葛亭煤矿1.5Mt-a新井设计-大采高综采技术研究

目录一般部分1矿区概述及井田地质特征 页Investigationsofwaterinrushesfromaquifersundercoalseams（JincaiZhang）Abstract：Inmanycoalmines,limestone-confinedaquifersunderliecoalseams.Duringcoalextractionfromthesemines,waterinrushesoccurfrequentlywithdisastrousconsequences.Thispaperintroducesthehydrogeologicalconditionsofthecoalminesandthepotentialwaterinrushdisastersfromaquifersundercoalseams.Itthenpresentsthewaterinrushmechanism.Themainfactorswhichcontrolwaterinrushesincludestratapressure,miningsize,geologicstructuresandthewaterpressureintheunderlyingaquifer.Analysisshowsthatreductionofconfinementduetominingisthemajorcauseofthewater-conductingfailureinthefloorstrata.Thedepthofthefailurezoneisstronglydependentontheminingwidth.Thispaperalsopresentsfieldobservationresultsofthewater-conductingfailureinthefloorstrata,andappliesthefiniteelementmethodcoupledwithstress-dependentpermeabilitytoanalyzehydraulicconductivityenhancementduetocoalextraction.Finally,theoreticalandempiricalmethodstopredictwaterinrushesaregiven,andtechnicalmeasuresforimprovingminedesignandsafetyforcoalextractionoveraquifersarepresented.Thesemeasuresincludefaultandfracturegroutingandminingmethodmodificationsuchaschanginglong-walltoshort-wallMining.Keywords:Waterinrush;Coalmining;Confinedaquifer;Stratafailure;Stressanddisplacement;Hydraulicconductivity;Permeability1IntroductionChinacontinuestorelyoncoalforabout75percentofitsenergy.Therefore,coalproductionisofcrucialimportanceforChina’seconomyanddevelopment.However,miningoperationsinChinaarethreatenedbyvariouskindsofgroundwaterduringcoalextractions.Themostseriousofthethreemaintypesofpossiblewaterdisastersaffectingthesafeoperationofcoalmines[1]iswaterinrushesfromtheOrdovicianlimestoneunderthepermo-CarboniferouscoalseamsinNorthernChina.TheOrdovicianlimestoneisaconfinedkarstaquifercontaininganabundantsupplyofwaterandwithaveryhighwaterpressure.Furthermore,thestratabetweencoalseamsandtheaquiferarerelativelythin,varyinginthicknessfrom30to60m.Duetothesecharacteristicsoftheaquifer,plusmining-inducedstratafailureandinherentgeologicalstructures(suchaswater-conductingfaults,fractures)high-pressuregroundwatercanbreakthroughseamfloorsandburstintominingworkings.Therefore,waterinrushesfromtheaquiferoccurfrequently,andcoalminesoftensufferfromseriouswaterdisastersduringcoalextractions.Waterinrushincidentshaveshownthatthemaximumwaterinflowinacoalminehasreachedasmuchas2053m³/min[2],whichsubmergedthemineinaveryshorttime.Accordingtoincompleteofficialstatistics,about285of600keycoalminesinChinaarethreatenedbywaterinrushesduringcoalmining[2].Thetotalcoalreservesthreatenedbybodiesofwaterareestimatedat25billiontons.Forexample,inNorthernChina,theyearlycoalproductionfromthePermo-Carboniferouscoal-bearingformationsismorethan200milliontons.However,thecoalextractionhasbeenthreatenedbyfrequentwaterinrushesfromtheOrdovicianaquifer.Inthisregion,thelowerlevelseamswhichhavemorethanhalfofthetotalcoalreservesaremuchmoredifficulttomineduetothisthreatofwaterinrushes(Table1).From1950to1990,atotalof222seriouswaterinrushincidentstookplaceinChinacausingcollieriestobesubmergedbywaterintrusionsfromtheconfinedkarstaquifers.Morerecently,totalwaterinrushesatnationalizedkeycoalminesoccurabout125timesannuallyresultinginaneconomiclossof1.5billionYuan(about180millionUSdollars).Inaddition,localcoalminesrunbyprovinces,counties,andprivatebusinesshavealargerannualeconomiclossinducedbywaterinrushes.ThemaincoalfieldsthreatenedbytheOrdovicianaquiferareJiaozhuoinHenanProvince,Fengfeng,HandanandXingtaiinHebeiProvince,ZiboandFeichenginShandongProvince,andHanchengandChengheinShaanxiProvince.Iftheproblemsofsafeminingovertheaquifercannotbesolvedefficiently,somecoalminesinthementionedcoalfieldswillbefacedwithgradualreductionofproductionorevenabandonmentofthemines.Ingeneral,therearetwodifferentwaysofsolvingtheproblemsofminingoverconfinedaquifers.Oneistodraintheaquiferbeforeminingoperation,andtheotheristominewithoutdrainage.Geologicalinvestigationandminingpracticehaveunveiledthattherearemanyenvironmentalproblemsinducedbywaterdrainagefromlimestoneaquifers,suchastheOrdovicianlimestoneaquiferinNorthernChinaandtheMaokuolimestoneaquiferinSouthernChina.Fissuresinthesekarstifiedlimestonesarewelldevelopedandinterconnectedwithintheaquifersuchthatwhenwaterisdrainedfromoneparticularregion,ithasanextensiveinfluenceonthewholeaquifer.Forexample,dewateringintheOrdovicianlimestoneaquiferwasconductedinWangfencolliery,HebeiProvince.Thepumpingflowratewas96m³/min;however,thedrawdowninthecentralwellwasonly2Determinationofthewater-conductingfailurezoneintheseamfloor2.1InCoalextractioncausesstratadeformationandfailurewhichmayenhancehydraulicconductivityinthesurroundingstrata.Therefore,itisdesirabletoaccuratelydeterminepre-andpost-mininghydraulicconductivitiesintheoverburdenandunderlyingstrataofthecoalseam.Tomeasuretheconductivityintheunderlyingstrata,boreholesaredrilledpre-mininginundergroundroadwaysforobservation.Ineachborehole,waterinjectionandanumberofwellloggingtechniques(suchaselectricresistivity,ultrasonicwave,acousticemission,holeteleviewer,etc.)areusedtodeterminerockstrength,boreholefissure,andchangesinhydraulicconductivity.Fig.1givesaschematicdiagramofawaterinjectioninstrument[16].Thekeytechniqueduringmeasurementsistocontroltheinjectionpressure.Thepressureshouldnotbehighenoughtocreatenewfracturesinthestrata,sincetheexperimentisconductedtodeterminethechangesinhydraulicconductivityinducedbymining.Therefore,theinjectionpressureshouldnotexceedtheleastprincipalstressofthesurroundingstrata.Fig.2showstheobservedboreholelocationsofandlayoutinXingtaicoalmine.Inthisarea,insitustresseswereasfollows:.TheroadwayinFig.2waslocated36mbelowtheminingfaceandfourboreholesweredrilledatdifferentangles.ThewaterinjectioninstrumentdescribedinFig.1wasappliedtomeasuretheflowrateofwaterinjectionpreandpost-mining,usinganinjectionpressureof0.35–0.5MPa.Thewaterinjectionalongeachboreholewasconductedbypumpingwaterintotheinstrument,andthenintotheborehole.Themeasurementsweretakenineachholeatdifferentsectionsthroughouttheboreholeandatdifferenttimes.Fig.1.TheinstrumentationforwaterinjectionobservationinaboreholeFig.2.ObservingboreholelayoutforwaterinjectionmeasurementsinXingtaicoalmine,HebeiProvince.Fig.3.Flowrateofwaterinjectionalongaborehole(Hole1inFig.2)pre-andpost-mininginXingtaicoalmine,HebeiFig.3givesthemeasuredpre-miningandpost-miningflowrateofwaterinjectioninHole1(refertoFig.2).Notethatinthiscontextpre-miningcorrespondstoastatebeforetheminingfacepassestheborehole,andpost-miningmeansaftertheminingfacepassestheborehole.ItcanbeseenthatbeforetheminingfacepassedHole1(inpre-mining,theminingfacewas32mawayfromtheborehole),theinjectionratewaszerofrom53to68mintheinclinedborehole.Thismeansthatthestratainthisareawereimpermeable.However,whentheminingfacepassedtheborehole,theinjectionrate(refertoFig.3forpost-miningat19and63m)increaseddramatically,andthestratainsomeareaschangedfrombeingimpermeabletopermeable.Sincetheboreholewallcollapsedbyminingwhentheminingfacepassed63mfromtheborehole,waterinjectiondatacouldnotbeobtainedafter60mfromtheboreholeopening.Theboreholecollapsepost-miningillustratesthattheboreholewasseriouslydamaged,andthatrocksaroundtheboreholefailedduetomining.Fig.4plotstheincrementsofwaterinjectionratesaftermining,whichwereobtainedbysubtractingthepre-mininginjectionratesfromthoseofthepost-mining.Theseincrementsrepresentinjectionratescausedbypermeabilitychangesinducedbycoalextraction.ItcanbeseenfromFig.4thatalongtheinclinedboreholefrom43to72m(theboreholeend),theinjectionrateincreasedcomparedtothepre-mining(insitu)state.Therefore,thestratainthisareawerefissuredbymining,andthisareaisdefinedasthewater-conductingfailurezone.Usingthesamemethodtoanalyzetheobserveddatafromallboreholes,themining-inducedwater-conductingfailurezonecanbeobtained.Thisfailurezoneisofcriticalimportanceforminedesignandwaterinrushpreventionforminingoveraquifers.Fig.4Flowrateincrementofwaterinjectionalongaborehole(Hole1inFig.2)aftermininginXingtaicoalmine,Fig.5displaysthechangesoftheinjectionrateswiththedistanceofminingadvancefortwodifferentdepthsbeneaththecoalseaminWangfencoalmine,HebeiProvinceFig.5Flowrateofwaterinjectionversusminingdistancefortwodifferentdepthsbeneathcoalseam(thenegativedistancerepresentspre-miningstateandthepositivemeanspost-miningstate).Fig.6Observingboreholelayoutandobservationsectionofthewater-conductingfailurezoneintheunderlyingstrataforslightlyinclinedcoalseaminFengfengcoalmines,HebeiFig.7Observingboreholelayoutandobservationsectionofthewater-conductingfailurezoneintheunderlyingstrataforinclinedcoalseaminHuainancoalmines,AnhuiFieldobservationshaveshownthatcharacteristicsoffailuresinthefloorstrataareconsiderablydifferentfordifferentinclinationsoftheextractedseams.Forflatorslightlyinclinedseams(inclinationangle,α<25°),theprofileofthewater-conductingfailurezoneisbroadinsectionwithextendedlobes,andthemaximumfailuredepthoccursbeneaththeheadgateandtailgate,respectively,showninFig.6.Forinclinedseams(25°<α<60°),thefailurezonepropagatesdownwardsinanasymmetricmannerinthedipdirection,asshowninFig.7.Theextentofthefailurezoneincreasesgraduallyfromupdiptodowndip,andthemaximumfailuredepthappearsinthefloorstratabeneaththeareaaroundthelowergate.Forsteeplyinclinedseams(60°<α<90°),thefailurezonesinthefloorstrataareoppositetotheinclinedseams,i.e.,themaximumfailuredepthappearsinthestratabeneaththeareaaroundtheuppergate.3Empiricalpredictionofthedepthofthewater-conductingfailurezoneAccordingtoinsituobservations,anumberofparametersaffectthedevelopmentanddepthofthewater-conductingfailurezone.Miningwidthoftheworkingfaceanduniaxialcompressivestrengthofthestrataarethemostimportantofallparameters.Anempiricalformulaforpredictingthedepthofthewater-conductingfailurezonewasdevelopedfromfieldtestresultsinlong-wallandshort-wallminingfaces.Theformulaisexpressedas(refertoFig.8)（1）whereh1isthedepthofthewater-conductingfailurezonestartingfromtheimmediateflooroftheseam(m)andLxistheminingwidthoftheminingface(m).NotethattheobserveddatawereobtainedfromcoalminesinNorthernChina,withminingdepthsrangingfrom103to560m,anduniaxialcompressivestrengthsfrom20to40MPa.Forminingaboveaquifers,itisdesirabletoavoidwaterinrushesandtheextraexpenseofstratadewatering.Thiscanbeachievedonlywhenaquifersarelocatedacertaindistanceoutsidethewater-conductingfailurezone.Ifanaquiferwhichisconfined,verypermeableandwithabundantwaterlieswithinthefailurezone,waterwithhighpressurewillrushintotheminingarea,andmaycauseadisastrousconsequence.Fig.8Observedmaximumdepthofthewater-conductingfailurezoneintheseamfloorstratafordifferentminingwidthsinChina.4ConclusionsInsitumeasurementsandphysicalmodelinghaveshownthatstressincreasesandabutmentpressureisinducedintheseamfloorjustbeforetheminingfaceisreached.Thiscausescompressivedeformationandadecreaseinthewaterinjectionrate.Aftermining,stressdecreasesandstressrelaxationandconfinementreductionareinduced,causingexpansiondeformationandawaterinjectionrateincreaseinthefloor.Essentially,asminingadvances,developmentofstressinthefloorstrataincludesthreestages:stressincreasepre-mining,stressdecreasepost-mining,andagradualrecoverytotheoriginalstress.Correspondingtothestressredistribution,displacementinthefloorstratashowscompressionbeforemining,expansionaftermining,andgradualrecoverytotheoriginalstate.Duringthefloorexpansionandthestressrelaxationstage,thestrataaremorepronetocreatingtensilefractures.Intheareaoftransitionbetweenfloorcompressionandexpansionlocatedbeneaththeareaaroundthecoalwallofminingface,thestrataarelikelytocreateshearfractures.Therefore,thefloorfailurezoneisthelargestinthestratarightbeneaththeareaaroundthecoalwall,wherewaterinrushismostlikelytotakeplace.Statisticaldatahaveshownthatmostwaterinrushesfromtheunderlyingaquiferswererelatedtofaults.Therefore,itisofcrucialimportancetodetectandmapgeologicalstructuresindetailbeforemining.Also,sincethemechanismofwaterinrushesfromfaultshasnotbeenfullyunderstood,furtherstudy,includinginsitumonitoringoffaults,needstobeundertaken.Sincemorethan60%ofwaterinrusheswereascribedinsomewaytofaultsandothergeologicstructures,necessarymeasuresareneededtoaddressfaultsandinherentfracturesinthefloorbeforeminingoperationsbegin.Forlargefaults,water-proofingbarriersneedtobeleft.Forsmallfaultsandfractures,groutingcansealthemandreducethepossibilityofwaterinrushes.Forweakaquifersexistingintheseamfloor,groutingcannotonlychangetheweakaquiferintoanimpermeablelayerbutalsoincreasethestrengthofthefloorstrata,whichcanreducemining-inducedfailures.References[1]ZhangJ,ZhangY,LiuT.Rockmasspermeabilityandcoalminewaterinrush.Beijing:GeologicalPublicationHouse;1997[inChinese].[2]ZiboMiningBureau.DataanalysesandapplicationofcoalseamwaterinrushesinZibocoalfield.ZiboCoalSciTech1979;[inChinese].[3]HuainanMiningBureau,Xi’anBranchofChinaCoalResearchInstitute.Hydrogeologicalconditionsandcontrolmethodsofthekarstaquiferunder#AcoalseaminHuainancoalfield.Internalresearchreport,1983[inChinese].[4]FengfengMiningBureau,ShangdongUniversityofScienceandTechnology.InsitumeasurementofthefloorstratafailureintheNo.2coalmineofFengfengcoalfield.Internalresearchreport,1985[inChinese].[5]Wang,Z.Preliminarystudyofwaterinrushesfromthefloorofcoalminingfaces.CoalGeologyandExploration1983;(5)[inChinese].[6]Wang,Y.Conditionsandpreventionofwaterinrushesfromunderlyingconfinedaquifersofcoalseams.CoalSciTech1985;(1)[inChinese].煤层下含水层突水机理研究摘要：在许多煤矿，煤层下都存在石灰岩承压含水层。这些煤矿进行煤炭开采时，突水频频发生，造成灾难性的后果。本文介绍了煤矿的水文地质条件和煤层下含水层潜在的突水灾害。然后给出了突水机理。导致突水的主要因素包括地层压力，开采规模，地质结构和下含水层水的压力。分析表明，采矿使用限制减少是底板岩层水导电失败的主要原因。失效区的深度主要决定于开采宽度。本文还介绍了底板岩层中水承压失效的现场观测结果，并应用有限元法和应力渗透性的依从质来分析由于煤炭开采使渗透系数提高的原因。最后，给出了预测突水的理论和实证方法，并提出了含水层上煤炭开采矿井设计和安全的改进技术措施。这些措施包括断层和裂缝灌浆及采矿方法的改进，如改长壁开采为短壁开采。关键词：突水；煤炭开采；承压含水层；岩层破坏；应力和位移；水力传导系数;渗透率1引言中国能源的约百分之七十五将继续依赖煤炭。因此，煤炭生产对中国经济的发展至关重要。然而，在煤炭开采过程中，中国采矿生产受到地下水的各种威胁。影响煤矿生产安全运行的可能水灾害三种主要类型中最严重的是中国北部石炭二叠系煤层下奥陶系石灰岩突水。奥陶系石灰岩有一个高水压并有丰富的水源供给的密闭岩溶含水层。此外，煤层和含水层之间的地层相对较薄，厚度在30米至60米范围内变化。由于含水层的这些特点，再加上采矿诱发岩层破坏和固有的地质构造（例如水导电断层，裂缝）高压地下水可以通过缝地板和冲入开采生产区。因此，含水层突水频繁，煤矿常常在煤炭开采过程中遭受严重水害。突水事件表明，一个煤矿的最大涌水量高达2053m³/min据不完全的官方统计，中国600个重点煤矿中约有285在煤炭开采过程中受到突水的威胁。受到水体威胁的煤炭总储量估计在25亿吨。例如，在中国北部，从石炭二叠系含煤地层中每年生产煤炭超过200万吨。在这个区域，超过煤炭总储量一半由于这种突水（表1）的威胁开采要困难得多。从1950年到1990年，在中国发生222个严重的突水事故，密闭岩溶含水层的突水导致煤矿被淹没。最近，国有重点煤矿每年共发生突水约125次，造成经济损失15亿元（约1.8亿美元）。此外，省，县，民营企业经营的地方煤矿每年由于突水导致的经济损失更大。受奥陶系含水层威胁的主要煤田是河南焦作，河北峰峰、邯郸、邢台，山东淄博、肥城，和陕西韩城、澄合。如果关于含水层的安全开采问题不能有效解决，在上述煤田的一些煤矿将面临着产量减少，甚至关闭煤矿的问题。一般来说，解决煤矿开采承压含水层问题有两种不同的方法。其一是开采前进行含水层排水，另一种是不带排水渠的开采。地质调查和矿业实践已经表明，有许多因石灰岩含水层排水引起的环境问题，如中国北部奥陶系灰岩含水层排水，和在中国南部的茅口石灰岩含水层排水。石灰岩岩溶裂隙和含水层之间的这种相互联系，使得当从一个特定的区域排水时，它对整个含水层有广泛的影响。例如，在河北省王坟煤矿对奥陶系灰岩含水层进行了排水。该泵流量为96m³/min，但是，在中央井地下水位的降低只有2.8米，该漏斗降落半径扩展到10公里，造成了许多饮用水井的损失。这导致100000人供水短缺。因此，排水是不可行的。石灰岩含水层之上的煤炭开采的唯一的解决办法是利用技术措施，不进行排水进行开采。为了做到这一点，研究岩层破坏特性及由于采矿水力传导的变化是至关重要的，然后找到一个方法来预测和防止突水。虽然已进行过这方面的各种研究，但对突的机制仍然没有得到很好的表1在中国的煤矿受奥陶系含水层威胁的煤炭储量2煤层底板下水承压失效区的测定2.1钻孔原位观测水承压失效煤炭开采引起的地层变形和破坏可能提高周围地层的渗透系数。因此，最好是准确确定开采前后在煤层上覆和下伏地层的渗透系数。为了测量下伏地层中的渗透系数，钻孔都在井下巷道开采前打钻以便观察。在每一个钻孔，大量的注水和测井技术（如电阻率，超声波，声发射，孔成像等）用于确定岩石强度，钻孔裂隙和水渗透系数的变化。图1给出了一个注水仪器原理图。在测量过程中的关键技术是控制注入压力。进行实验以确定开采引起的渗透系数的变化，压力不应该高到足以制造新的地层裂缝。因此，注入压力不应超过周围地层的最小主应力。图1钻孔注水观测仪器图2河北省邢台煤矿注水测量钻孔布局图2显示了邢台煤矿钻孔位置布局。在这一区域，应力如下：。图2中的巷道位于采煤工作面的下方36米，并且四个钻孔分别钻在了不同的角度。图1描述的注水仪器利用0.35MPa到0.5MPa注射压力来测量开采前后水注入的流量。沿每个钻孔注水由抽进仪器的水来控制，然后流入钻孔。该测量结果是由不同地区和不同时间的每个钻孔内得出的。图3给出了测量开采前后注入孔1的水流量（参考图2）。请注意，在这种情况下开采前对应一个采煤工作面通过钻孔之前的状态，开采后则对应采煤工作面通过钻孔后的状态。可以看出，通过开采工作面通过孔1之前（开采前，采煤工作面离钻孔32米远），倾斜的钻孔从53至68米的范围内注入率是零。这意味着，在这区域的地层防渗。然而，当工作面通过钻孔，注入率（采后在19至63米参考图3）急剧增加，而且在某些地区被不透水地层向透水性转变。由于采煤工作面通过钻孔63米时井壁坍塌，注水数据无法从60米之后的钻孔获得。采后的井壁坍塌说明，由于采矿钻孔被严重破坏，而且图3河北省邢台煤矿开采前后沿钻孔（图2中的孔1）的注水流量图4河北省邢台煤矿开采后沿钻孔（图2中的孔1）增加的注水流量图4给出了开采后注水率增量，这是由从采后注入率减去的采前注入率得到的。这些增量表明由煤炭开采引