本科生畢業(yè)設(shè)計（論文）題目：祁東煤礦2.4Mt/a新井設(shè)計煤與瓦斯突出煤層的開采技術(shù)摘要本設(shè)計包括三個部分：一般部分、專題部分和翻譯部分。一般部分為祁東煤礦2.4Mt/a新井設(shè)計。祁東煤礦位于安徽省宿州市境內(nèi)，交通便利。井田走向（東西）長約9km，傾向（南北）長約3km，總面積為27km2。主采煤層為61、71煤，煤層傾角平均14°，平均總厚度為10m。井田地質(zhì)條件較為簡單。井田工業(yè)儲量為313.16Mt，可采儲量為238.10Mt。礦井設(shè)計生產(chǎn)能力為2.4Mt/a。礦井服務(wù)年限為70.8a，涌水量不大，礦井正常涌水量為437.06m3/h，最大涌水量為586.10m3/h。礦井瓦斯相對涌出量為20m3/t，絕對涌出量為20m3/min，為高瓦斯礦井。井田開拓方式為立井兩水平上山開拓，二水平采用暗斜井延深。采用膠帶輸送機(jī)運煤，采用礦車進(jìn)行輔助運輸。礦井通風(fēng)方式為兩翼對角式通風(fēng)。全礦采用采區(qū)準(zhǔn)備方式，共劃分為四個工作面，并進(jìn)行了運煤、通風(fēng)、運料、排矸、供電系統(tǒng)設(shè)計。針對61201工作面進(jìn)行了采煤工藝設(shè)計。該工作面煤層平均厚度為7.0m，平均傾角15°。工作面采用綜采放頂煤采煤法。采用雙滾筒采煤機(jī)割煤，往返一次割兩刀。采用“四六制”工作制度，截深0.8m，每天六個循環(huán)，循環(huán)進(jìn)尺0.8m，月推進(jìn)度144m。一般部分共包括10章：1、礦區(qū)概述與地質(zhì)特征；2、井田境界和儲量；3、礦井工作制度、設(shè)計生產(chǎn)能力及服務(wù)年限；4、井田開拓；5、采區(qū)巷道布置；6、采煤方法；7、井下運輸；8、礦井提升；9、礦井通風(fēng)與安全；10、設(shè)計礦井基本技術(shù)經(jīng)濟(jì)指標(biāo)。專題部分題目是煤與瓦斯突出煤層的開采技術(shù)，主要是介紹了煤與瓦斯突出煤層的瓦斯抽放原理和卸壓措施，全面闡述了煤與瓦斯突出煤層的瓦斯抽放、煤與瓦斯共采技術(shù)。翻譯部分主要內(nèi)容是關(guān)于澳大利亞兩大地下開采方法——壁式、房柱式采煤法的介紹，英文題目為：GeologicalandgeotechnicalaspectsofundergroundcoalminingmethodswithinAustralia。關(guān)鍵詞：立井；暗斜井延深；兩水平；采區(qū)布置；兩翼對角式通風(fēng)；綜合機(jī)械化放頂煤采煤方法

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第頁英文原文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:‘‘a(chǎn)nyriskassociatedwithamajorhazardorpotentialhazardthatisaninherentfeatureofagenericminingmethod.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