陈四楼煤矿2.4Mt-a新井设计-综采工作面过断层技术研究

本科生毕业设计（论文）题目：陈四楼煤矿2.4Mt/a新井设计综采工作面过断层技术研究摘要本设计包括三个部分：一般部分、专题部分和翻译部分。一般部分为陈四楼煤矿2.4Mt/a新井设计。陈四楼煤矿位于河南省永城市境内，交通便利。井田走向（南北）长约13km，倾向（南北）长约6.7km，总面积为61km2。主采煤层为二2煤，煤层倾角为8~23，平均倾角11，平均煤厚为3.5m。井田地质条件较为简单。井田工业储量为28207万t，可采储量为20454万t。矿井设计生产能力为2.4Mt/a。矿井服务年限为65.56a，涌水量较大，矿井正常涌水量为894m3/h，最大涌水量为1087m3/h。矿井瓦斯相对涌出量为0.57m3/t，绝对涌出量为2.0m3/min，为低瓦斯矿井。井田开拓方式为立井两水平开拓，暗斜井延伸。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。矿井年工作日为330d，工作制度为“三八”制。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、准备方式——带区巷道布置；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。专题部分题目是综采工作面过断层技术研究，主要是研究了综采工作面过断层的方法及相关顶板管理控制技术，对综采工作面过断层技术做了全面的陈述。翻译部分主要内容是关于水压控制爆破用于水力致裂技术用来增加煤岩体孔隙率的研究，英文题目为：Hydraulicfracturingafterwaterpressurecontrolblastingforincreasedfracturing关键词：立井；两水平开拓；采区；两翼对角式通风

ABSTRACTThisdesignincludesthreeparts:thegeneralpart,thespecialsubjectpartandthetranslationpart.ThegeneralpartisanewdesignforChensiloumine.ChensiloumineislocatedinYongchengwhichcomeswithinthejurisdictionofShangqiuinHenanprovince.Itisveryconvenienttogettothemineintermsofbothhighwayandrailway.Thelengthofthecoalfieldis13km,thewidthisabout6.7km，andthetotalareais61km2.Thesecondisthemaincoalseams,anditsdipangleis8~23degree.Thethicknessofthemineisabout3.5minall.Thegeologicstructureofthiscoalfieldissimple.Therecoverablereservesofthecoalfieldare282.07milliontons,andtheminablereservesare204.54milliontons.Thedesignedproductivecapacityis24milliontonspercentyear,andtheservicelifeofthemineis65.56years.Thenormalflowofthemineis894m3perhourandthemaxflowofthemineis1087m3perhour.Therelativeminegasgushis0.57m3/tandtheabsolutegushis2.0m3/min,soitisalowgasmine.Themineistwoleveltodevelop.TecentrallanewayusesBeltConveyortotransitcoal,andtrolleywagonsareusedforaccessorialtransportationintheroadway.Theventilationmodeofthismineistwowingsdiagonalform.The“three-eight”workingsystemisusedintheChensiloumine.Itproducesfor330daysayear.Thisdesignincludestenchapters:1.Anoutlineoftheminefieldgeology;2.Boundaryandthereservesofmine;3.Theservicelifeandworkingsystemofmine;4.developmentengineeringofcoalfield;5.Thelayoutofpanels;6.Themethodusedincoalmining;7.Undergroundtransportationofthemine;8.Theliftingofthemine;9.Theventilationandthesafetyoperationofthemine;10.Thebasiceconomicandtechnicalnormsofthedesignedmine.ThetopicofspecialsubjectpartsistheAnalysisofFacetoAcrosstheFaultTechnologyinMechanizedMiningFace.ItmakesafullycomprehensivestatementoffacetoacrossthefaultTechnologyinmechanizedminingface.TranslationpartisaboutHydraulicfracturingandwaterpressurecontrol.TheEnglishtitleis“Hydraulicfracturingafterwaterpressurecontrolblastingforincreasedfracturing”.Keywords:Shaft;twolevel;Panel；Twowingsdiagonalventilation

一般部分1矿区概述及井田地质特征 页英文原文HydraulicfracturingafterwaterpressurecontrolblastingforincreasedfracturingBingxiangHuang,ChangyouLiu,JunhuiFu,HuiGuanSchoolofMines,ChinaUniversityofMiningandTechnology,South3rdRingRoad,Xuzhou,Jiangsu221116,ChinaAbstract:Traditionalhydraulicfracturingtechniquesgenerallyformmainhydrauliccracksandairfoilbranchfissures,butmainhydrauliccracksarerelativelyfewinnumber.Hydraulicfracturingafterwaterpressurecontrolblastingcantransformthestructureofcoalandrockmass.Experimentsprovethatitisaneffectivemethodforincreasingthenumberandrangeofhydrauliccracks,aswellasforimprovingthepermeabilityofcoalseams.Thetechnicalprincipleisasfollows.First,aholeisdrilledinthecoalseamandisinjectedwithagelexplosive(aminingwater-proofexplosive).Then,waterisinjectedintotheholetosealit,atlowenoughpressuretopreventcracksfromforming.Third,waterpressureblastingisdonebydetonatingtheexplosive.Thewatershockwavesandbubblepulsationsproducedbytheexplosioncauseahighstrainrateintherockwallsurroundingthehole.Whenthestressimposedontherockwallsurroundingtheholeexceedsitsdynamiccriticalfracturestrength,thesurroundingrockbreaksandnumerouscircumferentialandradialfracturespropagateoutward.Lastly,waterinjectionprocesses,suchasgeneralinjection,pulseinjection,and/orcyclicinjection,arecarriedouttopromotehydraulicfracturing.Dependingonthefissurewaterpressure,detonationfissurescontinuetoexpandandadditionalhydraulicfractureswithawiderrangeareformed.Undertheeffectofdetonationpressure,jointsandfissuresinthecoalmassopenandpropagate,leadingtoreducedadhesiveforcesonstructuralsurfacesandtherebyenhancingcoalcutting.Therefore,thismethodimprovesthepermeabilityofthecoalseam,effectivelyweakensthestrengthofthecoalandrockmass,andreducesthesurroundingrockstressoftheweakenedarea,effectivelysolvingtheproblemofhavingasmallnumberofbigcracks.Itisausefultechnicalapproachforimprovingtopcoalcaving,preventingrockburst,preventingcoalandgasoutbursts,andraisingthegasextractionefficiencyincolliery.Keywords:Hydraulicfracturing;Waterpressureblasting;Crackpropagation1IntroductionLow-permeabilitycoal-seamgasextraction;hard,thickcoal-seamfullymechanizedtopcoalcaving;androckburstcontrolaretechnicalchallengesincollieryatpresent.Hydraulicfracturingisaneffectivetechnicalapproachtoresolvethesechallenges[1].Thestructureofcoalandrockmassisalteredthroughhydraulicfracturing,whichcanincreasecracksincoalandrockmassimprovepermeability,andweakenstrengthtoreduceanyrockburstingliability.Afterdecadesofdevelopment,morestudyonhydraulicfracturinghasbeenconductedbothinChinaandelse-where[2–14].Simulationexperimentsandfieldinvestigationsofhydraulicfracturingshowthatthetraditionalhydraulicfracturinginnumber.Inthecaseofhomogeneousrock,asinglehydraulicmaincrackisgenerallygeneratedandcracksaremainlyconcen-tratedinabandaroundthehydraulicmaincrack,whoseextentissmall.However,toimprovehard,thicktopcoalcavability,handlehardroof,preventrockburst,increasepermeabilityofgassycoalseams,andpreventcoalandgasoutbursts,fullre-formationofthestructureofcoalandrockmassbyhydraulicfracturingisneeded.Thisrequiresthathydraulicfracturingproducemorehydrauliccracks,i.e.,increasethenumberofhydrauliccracks.Therefore,thereisanurgentneedtostudyhydrauliccontrolfracturingtechnologytoincreasethenumberofhydrauliccracks,whichhasimportanttheoreticalandpracticalsignificanceinguaranteeingefficientandsafecollieryproduction.Commonexplosivesblastingforgassycoalseamshassafetyrisks,sotheyarenotsuitable.Waterpressureblasting,developedinthepastcenturyasakindofcontrolledblastingmethod,caneffectivelycontrolthegenerationofblastingflyingrocks,airshockwaves,blastingtremors,anddetonationtoxicgases[15–18].Waterpressureblastingisagun-holeblastingtechnologythatuseswaterasacouplingmediumbetweenthecartridgeandthechargeholetotechniquesmainlyformwaterpressuremaincracksandairfoilbranchfissures,butwaterpressuremaincracksarerelativelyfewinnumber.Inthecaseofhomogeneousrock,asinglehydraulicmaincrackisgenerallygeneratedandcracksaremainlyconcern-tratedinabandaroundthehydraulicmaincrack,whoseextentissmall.However,toimprovehard,thicktopcoalcavability,handlehardroof,preventrockburst,increasepermeabilityofgassycoalseams,andpreventcoalandgasoutbursts,fullre-formationofthestructureofcoalandrockmassbyhydraulicfracturingisneeded.Thisrequiresthathydraulicfracturingproducemorehydrauliccracks,i.e.,increasethenumberofhydrauliccracks.Therefore,thereisanurgentneedtostudyhydrauliccontrolfracturingtechnologytoincreasethenumberofhydrauliccracks,whichhasimportanttheoreticalandpracticalsignificanceinguaranteeingefficientandsafecollieryproduction.Commonexplosivesblastingforgassycoalseamshassafetyrisks,sotheyarenotsuitable.Waterpressureblasting,developedinthepastcenturyasakindofcontrolledblastingmethod,caneffectivelycontrolthegenerationofblastingflyingrocks,airshockwaves,blastingtremors,anddetonationtoxicgases[15–18].Waterpressureblastingisagun-holeblastingtechnologythatuseswaterasacouplingmediumbetweenthecartridgeandthechargeholetotransfertheexplosionpressureandenergyatthemomentoftheexplosiontobreakuprock.Theprincipalcharacteristicsofwaterareexploitedasfollows.Sincewaterisdifficulttocompress,deformationenergylossesarelowandenergytransmissionefficiencybecomeshigh.Wateractstodeliveruniformpressure,makingthepressureonthesurroundingmediumrelativelysmoothandevenlydistributed,leadingtoevenbreakingofthesurroundingrockandgreatlyreducingtheharmfuleffectsofblasting.However,thecompressionratioofwaterexceedsthatofrockunderhighpressureandwateralsoactsasthebufferlayerbetweentheexplosiveproductsandtherockmass.Notonlydoesthisbufferlayerextendtheinteractiontimeoftheshockwaveontherock,butitalsocanreduceoreliminatetheenergylossintheplasticdeformationzonegeneratedintherockmass.Waterpressureblastingiscurrentlyamorematuretechnologyinfieldssuchastunnelexcavationandprojectdemolition.Inrecentyears,theapplicationofwaterpressureblastingtocollieryhasstartedinChinaandelsewhere[19,20].IntheformerSovietUnion,coal-seampre-injectioninternalexplosionswereconductedbyusingan8-m-deepholeof40mmdiametertopreventcoalandgasoutburstsinagentlyinclinedthincoalseamandamediumthickcoalseam.InChinaattemptsweremadetocreatecracksbywaterpressureblastingtoimprovethecoal-seamgasdrainagerate[21].Inviewoftheproblemsofexistingtechnology,apreliminarytesthasbeenconductedtoexploittheadvantagesofwaterpressureblastingandhydraulicfracturing.Thetestresultsshowthathydraulicfracturingafterwaterpressureblastingcanincreasethenumberandrangeofhydrauliccracksefficiently.Basedonpreliminarystudiesandtestresults,theauthorhasproposedtheuseofwaterpressurecontrolblastingforincreasingpermeabilityandweakeningstrengthasaresultofhydraulicfracturing.2.UsingwaterpressurecontrolblastingtoincreasepermeabilitythroughhydraulicfracturingWaterpressurecontrolblastinginduceshydraulicfracturingintheboreholeofacoal-rockseam,whichchangesthestructureofthecoal-rockmassandincreasesthenumberandrangeofhydrauliccracks,therebyincreasingpermeabilityandweakeningstrength.Thetechniqueinvolvesthefollowingsteps:(a)Drillaboreholeforhydraulicfracturingweakeningwithadrillingrig,injectanadequateamountofgelexplosive(awater-proofmineexplosive),andpulltheleadwireoutoftheborehole.(b)Aftersealinguptheboreholeorificewithholepackerorcementmortar,injectwaterintotheholeuntilitfillstheholeorreachesapressurevaluebelowthatwhichwouldgeneratewaterpressurecracks.Atthismoment,theinitialwaterpressureintheboreholemustbelessthantheorificerupturewaterpressure:whereistheminimumprincipalstressofthecrustalstressfieldaroundtheborehole,isthemaximumone,andisthetensilestrengthoftheboreholerock.(c)Detonatetheexplosivetocarryoutwaterpressureblasting.Thewatershockwavesandbubblepulsationsproducedbytheexplosionwillcauseahighstrainrateintherockwallsurround-ingthehole.Whenthestressimposedonthesurroundingrockwallexceedsitsdynamiccriticalfracturestrength,therockrupturesandgeneratesabundantcircumferentialandradialfracturessurroundingtheborehole.Meanwhile,becauseoftherock’selasticity,thehole’sinfluenceonthesurroundingrockstressdistributionisabout3–5timestheboreholediameter.Undertheeffectofsubsequentwaterpressure,cracksareinitiatedinthewalloftheholewhentheeffectivetangentialtensilestressofthewallexceedstherocktensilestrength.However,foragivencrustalstressfield,thepositionofthemaximumeffectivetangentialtensilestressoftheboreholewallisaconstant.Therefore,toincreasethedifferenceofhydrauliccrackinitiationbetweenthefollow-upboreholehallandtheblastingcracksandmaketheblastingcrackscrazepreferentially,thelengthofblastingcracksmustbegreaterthan3–5timestheboreholediameter.(d)Then,performwaterinjectionprocessessuchasgeneralinjection,pulseinjection,andcycleinjectiontocarryouthydraulicfracturing.Dependingonthefissurewaterpressure,blastingcrackscontinuetoexpandandmorewaterpressurefractureswithawiderrangeareformed.Thesurroundingrockloosingzoneofcollieryroadwayorgrottoforconstructingaboreholeisgenerally1.5–2.0m.Becausethewaterpressureinducedbywaterpressureblastingisgreat,thesealinglengthinthecompletesurroundingrocksectionoftheboreholemustbegreaterthan2m.Theboreholelengthforinstallingthegelexplosivemustexceed1m.Thus,theundergroundfracturingboreholedepthincollieryshouldnotbelessthan5m.Thestructureofcoalandrockmassisre-formedbyhydraulicblastingcontrolfracturing,leadingtoanincreasednumberofhydrauliccracks,anincreaseinthepermeabilityofthecoalseam,anefficientweakeningofthestrengthofcoalandrockmass,andareductioninthesurroundingrockstressoftheweakenedarea.Thiseffectivelysolvestheproblemofhavingasmallnumberofbigcracks.Thereareanumberofbeneficialeffectsfromthisprocess.Theweakeningofthehardcoalcanimprovetopcoalcapability,reducetheriskofrockburst,increasetherangeofcoal-seamfracturingcracks,makegasextractioneasier,andpreventcoalandgasoutbursts,allofwhichareimportantinguaranteeingefficientandsafecollieryproduction.3.Experimentalscheme3.1.ExperimentalsystemWedevelopedatruetriaxialhydraulicfracturingexperimentalsystem.Thesystemconsistsofanexperiment-benchframework,aloadingsystem,andamonitoringsystem.Themaintechnicalindicatorsareasfollows:(1)thetruetriaxialstressisloadedoncubicsamplestosimulatecrustalstress;thepressurefromtheloadingplateinthreedirectionscanreach4000kN.(2)Thesizeofthecubicspecimenisor.(3)Thewaterpressureforboreholefracturingcanreach70MPa.Duringboreholefracturing,parameterssuchaswater(liquid)pressureandflowaremonitoredbyanIntelligentVortexFlow-meterconnectedtothecomputer,usingestablishedproceduresfordatacollectionandstorage.Duringthefracturingsimulation,thecrackpropagationprocessandgeometricmorphologyaremonitoredbyaDisp-type24-channelacousticemissioninstrument,anRSMacousticinstrument,andaTDS-6Micro-seismicacquisitionsystem.3.2.ExperimentalmethodThesimulationexperimentadoptsasidelengthof500mmforthecubicspecimenmixedwithcoalandbriquette.(Theoriginalcoalsizeisabout.)Aparametertestofthemechanicalpropertiesofbothcoalandbriquetteofdifferentratioshasbeenconductedtoensurethatthestiffness,strength,andotherpropertiesofthebriquetteareassimilartocoal’sasfaraspossible.Thequalityratioofthesimulatedsampleisdeterminedascoalpowder:cement:plaster:water?0.5:1:1:0.8anditsmechanicalpropertiesareshowninTable1.Afterthespecimenhasnaturallydried,aboreholeof30cminlengthisdrilledatthecenteroftheuppersurfaceofthespecimenandthenSHZbarglueisusedtobondthedevicebondtotheboreholewalltocompletethesealingwhilethesealingdepthreaches20cm.Weoriginallyplannedtouseelectricdetonatorstocarryoutthesimulationexperimentofhydraulicblastingcontrolfracturing.Theexplosiveamount(1g)ineachelectricdetonatorismodestandthedetonatorscanbedetonatedinwatertoachievethepurposeofblastingaftersealingunderwaterpressure.Thus,anelectricdetonatoristheidealblastingequipmentforthesimulationexperiment.However,becausethepublicsecuritysectorstrictlycontrolselectricdetonators,itishardtoobtainblastingelectricdetonators.Therefore,thelargefirecrackershowninFig.1bwasusedasblastingequipmentforthesimulationexperiment.Thehydraulicblastingcontrolfracturingissimplifiedintotwostagestosimulate(1)blastingintheboreholeand(2)hydraulicfracturing.Thesimulatedstressfieldconditionis,,andandthestressdirectionisshowninFig.1c.Redposterdyeisaddedtothewatertanktomakeiteasiertoobservethehydraulicfracturemorphology.Duringtheexperiment,amicroseismicinstrumentisusedtomonitormicroseismicinformationofthespecimen;thetriggerthreshold(STA/LTAratio)ofamicroseismiceventis1.2,andtheamplituderangereaches500mAwithanSTA/LTAtimewindowof(0.1s)/(1s).Atthesametime,acousticemissionandelectromagneticradiationaremonitoredduringtheexperiment.Anacousticemissionprobe(R.45)placedintheexperimentalframeworkcloselystickstothespecimenandanelectromagneticradiationprobestaysclosetotheoutersteelringoftheexperimentalframework.Anacousticemissioninstrumentusestheacousticemissionprobeandtheelectromagneticradiationprobetotakesamplesatthesametime.Thefrequencydomainfoftheelectro-magneticradiationprobeis30kHz.Thesamplingfrequencyboththepre-amplifier(BP-SYS)andtheacousticemissionprobeis5MHz;thetriggerthresholdoftheelectromagneticradiationprobeis20dB,thetriggerthresholdoftheacousticemissionprobeis39dB,andthepre-ampgainis60dBforboth.Thehigh-passfilteroftheelectromagneticradiationprobeissetto20kHzandthehigh-passfilteroftheacousticemissionprobeis1kHz.Thelow-passfiltersforbotharesetto400kHz.Tocomparewiththeresultsofcommonhydraulicfracturingincoalandrockmass,onecommonhydraulicfracturingsimulationexperimentoffissuredcoalandrockmassunderthesamesimulatedcrustalstressandqualityratioofsamplehasbeenconducted.4.Analysisofresults4.1.Crackpropagationprocessofhydraulicfracturingafterwaterpressurecontrolblasting4.1.1.BlastingAfterthelargefirecrackershowninFig.1bislit,itisputatthebottomofthedrillholeandthenthesquareironpadof70.2kgcontainingtheexperimentframeworkissettocovertheorificeareaofthespecimen.ThetypicalmicroquakesmonitoredduringtheexperimentareshowninFig.2,wheretheabscissaplotstime,everysmalldivisionstandsfor0.1s,andthetotaltimeshownis5s.Inthefigure,thefirsteventisthequakecausedbythesquareironpadafterlightingthefirecracker;thesecondeventisthemicroquakeeventcausedbyblasting;thethirdeventmarkstheupwardjumpoftheironpadcausedbythedetonationgasaftertheexplosion.Aftersixblastsatthebottomofthedrillhole,thespecimensurfaceshowsnovisiblecracksandisstillintegrated.Thespecimenisthenplacedonthetestdeskforthehydraulicfracturingexperimentaftersealing.4.1.2.HydraulicfracturingThewaterpressureandacoustic–electriceffectduringhydraulicfracturingafterblastingareshowninFig.4.Atotalofsevenwaterinjectionfracturingexperimentswereconducted.Forthefirsttwo,thepressurewascontrolledmanually;forthelastfive,ahighhydraulicpressurewaspre-setbyastabilizerandwaterinjectionfracturingwithhighflowwascarriedoutbypressureoutputswitches.Whenthehydraulicpressureofthefirstwaterinjectionfracturingreaches1.1775MPa,aturningpointinthehydraulicpressurecurveappears(Fig.3b).Atthismoment,boththepulsenumberandtheamplitudeoftheelectromagneticradiationshowasmallpeak(Fig.3eandf),indicatingthatthedrillholewallruptures(ortheoriginalblastingcracksopenandburst),meaningthatthehydraulicpressureofruptureis1.1775MPa.Afterthehydraulicpressurereaches1.4775MPa,itthendecreases,showingthatthehydraulicfracturepropagatesatthistime.Afterthehydraulicpressurereachesamaximumof1.5375MPa,itfallsto1.4075MPawitharelativelyhighspeed,meaningthatthehydraulicfracturepropagateswithalargescale.Whenthehydraulicpressurebecomesabout1.40775MPa,itremainsconstantfor9sandthensharplydeclines.Meanwhile,boththepulsenumberandtheamplitudeofelectromagneticradiationhavesignificantpeaksandthedeformationandfailureofcoalandrockmassareexacerbated.Inthesecondwaterinjectionbymanualcontrol,whenthehydraulicpressurereaches1.2575MPa,thesamesituationaswiththefirstinjectionfracturingappears.Thehydraulicpressureexhibitsaturningpoint,whichindicatesrenewedopeningofthehydrauliccrack.Afterward,thehydraulicpressurerisesto1.4075MPaanditdeclinesstablyinonly3s.Thehydrauliccrackperforatesthroughthespecimensurfacefully;watercomesoutofthespecimenorificesurface(uppersurface)andthehydraulicpressuredecreasessharply.Duringthesubsequentfracturingofmultipleinjections,theratioofwaterfiltrationdecreasesrelativelybecauseofhighflow.Sothehydraulicpressurereachesamaximumof1.6775MPa,whichisgreaterthanthemaximumpressureobtainedbymanualcontrol.Thus,whenthefiltrationrateofthecoalandrockseamislarge,ahighflowofwaterinjectionfracturingshouldbeusedtoensurehigherwaterpressureonthecracktiptocausethehydraulicfracturetopropagate.Duringthewholeprocessofhydraulicfracturing,sevenmicroquakeeventsweremonitored;atypicalexampleisshowninFig.4.Incomparisontoblastingquakes,microquakesinducedbyhydraulicfracturepropagationaremuchweaker.Underlaboratoryconditions,becausethelayoutspaceoftheprobesissmall(2morless),thedifferenceintimeatwhicheachprobereceivesthemicroquakeeventsisverysmall,leadingtodifficultyinlocatingmicroquakeevents.Justasmicroquakesinducedbyhydraulicfracturinginalaboratoryspecimencanbemonitored,large-scalemicroquakesinducedbyhydraulicfracturinginthefieldalsocanbemonitored.Andbecausetheon-sitemonitoringregionislarge,themicro-quakesource(hydraulicfracturingpoint)canbelocatedatthesametime.Therefore,microquakeeventsinducedbyhydraulicfracturingcanbemonitoredbyamicroseismographduringhydraulicfracturinginthefield,leadingtoreal-timemonitoringandresearchonhydraulicfracturing.4.2.CrackpropagationshapeofhydraulicfracturingafterwaterpressureblastingThecrackshapeontheportholesurfaceofthetestblockafterhydraulicfracturingisshowninFig.5.Alongthedirectionofmaximumprincipalstress,sand-scouringoccursandtwowateroutletsaredistributedonbothsidesofthedrillhole.Thenormaldistancestothecenterlineofmaximumprincipalstressinthetestblockare75and85mm,respectively;thewidthofthecrackbandinducedbyhydraulicfracturingafterwaterpressureblastingreaches160mm.Atotalof13visiblecracksalongthedirectionofmaximumprincipalstressexistinthebandofhydraulicfracturing.Thence,hydraulicfracturingafterwaterpressureblastingcanformmorehydrauliccrackstheoreticallyandexpandthecrackbandalongthemainhydraulicfracturesurfaceunderthecombinedeffectsoftheblastingshockwaveandhydraulicpressure.Structuralplanessuchasjoints,fractures,andfaultsincoalandrockmasscanrefractandreflectacousticwaves.Asthedevelopmentdegreeofthevariousstructuralplanesincoalandrockmassintensifies,thesoundspeedincoalandrockmassalsodecreasessignificantly.Thesquareratiooftheaveragespeedofsoundinrock(Vp-rock)andaveragespeedofsoundincoalandrockmass(Vp-mass)istheintegritycoefficient().Thus,Isappliedtoindicatetheintegrityofcoalandrockmass.Beforetheexperimentofhydraulicfracturing,thesoundspeedoftheintegratedtestblockwasmeasured.Thenthesamespeedtestisconductedafterfracturing.Measuringpoints2cmapartarelaidoutonbothsidesparalleltothehydrauliccracksurfaceandatotalof625measuringpointsareobtained.Becausethecornersoftestblockgetdamaged,only504measuringpointsareactuallyavailable.Thedistancebetweencorrespondingmeasuringpointsonthetwosidesis50cm,soatotalof504datapointsareobtained.Thesoundpropagationspeedofeachpointisacquiredbymeasurement.Usingtheupperrightcornerofthetestblockasthecoordinateorigin,theverticaldownwarddirectionasthepositiveX-axis,thehorizontaldirectionasthepositiveY-axis,andtheintegrityrateofthetestblockastheZ-axisgivestheintegritydistributionofcoalandrockmassalongthemainfracturingsurfaceinducedbyhydraulicpressureshowninFig.6.Inthefigure,thefailuretrendofthetestblockfromtheupperrightcornertothelowerrightcornerisrelativelyintegrated.Intermediatecoalaffectedbytheblastingmakescrackspropagateanddevelopfurther,leadingtothemostseriousfailureatthecenter.Becauseofthewaterinjectiondrillhole,thewaterpressuregeneratesweakplanesintheupperpartofthetextblockandthusitbreaksmoreeasilyincomparisontothelower.Thetestblocknaturallysplitsalongthemainrupturesurfaceinducedbyhydraulicpressureunderthelightershock,andthecrackpropagationshapeofhydraulicfracturingafterwaterpressureblastingisshowninFig.7.Underthefracturingeffectofsevenwaterinjections,thehydraulicfracturepropagatesfully.Cracksappearonbothsides,whichonthebottomandtopofthetestblockextendto1–2cmawayfromthesurface.Themainrupturesurfaceinducedbythehydraulicpressureisovalinshapeandsplitstheentiretestblock(Fig.7b).Theweakeningeffectsonthestructuresaroundthedrillholeinducedbyblastingarebasicallyconsistent;inotherwords,blastingcrackspropagatealongtheradialdirectionallaroundandtheirlengthsareabout12.8cm,butthemaincracksinducedbythehydraulicpressureextendalongthedirectionperpendiculartotheminimumprincipalstressmainlyunderthecontrolofthestressfield.Belowthebottomofthedrillhole,thehydraulicfracturepropagatesalongtheblastingcracks,leadingtoformationoftwofailuresurfacesinducedbyhydraulicfracturing.However,asthecracksextend,thedistancebetweenthet