毕业设计-袁店一矿1.8Mt-a新井设计- 高渗透压松散破碎大断面失稳巷道修复技术

本科生毕业设计（论文）题目：袁店一矿1.8Mt/a新井设计高渗透压松散破碎大断面失稳巷道修复技术摘要一般部分为淮北矿业集团袁店一矿1.8Mt/a新井设计。袁店一矿西部边界为袁店断层为界，东至32煤层-1000m的水平投影线和39467500经线，南从杨柳~五沟断层及10煤层露头线，北到32煤层-1000m的水平投影线和区块登记边界。东西长约6.9~13.6km，南北宽1.2~3.4km，井田面积约37.22km2。主采煤层为8煤和10煤，其中8煤位于10煤上部，两煤层间距平均约80m，煤层倾角为5°～15°，平均约10°，属于缓倾斜煤层，煤层平均总厚为8煤3.5m、10煤3.6m。井田工业储量为214.47Mt，矿井可采储量148.23Mt。矿井服务年限为58.8a，第一水平服务年限28a。矿井正常涌水量为392m3/h，最大涌水量为584m3/h。矿井最大相对瓦斯涌出量10.08m3/t，属于高瓦斯矿井。井田开拓方式为立井两水平暗斜井延深集中岩石大巷开拓，井田采用采、带区式布置方式，共划分为三个采区，八个带区，轨道大巷、胶带机大巷和回风大巷皆为岩石大巷，布置在10#煤层底板岩层中。针对西二采区采用了采区准备方式，共划分3个回采工作面，并进行了通风、运煤、运料、排水、排矸、供电系统设计。针对8201工作面进行了采煤工艺设计。该工作面煤层平均厚度为3.5m，平均倾角15°。矿井年工作日为330d，工作制度为“四六”制，工作面采用长壁综采一次采全高采煤法。采用双滚筒采煤机割煤，往返一次割两刀。截深1.0m，每天六个循环，循环进尺6.0m，月推进度165m。大巷采用胶带输送机运煤，辅助运输采用电机车牵引固定矿车运料。矿井通风方式前期为中央分列式，后期为中央并列式通风。主井采用两套带平衡锤的16t箕斗提煤，副井采用一对1.0t矿车双层四车窄罐笼和一个带平衡锤的1.0t矿车双层四车宽罐笼运料和升降人员。专题部分题目是高渗透压松散破碎大断面失稳巷道修复技术。翻译部分主要内容是美国煤矿锚杆安装质量改善研究，其英文题目为：ImprovingRockboltInstallationsinUSCoalMines。关键词：袁店一矿；双立井；采区布置；中央并列式；大断面巷道；修复技术；锚杆性能

ABSTRACTThegeneralpartisanewdesignforYuanDianmine.YuanDianmineinwestisboundedYuanDianfault;Eastto32coal-1000mlevelprojectionlinesand39467500atwarp;Southfromawillow~5ditchfaultand10coalseamoutcroplines;Northto32coal-1000mlevelprojectionlinesandblockregistrationboundary.Thelengthoftheminefieldisabout6.9~13.6km,northandsouthwide1.2~3.4km,fieldwithanareaofabout37.22km2.The8#and10#isthemaincoalseam.Andthe8#isabovethe10#withaverticaldistanceofabout80m.Thedipangleofthecoalis5~15degreeandtheaverageoneis10degree.Theaveragethicknessofthecoalis3.5min8#and3.6min10#.Theprovedrecoverablereservesoftheminefieldare214.47milliontons,andtheminablereservesare148.23milliontons.Thedesignedproductivecapacityis1.8milliontonsperyear,andtheservicelifeofthemineis58.8years.Thenormalflowofthemineis392m3perhourandthemaxflowofthemineis584m3perhour.Therelativeminegasgushis10.08m3/t,Itisahighgasmine.Themineisadoubleleveldarktiltextendingdepthandconcentrationrockroadwaytodevelopandfullstrippreparation,whichdividedintothreeworkingareasandeightbandts,andtrackroadway,beltconveyorroadwayandreturnairwayareallrockroadways,arrangedinthefloorrockof10#coalseam.ThedesignappliesstrippreparationagainstthefirstbandofWestTwowhichdividedinto3stirpstotally,andconductedcoalconveyance,ventilation,gangueconveyanceandelectricitydesigning.Thedesignconductedcoalminingtechnologydesignagainstthe8201face.Thecoalseamaveragethicknessofthisworkingfaceis3.5mandtheaveragedipis15°.The“four-six”workingsystemisusedinthemine.Itproducesfor330daysayear.Theworkingfaceappliesfullymechanizedlongwallfull-heightcoalcavingmethod,andusesdoubledrumshearercuttingcoalwhichcutstwiceeachworkingcycle.Thedepth-webis1.0mwithsixworkingcyclesperday,andtheadvanceofaworkingcycleis6.0mandtheadvanceis165mpermonth.ThecentrallanewayusesBeltConveyortotransitcoal,andtrolleywagonsareusedforaccessorialtransportationintheroadway.Theventilationmodeofthismineisearlierstagewhichusingboundaryjuxtaposeformandlaterstagewhichusingcenterjuxtaposeform.Themainshaftusesdouble16tskipstoliftcoalwithabalancehammerandtheauxiliaryshaftusesatwinsnarrow1.0tfour-cardouble-deckcageandawide1.0tfour-cardouble-deckcagetoliftmaterialandpersonneltransportation.Thetopicofspecialsubjectpartsistherestorationtechnologyoflargesectionandloose-fracturedInstabilityroadwaywhichinhighseepagepressure.TranslationpartisabouttheuseageofcoalmineofUS,anddiscussestosetupamechanicalanchorsystemtoimprovetheperformanceofbolt.ItsEnglishtitleis“ImprovingRockboltInstallationsinUSCoalMines”.Keywords：Yuandiancoalmine;Doubleverticalshaft;Panellayout;Centerjuxtaposesventilation;Largesectionroadway;Restorationtechnology;Anchorperformance中国矿业大学2012届本科生毕业设计第英文原文IMPROVINGROCKBOLTINSTALLATIONSINUSCOALMINESA.J.S.SpearingI;B.GreerI;M.ReillyIIISouthernIllinoisUniversityCarbondale,IL,USA

IIFrazerandJones,Syracuse,NY,USASYNOPSISThevastmajorityoftheroughly100millionrockanchorsinstalledinminesintheUSAeachyearuseresincartridges1.About4.5millionoftheseboltsareinstalledusingamechanicalshellinadditiontotheresintocreateanactive(pre-tensioned)bolt.Over1millionoftheboltsarepassivecableboltsandtypicallyhaveaneffectivegroutlengthof1.2m,regardlessofthecablelength,whichcouldbeaslongas6m.Thesuccessfulperformanceoftheresingroutedboltsdependsonseveralparameters,includingtheannulargapbetweentheboltandholewall,whichshouldberelativelysmall,ideallyfrom3mmto5mm.Thisrequirement,combinedwiththehighviscosityoftheresin,producesahighback-pressurethatcancausetheboltbeinginstalledtobuckleornotbeinstalledtostandard.Itisthisback-pressurethatlimitstheeffectivegroutlengthwithpassivecableboltsandcausesthemechanicallyanchoredboltfailures(typicallycalled'spinners'wherethemechanicalshelldoesnotanchor).Thiscreatespotentiallyunsafeconditionsandwastestimeandmoney.Apurpose,builtrigwasusedtomimicundergroundinstallationsandrecordthebackpressuresduringfullscaleapplicationsinthelaboratory.Thisinformationwasused,andisstillbeingused,toreducethefailuresandsub-standardinstallationsbyproducingimproveddesigns.Inaddition,aflowmodelwascalibratedthatcanactqualitativelytoestimatetheback-pressuresandcanbeusedasacrudescreeningprocessbeforefullscaleprototypesarebuiltandtested.Todate,theresultsobtainedhavebeenusedtostoptheuseofamechanicalshellduetotheprovenhigherrateoffailures.Anew,improvedmechanicalshellisbeingfieldtestedandanothersystemisunderdevelopment.Theuseoftherigisthereforeongoingtodevelopimprovedmechanicalanchorsystems.Itistooearlyforrealdata;however,anecdotalevidenceseemstoindicatethatsignificantimprovementscanandwillbemade.Keywords:Rockbolt,performance,mechanicalanchor,resin,undergroundsupport,annulargap,installationpressure,back-pressure,resinports.IntroductionCoaliskeyforenergyproductionintheUSAandisactivelyminedin33states.Approximately90percentofthiscoalproductionisusedtogenerate50percentoftheUSA'selectricpower.CoalminingisresponsibleforoverUS$60billioninannualrevenue,andtheindustrydirectlyandindirectlysupportsover750000jobsintheUS2.AsFigure1shows,annualproductionhasrisenatasteadyratesince1960.In2007,about1.15billionshorttonsofcoalwereproducedfrom1438mines.612ofthesemineswereundergroundoperations,andtheyaccountedforabout31percentofthetotalcoalproduced3.Undergroundminingisofmoreconcernthansurfaceminingwhenconsideringcoalminesafety,forobviousreasonsasroofandribfallshavethepotentialtocauseseriousorfatalinjurytominers.Theweakroofstratatypicallylocatedaboveacoalseamarepronetoskinfailure,includingmassivefailureinsomecases.Over1500rooffallsoccureveryyearinUScoalmines4.Inaddition,however,thetightworkingconditionsalsomakeiteasyforaminertobecomepinnedbetweenapieceofmachineryandtheribifpropersafetyproceduresarenotfollowed.2005wastheyearwhentheleastfatalitiesoccurredonthecoalminestodate.In2006,however,thecoalminingindustrywasplaguedbytwomajordisasters;inJanuary2006anexplosionattheSagoMineinWestVirginiakilled12people,followedinMay2006byfiveminersbeingkilledinanotherexplosionattheDarbyMineinKentucky.InAugust2007,afurtherdisasteroccurredattheCrandallCanyonMineinUtahintheformofamassivecollapse,possiblycausedbyacoalbump,thatresultedinnineminersbeingkilledandafurtherthreemorefatalitiesduringrescueoperations.Asaresultofthesedisasters,CongressrapidlypassedtheMineImprovementandNewEmergencyResponse(MINER)Actin2006.Theprimary,relevantsupport-relatedprovisionsofthisAct,accordingtotheMineSafetyandHealthAdministration(MSHA),are:Eachminemustdevelopandcontinuouslyupdateawrittenemergencypreparednessplan,whichmustberecertifiedbytheMSHAevery6monthsMinesmustuseequipmentandtechnologythatiscommerciallyprovenandavailableifitcanimprovesafetyEveryminemusthave2trainedandexperiencedminerescueteamscapableofrespondingwithin1hourofanemergencyifrequiredMineoperatorsmustreportdangerousincidentsandaccidentstoMSHAwithin15minutesorfacefinesofuptoUS$60000ThecriminalpenaltycapwillberaisedtoUS$250000forthefirstoffenceandamaximumcivilpenaltyofUS$220000forflagrantviolationsofsafetyregulationsandstandardsWithin3years,allminesmusthavewirelesstwo-waycommunicationandanelectronicpersonneltrackingsysteminplaceTheMSHAisempoweredtoshutdownaminethathasrefusedtopayafinalorderpenaltyAscholarshipfundwillbecreatedtohelppayfortheeducationofmoreminingengineers,mainlyforMSHA.AccordingtotheNationalMiningAssociation(NMA),afederallobbyinggrouprepresentingmanymineproducers,themineshavereactedpositivelytothislegislation.Morethan150000newSelfContainedSelfRescuers(SCSR)havebeenintroduced;allmainescapewayshavelifelines;nearly1000refugefacilitiesthatcanprovide96hoursofindependentairhavebeencommissionedorareonorder;45newrescueteamshavebeenorarebeingtrained;andredundantcommunicationsystemshavebeeninstalled.OneoftheprovisionsoftheMINERActthatdoesdirectlyimpactrock-relatedsafetyisthatallunplannedrooffallsmustbereportedtoacentralMSHAofficebytelephonewithin15minutesofbeingdiscovered.MSHAdefinesanunplannedrooffallasafallthatisatorabovetheanchoragezoneinactiveworkingswhereroofboltsareinuse,orafall(rooforrib)inactiveworkingsthatimpairsventilationorimpedespassage.ThisinformationisthenrelayedtotherelevantMSHAdistrictoffice,whereadecisionismadeastowhetheraninvestigationisjustifiedandwhethertheareashouldbebarricadedofftokeepallpersonnelclear.Forthecoalindustry,MSHAisdividedinto11independentdistricts,allwithacentraldistrictofficeincloseproximitytothelocalcoalminingareas.Mostdistrictsalsohavelocaloffices,aseachminemustbethoroughlyinspectedfourtimesperannumbyMSHA,asidefromotherroutinevisits.RockfallsremainasignificantconcerninUScoalmines,asillustratedintheTablesIandII.RoofboltingisarequiredpracticeinallUScoalmines.SupportinUScoalminesisgenerallyclassifiedaseitherprimarysupport,secondarysupport,orsupplementalsupport.Primaryandsecondarysupportarespecifiedineachmines'roofcontrolplan,whichmustbeapprovedbyMSHA.Primarysupportisgenerallyrockboltsoranchorsthatareinstalledinthedevelopmentcycle.Secondarysupporttypicallyconsistsofcablebolts,trussesand/orstandingsupport.Supplementalsupportissupportinstalledinadditiontheprimaryandsecondarysupportwhenconditionsareworsethananticipated,duetoweathering,forexample,orforrehabilitationofanexcavation.Dependingontheparticularroofgeologyandthetypeandspacingofboltsused,thesupportprovidesskincontrol(keyblocksupport),suspension,beambuilding,orsupplementalsupport(whencableboltsaretypicallyusedinintersections).Thesupportdensityrequiredisinfluencedby:TheloadbearingcapacityoftheboltsThelengthofboltsTheboltstiffnessTheroofstrataandlocalgeologyThestressstateTheuseofboltancillariessuchasstrapsorscreen.Tang5statesthatimmediateroofgeologiescanbedividedintothreetypes:(A)Thedeflectionofeachstratumislargerthanthatofitsoverlyingstratum,andeachstratumdeflectsindependently(B)Somestratadeflectmorethantheoverlyingstratum(C)Thedeflectionofeachstratumislargerthanorequaltothatofitsunderlyingstratum.Theimmediateroofofcase(A)ismostcriticaltostability;therefore,anadequatelydesignedprimaryroofboltingsystemiscrucial.Additionally,theeffectofaxialloadingduetohorizontalstressesshouldbeconsideredinthedesignofsupportsystems.ThemostcommonlyusedbolttypeintheUSAisresinanchoredrebar.Astudy6foundthatastrongshiftinthecoalindustry'sboltpreferencehasoccurredinthelasttwodecades,withfullygroutedboltusageincreasingfrom40percenttowellover80percent,andmechanicalanchorboltsdecreasingfrom35percentto8percent.Adecreasingtrendinrooffallrateshasbeenobservedduringthisshiftinpreferencefrommechanicaltofully-groutedbolts,althoughtherearemanyfactorsthatmaybecontributingtothiseffect.Resingroutedrebarcanbeconsideredafarsuperiorsystemtothemechanicalanchorboltbecauseoftheloadtransfercapabilitiesandthehigheranchoragecapacityperunitlength,especiallyinweakstrata.Roofboltsystemsaredividedintotwocategories:passiveandactivebolts.Activeboltsaretensioneduponinstallation,andcanbeanchoredbyeitherusingatwo-speedresinoramechanicalshellwithresin.Passiveboltsareun-tensionedoninstallationandareusuallyfullygroutedwithresincartridges.Activeboltsaretypicallyusedinlaminatedstratafor'beambuilding'.Activeboltsusingmechanicalshellshavetwoadvantagesoverthetwo-speedresincartridgeoption:Innarrowseams,theforgedheadsusedwiththemechanicalshellactiveboltsprotrudelessfromthecoalroofthanthethreadedtwo-speedresinsystem.Thishasobvioussafetyadvantages.Inlong-termexcavations,theboltswithforgedheadsaremuchlesssusceptibletolong-termcorrosionthanthreadedbolts.Intersectionsareofparticularconcernregardingroofstabilitybecausethespanacrossthediagonalislarge,typically40percentmorethantheroomwidth.Thediagonalspancanbeevenlargerifthepillarcornersareroundedorincorrectlyedgedduringtheirdevelopment,orifthepillarcornersaredamagedduetostress.Approximately71percentofallrooffallsoccurinintersections,eventhoughtheyaccountforonly20to25percentofthetotaldevelopment,soafallis8to10timesmorelikelytooccurinanintersectionthananentryonaunitlengthbasis.Numericalmodelingandstatisticalanalysishaveshownthatalthoughfour-wayintersectionsare1.28timesmorelikelytofailthanthree-wayintersections,ittakestwothree-wayintersectionstoreplaceasinglefour-wayintersection.Thismakesthepotentialremedyofreplacingthree-wayswithfour-waysineffectiveinreducingthetotalnumberofrooffallsintheseareas7.Problemscanarisebecauseprimaryrockanchorsystemsarenotsuccessfullyinstalled100percentofthetime.Withamechanicalshellandresinbolt,theresultofafailureiseitheranon-tensionedbolt(commonlyreferredtoasa'spinner')oratotallyfailedinstallationthatrequiresanothercompleteinstallation.Thespinnerisoftentheresultofadamagedanchorshellleaf.Boththeseresultsareundesirablebecausetheycreatepotentiallyhazardousconditionsandincreasesupportcosts.Ithasbeenestimated8thataround2percentoftheresinboltswithmechanicalshellsarenotinstalledcorrectly.Basedontheannualusage,thisrepresentsabout90000bolts.Whenanyrockboltisinstalledthroughresincartridges,theeffectisthecreationofahighback-pressurethatcanbesignificantandcancreatefailures,especiallywhenamechanicalshellorcableboltisused.Foroptimumresinmixingandperformance,asmallannularspaceisneededbetweentheboltandthehole,typicallylessthan6mm(ideallyabout4mm).Aftertheholeisdrilled,thecorrectvolumeofresinincartridgeformisinsertedintheholeandtheboltisinserted,usingtheroofbolterchuck,throughtheresintothebackofthehole;theboltisthenspuntomixtheresinforthespecifiedtime.Iftheboltispassive,itisthenheldmotionlessuntiltheresinhassetandthechuckislowered,leavingtheboltinplace.Iftheboltisactiveandamechanicalshellisused,thespinningtomixtheresinalsolockstheshellinplace,sotheroofbolterstallsatthemaximumtorquesetonthemachineasthemechanicalshelllocks.AtypicaltwinboomroofbolterisshowninFigure2.Secondarysupportisinstalledmainlyinintersectionsbecauseofthelargereffectivespan.Theeffectivebondlengthwiththeresinisonly1.2m,asmentionedearlier,becauseoftheback-pressuresandtheflexiblenatureofthecable.Thesecablesareinstalledessentiallyaspassivesupports,andattemptstofitamechanicalshellontheendofthecablehavebeenunsuccessfulbecausetheincreasesinback-pressurecausethecablestobendandtheinsertiontofail.RockboltingmaterialsandancillariesintheUSAarespecifiedinASTMF4329.ThecoalminingindustryusesrebarwithtypicalpropertiesaslistedinTableIII.ThegradespecifiedinTableIIIreferstotheminimumyieldstressinimperialunits,asdefinedinASTMF432.Therefore,bydefinition,aGrade40steelhasaminimumyieldstressof40000psi(276MPa).ThesteelusedforcableboltsisgiveninTableIV.Thecableboltstypicallyusebulbs('birdcages')toassistwiththeresinmixingandfinalanchoring.TheresearchboltinstallationtestingapparatusThecausesoftheback-pressurearecomplexanddependmainlyontheannulusbetweentheboltandthehole,theresinviscosity,thefillers(bothquantityandsize),thecartridgeskin,andpossiblyeventheresincartridgestaples.Atotalinstallationfailureoccurswhentheinsertionbackpressureexceedsthebucklingstrengthofthebolt,whichtypicallybendsbeforeitiscompletelyinsertedintothehole.Smalllaboratorytestapparatusexiststoinvestigatesomeaspectsofresinboltinstallation,butisnotabletohandlerealisticboltandequivalentresinlengths,sotheresultsaremainlyqualitative.Inordertotrulyquantifytheinsertionproblems,acustomdesignedapparatuswasbuiltattheCoalResearchCenteratSouthernIllinoisUniversityCarbondale.Thisapparatusmeasuredtheback-pressurescreatedwhendifferentrockboltswereforcedthroughresincartridges.Theconditionscreatesignificantback-pressures,inthesamewayasasyringedoes,especiallysincetheresinmixisviscous.Theresincomponentofananchorcartridgehasaviscosityrangeoftypically200000to400000centipoise(mPa.s),about200000to400000timestheviscosityofwater.Research10wasconductedtounderstandandquantifytheissuescausingthefailures,improvecurrentdesigns,andtrytoestablishdesignparameterssuchthatthepercentageoffailurescanbereducedsignificantly,thusimprovingsafetyandreducingcosts.Thetestapparatus(Figure3)wasdesignedtoinstall1.2mrockanchors(cablesorbolts)intosteelpipeswithnominalinternaldiametersof25mmand35mm,whicharethetypicalholediametersusedinUScoalminesforrockanchoring.Thelengthselectedisacommon,effectiveresingroutlength(especiallyforcablebolts)anditkepttheoverallheightofthetestrigwithinmanageablelimitsbasedontheheightavailablefortherig.

Figure4isadiagramofthehydraulicsystemforthetestapparatus.Thecylinderishydraulicallypoweredandextendedatarateof150mm/sec.Thisisclosetotheactualinstallationspeedusedbyarockbolterunderground.Themaximumupthrustcapacityofthecylinderis5.5tons.ThehydraulicpowerpackwasborrowedfromanoldMTSloadframe.Theinstallationdistancewasmeasuredusingastringpotentiometer,andtheinsertionback-pressurewasrecordedasavoltageandconvertedtoaloadinthestandardmanner.ThetestregimeandprocedureThetestprocedurewassimpleandtheresultssurprisinglyrepeatable.Wherepossible,theresincartridgesusedwerefromthesamebatch,sothattheviscositywasasconsistentaswaspractical.Asteelpipe,1.2mlongwithaninternaldiameterofeither25mmor35mm(matchingtheboltholediametersdrilledunderground)isclampedinplace,andtheappropriateresincartridgeisplacedinthetube.Aboltisfittedintothesocketontheendoftheinsertioncylinder,andthecylinderisactivatedupwards,forcingtheboltintothesteelpipethroughtheresin.Afterbeingfullyinserted,theboltcanberotatedusingthemotorattachedtothecylinder,asshowninFigure5.Thisprocedurecloselymirrorstheactualundergroundboltinstallation.Thefollowingtestswerecarriedouttoquantifytheparametersthatinfluenceboltinsertionthroughtheresinandestablishwhichcombinationsofmechanicalshellsandboltsinstallreliably:Number5andnumber6rebarin25mmholes(mainlytocalibratetherig,checkontherepeatabilityofthetests,andobtainanideaoftheback-pressuremagnitudes)Parametertesting(resinviscosityandannulargap)Mechanicalshellswithnumber5rebarin25mmholesMechanicalshellswithnumber6rebarin37mmholesTheback-pressureswheninsertingatypicalcablebolt.Basedontheresultsfromtheproceduresoutlined,anewgenerationmechanicalshellwastestedthatcouldimprovetheloadperformance,diminishinstallationback-pressures,andpossiblyevenreduceproductioncosts.Alltestswererepeatedatleastoncetohelpensurereliablefindings.ResultsRepeatabilitytestsNumber5andnumber6rebarfeaturethemostcommondiametersusedinUScoalmines.Figure6givestheinsertionloads(back-pressure)resultsforthenumber6barsina25mmholewithastandardresin.ItcanbeseenfromFigure6thattheresultsarerepeatableandconsistent.Itisinterestingtonotethatafterabout1mofboltinsertion(0.2mfromfullinsertion),theforcerequiredisover1.6tons.Theboltdoesnotbuckle,however,becauseoftheshortlengthremainingoutoftheholeandtheresultinghigheffectivebucklingstrength.Sincethefailuresareduetotheback-pressurescausingtherockbolttobucklebeforeitcanbeinsertedintothehole,thebucklingstrengthofthemostcommonlyusedrebar(number6)wastested.Totalinstallationfailureswheretherebarbucklesduringinstallationarelesscommonthan'spinners',wheretheshellisdamagedduringinsertionthroughtheresincartridgeduetothepressure.Thebucklingstrengthofnumber5andnumber6rebarwasmeasuredatdifferentlengths,andtheresultsaregiveninTableV.ThespreadofresultsissignificantandismainlyduetothefactthatASTMF432specifiesonlyaminimumtensilestrengthandnotarange.Thisdatacanbeusedtodesignboltsystemsusingresintoreducethelikelihoodofatotalfailureoninstallation.Suchafailurewouldrequireanadditionalbolttobeinserted,wasting·bothtimeandmoneyandpotentiallyincreasingthesafetyhazard.InmostUScoalmines(exceptinthewestcoalfields),therebarextendslessthan1.5mfromthebolterchucktotherockboltholeintheroof,andthepressureoninitialinsertionisverylow,asthecartridgeislessthantheholelength(designedusuallytocreateafullcolumnbondinthehole,takingaccountoftheboltvolume).TheeffectofresinviscosityTheeffectofresinviscosityin25mmdiameterholes,usingnumber5andnumber6rebar,isshowninFigures7and8.Resincartridgesnormallyhaveviscositiesbetweenabout250,000cpsand450000cps.Toextendtheviscositiestested,someexpiredcartridgeswerefoundwithaveryhighviscosity.Theresultsareofinterestbecausethebackpressureincreaseswithincreasingviscositytoacertainlevel,andthentendstoreduce.Thereductioninback-pressurewhenusingtheextremelyhighviscosityresin(900000cps)wasnotanintuitiveresultandallthetestswererepeatedatleasttwice.Thisresultisdifficulttoexplainandisprobablyduetotherelativelycoarselimestonefillers,whichmaketheflowpropertiesoftheresincartridgemixmorecomplex.Itisapparentfromtheseteststhattheresinviscosityaloneisnotamajorcontributortotheinstallationbackpressure.TheeffectofresinportsTheannulargapishalfthegapbetweenthediametersoftheboltandthehole.Thegapisalsoconsideredtobeanimportantparameteraffectingtheback-pressureoninstallation.Whenmechanicalshellsareused,thegapbetweenthemechanicalshellandtheholeisclearlythelimitingfactor.Thedimensionsoftheshellplugaredictatedbytheperformancerequirementsoftheshell.Therefore,theonlywaytomakeadditionalpassagefortheresinisbymachiningflowgrooves(referredtoasresinports)intheshellplug.Resinportsinamechanicalshellplugarecriticaltothesuccessfulinstallationofboltswithmechanicalshellsthroughresinbecausetheyincreasetheeffectiveflowcross-sectionalareafortheresinduringinstallation.Theeffectoftheresinportsinshellshadnotbeenquantifiedinthepast.Figure9showstheplugsusedtoestablishtheeffect.Thefirstsetofplugshadnoresinports,thesecondwasastandardcommerciallyavailabledesignwithsixresinportsandthethirdsethadtwelveresinportstotrytofacilitatetheresinflowaroundtheshell.Threetestswereundertakenforeachplugdesign(withouttheleaves)using1.2mofequivalentresinfromthesameresinbatchina37mminternaldiameterhole(steelpipe).Eachplugdesignwastestedthreetimestoensureconsistentandrepeatableresults.Figure10showstheresults,andthedifferenceintheinsertionpressuresisdramatic.Basically,effectiveresinportsareessentialforsuccessfulinstallationsusingmechanicalshells.Theplugwithoutresinportsfailedeachtimeduringinstallation(thismeansthattheinsertionback-pressureexceededthebucklingstrengthoftheboltanditbent).Theshellswiththe6resinportshadinsertionloadsabove8.8kNandpeakedat15.7kN.Incontrast,theinsertionloadsusingthe12resinportshadloadsgenerallybelow9kNwithapeakofabout10.8kN.Resinportsarethereforeconsideredthekeytoreducingtheinstallationba