14 summary of mining methods and their selection.docx

14 summary of mining methods and their selection.docx

《14 summary of mining methods and their selection.docx》由会员分享，可在线阅读，更多相关《14 summary of mining methods and their selection.docx（48页珍藏版）》请在冰点文库上搜索。

14summaryofminingmethodsandtheirselection

14

SUMMARYOFMININGMETHODS

ANDTHEIRSELECTION

14.1INTRODUCTION

Inthis,thefinalchapterofthebookitisourobjectivetoofferindepthcomparisonsofthevariousmethodsstudiedandtoprovideanobjectivebasisforchoosingaminingmethod.WefirstsummarizethecharacteristicsoftheminingmethodsthatwillallowustochoosemethodsthatarefeasibleandtoeliminatethosethatarenotsuitedforthesubjectdepositWethendevelopanoutlineofaproceduretochooseasurfaceminingmethodand/oranundergroundmethodfromthecandidatemethodsAtthispointintheselectionprocess,itisimportanttobeawareofthecostsforeachmethodwetiestillconsidering.Accordingly,thenextsectionofthechapterdiscussesminingmethodcosts.Theselectionproceduremaythenrequirethatwechoosebetweenasurfacemethodandanundergroundmethod.Aprocedureforaccomplishingthisisoutlined.Amineinvestmentanalysismethodisalsointroducedtoensuretheeconomicvalueofthedepositandtoselltheprojecttothefinancialinstitutions.Finally,thechapterprovidesasummaryoftheminingmethodselectionprocessandaquicklookatthefutureofminingandminingengineering.

14.2METHODRECAPITULATION

SurfaceminingmethodswerecoveredindetailinChapters6,7,and8,andundergroundmethodsweredescribedinChapters9through12.Inthissectionwereviewtheimportantcharacteristicsofminingmethodstoprovideaprocedurefornarrowingdownthenumberofmethodsthatwillbeconsidered.ButfirstwelookattheproductionstatusofminingmethodsintheUnitedStatestoseehowwellutilizedthevariousmethodsareatthepresenttime.GeneralinformationonproductionisprovidedinTable14.1.Notethattheusageofthemethodsisprovidedingeneraltermsonlybecauseproductionstatisticsonminingmethodsarenolongerreadilyavailableexceptforcoalminingmethods.StudentsmaywishtoconsultthetablesinChapters8and13ofHartman（1987）,whichprovideproductionstatisticsforthemid-1980s.Morerecentstatisticsarenotreadilyavailable.

Inshouldbenotedthatsomeoftheminingmethods（likeleachingandlongwallmining）havebeenincreasinginusagewhileothers（suchasshrinkagestoping,stullstoping,andsquare-setstoping）havebeendecreasing.Table14.1providesvaluableinformation,asthemethodsthatareoftenusedarenormallyassociatedwithsuitabletechnologyandproductioncharacteristicsthatmakethemeconomicformanydepositsintoday'smarketplace.Wenowturntosomeofthepertinentcharacteristicsofminingmethodsthatwillenableustonarrowthelistofpotentialminingmethods.

Toaccomplishtheprocessofreducingthefieldofcandidatemethods,werefertothegeneraldiscussioninSection4.8offactorsthatdeterminetheminingmethodchosenforexploitationofthedeposit.Thesearegroupedinsixcategories:

1.Spatialcharacteristicsofthedeposit

2.Geologicandhydrologicconditions

Table14.1U.S.MineralProductionbyMiningMethod

MethodProduction

OpenPitHigh

QuarryingLow

OpencastminingHigh

AugerminingLow

HydraulickingLow

DredgingLow

BoreholeminingLow

LeachingModerate

Room-and-pillarminingHigh

Stope-and-pillarminingModerate

ShrinkagestopingLow

SublevelstopingLow

Cut-and-fillstopingLow

StullstopingLow

Square-setstopingLow

LongwallminingHigh

SublevelcavingLow

BlockcavingLow

Table14.2ClassificationofOreandRockStrength

Compressive

Strength,

MineralorRockRelativeStrengthlb/in.2（kPa）

Coal,decomposedandbadlyalteredVeryweak<6,000（<40,000）

rock

Friablesandstone,mudstone,weatheredWeak6,000-14,500

rock,softshale（40,000-100,000）

Shale,limestone,sandstone,Moderate14,500-20,000

schistoserock（100,000-140,000）

Mostigneousrock,strongmetamorphicStrong20,000-32,000

rock,hardlimestoneanddolomite（140,000-200,000）

Quartzite,basalt,diabaseVerystrong>32,000

（>220,000）

Source:

ModifiedafterHamrin,19t2BypermissionfromtheSocietyforMining,Metallurgy,andExploration,Inc.,Littleton,CO.

3.Geotechnicalproperties

4.Economicconsiderations

5.Technologicalfactors

6.Environmentalconcerns

Inthissection,weattempttooutlineaprocedurethatwilleliminatemethodsthatarenotsuitableforthedepositathand,usingthesixfactorslisted.Thiswillhelptoreduceouranalysisinthelaterstagesofmethodselection.Itisalsoimportantatthispointtoconsiderwhetherthedepositcanbeminedbysurfacemethods,byundergroundmethods,orbyacombinationofboth.Itmaybepossibletolimitthesearchforaminingmethodtoeithersurfaceorundergroundmethodssimplybyconsideringthedepthofthedeposit.

Althoughtherearemanyfactorsthatcanbeusedintheselectionofaminingmethod,oneofthemostimportantcategoriesisthegeotechnicalpropertiesoftheoreandrock.Thus,thestrengthoftheoredepositandthesurroundingrocksisofprimeimportanceintheselectionoftheminingmethod.Tohelpinthiseffort,weintroduceTable14.2,whichdefinesthecompressivestrengthofrocksforourqualitativestrengthdescriptionsfromveryweaktoverystrong.Thistablewillhelpthestudenttodeterminewhatrockstrengthsareamenableforeachminingmethod.

14.2.1SurfaceMiningMethods

Avarietyoffactorsshouldbeconsideredinreviewingthesurfaceminingmethodsforsuitabilityinexploitingagivenoredeposit.Inadditiontothesixcategoriesoffactorslistedearlier,theselectioneffortshouldconsiderthesequenceofdevelopment,theunitoperationstobeemployed,thehealthandsafetyaspectsofthemethods,andtheauxiliaryoperationsthatmustbeutilizedintheminingoperation.

Inchoosingorrejectingagivenminingmethod,thefirstsetoffactorstobeconsideredarethedepositconditionsandhowtheyrelatetothevariousminingmethods.Toaidinthisendeavor,informationonmanyofthephysicalcharacteristicsoftheeightsurfaceminingmethodsislistedinTable4.3.Thedepositcharacteristicscanbecomparedwiththeentriesinthistabletochooseminingmethodsthatarecompatible.NotethattheinitialmethodssingledoutusingTable14.3canbefurtherreducedinnumberbyreferraltoTable14.4wheretheadvantagesanddisadvantagesofthesurfacemethodsareoutlined.Adetailedstudyofthistablemayrevealadditionalmethodsthatcanbeeliminatedfromthelistofcandidatesbecausetheyhaveaparticularlyadversesetofdisadvantagesoralackofadvantages,ascomparedwithothermethods.Itmaybeadvisableatthispointtolimitthemethodstothetwomostlogicalsurfacemethods.Theselectionofsuitablesurfaceminingmethodsmaybeeasierthanchoosingsuitableundergroundmethods,becausethesurfaceminingproceduresaremorehighlydependentonwhatformsofgeologicdepositstheywilleconomicallyextract.

14.2.2UndergroundMiningMethods

Considerationofundergroundminingmethodsproceedsinamannersimilartothatforsurfacemethods.ThefirststepistocomparethedepositconditionswiththemethodcharacteristicsinTable14.5.Theobjectiveofthiscomparisonistoeliminatethosemethodsthatarenotsuitabletothedepositconditions.Theadvantagesanddisadvantagesoftheundergroundminingmethods,showninTable14.6,mayalsobeusedtoeliminatemethodsthatarenotsuitedtothemineraldeposit.

Notethattheundergroundmethodsusedforcoalarerelativelysmallinnumber,consistingofroom-and-pillarmining,longwallmining,andoccasionallyshortwallmining（asubcategoryoflongwallmining）.Ontheotherhand,thesethreemethodscanoftenbeusedinnonmetalandmetalminingalongwithalltheotherundergroundmethods.

Thechoiceofanundergroundminingmethodisoftenmoredifficultthanthatforsurfacemining,andminingengineershavefrequentlysoughtlogicaldecisionprocedurestohelpintheselection.OneoftheseselectionproceduresisoutlinedinTable14.7.TheoriginalversionofthistablewasproducedbyPeele（1941）.ThetablewasthenmodifiedbyLucasandHaycocks（1973）andbyThomas（1973）.Notethatthetablecanbeusedtoselectacoupleofminingmethodsthatmaybeappliedtoanygivendeposit.However,itdoesnotalwaysnarrowthechoicetoasinglemethod.Thus,theselectionproceduremaybecontinuedwiththeideaoffurthernarrowingthefield.ThiswillbeattemptedinSection14.3.

Table14.3ComparisonofDepositConditionsFavorabletoSurfaceMethods

MechanicalExtractionAqueousExtraction

FactorOpenpitQuarryingOpenCastAngeringHydraulickingDredgingBoreholeLeaching

1.OrestrengthAnyAny（soundAnyAnyUnconsol-Unconsoli-ConsolidatedRubblizedor

structure）idated,fewdated,somecavable.

bouldersboulderspermeable

2.RockAnyAnyAnyAnyUnconsoli-Unconsoli-CompetentCompetent,

strengthdateddatedimperviousimpervious

3.DepositAnyThick-bed-Tabular.Tabular,TabularTabularAnyMassiveorthick

shape（preferably）dedorbeddedbeddedtabular

tabular）massive

4.DepositdipAny（preferablyAny,ifthickAny（preferablyLowdipLowdipLowdipAny（preferablySteep

lowdip）lowdiplowdip）

5.DepositsizeLarge,thickLarge,thickLarge.LimitedLimitedModerateModeratetoAny（preferably

moderateextent,thinextent,thinextent,largelarge）

thicknessthickness

6.OregradeLowHigh（assayLowLowVerylowVerylowIntermediateVerylow

notcritical）

7.OreUniform（orUniformFairlyuniformUniformFairlyuniformFairlyuniformVariableVariable

uniformitysortorblend）

5DepthShallowtoShallowtoShallowShallowVeryshallowVeryshallowModeratetoShallowto

moderatemod