祁东煤矿2.4Mt-a新井设计-煤与瓦斯突出煤层的开采技术

本科生毕业设计（论文）题目：祁东煤矿2.4Mt/a新井设计煤与瓦斯突出煤层的开采技术摘要本设计包括三个部分：一般部分、专题部分和翻译部分。一般部分为祁东煤矿2.4Mt/a新井设计。祁东煤矿位于安徽省宿州市境内，交通便利。井田走向（东西）长约9km，倾向（南北）长约3km，总面积为27km2。主采煤层为61、71煤，煤层倾角平均14°，平均总厚度为10m。井田地质条件较为简单。井田工业储量为313.16Mt，可采储量为238.10Mt。矿井设计生产能力为2.4Mt/a。矿井服务年限为70.8a，涌水量不大，矿井正常涌水量为437.06m3/h，最大涌水量为586.10m3/h。矿井瓦斯相对涌出量为20m3/t，绝对涌出量为20m3/min，为高瓦斯矿井。井田开拓方式为立井两水平上山开拓，二水平采用暗斜井延深。采用胶带输送机运煤，采用矿车进行辅助运输。矿井通风方式为两翼对角式通风。全矿采用采区准备方式，共划分为四个工作面，并进行了运煤、通风、运料、排矸、供电系统设计。针对61201工作面进行了采煤工艺设计。该工作面煤层平均厚度为7.0m，平均倾角15°。工作面采用综采放顶煤采煤法。采用双滚筒采煤机割煤，往返一次割两刀。采用“四六制”工作制度，截深0.8m，每天六个循环，循环进尺0.8m，月推进度144m。一般部分共包括10章：1、矿区概述与地质特征；2、井田境界和储量；3、矿井工作制度、设计生产能力及服务年限；4、井田开拓；5、采区巷道布置；6、采煤方法；7、井下运输；8、矿井提升；9、矿井通风与安全；10、设计矿井基本技术经济指标。专题部分题目是煤与瓦斯突出煤层的开采技术，主要是介绍了煤与瓦斯突出煤层的瓦斯抽放原理和卸压措施，全面阐述了煤与瓦斯突出煤层的瓦斯抽放、煤与瓦斯共采技术。翻译部分主要内容是关于澳大利亚两大地下开采方法——壁式、房柱式采煤法的介绍，英文题目为：GeologicalandgeotechnicalaspectsofundergroundcoalminingmethodswithinAustralia。关键词：立井；暗斜井延深；两水平；采区布置；两翼对角式通风；综合机械化放顶煤采煤方法

ABSTRACTThisdesignincludesthreeparts:thegeneralpart,thespecialsubjectpartandthetranslationpart.Thegeneralpartisabouta2.4Mt/anewdesignforQidongmine.QidongmineislocatedinSuzhouCity,Anhuiprovince.thetrafficisconvenient.Thelengthofthecoalfieldis9km,thewidthisabout3km，andthetotalareais27km2.The61&71isthemaincoalseamswithaveragedipof14°.Thethicknessofthemineisabout10minall.Thegeologicstructureofthiscoalfieldissimple.Therecoverablereservesofthecoalfieldare313.16milliontonsandtheminablereservesare238.10milliontons.Thedesignedproductivecapacityis2.4milliontonspercentyear,andtheservicelifeofthemineis70.8years.Thenormalflowofthemineis437.06m3perhourandthemaxflowofthemineis586.10m3perhour.Therelativeminegasgushis20m3/tandtheabsolutegushis20m3/min,soitisalowgasmine.Themineisaverticalshaftdevelopmentwithtwomininglevelsandtheextensionofblindinclinedshaft.Tecentrallanewayusesbeltconveyortotransitcoal,andtrolleywagonsareusedforaccessorialtransportationintheroadway.Theventilationmodeofthismineistwowingsofdiagonalventilation.Thedesignappliesdistrictpreparationagainstthesecondwesterndistrict,whichdividedintofourlongwallfacestotally,andconductedcoalconveyance,ventilation,gangueconveyanceandelectricitydesigning.Thedesignconductedcoalminingtechnologydesignagainstthe61201face.Thecoalseamaveragethicknessofthislongwallfaceis7.0mandtheaveragedipis15°,Thefaceappliesfully-mechanizedcoalcavingminingmethod,andusesdoubledrumshearercuttingcoalwhichcutsonceeachworkingcycle.“Four-Six”workingsystemhasbeenusedinthisdesignandthedepth-webis0.8mwithsixworkingcyclesperday,andtheadvanceofaworkingcycleis0.8m.Sotheadvanceis144mpermonth.Thisdesignincludestenchapters:1.Anoutlineoftheminefieldgeology;2.Boundaryandthereservesofmine;3.Theservicelifeandworkingsystemofmine;4.developmentengineeringofcoalfield;5.miningdistrictpreparation;6.Themethodusedincoalmining;7.Undergroundtransportationofthemine;8.Theliftingofthemine;9.Theventilationandthesafetyoperationofthemine;10.Thebasiceconomicandtechnicalnormsofthedesignedmine.Thetopicofspecialsubjectpartsisminingtechnologyofcoalandgasoutburst,describesthecoalandgasoutburstofgasdrainageprinciplesandreliefmeasures,acomprehensiveexpositionofthecoalandgasoutburst,gasdrainage,coalandgasextractiontechnology.TranslationpartisastudyonundergroundcoalminingmethodswithinAustralia.TheEnglishtitleis:GeologicalandgeotechnicalaspectsofundergroundcoalminingmethodswithinAustralia.Keywords:Verticalshaft;Blindinclinedshaft;Twolevels;Miningdistrictpreparation;Twowingsofdiagonalventilation;Fully-mechanizedcoalcavingmining第页英文原文GeologicalandgeotechnicalaspectsofundergroundcoalminingmethodswithinAustraliaB.Scott·P.G.Ranjtih·S.K.Choi·ManojKhandelwalAbstract:AboutonequarterofthecoalproducedinAustraliaisbyundergroundminingmethods.ThemostcommonlyusedundergroundcoalminingmethodsinAustraliaarelongwall,androomandpillar.Thispaperprovidesadetailedreviewofthetwomethods,includingtheiradvantagesanddisadvantages,themajorgeotechnicalandoperationalissues,andthefactorsthatneedtobeconsideredregardingtheirchoice,includingthevaryinggeologicalandgeotechnicalconditionssuitedtoaparticularmethod.Factorsandissuessuchascapitalcost,productivity,recovery,versatilityandminesafetyassociatedwiththetwomethodsarediscussedandcompared.Themajoradvantagesofthelongwallminingmethodincludeitssuitabilityforminingatgreaterdepth,higherrecovery,andhigherproductionratecomparedtoroomandpillar.Themaindisadvantagesoftheroomandpillarmethodarethehigherrisksofroofandpillarcollapse,highercapitalcostsincurredaswellaslowerrecoveryrate.Keywords:Longwall·Roomandpillar·Geological·GeotechnicalIntroduction:MininginAustraliaisasignificantprimaryindustryandcontributortotheeconomyofAustraliaandencouragedimmigrationtoAustralia.Manydifferentoresandmineralsareminedthroughoutthecountry.Withtheincreaseincoaldemandandgrowingawarenesstowardssustainabledevelopment,thecoalindustryhasdrawnaconsensusovertheneedforincreasedproductionfromundergroundcoalmines.Aroundtheworld,themajorityofcoalreservesarerecoverableusingundergroundminingtechniques.Atthemoment,almosttwo-thirdsofcoalproductioncomesfromundergroundmines,however,inAustraliathisstatisticissignificantlylower(ACA2006).CurrentlyinAustralia,themajorityofundergroundcoalminesarelocatedinNewSouthWalesandCentralandWesternQueensland,wherethinnerblackcoalseamssuittheundergroundminingmethods.Thereareanumberofdifferenttypesofaccessmodesforundergroundmining.Theseincludedrift,incline/declineandshaft,andcanbeusedinconjunctionwitheitherofthethreemodesforundergroundminingwithinAustralia.Driftisgenerallyusedwhenthecoaldepositisinsideofahill,andminingisundertakenbyenteringdirectlyintothehill(Ghose1984).Incline/declineiscreatedatthegroundlevelofavalley,whereanaditisconstructedandslopesdowntothecoal.Shaftisusedwithanelevator,whichstretchesfromthesurfacetothecoalseamunderground(Wilson1983).Themainaimofthepaperistoidentifyandcomparevarioustechniquesusedforcoalextractionsandtheselectionprocessofthosetechniquesforaparticularsitebasedongeological,geotechnicalandotherfactors.ThetwomajormethodsofundergroundminingwithinAustraliaandaroundtheworldareroomandpillarandlongwallmining,andthesetwomethodswillbediscussedindetailsbelow.CurrentstatesofAustralianundergroundandopen-cutcoalminingoperationsInordertogainanunderstandingofthecurrentstateofcoalminingoperationsinAustralia,abroadoverviewisgivenbeforemethodsuitabilityforcoalminesisdiscussed.InAustralia,opencutminingproducesthemostamountofcoalforbothexportandinternaluses.In2004forexample,81.5milliontonnesofcoalwasminedusingundergroundmethods,whilst296.3milliontonneswereobtainedusingmethodswithinanopencutsystem(UniversityofWollongong2006).Thisisofnosurpriseasnearlytwo-thirdsofalloperatingmineswithinAustraliaareopencut,ascanbeseenfromTable1andFig.1below.Table1TypeofminesoperatingwithinAustralia(GNSW2006;GSA2006;GWA2006;GT2006;GV2006;GQ2006)MinetypesbystateStateUndergroundSurfaceTotalcoalminesQueensland103040NewSouthWales272552WesternAustralia066Tasmania123Victoria178SouthAustralia011Total3971110Fig.1MapofAustraliancoalbasins(DPMC2006)WithinAustralia,browncoalistypicallyfoundinthesouthernpart,withblackcoalfoundinthebasinsofNewSouthWalesandQueensland.Beforeproceedingfurther,aquickoverviewofcoalrankandclassificationisgiven.Typically,coalrankisclassifiedintothreedistinctcategoriesdependingonthedegreeofmetamorphismthatthecoalformingmaterialhasenduredasitmaturesfrompeattoanthracite.Thesearelignite,sub-bituminousandbituminous,andthepropertiesofthesegreatlyinfluencethetypeofmethodusedtoexploitthecoal.Asmentioned,surfaceminingoropencastminingisthepredominantmethodusedinAustralia.OpencastminingonalargescalefirstcommencedinAustraliainthe1960s,whereimporteddraglineswerethemainmeansofstrippingoverburden.Thismethodcontinuedtobeusedoverthenext20–30years,andstilltoday,however,astheseamsbecamedeeperandthecomplexityofthecoalseamincreased,otherequipmentssuchastruckandshovel,anddozers,wereintroduced(Westcott2004).Today,draglinesandtruckandshoveloperations,oracombinationofthetwo,arethepredominantmodesofequipmentusedinopencastmines,asseeninFig.2below.Fig.2OpencastCoalMiningEquipmentusedinAustralia(Westcott2004)SelectionofexcavationmethodThedecisiononwhethertooperateanaboveorundergroundmineisheavilyinfluencedbyacoupleofimportantfactors.Themajorfactorindecidingonwhethertogoundergroundoropencutisthestrippingratio(Whittlesetal.2007).Thisisdefinedastheratioofthevolumeofoverburden(BCM)movedtotheamountofcoalproduced(tonnes).Asageneralrule,anythingpast20:1isconsideredtoolargearatioforabovegroundcoalminingaslargeamountsofoverburdenarerequiredtobemovedinordertoexposethecoalseam,thusundergroundmethodsshouldbeconsidered.Anotherfactorindecidingonthetechniquetobeemployedisthetypeofcoaltobemined.Ifthecoaldepositconsistsoflignite,whichisTertiaryinageandrangesfromabout15to50millionyearsold,thenabovegroundmethodsshouldbemorecloselyconsidered.Thisisduetothefactthatligniteisamuchsoftermaterialthanblackcoal,whichincreasesthepossibilityofroofcollapseormaterialcollapsingfromaboveduringminingduetotheyounger,unconsolidatedandsoftermaterialoverlayingthebrowncoal.Carefulconsideration,however,wouldalsoneedtobegiven,whenminingbrowncoalaboveground,asastrongbaseforthelarge,heavyequipmentwouldberequiredtoavoidbenchcollapseorotherfailure.Large,heavycoalhaulagetrucksmayalsofinditdifficulttooperateonthesofterlignite,especiallyduringwetweatherevents,wheretheweightoftheequipmentresultsinlargeamountsoftimelostduetotrucksbecomingbogged,wheelspin,etc.Otherfactorstobeconsidered,whichwillbeexpandeduponshortlyinclude:•Lifeofmine.Forexample,isitfeasibletooutlaylargecapitalforasmallcoaldeposit?•Requiredproductivity.Doyouneedahighproductionmachineorisitmorefeasibletomineconstantlyataslowerrate?•Amountofcapitalavailable.Ifthereisanyplantcurrentlyavailablewithinthecompany,andcanitbeutilised?Inthefollowingsectionsonlongwallandroomandpillarcoalmining,thetypicalgeologicalandminingconditionsforthetechniquestobeutilisedwillbediscussed,includingvariationsofthetechniques,aswellasexpectedproductivityandcostsexperiencedwithintheindustry.Thefollowingisapplicabletoeachproposedmethod(opencastorunderground):•Notwominesareexactlythesame.Geologicalprofiles,weather,capitalavailable,production,productivityrequirements,recoverablereserves,etc.areallindependentvariablesbetweendifferentmines,andassuch,itisimpossibletoprepareastandarddocument,whichcatersforeverypossiblemine(Bise1995).Largeamountsoftimearerequiredbyexperiencedengineersorspecialistconsultantsduringthepreliminaryandplanningstagesinordertodesignaminingmethodsuitedtoaparticularlocation.•Geotechnicalissuesareindependentateachlocation,andadetailedinvestigationattheveryleastshouldbeundertakeninordertounderstandthegroundconditions,geologicalprofile,etc.(Wilson1983).Thegeotechnicalissuesoutlinedwithinthispaperincludedifferentmodesoffailure,soilproperties,etc.however,itisnotwithinthescopeofthispapertodetaileverypossiblegeotechnicalissuewithregardstocoalmines.Majorproblemswillbeidentifiedalongwiththeconditionsthatcausesuchcircumstancestooccur.•Costingofmineequipmentandproductivityisofabroadnature,andcanbecalculatedusingthefollowingformulaproposedbyNoaksandLandz1993.Thecostin1992$Ahasbeenadjustedto2006valueusingtherecommendedformula:CostNow=(CostThen)×(CostIndexNow)/(CostIndexThen)where,thecostpriceindexes(CPI’s)forboth1992(CPI,March1992:107.1,opencut;108.1,underground)and2006(CPI,June2006:167.0,opencut;152.0,underground)havebeenobtainedfromtheAustralianBureauofStatistics(ABS2006).•Allvaluesandproductivityaregeneratedasapreliminaryestimateforapre-feasibilitystudylevelofaccuracy(±25%),anddoesnotreplaceanengineeredcostestimateorfeasibilitystudy.Theaccuracyofanyestimatewillbedirectlyproportionaltothequalityandquantityofdataavailableandtothetimeandeffortputintoitspreparationandproperexecution(NoaksandLandz1993).Thefollowingsectionsoutlinethetwoundergroundcoalminingalternatives(longwall,androomandpillarmining)specifyingwhichgeologicalconditionsarebettersuitedtoeachmethod,aswellasgeotechnicalissuesinvolved.LongwallminingLongwallminingisthemostcommonoftheundergroundcoalminingmethodsusedinAustralia.Itsuitssiteswherecoalseamsarethicker,wideandhaveaconsistentcoalprofilewithgentledip.Inlongwallmining,largerectangularsectionsofcoalareidentifiedandremovedinonecontinuousoperation(Truemanetal.2009).Basically,apanel,orblock,ofcoaliscreatedbydrivingasetofheadingsintothesectionofcoal(panel)foracertaindistance(typically1.5–3kmlong).Thesesetsofheadingsaregenerallyspacedatadistanceofapproximately100–250m(330–820ft)apart,andarejoinedtogethertoallowthelongwallminingmachinetoworkalongthelongwallface.Themechanisedshearerrunsalongtheface,cuttingandremovingthecoalasthemineadvancesalongthelengthoftheheadings.Asthecoalisbeingcutanddroppedontoachainconveyor,temporaryhydraulic-poweredroofsupportsautomaticallyfollowthedirectionoftheshearertoholduptheroofwhilethecoalisbeingextracted.Thesesupportsprovideasafeworkingenvironment,andasthemineadvances,sodothesupportjacks,andtheroofareabehindthefaceisallowedtosafelycollapse,forminganareaknownasthegoaf.Inthemainroadwayswithinthemine,forusebyminepersonnel,transportationofmaintenanceequipment,etc.roofboltsareplacedintheceilingtoavoidcollapse.Oncetheshearerhascompletedextractingthecoalfromthepanel,itismovedtoanewlocation,andrepeatstheprocess.Thismethodofminingismoreefficientthantheroomandpillarmethod,withrecoveryratesaveragingapproximately75%.However,theequipmentismoreexpensiveandcannotbeusedinallgroundconditions.Theseissues,amongothers,willbediscussedfurtherbelow.Asmentionedatthebeginningofthissection,longwallminingisthepredominantundergroundmethodofextractingcoalwithinAustralia,withapproximately70%ofundergroundcoalminesutilisingthetechnique,allofwhichareineitherNewSouthWalesorQueensland.Themethodaccountsfor89%ofAustralia’stotalundergroundcoalproduction(UniversityofWollongong2006).ItisarelativelyrecentintroductioninAustralia,withthefirstlongwallminebeingdevelopedin1963,however,therearecurrently27inoperationincludingtheBeltana,MetropolitanandNewstancoalminesinNewSouthWales,andtheCrinium,Kestrel,OakyNorthandNewlandsSouthernmineswithinQueensland.Kelly(1999)identifiedthefactthatshearfailure,ratherthantensile,isthemajorfailuremechanisminanumberofAustralianlongwallminesmonitoredbytheCSIROsince1994.Thefailurehasoccurredfurtheraheadoftheretreatingfacethantraditionalgeo-mechanicstheorypredictsandisconsiderablyaffectedbythegeologicalconditionsofthesite.Otherfactorsinfluencingfailureincludegoafingmechanicsofpreviousblockandporewaterpressure.Hebblewhite(2003)introducedtheconceptofcoregeotechnicalrisksassociatedwithlongwallmining,thatis:‘‘anyriskassociatedwithamajorhazardorpotentialhazardthatisaninherentfeatureofagenericminingmethod.Almostbydefinition,coreriskscannotbetotallyeliminated,andmustthereforebecontrolledandmanagedduringthelifeoftheminingmethodorsystemofwork’’.Thepaperidentifiedsomemajorcoregeotechnicalrisksassociatedwithlongwallmining,andcanbeseeninTable2.Table2CoregeotechnicalrisksassociatedwithlongwallminingHazardConsequenceSurfacesubsidenceDisturbance/damagetosurfacefeatures(naturalandman-made),andtosub-surface,suchasaquifers.Faceinstability/periodicweightingLossofface/roofcontrol;productiondisruption;equipmentdamage;operatorsafetythreatenedCavinghangupWindblasts(rangeofconsequentsafetyimplications);excessivepillarandfaceloading;unpredictablesubsidenceStructuralgeologydisruptiontopanelblocksProductiondisruptionandpotentialsterilisationofreservesleadingtomajoreconomicimpact;adversefacegroundconditionsAbutmentstressesondevelopmentAdverseconditions/potentialfailureingateroadsandchainpillarsRisksidentifiedwithinTable2suchassurfacesubsidenceareinevitableandwilloccuronalmostalllongwallminesites,andmustbemanagedeffectively,whilstotherssuchascavinghangupcausingair/windblastsareavoidableifappropriateplanningisundertakenandprecautionsfollowed.Certainly,thegeotechnicalsuitability,issuesandrisksmentionedhereinarenotinanywaythesoleelementstoconsiderwhenplanning,developingoroperatinglongwallmines.Itissimplyanidentificationanddescriptionofmajorfactorsinvolvedwithinthelongwallminingprocess.Otherissuesandbusinessconsiderationsfollowing,relevanttospecificsites,shouldalsobetakenintoaccountwhenconsideringcoalminingmethods.OtherissuesandconsiderationsTheprevioussectiondescribesgeotechnicalconsiderationsrelevanttolongwallmining.Thefollowingsectionwillconsiderotherissueswhichmayariseduringlongwalloperationsincludingsafety,production,productivity,equipmentsize,make,etc.andoptionsforminelayout.Aseachsiteisindependentofanother,itisdifficulttorecommendcertain‘templates’forselectingtheminingmethod,however,itistheaimofthissectiontodiscusswhatoptionsareavailableandunderwhatconditionstheyarebestsuitedfor,aswellascommonissuesarisingduringtheapplicationofaparticularmethod.Theimportanceofproductivityinallminingcannotbeoverlooked,andthemainincreasesovertheyearshavegenerallycomefromadvancementsintechnology.Oneofthekeyfactorsoverthepast20yearsinmakinglongwallproductivitygainshasbeentheevolutionoflargerlongwallpanels,madepossiblebytechnologyadvancements,upwardsof3,350minlengthby320mwideasopposedtotypicallengthsandwidthsinthemid-1980sof1,525and180m,respectively(KvitkovichandWeisdack2005).Itisexpectedthatlongwalltechnologywillcontinuetoimproveforanumberofyears,thusprovidinggreateroptionsforlongwallunitselection,whichultimatelyhasagreatinfluenceonproductivity(PengandChiang1984).In1992forinstance,longwallequipmentwasverydiverseinsizeandcapacity,asitstillistoday,withshearerpowerrangingfrom150to1,080kW,andfaceconveyorcapacityrunningbetween940and2,600tonnes/h.Thesestatisticsdemonstratethevariousoptionsavailablewhenpurchasinglongwallequipment,whichwillultimatelyhavealargeinfluenceonthecostsandexpectedproductivityofaproject.TasmanAsiaPacific(Anon1998)conductedananalysisonlongwallminingin1998bycomparingbestpracticeperforminglongwallminesintheUSAwithanumberoflongwallminesoperatingwithinAustralia.ThisanalysisconcludedthattheaverageproductivityoftheAustralianmineswasapproximately25%lessthanthatoftheUSAmines.Theanalysiswaslimitedtothecoreminingoperationsoflongwalls(shearing,roofsupport,transportationofthecoal,labourandmaintenance)andtherefore,becausetheoperatingcharacteristicsofthemineswerefairlysimilar,estimatedproductivitygapslikelyindicateddifferencesinmanagementandworkpractices.Theresultsfromthisreportindicateareaswhichtypicallyaffectproductivityinlongwallmines.ThereportidentifiedthemajordifferencesbetweentheAustralianandUSAlongwallminesas:•higher‘non-production’timesduringshiftchangeoverwithinAustralianlongwallmines,•lowerutilisationofshearerswithinAustralianlongwallmines,andgeologicaldifferences.Theseresultsindicatekeyareaswhich,iffocuseduponandmanagedappropriately,caninfluenceproductivitylevelswithinlongwallmines.AscanbeseenfromFig.3,Australianmineshadmuchmore‘‘non-production’’,or‘‘joiningandleaving’’,timethantheUSAmines.Itwasnotedthatthe‘‘distancetravelledbyemployeesfromsurfaceaccesspointtominefacewasverysimilarbetweentheaverageparticipatingUnitedStatesandAustralianmines.So,largedifferenceinjoiningandleavingtimecannotbeexplainedbytraveltime’’(Anon1998).Itwassuggestedthatthemaincauseofthisdifferencewaseitherdifferentworkpracticeoremployeetransportationsystem.Thedifferenceinthese‘‘non-production’’timesresultedin40minutesextraproductivitypershiftfortheUSAmines,provingthatwhatmayseemasmalloralmostinsignificantfactorcanhavealargebearingontheoverallsuccessfulnessofalongwallmine.Fig.3‘Non-production’timeinshiftsatlongwallmines(%oftotalshifttime)(Anon1998)Anothermajordifference(seeFig.4)statedfromthereportwasalowerutilisationofshearersinAustralianlongwallmines.Fig.4Utilisationandavailabilityofshearers(Anon1998)Thisutilisationdifferencewasmainlyattributedtomineplanning,andagaindemonstratesamajorissuetoconsiderinordertomaximisetheproductionofalongwallmine.Thesemajorfactorsmentioned,obviouslyalongwithsomeotherminorfactors,identifyissuestoconsiderwhendevelopingoroperatinglongwallmines.Thisofcoursedoesnotincludeindividualgeologicalconditionsorequipmentselection.Figure5showswhateffecttheseissuescanhaveoncostpertonneiftheyarenotmanagedproperly.Fig.5Totalfactorproductivityandcostpertonneforlongwallmines(index,USAcoal=100,cost$A)(Anon1998)Whencomparinglongwallminingtotheothermajorundergroundmethod,roomandpillar,itisinterestingtonotethat,atleastintheUSA,higherlabourproductivitylevelsareobtainedutilisingthelongwallmethod(Darmstadter1997).Thisisduetoanumberoffactors.First,longwallminingismuchlesslabourintensivethanroomandpillarmining,whichislargelyduetothefactthatthelongwalloperationisofahighlymechanisednature,wherethereisasignificantdegreeofcomputerisationandcontinuityintheextractionprocess.Thisminimallabourintensivefactoralsohasasecondaddedbonus,thatis,superiorsafetyperformanceisgenerallyachievedduetolesspersonnelatthecuttingface.Secondly,longwallminingutilisesacontinuouslyhaulingconveyorsystem,whereastheroomandpillarmethodemploysasomewhatmorelabourintensiveshuttlecarsysteminconjunctionwithcontinuousminers.Thischaracteristicisanimportantaspectofundergroundminingtechniquestoconsider,particularlywhenonelooksattheoutcomeofa1995studyintheUSAcomparingtheratiooflongwalltoroomandpillarlabourproductivitylevelsthroughoutvariousstatesandregions,asshowninTable3below.Table3Ratiooflongwalltoroomandpillarlabourproductivitylevels,selectedstatesandregions1983–1993(Darmstadter1997)19831993Alabama1.061.33EastKentucky0.851.35Pennsylvania0.911.62Virginia0.731.01WestVirginia1.140.97Illinois1.251.12WestKentucky-0.75Colorado0.841.54Appalachia0.981.10IllinoisBasin1.191.00West1.111.51US0.981.19Source:EIA1995b,pp.39–40(WestKentuckyhadnolongwallproductionin1983)Asshownfromthis,anoverallratioofalmost1.2infavouroflongwallminingsuggeststhismethodwillgenerallyobtainhigherlabourproductivitylevelsasopposedtoroomandpillar.RoomandpillarminingConventionalroomandpillarminingwasthetraditionaltechniqueusedduringundergroundminingupuntilapproximately40yearsago,whencontinuousminingwasintroducedintoAustralia.Thisnewformofroomandpillarminingeliminatedtheneedfordrillingandblasting,andwasamuchmoreefficientprocess,andassuch,practicallyreplacedtheconventionalroomandpillarmethod.Althoughcontinuousroomandpillarminingisthemostcommontypeofundergroundminingintheworld,itplayssecondfiddletothemoreeconomiclongwallmininginAustralia,withapproximatelytwiceasmanyundergroundminesutilizingthismethodasopposedtoroomandpillar(ABS2006).Incontinuousroomandpillarmining,coalseamsareminedbyacontinuousminer,whichisanelectricmachinethatbreaksthecoalmechanically.Itsmaincomponentisalongrotatingdrumwhichhassharppicksattachedaroundtheoutside,andallowsthemachinetocutandloadthecoalatthesametime.Thecoalisthenloadedontoshuttlecarsand/orconveyorbeltswhereitistransportedtothesurface.Thecontinuousminerworksinsuchawaythatitcutsaseriesof‘rooms’intothecoalseam,andleaves‘pillars’madeupofcoal(roofboltsarealsoaddedlater)tosupporttheroofofthemineasthemachineadvances,hencethename‘roomandpillar’.Asthecontinuousminermovesdeeperintothecoalseam,eachroomrequiresapillarofgreaterwidthtomaintainthesupportofthemine.Carefulplanningisnecessaryduringthisstageofminingtoensurepillarsofsufficientstrengtharedesignedtosu