本科生畢業設計（論文）題目：陳四樓煤礦2.4Mt/a新井設計綜采工作面過斷層技術研究摘要本設計包括三個部分：一般部分、專題部分和翻譯部分。一般部分為陳四樓煤礦2.4Mt/a新井設計。陳四樓煤礦位于河南省永城市境內，交通便利。井田走向（南北）長約13km，傾向（南北）長約6.7km，總面積為61km2。主采煤層為二2煤，煤層傾角為8~23，平均傾角11，平均煤厚為3.5m。井田地質條件較為簡單。井田工業儲量為28207萬t，可采儲量為20454萬t。礦井設計生產能力為2.4Mt/a。礦井服務年限為65.56a，涌水量較大，礦井正常涌水量為894m3/h，最大涌水量為1087m3/h。礦井瓦斯相對涌出量為0.57m3/t，絕對涌出量為2.0m3/min，為低瓦斯礦井。井田開拓方式為立井兩水平開拓，暗斜井延伸。采用膠帶輸送機運煤，采用礦車進行輔助運輸。礦井通風方式為兩翼對角式通風。礦井年工作日為330d，工作制度為“三八”制。一般部分共包括10章：1、礦區概述與地質特征；2、井田境界和儲量；3、礦井工作制度、設計生產能力及服務年限；4、井田開拓；5、準備方式——帶區巷道布置；6、采煤方法；7、井下運輸；8、礦井提升；9、礦井通風與安全；10、設計礦井基本技術經濟指標。專題部分題目是綜采工作面過斷層技術研究，主要是研究了綜采工作面過斷層的方法及相關頂板管理控制技術，對綜采工作面過斷層技術做了全面的陳述。翻譯部分主要內容是關于水壓控制爆破用于水力致裂技術用來增加煤巖體孔隙率的研究，英文題目為：Hydraulicfracturingafterwaterpressurecontrolblastingforincreasedfracturing關鍵詞：立井；兩水平開拓；采區；兩翼對角式通風

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礦區概述及井田地質特征 頁英文原文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