泥石流凍土課件

環(huán)境地質(zhì)學(xué)

EnvironmentalGeology

主講人：萬新南教授

Prof.Wanxinnan環(huán)境地質(zhì)學(xué)

EnvironmentalGeology第三講Partthree地球表層的塑造過程

第三講環(huán)境地質(zhì)學(xué)

EnvironmentalGeology6、Pre降水、江河與洪水

7、MassWastingProcesses表層整體再塑（滑坡、泥石流、溶蝕、塌陷）8、海岸線與海岸塑造過程

9、生態(tài)與植被Partthree地球表層的塑造過程

第三講環(huán)境地質(zhì)學(xué)

EnvironmentalGeology

7、MassWastingProcesses

表層整體再塑（滑坡、泥石流、溶蝕、塌陷）Partthree地球表層的塑造過程

第三講環(huán)境地質(zhì)學(xué)

EnvironmentalGeologyMassWastingProcessesThereisnothinginorganic....Theearthisnotamerefragmentofdeadhistory,stratumuponstratumliketheleavesofabook,tobestudiedbygeologistsandantiquaries古玩家chiefly,butlivingpoetryliketheleavesofatree,whichprecedesflowersandfruit-notafossilearth,butalivingearth....

HenryDavidThoreau

Partthree地球表層的塑造過程

第三講環(huán)境地質(zhì)學(xué)

EnvironmentalGeologyMassWastingProcesses

A、Flowingsand,landslides,androckfallsareexamplesofmasswasting,thegeneraltermforgravitationallyinduceddownslopemovementofdebris.B、Mass-wastingprocessesoperateonslopinglands;eventuallythedebrisreachesastreamorgullywherefluvialprocessescontinuetheerosionalprocess.Partthree地球表層的塑造過程

第三講環(huán)境地質(zhì)學(xué)

EnvironmentalGeologyMassWastingProcessesPartthree地球表層的塑造過程

第三講環(huán)境地質(zhì)學(xué)

EnvironmentalGeologyMassWastingProcessesRockfallOneoftheworld'smostfamoustalusslopesistheonewhichformedanimpedment障礙toprospectors開拓者duringtheKlondikegoldrushof1898.thesnow-coveredtalusslope,calledtheScales,wastheonlyaccesstoChilkootPassandtheYukonRiver.ThepasswasguardedbytheCanadianNortheastPolice,whorequiredeveryprospectortocarry1tonofsuppliesuptheslopeandintotheinterior.Partthree地球表層的塑造過程

第三講環(huán)境地質(zhì)學(xué)

EnvironmentalGeologyMassWastingProcessesOneoftheworld'smostfamoustalusslopesistheonewhichformedanimpedment障礙toprospectors開拓者duringtheKlondikegoldrushof1898.thesnow-coveredtalusslope,calledtheScales,wastheonlyaccesstoChilkootPassandtheYukonRiver.ThepasswasguardedbytheCanadianNortheastPolice,whorequiredeveryprospectortocarry1tonofsuppliesuptheslopeandintotheinterior.

Partthree地球表層的塑造過程

第三講環(huán)境地質(zhì)學(xué)

EnvironmentalGeologyMassWastingProcessesCreepCreepistheslow,downslopemovementofsoil,weatheredrock,orothersurficialdebris.Movementisbyquasiviscousflow,occurringundershearstressessufficienttoproducepermanentdeformation,buttoosmalltoresultinadiscretefailuresurfacesuchasalandslide.Partthree地球表層的塑造過程

第三講環(huán)境地質(zhì)學(xué)

EnvironmentalGeologyMassWastingProcessesCreepCreepmaybecausedbynumerousphenomena.Forexample,interrainssubjecttofrost,rockorsoilmaygetheavedupperpendiculartotheslopeuponfreezing,andreturnedverticallydownwardduringathaw.Thus,overtime,materialonaslopeislikelytomovedownhill.Micro-landslidesandrandommovementssuchasoverturnedtrees,etc.,allcontributetocreep.

Partthree地球表層的塑造過程

第三講環(huán)境地質(zhì)學(xué)

EnvironmentalGeologyMassWastingProcessesLandslidesLandslideistheprocesswherebyadistinctmassofrockorsoilmovesdownslopeduetogravity.Landslides,unlikecreep,haveoneormoredistinctfailuresurfaces.Landslidevelocitiesaretypicallyontheorderof1m/daytoperhaps300km/hrasinthespecialcaseofair-entrappedlandslidesgeneratedbyearthquakes.Shreve(1968)believesthattheprehistoricBlackhawkLandslideinCaliforniaslidatimmensespeedsonalayerofcompressedairthatwastrappedbeneaththedebris.Thelandslide,consistingof320millionm3,traveled8kmacrossadesertflooratanaverageslopeof2.5°.[Hsu(1975)challengestheairlubrication空氣潤滑hypothesis假說infavorofadebrisflowmobilizedbycollisionofparticleswithinadust-ladencloud.].Partthree地球表層的塑造過程

第三講環(huán)境地質(zhì)學(xué)

EnvironmentalGeologyMassWastingProcessesLandslides

Landslideactivitytypicallyincreasesafterprolongedrains,orafterthefrostleavesthegroundinthespring.ThenovelistFirtsch(1980)describestheominoushazardoflandslideswhichweighsheavilyonthemindsofpeoplewholiveinthesteepslopesoftheSwissAlps:Partthree地球表層的塑造過程

第三講環(huán)境地質(zhì)學(xué)

EnvironmentalGeologyMassWastingProcessesLandslides

Classificationoflandslides.Forsimplicity,landslidescanbeclassifiedintotwogroups:1)translational,and2)rotational.Partthree地球表層的塑造過程

第三講環(huán)境地質(zhì)學(xué)

EnvironmentalGeologyMassWastingProcessesLandslides

Translationallandslides(Fig.6.8)slidealongabeddingplaneorotherplaneofweaknessintherock.Theentiremassmovesparalleltothisplane,asillustratedintherockslideinFig.6.1.Partthree地球表層的塑造過程

第三講環(huán)境地質(zhì)學(xué)

EnvironmentalGeologyMassWastingProcessesLandslides

Probablythelargesttranslationallandslidetooccurinhistorictimeshappenedin1925intheGrosVentreRiverValleyinWyoming(Fig.6.8A).About40millionm3ofPennsylvaniaTensleepSandstoneslidonabeddingplaneinclinedabout20°.Heavyrainandstreamundercuttingatthebaseofthemountainslopecontributedtothefailure(Voight,1978).A45km2lakeformedbehindthedebris;twoyearslaterthedamwasovertoppedbyheavyspringrunoff,andsixpeopledrowned淹死intheensuing跟著發(fā)生flood.The1903landslidedisasterattheminingtownofFrank,Alberta,wasatranslationalslidewhichdevelopedalongaprominentsetofjointswhichdipintothevalley.Partthree地球表層的塑造過程

第三講環(huán)境地質(zhì)學(xué)

EnvironmentalGeologyMassWastingProcessesLandslides

Rotationallandslides(“slumps”or“slips”)developinsurficialdepositsorweatheredrock(fig6.1).Theymaybenaturalinoriginorinducedbyman.Thefailuresurfaceisroughlyarcuate弧形incrosssection(spoon-shapedinthreedimensions).Atsomeplacestheoccurrenceofalandslideatthebaseofahillmayleavethehillslopeaboveunsupported,andsoanotherlandslideoccurs(Crandell,1951).Thechain-reactiontypeofstair-steppingslopefailureupahilliscalledprogressivefailure.Partthree地球表層的塑造過程

第三講環(huán)境地質(zhì)學(xué)

EnvironmentalGeologyMassWastingProcessesLandslides

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Mathematicalanalysis.MathematicalmodelsoflandslidestabilityarepresentedinTerzaghi(1950;1962),Scheidegger(1961).Stout(1969),Jaeger(1972),SchusterandKrizek(1978),andHuang(1983).Mostproblemsinvolvingthestabilityofslopesareassociatedwiththedesignandconstructionofunbraced無支擋cutsforhighways.Averygeneralizedrule-of-thumbisgivenbyTerzaghiandPeck(1948):Partthree地球表層的塑造過程

第三講環(huán)境地質(zhì)學(xué)

EnvironmentalGeologyMassWastingProcessesLandslides

Theroleofrockanisotropiesisveryimportantinthedesignofstableslopes.Fig4.24showsanexampleofastereographicsolutionofapossiblewedgefailureduetotwoprominentplanaranisotropiesonadeepcut.TheuseofstereoplotsinanalysisofslopestabilityisexplainedinotherChapter.Partthree地球表層的塑造過程

第三講環(huán)境地質(zhì)學(xué)

EnvironmentalGeologyMassWastingProcessesLandslides

ConsiderthelandslidecrosssectionshowninFig.6.16havingaunitthicknessof1m.Assumethedebrisconsistsofthreelayersofknowndensityandshearingstrengthasshown.Firstassumeatrialfailureplane#1(ABCD).Theslidecanbearbitrarilydividedintoaconvenientnumberofslices,andthemomentofeachcomputed.Accuratedraftingandmeasurementofmomentarmsisnecessary.Thesumoftheeightdrivingmomentsis29,507kN-m.Theresistingmomentisthendetermined,andisequaltotheshearingstrength(inthiscasetheso-calledundrainedshearstrengthSuisused)timesthelengthofarcineachslicetimesthemomentarm.Thesumoftheresistingmomentsiscalculatedtobe34,500kN-m.Thefactorofsafety,F.S.,isequaltotheratioofresistingmomenttodrivingmoment:F.S.(2.2.9)Inthiscase:FS=34,156/29,507=1.16Partthree地球表層的塑造過程

第三講環(huán)境地質(zhì)學(xué)

EnvironmentalGeologyMassWastingProcessesLandslides