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1、8InstallationofPilesinMarineandOffshoreStructure8.1GeneralPilingformarineandoffshorestructuresmustbeinstalledtodeveloptherequiredcapacitiesinbearing,uplift,andlateralresistance.Foroffshorebridgepiers,minimizationofsettlementsmayalsobecriteria.Stiffne
2、ssunderlateralloads,aswellasstrength,andtheabilitytoacceptoverloadsinaductilemodearealsoimportantcharacteristics.Forharborstructures,suchaswharvesandquays,andfortrestle-typebridges,prestressedconcretepilesarecommonlyemployed.Onceinplace,theirstrength
3、andrigidity,resistancetobuckling,anddurabilityoftenrenderthemthemostsuitable.However,stressesandstrainsoccurduringdriving,forwhichtheymustbeadequatelyprestressedtoresisttensionreboundcracksandmusthaveadequateconfiningspiralorhoopstoresistlateralbursti
4、ngstressesduetoPoisson’seffect.Thereboundtensionisatamaximuminsoftdrivingattheinitiationoftheinstallation.Thisiscontrarytointuition.Typicalpilesforharborworkarelargerandmoreheavilyreinforcedthanthoseemployedinlandfoundations.SteelHpileshavebeenusedas
5、thebearingpilesinbridgepiers,especiallywhenthefootingblockisatorbelowtheseafloororriverbottomlevelanddifficultdrivingisanticipated.Pileshoesarevaluableinresistinglocalbucklingatthepiletip.SteelHpilesandsmall-diameterpipepilesareoftenusedastensionpiles.
6、Toincreasetheirresistancetopull-out,theymaybefittedwithsteelplatefinsorspiraledplates.Alternatively,groutpipesmaybeattachedandgroutinjectedunderpressure,thusenlar-gingthezoneofanchorage.Ineffect,theyarebecominghigh-capacitygroundanchors.Micropilesaresm
7、alldiameterpipepiles,300-to500-mmsteelpiles,drilledintorockorsimilarcompetentmaterial,oftenemployedtoresistbothcompressionandtension(uplift).Ahighstrengthsteelbarorclusterofbarsisinsertedandthepilegroutedinthesocketedannulus.Themicropiletubularisthen
8、filledwithgrout,bothforreasonsofdurabilityandtoenablethemicropiletocarrycompressiveload.Sometimesitisfilledwithnon-corrosivegreaseinordertopermitelongationunderitsdesignload.Deepwater,long,unsupportedcolumnlengths,largecyclicbendingforces,andlargelater
