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1、HSoil/RockSurfaceandBuriedStructuresH.1GeneralIntroductionAgreatdealofinformationisgiveninthistextonimpactandexplo-sioninthefieldofgroundengineering.Inthissectionafewexamplesaregivenonimpact/explosionoccurringatgroundlevelorbelow,withspecialemphasisonthepredictionofthepenetrationof
2、missiles/projectiles/bombsinsoil/rockmedia.TableH.1listspropertiesanddimensionsofsomewellknowncombinationsofsoilsformingparticularstrata.H.2SoilStrataSubjecttoMissileImpactandPenetrationThemostimportantobjectiveistomodelindetailboththetargetsoilandthepenetratingmissile.Themodellin
3、gofthesoilasatargetmaterialpresentsaproblemwhichstemsfromthefactthatinsitusoil/rockisanon-linearanistropicmaterialandisfurthercomplicatedbyvariationsintheexistinglayeredstrata.A20-node,three-dimensional,isoparametric,dynamicfinite-elementmethodwasadoptedforthetargetmaterial,asshown
4、inFig.H.1.Eachlayerwasmodelledwithrespectivematerialproperties.Twotypesofexpansioncavities,namelycylindricalandspherical,weremodelled.Usingthecylindrically-expandingcavity,thetargetmaterialwasassumedtomoveradiallyonwardsasthemissilepenetrated.Theradialpressureinthecylindri-calcavi
5、tywasthenassumedtobeactingnormallyonthepenetratorsurface.Wheretherewasanangleofattack,apartfromaxialvelocities,anangularvelocitywasintroducedtothepenetratorasandwhentheangularorientationofthepenetratoroccurs.Whereasphericalcavityisassumed,thetargetmaterialwasthenassumedtomoveinadi
6、rectionnormaltothesurfaceofthemissile/bombpenetrator.TheISOPARprogramusesbothmethodssimultaneouslyintheanalysisofthe1078HSoil/RockSurfaceandBuriedStructuresTableH.1.SelectedstrataastargetsTargettypeSoildescriptionDepth(m)SoilconstantI(a)Clayeysilt,siltyclay,hardand0–85.18dry(b)San
7、dysilty,densedryandwell8–152.48cemented(c)Clay,siltyandsoft0–1.640.00(d)Sand,silty,clayeydensedryto15–245.10dampIIClay,soft,wet,varied,mediumto0–448.00highplasticityIIIIceglacier0–204.10IVSilt,clayeypermafrost0–103.55VSandloosetomedium,verymoist0–226.70VIStiffclay0–59.75VIISandston
8、e0–101.35VIIIFinegrainedrock0–41.
