第二十五国际采矿地面控制会议外文文献翻译Word格式文档下载.docx

第二十五国际采矿地面控制会议外文文献翻译Word格式文档下载.docx

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NIOSH-PittsburghResearchLaboratory

Pittsburgh,PA,USA

ABSTRACT：

ThefirstInternationalConferenceonGroundControlinMiningopenedwiththetopicofpillardesign.Twoclassicpaperswerepresented,onebyBieniwskiandtheotherbyWilson.Unfortunately,thetwomethodsweresoradicallydifferentfromeachotherthatitwasnearlyimpossibletoreconcilethem.Addingtotheconfusionwerethemanyotherpillarstrengthformulas（suchastheSalamon-Munro,theHolland-Gaddy,andtheObert-Duvall,justtonameafew）thatwerealsoavailable.Littlewonderthatdiscussionsofpillardesigninthosedaysoftenendedwithanguishedcriesof“butwhichformulaistherightone?

”

Thepast25yearshaveseensubstantialprogressinthescienceofcoalpillardesign.Indeed,onetestamenttotheimprovementistherelativescarcityofpapersonthetopicatrecentConferences.Twofactorshavebeenlargelyresponsiblefortheprogressthathasbeenmade.Thefirsthasbeenthecollectionoflargedatabasesofactualcasehistoriesofpillarperformanceinavarietyofsettings,fromshallowroom-and-pillarminesthroughdeepcoverlongwalls.Thesehavemadepossiblethedevelopmentofempiricaldesignproceduresthatarecloselylinkedtorealworldexperience.Thesecondimportantfactoristhedevelopmentofsophisticatedcomputermodelsthatcanaccuratelysimulatepillarbehaviorandroof/pillar/floorinteractions.Together,thesetwolinesofresearchhaveledtoanewunderstandingofpillarmechanicsthatidentifiesthreemodesofpillarfailure:

•Sudden,massivecollapse,accompaniedbyairblast,forslenderpillars（width/height<

4）

•Squeezing,orslow,non-violentfailure,formostroomandpillarapplications（4<

w/h<

10）

•Entryfailureorbumpsfordeepcoverandlongwallapplications（w/h>

10）

Itisparticularlysatisfyingthattheinsightsgainedfromnumericalmodelsbroadlysupportthoseobtainedfromtheempiricalstudies.

Whilefarlesscontroversialthaninthepast,pillardesignproblemscontinuetoarise.Onerecentexampleispillardesignforhighwallmining.NIOSHhasjustreleasedasoftwarepackage,calledARMPS-HWM,whichemploysanumberofmodernpillardesignconcepts.Sincehighwallminingwebpillarsarelongandslender,thegreatestdangeristhatofasuddencollapse.ARMPS-HWMsuggeststwopossiblepreventionstrategies,onewhichconcentratesontheSFofthewebs,andtheotherwhichcreatesa“pressurearch”usingproperlysizedbarrierpillars.

Thepaperwillclosewithadiscussionofsomecurrentneedsincoalpillardesign,including:

•Updatingolderempiricalmethods,suchasALPS,wherechangesintechnology（newtypesofroofsupport,moredemandingventilationrequirements,fasterretreatrates）may

havemadesomeoftheoriginalcasehistoriesobsolete.

•Methodsfordeterminingsite-specificcoalstrengths,focusingonbeddingplanestrengthandotherfactorsthatmayeffectconfinement,asinputforbothempiricalandnumericaldesign.

•Improvedmethodsforevaluatingcoalpillarperformanceforenvironmentalissues,suchassurfacesubsidenceandhydrologicimpacts,whichconsidersuchfactorsasdepth,w/hratio,waterimmersion/drainage,andtimedependentseamstrength.

ACKNOWLEDGEMENT（ANDAPOLOGY）

Thetopicofpillardesignisoneofthemostimportantinthefieldofcoalminegroundcontrol,andthesubstantialprogressthathasbeenmadehasbeenduetothecollectiveeffortofmanyresearchersandpractitioners.Inabriefoverviewlikethisone,itwasonlypossibletomentionafewofthosewhohavemadeimportantcontributions.AsanapologytothemanywhosevaluableworkIwasunabletoinclude,Icanonlysaythatyouareinverygoodcompany.

INTRODUCTION

Babcocketal.（1981）,writingintheirsurveypaperfortheFirstConferenceonGroundControlinMining,tracedthescienceofpillardesignallthewaybacktoCoulombin1773.Duringtheensuingcentury,avarietyofresearcherstestedrockspecimensofavarietyofsizesandshapes.However,itwasnotuntil1911thatBunting（1991）proposedthefirsttruepillardesignmethodforcoalmines.Buntingdescribedthenecessityforpillardesignthisway:

"

Tominewithoutadequatepillarsupportwillresult,soonerorlater,inasqueeze;

theinherenteffectsofwhicharecrushingofthepillars,cavingoftheroof,andheavingofthebottom."

Indevelopinghisformula,Buntingandhiscollaboratorstestedthestrengthofcoalspecimensinthelaboratoryandconductedback-analysisoffull-scalepillarfailures（“squeezes”）underground.Usingessentiallythesameapproach,anumberofpillardesignformulasweredevelopedduringthenext70yearsaroundtheworld.These“classic”methodsconsistedofthreesteps:

1.Estimatingthepillarloadusingtributaryareatheory;

2.Estimatingthepillarstrengthusingapillarstrengthformula,and;

3.Calculatingthepillar"

safetyfactor"

（SF）.

Step1,estimatingtheload,wasfairlystraightforwardforanindustrythatreliedalmostexclusivelyonroom-and-pillarminingatrelativelyshallowdepth.Thetributaryareaestimatewasconsideredsufficient,thoughitwasrecognizedthatinnarrowpanelsthepillarsneartheedgesmightnotexperiencethefullload.

Morecomplexweretheissuesassociatedwithpillarstrength.Thetwobigissueswerethe“sizeeffect”andthe“shapeeffect.”Thesizeeffectwasmostprominentinthelaboratory,wherecoalstrengthtestingshowedthatlargerspecimensweremuchweaker

thansmallones.Theshapeeffectreferredtotheobservationthatslender（lowwidth-to-heightratio）pillarswereweakerthanonesthatweremoresquat.

Asthenumberofclassicformulasproliferated,sodidthearguments.Shouldtheshapeeffectberepresentedasastraightline,orasanexponentialequation?

Wastheresuchathingasa“critical”specimensize?

Coulda“universal”formulaevenexist,ordideachonehaveitsownplace?

Theseissueswerediscussedatlengthinanumberofsurveypapersthatwereapersistentthemeinthosedays（Babcocketal.,1981;

LogieandMatheson,1983;

Hustrulid,1976）.

Insomerespects,Bieniawskirepresentedtheculminationoftheclassicapproachtopillardesign.InhispaperattheFirstConferenceinMorgantown,Bieniawskiclearlydescribedtheissuesinvolvedinpillardesign,andtheadvantagesandshortcomingsoftheavailablemethods.Hethenoutlinedalogical,step-by-stepapproachtosizingcoalpillars.Indeed,Bieniawski’sworkhasprovidedafirmfoundationuponwhichmanyofthedevelopmentsofthepast25yearshavebeenbuilt.

However,theFirstConferencealsocontainedapaperthatdescribedaradicallynewanddifferentapproachtopillardesign.ArthurWilson（1972,1981）oftheBritishNationalCoalBoardhadfirstproposedhis“hypothesisconcerningpillarstability”in1972,butby1981hehadexpandedandrefineditconsiderably.Hisframeofreferencewasdeeplongwallmining,whereverylargepillarswereroutinelyemployed.Here,thegoalofpillardesignwasnottopreventapillarcollapse,butrathertoensuretheserviceabilityofthegateentries.

Wilson’sfirstproblemwastheneedtogobeyondtributaryareaandconsidertheabutmentloadsbroughtaboutbyfull-extractionmining.Hisconceptofthe“loadbalance,”wherebythereductionofloadinthegobequalstheexcessloadcarriedbythechainpillars,allowedthefirstseriousquantificationofabutmentloads.

MorefundamentalwereWilson’sinnovationsindefiningpillarstrength.Incontrasttotheempiricalformulas,where“strength”wassimplythefailureloaddividedbythepillararea,Wilsontreatedthepillarasacomplexstructure,withnon-uniformstressesthroughout.Hiskeyinsightwasthatthe“shapeeffect”iscausedbythebuild-upofconfiningstresswithinthepillar,whichcreatesahigh-strength“core”inthepillarcenter.WhileWilson’smathematicscontainedsomeseriousflaws（Mark,1987;

Salamon,1992）,hisbasicconceptsareunchallengedtodayandunderlievirtuallyallnumericalmodels（Gale,1996）.

FormanyFirstConferenceparticipants,however,itwasprettydifficulttoseehowBieniawski’sapproachcouldeverbereconciledwithWilson’s.Whiletheybothpurportedtoaddresspillardesign,theinputparameters,mathematicalformulas,and（mostimportantly）thepredictedpillarsizesseemedtoberadicallydifferent.

In1992,thesituationseemed,ifanything,tohavebecomemoreconfused.InthatyeartheU.S.BureauofMinessponsoredthefirstWorkshoponCoalPillarMechanicsandDesign（Iannacchioneetal.,1992）,whichfeatured22differentpapersfromleadingpractitionersfromaroundtheworld.Nearlyeverypaperdescribedadifferentapproach,andthesewereapproximatelyevenlysplitbetweenempirical,analytical,andnumericalmethods.Theirpredictionsforpillarstrengthvariedwidely,however,evenintheirtrend.Somepredictedthatpillarstrengthwouldincreaseexponentiallyasthew/hratioincreased,otherspredicteditwouldtendtowardsamaximumlimitingvalue,andstillotherspredictedanintermediate,linearincrease（figure1）.Stressmeasurementsfrom34coalpillarswerealsoanalyzed,butwerenohelpinnarrowingthefield（MarkandIannacchione,1992）.

Moreover,theWorkshopparticipantscouldnotevenseemtoreachagreementonsomethingasfundamentalaswhatconstitutedpillar"

failure."

Theclassicapproachcontendedthat"

pillarswillfailwhentheappliedloadreachesthecompressivestrengthofthepillars"

andthat"

theload-bearingcapacityofthepillarreducestozerothemomentth