本科生畢業(yè)設(shè)計（論文）題目：許疃煤礦1.2Mt/a新井設(shè)計離層分區(qū)注漿減沉技術(shù)在許疃煤礦應(yīng)用探討本科生畢業(yè)設(shè)計學(xué)院：礦業(yè)工程專業(yè)：采礦工程設(shè)計題目：許疃煤礦1.2Mt/a新井設(shè)計專題：離層分區(qū)注漿減沉技術(shù)在許疃煤礦應(yīng)用探討畢業(yè)論文題目：許疃煤礦1.2Mt/a新井設(shè)計畢業(yè)論文專題題目：離層分區(qū)注漿減沉技術(shù)在許疃煤礦應(yīng)用探討畢業(yè)論文主要內(nèi)容和要求：根據(jù)采礦工程專業(yè)畢業(yè)設(shè)計大綱，本畢業(yè)設(shè)計分為一般部分、專題部分和翻譯部分，具體包括：1、一般部分：許疃煤礦1.2Mt/a新井設(shè)計，主要內(nèi)容包括：礦井概況、礦井工作制度及設(shè)計生產(chǎn)能力、井田開拓、首采區(qū)設(shè)計、采煤方法、礦井通風(fēng)系統(tǒng)、礦井運(yùn)輸提升等。2、專題部分：離層分區(qū)注漿減沉技術(shù)在許疃煤礦應(yīng)用探討。3、翻譯部分：完成近3-5年國外期刊上與采礦或煤礦安全有關(guān)的科技論文翻譯一篇，要求不少于3000字符。大學(xué)畢業(yè)論文答辯及綜合成績答辯情況提出問題回答問題答辯委員會評語及建議成績：答辯委員會主任簽字：年月日學(xué)院領(lǐng)導(dǎo)小組綜合評定成績：學(xué)院領(lǐng)導(dǎo)小組負(fù)責(zé)人：年月日

摘要本設(shè)計包括三個部分：一般部分、專題部分和翻譯部分。一般部分為許疃煤礦1.2Mt/a新井設(shè)計。許疃煤礦位于安徽省宿州市，地處平原，土地肥沃，農(nóng)作物生長良好。井田南北走向長6.27~6.47km，東西傾向?qū)?.11~3.73km，井田面積約19.94km2。井田內(nèi)主要可采煤層72煤層，傾角6.6~15.5°，平均厚度3m。礦井工業(yè)儲量為123.56Mt，可采儲量為85.74MtMt，設(shè)計服務(wù)年限54.9a。礦井正常涌水量為1050m3/h，最大涌水量為1660m3/h。礦井相對瓦斯涌出量為22m3/t，最大絕對瓦斯涌出量為64.83m3/min，屬高瓦斯礦井。煤層屬可能自然發(fā)火煤層，煤塵有爆炸危險性。根據(jù)礦區(qū)及井田地質(zhì)條件，設(shè)計采用立井單水平開拓方式。上山布置帶區(qū)，斷層上盤布置采區(qū)，全井田共劃分為四個帶區(qū)，一個兩翼采區(qū)，一個單翼采區(qū)。軌道大巷、膠帶機(jī)大巷和回風(fēng)大巷根據(jù)服務(wù)年限布置在煤層或巖層。本礦井為高瓦斯礦井，設(shè)置專用回風(fēng)井巷，并預(yù)掘底板瓦斯抽排巷進(jìn)行瓦斯卸壓抽放，礦井通風(fēng)方式采用中央并列式。針對涌水量大，大巷均向井底車場微斜自然排水，下山上行開采，后期向采空區(qū)排水。首采區(qū)帶區(qū)式準(zhǔn)備，工作面設(shè)計長度220m，采用綜合機(jī)械化采煤工藝。礦井年工作日為330d，晝夜凈提升時間為18h。礦井采用“四六”制工作制度，三班生產(chǎn)，一班檢修。生產(chǎn)班每班完成2個采煤循環(huán)。循環(huán)進(jìn)尺為0.8m，日產(chǎn)量為4243.54t。礦井煤炭采用膠帶輸送機(jī)運(yùn)輸，輔助運(yùn)輸采用DLZ110F柴油機(jī)單軌吊。主井采用一對12t底卸式箕斗提煤，副井采用多繩摩擦式提升機(jī)提升一窄（1.02）一寬（1.67）罐籠。專題部分題目為：離層分區(qū)注漿減沉技術(shù)在許疃煤礦應(yīng)用探討。在綠色開采及科學(xué)采礦理念的指導(dǎo)下，結(jié)合許疃煤礦覆巖特征及“三下”壓煤狀況，提出對高采出率下減緩地表下沉技術(shù)的探索。運(yùn)用數(shù)值模擬方法對離層區(qū)注漿減沉技術(shù)在許疃煤礦的使用進(jìn)行了分析探討。設(shè)計工作面長160m，關(guān)鍵層下巖層可達(dá)超充分采動狀態(tài)；離層區(qū)充填體分擔(dān)了部分覆巖載荷，分區(qū)煤柱應(yīng)力集中明顯減小；分區(qū)間跳采，因跳采出現(xiàn)的孤島工作面待兩側(cè)離層區(qū)充填穩(wěn)定后仍用離層區(qū)充填方法開采，數(shù)值模擬結(jié)果表明此方法可以有效減緩地表沉陷、提高資源開采率。翻譯部分主要講述了爆破卸壓的應(yīng)用現(xiàn)狀，包括地質(zhì)、巖石性質(zhì)、開采條件和爆破參數(shù)（炮孔布置、孔深、爆破載荷等），討論了爆破卸壓的優(yōu)勢并對其作為解決高采動應(yīng)力引起沖擊礦壓的效果進(jìn)行了評價，英文題目為：DestressBlastinginCoalMining–State-of-the-ArtReview。關(guān)鍵詞：許疃煤礦；立井單水平；瓦斯卸壓抽放；下山上行開采；單軌吊；F5逆斷層；變頻對旋式通風(fēng)機(jī)；離層區(qū)；數(shù)值模擬；爆破卸壓 ABSTRACTThisdesignincludesthreeparts:thegeneraldesign,themonographicstudyandthetranslation.Thegeneraldesignisabouta1.2Mt/anewundergroundminedesignofXutuanCoalMine.XutuanCoalMineliesinSuzhouCity,Anhuiprovince，wheresoilisflatandfertile.It’sabout6.27~6.47kmonthestrikeand3.11~3.73kmonthedip,withthe19.94km2totalarea.Themainaquifercoalseamis72coalseamwithanaveragethicknessof3m,andthedipis6.6~15.5°.Theprovedreservesofthiscoalmineare123.56Mtandtheminablereservesare85.74Mt,withaminelifeof54.9years.Thenormalmineinflowis1050m3/handthemaximummineinflowis1660m3/h.Theminerelativegasemissionquantityis22m3/t,andtheabsolutegasemissionquantityis64.83m3/min.Thecoalseamisfeasiblespontaneouscombustioncoalseamandthecoaldusthasexplosionhazard.Basedonthegeologicalconditionofthemine,thisdesignusesaverticalshaftsingle-leveldevelopmentmethod,whichdividedintofourbandsandtwodistricts,andtrackroadway,beltconveyorroadwayandreturnairwayaredifferentondifferentlifetime,arrangedinthefloorrockorcoalseam.Takingintoaccountofthehighgasemission,setupdedicatedroadwayforventilation,andexcavesbottomgasdrainageroadwaytoreliefgaspressure,mineventilationmethoduseCentralabreastventilation.inconnectionofbigwaterinflow,roadwaytiltstotheshaftbottomtofacilitatedrainage,ascendingminingisadoptedinthedistrictdip,takeadvantageofgoaffordrainage.Designedfirstminingdistrictmakesuseofthemethodofthestripdistrictpreparation.Thedesignlengthofworkingfaceis220m,whichusesfullymechanizedminingtechnology.Theworkingdaysinoneyearare330.Everydayittakes18hoursinliftingthecoal.Theoperationmodeinthemineis“four-six”withthreeteamsminingandtheotheroverhauling.Everyminingteammakestwoworkingcycle.Soeverydaythereare6workingcycles.Theadvanceofaworkingcycleis0.8m,andthequantityof4243.54toncoalismakedeveryday.Mainroadwaymakesuseofbeltconveyortotransportcoalresource,andoverheadmonorailtobeassistanttransport.Themainshaftusesadouble12tskipstoliftcoalandtheauxiliaryshaftusestwocage，oneis1.02mandtheotheris1.67m.Themonographicstudyentitled“ApplicationofisolatedsectiongroutingtechnologyforoverburdenbedseparationspaceinXutuancoalmine”.Undertheguidanceofconceptofgreenminingandscientificmining,inconnctionofcharacteristicofXutuan,exploringawaytoreducesubsidencewithahighrecovery.Studidbynumericalsimulation.Thelengthofwokingfaceis160m,rockstatumunderthekeystatumcanbefullmining;intermsofbackfillsharessomestress,coalpillarstresswassignificantlyreduced.skip-miningamoneisolatedsection,islandminingfacewasminedafterstabilityofbothsidesofgob.Thenumericalresultsshowthatthismethodcaneffectivelyreduceminingsubsidence,increasethecoalrecovery.Thetranslatedacademicpaperpresentsastate-of-the-artreviewofdestressblastingincoalmining.Informationsuchasgeology,rockproperties,miningconditionsaswellasblastingparameterssuchasblastholelayout,holelength,explosiveloadingetc.arepresented.Thepaperdiscussesthemainbenefitsofdestressblastingandtheevaluationofitseffectivenessasameasuretoovercomethechallengesofhighmining-inducedstressescausingcoalbumpsandrockbursts.Thetitleis“DestressBlastinginCoalMining–State-of-the-ArtReview”.Keywords:Xutuancoalmine;shaftsingle-leveldevelopment;gasdrainageandreliefgaspressure;ascendingmininginthedistrictdip;overheadmonorail;F5reversefault;rotatingfanwithfrequenceconvision;overburdenbedseparationspace;numericalsimulation;DestressBlasting

目錄一般部分1礦區(qū)概況與井田地質(zhì)特征 頁英文原文DestressBlastinginCoalMining–State-of-the-ArtReviewPetrKonicek1,*,ManiRamSaharan2,HaniMitri31InstituteofGeonicsAcademyofSciencesoftheCzechRepublic,Studentska1768,70800Ostrava-Poruba,CzechRepublic,2CentralInstituteofMining&FuelResearch(CIMFR),SeminaryHills,Nagpur,India,3McGillUniversity,Montreal,Quebec,CanadaH3A2A7Abstract:Coalmineworkingscontinuetofacethechallengesofcoalbumpsandrockburstscausedbyhighmining-inducedstressesduetohighoverburdenpressuresassociatedwiththeextractionofbrittle,lowstrengthcoalseams.Despiteofthefactthatdestressblastinghasbeenappliedforalmostacentury,itisstillnotapopularchoice.Thispaperpresentsastate-of-the-artreviewofdestressblastingincoalmining.Informationsuchasgeology,rockproperties,miningconditionsaswellasblastingparameterssuchasblastholelayout,holelength,explosiveloadingetc.arepresented.Thepaperdiscussesthemainbenefitsofdestressblastingandtheevaluationofitseffectivenessasameasuretoovercomethechallengesofhighmining-inducedstressescausingcoalbumpsandrockbursts.Keywords:Mining,Coal,DestressBlasting1.IntroductionItiselementarybutimportanttoillustratethatanundergroundexcavationinitiatesaprocessofreequilibrium,whichleadstothegenerationofstressesaroundtheexcavationinamannerthatfreesurfacesbecomeplanesforprincipalstressesandexperienceabi-axialstateofstresscondition.Theexcavationboundariesmayexperiencedamageeffectsduetostressesandtheseeffectsforcoalminescanbedislocationofrockreinforcement,interbedcrossoveroflaminatedroofrockmass,cutterfailure,floorheaveand/orrockburst/coalbump(Fig1).Thesedamagingeffectsarepresentedintheorderoftheirseverityaccordingtothestresslevel,correspondingstrength(uniaxialandpoly-axial)atthepointofconsiderationofthestressloading.Excessofthestresslevelincomparisontothestrengthandtherateatwhichtheexcessisattainedduringthere-equilibriumprocessismanifestedintothedifferentdamagingeffectsasillustratedinFigure1.Afasterrateinobtainingexcessstresseswillresultintorockburst/coalbump.Occurrenceofthisexcessstressoveragreaterareawillincreasetheseverityofthedamagingeffects.Further,partoftheexcavationexperiencesstressconcentrationandanotherexperiencesstressrelaxationduetotheshapeoftheopeningandinsitustressdirections.abcdFig1.(a)RockboltdislocationinanIndiancoalmine;(b)InterbedcrossoverinacoalmineofSouthAfrica[1];(c)CutterrooffailureinanUScoalmine[2];(d)RockburstinaGermancoalmine[3].Pastresearchformeasurementofstresses,understandingofstressesandpredictionofthetimingwhenandtherateatwhichthestresseswillbeinexcessofthestrengthhasbeenamixedsuccess.Theminingprocesshas,inthemeantime,becomefaster,largerandbeingdoneatdeeperlevels.Itisthusnecessarythatprotectivemeasuresbeevolvedtodealwiththedamagingeffectsofexcessivestresses.Figure2illustratesdifferentmethodsevolvedtodealwiththedamagingeffectsofexcessivestressesanddistressblastingisoneoftheoldestandproactivemeasuresamongsttheothermethods[4].Themechanismofdestressblastingisnotwellunderstooddespiteoftheapplicationofdestressblastinginawiderangeofminingconditionsandobjectives.Thepaperpresentsvariousconditionsforwhichdestressblastingisappliedfordeepcoalminesanddiscussesthepossibilitiestofurtherimprovethemethod.Theapplicationofdestressblastingisaimedintothezonesofstressconcentrationinsuchamannerthatthestressconcentrationzoneshiftedinteriortotherockmassthusleavingaprotectivebarrierbetweentheworkforceandthestressconcentrationzone.ThismechanismofdestressblastingisillustratedinFigure3,whichdemonstratethatdestressblastingshiftsstressconcentrationzoneawayfromtheactiveworkingfront.Fig.2.Methodstoreducedamagingeffectsofexcessivestresses[4]Fig.3.Geomechanicseffectsofdestressblasting[5]2.NaturalandminingconditionsHardcoaldepositsaremostlycomplexsedimentarysequencescontainingcoalseams(multiseamdeposits)inUpperPaleozoicage.Rocksbetweencoalseamscompriseshale,mudstones,siltstones,sandstonesandconglomerates.Thicknessofcoalbearingstratarangesfromhundredstothousandsofmeters,whereasthethicknessofcoalseamsvariesfrom1totensofmeters.Thefeaturemostcommonwherecutterrooffailureorfloorheaveoccursisthepresenceofthinlylaminatedroof/floor.Thefeaturemostcommontoseamsinwhichrockburstoccuristhecloseproximitytoastrong,thickandrigidstratum[3].Thesestrataconsistofsandstonesandconglomeratesinmostcoalfieldsandinrarecasestheyconsistofothertypesofgeologicalmaterialsandcanbedefinedascompetentmassiveelasticrock[6].TypicalexamplesofrockburstpronestrataaredescribedinFig4.SummaryofthebasicrockpropertiesofcarboniferousrocksisillustratedthroughTable1[3,7].Itisalsoimportanttounderstandthatcoalbearingstratahaveverydifficultstructuraltectonicpattern[14]withverycomplicatednaturalstressfieldandcombinationofthesecausesstressdamages[7,8,9,10].Fig.4.Typicalpropertiesofcarboniferousrockmasswithcompetentrocklayers(A)LazyColliery(theCzechpartofUSCB);(B)Germany[11];(C)ChinakuriColliery(India)[12]Table1.Rockproperties*RockUCS[MPa]RQD[%]Bedthickness[m](competentrocks)Coal10–30--Mudstones35–65--Siltstones40–15060–905–10Sandstones50–17060–9010–100Conglomerates40–14060–905–20*GeneralizeddatafromCzech,German,Indian,Polish,UkraineandUSACollieries[3,7,11,52]Miningconditionsinfluencetherockmassresponseandstressconcentration.Someoftheseconditionsarelistedbelow.?miningwithinmorethanonecoalseamsseparatedtoeachotherby3mtoabout100m,?extractionthicknessandsizeoftheopenings,?protective/unminedpillarsincoalseams,?partunminedoverlyingseams,?advancerateofmining,?differentadvancedirectioninoverlyingseams,and?improperlysuperimposedmininglayoutsinmulti-seamminingTypicalexampleofcomplicatedmininghistoryispresentedinFig.5,whichwaspublishedbyDvorskyetal.[47].Figure5representstimesequenceofmininginareaof4thminingblockinCSACollieryintheCzechpartoftheUpperSilesianCoalBasin(USCB).TheschemeofmininginthelevelofseamNo.530whichwasminedwithmanyoverlyingseamsindifferentdirections(Fig.5showsonlyfourofthem)isillustrated.Overlyingseamshadmanyunminedpillarsthatwereleftinthecentralpartoftheminingblockduetoatectonicfaultoccurrence.Theminingconditionswerefurthercompoundedduetochangingofminingdirectioninwestandeastpartofminingblock.ThiscomplicatedminingsituationtogetherwithverydifficultnaturalconditionscausedmanyrockburstwhileminingtheseamNo.530[47,15].Fig.5.Schematicmapoftimesequenceofminingofparticularlongwallsinareaof4thminingblock(seamNo530)ofCSACollieryintheCzechpartoftheUSCB;adjustedafter[47].Numerousminingcasestudiesofexcessivedamagesfrominducedstressescanbepresentedfrommanyminingregionsacrosscontinents,suchasAustralia[16],CzechRepublic[,15,17,18,47],Germany[3,11,19,20],Poland[21,22,23,37],USA[24],China[25,26]andIndia[27].3.DestressblastingasproactivemeasureDestressblastingincoalseamsorimmediateroofandfloorrockmasshasbeenadoptedtomanagecutterrooffailure,floorheaveandrockburst/coalbump.Theobjectivehasbeentoshiftexcessiveinducedstressestotheinteriorrockmassandtoprovideaprotectivebarriersurroundingtheexcavation.Threetypicalconditions,forwhichdestressblastinghasbeenadopted,areillustratedinFigure6.Theseusedestressblastingtoavoidcutterrooffailure,floorheaveandrockburst.MajorprincipalstressforthecasesshowninFigure6ishorizontalexceptforthecaseoflongwallminingwheremajorprincipalstressfromverticaldirectionisthecauseofconcern.Thesecasestypicallyusefarthestonethirdlengthoftheboreholechargedwithpermittedexplosive(singlecartridgepermetreofthechargelength)andboreholelengthdesignedsuchthattheexplosivecolumnbeginsatleast3mor1.5timestheexcavationheightfromtheboreholecollar[3].Theconditionunderwhichdestressblastingisrequiredandthelocationofdestressblastingisdeterminedfromdrillingrateandnoiseoftestdrillholes.Theeffectivenessofdistressblastingismeasuredfromchangeinsupportpressureandrateofconvergenceofroof/floorrockmass.Successfulapplicationofdestressblastingundersuchconditionsrequiresthatitshallbepracticedonregularbasisandbeapartofroutineminingcycle.Kexin[25]andXiaetal.[26]describeapplicationofdestressblastingtocontrolfloorheavefordeepcoalminesinChina.ThedestressblastinginvolveapatternandobjectiveconsistentTable2–parametersofboreholepatternfordestressblastinginthetestgallery[25]LayoutBoreholeChargingTestsectionpatternRowspacing,mToespacing,mColumnspacing,mSpacing,mDepth,mOrient-ationCharging,mMudstemming,m12row,3holeinflowerpattern4.7┴towallLeft1.6Left3.1Right1.9Right3.822deephole,1shallowholeDeephole4.2Deephole1.5Deephole2.7Shallowhole3.2Shallowhole0.7Shallowhole2.532row3holeinflowerpattern4.10.9-1.83.2-2.342linerow4.30.4-1.23.9-3.1withtheFigure6(b).DetailsofthepatternreportedbyKexin[25]isgiveninTable2.Thedestressblastingprogramreportedtobeasuccessinthemine.(a)Systemofdestressblastingtolimitcutterrooffailure(b)Systemofdestressblastingtolimitfloorheave(c)SystemofdestressblastingtolimitrockburstingatedrivingandlongwallminingFig.6.DestressblastingasproactivemeasurefordifferentobjectivesDestresscoalblastingissimilarlyusedtoalleviaterockburstsproblemsinPolishandCzechCollieriesbutalsoinGermancollieriesinthepast[18,19,28,29,30,31,32,33].Atypicaldestressblastingpracticeset-upisshowninfig.6(c)[29].Lengthofboreholesusedfordestressblastingdependsonsizeofprotectiveareawhichiscreatedaheadofafaceandthisisafunctionofthicknessofcoalseam,sizeofpillars,miningdepthandlocked-instressesinimmediateroofrocks(principlesarepresentedinFigure3).InPolishcollieries,lengthofboreholesisusuallyupto10m,diameterofboreholesdonotexceed80mm(usually42mm).Generallywecanquotethatsmallcharges(max.2.5kgsafetyexplosiveperborehole)areusedforboreholesindicatingexcessivestressstate.However,consumptionofblastingmaterialon1moflongwalladvanceisreportedabout80kg[28].Combinedsystemisfrequentlyusedindriving–destressblastingandcutblastingtogetherwherelengthofboreholesandexplosivechargearesmaller[28],lengthofboreholesfrom1.2to2.4mandexplosivechargeisfrom300gto1200gperborehole.Maximumwaitingtimeafterdestressblastingincoalseamis30minutes.InCzechCollieriesthelengthofboreholeislarger(upto20m),diameterofboreholes(42mm)andspacingofboreholes(max.5mindrivingofroadways,max.15minlogwallface)arestrictlygiven.Explosivechargeislarger(from2.5to7.5kgperborehole,i.e.50%–60%lengthofborehole).Maximumweightofexplosivechargeis180kgperdestressblastingstage.Combinationofdistressblastingincoalseamsanddestressdrillingaresometimesused[45];indrivingdestressboreholesinthefaceanddestressblastinginsidesofgates;inminingdestressboreholesfromgatewaysandtherestofthelongwallface–destressblasting.TypicalexampleofdestressblastinginCzechcollieriesispresentedinFigure6(c).InGermancollieries,destressdrilling(orslotting)ispreferredoverdestressblastinginmostcases.Rockburstphenomenaareobservedincoalseamsonly,anddestressdrillingisbelievedtobemoreeffective[46].ItisnoteworthythatthethicknessofcoalseamsinGermancollieriesgenerallydoesnotexceed3.5m.Generally,coaldepositsarefoundinmulti-seamseparatedfromeachotherby3m(termedascontiguousseams)tofewtensofmetersandtheyworkedinsequencefromtoptobottomexceptcontiguousseams.Oftenenough,partoftheupperseamisnotmineableandisletbehind.Miningoftheseambelowtheunminedportionoftheupperseammayposestrainburstinghazards.Suchasituationdemandstheapplicationofdestressblastingpriortotheminingofthelowerseam[e.g.2,35,47].Figure7.Simplifiedmodelofdestressblastingapplication[36]ApplicationofdestressblastingundersuchconditionshasbeeninpracticeinCzech[36,45,47,48]andPoland[22,23,28]andistermed"preconditioning"asdestressblastingispracticedmuchearlierthanmining.ThesimplifiedconceptualmodelofdestressblastingapplicationaspreconditioningisshowninFigure7[36].Thus,twomaintypesofrockburstsaredistinguishedaccordingtotheiroriginandmechanism.Theyare:rockburstinitiatedinthecoalseamoritsvicinityandrockburstinitiatedoutsidethecoalseam,mostlyinhighlycompetentroof.Toprotectagainstrockburstsinthecoalseam,activemeasuresareappliedinthevicinityofmineworkings,whereastoeliminateunfavourablestressconditionsoutsidethecoalseamitisnecessarytoapplypassiveprotectionofpotentiallyendangeredmineworkings.Wecangenerallydescribethepreconditioningsystemasasystemoflongholeswhicharedrilledinadjacentrocksofcoalseams.Preconditioningisdesignedaccordingtothefollowingspecifications[36].?Boreholesdrilledusuallyfromthegates.?Boreholesdiameter75–105mm.?Inclinationofboreholesupto+30°.?Spacingofboreholes5–12m.?Pneumaticchargingofexplosivesintoboreholes(incartridges).?Useofrockexplosives.?Simultaneousblastingwithoutdelay.?Blastingofexplosivesatadistanceof30mto100mfromthelongwallfaceintheregionofexpectedstressconcentration.Maximumwaitingtimeafterdestressblastinginadjacentrocksdependsonthedilutionofblast-inducedfumesinthemineandregisteredseismicactivity.Waitingtimeisfrom45to60minutes.Destressblastinginadjacentrocksofhardcoalseamsisnotthemostcommonlyusedsystemofcoalrockburstprevention.DestressblastingasarockburstcontroltechniquecomesfromdeepSouthAfricanoremines.Wecangenerallydescribemaingoalsofdestressblastingas:?Softeningofthecompetentrocklayersandreducingtheireffectivemodulusofelasticity,?Stressrelease.UsingsystemintheCzechCollieries,whichexampleispresentedbelow,isauniqueEuropeansystemindifficultstressconditionsinrockmasswecandescribeitwidely.Thesystemofdestressblastinghasbeenusedfor30yearsandwithincreasingminingdepths,ithasgainedimportance[36].AnexampleofdestressblastingaspreconditioningispresentedinFig.8whichhasbeenappliedinCSAcollieryoftheCzechRepublic[17].Theproperdestressblastingdrillholesweredrilledupwardsfrom(+20o)to(+28o)fromcoalseamlevelNo530locatedwithindepthrangeof860mupto890mbelowEarthsurface.Thelengthsofholesvariedfrom30mto80m.Inviewofdesignedparametersandthedestressblastingtasktheboreholediametersof75mmand93mmwereselected.Perpendiculardistancebetweenthedrillholesof(1)and(2)was10mupto15mandbetweenthedrillholesof(3)was10matmaximum.Thedrillholebottomsweresituatedatadistanceofabout30mabovetoppartofcoalseamNo530.Fordrillholestheplasticexplosiveinchargesaswellaspneumaticsandstemmingwereapplied.Thelengthsofparticularchargesvariedfrom15mupto50mandthelengthsofsandstemmingfrom15mupto30m.Allchargesineachstageweresimultaneouslyfiredwithoutusingdelays.Weightofparticularchargesvariedaccordingtoapplieddiameterandlengthofdrillholefrom60kgupto400kgperhole.Inparticularstagesthegroupsof2–6drillholeswithtotalchargesof552kgupto1440kgwereblasted.27stagesofdestressblastingwererealizedduringtheextractionoflongwallNo14735,i.e.fromNovember2003untilJune2004.Atotalamountof27,960kgexplosiveswasblastedin120drillholes.Inallstagesagreaterseismicenergywasreleasedthanitwouldcorrespondtoworkingperformedbyexplosiveatspecificphysical-mechanicalconditions.SimilarsystemofdestressblastingisusedinPolishcollieries[23,28,37],lengthofboreholesisintherangeof12to60mbutweightofexplosivechargeissmaller(accordingtolengthofboreholes40–150kg).Spacingofboreholesislarger(20–40m).Sometimesthegoalistocreatefracturesaroundtheblastedholes.DirectionalfracturingtechniquehasbeendevelopedinPoland[49,50].Thistechniqueisbasedontheconceptofhydraulicfracturingbuthasadjustmentfordestressblasting.Theobjectiveistocreatefracturesperpendiculartoboreholeaxis.MaximumwaitingtimeafterdestressblastingismuchlongerthaninCzechcollieries(uptoseveralhours).Fig.8.SchemeandsituationofdestressblastinginareaoflongwallNo14735inseamNo530atCSAColliery[17]4.EvaluationofeffectivenessProperlydesignedandrealizeddestressrockblasting(locationandspacingofboreholes,diameterofboreholes,lengthofcharge,numberoffiredboreholes,totalexplosivescharge,etc.)shallreducethestrengthanddeformationpropertiesofrockmassandthusshifthighstressconcentrationfartherinteriorintotherockmass.Evaluationofeffectivenessofdestressblastingisthusattemptedusingdifferentapproaches.Wewilltakeherealibertyofdescribingtheeffectivenessevaluationapproachasbeingdonefornon-coalminestooinordertodevelopabetterapproachforcoalmineapplications.Effectivenessfordestressblastingforthecaseofcutterfailureismeasuredfromvisualobservation.Incaseoffloorheave,theeffectivenessofdestressblastingismeasuredintermsofdecreaseinrockmassdeformationanddeformationrate.Kexinetal[25]andXiaetal.[26]describedecreaseinrockmassdeformationaftersuccessfulapplicationofdestressblastinginaChinesecoalmine.Figure9illustrateslongtermmeasurementofsidewallsandfloormovementcharacteristicsbeforeandafterdestressblastingintheChinesecoalmine.Variousattemptshavebeenmadetoascertaineffectivenessofdestressblastingasappliedtoalleviaterockburstproblemsandsomeofthemaredescribedbelow.Fig.9.Convergencemonitoringinacoalmineroadway[25]Changeinstressparametersbeforeandafterdestressblasting[35,38,39]andmodulusparameters[40,41]hasbeenmonitoredbothincoalandnon-coalminesasitisbelievedthattheobjectiveofdistressblastingistoreducethecriticalstressparametersandinducereductioninmodulusvaluessothattherockmassshallnotcarrycriticalstresslevel.Fig.10representsmeasurementofstresschangeduetodistressblastingintabulargolddepositsinSouthAfrica.Suchmeasurementsaretroubledwithinexplicableresults.Attemptshavealsobeenmadetocharacterizetheeffectivenessofdestressblastingbythecalculationofseismicenergyreleasedconcurrenttodestressblastingapplicationasitisconceivedthatreleaseofhigherenergythencontainedbytheexplosivesisamanifestationofreleaseofstrainenergystoredintherockmass[36,42].Theproblem,however,withtheapplicationofthismethodologyisthatmajorityofrockburstsareconcurrenttotheblasting,irrespectiveofroutineblastingordestressblasting.Stressreleaseisevaluatedusingcalculatedseismiceffect–SE[51,42].ItisbasedonstatisticalinterpretationofthedataofSEdistribution[42].Thedegreeofstressreleaseduetodestressblastingcanbedivided,onthebasisofSEcalculation,intoinsignificant,good,verygood,extremelygoodandexcellent(seeTable3).TheSEofdestressrockblastingistheratioofseismicenergyreleasedintherockmasswhenblastingtotheconsideredenergyoftheparticulardetonatedcharge:(1)whereESeis=seismicenergyinJ;Q=weightofexplosivechargeinkg;andK=2.1(forthenaturalconditionsofrockmassintheCzechpartoftheUSCB).ThereleasedseismicenergyintherockmassESeisisevaluatedfromseismicmonitoring.