土木工程毕业设计外文翻译1

DESIGNANDEXECUTIONOFGROUNDINVESTIGATIONFOREARTHWORKSPAULQUIGLEY,FGSIrishGeotechnicalServicesLtdABSTRACTThedesignandexecutionofgroundinvestigationworksforearthworkprojectshasbecomeincreasinglyimportantastheavailabilityofsuitabledisposalareasbecomeslimitedandcostsofimportingengineeringfillincrease.Anoutlineofgroundinvestigationmethodswhichcanaugment‘traditionalinvestigationmethods’particularlyforglacialtill/boulderclaysoilsispresented.Theissueof‘geotechnicalcertification’israisedandrecommendationsoutlinedonitsmeritsforincorporationwithgroundinvestigationsandearthworks.1.INTRODUCTIONTheinvestigationandre-useevaluationofmanyIrishboulderclaysoilspresentsdifficultiesforboththegeotechnicalengineerandtheroaddesignengineer.Theseglacialtillorboulderclaysoilsaremainlyoflowplasticityandhaveparticlesizesrangingfromclaytoboulders.Mostofourboulderclaysoilscontainvaryingproportionsofsand,gravel,cobblesandbouldersinaclayorsiltmatrix.Theamountoffinesgovernstheirbehaviourandthesiltcontentmakesitveryweathersusceptible.Moisturecontentscanbehighlyvariablerangingfromaslowas7%forthehardgreyblackDublinboulderclayupto20-25%forMidland,South-WestandNorth-Westlightgreyboulderclaydeposits.Theabilityofboulderclaysoilstotake-infreewateriswellestablishedandpoorplanningofearthworksoftenamplifiesthis.Thefinesoilconstituentsaregenerallysensitivetosmallincreasesinmoisturecontentwhichoftenleadtolossinstrengthandrenderthesoilsunsuitableforre-useasengineeringfill.Manyofourboulderclaysoils(especiallythosewithintermediatetypesiltsandfinesandmatrix)havebeenrejectedattheselectionstage,butgoodplanningshowsthattheycaninfactfulfilspecificationrequirementsintermsofcompactionandstrength.Theselectionprocessshouldaimtomaximisetheuseoflocallyavailablesoilsandwithcarefulevaluationitispossibletouseorincorporate‘poorormarginalsoils’withinfillareasandembankments.Fillmaterialneedstobeplacedatamoisturecontentsuchthatitisneithertoowettobestableandtrafficableortoodrytobeproperlycompacted.Highmoisturecontent/lowstrengthboulderclaysoilscanbesuitableforuseasfillinlowheightembankments(i.e.2to)butnotsuitablefortraffickingbyearthworkplantwithoutusingageotextileseparatorandgranularfillcappinglayer.Hence,itisvitalthattheearthworkscontractorfullyunderstandsthehandlingpropertiesofthesoils,asformanyprojectsthisiseffectivelygovernedbythetrafficabilityofearthmovingequipment.2.TRADITIONALGROUNDINVESTIGATIONMETHODSForroadprojects,aprincipalaimofthegroundinvestigationistoclassifythesuitabilityofthesoilsinaccordancewithTablefromSeries600oftheNRASpecificationforRoadWorks(SRW),March2000.Themajorityofcurrentgroundinvestigationsforroadworksincludesacombinationofthefollowingtogivetherequiredgeotechnicaldata:TrialpitsCablepercussionboreholesDynamicprobingRotarycoredrillingIn-situtesting(SPT,variableheadpermeabilitytests,geophysicaletc.)LaboratorytestingTheimportanceof‘phasing’thefieldworkoperationscannotbeoverstressed,particularlywhenassessingsoilsuitabilityfromdeepcutareas.Cablepercussionboreholesarenormallysunktoadesireddepthor‘refusal’withdisturbedandundisturbedsamplesrecoveredatintervalsorchangeofstrata.Inmanyinstances,cablepercussionboringisunabletopenetratethroughverystiff,hardboulderclaysoilsduetocobble,boulderobstructions.Sampledisturbanceinboreholesshouldbepreventedandlossoffinesiscommon,invariablythisleadstoinaccurateclassification.Trialpitsareconsideredmoreappropriateforrecoveringappropriatesizesamplesandforobservingtheproportionofclaststomatrixandsizesofcobbles,boulders.Detailedandaccuratefielddescriptionsarethereforevitalforcutareasandtrialpitsprovideanopportunitytoexaminethesoilsonalargerscalethanboreholes.Trialpitsalsoprovideaninsightontrenchstabilityandtoobservewateringressanditseffects.Asuitablyexperiencedgeotechnicalengineerorengineeringgeologistshouldsupervisethetrialpittingworksandrecoveryofsamples.Thecharacteristicsofthesoilsduringtrialpitexcavationshouldbecloselyobservedasthisprovidesinformationonsoilsensitivity,especiallyifwaterfromgranularzonesmigratesintothefinematrixmaterial.Veryoften,theconditionofsoilonthesidesofanexcavationprovidesamoreaccurateassessmentofitsin-situcondition.3.SOILCLASSIFICATIONSoildescriptionandclassificationshouldbeundertakeninaccordancewithBS5930(1999)andtestedinaccordancewithBS1377(1990).Theengineeringdescriptionofasoilisbasedonitsparticlesizegrading,supplementedbyplasticityforfinesoils.Formanyofourglacialtill,boulderclaysoils(i.e.‘mixedsoils’)difficultiesarisewithdescriptionsandassessingengineeringperformancetests.Asoutlinedpreviously,Irishboulderclaysusuallycomprisehighlyvariableproportionsofsands,gravelsandcobblesinasiltorclaymatrix.Lowplasticitysoilswithfinescontentsofaround10to15%oftenpresentthemostdifficulties.BS5930(1999)nowrecognisesthesedifficultiesindescribing‘mixedsoils’–thefinesoilconstituentswhichgoverntheengineeringbehaviournowtakespriorityoverparticlesize.Akeyparameter(whichisoftenunderestimated)inclassifyingandunderstandingthesesoilsispermeability(K).Inspectionoftheparticlesizegradingswillindicatemagnitudeofpermeability.Wherepossible,triaxialcelltestsshouldbecarriedoutoneitherundisturbedsamples(U100’s)orgoodqualitycoresamplestoevaluatethedrainagecharacteristicsofthesoilsaccurately.Lowplasticityboulderclaysoilsofintermediatepermeability(i.e.Koftheorderof10-5to10-7m4.ENGINEERINGPERFORMANCETESTINGOFSOILSLaboratorytestingisverymuchdictatedbytheproposedend-useforthesoils.TheengineeringparameterssetoutinTable6.1pftheNRASRWincludeacombinationofthefollowing:MoisturecontentParticlesizegradingPlasticLimitCBRCompaction(relatingtooptimumMC)RemouldedundrainedshearstrengthAnumberofkeyfactorsshouldbeborneinmindwhenschedulinglaboratorytesting:Compaction/CBR/MCVtestsarecarriedouton<20mmsizematerial.Moisturecontentvaluesshouldrelateto<20mmsizematerialtoprovideavalidcomparison.Porepressuresarenottakenintoaccountduringcompactionandmayvaryconsiderablybetweenlaboratoryandfield.Preparationmethodsforsoiltestingmustbeclearlystipulatedandagreedwiththedesignatedlaboratory.Greatcaremustbetakenwhendeterminingmoisturecontentofboulderclaysoils.Ideally,themoisturecontentshouldberelatedtotheparticlesizeandhaveacorrespondinggradinganalysisfordirectcomparison,althoughthisisnotalwayspractical.Inthemajorityofcases,theMCVwhenusedwithcompactiondataisconsideredtoofferthebestmethodofestablishing(andchecking)thesuitabilitycharacteristicsofaboulderclaysoil.MCVtestingduringtrialpittingisstronglyrecommendedasitprovidesarapidassessmentofthesoilsuitabilitydirectlyafterexcavation.MCVcalibrationcanthenbecarriedoutinthelaboratoryatvariousmoisturecontentincrements.SampledisturbancecanoccurduringtransportationtothelaboratoryandthiscanhaveasignificantimpactontheresultantMCV’s.IGSLhasfoundlargediscrepancieswhenperformingMCV’sinthefieldonlowplasticityboulderclayswiththosecarriedoutlaterinthelaboratory(2to7days).ManyoftheaforementionedlowplasticityboulderclaysoilsexhibittimedependantbehaviourwithsignificantlydifferentMCV’srecordedatalaterdate–increasedvaluescanbeduetothedrainageofthematerialfollowingsampling,transportationandstoragewhiledilatancyandmigrationofwaterfromgranularlensescanleadtodeteriorationandlowervalues.Thistypeofinformationisimportanttoboththedesignerandearthworkscontractorasitprovidesanopportunitytounderstandthepropertiesofthesoilswhentestedasoutlinedabove.Itcanalsoillustratetheadvantagesofpre-draininginsomeinstances.Withmixedsoils,faceexcavationmaybenecessarytoacceleratedrainageworks.CBRtestingofboulderclaysoilsalsoneedscarefulconsideration,mainlywiththepreparationmethodemployed.Designengineersneedtobeawareofthis,asitcanhaveanorderofmagnitudedifferenceinresults.Staticcompactionofboulderclaysoilsisadvisedascompactionwiththe2.5orrammeroftenleadstohighexcessporepressuresbeinggenerated–henceverylowCBRvaluescanresult.Also,curingofcompactedboulderclaysamplesisimportantasthisallowsexcessporewaterpressurestodissipate.5.ENGINEERINGCLASSIFICATIONOFSOILSInaccordancewiththeNRASRW,generalcohesivefilliscategorisedinTable6.1asfollows:2AWetcohesive2BDrycohesive2CStonycohesive2DSiltycohesiveThematerialpropertiesrequiredforacceptabilityaregivenandthedesignengineerthendeterminestheupperandlowerboundlimitsonthebasisofthelaboratoryclassificationandengineeringperformancetests.IrishboulderclaysoilsarepredominantlyClass2C.Clause612oftheSRWsetsoutcompactionmethods.Twoproceduresareavailable:MethodCompactionEnd-ProductCompactionEndproductcompactionisconsideredmorepractical,especiallywhengoodcompactioncontroldatabecomesavailableduringtheearlystagesofanearthworkscontract.AminimumTargetDryDensity(TDD)isconsideredveryusefulforthecontractortoworkwithasameansofcheckingcompactionquality.Oncethematerialhasbeenapprovedandmeetstheacceptabilitylimits,thenin-situdensitycanbemeasured,preferablybynucleargaugeorsandreplacementtestswherethestonecontentislow.Asplacingandcompactionofthefillprogresses,thein-situTDDcanbecheckedandnon-conformingareasquicklyrecognisedandcorrectiveactiontaken.Thisprocessrequiresthedesignengineertoreviewthefielddensitieswiththelaboratorycompactionplotsandevaluateactualwith‘theoreticaldensities’.6.SUPPLEMENTARYGROUNDINVESTIGATIONMETHODSFOREARTHWORKSThemoretraditionalmethodsandprocedureshavebeenoutlinedinSection2.Thefollowingareexamplesofmethodswhicharebelievedtoenhancegroundinvestigationworksforroadprojects:Phasingthegroundinvestigationworks,particularlythelaboratorytestingExcavation&samplingindeeptrialpitsLargediameterhighqualityrotarycoredrillingusingair-mistorpolymergeltechniquesSmall-scalecompactiontrialsonpotentiallysuitablecutmaterialPHASINGPhasinggroundinvestigationworksformanylargeprojectshasbeenadvocatedformanyyears–thisisparticularlytrueforroadprojectswheresignificantamountsofgeotechnicaldatabecomesavailableoverashortperiod.Onthemajorityoflargegroundinvestigationprojectsnoperiodisleftto‘digest’orreviewthepreliminaryfindingsandre-appraisethesuitabilityofthemethods.Withregardtosoillaboratorytesting,largetestingschedulesareoftenpreparedwithnorealconsiderationgiventotheirenduse.Inmanycases,thescheduleispreparedbyajuniorengineerwhiletheseniordesignengineerwhowillprobablydesigntheearthworkswillhavenorealinvolvement.Itishighlightedthattheengineeringperformancetestsareexpensiveandoflongduration(e.g.5pointcompactionwithCBR&MCVateachpointtakesinexcessoftwoweeks).Whenclassificationtests(moisturecontents,particlesizeanalysisandAtterbergLimits)arecompletedthenamoreincisiveevaluationcanbecarriedoutonthedataandtheengineeringperformancetestsscheduled.IfMCV’sareperformedduringtrialpittingthenagoodassessmentofthesoilsuitabilitycanbeimmediatelyobtained.DEEPTRIALPITSTheexcavationofdeeptrialpitsisoftenperceivedascumbersomeanddifficultandthereforenotconsideredappropriatebydesignengineers.Excavationofdeeptrialpitsinboulderclaysoilstodepthsofupto12misfeasibleusingbenchingtechniquesandsumppumpingofgroundwater.Inrecentyears,IGSLhasundertakensuchdeeptrialpitsonseverallargeroadgroundinvestigationprojects.Thedataobtainedfromthesehascertainlyenhancedthegeotechnicaldataandprovidedabetterunderstandingofthebulkpropertiesofthesoils.Itisrecommendedthatthisworkbecarriedoutfollowingcompletionofthecablepercussionboreholesandrotarycoredrillholes.Thegroundwaterregimewithinthecutareawillplayanimportantroleingoverningthefeasibilityofexcavatingdeeptrialpits.Theinstallationofstandpipesandpiezometerswillgreatlyassisttheunderstandingofthegroundwaterconditions,hencethepurposeofundertakingthisworklateoninthegroundinvestigationprogramme.Largerepresentativesamplescanbeobtained(usingtrenchbox)andin-situshearstrengthmeasuredonblocksamples.Thestabilityofthepitsidewallsandgroundwaterconditionscanalsobeestablishedandcomparedwithlevelsinnearbyboreholestandpipesorpiezometers.Overaprominentcutareaofsay500m,threedeeptrialpitscanproveinvaluableandthespoilmaterialalsousedtocarryoutsmall-scalecompactiontrials.Fromavalueengineeringperspective,thecostofexcavatingandreinstatingtheseexcavationscanbeeasilyrecovered.Aprovisionalsumcanbeallocatedinthegroundinvestigationandusedforthiswork.HIGHQUALITYLARGEDIAMETERROTARYCOREDRILLINGThissystementailstheuseoflargediameterrotarycoredrillingtechniquesusingairmistorpolymergelflush.Tripletubecoredrillingiscarriedoutthroughtheoverburdensoilswiththerecoveredmaterialheldinaplasticcoreliner.Corerecoveryinlowplasticityboulderclayhasbeenshowntobeextremelygood(typicallyinexcessof90%).Thehighcorerecoverypermitsdetailedengineeringgeologicalloggingandprovisionofsamplesforlaboratorytesting.Indrumlinareas,suchasthosearoundCavanandMonaghan,IGSLhasfoundtheuseoflargediameterpolymergelrotarycoredrillingtobeverysuccessfulinrecoveringverystiff/hardboulderclaysoilsfordeeproadcutareas(wherecablepercussionboreholesandtrialpitshavefailedtopenetrate).In-situtesting(vanes,SPT’setc)canalsobecarriedoutwithinthedrillholetoestablishstrengthandbearingcapacityofdiscretehorizons.Largediameterrotarydrillingcostsusingtheaforementionedsystemsaretypically50to60%greaterthanconventionalHQcoresize,butagainfromavalueengineeringaspectcanprovemuchmoreworthwhileduetothequalityofgeotechnicalinformationobtained.SMALL-SCALECOMPACTIONTRIALSTheundertakingofsmall-scalecompactiontrialsduringthegroundinvestigationprogrammeisstronglyadvised,particularlywhere‘marginallysuitable’soilsarepresentinprominentcutareas.Inadditiontovalidatingthelaboratorytestdata,theyenablemorerealisticplanningoftheearthworksandcanprovideconsiderablecostsavings.Thecompactiontrialcanprovidethefollowing:Achievablefielddensity,remouldedshearstrengthandCBREstablishingoptimumlayerthicknessandnumberofrollerpassesResponseofsoilduringcompaction(staticvdynamic)Monitortrafficability°reeofrutting.Atypicalsizetestpadwouldbeapproximately20x10minplanareaanduptointhickness.Theselectedareashouldbeclosetothecutareaorborrowpitandhaveadequateroomforstockpilingofmaterial.Earthworkplantwouldnormallyentailatrackedexcavator(CAT320orequivalent),25tdumptruck,D6dozerandeitheratowedorself-propelledroller.In-situdensitymeasurementonthecompactedfillbynucleargaugemethodisrecommendedasthisfacilitatesrapidmeasurementofmoisturecontents,dryandbulkdensities.Italsoenablesalargesuiteofdatatobegeneratedfromthecompactedfillandtoassesstherelationshipbetweendegreeofcompaction,layerthicknessandnumberofrollerpasses.Bothdisturbedandundisturbed(U100)samplesofthecompactedfillcanbetakenforlaboratorytestingandvalidationchecksmadewiththefielddata(particularlymoisturecontents).IGSL’sexperienceisthatwithgoodplanningasmall-scalecompactiontrialtakestwoworkingdaystocomplete.7.SUPERVISIONOFGROUNDINVESTIGATIONPROJECTSCloseinteractionandmutualrespectbetweenthegroundinvestigationcontractorandtheconsultingengineerisconsideredvitaltothesuccessoflargeroadinvestigationprojects.Aseniorgeotechnicalengineerfromeachoftheaforementionedpartiesshouldliasecloselysothatthedirectionandscopeoftheinvestigationcanbechangedtoreflectthestratigraphyandgroundconditionsencountered.Thenatureoflargegroundinvestigationprojectsmeansthattheremustbegoodcommunicationandflexibilityinapproachtoobtainingdata.Bepreparedtocompromiseasmethodsandproceduresspecifiedmaynotbeappropriateandsiteconditionscanquicklychange.Fromasupervisionaspect(bothcontractorandconsultingengineer),theemphasisshouldbeonthequalityofsite-basedgeotechnicalengineers,engineeringgeologistsasopposedtoquantitywhereworkisduplicated.8.GEOTECHNICALCERTIFICATIONTheDepartmentofTransport(UK)preparedadocument(HD22/92)in1992forhighwayschemes.Thissetsouttheproceduresanddocumentationtobeusedduringtheplanningandreportingofgroundinvestigationsandconstructionofearthworks.RoadprojectsinvolvingearthmovingactivitiesorcomplexgeotechnicalfeaturesmustbecertifiedbytheDesignOrganisation(DO)-consultingengineeroragentauthority.TheprofessionalresponsibilityforthegeotechnicalworkrestswiththeDO.Forsuchaproject,theDOmustnominateacharteredengineerwithappropriategeotechnicalengineeringexperience.He/sheisreferredtoastheGeotechnicalLiaisonEngineer(GLE)andisresponsibleforallgeotechnicalmattersincludingpreparationofproceduralstatements,reportsandcertificates.Section1.18ofHD22/92statesthat“oncompletionofthegroundinvestigationworks,theDOshallsubmitareportandcertificatecontainingallthefactualrecordsandtestresultsproducedbythespecialistcontractortogetherwithaninterpretativereportproducedeitherbythespecialistcontractororDO”.TheDOshallthenprepareanEarthworksDesignReport–thisreportistheDesigner’sdetailedreportonhisinterpretationofthesiteinvestigationdataanddesignofearthworks.TheextentandclosenessoftheliaisonbetweentheProjectManagerandtheGLEwillverymuchdependonthenatureoftheschemeandgeotechnicalcomplexitiesdiscoveredastheinvestigationanddesignproceed.Aftertheearthworksarecompleted,ageotechnicalfeedbackreportisrequiredandistobepreparedbytheDO.Thisaddressesthegeotechnicalissuesandproblemsencounteredduringtheconstructionearthworksandcorrectiveactionormeasurestaken.CertificatesarepreparedbytheDOtosignoffonthegeotechnicalmeasurescarriedout(e.g.unstableslopes,karstfeatures,disused/abandonedmineworkings,groundimprovementsystemsemployed,etc).9.CONCLUSIONSCloseco-operationisneededbetweengroundinvestigationcontractorsandconsultingengineerstoensurethatthegeotechnicalinvestigationworkfortheroadsNDPcanbesatisfactorilycarriedout.Manysoilsaretooeasilyrejectedatselection/designstage.Itishopedthattheproposedmethodsoutlinedinthispaperwillassistdesignengineersduringscopingandspecifyingofgroundinvestigationworksforroadprojects.Withmoderninstrumentation,monitoringofearthworksduringconstructionisverystraightforward.Porewaterpressures,lateralandverticalmovementscanbeeasilymeasuredandprovideimportantfeedbackontheperformanceoftheengineeredsoils.Phasingofthegroundinvestigationworks,particularlylaboratorytestingisconsideredvitalsothatthedatacanbeproperlyevaluated.Disposalof‘marginal’soilswillbecomeincreasinglydifficultandmoreexpensiveasthewastelicensingregulationsaretightened.TheadventoflandfilltaxintheUKhasseenthoroughexaminationofallsoilsforuseinearthworks.ThisislikelytoprovideasimilarincentiveandchallengetogeotechnicalandcivilengineersinIrelandinthecomingyears.AcertificationapproachcomparablewiththatoutlinedshouldbeconsideredbytheNRAforgroundinvestigationandearthworkactivities.土方工程的地基勘察与施工保罗·圭格利爱尔兰岩土工程服务有限公司摘要：当工程场地的处理面积有限且填方工程费用大量增加时，土方工程的地基勘察设计与施工已逐渐地变得重要。由于冰渍土以及含砾粘土的提出使土方工程地基勘察方法的纲要比传统的勘察方法更详细。本文提出“岩土认证”观点以及对地基勘察与土方工程相结合的优点加以概要说明。1、引言许多爱尔兰含砾粘土的勘察与再利用评价使岩土工程师与道路工程师感到为难。这些冰渍土或含砾粘土主要表现为低可塑性而且还含有从粘土到漂石的不同粒径颗粒。大部分本地粘土与淤泥质土中包含不同比例的砂、砾石、卵石、漂石。颗粒级配控制着土体的行为，而且淤泥使土体性质易受天气变化影响。土体含水量随着地区不同而不同，从都柏林硬灰黑含砾粘土的7%到中部、西南部或西北部浅灰色含砾粘土沉积物的20%-25%。含砾粘土吸附水的能力建立的较好但土方工程中计划的不恰当常导致其扩大。一般来说，良好级配的土体对于含水量的轻微变大相当敏感，将导致强度下降或不适合用作工程回填土。许多含砾粘土（尤其中等淤泥质土或良好级配的砂）在选择阶段已经被筛除，但事实上它们能对压缩或强度起到特定的作用。筛选过程应尽量使用本地土体或者回填区或路堤边性质相对较差的土体，通过仔细评价应加以应用。回填材料必须保持一定的含水量，既不能太湿导致土体不稳定也不能太干以致不能被充分压缩。高含水量、低强度含砾粘土适用于低路堤回填（相当于2到的高度）但不适用于没有使用土工织布隔离与回填层的土方回填工程。因此，土方工程承包商充分认识土体的处理特性相当重要，因为许多工程都受到挖掘设备通行能力的影响。2、传统地基勘察方法对于道路工程来讲，地基勘察最基本目标是对土体适用性进行类似表6.1的分类，该表源于国家档案登记处2000年3月版的道路施工规范。目前大部分道路施工中的地基勘察包含以下提供有关岩土参数的试验方法：◆取样孔◆静压法取样◆动力探测◆回转钻进◆原位测试（标准贯入试验，变水头渗透试验，岩土物理试验等）室内试验评价场地工作的重要性特别是评价土体深部取样区域的适用性时不能过分强调其适用性。静压法取样通常将取样器下沉至要求深度进行取样，并每间隔一米进行取样。在许多情况下，静压法取样由于卵石、漂石阻碍不能压入非常坚硬的含砾粘土。土样在钻孔内应尽量少扰动，但级配变坏是很正常的，级配变坏将导致土样分类不够精确。取样孔对于恢复适当尺寸的土样以及观察碎屑岩在卵石、漂石中所占比例来说应该是适当的。因此，详尽且精确的地区描述取样区域以及取样空来说都相当重要，而且还为它们提供了检查土体在钻孔范围以外性质的良机。取样孔也提供了孔壁稳定性的评价以及观察孔壁内水进入时所造成的影响。一位有经验的岩土工程师或工程地质专家应监督取样孔工作以及土样的恢复。因为土样性质为土样敏感性提供了信息，所以取样时土体性质应被密切关注，尤其是水从小颗粒区域迁移到良好级配区域。而且土体在开挖时的条件为其原位条件提供了一个相对精确的评价。3、土的分类土的描述与分类应该依照英国标准5930（1999）进行并依照英国标准1337（1990）进行测试。土的工程描述应基于按粒径大小分级并依照良好级配土的可塑性进行补充。对于许多冰渍土或含砾粘土（混合土）的难点在于其描述与工程性质测试的评价。关于以前的地基勘察纲要，爱尔兰含砾粘土的粘土与淤泥质土中常由易变比例的砂、砾石、卵石组成。良好级配且含水量为10%-15%的低可塑性土最难进行描述与分类。现在英国标准5930（1999）已认识到描述“混合土”所存在的难点——土的良好级配较之颗粒尺寸对于控制着土的工程性质更优越。一个关键参数在土分类以及理解过程中经常被低估，该参数就是渗透系数K。检查土的颗粒级配将间接说明土的渗透系数的大小。假如可能，为了准确评价土体的排水特性，三轴单元试验将采用无扰动原状土样或高质量土样进行试验。低可塑性的中等渗透性含砾粘土(K大约在10-5到10-7米.秒范围内)能经常通过不同排水条件进行“模拟”4、土工试验由于室内试验的许多规定使其被建议用作土的最后试验。土的工程参数列于表6.1，该表源于国家档案登记处2000年3月版的道路施工规范。其中包含以下内容：◆含水量◆颗粒级配◆塑限◆加州承载比◆密实度（最优含水量）◆重塑土不排水抗剪强度当进行室内试验时，大量的关键因素应该被考虑。◆密实度.20mm。◆含水量测试试样应小于20mm以提供真实有效的对比。压缩时孔隙压力未加以考虑可能导致室内与实际存在相当大的差异。土样测试的准备方法必须被明确规定，而且试验应在指定试验室进行。进行含砾粘土的含水量测试时必须非常小心谨慎。理想地说，土的含水量应与其粒径有关，而且还有相应的级配分析曲线，虽然该曲线不是具有实际应用价值。在大部分情况下，含水量被应用于密实度被认为是提供了关于建立含砾粘土适用性特征的最好方法。由于含水量能在开挖后快速评价土体的适用性，故强烈建议在取样孔中对其进行测试。因此，含水量刻度能够在实验室内不同含水量增量情况下被采用。土样扰动常发生在搬运过程中，这将对含水量的结果产生重大的影响。地质科学研究所在进行低可塑性含砾粘土含水量测定时已经土样含水量由于时间的推移（2到7天）存在巨大的差异。许多上述低可塑性含砾粘土表现出与时间相关的含水量变化特性。其变化值主要由于土样取样时的排水条件，土样运移以及其体积的膨胀与土中水的迁移将导致土样破坏或者强度下降。以上资料对于设计者以及土方工程承包商来说都很重要，因为进行上述规定的测试时它提供了设计者以及土方工程承包商理解土体特性的机会。它能说明在某些情况下先进行排水的所存在的优点。对于混合土来说，对土方工程进行开挖时加快排水工程非常有必要。含砾粘土的加州承载比测试也需要非常小心谨慎，尤其是开展测试前所采用的准备工作。设计工程师必须意识到这一点，因为准备工作的误差将导致试验结果的明显不同。经验表明，采用2.5或4公斤的锤进行含砾粘土的静态击实将导致超高的孔隙压力，因此将导致加州承载比值变低。被击实含砾粘土的硬化相当重要，因为土的硬化将使孔隙水压力消散。5、土的工程分类依照英国标准道路施工规范，一般的粘性填土分类如表6.1如下所示：2A湿粘性填土2B干粘性填土◆2C含石粘性填土2D粉质粘性填土首先按可接受性进行提供土样特性，然后设计工程师在实验室分类以及工程性质测试基础进行决定土工程分类的上下限。爱尔兰含砾粘土基本上都属于2C含石粘性填土。道路施工规范612条列出了击实方法。两种现有的规程：◆原状土样击实重塑土样击实重塑土样击实被认为最实用，特别是在土方工程合同初期阶段良好的击实控制数据可被利用。检验击实质量时，最小干密度对于合同承包商来说是最有用的。一旦土样被认可或满足工程分类要求，然后原位密度才能进行测定，当土样中含石量较低时，通常采用核子测定仪或换砂试验进行测定。当布置或击实回填土时，原位干密度能够得到检验，不够密实的地方能够被快速识别并进行击实。该过程要求设计工程师评价击实试验区域的总体密度并估计现场真实的“理论密度”。6、土工地基勘察方法的补充传统的勘察方法与规程已在第二部分进行详细介绍。接下来讲述的是有助于道路工程的地基勘察工作方法的几个例子：◆地基勘察工作分阶段进行，特别是室内测试开挖&深取样孔取样使用喷气或聚合物胶质体技术的大直径高质量回转钻进◆对可能适合挖方的土样进行小范围击实试验对于许多大型工程来说，地基勘察工作应分阶段进行已经被提倡许多年了；特别室道路工程更应如此。因为道路工程的大量岩土工程方面数据可在短期内即可使