InternationalJournalofMi；InternationalJournalofMi；MuZonglonga,DouLinmingb,；Theruptureandmovementsco；LithologyofLW250103.Sequ；
InternationalJournalofMiningScienceandTechnology23(ContentslistsavailableatSciVerseScienceDirectInternationalJournalofMiningScienceandTechnologyjournalhomepage:/locate/ijmstF-structuremodelofoverlyingstratafordynamicdisasterpreventionincoalmineMuZonglonga,DouLinmingb,HeHuc,?,FanJunaaSchoolofMines,ChinaUniversityofMining&Technology,Xuzhou221116,ChinaStateKeyLaboratoryofCoalResourcesandMineSafety,ChinaUniversityofMining&Technology,Xuzhou221116,ChinacSchoolofResourceandEarthScience,ChinaUniversityofMining&Technology,Xuzhou221116,ChinabarticleinfoabstractTheruptureandmovementscopeofoverlyingstratauponthelongwallminingfaceincreasedsharplyastheexploitationscaleanddegreegrowingrecently,andthespatialstructureformedbyfracturedstratabecamemuchmorecomplex.Theoverlyingstrataabovetheworkingfaceandadjacentgobswouldaffecteachotherandmovecooperativelybecausesmallpillarcanhardlyseparatetheconnectionofoverlyingstratabetweentwoworkfaces,whichleadstominingseismicityinthegobandinducesrockburstdisasterthatnamedspatialstructureinstabilityrockburstinthispaper.Basedonthekeystratumtheory,theF-structuremodelwasestablishedtodescribetheoverlyingstratacharacteristicandrockburstmechanismofworkfacewithonesideofgobandtheothersideun-minedsolidcoalseam.TheresultsshowthatF-structureinthegobwillre-activeandlossstabilityunderthein?uenceofneighboringmining,andfractureandshearslippingintheprocessofinstabilityisthemechanismoftheseismicityinthegob.TheF-structurewasdividedintotwocategoriesthatshort-armFandlong-armFstructurebasedonthestateofstrataabovethegob.WestudiedtheundergroundpressurerulesofdifferentF-structureandinstabilitymechanism,thusprovidetheguideforpreventionandcontroloftheF-structurespatialinstabilityrockburst.Themicro-seismicsystemisusedforon-sitemonitoringandresearchingthedistributionrulesofseismicevents,theresultscon?rmedtheexistenceandcorrectofF-spatialstructure.AtlastspecializedmethodsforpreventionseismicityandrockburstinducedbyF-structureinstabilityareproposedandappliedinHuatingCoalMine.ó2013PublishedbyElsevierB.V.onbehalfofChinaUniversityofMining&Technology.Articlehistory:Received26November2012Receivedinrevisedform12December2012Accepted20January2013Availableonline23July2013Keywords:OverlyingstrataSpatialstructureDynamicdisasterKeystrataSeismicity1.IntroductionRecentyears,seriesofadvancedminingtechnologiessuchaslongwallminingwithtopcoalcaving,largeheightminingandsmallornonepillarbetweenadjacentworkfaceshavedevelopedconsiderablyinChinesecollieries,andlarge-scaleapplicationofthesetechnologieshavesigni?cantlypromotedtheareaandspeedoftheminingworkfaces[1C4].Withthesuccessfulcombinationofsmallornonepillarandtopcoalcavingtechnology,theruptureandmovementscopesofoverlyingstrataexceedtheordinaryworkfacegreatly,whichmakestheminingstress?eldandspatialstructureformofoverlyingstratamuchmorecomplex[5,6].Therupturedroofintheneighboringgobbecameunstableandacti-vatedagainunderthedisturbanceofminingactivitiesbecauseofnoprotectioncoalpillarbetweenthem.There-instabilityoftherupturedroofinthegobcaninduceseverelydynamicdisasterssuchasrockburstandcausecasualtiesandequipmentdamageintheworkingface,butlessattentionandresearchhavebeenpaid?Correspondingauthor.Tel.:+4.E-mailaddress:hehu_(H.He).tothiskindofminingtremorinthepast,inthispaperwegiveanameofthistypeasspatialstructureinstabilityrockburst.TherockburstandminingseismicityincollieriesshowanexplosiveincreaseinChina,andmorethan120mineshaverelatedreports,inwhichtheproportionofspatialstructuredinstabilitytypegrowsgradually[7C9].Soin-depthstudiesmustconductinordertorevealthemechanismandguiderationalpreventionsfortherock-burstinducedbythespatialstructureinstabilityoftheoverlyingstrataintheadjacentgob.Numerousresearcheshavebeendoneinthepasttoinvestigatetheroofbehavior,andgreatachievementshavebeenobtainedasthestratamovementandstressdistributionrelatedtominingactivitiesaremajorconcernsincoalscience[10C13].Themostimportantoutcomeisthe‘‘VoussoirBeam’’and‘‘keystrata’’theoryofroofproposedbyprofessorQian,academicianfromtheChineseAcademyofEngineering[14C18].Butwefoundthatmostofthepreviousstudiesofundergroundpressurerulescon?nedtoalimitedzonesofasingleworkface,themajorresearchobjectofstratacontrolconcernsonthemainroofnotfarfromthecoalseam.Neverthelessdynamicdisastershaveinvokedregionsmorethanonesingleworkface,whichhavebeenprovedbyin-situaccidents/$-seefrontmatteró2013PublishedbyElsevierB.V.onbehalfofChinaUniversityofMining&Technology.http://dx.doi.org/10.1016/j.ijmst.514Z.Muetal./InternationalJournalofMiningScienceandTechnology23(investigations.Howeverseismicitiesinadjacentgobsarelackofcorrespondingresearchesincludingthemechanismandlawsthatareofgreatmeaningforeffectivedisasterpreventionandweaken-ing.Inthispaper,anF-structuremodelofoverlyingstrataisputforwardofrevealingthemechanismofseismicitiesinadjacentgobinducedbyminingactivitiesduringfullymechanizedtopcoalcavinglongwallfacesexcavation.Coalmineseismicobservationsystem,madeinPolandalsocalledSOSforshort,whichmoreaccu-rateandinformation-richthanothertraditionalmethodswasuti-lizedtomonitorthebehaviorandvibrationoftheoverlyingstrataatthesametime.2.F-spatialstructuremodeloftheoverlyingstrataBasedonthe‘‘keystrata’’theoryweknowthatthemainroofistoforman‘‘OCX’’balancedstructureafterthecoalseamexcavated,asshowninFig.1,andonthepro?lealongtheadvanceandstrikedirectionoftheworkingface,thefracturedroofarticulatedwitheachotherandobtainedbalanceas‘‘VoussoirBeam’’.Inthepro-cessofmainroofrupture,movementandinstabilitywillcausestratabehaviors,sometimesmayinduceundergroundpressureaccidentsiftheroofwithhighstrengthandthickness[19,20].Thebalancedstructureontheboundariesoftheworkfacecanmaintainalongperiodtimewithoutanyotherminingdisturbance.Butifthenextworkingfaceisnearthegobandsmallornoprotec-tionpillarbetweeneachother,the‘‘VoussoirBeam’’structurewillbecomeboundaryconditionsofthenextworkface.Withthecoalextractionandroofmovement,theboundarystructurewillactivateandcave,soin?uencethestressdistributionandleadtominingtremors.Basedonthecharacteristicoftheoverlyingstrataboundaryconditions,weestablishF-structuremodelforthiskindofworkface.TheF-structuremodelcanbeclassi?edintotwocat-egories,longandshortarmF-structurecorrespondingtothesub-criticalextractionandfullsubsidenceofthegob,respectively.Fig.2showsthelong-armF-structure,ifthewidthofthegobistooshorttoexceedthelimitspanofonekeystratum,usuallymainkeystratumabovethecoalseam,itwillmaintainintactunlessthetotalwidthofthegobandnextworkfaceexceedsthelimitspan,themainkeystratumwillrupture.Fig.2aistheplandiagramofthefracturelineandFig.2bexhibitsthepro?lealoneACA.Fig.3showstheshort-armF-structuresketch,inthissituationthewidthofthegobismuchmorethanthecriticalextractionsizeandallkeystratafracturedandkeptastablestructure,thesubsidenceofthesurfacereachesmaximumthatallowedunderthespeci?cgeologiccondition.Fig.3aandbshowtheplansketchoffracturelineandpro?lesketchofoverlyingstrata,respectively.Thedifferencebe-tweenofthelong-armandshort-armisthatwhetherthemainkeystratarupturedandthiswillresultsindifferentstress?eldandstratabehaviors.ThecharacteristicofF-structuremodelisthatthestrataarm(shortoflong)willcoordinatelymovewiththeroofsinthenextworkingfaceunderminingactivitiesthereforinduceseismicitiesinthegobandimpactthegob-sideentry.TheF-struc-turemodelcontainstwotypesofstratamovement,theruptureandinstabilityoftheF-armsinthegobsideand‘‘OCX’’ruptureinmiddleandthesolidcoalseamside,soitismuchmorecomplexthansingleworkingface.3.MechanismoftheF-structureinstabilityandinducingseismicityThestabilityofthearmofF-structureandconnectedrockblocksespeciallyblockBasshowninFig.4asigni?cantlyaffectedAdvancing direction1234AA15(a) Planar graph of “O-X”rupture model
(b) A-Aprofile of “O-X”rupture modelFig.1.‘‘OCX’’modeland‘‘VoussoirBeam’’structureofkeystratainsingleworkface.1.C2.O-3.X-4.‘‘VoussoirBeam’’structureformed5.Gobafterthecoalexploitation.Main key stratum unbroken2(a) Profile of long-arm F-structure of overlyingstrata(b) Planof long-arm F-structure of overlyingstrataFig.2.Schematicdiagramoflong-armF-structuremodelofoverlyingstrata.1.Nextwork2.En3.Smallpilla4.Fract5.Fractur6.Fracturel7.Gobofpreviousdistrictsublevel.Z.Muetal./InternationalJournalofMiningScienceandTechnology23(5152Main key stratum broken4567123(a) Profile of short-arm F-structure of overlyingstrata(b) Plan of short-arm F-structure of overlyingstrataFig.3.Schematicdiagramofshort-armF-structuremodelofoverlyingstrata.1.Nextwork2.En3.Smallpilla4.Fract5.Fractur6.Fracturel7.Gobofpreviousdistrictsublevel.ofrotaryangle,howeverhorizontaldecreasesgraduallysincethehingeareabetweenAandBreducesand?nallyseparatesattheworstsituation.Sothestructureisinanunstableequilibriumthathardlytopreserve.Twokindoffocalmechanismexistduringstruc-tureinstability,rotaryastherotationangleexceedthelimitationbetweenAandBandshearslippingbetweenAandBaswellasBandC.Intheprocessofrotaryandslipapartofenergyreleasedseis-micwavewhichisthemechanismofseismicityinthegob.Astheroofshadalreadyfracturedtodifferentdegree,mimingseismicitiesfrequentlyunderminingactivitybytheinsitemonitoring.4.Insitumicro-seismicmonitoringofF-structuremodel(a)Relationship between rock blocks of the “Voussoir Beam”FFFShear slipBlock CSeismicity4.1.IntroductionofthecoalmineTheHuatingCoalMineinNorthwestChinaisnowextractingthethirdfullymechanizedtopcoalcavinglongwallfaceLW250103inthe?rstdistrictofsecondlever.LW250103isadja-centtothe250102gobinthewestwitha5mwidthpillarbetweeneachotherandsolidcoalseamintheeastwith200mfacelength.Table1showsthelithologyofLW250103fromthesurfacetocoalseam.Thecoalseamis12mthickwithanaveragedipangle5de-gree,theimmediateroofismudstoneofabout7.5mthickand30m?nesandstoneconstitutesthemainroofalsoplaystheroleofsubkeystrata,20mgritstonewithgravel80mawayfromthecoalseamanalyzedtobemainkeystrata,becausenoneoftherestuntilsoilonsurfacecanformthemainkeystrata.Theminingtremorsoccursfrequentlyandinducedtensofrockburstscausedgreatdamagetotheworkfaceandroadways,hencethe16-channal‘‘SOS’’systemwasintroducedtomonitortheseis-micevensincludingfourteenstationsundergroundandtwosta-tionsonsurface.TheSeismologicalObservationSystemcalled‘‘SOS’’forshortthatnewlydevelopedbyCentralMiningInstituteofPoland,asoneofthemostadvancedmonitoringequipmentathomeandabroad,SOScomprisedbytheseismicdatatransmissionsystemwithmaximumdistanceof10km,seismicgeophonesoffrequencyband1C600HzandtheAS-1SeismicRecordingSystem.Itcanaccuratelydeterminethesourceparameterssuchasoccur-ringtime,coordinatesandenergyofthelowenergytremorsoftheorder10C100Jwiththehorizontallocationerrorlessthan20m,theverticalerror50mundertheoptimalcon?gurationofseismologicalnetwork.Fig.5showsthelayouttheSOSnetworkofHuatingmine.4.2.CharacteristicofF-structurerevealedbySOSDuringtheexploitationofLW250102whichwasadjacenttoLW250101anda20mwidthcoalpillarbetweenthem,mininginducedtremorsoccurredfrequently.ThelocationofthetremorsSeismicityAkcBloFShear slipBlock B(b) Instabilityof the block of the “Voussoir Beam”Fig.4.Mechanicalandmovementmodeloftherockblocks.thestratabehaviorsoftheworkingface,miningtremorsoccurredfrequentlyinthegobandaroundtheroadways.Fig.1aboveillus-trates‘‘VoussoirBeam’’structurediagramofruptureroofformedaftercoalexcavation.ActuallyblockBisatriangleroofplatewithanarcsideabovetheface-endswhichfracturedinthecoalseam2C10mawayfromthewallandanothersidehingedwithblockC.BlocksA,BandCtogethercanformthethree-hingedarchequilib-riumstructure,thisbalancedstructureclampedbythesolidcoalofthenextlongwallface,topcoalthatnottransportedoutattheface-end,immediateroofinthecavingzoneandblockAinthefracturedzonetomaintainarelativebalancedstateuntilthebeginningofcoalwinningbesides.Withthenextworkingfacead-vanced,thesolidcoalandimmediateroofwhichsupportedtheblockAcontinuouslycavedandextracted,thelocationoffracturedlinewouldinevitablycoincideswiththesubkeystrataofthepre-viousface.ThetwokeyrockblocksAandBabovethefaceendhingedtogetherlikea‘‘tower’’whosestabilitywasaffectedbytherotaryandsinkofblockA.Fig.4bshowsasimpli?edmodeltoanalyzethemechanicalbal-anceoftheF-structure,takingtherockblockswhichplayaleadingroleforstudyingobjects.AffectedbytherotarymovementofrockblockA,the‘‘VoussoirBeam’’structureneedsmuchmorehugehorizontalforcetokeepthebalance.Weknowthatthecriticalhorizontalforcethatmaintainedthestructurebalancegrowssharplywiththeincrease516Table1LithologyofLW250103.Sequence1C345C789C718CC344-LithologyZ.Muetal./InternationalJournalofMiningScienceandTechnology23(Thickness(m)221.415.17.677.1.556..154.7.13.0.3.75Compressivestrength(MPa)KeystrataLoessmudstoneSiltstoneSandstoneandmudstoneSandymudstoneSandstoneandmudstoneConglomerateSandstoneandmudstoneMediumsandstoneFinesandstoneFinesandstoneGritstoneFinesandstoneSandstoneandmudstoneSiltstoneSandstoneandmudstoneFinesandstoneSandstoneandmudstoneFinesandstoneSandstoneandmudstoneSandstoneandmudstoneSandstoneandmudstoneSiltstoneSandstoneandmudstoneSiltstoneFinesandstoneSandstoneandmudstoneCoalseamMainkeystrata(short-Farm)No.4keystrata(short-Farm)No.3keystrata(short-Farm)No.2keystrata(short-Farm)No.1keystrata(short-Farm)Fig.5.LayoutoftheminingseismicmonitoringsysteminstalledinHuatingCoalMine.Z.Muetal./InternationalJournalofMiningScienceandTechnology23(517successivelybrokeandcaved,therebyformed4stripesofseismictremorsinthegob.ThelengthofF-structurearmisapproximately100mhalftheworkfacewide.4.3.Evolutionoftheseismicitiesduringthe?rstweightingstageofLW250103Thetime-spaceevolutionprocesscanre?ecttheruptureandmovementoftheoverlyingstrata,forexampleintheperiodthatfromthebeginningoftheminingtothe?rstweightingofthemainroof,especiallywhentheworkfaceadvancedahead120C150mfromtheopen-offcut,thefrequencyandtotalenergyperdayin-creasedsharply,andextendedto250101gob,asFig.7shows.Fig.7arevealsatthebeginningofcoalminingfromMarch1C15inLW250103smalltremors,energyleverof103C105J,distributeaveragelyonthetailentrysideandinthegob,allclosetosmallpil-lar.TremorsinLW250103areabout20mawayfromthetailentrythatsuggeststhelocationoffractureline,meanwhiletremorsinthegobare30mfromthecoalpillarwhichdeterminesthelengthoffracturedrockblockwhoseinstabilityresponsiblefortheseis-micity.Fig.7bshowsthelocationofbigtremorsinthesameperiodwithenergyexceed105Jthatmainlyconcentrateintheworkfaceformingarupturezonealmostparalleltothetailentryofa20mdistance,elevationofthesetremorsare1020maveragelythatabout30C40mabovethecoalseam.Butfewbigtremorsoccur250101gobfromwhichwecandeterminetheinstabilityprocessinthegoblagsbehindthataboveworkfacearea.Fig.7candddem-onstratestheseismicitydistributionintheregion120C150mawayfromtheopen-offcutwherethe?rstweightingofmainroofhap-pened,tremorsscatterintensivelyandhaveatendencyspreadingtothecentralgob.MechanismofthesebigtremorsisduetotheinstabilityofF-structureofkeystrata.Theupwardtendencyregu-lationoftheseismicsourcelocationcanberevealedsincetheele-vationofthesetremorsduringMarch15toApril1is1080m,60mhigherthanthoseduringMarch1C15.5.ControlmethodsforthedynamicdisastersinducedbyF-structureinstabilityF-structureformedbythefracturedkeystrataandastheboundaryofthenextworkfacewillre-activateanddestabilizeagainunderthein?uenceofmining.TherotaryandslipoftheF-armisresponsiblefortheseismicityandrockburstinthegobwhichcausedbreakanddamagetothegob-sideroadway.Sincethesmallcoalpillarhasalreadybeeninplasticorevenfragmentedstate,theconventionaldestressmeasuresaimingtodecreasethestressconcentrationinthecoalseamsuchasblastingandwaterinjectionareuselessforpreventionthiskindoftremorandhaslit-tleeffectsofroadwayprotection.BasedonthemechanismandcharacteristicanalysisoftheF-structure,weputforwardthreemethodstoeliminatethisdisasterasfollows:(1)InitiativecuttingF-arm.Thedirectionalhydraulicfracturinganddeepholeblastingintotheroofaretwoeffectiveapproaches.(2)Activeimpactresis-tant.Thecorecontentistouseclosedsupportingsystemwithhighstrengthandyieldthatcanresistandabsorbtheseismicenergy.TheO-shellcombinedwithbolt-wire-cableaswellasdoor-hydraulicsupportcanbeadopted.(3)Activeavoidance.Thismeth-odisspeciallydesignedforthickcoalseam,bychangingthelayoutoftheroadway,transformsthegob-sideentrytogob-belowentry.Excavatetheentryunderthegobtherebyontheonehandavoidthein?uenceoftheinstabilityofF-arm,ontheotherthelooseandbrokenrockrefusecansigni?cantlydissipatetheseismicwave,atthesametime,entryunderthegobissituatedinthestressdecreasingzonewhichmakesthemaintenancemuchmoreeasily.Amongthesethreemethods,activeavoidanceisthemosteffectiveFig.6.Distributionofthemicro-seismicsourcesinLW250103.mainlyconcentratedinLW250102andmostofthebiginthecoalpillarmonitoredbytheSOSsystem,whereasveryfewin250101gob,whichindicatedthe20mpillareffectivelyseparatedthecon-nectionofoverlyingstratamovementbetweenLW250102and250101gob,sothestratain250101gobmaintainedstableundertheminingactivities.Inordertosolvethepillar-burstproblem,smallpillarthat5mwidewasadoptedbetweenLW250103and250101gob,butwhenLW250103ismining,lotsoftremorswerelocatedin250101gobandinducedseveralrockburstaccidentstothegob-sideroadway,causeddif?cultiesfornormalproduction.Fig.6showsthetremorswithenergyexceeding104JfromMarch1,2010toJuly25,2011intheprocessofLW250103advancing.Fig.6aistheplanegraphofthedistributionoftheminingtremors,wecanseethatobviousregulationsexhibitin250101gob,?rstthetremorsperiodicallyappear,theintervalisabout200mthatequalstothewidthoftheworkface.Secondly,almostallthevibra-tionstremorsin250101gobconcentratewithinthehalfpartzoneof250101gobthat100mfromtheLW250103,howevertheotherhalfpartthatclosedto250102gobfewtremorsoccurred,whichindicatesthein?uencingareaoftheminingactivitiesisabout100m.Thirdly,theconcentratedzonesofthesourcesinLW250103and250101gobcorrespondwitheachotherthatrevealsthemechanismofthetremorsinthegobisoverlyingstratainsta-bilitycooperativelywiththemovementofLW250103.Fig.6bshowstheACApro?leviewofthetremordistribution.FromFig.6bwecanclearlyidentifytheF-structurealsoexitsamongtheseismicsources,becausetremorsinroofstrataarecausedbythere-activityofF-structureofoverlyingstrata.Theseismiczonethatisalsofracturedzoneonthegobsideis350mabovethework-face,higherthanthesolidcoalseamsideandthesourceenvelopalsoinclinedto250101gobasthelinkingofroofstrata.Intotal,4groupsofkeystratacorrespondingto4armsofF-structure三亿文库包含各类专业文献、中学教育、文学作品欣赏、行业资料、专业论文、应用写作文书、18F_structuremodel_省略_entionincoalmine_MuZ等内容。　分子式:C16H22N2O4
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