英文文献翻译.docx

英文文献翻译.docx

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英文文献翻译

Experimentalresultsofalow-powerroadheaderdrivingagallerywithdifferenttypesofrock

attheface

Abstract

Inthispaper,theexperimentalresultsofa45-kWand15-troadheaderexcavatingagallerywithtwodifferenttypesofrockatthefaceusingtwodifferentcuttingheadsareshown.Itisprovedthattheroadheaderworksproperlywithbothcuttingheads.Incomparisonwithotherresultsintheliterature,theprincipalparameters,i.e.specificenergy,cuttingrateandtoolwear,areatalevelthatcanbeconsideredsatisfactorytakingintoaccountthelowpoweroftheroadheader.Ontheotherhand,theinfluenceofthenumberofpicks,whichisthemaindifferencebetweenthetwocuttingheads,ontheoperationalparametersisshown.

Keywords:

Roadheaders;Cuttingheaddesign;Specificcuttingenergy;Cuttingrate;Toolwear

1.Testdescription

1.1.Testobjectives

Theaimwastodeterminethepossibilityofdrivingthesegalleriesbymeansofa45-kWroadheader,comparingtwodifferentcuttingheadsexcavatingthesametypeofrockinsimilaroperatingcycles.Themaindifferencebetweenthetwocuttingheadswasthenumberofpicks:

thefirstcuttingheadhad36picks,whilethenewonehadonly24（Fig.5）.Becauseofthelowernumberofcuttingtoolsincontactwiththerock,thetorquetransmittedbythemotorwastransformedtoalargertangentialforceinthepick,whichallowshigher-strengthrocktobecut.Stressconcentrationisthemajorfactorinrockfragmentation.

Theparameterstomeasure（accordingtoclassicstudiesonthistheme;FowellandMcFeat-Smith,1976;Gehring,1989）arethecuttingrate（volumeofrockexcavatedpertimeunitinm

/s）,specificenergy（energynecessarytoexcavateaunitofvolumeinMJ/m

）andthetoolwearorspecificpickconsumption（picksorpickmasslostexcavatingaunitofvolumeofrockinpicks/m

org/m

）.Allparametersweremeasuredwhentheroadheaderwasexcavatingcoalandrock,aswellaswhenitwasperformingotherpartsofthecycle.

1.2.Descriptionoftheexcavatedface.

Thecoalseamminedbythesublevelcavingmethodwasverticalanditsaveragethicknesswas2.0m.Withtheaimofcarryingoutthetestintheworstconditions,thetestzoneusedwasinanareawithaseamthicknessoflessthan2.0m.Athree-segmentsteelsetsupportwasused,thegallerybeingof2.50minwidthatthelowpartand3.0mhigh.InFig.6sketchesoftheexcavatedfaceswiththe36-pick（7.74m）and24-pickcuttingheads（7.97m）areshown.Thecoalseamwas1.70and1.90mthick,respectively.Itwasformedbytwoveins:

ontherightthecoalwassoft（

5MPa）,whileontheleftthecoalwasstrong（

10–15MPa）withoutrockbetweenthem.Theleftwallwasofsiltstone（sometimessandstone）withacompressivestrengthof

60MPa,fracturespacingofS

10–15cmandanRMR（RockMassRatio,Bieniawski,1976）valueofapproximately35–40.TheSiO

contentintherockwas18%andthemeangrainsize18

.TheSchimazekindexwasatanaveragevalueofF=0.194N/mm.Therightwallwasalsosandysiltstone,butmorefracturedanditbrokebecauseofthediscontinuitiesratherthanthepickaction.Fig.7showstheroadheaderandthegallery.

1.3.Testandmeasurements

Thetestforeachofthetwocuttingheadsconsistedofadvancing1.35m（equaltothedistancebetweensteelsets）inthreepassesof0.45meach,sincethiswasthedimensionofthecuttinghead.Whiletheroad-headerwasexcavating,theinstantaneouspowerandotherelectricalparameterswererecordedbymeansofadatalogger.Ineachcase,thecross-sectionwasmeasuredandtheexcavatedvolumewascalculatedinordertodeterminetheenergyconsumptionandtoolwear.Allthepickswerechangedfornewonesineachtestandwereweighedbeforeandafterthetrialinordertodeterminethetoolconsumptionduringexcavation.Thepickmasslostineachtestismorerealisticthanthenumberofpickschangedforalongerperiod,becausemanypickscanbelostduetoothercauses.Theoperatingmethodwasasfollows:

inthefirstpass（cuttingthefirst0.45m）thedifferenttypesofrockwerecutseparately;afterthis,thenexttwopasseswerecarriedoutasinatypicalcycleinthemine.Thus,theresultsforthetwocuttingheadscouldbecomparedintheidealcase,inwhichrockwascutseparately,orintheothercaseofamorerealisticexcavation.Informationaboutthecuttingoftwocoalveinsandtheleftrockwallcanbeobtainedfromthefirstpass.Theresults

forcuttingoftherightrockwallwerelessinterestingbecauseofitstendencytofalldownduetodiscontinuities,whichmadeits

excavationeasier.

1.4.Tesewith36-pickcuttinghead

Therecordoftheinstantaneouspowerconsumptionduringthecompletetrialwiththe36-pickcuttingheadisshowninFig.9.

Thetotal-intervalaveragepowerisapproximately35kW（lessthanthenominalpowerofthemotor）,althoughthereareperiodsof2-3sduringwhichvaluesof60kW,representinganoverloadofmorethan30%,arereached.Moreover,peaksof100kWarealsoobserved.However,thesepeaks,producedwhenapickhitsonahardrockzone,are

instantaneousandarenotsignificant.Thecyclestartedwithcuttingofthesoftcoalvein,workingfromtoptobottom.Thisiscommon,becausethefirstcutisthemostdifficultoneduetotherockbeingmoreconfined,andthusthesoftrockisselectedforstartingtheoperation.

Thisfirstcutthenallowseasierexcavationoftheotherpartsoftheface,startingwiththerightrockwall,followedbythehardcoalveinandfinishingwiththeleftrockwall.

Whenthecuttingheadisworking,twodifferentpartscanbeobservedintherecording.One,forwhichhighpowerisrequired,correspondstothetypicalcuttingoperation（theheadisagainsttheface,cuttingasignificantvolumeofrock）,theresultsofwhichareeasytocompareindifferenttests.Theotherpartcorrespondstoperiodsduringwhichtheheadiscarryingoutotheroperationsthatrequirelowerpower.Inthiscase,theresultsarenoteasilycomparablebecausethepowerisonlyslightlyhigherthanthepowerrequiredforheadrotation.Theseoperationsinvolve,forexample,movingwastetohelptheconveyorwork,attackinglocalpointswithoutexcavatingasignificantvolumeofrockinordertogivethefinalgalleryprofile,ormovingthemachinearmwithoutcontactingtheface（inthiscase,headrotationistheonlymovement）.

Theseoperationsaredevelopedaccordingtotheconditionsandcanbecarriedoutduringexcavationofpartoftheface,orafterexcavatingthecompletesection.Inthisstudy,thepowerconsumptionincuttingandotheroperationshasbeenevaluatedseparately.

Thenew36picksplacedonthecuttingheadweighed30017gbeforethetrialand30001gafterwards,i.e.theoverallmasslosswas16g.

1.5.Testwithnew24-pickcuttinghead.

Thecompletepowerrecordofthe24-pickheadtestisshowninFig.10.

Theaveragepowerforthecompleteperiodissimilartotheothercase,35kW,butthetimespentatworkisless（30vs.35min,withoutcomputingstopperiods）.Itcanalsobeobservedthattheoverloadsendureforalongertime.

Inthiscase,theexcavationcyclewasslightlydifferent,havingworkedtherightrockwallintwophases:

thefirstafterexcavatingthesoftcoalveinandthesecondattheendofthecycle,whenthefinalgalleryprofilewascut.The24newpicksweighed19985gbeforethetrialand19961afterwards,i.e.masslosswas24g.

2.Results

2.1Toolwear（pickconumption）

Inthistrialitwasnotpossibletodeterminedirectlythepickconsumption,becausenopickwastotallywornwhencuttingthissmallvolumeofrock.Nevertheless,themasslossduringthetestallowsustoestimatetherateatwhichoneheadwouldwearoutalargernumberofpicksthantheother.TheresultsareshowninTable5.

FromTable5itisinferredthatthetoolconsumptionwouldbeapproximately45%greaterusingthe24-pickheadcomparedtothe36-pickhead.

Takingintoaccountthepickweight（approx.833g）andassumingthatitisnotusefulafterlosing5–10%ofitsmass,thenconsumptionof1.53and2.23g/m

isequivalentto0.036–0.018and0.053-0.026picks/m

inaccordancewithotherpublishedresults（whenthespecificenergyrequiredis10–15MJ/m

toolconsumptionof0.040–0.050picks/m

iscommon）.

Theseresultsareinaccordancewiththeday-to-dayworkofthisroadheader:

thenumberoftoolslostisnearly45%greaterwiththe24-pickheadthanwiththe36-pickhead,asshowninTable6.

Thislevelofpickwearishighcomparedtosoftmineralexcavation（miningpotash,Ortega,1996,orminingcoal,Bermudez,1995）.Nevertheless,itisnotexcessiveinthecaseofexcavatingrock（Anon.,2000）,whichdemonstratesagain

thatitispossibletousethiskindofroaheaderinadvancingthistypeofgallery.

3.Conclusions

Fromthetestscarriedoutandfromexperiencesinthemine,thefollowingconclusionscanbeinferred:

–Analysingonlytheexcavationofrock（themostcriticalmaterial）,thecuttingrateusingthe24-pickheadisapproximately10–20%greaterthanforthe36-pickheadandthespecificenergyisclearlylower.

–Analysinganormalworkingcycle,inwhichthecompletefaceisexcavated,thecuttingratereachedwiththe24-pickheadis20%greater,withlessspecificenergyneeded.

–Onedisadvantageisthatcuttingtoolconsumptionis40–50%greaterwiththe24-pickhead.

–Anotherdisadvantageobserved,forwhichtheeffects

werenotquantified,isthegreaterlevelofvibrationsintheroadheader.

Ingeneral,theuseofaheadwithalowernumberofpickswouldinvolveabalancebetweengreateradvancementintherockandgreaterpickconsumption.Inthecas