《水工建筑物抗震设计标准》（GB51247-2018）

Foreword

AccordingtotherequirementsofDocumentJIANBIAO[2012]No.5issuedbytheMinistryofHousingandUrban-RuralDevelopment(MOHURD)ofthePeople'sRepublicofChina—"NoticeonPrintingandDistributing'theDevelopmentandRevisionPlanofNationalEngineeringConstructionStandardsin2012'",andafterextensiveinvestigationandresearch,summarizationofpracticalexperience,andwidesolicitationofopinions,thedraftinggrouphaspreparedthisstandard.

Thisstandardcomprises14chaptersand2appendixeswiththemaintechnicalcontentsonseismicdesignofhydraulicstructuresofhydropowerplant,covering:generalprovisions;termsandsymbols;basicrequirements;site,foundationandslope;seismicactionandseismiccalculation;embankmentdam;gravitydam;archdam;sluice;undergroundhydrauliestructures;intaketower;penstockandsurfacepowerhouseofhydropowerstation;aqueduct;shiplift,etc.

Theprovisionsprintedinboldtypearemandatoryonesandmustbeimplementedstrictly.

TheMinistryofHousingandUrban-RuralDevelopmentofthePeople'sRepublicofChinaisinchargeofadministrationofthisstandardandexplanationofitsmandatoryprovisions,theMinistryofWaterResourcesofthePeople'sRepublicofChinaisresponsibleforitsroutinemanagement,ChinaInstituteofWaterResourcesandHydropowerResearchisinchargeofexplanationofspecifictechnicalcontents.Duringimplementationofthisstandard,anycommentsandadvicescanbepostedorpassedontoChinaInstituteofWaterResourcesandHydropowerResearch(Address:No.20,ChegongzhuangWestRoad,HaidianDistrict,Beijing,Postcode:100048)

ChiefDevelopmentOrganization,Co-DevelopmentOrganization,ChiefDraftersandChiefReviewersofthisstandard:

ChiefDevelopmentOrganization:

ChinaInstituteofWaterResourcesandHydropowerResearch

Co-DevelopmentOrganization:

ChinaWaterConservancyandHydropowerInvestigationandDesignAssociation

ChiefDrafters:

CHENHouqunLIDeyuHUXiaoGUANZhichengYANGZeyan

LIUXiaoshengWANGHaiboZHAOJianmingSHAOJiannanDUXiaokaiZHANGYanhongZHANGBoyanWANGZhongningTUJinLIMin

ZHANGCuiranOUYANGJinhuiMAHuaifa

ChiefReviewers:

GAOAnzeLIUZhimingZHOUJianpingDANGLincaiZHANGChuhanLINGaoZHOUJianYUYanxiangWANGYayongJIANGGuocheng

LIXiansheSIFu'an

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Contents

1Generalprovisions (1)

2Termsandsymbols (2)

2.1Terms (2)

2.2Symbols (4)

3Basicrequirements (6)

4Site,foundationandslope (8)

4.1Site (8)

4.2Foundation (9)

4.3Slope (10)

5Seismicactionandseismiccalculation (12)

5.1Seismicgroundmotioncomponentsandcombinion (12)

5.2Classificationofseismicactions (12)

5.3Designresponsespectrum (13)

5.4Combinationofseismicactionwithotheractions (14)

5.5Structuralmodelingandcalculationmethod (14)

5.6Dynamicpropertiesofconcreteandfoundationrockforhydraulicstructures (15)

5.7Seismiedesignforutimanlinitstateswitparialfatrs (16)

5.8Seismiccalculationforappartenantstructures (17)

5.9Seismicearnhprcsue (17)

6Embankmentdam (19)

6.1Seismiecalculation (19)

6.2sesmicmeasures (21)

7Gravitydam (23)

7.1Seismiccalculation (23)

7.2Seismicmeasures (25)

8Archdam (27)

8.1Seismiccalculation (27)

8.2Seismicmeasures (29)

9Sluice (30)

9.1Seismiccalculation (30)

9.2Seismicmeasures (31)

10Undergroundhydraulicstructures (33)

10.1Seismiccalculation (33)

10.2Seismicmeasures (34)

11Intaketower (35)

11.1Seismiccalculation (35)

11.2Seismicmeasures (38)

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12Penstockandsurfacepowerhouseofhydropowerstation (40)

12.1Penstock (40)

12.2Surfacepowerhouse (40)

13Aqueduct (42)

13.1Seismiccalculation (42)

13.2Seismicmeasures (42)

14Shiplift (44)

14.1Seismiecalculation (4)

14.2Seismicmeasures (44)

AppendixASeismicstabilitycalculationofembankmentdamsbypseudo-staticmethod (46)

AppendixBCalculationofhydrodynamicpressureinaqueduct (48)

Explanationofwordinginthisstandard (51)

Listofquotedstandards (52)

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1Generalprovisions

1.0.1ThisstandardisformulatedinaccordancewiththeLawofthePeople'sRepublicofChinaonProtectingAgainstandMitigatingEarthquakeDisasters,andwithaviewtocarryingoutthepolicyofpreventionfirst,tomitigateearthquakedamageandpreventsecondarydisastersthroughseismicdesignofhydraulicstructures.

1.0.2Thehydraulicstructuredesignedasperthisstandardshallbeabletoresisttheseismicactionofthedesignintensity,andremainfunctionalafterrepairoflocaldamages,ifany.

1.0.3ThisstandardismainlyapplicabletoseismicdesignofGrade1,Grade2andGrade3hydraulicstructureswithdesignintensityofV,Ⅱ,VandIX,suchastheroller-compactedembankmentdam,concretegravitydam,concretearchdam,sluice,undergroundhydraulicstructures,intaketower,penstockandsurfacepowerhouseofhydropowerstation,aqueduct,shiplift,etc.

ForhydraulicstructureswithdesignintensityofVI,seismiccalculationmaynotberequired,butseismicmeasuresshallstillbetakeninaccordancewiththisstandard.

ForhydraulicstructureswithdesignintensityaboveIX,andwater-retainingstructureshigherthan200morwithunfavorableconditions,specialstudyanddemonstrationshallbecarriedoutontheirseismicsafety.

1.0.4Forgeneralprojects,thedesignpeakgroundacceleration(PGA)ontheprojectsiteandcorrespondingdesignintensityshallbedeterminedinaccordancewiththecurrentnationalstandardGB18306SeismicGroundMotionParametersZonationMapofChina.

1.0.5Forlarge-scale(Rank1)projectswithadamheightover200morreservoirstoragecapacityover10billionm³intheregionswithabasicintensityofVorabove,andlarge-scale(Rank1)projectswithadamheightover150mintheregionswithabasicintensityofVIorabove,thedesignpeakgroundaccelerationontheprojectsiteandcorrespondingdesignintensityshallbedeterminedbasedonsite-specificseismicsafetyevaluation.

1.0.6ForGrade1andGrade2damswithaheightover90m,mainstructuresofRank1pumpedstoragepowerstationsandimportantstructuresofwaterdiversionprojectsintheregionswithabasicintensityofVⅡorabove,thedesignpeakgroundaccelerationontheprojectsiteandcorrespondingdesignintensitymaybedeterminedbasedonsite-specificseismicsafetyevaluationaftertechno-economicdemonstration.

1.0.7Inadditiontothisstandard,theseismicdesignofhydraulicstructuresshallcomplywithotherrcurrentrelevantstandardsofthenation.

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2Termsandsymbols

2.1Terms

2.1.1seismicdesign

Specialdesignofengineeringstructuresinearthquakeregions,generally/includingseismiccalculationandseismicmeasures.

2.1.2basicintensity

Seismicintensityofgeneralsitewitha10%probabilityofexceedancein50years,whichisusuallydeterminedaccordingtothepeakgroundaccelerationspecifiedinthecurrentnationalstandardGB18306SeismicGroundMotionParametersZonationMapofChina,andcorrespondingtotheseismicintensityspecifiedintheAppendix.Formajorprojects,itshallbedeterminedthroughsite-specificseismicsafetyevaluation.

2.1.3designintensity

Seismicintensityforengineeringfortificationdeterminedonthebasisofbasicintensity.

2.1.4reservoirearthquake

Earthquakerelatedtoreservoirimpounding,whicheveroccurswithinascopeoflessthan10kmawayfromthereservoirrims.

2.1.5maximumcredibleearthquake(MCE)

Earthquakewithpotentialmaximumgroundmotionassessedbasedontheregionalgeologicalandseismologicalconditionsaroundprojectsite.

2.1.6scenarioearthquake

Earthquakehavingaparticularmagnitudeandepicentraldistance,withthemaximumprobabilityofexceedanceofdesignpeakgroundaccelerationlinasourcethatmakesthemaximumcontributiontodesignpeakgroundaccelerationonaprojectsiteamongpotentialseismicsources,basedontheresultofsite-specificseismicsafetyevaluation.

2.1.7seismicgroundmotion

Groundmotioninducedbyearthquake.

2.1.8seismicaction

Dynamicactionsofseismicgroundmotiononstructures.

2.1.9hangingwalleffect

Phenomenonthatseismicgroundmotionofhangingwallabovetheinclinedseismogenicfaultislargerthanthatoffootwall.

2.1.10peakgroundacceleration(PGA)

Maximumabsolutevalueofgroundmasspointmotionaccelerationduringearthquake.

2.1.11designearthquake

Seismicgroundmotionforseismicfortificationcorrespondingtodesignintensity,whoseparametersincludepeakgroundacceleration,responsespectrum,duration,andaccelerationtimehistory.

2.1.12designpeakgroundacceleration

Peakgroundaccelerationoffortificationprobabilitylevelspecifiedbysite-specificseismicsafety

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evaluationonprojectsite,orgenerallycorrespondingtothedesignintensity.

2.1.13seismiceffect

Dynamiceffectsuchasstructureinternalforce,deformation,slidingandcrackingcausedbyseismicaction.

2.1.14seismicliquefaction

Processinwhich,inducedbytheseismicgroundmotion,theparticlesofsaturatedcohesionlesssoilorlesscohesivesoilgrowdenser,soilporewaterpressureincreases,andtheeffectivestressofthesoilapproacheszero.

2.1.15designresponsespectrum

Curvethatplotsthemaximumgroundaccelerationasafunctionofthenaturalvibrationperiodofsingle-degree-of-freedom(SDOF)systemconsideringagivendampingratio,whichmaybeexpressedbytheratioofthemaximumaccelerationresponsetothepeakgroundacceleration.

2.1.16dynamicmethod

Methodtoanalyzeseismiceffectofstructurebasedonthetheoryofstructuraldynamics.

2.1.17timehistoryanalysismethod

Methodtoanalyzeseismiceffectinwholetimehistorybyintegratingthegoverningmotionequationofstructurewithaccelerogramasseismicinput.

2.1.18modedecompositionmethod

Methodtoanalyzeseismiceffeetofstructure,inwhichthetotalseismiceffectofthestructureisobtainedbysuperpositionofseismiceffectofeachmode.Itiscalledthemodedecompositiontimehistoryanalysismethod,whenthetimehistoryanalysisisusedtoobtaintheseismiceffectofeachmode.Itiscalledthemodedecompositionresponsespectrummethod,whentheresponsespectrumisusedtoobtaintheseismiceffectofeachmode.

2.1.19squarerootofthesumofsquares(SRSS)method

Methodtoevaluatethemaximumresponseofstructurebythesquarerootofthesumofthesquaresofvariousmodeseismiceffects.

2.1.20completequadraticcombination(CQC)method

Methodtoevaluatethemaximumresponseofstructurebythesquarerootofthesumofquadratictermsofvariousmodeseismiceffectsandcouplingterms.

2.1.21seismichydrodynamicpressure

Dynamicpressureofwateronstructurecausedbyearthquake.

2.1.22seismicearthpressure

Dynamicpressureofsoilmassonstructurecausedbyearthquake.

2.1.23pseudo-staticmethod

Staticanalysismethodtakingtheproductofgravityaction,ratioofdesignseismicpeakaccelerationtogravityacceleration,specifiedseismiceffectreductionfactoranddynamicdistributioncoefficientasthedesignseismicaction.

2.1.24seismiceffectreductionfactor

Reductionfactorforseismiceffectsintroducedduetosimplificationinanalysismethod.

2.1.25naturalvibrationperiod

Timeintervalforstructuretocompleteafreevibrationcycleinacertainvibrationmode.Thenaturalvibrationperiodcorrespondingtothefirstvibrationmodeiscalledthefundamentalperiod.

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2.1.26seismicmeasures

Seismicdesignexceptthecalculationofseismicactionandresistance,includingdetailsofseismicdesign.

2.1.27detailsofseismicdesign

Variousdetailedmeasuresthatmustbetakenforstructuralandnon-structuralmemberswithoutjustificationbyseismiccalculation,accordingtobasicrequirementsofseismicdesign.

2.2Symbols

2.2.1Actionsandeffects:

ah—representativevalueofhorizontaldesignpeakgroundacceleration;

a、—representativevalueofverticaldesignpeakgroundacceleration;

E—representativevalueofhorizontalseismicinertialforceactingonmasspointi;

Fe—representativevalueofseismicactiveearthpressure;

F₀—representativevalueoftotalseismichydrodynamicpressureonwater-contactfaceperunitwidthofstructure;

g—gravityacceleration,whichistakenas9.81m/s²;

Gg—characteristicvalueofstructuretotalgravityactionthatproducesseismicinertialforce;Pw(h)—representativevalueofseismichydrodynamicpressureatwaterdepthh;

a—dynamicdistributioncoefficientofseismicinertialforceofmasspointi;

β—designresponsespectrum;

ξ—seismiceffectreductionfactor.

2.2.2Materialpropertiesandgeometricparameters:

ak—characteristicvalueofgeometricparameter;

f—characteristicvalueofmaterialproperty;

K—characteristicvaluesoflongitudinalstiffnesscoefficientofunitlengthoftunnelsurroundingmass;

K—characteristicvaluesoftransversestiffnesscoefficientofunitlengthoftunnelsurroundingmass;

N—blowcountofstandardpenetrationtest;

N.—criticalblowcount;

v,—characteristicvalueofcompressionwavevelocity;

v₅—characteristicvalueofshearwavevelocity;

Pw—characteristicvalueofwatermassdensity.

2.2.3Limitstatedesignusingpartialfactor:

E—representativevalueofseismicaction;

Gk—characteristicvalueofpermanentaction;

Qk—characteristicvalueofvariableaction;

R—resistanceofstructure;

S—actioneffectofstructure;

γo—importancefactorofstructure;

ya—structuralfactor,safetymarginintroducedfornon-randomuncertaintyontheultimatelimitstateofbearingcapacity;

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YE—partialfactorforseismicaction;

YG—partialfactorforpermanentaction;

Ym—partialfactorformaterialproperty;

YQ—partialfactorforvariableaction;

ψ—designsituationfactor.

2.2.4Others:

T₈—characteristicperiod;

T—naturalvibrationperiodofstructure;

λm—massratioofappurtenantstructuretomainstructure;

λ—fundamentalfrequencyratioofappurtenantstructuretomainstructure.

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3Basicrequirements

3.0.1TheseismicfortificationclassofhydraulicstructuresshallbedeterminedbasedontheirimportanceandbasicseismicintensityontheirsitesaccordingtoTable3.0.1.

Table3.0.1Classificationofseismicfortification

Seismicfortificationclass

Gradeofstructure

Sitebasicintensity

A

Water-retainingandimportantwater-releasingstructuresofGrade1

≥V

B

Non-water-retainingstructureofGrade1andwater-retainingstructureofGrade2

C

Non-water-retainingstructureofGrade2andstructureofGrade3

≥MⅡ

D

StructureofGrade4andGrade5

Note:Importantwater-releasingstructuresrefertothosewhosefailuremightendangerthesafetyofwater-retainingstructures.

3.0.2Theseismicfortificationclassofhydraulicstructuresshallberepresentedintermsofdesignintensityandhorizontaldesignpeakgroundaccelerationonflatgroundsurfaceaftersiteclassadjustment,andshallcomplywithArticle3.0.3toArticle3.0.8inthisstandard.

3.0.3Forhydraulicstructures_whoseseismicfortificationclassesaredeterminedinaccordancewiththecurrentnationalstandardGB18306SeismicGroundMotionParametersZonationMapofChina,inthecaseofgeneralprojects,thevalueofthepeakgroundaccelerationontheirsitesshallbetakenfromzonationmapastherepresentativevalueofthehorizontaldesignpeakgroundacceleration,andthecorrespondingbasicintensityistakenasthedesignintensity.InthecaseofhydraulicstructuresassignedtoseismicfortificationClassA,theirdesignintensityshallbeonelevelhigherthanthebasicintensity,andthe_representativevalueofthehorizontaldesignpeakgroundaccelerationshallbedoubledaccordingly.

3.0.4Forprojectswhoseseismicfortificationcriteriaarebasedonsite-specificseismicsafetyevaluation,theprobabilityofexceedanceoftherepresentativevaluesofhorizontaldesignpeakgroundacceleration,P¹00,ontheflatrockfoundationsurfaceshallbe0.02in100yearsforwater-retainingstructuresandimportantwater-releasingstructuresassignedtoseismicfortificationClassA.Anprobabilityofexceedancein50years,P⁵o,shallbe0.05forGrade1non-water-retainingstructures.Anprobabilityofexceedancein50years,Pso,shallbe0.10forhydraulicstructuresassignedtootherseismicfortificationclassesthanClassA,andthecorrespondingpeakground

accelerationshallnotbelowerthanthatspecifiedinthecurrentnationalstandardGB18306SeismicGroundMotionParametersZonationMapofChina.

3.0.5ForhydraulicstructuresassignedtoseismicfortificationClassAwhosedesignseismicparametersshallbeprovidedbythesite-specificseismicsafetyevaluation,aspecialdemonstrationonsafetymarginunderthemaximumcredibleearthquake(MCE)shallbecarriedoutondisasterpreventionoftheuncontrolledreleaseofreservoirinadditiontotheseismicdesignunderdesignpeakgroundacceleration.Aspecialreportonseismicsafetyshallbeprepared.TheMCEofthesiteshallbedeterminedbythedeterministicmethodortheprobabilisticmethodwithanprobabilityofexceedanceof0.01in100years.

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3.0.6Inthespecialreportonseismicsafety,relevantsite-specificdesignresponsespectrumshouldbedeterminedbasedonscenarioearthquakecorrespondingtohorizontaldesignpeakgroundacceleration,andartificialaccelerogramsaregenerated.Foranalyzingtheseismiceffectonstructureswithstrongnon-linearity,theinfluencearisingfromnon-stationaryfrequencyofgroundmotionshouldbestudiedwhenconditionspermit.Whenthedistancefromtheseismogenicfaulttothesiteislessthan30kmanditsinclinationangleissmallerthan70°,hangingwalleffectshouldbeconsidered.Whenthedistanceislessthan10kmandthemagnitudeisover7.0,theruptureprocessofseismogenicfaultastheareasourceofthenear-fieldstrongearthquakegroundmotionsshouldbestudiedtogeneratedirectlytherandomtimehistoriesofgroundmotions,andthentoselectthetimehistorieswiththepeakperiodofevolutionaryspectrumclosesttothefundamentalperiodofstructure.

3.0.7Whenthegradeofwater-retainingstructureisraisedduetothedamheight,specialstudyontheseismicfortificationstandardshallbeperformedandreportedtocompetentauthoritiesforapproval.

3.0.8Seismicactionsmaynotbeinvolvedinthecaseofrelativelyshortperiodofconstruction.

3.0.9Fornewreservoirswiththedamhigherthan100mandstoragecapacitylargerthan

500millionm³,anevaluationofreservoirearthquakeshallbeconducted.Inthecaseofpotentialreservoirearthquakeofmagnitudehigherthan5.0orepicentralintensityhigherthanVⅡ,areservoirearthquakemonitoringnetworkshallbeestablishedandputintooperationatleastoneyearpriortotheinitialimpoundment.

3.0.10Theseismicdesignforhydraulicstructuresshallincludeseismiccalculationandseismicmeasures,andshallbecompliancewiththefollowingrequirements:

1Selecttheregion,siteandstructuretypefavorableforseismicresistanceaccordingtotheseismicrequirements.

2Preventstabilityfailureoffoundationandslopesadjacenttothestructures.

3Selectsafeandcost-effectivestructuresandmeasuresforearthquakeresistance.

4Proposetheconstructionqualitycontrolmeasuresmeetingtheseismicsafetyrequirementsindesigndocuments.

5Arrangewater-releasingfacilitiesthatcanlowerthereservoirlevelasquicklyaspossible.

6Conductseismicdesignsfornon-structuralelements,appurtenantelectromechanicalequipmentandtheirconnectionswithmainstructuresinhydraulicstructures,suchassluice,intaketowerandshiplift.

3.0.11Therequirementsforemergencyplantopreventandmitigateearthquakehazardshallbeeproposedinthedesigndocumentforhydraulicstructureswithseismicrequirements.

3.0.12DynamicmodeltestshouldbeconductedfordamsassignedtoseismicfortificationClassAwiththedesignintensityofVⅢandabove,andaheightofmorethan150m.

3.0.13Theseismicmonitoringarraydesignforstrong-motionobservationshallmeettherequirementsofthecurrentprofessionalstandardSL486TechnicalSpecificationofStrongMotionMonitoringforSeismicSafetyofHydraulicStructuresorDL/T5416SpecificationofStrongMotionSafetyMonitoringforHydraulicStructures.

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4Site,foundationandslope

4.1Site

4.1.1Insiteselectionforahydraulicstructure,acomprehensiveevaluationshallbeperformedintermsoftectonicactivity,thestabilityofsitefoundationandslope,andtheriskofsecondarydisasters,etc.,basedonengineeringgeologicalandhydrogeologicalexplorationandseismicityinvestigation.Thesiteshallbeclassifiedintofourcategories:favorable,normal,unfavorableandhazardousaccordingtoTable4.1.1.Favorableornormalsiteforseismicsafetyshouldbeselected,whileunfavorableandhazardoussitesshouldbeavoided.Athoroughseismicsafetyeyaluationmustbeconductedforadamconstructedinunfavorableandhazardoussites.

Table4.1.1Classificationofsite

Siteclass

Tectonicactivity

Stabilityofsitefoundationandslope

Riskofsecondarydisaster

Favorable

Noactivefaultwithin25kmaroundthesite,withbasicintensityofVI

Good

Verylow

Normal

Noactivefaultwithin5kmaroundthesite,withbasicintensityofⅡ

Fair

Low

Unfavorable

Thereareactivefaultsoflessthan10kminlengthwithin5kmaroundthesite,andseismogenicstructureswithamagnitudelessthan5.0.Thebasic

intensityisVI

Poor

High

Hazardous

Thereareactivefaultsnotshorterthan10kmwithin5kmaroundthesite,andseismogenicstruetureswithamagnitudegreaterthan5.0.ThebasicintensityisIX

Verypoor

Veryhigh

4.1.2ThesitesoilsafterexcavationandtreatmentforahydraulicstructureshouldbeclassifiedaccordingtotheshearwavevelocityofsoillayersshowninTable4.1.2,andshallbeinaccordancewiththefollowingrequirements:

1Theshearwavevelocityv,ofsitesoil,ortheequivalentshearwavevelocityofeachsoillayerbeneaththefoundationinthecaseofmulti-layeredsitesoil,shallbecalculatedaccordingtothefollowingformula:

(4.1.2)

whered₀—overburdenthickness(m);

d—thicknessoftheithsoillayer(m);

v.—shearwavevelocityoftheithsoillayer(m/s);

n—numberofoverburdensoillayers.

2Thedeterminationofoverburdenthicknessdoshallbeinaccordancewiththefollowingrequirements:

1)Thethicknessshallbedeterminedbythedistancefromthegroundorfoundationsurfacetothe

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topofthesoillayer,whoseshearwavevelocityismorethan500m/sandtheshearwavevelocityoflayersbeneathwhichisnotlessthan500m/s.

2)Thethicknessshallbedeterminedbythedistancefromthegroundorfoundationsurfacetothetopofthelayer,whosedepthismorethan5mandshearwavevelocityismorethan2.5timestheoverlyingsoillayerandtheshearwavevelocityofitselfandunderlyinglayersisnotlessthan400m/s.Thebouldersandlenticleswithashearwavevelocitygreaterthan500m/sshallbedeemedthesameassurroundingsoillayer.

3)Thehardrocklayerintercalatedinsoilshallbeconsideredasrigidbodyanditsthicknessshallbedeductedfromtheoverburdenthickness.

Table4.1.2Classificationofsitesoil

Sitesoilclass

Shearwavevelocityv(m/s)

Descriptionsandproperties

Hardrock

v₅>800

Stiff,hardandintactrocks

Softrockandhardsoil

800≥v,>500

Fracturedandpartiallyfracturedrocks,orsoftandintermediaterocks;densesandygravels

Moderatelyhardsoil

500≥v,>250

Moderate-denseandslight-densesandygravels;densecoarsesandandmediumsand;hardclayorsilt

Moderatelysoftsoil

250≥v.>150

Slight-densegravels,coarsesand,mediumsandandfinesandandsiltysand;ordinaryclayandsilt

Softsoil

v≤150

Muck;muckysoil;loosesandysoil;miscellaneousfill

4.1.3Sitesshallbeclassifiedintofiveclasses,namelyI₀,I₁,I,Ⅲ,andIV,accordingtothetypeofsitesoilandoverburdenthickness,asshowninTable4.1.3.

Table4.1.3Classificationofsite

Sitesoilclass

Overburdenthicknessd。(m)

0

0<d₀≤3

3<d

5≤d₀≤15

15<d₀≤50

50<d₀≤80

do>80

Hardrock

I₀

-

Softrockandhardsoil

I₁

-

Moderatelyhardsoil

-

I₁

Ⅱ

Moderatelysoftsoil

-

I₁

Ⅱ

Ⅲ

Softsoil

-

I₁

Ⅱ

Ⅲ

IV

4.2Foundation

4.2.1Inseismicdesignoffoundationforhydraulicstructures,thetype,load,hydropowerandoperatingconditionsofstructures,aswellasengineeringgeologicalandhydrogeologicalconditionsoffoundationandbankslopeshallbeconsideredcomprehensively.

4.2.2Forfoundationandbankslopeofwater-retainingstructures,suchasdamandsluice,thecriteriaonstabilityagainstearthquakeliquefaction,earthquakesubsidenceofweakclayandseepagedeformationunderdesignseismicactionshallbemet.Thedetrimentaldeformationtothestructuresshallbeavoided.

4.2.3Forweakdiscontinuitiesinfoundationandbankslopeofhydraulicstructures,suchasfaults,fracturedzones,dislocationzones,andespecially,low-dipclay-interbeddedlayersandargillization-liable

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rocklayers,thestabilityandallowabledeformationunderdesignseismicact