美国煤矿锚杆安装质量改善研究外文文献翻译中英文翻译.docx

美国煤矿锚杆安装质量改善研究外文文献翻译中英文翻译.docx

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美国煤矿锚杆安装质量改善研究外文文献翻译中英文翻译

英文原文

IMPROVINGROCKBOLTINSTALLATIONSINUSCOALMINES

A.J.S.SpearingI;B.GreerI;M.ReillyII

ISouthernIllinoisUniversityCarbondale,IL,USA

IIFrazerandJones,Syracuse,NY,USA

SYNOPSIS

Thevastmajorityoftheroughly100millionrockanchorsinstalledinminesintheUSAeachyearuseresincartridges1.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.

Introduction

CoaliskeyforenergyproductionintheUSAandisactivelyminedin33states.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:

ØEachminemustdevelopandcontinuouslyupdateawrittenemergencypreparednessplan,whichmustberecertifiedbytheMSHAevery6months

ØMinesmustuseequipmentandtechnologythatiscommerciallyprovenandavailableifitcanimprovesafety

ØEveryminemusthave2trainedandexperiencedminerescueteamscapableofrespondingwithin1hourofanemergencyifrequired

ØMineoperatorsmustreportdangerousincidentsandaccidentstoMSHAwithin15minutesorfacefinesofuptoUS$60000

ØThecriminalpenaltycapwillberaisedtoUS$250000forthefirstoffenceandamaximumcivilpenaltyofUS$220000forflagrantviolationsofsafetyregulationsandstandards

ØWithin3years,allminesmusthavewirelesstwo-waycommunicationandanelectronicpersonneltrackingsysteminplace

ØTheMSHAisempoweredtoshutdownaminethathasrefusedtopayafinalorderpenalty

ØAscholarshipfundwillbecreatedtohelppayfortheeducationofmoreminingengineers,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:

ØTheloadbearingcapacityofthebolts

ØThelengthofbolts

ØTheboltstiffness

ØTheroofstrataandlocalgeology

ØThestressstate

ØTheuseofboltancillariessuchasstrapsorscreen.

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-speedresin