岩土工程中的裂隙 及孔隙

ORIGINALARTICLEGeotechnicalmodelingoffracturesandcavitiesthatareassociatedwithgeotechnicalengineeringproblemsinKualaLumpurlimestone,MalaysiaSamyIsmail•ShattriMansor•AhmedRodsi•B.K.BujangReceived:2March2009/Accepted:9February2010/Publishedonline:25March2010Springer-Verlag2010AbstractThisstudypresentsamodifiedgeotechnicalmodelofsubsurfacecavitiesandfracturesthatareassoci-atedwithfoundationandpillingproblems.Thetopo-graphicalmodelwasusedtoautomaticallyextractminimumsurfacecurvature,slope,andpits.Theimageprocessingshowsthatmorethanfourteenregionalfaults,trendingNE,SW,andWNWaffecttheKualaLumpurlimestonebedrockandthesurfacetopographyfromSouthtoNorth.Thesefracturesoftenshowhigherprobabilityofpilingandconstructionsproblems.Thefaultsaretensional,lowlying,andwrenchoflength10–20km.Opencastex-miningpondfloors(bathymetry)aregoodindicatorsofsubsurfacefracturesandcavitiesthataffectthelimestonebedrock.TheLANDSATimage(bandone)showsthatthefracturesofopencastex-miningpondfloorshavethesametrendastheregionalfaults.Thesetechniquescanhelpgeotechnicalengineerstopredictsubsurfacefracturesandcavities,especiallyinareasadjacenttoex-miningponds.Inbrief,mostofthesubsurfacecavitiesandex-miningponds,forexamplethePhongFattpond,arelocatedonandalongfaultzones.KeywordsKualaLumpurSetapakEx-miningCavitiesKennyHillformationIntroductionIntropicalregions,thecontinuousdissolutionofcarbonaterocksalongfaultzonesandintersectedfracturesmaybeleadtotheoccurrenceofearthdepressionsonalargescaleand/orafewmeters(Johnson1989;Hill1996),largecol-lapse(Gutierrez1996),concordantsynclinalvalleys(Gustavson1986),andexcavationwallcollapse(Tan2006).Inadditiontogeotechnicalengineeringproblems,thishasledtotheswallowingofmanypeopleandinfra-structuresallovertheworld(Gutierrezetal.2008).Themainproblemsconfrontedbyengineersdesigningstructuresinkarstterrainaredifficultiesinexcavationandgradingthegroundoverpinnacledrockheads,collapseoftheroofoversubsurfacevoids,subsidenceofcoversoiloversinkholes,difficultiesinfoundingastructureoveranirregularorpinnacledrockhead,lossofwaterfromdamreservoirs,andpollutionofgroundwater(Xeidakisetal.2004).Inthiscontext,thefractures,cavities,andpinnaclesofKualaLumpurlimestonebedrockarecommonfeaturesassociatedwithpreconstructionandproblemswithfoun-dations(Fig.1).Forexample,thePetronasTwinTowersinKualaLumpurwereshiftedabout50mfromtheirorigi-nallyplannedpositions(onKualaLumpurlimestone)becauseoftheintensefracturesandlimestonecavitiestositentirelywithintheresidualsoilsandmetasediments(KennyHillformation)(Azametal.1996).AquickreviewofgeologicalandgeotechnicalmapsoftheMalaysianGeosciencesandSurvey(GSM),andpre-viousgeophysicalreports,giveslittleinformationaboutS.Ismail(&)S.MansorA.RodsiInstituteofAdvancedTechnology(ITMA),Selangor,Malaysiae-mail:[e-mail]-mail:[e-mail]-mail:[e-mail]partment,FacultyofEngineering,UniversityPutraMalaysia(UPM),43400Serdang,Selangor,Malaysiae-mail:[e-mail]123EnvironEarthSci(2011)62:61–68DOI10.1007/s12665-010-0497-3subsurfacecavities,faults,andfractures.Forexample,thesubsurfacelimestonebedrockdelineatedinKg.Baruvil-lageduringtheLightRailTransit(LRT)projectwasnotdelineatedintheexistinggeologicmap(GueandTan2001).Insuchareasandterrain,identificationoffracturesandcavitiesbyuseoftraditionalgeophysicalsurveyingistimeandcost-consumingbecauseofdensevegetation,spreadingurbanization,highnoiseinterference,andsoilmoisturethatattenuatestheelectromagneticwaves.How-ever,thisstudyispresentedtoovercomethelimitationsofthesemethods.Nowadays,theactiveremotesensinganddigitalelevationmodelandlightdetectionandranging(LIDAR)givegood,costandtime-effective,resultsforchangesintheelevationoftheearth’ssurfaceonalargescale.Inremotesensing,theobscuringvegetationissometimesindicativeofgeologicalstructuressuchasfaults,joints,andundergroundstreams(channels).Inaddition,itissubtlyaffectedbytheunderlyinggeologyand,especially,thepresenceofanomalies.Theaspect,slope,maximumcurvature,andlongitudinalprofil-ingarepowerfulcomponentsoftopographicalmodelsdelineatingthesurfacetopographyoflimestoneandkarstfeaturesassociatedwithgeotechnicalengineeringproblems.Tectonic,geomorphologicstudies,andrivernetworkanal-ysiscanbeperformedmorerapidlyandeasilybyuseofdigitalelevationdataandgeographicalinformationsystems(Jamiesonetal.2004;Jordan2003;Korupetal.2005;Mayer2000;Oguchietal.2003;Szynkaruketal.2004).ThestudyareaThestudyareaislocatedfromlongitude101.35Eto101.50Eandfromlatitude3Nto3.15N;thetotalareaisapproximately236,827km2(Fig.2).Geographically,KualaLumpurissituatedinthebroadvalleyoftheRiverKlang,whichconsistsofaflatalluvialplainwithopencastex-miningponds(Yeap1985,1987).Itisboundedbyhillspredominantlyofgraniticrocktothewestandeastandmetasediments(KennyHillFormation)southwest(Fig.3).Approximately40%ofKualaLumpurisunderlainbyfracturedlimestone(totalarea236,827km2).GeologicalsettingofthestudyareaThegeologicalStratigraphyofKualaLumpurareastartswiththeoldersuccessioncalledtheHawthorndenforma-tion