简介：Athree-stepfiniteelementmethod(FEM)togetherwithLargeEddySimulation(LES)isap-pliedtoincompressibleturbulentflowaroundseabedpipelinesatrelativelyhighReynoldsnumbers.Bothtwo-dimensionalandthree-dimensionalnumericalsimulationiscarriedouttodeterminethethree-dimensionaleffect.Theresultsofnumericalsimulationagreequitewellwiththewaveforcesactingonpipelinemodelsmeasuredinphysicalmodeltest.

简介：BasedonBiot'sconsolidationtheory,atwo-dimensionalmodelforcomputationoftheseabedresponsetowavesispresentedwiththefiniteelementmethod.Numericalresultsfordifferentwaveconditionsareobtained,andtheeffectsofwavenon-linearityonthewave-inducedseabedresponseareexamined.Moreover,thewave-inducedmomentaryliquefactioninuniformandinhomogeneousseabedsisinvestigated.Itisshownthatthewavenon-linearityaffectsthedistributionofthewave-inducedporepressureandeffectivestresses,whiletheinfluenceofwavenon-linearityontheseabedliquefactionpotentialisnotsosignificant.

简介：Wave-inducedtransientresponseofdisplacements,effectivestressesandporepressureinsaturateseabedaresalvedbyaconsolidationfiniteelementmethod.Theinfluenceoftheresponsestothestabilityofseabedandcoastalstructuresisshownbyanimprovedslicemethodwithcirculararcslipsurface.Dynamicelasticconsolidationtheoryandlinearpermeabilitytheoryareemployedinthesolutionofseabedresponse.Theseabedcanbeconsistedoflayeredsoilwitharbitraryboundaries.Theactingwavecanberegularorirregular.Irregularwavepressureactingonthesurfaceofseabediscalculatedbylinearsuperpositionmethod.Wave-inducedexcessstressontheslipsurfaceisconsideredinthestabilityanalysis.Thespatialandtemporalvariationsofporepressureinsandyseabedcomparewellwithexperiment.Calculationsforaverticalbreakwatershowthatthesafetyfactorofseabedandstructurewilldecreaseifwave-inducedseabedresponseisconsidered.Thescopeofdecreaseismainlyre

简介：Inestuarineandcoastalareas,theseabedisinaconstantprocessofdynamicchangeundermarineconditions.Seabedsedimenterosionandresuspensionareimportantprocessesthatsafelycontrolthegeologicalenvironment.FieldtripodobservationsconductedintheJiaozhouBayinChinaarereported,toinvestigatetheeffectsofhydrodynamicconditionsontheerosionandresuspensionprocessesoftheseabed.Theobservationalresultsshowthatthemaximumshearstresscreatedbytidalcurrentscanreach0.35N/m~2,whichishigherthanthewave-inducedshearstressduringfairweatherconditions.Aseabederosionfrequentlyoccursduringthefloodtide,whereasaseabeddepositionoccursduringebbtide.WavescanproduceabottomshearstressapproximatelyequivalenttothatinducedbycurrentswhenthelocalwindreachesForce4withaspeedof5m/s.Whenthewindreaches7m/sandthesignificantwaveheightreaches26cm,wavesplayamoresignificantrolethancurrentsinthedynamicprocessesoftheseabedsedimentresuspensionandleadtoahighvalueofturbiditythatisapproximatelytwotoeighttimeshigherthanthatinfairweather.Theseanalysesclearlyillustratethatperiodiccurrent-inducedsedimenterosionandresuspensionaredominantinfairweather,whereasepisodichighwavesareresponsibleforsignificantsedimentresuspension.AdditionalworkisneededtoestablishamorethoroughunderstandingofthemechanismsofsedimentdynamicsintheJiaozhouBay.

简介：Anewseabedsedimentfidelitysamplerwasdevelopedanditsthermalinsulationperformancewasstudiedandanalyzed.Thetemperaturedistributionsimulationindicatedthatthesamplequalitycouldbeinsuredbyusingthisnewsampler.BasedonANSYS10,thetemperaturefiniteelementmodelofthesamplecylinderwasestablished.Accordingtothelawofconservationofenergy,theunsteadyheattransmitequationofthesamplerundersolid-liquidcouplingconditionwasderived,thenthemathematicalmodelcalculationwascarriedoutbyusingamixedfinite-elementfinite-differencemethod,andtwothermalinsulationmethodswereused.Thesimulationwascarriedoutbyusingthethicknessofthethermalinsulationlayerandheatconductivityasthevariableparametersandthetemperaturedistributionofthesamplerandrelatedinfluencingfactorswereobtained.Optimizationanalysiswasconductedusingthesimulationdataandrelatedparametersandthemagnituderangesoftheparameterswereobtainedthatcouldmeetthedesigntemperaturerequirements.Theexperimentaldataandsimulationresultsindicatedthattheresultswereingoodagreementwiththerealities,andthissamplermightbeofvalueforseabedsedimentsamplerdesignandmanufacture.

简介：Anumericalmodel,EvolutionEquationofMild-SlopeEquation(EEMSE)developedbyHsuetal.(2003),wasappliedtostudytheBraggreflectionofwaterwavesoveraseriesofrectangularseabed.ThreekeyparametersoftheBraggreflectionincludingthepeakcoefficientofprimaryBraggreflection,itscorrespondingrelativewavelength,andthebandwidth,haveshowntobeeffectiveindescribingthecharacteristicsoftheprimaryBraggreflection.ThecharacteristicsoftheBraggreflectionwereinvestigatedunderthevariousconditionscomprisingnumber,height,andspacingintervalofaseriesofrectangularseabed.TheresultsrevealthatthepeakofBraggreflectionincreaseswiththeincreaseofrectangularseabedheightandnumber,thebandwidthandtheshiftvalueoftheBraggreflectiondependontheincreaseoftherectangularseabedheightaswellasthedecreaseofrectangularseabednumber,andtherelativerectangularseabedspacingintherangof3and4couldproducehigherBraggreflection.Finally,acorrelativeandregressiveanalysisisperformedbyuseofthecalculateddata.Basedontheresultsoftheanalysis,empiricalequationswereestablished.Ourstudyresultscanprovideanappropriatechoiceofaseriesofrectangularseabedfieldforapracticaldesign.

简介：-Thecyclicrotationofprincipalstressdirectionwithaconstantamplitudeisthecharacteristicsofcyclicstressinseabeddepositinducedbytravellingwaves.Presentedinthepaperaretheresultsobtainedfromtestssimulatingthecyclicstresscharacteristics,withemphasislaidonthebuildupofporewaterpressureinsoilsamples.Regressionanalysisoftestdatashowsthattheporewaterpressurecanbeexpressedasthefunctionofthenumberofcyclesofcyclicloading,orasthefunctionofgeneralizedshearstrain.Usingtheresultsthusobtained,thepossibilityoffailureofseabeddepositundercyclicloadinginducedbytravellingwavescanbeevaluated.Thecomparisonwiththeresultsofconventionalcyclictorsionalsheartestsshowsthatneglectoftheeffectofthecyclicrotationoftheprincipalstressdirectionwillresultinconsiderableover-estimationofthestabilityofseabeddeposit.

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简介：Ascientifichypothesisisproposedandpreliminarilyverifiedinthispaper:underthedrivingofseepageflows,theremightbeaverticalmigrationoffine-grainedsoilparticlesfrominteriortosurfaceofseabed,whichisdefinedas‘sub-bottomsedimentpumpaction’inthispaper.FieldexperimentswereperformedtwiceontheintertidalflatoftheYellowRiverdeltatostudythisprocessviabothtrappingthepumpedmaterialsandrecordingtheporepressuresinthesubstrate.Experimentalresultsarequiteinterestingaswedidobserveyellowslurrywhichismainlycomposedoffine-grainedsoilparticlesappearingontheseabedsurface;seepagegradientswerealsodetectedintheintertidalflat,undertheactionoftidesandsmallwindwaves.Preliminaryconclusionsarethat‘sedimentpump’occurswhenseepageforceexceedsacertainthreshold:firstly,itisbigenoughtodisconnectthesoilparticlesfromthesoilskeleton;secondly,thedegreeofseabedfluidizationorbioturbationisbigenoughtoprovidepreferredpathsforthedetachedmaterialstomigrateupwards.Thentheywouldbefirstlypumpedfrominteriortothesurfaceofseabedandtheneasilyre-suspendedintooverlyingwatercolumn.Influentialfactorsof‘sedimentpump’aredeterminedashydrodynamics(waveenergy),degreeofconsolidation,indexofbioturbation(permeability)andcontentoffine-grainedmaterials(sedimentaryage).Thisnewperspectiveof‘sedimentpump’mayprovidesomeimplicationsforthemechanisminterpretationofseveraluncleargeologicalphenomenaintheYellowRiverdeltaarea.