6 surface mine developmentWord文档格式.docx
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6 surface mine developmentWord文档格式.docx
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TheproportionsoforeandtotalmaterialtonnageproducedinsurfaceandundergroundminesareprovidedinTable6.2.Thetonnageoforeandcoalbeingminedonthesurfacekeepsincreasing.Whenthefirsteditionofthisbookappearedin1987,theproportionoforeandcoalminedinsurfaceminesintheUnitedStateswas85%,itisnowmorethan88%).Notealsothatthepercentageofallmaterialminedinsurfaceminesisgreaterthan960/oonatonnagebasis.Thi5heavyemphasisonsurfaceminingisduetotwofactors:
theincreasingdifficultyoffindingdepositsthatcanbeeconomicallyminedundergroundandtheever-increasingefficiencyofmininginsurfacemines.Thisistrueeventhoughthecostofreclamationforasurfacemineisincreasingsteadily.Thesuccessofsurfaceminingoperationsisthushighlydependentonefficientdrilling,blasting,loading,andhaulage.
Table6.1EstimatesofOreandWasteProductionforDifferentMineral-CommodityClassesinSurfaceandUndergroundMiningintheUnitedStates,1997
SurfaceUndergroundAllMining
CommodityOreWasteTotalOreWasteTotalOreWasteTotal
(milliontons)
Metals12901.8633.153643671,3541.8663,220
Nonmetals27784493.22712301232,9014493,350
Coal66910,303*10.97242145*4661,09010.34811,438
Total473712,61517,352608486565,34512.66318,008
Source:
Moore((997)andEnergyInformationAdministration(2000).
ThesevaluesbasedonorewasteratiosreportedbyEnergyInformationAdministration(1983).
Table6.2ProportionsofOreandCoalTonnageandTotalTonnagefromSurfaceandUndergroundMines
OreTonnageTotalTonnage
SurfaceUndergroundSurfaceUnderground
Metals95.3%4.7%97.9%2.1%
Nonmetals95.8%4.3%96.3%3.7%
Coal61.4%38.6%95.9%4.1%
Total88.6%I1.3%96.4%3.6%
Sources:
EnergyInfurm3ticnAdministration(1983,2000).Moore(1997).
Mineplanninganddevelopmentarecrucialstepsintheoperationofasurfacemine.Certainfactors(seeSection4.2)mayrequirespecialattentioninpreparationforsurfacemining.Ofthelocationfactorsclimateisofmorecriticalconcerninsurfaceoperationsthaninundergroundmines.Today,harshclimatesathighaltitudesorinnorthernlatitudesrarelyprecludesurfacemining,buttheycanbedetrimentaltoefficientandcost-effectiveoperation.Amongthenaturalandgeologicfactors,terrain,depth,spatialcharacteristicsofthedeposit,andpresenceofwaterareveryimportantvariables.Theenvironmentalconcernsandthecostsofovercomingenvironmentalproblemsrankamongthemostimportantconsiderationsintheplanninganddevelopmentofasurfacemine.
ThestepsinthesequenceofminedevelopmentarcenumeratedinSection4.2;
threeoftheseareuniquetosurfacemining:
1.Initiationofalandreclamationplanaspartoftheenvironmentalimpactstatement(EIS)
2.Provisionoftopsoilstockpilesandwastedisposaldumps
3.Performingadvancedstrippingofoverburdentogainaccesstothedeposit
Otherstepsinminedevelopmentmustbecarriedoutaswell,butthesethreestepsrequiresignificantresourceallocationandplanningforasurfacemine.Figure6.1showstheminedevelopmentscheduleforatypicalmine(Petty.1981).Notethattheenvironmentalstudiesandthepermittingprocessareasignificantpartoftheoverallminedevelopment,andthatenvironmentalconcernsarecontinuousthroughoutthedevelopmentprocess.Thus,thefirstoftheaforementionedthreestepsindevelopmentwillnormallybeamajorConsiderationinthedevelopmentofthemine.Landreclamation,wastedisposal,andadvancedstrippingarescheduledduringStage3ofFigure6.1.(Noticethatitiscustomaryterminologytosaywe'
tuneore,stone,orrockbut
FIGURE61.Schedulingdiagramforsurfacemetalmine.(AfterPetty,1981.BypermissionfromAmericanInstituteofProfessionalGeologists,ColoradoSection,Golden,Co.)
thatwestripoverburdenorwaste.)Wewillconsiderthethreetasks,aswellasplantlayout,inmoredetailinthesectionsthatfollow.
6.1.1LandReclamation
ThefederalSurfaceMiningControlandReclamationActof1977requiresthatlanddisturbedbyminingbereclaimedandrestoredtoitspreminingconditionorbetter.SomeofthemanyrequirementsaresummarizedinSection2.2.5.Duringdevelopment,thefirststepsaretakentoensurethattheFISfiledbythecompanyisfullyimplemented.Thecompanymustpostasizablebondtocovertheexpectedcostofreclaimingtheland.Thebondoneachsectionoflandisreleasedonlyafterthelandhasbeenreclaimedandsuitablevegetationhasbeenestablished.Provisionsofthelaw,whichareprimarilyapplicabletosurfacecoalmines,arequitestringentandcostly.Restorationoflandto“approximateoriginalcontour"
followingminingisarequirementthatncccs51-tatescarefulplanning,surveying,andmapping.Preservingsurfacedrainagemayrequirestreamrelocationordiversion.Carefulcontroloftherunofffromthemineisalsonecessarytopreventstreamsiltation.Maintainingwildlifeandfisheriesisofspecialconcernonlandstobesurfacemined.Provisionstoprotectfishandgameresourcesandtoprovideacceptablehabitatmustheinitiatedearlyinthedevelopmentprocessandcarefullymaintainedthroughoutthelifeofthemine.Finally,archaeologicalsites,bothknownanduncoveredduringmining,mustbeprotected.Stateorinternationalcodesmayalsoentersignificantlyintotheplanningpicture.Forprovisionsofatypicalstateminingcode,seeAtkinson(1983)andtheIllinoisDepartmentofMinesandMinerals
(1985).
6.1.2TopsoilStockpilesandWasteDisposal
Duringthedevelopmentstageofanysurfacemine.topsoilstockpilesandwastedisposalareasarelocated.Separateareasmayberequiredfortopsoil,subsurfacesoil,rock,low-gradeorleachableore,andtailings.Separatingthesematerialsenhancestheopportunitiestobetterutilizetiematerialsintheextractionofvaluablecomponentsandinthereclamationoftheminedarea.Siteselectionmustensureconvenientdisposalandretrievalbutmustavoidinterferencewithproductionanditsrelatedauxiliaryoperations.Advancedplanningisnecessarytoensurethatthematerialsinstorageneverconflictwithminingactivities.
6.1.3AdvancedStripping
Thegeometryofthemineraldepositandtheoverburdenandtheplannedproductionratedictatetheminimumamountofstrippingthatmustbedonetomaintainthedesiredrateoforeorcoalextraction.Economicconsiderationswouldnormallysuggestthatthestrippingbeperformedonlyasneededbecausetheexpensesassociatedwithstrippingarenotmatchedbyaneconomicreturn(seeSection4.1).However,FourieandDohm(1992)outlinethreegeneralplansforstrippinginasurfaceminetheincreasingstrippingratiomethod,thedecreasingstrippingratiomethodandtheconstantstrippingratiomethod.TheincreasingstrippingratiomethodstrictlyfollowstheruleofstrippingonlyismuchoverburdenasrequiredforproductionthisprocedureisoptimalintermsofthecashflowifothervariablesdonotsignificantlyenterthepictureTheothertwomethodsattempttoleveloutthestrippingrequirementsandspreadthemmoreevenlyovertime.InadepositthatdoesnotoutcropadvancedstrippingisrequiredbeforeoreproductioncmbeginInadditionitisageneralrulethatacertainamountoforeshouldalwaysbeavailableforminingsothatproductionschedulingisnotconstrainedbythelackofavailableoreoretileofthumb,commonintruck-shoveloperationsistomaintainitleasta30daySupplyofbrokenoreavailablefortheloadingequipment
Amajorconsiderationinstrippingdecisionsmaybetheclimate.Severecoldweathermayfavorstrippinginthesummermonthswhenthegroundisthawed,withminingbeingconductedduringthewinter.IntheironrangesoftheLakeSuperiordistrictandinregionsofAlaska,shippingmayberestrictedbyiceformationonthewaterways.Thus,strippingmaybeemphasizedinwinterandminingduringthesummer.
Afinalconsiderationmayhethedecisionastowhetherthestrippingshouldbeperformedin-houseorbyacontractor.Largeminingcompaniesgenerallyprefertodotheirownstripping,butasmallercompanymayfinditexpeditioustocontractitout.Contractstrippingisoftenmoreexpensive,butitmaybequicker.Inaddition,theminingcompanyisrelievedofthecapitalexpenseofpurchasingstrippingequipment.
6.1.4PlantLayout
SomeofthefactorsthatmustbeconsideredinselectingthemineplantsizeandlayoutwereidentifiedinSection4.2.Forasurfacemine,thetaskiscomplicatedbythespecialconsiderationsjustdiscussed:
landreclamation,topsoilstockpilingwastedisposalandoverburdenstripping.Thesemostbecarefullyplannedtominimizethecostofmining.Inadditionthesupportactivitieswillbecomeanimportantadditionalmineplantlayouttask.Theplantlay
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