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1、StiffnessofsoftrocksfromlaboratorytestsM.Barla,G.Barla,D.C.F.LoPresti,O.PallaraDepartmentofStructuralandGeotechnicalEngineering,PolitecnicodiTorino,ItalyN.VandenbusscheEcoleNationaledesPontsetChaussées,Paris,FranceABSTRACT:Thestressstrainstrengthpropertiesofvarioussoftrockshavebeenev
2、aluatedbymeansoftestsperformedwithaspeciallydevisedtriaxialapparatus(Hayanoetal.1997,Tatsuoka1988)havingthefollowingcharacteristics:i)verylowcompliance;ii)accurate,localmeasurementsfortheaxialandradialstrains;iii)highresolutionoftheactuator;iv)slidingmechanismatthebottomofthepedestal
3、.Thesamplestestedweretakenfromtwosedimentarysoftrocks:i)Miocenesiltymarlinterbeddedwithsandstone(S.RaffaeleCimena,Italy)andii)latePliocenetoearlyPleistocenemudstone(Sagamihara,Japan),wellcementedandmostlyunweatheredandcontinuous(Kimetal.1994,Hayanoetal.1997).Moreover,twotestswereperf
4、ormedonspecimensofheighlytectonisedcarbonaticbreccia(Giaglionesite,Italy).Inparticularthefollowingaspectshavebeenconsidered:i)theinfluenceofCaCO3contentonstrengthandstiffnessinthecaseofS.RaffaeleCimenasandstone;ii)theimportanceoflocalstrainmeasurements;iii)theimportanceofendcapping;i
5、v)thecomparisonofthestiffnessinferredfrominsituandlaboratorytests,aswellasfromrockmassratingsystemsinthecaseofcarbonaticbreccia.1.INTRODUCTIONTwoimportantproblemshavereceivedlittleattention:-howtofacetheproblemofsoildepositsorrockTheimportanceofaccurateassessmentofsoilstiffness,masse
6、sthatexhibitahighspatialvariabilityatthefromverysmallstrainstopeak,iswidelyrecognised.mechanicalproperties;Severalwelldocumentedcasehistorieshaveshownthat-howtoinferthestiffnessofadiscontinuousrocktheobservedsettlementsunderworkingloadconditionsmassfromEs(local).ofwelldesignedfoundat
7、ionsonstiffsoilsorsoftrocksThispaperdealswiththefollowingtopics:aregenerallylessthan0.1%(Simpsonetal.1979,-assessmentoftheEmax/qmaxratioforavarietyofBurland1989,Tatsuokaetal.1995a).Backanalysessoftrocks.ThespatialvariabilityofEmaxcanbebasedonthisdatahaveshownthatcorrectstiffnessinfer
8、redfromtheva