英文翻譯綜述Theabsenceofcatastrophicconsequencesresultingfromcrackformationcanbeexplainedbythecompara-tivelyshallowdepthofcrackdevelopmentandtheeffectiveperformanceofthedrainage,whichisamandatorystructuralelementforthedamandsubsurfacecontour.Fulfillmentoftheabove-citedstandardrequirementsresultsinthefactthatthecompressivestrengthoftheconcreteisnotfullydeveloped(usuallyby10-15%),Asaresult,thevolumeofagravitydam,asarule,signifi-cantlyexceedsthevolumeofabuttressdam,inwhichthepropertiesofthematerialaremorefullyutilized.Asaresultofthis,thegravitydamisfrequentlynotconsidered,althoughitalwaysattractsattentionduetothesim-plicityofitsdesign,whichmakesitpossibletoemploythemostinexpensivemeansofplacingconcrete;toitssize,whichissmallerthanothertypesofdams;tothedependenceonthequalityofthefoundation;andtothepossibilityofobtainingacompactgroupingofbasicstructureswithinthehydraulicfacility.Theseadvantagesofferedbygravitydamscompelustosearchfornewmeansofimprovingtheirdesigninordertoreducetheircost.Asoneapproach,wecanproposethefollowing:Selecttheshapeofthedamfromthecompressivestrengthoftheconcreteinthezoneofitsdownstreamface,thestrengthofthefoundationbeneathitsbase,andtheabilityofthedamasawhole,andofitsindividualparts,toresistplaneshearandoverturning;Assumingtheformationandexposureofcracks,donotrestrictthemagnitudeofthetensilestressesintheupstreamface,includingthecontactzone;Inordertoexcludethecounterpressureexertedbywaterinthecracksandtorealizestructuralmea-sures:a)Installananti-seepagecurtainontheupstreamfaceanddevelopadrainagesystemdirectlybehindit,assumingthatthebasicpurposeofthecurtainistominimizetheseepageintothedrainagesystem;and,b)carrythegroutcurtainupstreamandconstructareliableunionbetweenitandthedam.Theeffectoftheconditionsrequiredforthestateofthepressure(upstream)faceandthelevelofstressesinthegravitydarnmass(withobservanceofstandardrequirementsconcerningtheshearstrengthwithabasicloadingcombination)isillustratedgraphicallyinTable1andinFig.1.Acomparisonofdamshapesismadewithtan~0=0.75andC=25tons/m2.Thevolumesrepresentedbytheshapesaregivenincludingcouplingbetweenthedamandcurtain.AlessmassivegravitydamwasdesignedinaccordancewiththeseprinciplesfortheconditionsprevailingattheKurpsaihydraulicfacility(1973)bytheAll-UnionLeninOrderS.Ya.ZhukScientific-ResearchInstituteforDesignandExploration.Aswepassovertheproblemofgroupingswhichshouldbecloselylinkedwiththestructuralandtechnologicalcharacteristicsofthedam,wecanonlyprovideadescriptionofthedesignsthatguaranteereliableserviceofadamwherecracksarepermissibleintheupstreamfaceandalongthecontactwiththefoundation,andtheresultsofcomputationsandexperimentalinvestigations.Adam(Fig.2)withamaximumheightof124misexaminedunderaheadof99manda9-pointearth-quake.Aninterstratifiedblockofsandstonesandargfllites,whichisinclinedatanangleof55-65*tothehori-zontal,servesasthefoundation.Themodulusofelasticityofthefoundationisincreasedfrom(20-50)x103skg/cm2intheunloadedzoneto(100-150)x103kg/cm2inthedeepzone.Theworkingvaluesoftheshearparam-etersinthesafe-rockzonearetakenastan~0=0.75andC=2.5kg/cm2.Alongfaultplanes.Ordinarily,thedesignandestimateforastoragedamshouldprovidefortheinjectionofgroutunderpressuretosealseamsjoints,andotheropeningsinthebedrocktoadepthequaltothereservoirheadabovethesurfaceofthebedrock.Groutingisusuallydonewithneatcementandwaterstartingwitharatiofo1:5.Ifconsiderable“take”inanyoneholeisexperienced,thegroutmixtureisthickenedprogressivelyuntilaratioof1:1isobtained.Admixture,suchassandorday,areaddediflargevoidsareencountered.□Forsmalldams,asinglelineofgroutholesissufficientoGroutingofrockfoundationsordinarilywillnotberequiredfordetentiondams,verysmalldiversionandstoragedams,orwherepreconstructionexplorationhasdemonstratedthattherearenoopeningsinthebedrocks.Veryoftenisfoundtobebadlyjointedorbrokenforsomedepthbelowitsstructure.Insuchinstances,aconcretegroutcapmaybeneededtofacilitategrouting.Thtgroutcapisusuallyaconcrete-filledtrenchexcavatedaminiumof3feetandamaximumof8feetinthebedrock,depengdingonconditions.Thetrenchisusuallymadeaminimumwidthof3feettofacilitateconstruction.°Thegroutcapperformsseveralfunctions:(l)Itprovidesanchorageforthepipenippletowhichthegroutpumpisconnected;(2)itcutsoffseepageintheupperportionofthebedrockwhichcannotbesuccessfullygrouted;and(3)itprovidesweightsothathighergroutingpressuremaybeusedatshallowdepth。excavationforthegroutcapmustbecarefullyperformedsothattherockisnotshattered.TypicalspecificationsfortheperformanceofgroutingandtheexcavationforthegroutcapareincludedinappendixG.However,ifanextensivegroutingprogramisrequiredintheconstructionofadam,consultingadiviceshouldbeobtainedfromanengineerexperiencedinthistypeofwork..Foradditionalinformationonthesubjectofgrouting,includingtheexperiencesofthebureauofreclamation,theU.S.CorpsofEngineers,andtheTennesseeValleyAuthority,refertotheAmericanSocietyofCivilEngineers'paperswhichcomprisethe"SymposiumonCementandClayGroutingofFoundation^Concretecutoffwallswereformerlyprovidedevenforsmalldamstointerceptseepagealongthecontactoftheembankmentwiththerockfoundation,thesewallsareexpensiveandareordinarilynotrequiredforsmallearthfilldamsofthetyperecommendedinthistext,providedthatcareistakentoobtainanintimatecontactbetweentheimperviousportionofthedamand