalcase.InternationalJournalofCoalGeology79,157–166.Altounyan,P.F.R.,Taljaard,D.,2000.DevelopmentsincontrollingtheroofinSouthAfricancoalmines—asmarterapproach.Coal—thefuture.12thInternationalConferenceonCoalResearch.SouthAfricanInstituteofMiningandMetallurgy,pp.39–46.Barton,N.,Pandey,S.K.,2011.NumericalmodellingoftwostopingmethodsintwoIndianminesusingdegradationofcand?basedonQ-parameters.InternationalJournalofRockMechanics&MiningSciences48,1095–1112.Bigby,D.N.,Cassie,J.W.,Ledger,A.R.,1992.