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《既有建筑地基基礎(chǔ)加固技術(shù)規(guī)范

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precedencetotheirEnglishtranslations

whichareonlyforinternalreference.

IndustrialStandardofthePeople'sRepublicofChina

JGJ123-2000

TechnicalCodeforImprovementof

SoilandFoundationofExistingBuildings

Beijing,2000

IndustrialStandardofthePeople'sRepublicofChina

TechnicalCodeforImprovementof

SoilandFoundationofExistingBuildings

JGJ123-2000

Mainlypreparedby:ResearchInstituteofConstructionScienceof

thePeoplers

RepublicofChina

Approvedby:MinistryofConstructionofthePeople'sRepublicof

China

Implementationdale:June1,2000

—1—

Noticeonissuingtheindustrialstandard“TechnicalCodefor

ImprovementofSoi1andfoundationofExistingBuildings”

JianBiao[2000]No.35

AspertherequirementinMNoticeonIssuingCompilationand

RevisionProjectPlanfor

ConstructionProjectIndustrialStandardsof1993”(JianBiao1993

No.285),“Technical

CodeforImprovementofSoilandFoundationofExistingBuildings”

compiledby

ResearchInstituteofConstructionScienceofPeople'sRepublicof

Chinaishereby

reviewedandapprovedascompulsoryindustrialstandard,numberas

JGJ123-2000,and

shouldcomeintoforcefromJune1,2000.

ThesubjectstandardwillbemanagedandinterpretedbytheResearch

Instituteof

ConstructionScienceofP.R.Chinawhichisthetechnical

responsibleunitfortheMinistry

ofConstruction.TheResearchInstituteofStandardQuotasorganized

ChinaConstruction

PublishingHousetopublishthestandard.

MinistryofConstructionofPeople'sRepublicofChina

February12,2000

—2—

Forward

AspertherequirementofJianBiao1993No.285issuedbythe

MinistryofConstruction,thecodecompilationteamherebycompiledthis

codethroughextensiveinvestigationandresearch,withmanyresearch

resultshomeandabroadandalargeamountofconstructionpractice

experiencessummarized,andthroughopinionsbroadlysolicited.

Thetechnicalcontentsofthiscodemanyconsistofgeneralrules,

symbols,basicstipuation,verificationofsoi1andfoundation,

foundationcalculation,improvementmethodsofsoilandfoundation,

remedyandpreventionofsoilandfoundationincidentoraccident,

improvementthroughaddedlayers,reinforcementtorectifyinclinecr

replacement,andetc.

ThecodeismanagedandinterpretedbytheResearchInstituteof

ConstructionScienceofP.R.Chinawhichisthetechnicalresponsible

unitfortheMinistryofConstruction.

ThecodeismainlycompiledbytheResearchInstituteof

ConstructionScienceofP.R.China(Address:30EastThirdNorthRing

Road,Beijing;Postcode100013)

ThecodeisjointlycompiledbyTongjiUniversity,Nothern

CommunicationUniversity,ResearchInstituteofConstructionScienceof

Fujianprovince.

Thecodeismainlycompiledbyfollowingpersonnel:ZhangYongjun,

YeShuqi,TangYeqing,andHouWeisheng.

—3—

TableofContent

1General

Rules......................................................................

52

Symbols....................................................................

.......................................................................53

Basic

stipulation...............................................................

..............................................................64

VerificationofSoiland

Foundation................................................................

...........................75Foundation

Calculation...............................................................

................................................96Methodsfor

ImprovementofSoiland

Foundation...............................................................

11

7RemedyandPreventionofSoilandFoundation

Incident...................................................27

8ModificationtoAdd

Stories.....................................................................

...................................32

—4—

1.0.1Inordertoexecutethetechnicalandeconomicalpolicyofthe

countryduringthedesignandconstructionoftheimprovementofsoil

andfoundation,thecodeiscompiledso

that“advancedtechnology,reasonableeconomy,safelyandadequacy,

ensuredqualityand

protectedenvironmentncanbeachieved.

1.0.2Thiscodeisapplicabletodesignandconstructionofany

improvement,tosoilandfoundationcausedbyinadequatesoil

investigation,design,construction,oroperations,by

increasedload,incline,displacement,reconstructionorprotection

ofancientbuildings,or

bynearbynewbuildings,excavationofdeepfoundationpits,new

undergroundservices,or

naturaldisaster.

1.0.3Thedesignandconstructionofimprovementofsoiland

foundationofexistingbuildings,besidesmeetingtherequirementscf

thiscode,shouldmeettherequirementof

relevantnationalcompulsorystandardswhichisinforce.

A-Bottomareaoffoundation

d-Pilediameter

d'-Diameterof1imepileafterexpansion

Ep-Compressionmodulusofpilebody

Es-Compressionmodulusofsoi1betweenpiles

Esp-Compressionmodulusofcompoundsoillayer

F-Designvalueoftheverticalforceonthetopsurfaceof

foundationfromupperstructureafterreinforcementoffoundationor

loadincreased.

f-Designvalueoffoundationbearingcapacity

fs,k-Standardvalueofbearingcapacityofsoilbetweenpiles

afterimprovementfp,k-Standardvalueofbearingcapacityofpile

unitsectionfsp,k-Standardvalueofbearingcapacityofcompound

foundationG-Designvalueoffoundationweightandweightofsoilon

topoffoundation11-Linedistanceofpiles

12-Rowdistanceofpiles

M-Designvalueofmomentappliedtothebottomoffoundation

afterimprovementorincreasedload

m-Replacementratioofarea

Na-Designvalueofbearingloadforupliftingpoint

-5-

N-Numberofupliftingpoints

p-Designvalueofaveragepressureonthebottomoffoundation

afterimprovementorincreasedload

pmax-Designvalueofmaximumpressurealongthesideofthe

bottomoffoundationafter

improvementorincreasedload

pmin-Designvalueofminimumpressurealongthesideofthe

bottomoffoundationafter

improvementorincreasedload

Q-Designvalueoftotalloadforbuilding

q-Limevolumeforeachmeteroflimepile

s-Finalsettlementoffoundation

sO-Settlementachievedbeforeimprovementorincreasedload

si-Settlementachievedafterimprovementorincreasedload

s2-Settlementtobeachievedunderoriginalbuildingload

W-Sectionalmodulusatthebottomoffoundationafterimprovement

orincreasedloadnc-Expansionfactor

3.0.1Beforeimprovementofsoi1andfoundationofexisting

buildings,soilandfoundationshouldbeexaminedtoenabledesignand

construction.Theexaminationofsoil

andfoundation,anddesignandconstructionofimprovementshouldbe

carriedoutby

companieswithrelevantcertificationsandbyprofessionalpersonnel

withexperiences.

3.0.2Designofimprovementofsoilandfoundationofexisting

buildingsshouldbecarriedoutaccordingtothefollowingsteps:

1Whenselectingmethodforimprovement,objectiveofimprovement,

jointfunctionof

upperstructure,foundationandsoi1shouldbeconsideredtodecide

initiallywhethersoil,

foundation,stiffnessofupperstructureorcombinationofsoiland

foundationshouldbe

improved.

2Aftertheinitialschemesareselected,theyshouldbecompared

throughexpected

achievement,difficultyofconstruction,materialavailabilityand

deliveryconditions,safe

constructability,impacttoadjacentbuiIdingorenvironment,

conditionsofconstruction

equipment,constructionperiodandcost,sothataoptimumscheme

canbeselected.

3.0.3Theconstructionpeopleshouldunderstandtheobjectiveof

improvement,theory,technicalrequirementandqualitystandardforthe

improvementprojectundertaken.

—6—

Dedicatedpersonnelarerequiredforqualitycontrolthroughstrict

monitoring.Wheneveran

abnormalconditionisobserved,meetingshouldbeheldwith

designersandrelevant

departmenttoanalyzetheproblemandfindsolutions.

3.0.4Adedicatedorganizationisrequiredtosupervisequality

duringconstruction.Whentheconstructioniscomplete,quality

inspectionandacceptanceshouldbeconducted.

3.0.5Settlementobservationisrequiredduringconstructionof

improvedtosoilandfoundation.Forbuildingsofimportanceorof

strictrestrictionofsettlement,settlement

observationshouldbecontinuedaftertheimprovementuntilit

becomesstable.Adjacent

buildingsandundergroundservicesshouldbemonitoredatthesame

time.

4.1VerificationofSoil

4.1.1Thefollowingstepsshouldbeobservedwhenexaminingsoi1of

existingbuildings,

1Collectgeotechnicalinvestigationinformation,designdocuments

anddrawingsof

foundationsforexistingbuildingsandupperstructure,construction

recordedofconcealed

parts,andas-builtdrawings.

2Thefollowingthingsshouldbeanalyzedwhenstudyingtheoriginal

geotechnical

investigationinformation.

1)Distributionandevennessofsubsoil,weakunderlyinglayer,

specialsoil,gullies,

ditches,rivers,tombs,caves,andholes.

2)Physicalandmechanicalpropertiesofsubsoil.

3)Waterlevelandcorrosivityofgroundwater

4)Liquefactioncharacteristicofsiltorsand,andearthquake

characteristicofsoftsoil

5)Stabilityofsite

3Investigatethecurrentconditionofthebuilding,actualworking

load,settlement,and

settlementstability,differentialsettlement,distortion,incline

andcracketc,andfindcauses.

4InvestigateadjacentbuiIdings,undergroundservices,andpipe!ine.

5Workoutinspectionmethodtoverifythesoilbasedonthe

objectiveofimproved,

togetherwithinformationcollectedandanalysesofinformation.

4.1.2Thefollowingmethodscanbeadoptedforinspectionofsoil

accordingtoimprovenentrequirementandsitecondition.

—7—

1Drilling,pitexploration,channelexploration,orearthphysical

methodcanbeadopted.2Indoorphysicalmechanicalpropertytestcanbe

carriedoutonundisturbedsoil.

3Tn-situtestslikeloadtest,conepenetrationtest,standard

penetrationtest,dynamicpenetrationtest,cross-boardsheartestcr

sidepressuretestcanbeadopted.

4.1.3Inspectionofsoilofexistingbuildingsshouldcomplythe

followingrequirements.

1Accordingtotheimportancefothebuildingandoriginal

geotechnicalinvestigation

information,supplementaryboreholeorin-situtestholeshouldbe

providedtofindoutsubsoildistributionandsoilphysicaland

mechanicalproperties.Holesshouldbeclosetofoundation.

2Forimportantbuildingsthatrequireaddingstoriesorincrease

load,itissuitabletotakeundisturbedsoilandcarryoutindoor

physicalmechanicalpropertytestorloadtestunderthefoundation.

4.1.4Whenevaluatingsoilofexistingbuilding,thefollowing

requirementsshouldbemet.

1Accordingtotheinspectionresult,togetherwithlocalexperience,

acompressive

evaluationofthesoilshouldbeprepared.

2Decidewhetheritisnecessarytoimprovesoilandprovide

recommendationsof

improvementmethodbasedonthesoilconditionandupperstructure.

4.2Verificationoffoundation

4.2.1Inspectionoffoundationofexistingbuildingshouldbe

carriedoutaccordingtothefollowingsteps.

1Collectdesignandconstructiondocumentsforfoundation,upper

structure,andpipeline,andas-builtdrawings.Understandtheactual

loadondifferentpartsofthebuilding.

2Siteproofisrequired.Explorationchannelmayberequiredto

verifyfoundationtype,material,dimension,andembeddeddepth.Examine

crackinthefoundation,corrosiveness,degreeofdamage,strengthand

gradeoffoundationnaterials.Ifthebuildinginclines,thendegreeof

inclineanddistortionshouldbeinvestigatedaswel1.Forpiled

foundations,piledepth,bearinglayerandpilequalityshouldalsobe

investigated.

4.2.2Thefollowingmethodscanbeadoptedfortheinspectionof

foundationofexistingbuilding.

—8—

1Visualcheckoffoundation

2Initialcheckwithhandhammertofindoutfoundationquality.

Findoutstrengthor

gradeoffoundationmaterialusingnon-dcstructivcmethodorcore-

takingmethod.

3Checkrebardiameter,numberofpiles,location,andcorrosiveness.

4Observesettlementofpilefoundation.

4.2.3Whenevaluatingfoundationofexistingbuilding,thefollowing

requirementsshouldbemet.

1Evaluatecompletenessofthefoundationbasedoncracks,

corrosiveness,degreeof

damageandgradeofmaterials.

2Calculatebearingcapacityanddeformationbasedontheactual

loadanddeformation

characteristics.Decidewhetheritisnecessarytoimprove,and

recommendmethodof

improvement.

5.1Calculationofbearingcapacity

5.1.1Whenthefoundationofexistingbui1dingneedtobeimproved

ortheloadistobeincreased,thebearingcapacityofsoilshouldbe

calculatedinaccordancewithfollowingrequirements.

Whentheaxialloadworks

p<=f(5.1.1-1)

Where,

p-designvalueofaveragepressureatthebottomoffoundation

afterimprovedorincreasedload.

f-Designvalueofsoilbearingcapacity,whichshouldbe

determinedbasedonthestandardvaluedeterninedthroughthiscodein

accordancewithcurrentnationalstandard“Codeforbuildingfoundation

design”(GBJ7).Forfoundationthatrequiresimprovement,the

standardvalueofsoi1bearingcapacityshouldbedeterminedthrough

examinationaftertheimprovement.Forsoilwithincreasedload,

standardvalueofsoilbearingcapacityshouldbedeterminedthrough

examinationbeforeloadisincreased.Forbuildingswithstabilized

settlement,whenaddingstories,article8.2ofthiscodemaybe

referredtodetermine

standardvalueofsoilbearingcapacity.

Whentheeccentricloadworks,besidesmeetingtherequirementof

formula5.1.1-1,the

followingformulashouldbemetaswell.

pmax<=l.2f(5.1.1-2)

—9-

Where,

pmax-designvalueofmaximumpressurealongthebottomof

foundationafterimprovementorincreasedload.

5.1.2Pressureatthebottomoffoundationafterimprovementor

increasedloadmaybedeterminedthroughthefollowingformula

Whentheaxialloadworks,

p=(F+G)/A(5.1.2-1)

Where,

F-designvalueofverticalforceonthetopoffoundationfrom

upperstructureafterimprovementorincreasedload

G-designvalueoffoundationweightandsoilweightontopof

foundation.Ifbelowwaterlevel,floatingforceshouldbededucted.

A-foundationbottomarea

Whentheeccentricloadworks,

pmax=(F+G)/A+M/W(5.1.2-2)

pmin=(F+G)/A-M/W(5.1.2-3)

Where,

M-designvalueofmomentappliedtothebottomoffoundation

afterimprovementorincreasedload

W-sectionalmodulusoffoundationbottomafterimprovementor

increasedload,pmin-designvalueofmininumpressurealong

foundationbottomafterimprovementorincreasedload.

5.1.3Whenthereisweakunderlyinglayerwithinthebearinglayers

offoundation,thebearingcapacityofweakunderlyinglayershouldbe

calculated.

5.1.4Forexistingbuildingsonaslopeoradjacenttodeep

foundationpit,soi1stabilityshouldbecalculatedaswell.

5.2CalculationofSoilDeformation

5.2.1Thecalculatedvalueofsoildeformationafterimprovementor

inreasedloadshouldnotexceedtheallowablevalueinthecurrent

nationalstandard“CodeforBuilding

FoundationDesign”(GBJ7).

5.2.2Thefinalsettlementoffoundationforexistingbuildingafter

soi1andfoundation

—10—

improvementorincreasedloadshallbedeterminedthroughthe

followingformu1a.

s=s0+sl+s2(5.2.2)

Where,

s-finalsettlementoffoundation

sO-settlementachievedbeforeimprovementorincreasedload,

whichcanbedeterminedthroughsettlementobservationinformationcr

estimatedaccordingtolocalexperience.

si-settlementachievedafterimprovementorincreasedload.If

soilandfoundationareimproved,thevaluecanbecalculatedwiththe

compressionmodulusafterimprovement.If

theloadisincreased,thevaluecanbecalculatedwiththe

compressionmodulusbefore

increased1oad.

s2-settlementtobeachievedunderoriginalbuildingload.The

valuecanbeestimated

basedonthesettlementobservationinformationorlocalexperience.

Ifthefoundation

settlementunderoriginalbuildingloadisstabilized,thenthe

valueshouldbezero.

5.2.3Calculationoffoundationsettlementmaybereferredtothe

currentnationalstandard“CodeforBuildingFoundationDesign”(GBJ

7).

6.1MortarFillingMethod

6.1.1Themethodisapplicablewhencracksarefoundinfoundations

duetounevensettlenent,frostheavingorotherreasons.

6.1.2Whenthemethodisapplies,firstdrillaholeatthecrack.

Thefillingtubecanbe25mmindiameter.Anglebetweentheholeandthe

horizonshouldbenolessthan30

degrees.Thediameteroftheholeshouldbe2-3mmgreaterthanthe

diameterofthefilling

tube.Thedistancebetweenholesmaybe0.5to1.0meter.

6.1.3CementMortarcanbeusedasfillingmaterial.Filling

pressurecanbe0.1to0.3Mpa.Ifthemortarisnotgoinginside,the

pressuremaybeincreasedto0.6Mpaslowly.If

thefillingmaterialisnotgoinginsidefor10to15minutes,

fillingcanbestopped.The

effectivediameteroffillingis0.6to1.2meters.

6.1.4Forsinglefoundations,holesoneachsideofthefoundation

shouldbenolessthantwo.Forstripfoundations,constructionshould

becarriedoutbysections,witheachsection

between1.5to2.0meters.

—11—

6.2FoundationBottomEnlargementMethod

6.2.1Whenthebearingcapacityofthefoundationorthesizeofthe

foundationfortheexistingbuildingcannotmeetingdesignrequirement,

foundationbottomonargemcnt

methodcanbeadopted.Concreteorreinforcedconcretemaybeused

tomakethebottomof

foundationbigger.Thedesignandconstructionshouldmeetthe

followingrequirements

whenmakingthebottomoffoundationbigger.

1.Ifthefoundationisundereccentricload,asymmetrical

enlargementcanbeadopted

whileifthefoundationisundercentralload,symmetrical

enlargement.

2.Thesurfaceoforiginalfoundationshouldbemaderoughand

washedclean,andalayer

ofhigh-strengthcementmortarorconcreteagenttoincreasethe

adhesiveforceofold

concretefoundationandnewconcretefoundations.

3.Fortheenlargedarea,acompactedblindinglayerofthesame

thicknessandmaterielastheoriginalblindingshouldbeused.

4.Whenusingconcretetoimprovethefoundation,thedimensionof

addedconcrete

shouldmeetingtheallowableheightandwidthrationforstiff

foundationstipulatedinthecurrentnationalstandard“Codefor

BuildingFoundationDesign”(GBJ7).Anchorre-bar

shouldbeplacedatcertaindistancealongtheheightofthe

foundation.

5.Whenusingreinforcedconcretetoimprovethefoundation,the

mainre-barsinthe

addedpartshouldbeweldedtothemainre-barsintheoriginal

foundation.

6.Fortheimprovementtostripfoundation,sectionsof1.5to2.0

metersshouldbe

planned,andconstructionshouldbecarriedbybatchesandsections

atdifferenttimes.

6.2.2Whenconcreteorreinforcedconcreteisnotsuitablefor

makingthebottomoffoundationbigger,singlefoundationmaybechanged

intostripfoundation,originalstrip

foundationtocrossstripfoundationorraftfoundation,ororiginal

raftfoundationtoboxfoundation.

6.3FoundationDeepenMethod

6.3.1Themethodisapplicablewhengoodsubsoillayerexistsnear

grade,whichcanbeusedasbearinglayer,andwithlowwatertable.

Maketheoriginalfoundationdeeper,sothatitsitsonabetterbearing

layertomeetthebearinganddeformationrequirementsofthe

design.Whenthewatertableishigh,dewaterordrainingmeasures

shouldbecarriedout.

6.3.2Thefollowingstepsshouldbeobservedwhenmakingfoundation

deeper.

—12—

1.Excavatea1.2meterlong,0.9meterwideverticalpitalongthe

foundationofexistingbuildingsbysectionsorbatches.Ifthepitwall

cannotbeuprightduetosandsoi1orsoftsoil,thensupportsare

requiredforthewalls.Thebottomofthepitmaybe1.5meterslower

thantheexistingfoundation.

2.Excavateafoundationpitundertheoriginalfoundation,the

widthofwhichshouldbethesameastheoriginalfoundation,andthe

excavationdepthshouldreachthebearinglayerrequiredby