曹村矿井2.4Mt-a新井设计-超前预爆破在综采工作面的应用研究

曹村曹村矿井2.4Mt/a新井设计超前预爆破在综采工作面的应用研究题目：姓名：学号：班级：摘要一般部分针对曹村矿井进行了井型为2.4Mt/a的新井设计。曹村矿井位于山西临汾市境内，井田走向长约4.0km，倾向长约6.0km，面积约24km2。主采煤层为11#煤层，平均倾角2~5°，平均厚度9m。井田工业储量为409.5Mt，可采储量267.75Mt，矿井服务年限为79.69a。矿井正常涌水量为500m3/h，最大涌水量为800m3/h。矿井相对瓦斯涌出量1.05m3/t,可以视为低瓦斯矿井。根据井田地质条件，设计采用双立井单水平开拓方式，井田采用全带区式布置方式，共划分为八个带区，轨道大巷和胶带机大巷皆为岩石大巷，布置在11#煤层底板岩层中。针对东一带区采用了带区准备方式，共划分4个分带工作面，并进行了运煤、通风、运料、排矸、供电系统设计。针对11101工作面进行了采煤工艺设计。该工作面煤层平均厚度为9.0m，平均倾角3°，直接顶为泥岩，老顶为细砂岩。工作面采用长壁综采放顶采煤法。采用双滚筒采煤机割煤，往返一次割两刀。采用“三八制”工作制度，截深0.8m，每天六个循环，循环进尺4.8m，月推进度144m。大巷采用胶带输送机运煤，辅助运输采用蓄电池式电机车牵引固定箱式矿车。主井采用两套带平衡锤的16t箕斗提煤，副井采用一对3.0t矿车双层四车窄罐笼和一个带平衡锤的3.0t矿车双层四车宽罐笼运料和升降人员。专题部分题目为《超前预爆破在综采工作面的应用研究》，利用分形理论建立岩石断裂耗散能量与块度分维值之间的理论关系，推导出岩石爆破块度分数维与炸药单耗之间关系。进行了室内相似材料模型爆破实验。验证了上述理论关系。利用爆破岩石表面裂晾分布的分形维数值作为衡量指标，优化爆破孔网参数。为预爆破在实践中的应用提供理论依据，然后通过介绍三种不同环境下的应用，表明该技术有效的提高了回采的安全性，降低了冲击来压强度，资源回收率大幅提高。翻译部分题目为《Studyonthecharacteristicsofgroundpressurebehaviorsinworkingfacewithgreatminingheightatdifferentadvancespeedsbysimilaritymodelexperiment》，主要介绍了在实验室中通过相似模型实验来研究大采高工作面在不同推进速度条件矿压呈现的规律。关键词：曹村矿井；双立井；带区布置；综采放顶煤；超前预爆破；处理坚硬顶板ABSTRACTThegeneraldesignisabouta2.4Mt/anewundergroundminedesignofCaocuncoalmine.CaocuncoalmineislocatedinLinfen,Shanxiprovince.It’sabout4.0kmonthestrikeand6.0kmonthedip,withthe24.0km2totalhorizontalarea.Theminablecoalseamis11#withanaveragethicknessof9.0mandanaveragedipof3°.Theprovedreservesofthiscoalmineare409.5Mtandtheminablereservesare267.75Mt,withaminelifeof79.69a.Thenormalmineinflowis500m3/handthemaximummineinflowis800m3/h.Theminegasemissionrateis1.05m3/twhichcanberecognizedaslowgasmine.Basedonthegeologicalconditionofthemine,thisdesignusesaduel-verticalshaftsingle-leveldevelopmentmethod,andfullstrippreparationwhichdividedintoeightbands,andtrackroadwayandbeltconveyorroadwayareallrockroadways,arrangedinthefloorrockof11coalseam.ThedesignappliesstrippreparationagainstthefirstbandofEastOnewhichdividedinto4stirpstotally,andconductedcoalconveyance,ventilation,gangueconveyanceandelectricitydesigning.Thedesignconductedcoalminingtechnologydesignagainstthe11101face.Thecoalseamaveragethicknessofthisworkingfaceis9.0mandtheaveragedipis3°,theimmediateroofismudstoneandthemainroofissandstone.Theworkingfaceappliesfullymechanizedcavingmethod,andusesdoubledrumshearercuttingcoalwhichcutstwiceeachworkingcycle."Three-Eight"workingsystemhasbeenusedinthisdesignandthedepth-webis0.8mwithsixworkingcyclesperday,andtheadvanceofaworkingcycleis4.8mandtheadvanceis144mpermonth.Mainroadwaymakesuseofbeltconveyortotransportcoalresource,andbatterylocomotivetobeassistanttransport.Themainshaftusesdouble16tskipstoliftcoalwithabalancehammerandtheauxiliaryshaftusesatwinsnarrow3.0tfour-cardouble-deckcageandawide3.0tfour-cardouble-deckcagetoliftmaterialandpersonneltransportation.Themonographicstudyentitled"Theappliedresearchoftheaheadofthepre-blastingintheworkingface",asimplefractalmodelofrockfractureisestablishedtodealwithdissipatedenergyofrorkfractureandfrartaldimensionofrockfragmentationandtoobtainthetheoreticalrelationbetweenthefractaldimensionofrockfragmentationandexplosivespectficcharge.Theblastingexperimentofsimulationmaternalmodelisconductedtoverifytheoreticalresults.Takingthefractaldimensionofcrackdistributiononthesurfaceoftopcoalasanindexafterblastingtopcoal,someblastingparametersareoptimizedandthebestblastingplanisfinallydeterminedinon-the-spotmining.Itsconclusionprovidesatheoreticbasicforthepracticalapplicationsoftheblastingsofteningtechnology.Then,byintroducingthepracticalapplicationsoftheblastingsofteningtechnologyinthreedifferentenvironments;itshowsthetechnologyimprovestheminingsafetyandrecoveryrateeffectively.Thetitleofthetranslatedacademicpaperis"通过相似模拟实验研究大采高工作面在不同推进速度条件下矿压显现特性".Itshowsthecharacteristicsofgroundpressurebehaviorsinworkingfacewithgreatminingheightatdifferentforwardspeedswerestudiedbysimilaritymodelexperimentinlaboratory.Keywords:Caocuncoalmine;doubleverticalshaft;bandmode;fullymechanizedcoalcaving;preliminarydemolition;hardroofprocessing;第页外文原文JOURNALOFCOALSCIENCE&ENGINEERING(CHINA)ISSN1006-9097pp28-31Vo1.13No.1Mar.2007StudyonthecharacteristicsofgroundpressurebehaviorsinworkingfacewithgreatminingheightatdifferentadvancespeedsbysimilaritymodelexperimentHUAXin-zhu(华心祝)1，ZHANGJin-long(张金龙)2，XIEGuang-xiang(谢广祥)1Dept.ofResourceExploitationandManagement,AnhuiUniversityofScienceandTechnology,Huainan232001,China;2.CollegeofCivilEngineering,HohaiUniversity,Nanjing210098,China)AbstractPresentlymostofresearchresultsonstratabehaviorswereconcludedunderthenormal(moderate)advancerateconditions.Comparingwithnormaladvancerate,fastadvancerateandslowadvanceratemaycausesomenewchangesofstratabehaviors.Thecharacteristicsofgroundpressurebehaviorsinworkingfacewithgreatminingheightatdifferentforwardspeedswerestudiedbysimilaritymodelexperimentinlaboratory.Itsconclusionprovidesatheoreticbasisforgroundpressurecontrolling.Keywordssimilaritysimulation,advancerate,workingfacewithgreatminingheight,groundpressureIntroductionTheadvancerateofthehigh-yieldandhigh-efficiencyandhigh-powerfullymechanizedcoalfaceisasmuchmoreseveraltimesasthatoforthodoxface.Buttheadvancerategetsslowwhenworkingfaceencountersabnormityoritsmachinesandelectricdevicesfailure.Comparingwithnormaladvancerate,fastadvancerateandslowadvanceratemaycausesomenewchangesofstratabehaviors.Bysimilaritymodelexperimentinlaboratory,thecharacteristicsofgroundpressurebehaviorsinworkingfacewithgreatminingheightatdifferentforwardspeedsarestudiedinthispaper.Itsconclusionmayprovideatheoreticsupportforgroundpressurecontrolling.1TheprototypegeologyTheprototypeistheworkingfaceNo.1215(3)inZhangjicoalmine,Huainan.Thisworkingfacelocates-600mlevelinthemine.Theelevationoftheworkingfaceisfrom-410mto-570mandthefacelengthis200m.TheC13-1coalseamisexcavatedinthisworkingfaceanditsthicknessisfrom3.6mto4.2m,theaverageis3.9m.thedipangleofthecoalseamisfrom6to10°,theaverageis8°.ThevalueofProtodyakonvcoefficientofcoalstrengthisfrom0.7to1.2.Thecoalseamoccurssteadyanditstextureissimple.Thefullymechanizedcoalminingmethodwithgreatminingheightisadoptedinthisworkingface.2Experimentdesign2.1SelectionoftherigformodeltestTheexperimentwasconductedontheplanestressrig.Theheightofprototypeis100m,including10mbottombed,3.9mcoalseamand86.1mtopcover.Thesizeofmodelis:length×width×height=3m×0.3m×lm.2.2Meteringequipmentsandmeasuringpointsarrangement(1)MeasuringpointsarrangementStressmeasuringpointsanddisplacementmeasuringpointsarelaidinthemodel.Thereare36stressmeasuringpointswhichweresetinthecoalseam,theimmediateroofandthemainroofrespectivelyforobservingthecharacteristicsofstresschangeatdifferentforwardspeeds.Thereare9displacementmeasuringlines,including18measuringpointswhichweresetintheimmediateroofandthemainroofrespectivelyforobservingthecharacteristicsofthedisplacementandfallingrateofoverlyingstrataatdifferentforwardspeeds.(2)MeteringequipmentsTheBW-15tinselmicro-dynamomareusedforobservingthecharacteristicsofstresschangeincoalpetrographicmass.Itisadisk.Itsdiameteris28mmanditsthicknessis7mm.TheYHD-50electric-resistancedeformareusedforobservingthecharacteristicsofthedisplacementofoverlyingstrata.ThedataarecollectedbytheYJD-27straingauge,theYE2532data-collectionsystemandcomputerintheexperiment.2.3ExcavationsimulationThe30mcoalpillarisretainedrespectivelyattheleftandrightexcavationboundaryinordertoreducetheboundaryeffect.Threedifferentadvanceratesaresimulatedinthemodel.Theyareslowadvancerate(2.4m/d),normaladvancerate(4.8m/d)andfastadvancerate(9.0m/d).Workingfaceadvancesin80mateachforwardspeed,soworkingfaceadvancesin240mtogether.2.4ObservationcontentInthisexperiment,theweightinglengthofmainroof,roofsubsidence,fallingrate,influenceareaandthelocationofpeakvalueofthefrontabutmentpressureandthefactorofstressconcentrationareobservedatdifferentforwardspeeds.3Testresultsandanalysis3.1Thecharacteristicsofroofcavingatdifferentforwardspeeds(1)NormaladvancerateWiththeadvancementofworkingface,themainroofspanincreasescontinuously.Themainroofrupturesandfallsafterworkingfaceadvancesin26m.Then,themainrooffallsperiodicallyandtheperiodicweightinglengthofmainroofisabout15m.(2)FastadvancerateTheperiodicweightinglengthofmainroofisabout16matfastforwardspeed.Theperiodicweightingofmainroofhappensfrequentlyfortheadvancerateofworkingfaceisverysoon.Theweightingofmainroofoccursabouteveryoneortwodays.Duringtheperiodicweightingofmainroof,themainroofswingsandsubsidisessuddenly,then,itgetsequilibriumfast.(3)SlowadvancerateTheperiodicweightinglengthofmainroofisabout11matslowforwardspeed.Theperiodicweightingofmainroofhappensinfrequentlyforthedetentionperiodofworkingfaceisrelativelylonginsomearea.Theweightingofmainroofoccursabouteveryfourorfivedays.Theplaceoccuringdelaminationandbreakageintheroofaboveworkingfaceisfarfromtheworkingface.(4)ComparisonofthecharacteristicsofroofcavingatdifferentforwardspeedsThecomparisonresultsofthecharacteristicsofroofcavingatdifferentforwardspeedsshowninTable1[1].Table1ComparisonofthecharacteristicsofrooffallingatthreedifferentforwardspeedsAdvancerateWeightinglength(m)WeightingInteral-time(d)Weightinginfluence-timeCharacteristicdescriptionSlow114~5VerylongCrackedirregularshapeNormal153LongRegularshapeFast161~2ShortLargeblockTable1showsdifferentcharacteristicsofroofcavingatthreedifferentforwardspeeds.Tosumup,atfastforwardspeed,theperiodicweightinglengthofmainroofisthegreatestoneanditisabout16m.Themainroofisintegralrelatively.Theweightinginterval-timeofmainroofisabout2dandtheweightinginfluence-timeisshort.Atslowforwardspeed,theperiodicweightinglengthofmainroofisthesmallestoneanditisabout11m.Themainroofiscracked;theweightinginterval-timeofmainroofisaboutfourorfivedaysandtheweightinginfluence-timeislong.Atnormalforwardspeed,characteristicsofroofcavingarein-between.3.2ThecharacteristicsofdisplacementatdifferentforwardspeedsCoordinatezeroissetoneverymeasuringpoint.Thehorizontalcoordinatedaxisindicatesthehorizontaldistancefrommeasuringpointtowallface(unit:m,thepositivevalueindicatesthemeasuringpointisinfrontofthewallface,viceversa).Theverticalcoordinatedaxisindicatesconvergence(unit:mm)andfallingrate(unit:mm/d)ofmeasuringpoint.Theconvergence(fallingrate)-advancedistancecurvesatdifferentforwardspeedsshowninFig.l.Fig.1CurvesofconvergenceandfallingrateofroofatdifferentmeasuringpointsonthemeasuringlineⅠ,ⅡandⅢatnormal,Ⅳ,Ⅴ,Ⅵatfast,Ⅶ,Ⅷ,Ⅸatslowforwardspeed(1)ConvergenceandfallingrateofroofatnormalforwardspeedThecharacteristicofconvergenceandfallingrateofroofatnormalforwardspeedshowninFig.1(a).Itrevealsthattheconvergenceofunderroofislargethanthatofupperroof.Atthe13.6mdistancelocationbehindthewall,theconvergencevalueofmeasuringpointNo.46,47and48whicharesetintheupperroofarerespectively60.69and73mm,itincreasesgradually.Thefallingrateiscorrespondingly22,24and25mm/d.Thereasonforthisisthatoverlyingstratamovesfullyanditssubsidenceisincreasingwiththewallfarfromtheexcavationboundary.Whileatthesameposition,theconvergencevalueofmeasuringpointNo.38and39whicharesetintheunderroofarerespectively78and76mm,thefallingrateiscorrespondingly25and26mm/d.Thedifferenceofroofconvergencebetweenunderroofandupperroofare9and3mm,theaverageis6mm.Itindicatestheslightdelaminationoccursintheroof.Iftheroof-controldistancebyhydraulicsupportis6m,atthe22mmdistancelocationbehindthewall,theconvergencevalueofmeasuringpointNo.38and39arerespectively32and40mm,theaverageis38mm.Thefallingrateiscorrespondingly20and22mm/dandtheaverageis21mm/d.(2)ConvergenceandfallingrateofroofatfastforwardspeedThecharacteristicofconvergenceandfallingrateofroofatfastforwardspeedshowninFig.1(b).Whenworkingfaceadvanceatfastforwardspeed,atthe16mdistancelocationbehindthewall,theconvergencevalueofmeasuringpointNo.49,50and51whicharesetintheupperroofarerespectively61,65and66mm,thefallingrateiscorrespondingly43,46and49mm/dandtheaveragefallingrateis46mm/d.Whileatthesameposition,theconvergencevalueofmeasuringpointNo.40,41and42whicharesetintheunderroofarerespectively64,68and71mm,thefallingrateiscorrespondingly44,47and51mm/dandtheaveragefallingrateis47mm/d.Thedifferenceofroofconvergencebetweenunderroofandupperroofare3,3and4mmandtheaverageis3mm.Itindicatestheupperroofandunderroofmovetogether.Atthe6mdistancelocationbehindthewall,theconvergencevalueofmeasuringpointNo.40,41and42arerespectively17,18and18mmandtheaverageis18mm.Thefallingrateiscorrespondingly18,19and17mm/d,theaverageis18mm/d.Theaveragefallingrateatthe6mdistancelocationbehindthewallismuchlessthanthatatthe16mdistancelocationbehindthewall.Itrevealsthefallingratechangesgreatly.(3)ConvergenceandfallingrateofroofatslowforwardspeedThecharacteristicofconvergenceandfallingrateofroofatslowforwardspeedshowninFig.1(c).Fromthis,wecanseethat,atthe11.2mdistancelocationbehindthewall,theconvergencevalueofmeasuringpointNo.53and54whicharesetintheupperroofarerespectively115and108mm,thefallingrateiscorrespondingly24and23mm/dandtheaveragefallingrateis23.5mm/d.Whileatthesameposition,theconvergencevalueofmeasuringpointNo.43,44and45whicharesetintheunderroofarerespectively134,125and122mm,thefallingrateiscorrespondingly31,26and25mm/dandtheaveragefallingrateis27mm/d.Thedifferenceofroofconvergencebetweenunderroofandupperroofare12and16mmandtheaverageis14mm.Atthe6mdistancelocationbehindthewall,theconvergencevalueofmeasuringpointNo.43,44and45arerespectively76,76and68mmandtheaverageis71mm.Thefallingrateiscorrespondingly25,24and22mm/d,theaverageis24mm/d.(4)ComparisonofthecharacteristicsofsubsidenceamongthreedifferentforwardspeedsThecomparisonresultsshowninTable2.Table2Comparisonofthesubsidencecharacteristicsofroofwithintheroof-controlarea(6mbehindtheworkingface)amongthreedifferentadvancerateItemsAdvancerate(m/d)Slow(2.4)Normal(4.8)Fast(9.0)Theaverageconvergence(mm)713818Theaveragefallingrat(mm/d)212118Table2showsthattheconvergenceandfallingrateofroofwithintheroof-controlareadecreasewiththeadvancerateincreasing,especially,atfastforwardspeed,thedecreaseisremarkable.3.3ThedistributionlawofthefrontabutmentpressureatdifferentforwardspeedsThedistributionlawofthefrontabutmentpressureatthreedifferentforwardspeedsdisplaysinTable3bytest.Table3ComparisonofthefrontabutmentpressureonthecoalseamamongdifferentadvancerateAdvanceThefactorofstressconcentrationKmaxThedistanceformpeakvalueofthefrontabutmentpressuretowallface(m)Slow2.9022Normal2.6214Fast1.4710ThefactorofstressconcentrationKmaxisabout2.9atslowforwardspeedsandthelocationofpeakvalueofthefrontabutmentpressureexceeds22mfromwallface.ThefactorofstressconcentrationKmaxisabout2.62atnormalforwardspeedsandthelocationofpeakvalueofthefrontabutmentpressureis14mfromwallface.ThefactorofstressconcentrationKmaxisabout1.47atfastforwardspeedsandthelocationofpeakvalueofthefrontabutmentpressureisabout10mfromwallface.Thisresultshowsthatthefactorofstressconcentrationandthedistanceformpeakvalueofthefrontabutmentpressuretowallfacedecreasewiththeadvancerateincreasing.4Conclusions(1)Whenworkingfaceadvancesatfastforwardspeed,theperiodicweightinglengthofmainroofisthegreatestoneandtheweightinginterval-timeofmainroofisshort,theweightinginfluence-timeisshortandthemainroofisintegralrelativelyandthefractureareaintheoverlyingstrataissmall.Whileatslowforwardspeed,theperiodicweightinglengthofmainroofisthesmallestoneandthemainroofisdestruct,theweightinginterval-timeofmainroofislongandtheweightinginfluence-timeislong.Atnormalforwardspeed,characteristicsofroofcavingarein-between.(2)Theconvergenceandfallingrateofroofwithintheroof-controlareadecreasewiththeadvancerateincreasing.Comparingwithslowforwardspeed,thedecreaseisremarkableatfastforwardspeed.Itwillbeadvantagedforcontrollingroof.(3)Thefrontabutmentpressurechangesremarkablywhenworkingfaceadvancesatdifferentspeeds.Thefactorofstressconcentrationandthedistanceformpeakvalueofthefrontabutmentpressuretowallfacedecreasewiththeadvancerateincreasing.Itshowsthattoincreasetheforwardspeedisadvantagedforpreventingribtoscaleoff.(4)Thereareotherinfluencefactorsforstratabehaviors.Thecharacteristicsofgroundpressurebehaviorsinworkingfacewithgreatminingheightatdifferentforwardspeedsarestudiedthroughsimilaritymodelexperimentinlaboratory.Researchindicatesincreasingtheforwardspeedisadvantagedforcontrollingroof.Itcoincideswithpractice.Atthesametime,ittestifiesthatincreasingtheforwardspeedisoneofeffectivemeasuresforcontrollingroof.Fastforwardspeedshouldbedonebypossiblemethodduringtheextraction.References[1]HuaXinzhu.Studyonthemechanismofcontrollingsurroundingstrataforfullymechanizesminingfacewithgreatminingheightalongthelineofinclination[D].Beijing:ChinaUniversityofMiningandTechnology(Beijing),2005.中文译文煤炭科技（中国）刊号1006-9097页码28-31第十三卷第一期2007年三月在相似模拟实验中大采高工作面下矿压显现特性华心祝1，张金龙2，谢光祥1（1.资源开发与管理系，安徽科技大学，淮南232001，中国2.土木工程学院，河海大学，南京210098，中国）摘要目前大多数矿压显现的研究结果的结论是在正常（适度）推进速度的条件下做出的。与正常推进速度相比，快速推进速度和缓慢推进速度可能引起矿压一些新的变化。在实验室中通过相似模型实验来研究大采高工作面在不同推进速度条件矿压呈现的规律。得出的结论为矿压控制提供了一个基本原理。关键词相似模拟，推进速度，大采高工作面，矿压结论在高产高效高强度机械化的采煤工作面中，推进速度是以前工作面推进速度的几倍。但是当工作面遭遇反常情况或工作面的机电设备发生故障，推进速度会变得慢下来。与正常推进速度相比，快速推进速度与缓慢推进速度可能会引起矿压的一些新变化。通过实验室中的相似模拟实验，对大采高工作面在不同推进速度条件下矿压的显现规律进行研究。它的结论可能为矿压控制提供一个理论依据。1地质原型淮南张集煤矿的No.1215(3)工作面是原型，该工作面位于矿山的-600水平，工作面垂直高度从-410m到-570m，工作面长度200m。工作面布置在C13-1煤层中，该煤层厚度3.6~4.2m，平均厚度3.9m。煤层倾角6°~10°，平均倾角8°。Protodyknov煤层强度系数为0.7~1.2。该煤层发育稳定，地质结构简单。工作面适合采用大采高综合机械化采煤方法。2实验设计2.1模型实验设备的选择该实验通过平面压力装置进行控制，原型高度100m，包括10m底板，3.9m煤层厚度和86.1m顶板厚度。该模型尺寸：长×宽×高=3m×0.3m×1m。2.2测量设备和测试点的布置（1）测试点的布置压力测试点和移动测试点均位于模型中，煤层中布置了36个压力测试点，分别观察直接顶和老顶在不同推进速度条件下的矿压显现规律。煤层中布置了9条位移测量线，包括18个直接顶和老顶中的测试点，这样可以观察在不同工作面推进速度下上覆岩层的移动和垮落速率。（2）测量设备BW-15金属微型发电机被用于观察煤岩质量中压力显现规律的变化，该设备是盘状物，它的直径是28mm，厚度是7mm。YHD-50电抗变形仪用来观察上覆岩层位移变化规律，实验室的YJD-27应变计，YE2532数据收集软件和计算机用来收集数据。2.3掘进模拟为了减少边界影响分别在边界的左右两侧留下30m的煤柱，在模型中模拟三种不同推进速率，缓慢推进速率（2.4m/d），正常推进速率（4.8m/d）和快速推进速率（9.0m/d）。用每种推进速率推进80m，即工作面总共推进了240m。2.4观察内容在该实验中，观察在不同推进速度下，老顶加权长度，顶板下降，下降速率，影响区域，前支撑压力高峰值的位置和压力集中系数。3测试结果与分析3.1不同推进条件下顶板下称规律（1）正常推进速率随着工作面的推进，老顶跨度不间断的增长，在工作面推进26m处，老顶破断落下。然后，老顶周期性地冒落，老顶周期性地跨落步距为15m。（2）快速推进速率在快速推进条件下，顶板周期性地跨落步距是16m。对于前进工作面，周期来压频繁的发生是很快的，老顶周期来压一般每1~2天一次，在周期来压时间内，老顶突然间折断下沉，然后，很快的回复平衡。（3）缓慢推进速率在缓慢推进速率条件下，老顶跨落步距大约11m。对于间歇生产工作面，周期来压不频繁的发生相对较长在某些区域，老顶周期来压每4~5天一次，在工作面顶板内发生分层和破断的地方离工作面很远。（4）三种不同推进速率顶板下沉规律的比较三种不同推进速度顶板下沉规律的比较结果如表1所示。表1三种不同推进速度下顶板下沉规律比较推进速率加权长度加权间隔时间加权影响时间特性描述缓慢114~5很长不规则形状爆裂正常153长规则形状快速161~2短很大块岩在三种不同推进速度条件下顶板下沉规律如表1所示，概括来说，在快速推进条件下，老顶周期性垮落步距最大为16m，老顶是完整