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PART6FOUNDATIONS

TABLEOFCONTENTS

SECTION

6.1GENERAL2

6.2DOCUMENTS,APPROVALANDINSPECTION2

6.3MATERIALSUSEDINFOUNDATIONS4

6.4DESIGNREQUIREMENTS5

6.5EXCAVATIONS8

6.6SHALLOWFOUNDATIONS10

6.7DEEPFOUNDATIONS 10

6.8SPECIALFOUNDATIONS13

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PART6FOUNDATIONS

6.1GENERAL

This part applies to foundation systems for buildings and related structures in the built

environment. It iswritten in terms of general performance requirements. In order to interpret

adequately, such requirements for specific foundation designs in relation to particular site and

subsurface conditions, judgement based on knowledge of geotechnical analysis and design

principlesisrequired.

6.2DOCUMENTS,APPROVALANDINSPECTION

(1)SurfaceandSubsurfaceInvestigation

Unless exempted by the authority having jurisdiction, surface and subsurface

investigationincludinggroundwaterconditions,shallbecarriedoutunderthedirection

ofapersoncompetentinthisfieldofwork,whoshallprepareareportontheresultsof

thisinvestigation,andthisreportshallbesubmittedwiththeapplicationtoexcavateor

build.

(2)DrawingsandEvidence

Drawings submitted with the application to put up a building or to excavate shall

indicate:

(a) the type and condition of the soil or rock, as well as the groundwater

conditions,asdeterminedbythesurfaceandsubsurfaceinvestigation;

(b) the allowable bearing pressures on the soil or rock, the allowable loads,

whenapplicableandthedesignloadsappliedtofoundationunits;

(c) theearthpressuresandother loadsappliedtothesupportingstructuresof

supportedexcavations;

(d) when requiredby theauthorityhaving jurisdiction,evidence that justifies

the information contained on the drawings shall be submitted with the

applicationtoexcavateorbuild.

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(3)Inspection

(a)Inspectionshallbecarriedoutbythedesignerorbyanothersuitablyqualified

personresponsibletothedesigner,toensurethatthesurfaceandsubsurface

conditionsareconsistentwiththedesignandthatconstructioniscarriedoutin

accordancewiththedesignandgoodengineeringpractice.

(b)Inspectionrequiredinclause6.2(3)(a)shallbecarriedout:

(i)onacontinuousbasisduringtheconstructionofalldeepfoundationunits,andduring

theinstallationandrevivalofretainingstructuresandrelatedbackfillingoperation;

and

(ii) as required, unless otherwise directed by the authority having jurisdiction, in the

construction of all shallow foundation units, and in excavating, dewatering and

otherrelatedworks.

(4)ReportsonFoundationInspections

Thepersonresponsible for the inspectionsrequired inclause6.2(3)shallprepareareportof

eachsuch inspectionsignedby thepersonresponsible for the inspectionwhichshallbesent

withoutdelaytotheauthorityhavingjurisdiction.

(5) Alteredsurfaceandsubsurfaceconditions

(a) Whereduringconstructionthesoilorrockisfoundnottobeofthetypeorinthecondition

used in design and as indicated on the drawings, the design shall be reassessed to the

satisfactionoftheauthorityhavingjurisdiction.

(b) Whereduringconstructionclimaticoranyotherconditionshavechangedthepropertiesof

the soilor rock, thedesign shallbe reassessed to the satisfactionof theauthorityhaving

jurisdiction.

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(6) AsconstructedDrawing

Whereconditionsasdescribed inclause6.2(5)areencountered,orwherefoundationunits,or

their locationswere altered, this information shallbe recordedon appropriateddrawingsor

newasconstructeddrawingspreparedandsubmittedtotheauthorityhavingjurisdiction.

(7) Approvaltoproceed

Before any part of a foundation is placed and before any superstructure is placed on a

foundation:

(a) theauthorityhavingjurisdictionshallbenotifiedandgivenanopportunitytoinspectthe

site;and

(b) writtenpermissiontoproceedshallbeobtainedfromtheauthorityhavingjurisdiction.

6.3MATERIALSUSEDINFOUNDATIONS

6.3.1Wood

(1)Preservativetreatmentofwood

Wherewoodisusedinfoundationsorinsupportofsoilorrock,thewoodshallconformtothe

followingstandards:

BS8004:1986Codeofpracticeforfoundations

BS914:Woodpreservationbymeansofpressurecreosoting

BS 4072: Wood preservation by means of waterborne copper/chrome/arsenic (CCA)

compositions.

(2) It is recommended thatwherenecessary, theadviceof theForestryResearch Institute (CSIR

FORIG)andtheBuildingandRoadResearchInstitute(CSIRBRRI)besought.

6.3.2Plainandreinforcedmasonry

(1) Plain reinforcedmasonryused in foundations shallbedesigned to resisteffectivelyall

effectsofloadsandinfluencesthatmaybeexpectedandshallsatisfytherequirements

ofSections5.3to5.9ofPart5oftheCode.

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(2)Whereplainorreinforcedmasonryinfoundationsorinstructuressupportingsoilorrock

maybesubjectedtoconditionsconducivetodeterioration,protectionshallbeprovided

topreventsuchdeterioration.

6.3.3Concrete

(1) Plain, reinforcedorprestressedconcreteused in foundations shallbedesigned to resist

effectivelyalleffectsof loadsand influencesthatmaybeexpectedandshallsatisfythe

requirementsofSections5.3to5.9ofPart5oftheCode.

(2)Chemicalattackonconcrete

Whereconcrete in foundationsmaybesubject tochemicalattack itshallbe treated in

accordancewithrequirementinBS8004:1986Codeofpracticeforfoundations.

6.3.4Steel

(1)Steelusedinfoundationsorinsupportofsoilorrockshallbedesignedtoresisteffectively

all effects of loads and influences that may be expected and shall satisfy the

requirementsofclauses5.3to5.9ofPart5oftheCode.

(2)Corrosionofsteel

Where conditions are corrosive to steel, adequateprotectionof exposed steel shallbe

provided.

6.3.5Othermaterials

Materialsotherthanthosedescribed inthissubsectionmaybeusedinfoundationsprovided

theyconformtotheminimumrequirementsofthissubsectionandareapproved.

6.4DESIGNREQUIREMENTS

(1)Basisofdesignforfoundations

Thedesignoffoundations,excavationsandsoilandrockretainingstructures,shallbebased

onasurfaceandsubsurfaceinvestigationscarriedoutbyapersoncompetentinthisfieldor

work,andoneormoreofthefollowing:

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(a) application of generally accepted geotechnical and civil/structural engineering

principlesbyapersoncompetent inthis fieldofworkasprovided inthissectionand

othersectionsofPart5ofthisCode;

(b) establishedlocalpracticewheresuchpracticeincludessuccessfulexperiencebothwith

soilsand rocksof similar typeand conditionandwitha foundationorexcavationof

similartype,constructionmethod,sizeanddepth.;

(c) insitu testingof foundationunits suchas load testing ofpiles,anchorsor footings

carriedoutbyapersoncompetentinthisfieldofwork;or

(d) innovative approaches, provided the design is carried out to the satisfaction of the

authority having jurisdiction by a person specially qualified in the specific method

applied,andprovided thedesignensuresa levelof safetyandperformanceat least

equivalenttothatprovidedfororimplicitindesigncarriedoutbymethodsreferredto

inclauses(a)and(b).

6.4.2Subsurfaceinvestigation

Asubsurfaceinvestigationshallbecarriedouttosuchadepthandextentastoprovideall

the necessary information for the design and construction of the excavation or the

foundation.

6.4.3Identificationandclassificationofsoilandrock

Theidentificationandclassificationofsoilsandrocksanddescriptionsoftheirengineering

andphysicalproperties shallbe inaccordancewithawidelyaccepted system, suchasBS

8004.

6.4.4Loadsonfoundations

ThefoundationsofabuildingshallbecapableofresistingallloadsasstipulatedinPart5of

thisCode.

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6.4.5Totalanddifferentialsettlement

The foundation of a building shall be proportioned so that the estimated total and

differential settlementsof the foundationarenot greater than the settlements that the

buildingisdesignedtoaccommodate.

6.4.6Depthoffoundation

Thebearingsurfaceofafoundationshallbebelowthe levelofanypotentialdamagedue

toerosionoregressofwaterandaggressiveliquids.

6.4.7Slopingground

Whereafoundation istoreston, inornearslopingground,thisparticularconditionshall

beprovidedforinthedesign.

6.4.8Eccentricandinclinedloads

Wherethereiseccentricityorinclinationofloadinginfoundationunits,thiseffectshallbe

fullyinvestigatedandprovidedforindesign.

6.4.9Dynamicloading

Wheredynamic loading conditionsapply,allowable loadsorallowablebearingpressures

shallbeassessedbyaspecialinvestigationoftheseconditions.

6.4.10Hydrostaticuplift

Whereafoundationoranypartofabuilding issubjecttohydrostaticuplift,theeffects

shallbeprovidedforindesign.

6.4.11Watertablechange

Where proposed constructionwill result in a temporary or permanent change in the

groundwater level, the effects of this change on adjacent property shall be fully

investigatedandprovidedforinthedesign.

6.4.12Swellingandshrinkingsoil

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Whereswellingorshrinkingsoils, inwhichmovementsresultingfrommoisturecontent

changesmaybesufficienttocausedamagetoastructure,areencounteredorknownto

exist,suchaconditionshallbefullyinvestigatedandprovidedforindesign.

6.4.13Expandinganddeterioratingrock

Whererockwhichexpandsordeteriorateswhensubjectedtounfavorableenvironmentalconditions

ortostressrelease isknowntoexist,suchconditionsshallbefully investigatedandprovidedfor in

thedesign.

6.4.14Constructiononfill

Buildingsmaybeplacedonfillifitcanbeshownbysubsurfaceinvestigationthat:

(a) thefillisorcanbemadecapableofsupportingthedesignloads;

(b) detrimentalmovementofthebuildingorservicesleadingtothebuildingwillnotoccur;and

(c) Explosivegassescanbecontrolledordonotexist.

6.4.15Structuraldesignoffoundations

Thestructuraldesignofafoundationofabuilding,theproceduresandconstructionpracticesshall

conformwith theappropriate subsectionsand clausesof thisPartof theCodeunlessotherwise

specifiedinPart5ofthisCode.

6.5EXCAVATIONS

6.5.1Excavationdesign

The design of excavations and of supports for the sides of excavations shall conform with the

requirementsofSection6.4andtothissubsection.

6.5.2(1)Excavationconstruction:

Everyexcavationshallbeundertakeninsuchamannerasto:

(a)preventmovementwhichwouldcausedamagetoadjacentproperty,existingstructures,

utilities,roadsandsidewalksatallstagesofconstruction;and

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(b)protectthepublicatthebuildingsite.

(2)Materialshallnotbeplacednorshallequipmentbeoperatedorplacedonoradjacenttoan

excavationinamannerthatmayendangertheintegrityoftheexcavationsoritssupports.

6.5.3Supportedexcavations

Thesidesofanexcavationinsoilorrockmaybesupportedbyaretainingstructureconformingwith

therequirementsofSubsections6.5.1and6.5.2exceptaspermittedinClause6.5.2(1)and6.5.2(2).

6.5.4Unsupportedexcavations

The sides of an excavation in soil or rockmay be unsupportedwhere a design is prepared by a

personcompetent in this fieldofwork inconformancewith the requirementsofSubsection6.5.1

and6.5.2.

6.5.5Controlofwateraroundexcavations

Surfacewater,allgroundwater,perchedgroundwaterand inparticularartesiangroundwatershall

bekeptundercontrolatallstagesofexcavationandconstruction.

6.5.6Lossofground

At all stages of excavation and construction, loss of ground due towater or any cause shall be

prevented.

6.5.7Protectionandmaintenanceofexcavations

All sides of an excavation, supported and unsupported, shall be continuously maintained and

protectedfrompossibledeteriorationbyconstructionactivityorbyactionofrainandwind.

6.5.8(1)Backfilling

Whenanexcavationisbackfilled,thebackfillshallbeplacedsoasto:

(a)providelateralsupporttothesoiladjacenttotheexcavation;and

(b)preventdetrimentalmovements.

(2)Thematerialusedasbackfillorfillsupportingafooting,foundationorafloorongradeshallbea

typethatisnotsubjecttodetrimentalvolumechangewithchangesinmoisturecontentand

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temperature.

6.6SHALLOWFOUNDATION

6.6.1Designofshallowfoundations

Thedesignofshallowfoundationsshallbeinconformancewithsubsection6.4Designrequirement

andtherequirementsofthissubsection.

6.6.2Foundationsupport

Whereashallowfoundationistobeplacedonsoilorrock,thesoilorrockshallbecleanedofloose

and unsound material and shall be adequate to support the design load taking into account

temperature,precipitation,constructingactivitiesandother factorswhichmay lead tochangesof

thepropertiesofsoilorrock.

6.6.3Incorrectplacementofshallowfoundations

Whereashallowfoundationunithasnotbeenplacedorlocatedasindicatedondrawings,theerror

shallbecorrectedorthedesignbearingpressureofthefoundationunitrecalculatedforthealtered

conditions by the person responsible for the design to the satisfaction of the authority having

jurisdictionandactiontakenasrequiredinClause6.2(6)

6.6.4Damagedshallowfoundationunit

Whereashallowfoundationunitisdamaged,itshallberepairedorthedesignbearingpressureof

thefoundationunitrecalculatedforthedamagedconditionbythepersonresponsibleforthedesign

tothesatisfactionoftheauthorityhavingjurisdictionandactiontakenasinClause6.2(6).

6.7DEEPFOUNDATIONS

6.7.1General

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Adeepfoundationunitshallprovidesupportforabuildingbytransferringloadsbyendbearingtoa

competent stratum at considerable depth below the structure, or by mobilizing resistance by

adhesionorfriction,orboth,inthesoilorrockinwhichitisplaced.Itcanbepremanufacturedor

castinplace, it can be driven, jacked, jetted, screwed, bored or excavated; it can be of wood,

concreteorsteeloracombinationthereof.

6.7.2(1)Designofdeepfoundation

Deepfoundationunitsshallbedesignedinconformancewithsection6.4andthissubsection.

(2)Loadtestingofdeepfoundation

WheredeepfoundationunitsareloadtestedasrequiredinClause6.4(1)(c),anadequatenumberof

loadtestsshallbecarriedoutinaccordancewithBS8004Codeofpracticeforfoundations

orotheracceptablemethods,andtheresultsinterpretedbyapersoncompetentinthisfieldofwork

tothesatisfactionoftheauthorityhavingjurisdiction.

(3)Deepfoundationsnotloadtested

WheredeepfoundationunitsarenotloadtestedasoutlinedinClause6.4(1)(c)andwherewell

establishedlocalpracticeasoutlinedinClause6.4(1)(b)isnotapplicable,thedesignproceduresand

theappropriatestringentfactorsofsafetyshallbedeterminedbyapersoncompetentinthistypeof

worktothesatisfactionoftheauthorityhavingjurisdiction.

6.7.3Allowableloadonadeepfoundation

Theallowableloadonadeepfoundationshallbedeterminedtakingintoaccount:

(a)spacingofthefoundationunitsandgroupeffects;

(b)negativeskinfriction;

(c) lateralloads;

(d)upliftforces;and

(e)otherrequirementsofthisSubsection.

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6.7.4Structuralrequirementsofdeepfoundations

(1)Theportionofdeepfoundationunitpermanentlyincontactwithsoilorrockshallbestructurally

designedasalaterallysupportedcompressionmember.

(2)Theportionofdeepfoundationunitincontactwithairorwatershallbestructurallydesignedas

alaterallyunsupportedcompressionmember.

(3)Structuralstrengthofpremanufactureddeepfoundationunitsshallbesufficienttowithstand

allstressesresultingfromhandlinganddriving.

(ThestructuralstrengthofdeepfoundationunitsasdeterminedinClause6.7.4(3)representsthe

Maximumloadtheunitiscapableofsupportingasastructuralmember,whichinmostcases

exceedsitsgeotechnicalcapacity.

Themaximumloadthatmaybeappliedtoadrivenpile,exceptwhendriventotrueendbearing,is

relatedtotheenergyimpartedtothesoil.Thisenergyisrelatedtotheaxialstiffnessratherthan

thestrengthofthepile.Inadditionwhendeterminingthemaximumloadadeepfoundationunit

cansafelycarryasastructuralmember,considerationshouldbegiventothefactthatitisoften

impracticabletoinspecttheunitforstructuralsoundnessafterithasbeeninstalled.Consequently,

totakeaccountofthislimitation,itmaybedesirabletoassignareducedvaluetoitsstructural

capacity).

6.7.5Tolerancesinlocationandalignment

Permissibledeviationsfromthedesignalignmentandthelocationofthetopofdeepfoundation

unitsshallbedeterminedbydesignanalysisandshallbeindicatedonthedrawings.

6.7.6Incorrectlocationoralignment

Whereadeepfoundationunithasnotbeenplacedwithinthepermissibledeviationsreferredtoin

Subsection6.7.5,theconditionofthefoundationshallbeassessedbythepersonresponsibleforthe

designandanynecessarychangesmadetothesatisfactionoftheauthorityhavingjurisdictionand

actiontakenasrequiredinSubsection6.2.6.

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6.7.7Installationofdeepfoundations

Deepfoundationunitsshallbeinstalledinsuchamannerasnottoimpair:

(a) thestrengthofthedeepfoundationunitsandthepropertiesofthesoilorrockonor inwhich

theyareplacedbeyondthecalculatedoranticipatedlimits;

(b)theintegrityofpreviouslyinstalleddeepfoundationunits;or

(c)theintegrityofneighboringstructuresandservices.

6.7.8Installationrecords

TheinstallationofeachdeepfoundationunitshallbeinspectedinconformancewithSubsections

6.2.3and6.2.4and,insuchamannerthatallpertinentinformationisrecorded.

6.7.9Damageddeepfoundationunit

Whereinspectionshowsthatadeepfoundationunitisdamagedornotconsistentwithdesignor

goodengineeringpractice,theallowableloadofsuchaunitshallbereassessedbytheperson

responsibleforthedesign,anynecessarychangesmadetothesatisfactionoftheauthorityhaving

jurisdictionandactiontakenasrequiredinClause6.2(6).

6.8SPECIALFOUNDATIONS

6.8.1Specialfoundationsystems

Where special foundation systems are used, such system shall conform to Section 6. 4. Design

Requirementsandevidenceshallbeprovided to theauthorityhaving jurisdiction todemonstrate the

adequacyofthefoundationforthepurposeintended.

6.8.2Useofexistingfoundations

Existing foundationsmaybeused to supportneworalteredbuildingsprovided they complywithall

pertinentrequirementsofthisPart6(Foundations)oftheCode.