Geology Applied to Civil Engineering 土木工程地質(zhì) 英文課件 第4章 Geologic processes of surface water、Geologic processes

4.2GeologicalprocessesofgroundwaterGeologyAppliedtoCivilEngineering12contentsGeologicalprocessesofriverGeologicalprocessesoftemporarysurfacewater1GeologicalprocessesoftemporarysurfacewaterThetemporarysurfaceflowisaseasonalandintermittentflowwithprecipitationasthedominantwatersourceandwoulddryupduringthedryseason,e.g.,thesurfacewaterfromtheslopetothevalleyafterprecipitation.1.1EluviationandeluviumDuringtheinfiltrationprocessofprecipitationtotheunderground,theinfiltratedwaternotonlycarriesawaythefineparticlesbutalsodissolvesthesolublematerials.Undertheaforementionedphysicalandchemicalprocesses,therocksontheearthsurfacegraduallylosetheirintegrityandcompactness,andtheleftovermaterialisusuallyinsolubleandhardtobewashedaway.Thisprocessiscalledeluviation,andtheleftovermaterialiscalledeluvium,whichcanbemarkedasQel

（1）Eluviumisalayeroflossandfracturedmaterialbetweentheweatheredzoneofbedrockandearthsurface.（2）Thematerialcompositionofeluviumiscloselyrelatedtotheunderlyingbedrock（3）Thethicknessofeluviumisrelatedtothelocaltopography,precipitation,chemicalcomponentsinthewater（4）Theeluviumusuallyhasrelativelylargerporosityandhigherwatercontent1.2OutwashanddiluviumBeforemergingintothedepressionsorvalleys,theprecipitationusuallyflowsassheetflowovertheentireslopeandwashestheweatheredfragmentarymaterialstotheslopefoot.Thisprocessisdefinedasoutwash,andthesedimentarydepositsattheslopefootisarecalleddiluvium,markedasQdl（1）Diluviumusuallylocatesattheslopefootwithvariousthicknesses.（2）Diluviumisusuallycomposedofgravelandclay,anditsmaterialcompositionisnotdeterminedbytheunderlyingbedrockbutthebedrockontheupperslope.（3）Thestratificationisnotsignificantinthediluviumandtheedgesandcornersofgravelsareveryclearduetotherelativeshorttransportingdistance.（4）Diluviumischaracterizedbylooseandwater-richfeatures,therefore,hasrelativelypoorperformancewhenservingascivilfoundation1.3ScouringandproluviumHeavystormoralargeamountofmeltingsnowusuallyformssignificanttemporarysurfacewaterflow,whichisalsoknownastorrent.Thetorrentcancarryavastamountofmudandrocksforadistance.Thesemudandrocksusuallydepositatthegullymouthandformproluvium,markedasQpl（1）Proluviumusuallylocatesatthepiedmontplains,intermountainbasinsandtheentrancesofrivers.Proluviumisusuallyintheshapeofafan.Proluvialfan（2）Thecompositionofproluviumisverycomplexanddeterminedbytherocktypeoftheupstreamrunoffarea.（3）Thegrainsizedecreasesfromthehandletothearcedgeandchangesfromsandtosandyclay,clayeysandandclay.（4）Theproluvialcomponentsanddistributionaswellaswaterdistributionshouldbeinvestigatedbeforedeterminingtheplaceforconstruction.Gullyiseasilyformedatthelocationswithrelativelyloosesurfacesoil,highlyfracturedrock,steepslope,andrarelyvegetationcoveredgroundsurface.Theformationprocessofgullies:(a)Theoriginalgroundsurface;(b)Ditchesformedduringtherainwash;(c)Ditchesconnectedandevolvedasinitialgullies;(d)Densegullynetworkformedduringthelong-termtemporarysurfacewaterflowinteraction.Gully2GeologicalprocessesofriverTheperennialsurfaceflowisaperennialwaterwhichmayhaveseasonalfluctuationbutwouldnotdryupalltheyearround.Thiskindofsurfacewaterisusuallyknownasriver.Avalleywithtemporarywatercantransformintoariverifrechargedcontinuously.Generally,alotofwatersourcescanactasthepotentialrechargewaterforrivers.Besidestheprecipitation,riverscanberechargedbythemeltediceorsnowfromthehillaswellasthegroundwater.2.1(1)ErosionprocessesofriverTheerosionprocessbyarivercanbedividedintodown-cuttingandlateralerosion.Thedown-cutting,alsoknownasverticalerosionisthedownwardcuttingoftheriverbedwhichoftenresultsinthedamagetotheriverbottom.Lateralerosionistheerosionontheriversides,whichwillwiden,bentanddestroytheriverchannel.Theerosionbyriverisdeterminedbythefluxandvelocityofriverflow,andcanbeestimatedusingthefollowingequation:whereEisthekineticenergyoftheriver,Qdenotesthefluxoftheriver(m3/s),andVrepresentsthevelocity(m/s).Thedown-cuttingprocesserodesandwidenstheriverchannel.Thedegreeofdown-cuttingdependsonthevelocityandfluxaswellasthecomponentsoftheriverbed.Thelateralerosionerodestheriverbanksandchangesthewidthandcurvatureoftheriverbed.Thereareseveralreasonsoflateralerosiontotheriverbank.Firstly,duetothewindingoftheriverbed,asmallwindingwillchangetheparallelrelationshipbetweenthemainstreamlineandtheriverbank,whichwillincreasethewindingoftheriver.Secondly,theobstaclesintheriver,e.g.,shoal,canchangethemainstreamlineanderodetheriverbankDown-cuttingerosionThelateralerosionandsedimentationofrivererosionDown-cuttingandlateralerosion2.1(2)TransportationprocessesofriverTransportationprocess:Riverhasthecapacitytotransporttheerodedfragmentstothedownstreamlakeoroceanbasinsthroughvariousways.Physicaltransportationcarriesclay,silts,sandsandrocks.physicaltransportationcanbedividedintothreemodes,i.e.floating,jumpingandrolling.Chemicaltransportationmovesthesolublesaltsandcolloidalmatters.Ithasthelongesttransportationdistance,andtheionsandcolloidparticlesareusuallymovedtothebasinsoflakesandtheocean.Sortingprocess:Duringthetransportationprocess,thetransportedmaterialwouldgraduallydepositontheriverbedintheorderfromlargetosmallinsizeandfromheavytolightinmasswithdecreasingofvelocity.Corrosiveprocess:transportedmaterialsareturnedintoroundshapebytheabrasionofangularities,andfinallybecomegravels,pebblesorsandswithsomeroundness.Astheflowvelocitydecreases,thetransportedmaterialsbytheriverwouldgraduallydeposit.Thisprocessisknownassedimentationprocess,andthesedimentiscalledalluvium,markedasQal.Theshapeandcharacteristicsofanalluvialfanaresimilartotheproluvialfan,butthealluvialfanusuallyhasalargerscale,bettersortingandhigherroundness.Thealluviumismoreoftenformedattheestuaryoflargerivers.Thesealluviumsaredominantlyformedbeneaththewatersurfaceandin“fan”shapewiththehandleandedgeofthefanattheestuaryandintheocean,respectively,calleddelta.TheYongdingriveralluvialfanSchematicdiagramofadelta2.1(3)Sedimentationprocessesofriver2.2(1)RivervalleycrosssectionRivervalleyiscomposedbyseveralpartsincludingriverbed,floodplainandterraces.Attheupstreamorearlyphaseofarivervalley,theriverhasstrongdown-cutting,steepslope,highflowvelocityandfewdeposits,resultingina“V”shaperivervalley.Atthedownstreamandlaterphaseofarivervalley,rivershaveonlyslighterosionbutstrongsedimentation.Thesectionusuallysituatesontheplain,andtheriverdistributesonthealluviumwithalluviumplainoutsidetheriverbed.Afewplaceshavestrongsedimentation,andtheriverbedbecomeshigherinelevationduringsedimentation,whichoftenformslevees(naturaldams).2.2(2)RiverterracesRiverterraceisthe“step”shapelandformformedbyerosionorsedimentationintherivervalley.Iftheterraceextendstowardstheperpendiculardirectionofriverflow,theterraceiscalledlateralterrace.Whileiftheterraceextendstowardstheparalleldirectionofriverflow,thentheterraceiscalllongitudinalterrace.Theterracecanbedividedintothethreetypesbasedonthecomposingcomponents:Erosionterraceiscomposedbyafewofalluviumbutmainlyerodedrocks.Basementterracehasrelativelythickalluviumonthesurface,thealluviumiscutthoroughly.Alluvialterracehasthickalluviumthatisnotcutthoroughlybyriver.(a)erosionterrace;(b)basementterrace;(c)alluvialterrace.2.3ThegeologicprocessesofriveranditsimpactonthecivilengineeringCivilengineeringhassignificantrelationwithrivers.Aswecanseeindailylife,thecities,factoriesandhighwaysareusuallyconstructedalongtheriver.Thus,theirlocationsintherivervalleyaresignificantlyimportantforthefoundationstability.Rivers’scouringerosionmaydestroythecivilengineeringontheterrace.Thesedimentationprocessofarivercanalsoposepotentialthreatstothesafetyofhumansettlementsontheplain.Bridgesisaretheessentialwaysfortheroadsandrailwayscrossingtherivers.(1)

thestraightsectionofariverispreferredforthebridgelocation.(2)thelocationswherebedrockswithgoodbearingcapacityandstabilityshouldbeselectedforbuildingthebridgepiersGeologicalenvironmentsurroundingthefoundationoftypicalbridgepiers.ThebridgepierAisnotstableduetothehighpossibilityofoccurringbeddingslip.ThebridgepierCissituatedonafault.課后學(xué)習(xí)及作業(yè)1.將“水流流出谷口時，由于地勢突然趨于平緩、水道變得開闊，水流速度放慢，河流搬運的物質(zhì)逐漸堆積下來，形成洪積扇或沖積扇”譯為英語。2.Whythenaturalriversareusuallynotstraight?Butpresentasmeanders?4.2GeologicalprocessesofgroundwaterGeologyAppliedtoCivilEngineering12contentsHydraulicpropertiesofsoilandrockThestatesofwaterinthesoilandrock3PhysicalpropertiesofGroundwater4ThebasicclassificationofGroundwater5ThegeologicprocessofGroundwater6Theeffectofgroundwateronthecivilengineering1ThestatesofwaterinthesoilandrockPoresandfissuresofrockandsoilprovidethevoidspacesforgroundwaterstorageandtransportation.Groundwatercanbedividedintothefollowingfivetypesaccordingtothephysicalandmechanicalpropertiesofwaterandtherelationshipbetweenwaterandparticles.WatervaporAttachedwater(a,b)Filmwater(c,d)CapillarywaterGravitationalwater(e)Solidwater1.1WatervaporandsolidwaterWatervaporisthesteamexistingintheporesandfissuresofsoilandrockwiththeair.Thiskindofvaporcancomefromtheatmosphereorevaporationforofliquidwaterbeneaththegroundsurface.Watervaporhasstrongactivityandflowsfromthelocationwithhighvaporpressuretothatwithlowvaporpressure.Itsmovementiscontrolledbymanyfactors,suchastheairflow,humidityandtemperature,etcforexample.Thiskindofwaterwouldtransformintoliquidwaterwhenthetemperaturedecreasestoorthehumidityincreasestoacertainvalue.Solidwaterreferstotheiceintheporesandfissuresofthesoilandrock.Theliquidwaterwouldturnintosolidicewhenthetemperatureisbelow0℃,andchangetoliquidsagainwhenthetemperatureincreasestomorethan0℃.Theundergroundtemperatureisbelow0℃allyearroundinnortheasternChina,plateaus,andhighmountainsinwesternChina,asaresult,groundwaterisinthestateofsolidsallthetime.1.2AttachedwaterandfilmwaterAttachedwater,i.e.tightly-boundwater,isthewaterattachedtotheparticlesurfaceofsoils/rocks.Particleholdsthemaximumattachedwaterwhenformingacontinuouswaterfilmaroundit.Atthistimethethicknessofwaterfilmequalstothediameterofthewatermolecule.Filmwater,i.e.loosely-boundedwater,isthewaterattractedbytheparticlesandsurroundstheattachedwater.Thethicknessofthiswatercanreachtoseveralandevenhundredstimesofthewatermolecule.Thiskindofwatercanflowslowlybetweentwoparticleswhencontacting.Thewatermovesfromthethickfilmstothethinfilmsuntilthethicknessofthefilmsapproximatingequally.However,thefilmwatercannotmovefreelybythegravityandpropagatethehydrostaticpressure.Bothattachedwaterandfilmwateraremoleculewater,andtheircontentinthesoilandrockdependsonthesurfaceareaoftheparticles.Asmallerparticlehasmoresurfaceareaandcanboundmorewaterastheattachedwaterandfilmwater.Forexample,thewatercontentofattachedwaterandfilmwatercanreach18%and45%,respectively,inclays,butonly0.5%and2%,respectively,insands.Theattachedwaterandfilmwaterinfissuresandcavitiesofhardrockareverylimitedandcanbeignored.1.3CapillarywaterandGravitationalwaterCapillarywater,i.e.non-boundedwater,isthewaterexistinginthecapillarypores(Φ＜1mm)andfissures(width＜0.25mm)inthesoilandrock.Thecapillarywaterisgovernedbythegravityandcapillaritysimultaneously.Waterwouldgoupwhenthecapillarityisgreaterthangravity,whilegodownwhenthecapillarityislessthangravity.Thecapillarywaterreachesitsmaximumclimbingheightwhenthecapillarityequalsgravity.Theclimbingheightunderthiscircumstanceiscalledcapillaryheight.CoarseSandMediumSandFineSandLightSandClaySandyClayClay2≤h≤412≤h<3535≤h<120120≤h≤250300≤h≤350500≤h≤600Maximumclimbingheightofthecapillarywater(unit:mm).Gravitationalwater,i.e.non-boundedwater,isthewaterwhichcanmovefreelyunderthedrivingofgravity.Thiskindofwaterisoutofthecontrolofparticlegravity,thus,iscalledfreewater.Gravitationalwateristhedominantwaterinsaturatedsoilandrockbesidesattachedwaterandfilmwater.Itisthepredominantpartofgroundwater.1.4GroundwaterdistributionTheundergroundzonecanbedividedintotwocategories,i.e.unsaturatedzoneandsaturatedzone,intermsofthewaterstoringstate.Theboundaryofthesetwozonesisthegroundwatertable,whichistechnicallydefinedasthesurfaceofwhichtheporewaterpressureequalstotheatmosphericpressure.Theunsaturatedzoneholdsvariousstatesofwaterpotentiallyincludingthewatervapor,attachedwater,filmwaterandcapillarywater.Thesaturatedzonehastheattachedwater,filmwaterandgravitationalwater.2HydraulicpropertiesofsoilandrockThehydraulicpropertiesofsoilandrockaredefinedastheperformancesofsoilandrockwheninteractingwithwater.Thehydraulicpropertiescanbedividedintotwocategories.Thefirstcategoryindicatestheperformanceofrocksandsoilsforstoringandtransportingwater,andincludesthewatercapacity,waterretention,permeabilityandwaterrelease.Thesecondcategoryrepresentstheinfluenceofwaterontheengineeringperformanceofrocksandsoils.Thedissolution,absorption,permeability,softening,freezingresistance,disintegration,etc.belongtothiscategory.Watercapacityindicatesthecapabilityofsoils/rocksholdingwater.Itisdefinedastheratioofthevolumeofwaterheldbyrock/soiltothetotalvolumeofrock/soil.Thevalueofwatercapacityequalstothevoidratiowhenthevoidspacesinrocks/soilsaresaturatedbywater.Thevoidratiocanbedividedintoporosityandfractureratebasedonthetypeofvoidspace.However,therearesomeclosedporesandfracturesthatwatercannotenterin,thus,thevalueofwatercapacityinfactislessthantheporosityandfracturerateofsoils/rocks.Waterholdingcapacityofrockandsoilisthecapacityofrocks/soilsholdingwaterinthefracturesorporesbymoleculargravityorcapillaryforce.Thiskindofwatercannotflowfreelyunderthedrivingofgravity,andoccursmainlyintheformofattachedwater,filmwaterandcapillarywater.Waterholdingcapacityisusuallyrepresentedbythewaterretention.Waterretentionisdefinedasthevolumeofwaterheldbymoleculargravityorcapillaryforceinporesandfracturestothetotalvolumeofsoilsorrocks.Theratioofthevolumeofwater(e.g.filmwater),whichisonlyretainedbymolecularforce,tothetotalvolumeofsoilsorrocksiscalledmolecularwaterretention.Theratioofthemaximumvolumeofcapillarywatertothetotalvolumeofsoilsorrocksisdefinedasthecapillarywaterretention.2.1WatercapacityandWaterholdingcapacityofrockandsoilWatersupplyrepresentstheperformanceofsaturatedrocksorsoilsreleasingwaterfreelyunderthedrivingofgravity.Thisperformancecanbesignifiedbythespecificyield,whichistheratiooffreelyreleasingwatervolumetothetotalvolumeofrocks/soils.Thespecificyielddiffersindifferenttypesofsoilandrock.Sedimentslikegravel,coarsesand,etcwithlargeparticlesize,usuallyhavelargevoidspacetoholdgravitationalwater,thus,arewithrelativelylargespecificyield,whileforthelithologies(forexample,clay,mudstoneandshale)withfineparticlesusuallyholdverylimitedgravitationalwaterduetotheirsmallvoidspaces,therefore,haveverysmallspecificyield.2.2WatersupplyLithologyGravelCoarseSandMediumSandFineSandExtraFineSandSpecificyield(d)0.30≤d<0.350.25≤d<0.300.20≤d<0.25~0.15≤d<0.200.10≤d<0.153PhysicalpropertiesofgroundwaterThephysicalpropertiesofgroundwaterincludetemperature,color,transparency,smell,taste,electricalconductivityandradiation,forexample.Thesepropertiesareaffectedbythesurroundingenvironmentandgroundwaterchemicalcomposition.Temperature:Thetemperatureofgroundwaterdependsonitsburialdepth,rechargeconditionandgeologiccondition.Generally,groundwatercanbedividedintosevencategoriesbasedonthetemperature,i.e.overcoldwater(<0℃),extremelycoldwater(04℃),coldwater(420℃),warmwater(2037℃),hotwater(3742℃),extremelyhotwater(42100℃),overhotwater(>100℃).Color:Groundwatercolordependsonthechemicalcomponentsandsuspendedsolids.Waterwithoutchemicalcomponentsandsuspendedsolids,i.e.purewater,iscolorless.Transparency:Purewateristransparent,however,ifthewaterhassomeminerals,organicsorcolloidalmatters,thetransparencewillbechanged.Themorecompoundsthewaterhas,thelesstransparentthewaterwillbe.3.1Physicalpropertiesofgroundwater3.1PhysicalpropertiesofgroundwaterSmell:Purewaterandmostmineralshavenosmell.However,whentherearesomegasesororganicmatters,thewaterwillhavesomesmell.Taste:Thetasteofgroundwaterdependsonthechemicalcomponentsinit.SpecificGravity:Thespecificgravityofgroundwaterdependsonthecomponentsinthewater.Thisparameterequals1forpurewater,whileitcanreach1.2to1.3whenmanycomponentsareincluded.ElectricalConductivity:thesalinityofthegroundwaterdeterminestheelectricalconductivityofgroundwater.Radioactivity:TheradioactivityofgroundwaterreliesontheRadonandradioactivesalts.Infact,mostgroundwaterscontainmoreorlessradioactivity.3.2ChemicalcompositionofgroundwaterThemajorchemicalcomponentsingroundwaterVariouschemicalinteractionsoccurbetweengroundwaterandsurroundingrockscontinuouslyduringthegroundwaterflowandstorageperiods.Theseinteractionscandissolveorexchangesomesubstancesonrocksandresultintheincreaseofgroundwaterchemicalcomponents.About60elementswerefoundinthegroundwateruntilnow.ThecategoriesofgroundwateraccordingtothechemicalcompositionTotaldissolvedsolids(TDS)Hardness:extrasoft,soft,slightlyhard,hard,extrahardPHGroundwaterTypesFreshwaterWeaklybrackishwaterStronglybrackishwaterSalinewaterSaltyWaterTDS(g/L)＜11

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50≥50TypesStrongAcidWeakAcidNeutralWeakAlkalineStrongAlkalinepHvaluepH≤55<pH<7pH=77<pH<9≥93.3GroundwaterqualityevaluationTheevaluationofgroundwaterqualityissignificantlyimportantincivilengineeringconstruction,anddominantfordomestic,industrialandengineeringpurposes.Groundwaterqualityassessmentfordomesticpurposedominantlyconcernsthehealthofwaterconsumers,andcanbeconductedbasedonthedrinkingwaterstandardofChina.No.ParametersStandard1Color<15degree,withnoothercolor2Turbidity1degree3SmellandtasteNoodor4SuspensionNosuspension5pHvalue6.5≤pH≤8.56Totalhardness<450mg/L7Iron<0.3mg/L8Manganese<0.1mg/L9Copper<1.0mg/L10Zinc<1.0mg/L11VolatileHydroxybenzene<0.002mg/L12AnionicDetergent<0.3mg/L13Sulfate<250mg/L14Chloride<250mg/L15TotalDissolvedSolids<1000mg/L4ThebasicclassificationofgroundwaterTobetterutilizeandstudygroundwater,itisnecessarytodividethegroundwaterintodifferenttypes.Categorymethodisclassifyinggroundwaterwithcomprehensiveconsiderationofvariousfactorsaffectinggroundwaterfeatures.Thiskindofcategoryisusuallysyntheticallyconductedbasedongroundwaterburialconditionandaquifersproperties.AquiferProperties/StorageConditionPorewater(Waterintheporesofloosematerial)FissureWater(Waterinthefissuresofrock)KarstWater(WaterinthecavitycausedbyKarst)VadosezonewaterWaterinthesoilabovetheaquitardofthevadosezoneWaterafterbedrockweatheringKarstwaterpenetratedverticallyintothecavityPhreaticwaterWaterinthedilluivum,proluvium,alluvium,lacustrine,glacialtillandoutwashdeposit.Waterinthedesertorcostaldunes.Waterinthefissuresabovethebedrock,unconfinedwaterinthefissuresoffloetzstrataUnconfinedwaterinthesolublewaterofbarerocksConfidedwater(Artesianwater)Waterinthesynclineorartesianwellformedbylosssoil.Waterinthemonoclinicorartesianslope.Fissurewaterinthestructuralbasin,synclineandbedrock.Waterinthestructuralfracturebeltanddeepfissures.Confidedwaterinthestructuralbasin,synclineandsolublebedrock.4.1GroundwaterclassificationbasedontheburialconditionandtheircharacteristicsVadosezonewaterisdefinedasthewaterdistributedinthevadosezone.Itcanbedividedintogravitationalwaterornon-gravitationalwater.Non-gravitationalwater,alsoknownassoilwater,includesattachedwater,filmwaterandcapillarywater,whilegravitationalwateristheperchedwaterabovethelocalaquicludeinthevadosezone.VadosezonewaterPhreaticwaterPhreaticwateristhegroundwaterexistinginthesaturatedzoneabovethefirstaquiclude.Thephreaticwaterhasafreewatertable,whichisknownasthegroundwatertable.Thedistancebetweenthegroundsurfaceandgroundwatertableisdefinedasthegroundwaterdepth(h).Groundwatertableisnotawidelyextendedsurface.Ithasanundulatedsurfacefromregionalperspective,andisdominantlyinfluencedbythegroundsurfacemorphology,aquiferthicknessandstratumpermeability.(a)topographyinfluence;(b)aquiferthicknessinfluence;(c)aquiferpermeabilityinfluence.ConfinedwaterTheconfinedwaterreferstothegravitationalwaterinaquifersbetweentwoaquicludes.Theseaquifersaresaturatedandgroundwaterinthemareunderpressure.Theupperaquicludeisknownastheupperconfiningbed,whiletheloweraquicludeisknownasthelowerconfiningbed.Duetothehighpressureofconfinedwater,groundwaterwillflowintotheboreholesandreachtoa