喷射混凝土巷道应力测量仪的性能外文文献翻译中英文翻译.docx
- 文档编号:10925019
- 上传时间:2023-02-23
- 格式:DOCX
- 页数:20
- 大小:762.25KB
喷射混凝土巷道应力测量仪的性能外文文献翻译中英文翻译.docx
《喷射混凝土巷道应力测量仪的性能外文文献翻译中英文翻译.docx》由会员分享,可在线阅读,更多相关《喷射混凝土巷道应力测量仪的性能外文文献翻译中英文翻译.docx(20页珍藏版)》请在冰豆网上搜索。
喷射混凝土巷道应力测量仪的性能外文文献翻译中英文翻译
英文原文
Theperformanceofpressurecellsforsprayedconcretetunnellinings
C.R.I.CLAYTON,J.P.VANDERBERG,G.HEYMANN,A.V.D.BICAandV.S.HOPE
Abstract:
Thepaperexaminesthefactorsthataffecttheperformanceoftangentialcellsembeddedinshotcretetunnellinings.Newdata,derivedfromfieldmonitoring,numericalmodelling,andcalibrationtestscarriedouttosimulatetheembedmentandcrimpingprocesses,arepresented.Thesesuggestthatalthoughwell-designedembeddedtotalpressurecellswillhavecellactionfactorsclosetounity,theycannotbeassumedtoprovidereasonableestimatesofthestresseswithinsprayedconcretelinings,unlesstheinfluencesofinstallationeffects,temperaturechanges,shrinkageandsubsequentcrimpingcanbetakenintoaccount.
Keywords:
fieldinstrumentation;tunnels.
Introduction
Thepressurecellsusedformeasuringthecompressivestressesinshotcretetunnelliningsgenerallyconsistoftwostainlesssteelplateswithathinfluid-filledcavitybetweenthem.Thecavityisconnectedeithertoamembrane-typebypassvalveortoavibrating-wirepressuretransducer.Theuseofotherdirect-stressinstrumentshasbeenreportedintheliterature,althoughinfrequently.Pressurecellsaretypicallyinstalledinoneoftwoorientations:
radial,torecordthestressbetweenthesprayedconcreteandthegroundsurroundingthetunnel;andtangential,torecordthehoopstresswithinthetunnelliningitself.Thispaperconsidersonlytangentialcells.
Despitetheirwidespreaduseinpractice,therehasbeenverylittleresearchreportedintheliteratureontheuseandbehaviourofshotcretepressurecells.Manypractitionersremaindoubtfuloftheabilityofembeddedpressurecellstomeasuretheactualstressesinconcretetunnellinings.Inapreviouspaperreviewinginstrumentationforsprayedconcretelinedtunnelsthepresentauthorsnotedsomeofthepotentialdifficulties,statingthatitwas`extremelyunlikelythatembeddedcellsbeusedformonitoringtheactualstressinatunnellining'.Yet,potentially,pressurecellsareavaluablesourceofinformationthatmightbeusedtoassesswhethertunneldesignassumptionsarejustified,andthispaperthereforereportsthefindingsofourfurtherresearchintothisimportanttopic.
Factorsaffectingthepressuresrecordedbytangentialpressurecellsintunnellinings
Directstressmeasurementwithinanymediumismadedifficultbythemanyfactorsthatcanaffecttheresults.Inthecaseoftangentialpressurecellsembeddedinshotcreteourrecentexperiencesduringtunnelmonitoringsuggestthattheseareasfollows.
Cellproperties
Thecellshouldbeconstructedsothatthestressesintheshotcretearenotsignificantlymodifiedbyitspresence.Sincethecompressibilityofthefluidinthecellislessthanthesurroundingmaterialsitwillunder-read,butthiscanlargelybecompensatedforbymakingthecellwideandthin.Theuseofcellfluidssuchasmercuryoroilwillaffectnotonlythecompressibilityofcellsbutalsotheirtemperaturesensitivity.Changesintemperaturewillexpandthefluidagainstthesurrounding,relativelyrigidcellmetalandsurroundingconcrete,andwillproduceachangeinmeasuredstress.
Installationeffects
Theinadvertentformationofcavitiesaroundthecellduringshotcretingwillleadtoasoftmeasurementsystem,whichwillsubsequentlyunder-read.Incorrectpositioningofthecellwithinthelining,rotatingittowardstheradialdirection,canalsocauseittounder-readsomewhat,becauseradialstressesaretypicallylessthan10%oftangential.Indeedtheactualthicknessoftheliningatthepointofinstallationwillalsoaffecttheinterpretationofthestressmeasurements.
Post-installationfactors
Asnotedabove,temperaturechangescanbeexpectedtoleadtochangesinmeasuredstresses.Shrinkageduringtheearlylifeoftheshotcretewillresultinchangesintherecordedstressthatarenotduetoexternalstresschanges.Crimping,whichisoftenundertakentoensurethatpressurecellsareproperlybeddedwithintheshotcrete,canprovideasignificantoffsettothemeasuredpressures.
Numericalandphysicalexperiments,andresultsfrommonitoring
Numericalmodellingandphysicalsimulationhavebeencarriedouttoassesstheactualperformanceofsomestresscellsusedinpractice,andtoplacetheirperformanceinthecontextofothercelldesigns.
Numericalmodellingtoassesstheeffectsofcellfluid
ToexaminetheeffectofcellfluidoncellperformancetwoidealisedcircularcellsembeddedinablockofconcreteweremodelledunderaxisymmetricconditionsusingthefiniteelementpackageLUSAS.ThegeometryofthecellsandthematerialpropertiesmodelledareshowninFig.1.The160mmdiametercellissomewhatlargerthanmanyofthecellscurrentlyinuse,whereasthe80mmcellissmaller,andwasconsideredbytheauthorstobelikelytohaveanexcessiveT/Dratio.Inthefirstnumericalexperimenttheeffectofthebulkmodulusofthecellfluidwasinvestigated,byapplyingaconstantexternalaxialstressandvaryingthecellcavitypressure.Thebulkmodulusequivalenttoeachcellactionfactorwascalculatedbyintegratingthedisplacementsalongthesurfaceofthecellcavity.Fig.2showstheconsiderableinfluenceofbulkmodulusoncellactionfactor,butitalsoshowsthatwhenreasonablecellgeometriesareusedcellactionfactorsremaintolerablyclosetounitywhenoilissubstitutedformercury.
Fig.1.Geometryofcellsandpropertiesofmaterialsusedduringnumericalmodelling:
(a)idealisedpressurecell;(b)geometrymodelled;(c)materialproperties
Fig.2.Effectofbulkmodulusofcellfluidoncellactionfactor
Physicalsimulation
Calibrationtestswereconductedtoevaluatetheperformanceofthevibrating-wiremercury-filledpressurecells,inthreephases:
(a)Duringthefirstphasethemanufacturer'scalibrationofthepressurecellswascheckedbyconductinganairpressurecalibrationonallthecellsused.Thiswasdoneina1mdiameterchamber,inthelaboratory.
(b)Thesecondphaseoftheexperimentalworkwasconductedtoinvestigatewhethertangentialcellsinstalledunderidealandcontrolledconditionscouldproducereliableresults.Thiswasdonebyinstallingtwopressurecellsinaprecastconcreteslab,constructedinthelaboratory.
(c)Thefinalphaseoftheexperimentalworkwasdesignedtoinvestigatetheperformanceofthetangentialcellsunder'workingconditions',aswellastoinvestigatewaysofinstallingthecellstoimprovetheirperformance.Thiswasdonebyinstallingtangentialpressurecellsinshotcreteslabs,formedinatunnelunderworkingconditions.
Thecellsusedfortheexperimentalworkweremercury-filledvibrating-wirecellssuppliedbyGeokon,andwithafull-scalerangeof20MPa(Fig.3).Allthepressuremeasurementswerecalculatedusingthetemperaturecorrectionsuppliedbythemanufacturer.
Fig.3.Vibrating-wiremercury-filledconcretestresscell
Thesecondphaseofthecalibrationtestingwascarriedouttoinvestigatetheperformanceofthetangentialpressurecellsunderidealandcontrolledconditions.Forthisexperimenttwocellswereembeddedina25MPaready-mixconcreteslab,1.0mhigh,1.0mwideand0.3mthick.Thetwocellsweretiedtoacageconstructedfromreinforcingbarmeshes,whichwereidenticaltothoseinuseintheHeathrowTerminal4stationtunnels.Theexperimentalset-upisshowninFig.4,exceptthatinthefirstsetofexperimentstwobarecellswereused.Onebarecellandoneprecastcellwereusedinasubsequentexperiment,describedlaterinthispaper.
Fig.4.Layoutofcellsembeddedinconcretepanel
Duringthecuringperiodtheslabtemperatureincreasedtoabout32°C,andafterwardsdecreasedslowlyoverseveraldays.Monitoringwascarriedoutuntilthecelltemperaturesreachedequilibriumwiththelaboratoryenvironment(Fig.5).
Fig.5.Temperaturesmeasuredaftercastingcellsinready-mixedconcrete
Ateachloadincrementthecellreadingswereobservedtostabiliserapidly:
creepeffectswerenotapparent.Thevalueofcellactionfactorwassubsequentlycalculatedfrompressurecellreadingsandaverageappliedverticalstresses.
Thefinalphaseoftheexperimentalworkconsistedoftheevaluationofthetangentialpressurecellsinstalledunder`workingconditions'.Thiswasdonebyplacingtwopressurecellsineachoftwoslabs,similartotheabovebutconstructedusingshotcreteinatunnelatHeathrowTerminal4.Becausetheresultsoftheexperimentonthecellsinstalledintheconcreteslabshowedthatunderidealconditionsthecellsseemtoperformsatisfactorily,itwasarguedthatfailureunderworkingconditionsmightresultfrominstallationeffects.Amajordifficultywiththeinstallationoftangentialpressurecellsisensuringthatnovoidsareformedin`shadowzones'aroundthecellduringshotcreting.Itwasthereforedecidedtoprecastoneofthecellsineachofthetwoslabsinataperedconcreteblock,designedtopreventtheformationofshadowzones(Fig.6).
Fig.6.Detailofcellcastinprecastconcrete
Discussion
Theoreticalconsiderationssuggestthatawell-designedembeddedcell,withhighstiffnessandalowaspectratio(T/D),shouldhaveacellactionfactorclosetounity.Ourexperimentsoncommerciallyavailablecellssupportthisview.Theabilityofacelltomeasuretheappliedpressurecorrectlyisdependentuponadditionalfactors,however.Offsetsduetotemperature,crimpingandshrinkagemustbeproperlytakenintoaccount.Thequalityofcellinstallationmustbeassessed.
Althoughmanufacturersroutinelysupplytemperaturecorrecti
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 喷射 混凝土 巷道 应力 测量仪 性能 外文 文献 翻译 中英文