毕业论文外文翻译-关于二柱掩护式支架与顶板之间相互作用的研究

河北工程大学毕业论文PAGE1ASTUDYOFTHEINTERACTIONBETWEENTHE2-LEGSHIELDSUPPORTANDTHEROOFSTRATAINTRODUCTIONThe2-legshieldpoweredsupportisshowninFig.1.Itisknownthatinordertoassestheadaptabilityofapoweredsupportnormallytherearetwoprinciplestobeconsidered:Fig.12-legshieldsupportEFFECTIVENESSOFROOFCONTROLObviously,shieldsupportismucheasiertopreventthebrokenrocksfromfallingintotheworkingspace,butitismuchhardertopreventthebrokenrocksfromfallingintotheface-to-canopyarea.OnthebasisofthestatisticaldataobtainedfromtheCollieriesYang-QuanandZhai-Li,thedown-timeleadstostopproductionduetofallingroofintheface-to-canopyareaisabout40-60%ofthetotaldown-timeintheworkingface.CollapseofroofstrataalongthefacelineisshowninFig.2.Thatistosay,inafaceinstalledwith2-legshieldpoweredsupportmuchmoreattentionmustbepaidtotheproblemofimmediateroofcontrol,especiallyintheface-to-canopyarea.EFFECTONSUPPORTSTRUCTUREUNDERTHEACTIONOFROOFPRESSURERecentreportsfromsomecollieriesrevealthat2-legshieldsupporthasbeenbrokenundertheactionofroofpressure,especiallyatthejointofthecanopyandthestabilizingcylinderasshowninFig.3.Itisevidentthatthesupportingcapacityofthistypeofsupportcouldnotbeconsideredasadequatetosomesuchkindofroofconditionsandmustbeimproved.Fig.2CollapseofalongwallfaceatthefacelineFig.3DamageatthejointofthestabilizingcylinderandthecanopyANALYSISOFLOADINGCONDITIONOF2-LEGSHIELDSUPPOIRTTheforcesactingonthecanopyof2-legshieldsupportare:theroofpressure,theforcesfromthesupportlegs,ram,hingepinofthecanopyandthecavingshield,thesurfacefrictionbetweenthecanopyandtheroofstrata.Assumingthatthesurfacefrictionandtheforceactingonthecavingshieldarenottakenintoaccount,thefollowingformulacanbeobtained:ThemeaningsofallthesymbolsusedinthisformulaareillustratedinFig.4a.Assumingthatthenwecanobtainthefollowingformula.ItcanbeseenthatWhenPisincreasedtotheyieldloadP+,theforcethusintheramwouldbedistributedasshownincurveZintheFig.4b.Infacttheramhasayieldloadinpushandpull.Forexample,fortheshieldsupportW.S.1.7,theyieldloadinpushisequalto67.7tandinpull62.4t.SothecurveoftheforcefromtheramwouldberedistributedinthefaceascurveZ+,andthecurveofforceforthesupportlegswouldberedistributedascarvePshowninFig.4b.ThenthetotalloadPsforthewholesupportcanbegivenasfollows:,AssumingthatW=0,then:Thus,accordingtothepositionwheretheroofpressureactsonthecanopyandreferthesupportperformancetotheloadoftheramZisequalto+Z,(theyieldloadoftheleg)andⅢ-CDzone,onwhichtheloadoframisequalto–Z(theyieldloadoftheraminpull).Theloadbearingcharacteristicsofthesupportlegsandtheeachzoneofthecanopyareshownasfollows:Fig.4ThreeworkingzonesofsupportcanopyⅠzoneZ=Z+..ⅡzoneP=P+.ⅢzoneZ=-Z-Obviously,theresistancesofⅠzoneandⅢzoneonthecanopyareproducedbytheyieldloadoftheram.Forexample,ifZisequaltozero,theresistanceofthesupportitselfinzonesⅠandⅢwouldlossandtheresistancecanbeproducedonlywhenthereexistssomeadditionalforcesfromthecorrespondingzones.InzoneⅢorⅠ.Thereexistsabalanceforceproducedbytheroofstrata.Iftheyieldloadoftheramisincreased,obviously,theintervaloftheⅡzonewouldbecomemuchwider,andtheresistanceonthezonesⅠandⅢwillbeincreasedaccordingly.ThereareshowninFig.5.Fig.5ResistanceCurveofdifferentyieldloadoframINTERACTIONBETWEENROOFPRESSUREANDSUPPORTRESISTANCEItiswell-knownthattheroofpressureactingonthecanopyofthesupportcanbedividedintotwocomponents,theyare:Q1producedbytheimmediateroofandQ2bythemainroof,asshowninFig.6.Asageneralrule,theimmediateroofcanbeconsideredasadiscontinuousmedia(likealoosebody)andthereisafreefacealongthecavingline.LoadQ1actssteadilyonthesupports.Loaddistributiononthecanopymaybeconsideredasuniform.LoadQ2fromthemainroofmaybeconsideredasaconcentratedloadwhichactsontheimmediateroofandthenactsonthecanopyofthesupport.Basedonthedisplacementmeasurementofroofstrataithasbeenfoundthatthemainroofoftheoverlyingstratacanbeconsideredasastructureformedbylayersofrockblocksinterlockingwithoneanother,whenthecoalfaceadvances,eachblockbecomestomoveformingaturningblock.ThedisplacementofthemainroofisshowninFig.7.Obviously,theactingpositionoftheloadfromthemainrooffirstlydependsonthestabilityconditionoftheblocksinthemainroof.Q2canacteitherinfrontorintherearofthecanopy.Secondly,itdependsonthepositionwheretheimmediaterooffalls.Ifthefrontsectionoftheimmediateroofisfracturedandfallsintotheworkingspace,thentheforcefromthemainroofwouldactonthecanopy.Iftheconditionisoppositetothis,thentheforcewouldactonthepositioninfrontofthecanopy.Consequently,theroofpressureQactingonthecanopycanthuscanbecombinedfromthoseofQ1andQ2.Fig.6RoofPressureProducedbythemainroofandtheimmediateroofFig.7DisplacementofthemainroofWhenthepressureQactsonzoneⅠandQ>Ps,thereliefvalveoftheramwouldfirstlyopen,thenthefrontpartofthecanopywouldturndownwardsandthebalanceforceQ3wouldbeproducedintherearpartofthecanopymustbekeptintactormustnotcaveequaltotheresistanceforce(Ps)ofthesupport.IntheoppositeconditionthebalanceforceQ3wouldbeproducedinzoneⅠ.FromthiswecanseethattheresistanceofthistypesupportcanthusbeformedintheconditionwhenthebalanceforceQ3occursonthecanopy.Thatistosay,theimmediateroofmustnotcaveatall.Accordingtotheanalysismentionedabove,nowconsiderthatisunderthedifferentconditions:TheroofisunbrokenandtheresistanceofthesupportPsisequaltoP+(theyieldloadofthelegs).Thentheresistanceofthesupportcanbeexpressedasfollows:Q＋Q3＝PsAssumePs＝P+,sothatThentheactingpositionwheretheroofpressureQactswouldbecomex＝P＋（1－A）·z/BAssumethattheactingpositionwheretheroofpressureQactsisatx1,andthebalanceforceQ3isx3(theoriginisinthehingepinpoint),thenthefollowingformulaisobtained:Q·x1＋Q3·x3＝（Q＋Q3）·（p＋（1－A）·z/B）TheroofpressureQwhichthesupportcanresistisequalto:TheroofpressureQwhichthesupportcanresistisequalto:Taketostandfortheefficiencyofthesupport,obviously,thishasrelationwiththefollowingfactors:thegeometricalparametersofthesupport,i.e.parametersofthebalanceforce(reaction)oftheimmediateroofx3.Itisobviousthatthenearerthevaluex1approachestozoneⅡ,thehighertheefficiencyofthesupportwouldbe.Somethingthevaluex3canberepresentedasanindextostandfortheinteractiverelationbetweenthecanopyandtheimmediateroof.WhenQactsintheposition,thebalanceforceisequaltozero,andtheefficiencyofsupport,isequalto1.Fig.8showsthatwhenavariableroofpressure(Q)actsinthreedifferentpositions(x1)inthezoneⅠofthecanopyandwithdifferentindexx3inzoneⅢ,inordertoresisttheroofpressure(Q),acorrespondingbalancereactionforceQ3withdifferentvaluesmustbegiveninzoneⅢ.Forexample,whentheroofpressureisactingonthetipofthecanopyandisequalto80tifx3>37cm.thentherewouldbenosuchbalanceforceformedintherearpartofthecanopy.Becauserooffalloccursintheface-to-canopyareawheretheroofwouldbecomeirregular,thusthecanopywouldhavethreekindsofoperatingconditionforthecanopytoswing:downwards(<0○)upwards(>10○)andatananglefrom0○to10○.AccordingtostatisticaldatacollectedfromZhai-LiColliery,thepercentageoftheoperatingoftheoperatingconditionsofthecanopyswingingcanopyin<0○accountsfor3.5%andthatofin>15○,for11%.Duetothefactthattheactingpositionoftheroofpressureonthecanopyisdifferent,theanglebetweenthecanopyandthecavingshieldmaybevariable.Table1showsthevariationaccountsfor44.8%,whichmeansthatthecanopyandthecavingshieldmaybevariable.Table1showsthevariationofthisangleineachoperationcycle.FromTable1,wecanseethatthepercentageofpositivevariationaccountsfor44.8%,whichmeansthattheroofpressure(Q)firstlyactsonzoneⅠandthanthebalanceforce(reaction)(Q3)isformedonzoneⅢ;finally,theactingpositionofthecombinedforce(Q+Q3)wouldmovetowardszoneⅡ.InTable1thepercentageofnegativevariationaccountsfor19.4%.SimilarresultshavealsobeenobtainedfromfieldmeasurementsinworkingfaceNo.332ofZhai-LiCollieryasshowninTable2andFig.9.Obviously,whethertheroofpressureactsonzoneⅠorⅢofthecanopy,iftheactingpositionofthecombinedforce(Q+Q3)movestowardszoneⅡ,theoperatingconditionofthesupportwouldbenormal.ButiftheactingpositionofthecombinedforcemovesoverzoneⅡandcontinuouslymovesforwardsorbackwards,thesupportwouldthenworkinabnormalconditions.Fig.8BalanceforceCurvesfordifferentindexX3inzoneⅢ关于二柱掩护式支架与顶板之间相互作用的研究二柱掩护式支架如图1所示。为了评定支架的适应性，通常有两个特性要考虑：顶板控制影响显然，掩护式支架更容易阻止冒落矸石掉在工作面上，但是它更难阻止冒落矸石掉在遮蓬区。根据来自阳泉和翟梨的资料显示,下落时间导致停止生产，归因于下落顶板在遮蓬区大约是40％～60％的下落时间在工作区。顶板沿着朝向倒塌。就是说，在一个装有二柱掩护式支架的面上更多关注的是顶板及时控制问题，特别是面向遮蓬区。在顶板压力作用下对支护结构的作用近期来自煤矿的报道证明，二柱掩护式支架已经在顶板压力作用下破坏，特别是遮蓬和稳定柱面连接处。明显的是这种支架的支护空间被认为对一些顶板条件不够，并且必须改进。二柱掩护式支架加载条件分析作用在二柱掩护式遮蓬上的压力：顶板压力，来自立柱的力，撞击，遮蓬和洞穴保护的销轴，顶梁和顶板的破碎表面。假设表面破碎和作用在掩护梁上的力不考虑，可以得到下面的公式： 上式中符号的意思表达在图4a中。假设然后我们可以得到下面的公式。可以看出，当P增大到屈服载荷P+，力因此在撞击中形成象在图4b中曲线Z所描述的。事实上撞击的推拉力有一个屈服载荷。例如，对于掩护式支架W.S.1.7，屈服力是推力67.7t和拉力62.4t。因此，撞击力的曲线如图4b所示。那么总的载荷Ps整个的支架给出如下：假设W=0,那么因此，根据顶板作用在顶梁上的压力的位置和支架支护的表现，我们可以遮蓬划分为3个工作区，即，II－BC区，立柱的载荷P等于P+，Ⅱ－BC区，立柱载荷P等于P+和Ⅲ-CD区，和撞击的载荷力等于－Z（撞击的屈服力是拉力）。支撑立柱承受力的特性和每个遮蓬区上的冲击显示如下：Ⅰ区Z＝＋Z；Ⅱ区P＝P+Ⅲ区Z＝－Z-显然，作用在Ⅰ和Ⅲ区遮蓬上的反作用力是由冲击的屈服载荷产生的。例如，如果Z等于0，在Ⅰ和Ⅲ区支护本身的反作用力将失去和反作用力丢失和只有当来自相应区域的一些附加力存在时反作用力将产生。在Ⅰ或Ⅲ区，存在由顶板产生的平衡力。如果冲击的屈服载荷产生了，显然，Ⅱ区的距离将变的更宽，并且Ⅰ或Ⅲ区上的反作用力将由此增加。这些如图5所示。顶板压力和支护反作用力的相互作用众所周知，作用在支护顶梁上的顶板压力可以分成两个部分，它们是：由及时顶梁产生的Q1，由主顶梁产生的Q2，显示在图6中。作为通用法则，作为一个不连续的媒体被考虑和存在一个沿着洞穴的自由面。载荷Q1固定作用在支护上，载荷分布在遮蓬区可以认为是均布的。来自主顶梁的载荷Q2被作为一个集中载荷考虑，作用在及时顶梁和支护保护。基于顶板测量显示，发现主顶梁过度层可以作为由大量的岩石连续互锁形成的一