毕业设计英文翻译爆破在岩巷掘进中的应用及井巷支护Word文件下载.doc
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1.1FRAGMENTATION
Fragmentationisthebreakingofcoal,ore,orrockbyblastingsothatthebulkofthematerialissmallenoughtoload,handleandtransport.Fragmentationwouldbeatitsbestwhenthedebrisisnotsmallerthannecessaryforhandlingandnotsolargeastorequirehandbreakingorsecondaryblasting.
Energymustbesuppliedtorockbydirectorindirectmeanstofragmentthatrockandthetypeofloadingsystem.Fragmentationenergyisconsumedbythemainmechanisms:
(1)creationofnewsurfacearea(fractureenergy),
(2)friction(plasticity)and(3)elasticwaveenegydispersion.
Theloadingmethoddeterminestherelativeproportionsandtheamountofenergyconsumedinfragmentingagivenrocktype.Unonfinedtensilefailureconsumestheleastenergywithanincreasinga,mountofenergyrequiredastherockismorehighlyconfinedwithinacompressivestressfieldduringfragmentationThewayenergyisappliedbytoolstocauserockormineralfragmentationisimportantindeterminingfragmentationefficiency.Tobestdesignfragmentationtoolsandoptimizefragmentationsystemsitwouldbedesirabletoknowhowrockpropertiesinfluencebreakage.
Thestrengthofrockisinfluencedbytheenvironmentalconditionsimposedontherock.Thoseofmostimportanceinrockare
(1)confiningpressure,
(2)porefluidpressure,(3)temperatureand(4)rateofloadapplication.Increaseinconfiningpressure,aswithincreasingdepthbeneaththearth'
ssurfaceorundertheactionofafragmentationtool,causesanincreaseinrockstrength.Apparentrockstrengthdecreasesasporcfluidpressureincreases,sinceitdecreasestheeffectofconfiningpressure.Althoughchemicaleffectsofporefluidsinfluencerockstrength,theygenerallyaresmallcomparedtotheconfiningpressureeffect,exceptforasmallminorityofrocktypes.Increaseinrocktemperaturecausesadecreaseinrockstrength.Thiseffectisverysmallbecauseofthesmallambienttemperaturechangesfoundduringmining.Anincreaseinrateofloadapplicationcausesanapparentincreaseinrockstrength.
Rockexhibitsdirectionalpropertiesthatinfluencethewayitbreaks.Theseareembodiedintheconceptofrockfabric,whichconnotesthestructureorconfigurationoftheaggregatecomponentsaswellasthephysicalormechanicalpropertymanifestations.Rockfabricontonlyrelatestothepreferredorientationofmineralconstituentsandtheirplanesofweakness,butalsototheconfigurationofdiscontinuities,microcracksandpores.Jointsandbeddingplaneshavegreatinfluenceonfragmentationatfieldscale.
Physicalpropertiesofrock(density,indentation,hardness,abrasivehardnessandporosity,)arefrequentlyusedinconjunctionwithmechanicalpropertiestodevelopbetterempiricalestimationsofrockfragmentation.
1.2BLASTHOLECHARGINGMETHODS
Drillholechargingcanbecarriedoutindifferentwaysdependingonwhethertheexplosiveusedisincartridgesorintheformofloosematerial.Theoldestchargingmethodimpliestheuseofatampingrodandthissystemisstillusedtoaverygreatextent.Duringthelast20years,compressedairchargershavebeenusedandthesemachinesprovidebothgoodcapacityandalsoanimprovedlevelofchargeconcentrationsothatthedrillholesareutilizedtoahigherdegree.Duringthelastfewyearssemi-automaticchargershavebeentakenintouse,primarilyinundergroundwork.Compressedairchargersforblastingpowderintheformofloosematerialhavealsocomeintouseonalargescale.Asfarasslurryblastingisconcerned,specialpumpingmethodshavebeendevelopedthroughwhichchargingcapacityinthecaseoflargediameterdrillholesispracticallygood.
Atampingrodmustbemadeofwoodorplastic.Itmustnotbetoothickinrelationtothedrillholediametersincethiscancrushanddamagefuseorelectricdetonatorcablesduringchargingwork.Ifagooddegreeofpackingistobeobtainedduringchargingwithatampingrodthenonlyonecartridgeatatimeshouldbechargedandtamped.Thedetonatormustbecorrectlyfedintothedrillholeduringchargingwork.
CompressedairchargershavebeeninuseisSwedenforabout20years.Thefirsttypeconsistedofaluminumpipesconnectedtogetherandthecartridgeswereblownintotheholewithanairpressureof42poundspersquareinch.sincethattimethechargingtubehasbeenreplacedbyanti-statictreatedplastichoseofaspecialdesign.Achargerincludesafoot-operatedvalve,reductionvavlewithairhose,breech,connectingtubeandcharginghose.
Thesemi-automaticchargerpermitsthecontinuousinsertionofexplosivecartridgeatthesamerateastheyarechargedintheholebythehose.Insteadofavalvebeingused,thecartridgespassthroughanairlockbetweentwoflaps.Theairpressureinthecharginghoseisretainedwhilecartridgesarepressureinthecharginghoseisretainedwhilecartridgesarebeinsinserted.Thesemi-automaticchargerpermitsconsiderablyhigherchargingcapacitythanthenormaltypeofcharger.
Explosivesintheformoftheformofloosematerial,usuallyammoniumnitrateexplosives(ANFO),requirespecialchargers.Twotypescanbedifferentiated:
pressrurevesselmachinesandejectorunits.PressurevesselmachinesareparticularlysuitableforcrystallineAnexplosiveswithgoodchargingcapacity.Ejectorunitsareoperatebyanejectorsuckingupexplosivefromacontainerthroughacharginghose.Theexplosiveisthenblownthroughthecharginghoseintothedrillhole.Thereare,alsocombinedpressureejectormachines.ThecharginghoseusedforANFOchargingoperationsmustconductelectricityandhavearesistanceofatleast1KΏ/mandmax.30KΏ/M.
NitroNobelhasdevelopedaspecialpumpingprocedurewhichconsistsofatankervehiclewhichisusedtopumpexplosivedirectlythedrillholes.Thechargingcapacityisveryhighinthecaseoflargediameterdrillholes.
1.3CONTROLLEDBLASTINGTECHNIQUTES
Controlledblastingisusedtoreduceoverbreakandminimizefracturingoftherockattheboundaryofanexcavation.Thefourbasiccontrolledblastingtechniquesare:
linedrilling,presplitting,cushionblastingandsmoothblasting.
Linedrilling,theearliestcontrolledblastingtechnique,involvesdrillingarowofcloselyspacedholesalongthefinalexcavationline,providingaplaneofweaknesstowhichtobreak.Linedrillholes,2or4diametersapartandcontainnoexplosive.Theblastholesadjacenttothelinedrillholesnormallyareloadedlighterandareoncloserspacingthantheotherblastholes.Themaximumdepthforlinedrillingisabout30ft.Linedrillinginvolvesnoblastinginthefinalrowofholes,andthusminimizesdamagetothefinalwall.
Presplitting,sometimescalledpreshearing,involvesasinglerowofboreholes,usually2to4in.indiameter,drilledalongthefinalexcavationataspacingof6to12boreholediameters.Dynamitecartridges1to1.5in.insizeon1to2ft.centersusuallyarestring-loaddeondetonatingcord,althoughspecialsmall-diametercartridgeswithspecialcouplersareavailablefortotalcolumnloading.Inunconsolidatedformations,closerspacingswithlighterpowderloadsarerequired.Thebottom2to3ft.ofboreholeusuallyisloadedsomewhatheavierthantheremainder.Stemmingbetweenandaroundtheindividualchargesisoptional.Thetop2to3ft.ofboreholeisnotloaded,butisstemmed.Thedepththatcanbupresplitislimitedbyholealignment,with50ft.beingaboutmaximum.Thepresplitholesarefiredbeforebeforetheadjacentprimaryholestoprovideafractureplanetowhichtheprimaryblastcanbreak.Inpresplittingitisdifficulttodeterminetheresultsuntiltheadjacentprimaryblastisshot.Forthisreason,presplittingtoofarinadvanceisnotrecommended.Presplittingseldomisdoneunderground.
Cushionblastinginvolvesdrillingarowof2–to6-in.diameterboreholesalongthefinalexcavationline,loadingwithalightwell-distributedcharge,completelystemmedandfiringafterthemainexcavationisremovedratherthanbefore,asinpresplitting.Theburdenontheholesisslightlylargerthanthespacing.Wedgesmaybeusedtoabutthechargestotheexcavationsideoftheboreholeandminimizedamagetothefinalwall.Eeplosiveloadingissimilartothatinpresplitting.Cushionblastinghasbeendonetodepthsnear100ft.inasingleliftwiththelarger-diameterboreholesbecausealignmentismoreeasilyretained.Cushionblastingseldomisdoneunderground.
Smoothblastingistheundergroundcounterpartofcushionblasting.Attheperimeterofthetunnelordrift,closelyspacedholeswithaburden-to-spacingrationear1.5:
1areloadedwithlightwell-distributedcharges.Smoothblastingdiffersfromcushionblastinginthat
(1)exceptatthecollar,thechargesarenotstemmedand
(2)theperimeterholesarefiredonthelastdelayinthesameroundastheprimaryblast.Totalcolumnloadingismostcommon,althoughspacersmaybeused.Theholesarestemmedtopreventthechargesfrombeingpulledoutbythedetonationofthepreviousdelayedholes.Smoothblastingreducesoverbreakinadriftandalsoprovidesamorecompetentbackrequiringlesssupport.Itinvolvesmoreperimeterholesthandoesnormalblasting.
Combinationsofcontrolledblastingtechniquesareused.Inunconsolidatedrock,linedrillingsometimesisdesirablebetweenpresplitorcushionboreholes.Cornerssometimesarepresplitwhencushionblastingisused.
1.4TUNNELBLASTING
Themostcommonmethedofdrivingaminingtunnelisacyclicoperationinthreesequences:
(1)Drillingshotholes;
chargingthemwithexplosivesandblast