土木工程专业英语原文及翻译

-1-徐州工程学院08级土木(1)班课程考试试卷考试科目专业英语考试时间2011.5.20学生姓名所在院系土木学院任课教师徐州工程学院印制成绩-2-StabilityofSlopes9.1IntroductionGravitationalandseepageforcestendtocauseinstabilityinnaturalslopes,inslopesformedbyexcavationandintheslopesofembankmentsandearthdams.ThemostimportanttypesofslopefailureareillustratedinFig.9.1.Inrotationalslipstheshapeofthefailuresurfaceinsectionmaybeacirculararcoranon-circularcurve．Ingeneral，circularslipsareassociatedwithhomogeneoussoilconditionsandnon-circularslipswithnon-homogeneousconditions．Translationalandcompoundslipsoccurwheretheformofthefailuresurfaceisinfluencedbythepresenceofanadjacentstratumofsignificantlydifferentstrength．Translationalslipstendtooccurwheretheadjacentstratumisatarelativelyshallowdepthbelowthesurfaceoftheslope:thefailuresurfacetendstobeplaneandroughlyparalleltotheslope.Compoundslipsusuallyoccurwheretheadjacentstratumisatgreaterdepth，thefailuresurfaceconsistingofcurvedandplanesections．Inpractice,limitingequilibriummethodsareusedintheanalysisofslopestability.Itisconsideredthatfailureisonthepointofoccurringalonganassumedoraknownfailuresurface．Theshearstrengthrequiredtomaintainaconditionoflimitingequilibriumiscomparedwiththeavailableshearstrengthofthesoil，givingtheaveragefactorofsafetyalongthefailuresurface．Theproblemisconsideredintwodimensions，conditionsofplanestrainbeingassumed．Ithasbeenshownthatatwo-dimensionalanalysis-3-givesaconservativeresultforafailureonathree-dimensional(dish-shaped)surface．9.2AnalysisfortheCaseofφu=0Thisanalysis,intermsoftotalstress，coversthecaseofafullysaturatedclayunderundrainedconditions,i.e.Fortheconditionimmediatelyafterconstruction．Onlymomentequilibriumisconsideredintheanalysis．Insection,thepotentialfailuresurfaceisassumedtobeacirculararc.Atrialfailuresurface(centreO，radiusrandlengthLa)isshowninFig.9.2.Potentialinstabilityisduetothetotalweightofthesoilmass(WperunitLength)abovethefailuresurface．ForequilibriumtheshearstrengthwhichmustbemobilizedalongthefailuresurfaceisexpressedaswhereFisthefactorofsafetywithrespecttoshearstrength．EquatingmomentsaboutO：Therefore(9.1)Themomentsofanyadditionalforcesmustbetakenintoaccount．Intheeventofatensioncrackdeveloping，asshowninFig.9.2，thearclengthLaisshortenedandahydrostaticforcewillactnormaltothecrackifthecrackfillswithwater．Itisnecessarytoanalyzetheslopeforanumberoftrialfailuresurfacesinorderthattheminimumfactorofsafetycanbedetermined．-4-Basedontheprincipleofgeometricsimilarity，Taylor[9.9]publishedstabilitycoefficientsfortheanalysisofhomogeneousslopesintermsoftotalstress．ForaslopeofheightHthestabilitycoefficient(Ns)forthefailuresurfacealongwhichthefactorofsafetyisaminimumis(9.2)Forthecaseofφu=0，valuesofNscanbeobtainedfromFig.9.3.ThecoefficientNsdependsontheslopeangleβandthedepthfactorD，whereDHisthedepthtoafirmstratum．GibsonandMorgenstern[9.3]publishedstabilitycoefficientsforslopesinnormallyconsolidatedclaysinwhichtheundrainedstrengthcu(φu=0)varieslinearlywithdepth．Example9.1A45°slopeisexcavatedtoadepthof8minadeeplayerofsaturatedclayofunitweight19kN／m3:therelevantshearstrengthparametersarecu=65kN／m2andφu=0．DeterminethefactorofsafetyforthetrialfailuresurfacespecifiedinFig.9.4.InFig.9.4,thecross-sectionalareaABCDis70m2.Weightofsoilmass=70×19=1330kN／mThecentroidofABCDis4.5mfromO．TheangleAOCis89.5°andradiusOCis12.1m．ThearclengthABCiscalculatedas18.9m．Thefactorofsafetyisgivenby：-5-Thisisthefactorofsafetyforthetrialfailuresurfaceselectedandisnotnecessarilytheminimumfactorofsafety．TheminimumfactorofsafetycanbeestimatedbyusingEquation9.2.FromFig.9.3，β=45°andassumingthatDislarge，thevalueofNsis0.18.Then-6-9.3TheMethodofSlicesInthismethodthepotentialfailuresurface，insection，isagainassumedtobeacirculararcwithcentreOandradiusr．Thesoilmass(ABCD)aboveatrialfailuresurface(AC)isdividedbyverticalplanesintoaseriesofslicesofwidthb,asshowninFig.9.5.Thebaseofeachsliceisassumedtobeastraightline．Foranyslicetheinclinationofthebasetothehorizontalisαandtheheight,measuredonthecentre-1ine,ish.Thefactorofsafetyisdefinedastheratiooftheavailableshearstrength(τf)totheshearstrength(τm)whichmustbemobilizedtomaintainaconditionoflimitingequilibrium,i.e.Thefactorofsafetyistakentobethesameforeachslice，implyingthattheremustbemutualsupportbetweenslices，i.e.forcesmustactbetweentheslices．Theforces(perunitdimensionnormaltothesection)actingonasliceare：1.Thetotalweightoftheslice，W=γbh(γsatwhereappropriate)．2.Thetotalnormalforceonthebase，N(equaltoσl)．Ingeneralthisforcehastwocomponents，theeffectivenormalforceN'(equaltoσ'l)andtheboundarywaterforceU(equaltoul)，whereuistheporewaterpressureatthecentreofthebaseandlisthelengthofthebase．3.Theshearforceonthebase，T=τml.4.Thetotalnormalforcesonthesides,E1andE2.5.Theshearforcesonthesides，X1andX2.-7-Anyexternalforcesmustalsobeincludedintheanalysis．TheproblemisstaticallyindeterminateandinordertoobtainasolutionassumptionsmustbemaderegardingtheintersliceforcesEandX：theresultingsolutionforfactorofsafetyisnotexact．ConsideringmomentsaboutO，thesumofthemomentsoftheshearforcesTonthefailurearcACmustequalthemomentoftheweightofthesoilm