Ec7 Embedded Wall Design Nigg

Eurocode 7 SeminarBelfast, 11 April 2013

DavidPreeceBachy SoletancheBachySoletanche

EmbeddedwalldesigntoEC7

Tel: 01704895686Mob: 07715484208E: [email protected]

1


Introduction

Setthescene StepsinvolvedtodesignanembeddedwalltoEC7&highlight

differences and similarities with other advice (C580, BS 8002)differencesandsimilaritieswithotheradvice(C580,BS8002)

ProvideanexampleofacantileverwallandcompareresultsofC580designandEC7design

Execution codes Executioncodes

2


3

Nicoll Highway collapse in Singapore, April 2004. 4 workers killed


4


BelfastSewers2007

5


Fermoy

6


TheCubeBirmingham

7


D t i ll ti t

Embeddedwalldesignsteps Determinewallsectiongeometry Plotgroundconditionsandreviewadequacyofgroundinvestigation Determinecharacteristicvaluesofgeotechnicalparameters

D t i d t diti th ti Determinegroundwaterconditions,otheractions Determinewalltypeandinitialwallsizing SetupcalculationsforULS

C S bi i 2 CarryoutULScombination2 CarryoutULScombination1

SetupcalculationsforSLSandruncalcD t i d i f t b d f th t t l il d i Determinedesignforcestobeusedforthestructuralpiledesign

8


Determinewallsectiongeometrygeometry Retainedlevels horizontal/sloping? Adjacentbuildings,existingbasements Excavation levelsExcavationlevels Permanentbasementlevels Temporaryproplevels,proptypes,temporarybermsdimensions Allowanceforunplannedoverdig

9


9.3.2.2Groundsurfaces hgeometrycontd

(1)Ptakeaccountofthevariationintheactualfieldvalues;

(2)inULSleveloftheresistingsoilshouldbeloweredbelow the normally expected level by an amount

a

belowthenormallyexpectedlevelbyanamounta. a subjecttositecontrol; Withanormaldegreeofcontrol:

Cantilever: a =10%ofwallheightaboveexcavationlevelCa t e e : a 0% o a e g t abo e e ca at o e ewithalimitof0.5m;

Propped: a =10%ofdistancebetweenlowestsupportandexcavationlevelwithalimitof0.5m

(3) = 0 may be used when surface level specified to beh

a(3) a 0maybeusedwhensurfacelevelspecifiedtobecontrolledreliably.

(4)Largervaluesof a shouldbeusedwheresurfacelevelisparticularlyuncertain.

10


Plotgroundinvestigation&reviewadequacy EN 1997 2 2007 (E) Anne B EN19972:2007(E)AnnexB B.3(1):

Forhighrise&industrialstructuresagridpatternat15mto40mg g p Forlinearstructuresaspacingof20mto200m Forspecialstructures(e.g.bridges)twotosixinvestigationpoints

11


B.3(12)forcutoffwallsza > 2.0mbelowgroundinvestigationcontd

asurfaceimpermeabletowater

B.3(13)forpilesza > 1.0bg &> 5.0m&> 3DF Other requirements B 3 (5) for high rise (6) OtherrequirementsB.3(5)forhighrise,(6)

forraftfoundations,(10)forexcavations,etc...

12


Determinecharacteristicvaluesofgeotechnicalparametersp

1.5pagesoftext2.4.5.2(2)Pacautiousestimateofthevalueaffectingtheoccurrenceofthelimitstate.gComparewithdefinitioninCIRIAC580Moderatelyconservative isacautiousestimateofthevaluerelevanttotheoccurrenceofthelimitstateC580onModcon:equivalenttorepresentativevalues inBS8002(1994)&characteristicvalues

d f d h h ld b f dasdefinedinEC7.Thisshouldnotbeconfusedwiththecharacteristicvalue(5percentfractile)adoptedinstructuralengineeringformaterialproperties Fig 5 15 CIRIA C580

13

properties. Fig 5.15 CIRIA C580


characteristicgeotechnicalparameters contd Graph of Level .vs. All Shear Strength Data in Clay Soils

2.4.5.2(3)PThegreatervarianceofccomparedtothatoftanshallbeconsidered

parameterscontd5

Triaxials tests

SPT 'N' x f1

U100 blow s x F

Design line

Design line

considered 2.4.5.2(11)Ifstatisticalmethodsareused,thecharacteristicvalueshouldbederivedsuch that the calculated probability of a

-5

0

L

e

v

e

l

(

m

O

D

/

m

A

O

D

/

m

R

L

)

suchthatthecalculatedprobabilityofaworsevaluegoverningtheoccurrenceofthelimitstateunderconsiderationisnotgreaterthan5%.

-15

-10

NOTEInthisrespect,

characteristic values = moderately conservative = representative values

-200 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300

Undrained Shear Strength, Cu (KPa)

14

characteristicvalues moderatelyconservative representativevalues


9.5.1General (4) mobilised wall friction and adhesion should be considered as a

Wallfrictiond (4)mobilisedwallfrictionandadhesionshouldbeconsideredasa

functionof: thestrengthparametersoftheground; thefrictionpropertiesofthewallgroundinterface;

d

d thedirection&amountofmovementofthewallrelativetotheground; theabilityofthewalltosupportanyverticalforcesresultingfromwall

frictionandadhesion. (5) The amount of shear stress which can be mobilised at the wall ground (5)Theamountofshearstress,whichcanbemobilisedatthewallground

interfaceshouldbedeterminedbythewallgroundinterfaceparameter. (6)Aconcretewallorsteelsheetpilewallsupportingsandorgravelmaybe

assumedtohaveadesignwallgroundinterfaceparameterd =k. cv;d; kshouldnotexceed2/3forprecastconcreteorsteelsheetpiling.

(7)Forconcretecastagainstsoil,avalueofk=1.0maybeassumed.

15


k Wallfriction

Acting UP on

Soil movement

Downward movement of soil relative to wall:

v Kp & Kad =k.cv;d densesand

Acting DOWN on the Upward movement of

UP on the soil

v p a

Loose sand

on the soil

Soil movement

Upward movement of soil relative to wall:

v Kp & Ka

x

Loosesand

+ up

cv;kProp

Common situation wall friction beneficial on both sides:

+up

down

l hSoil movement

Wall movement

Soil movement

Forces on the soil

16CIRIA C580

volumechangecurve Forces on the soil


9.3.2.3WaterlevelsGroundwateranddrainage

Most unfavourable during (1)Pbasedonhydraulicandhydrogeologicalconditionsatthesite

(3)Pconsideradversewaterpressureduetoperched or artesian water tables

Most unfavourable during lifetime of structure

perchedorartesianwatertables

2.4.6.1 (6)forULS:mostunfavourableduringlifetime

fofstructure

(6)forSLS:mostunfavourableinnormalcircumstances

(8)designvaluesderivedbyapplyingpartialfactorstocharacteristicwaterpressuresorapplyingsafetymargintothecharacteristic

t l l

Most unfavourable in normal circumstances

17

waterlevel


2.4.6.1Designvaluesforgroundwatergroundwater

(9)shouldconsider: thefavourableorunfavourableeffectsofdrainage,bothnaturalandartificial,takingaccountofitsfuturemaintenance;

the supply of water by rain flood burst water mains or other means; thesupplyofwaterbyrain,flood,burstwatermains orothermeans; changesofwaterpressuresduetothegrowthorremovalofvegetation

(10)Considerunfavourablewaterlevelsthatmybecausedbythechangesinthewatercatchmentandreduceddrainageduetoblockage,freezingorothercauses.

(11)Unlesstheadequacyofthedrainagesystemcanbedemonstratedanditsmaintenanceensured,thedesigngroundwatertableshouldbetaken as the maximum possible level, which may be the ground surface.takenasthemaximumpossiblelevel,whichmaybethegroundsurface.

9.6(3)unlessareliabledrainagesystemisinstalledvaluesofwaterpressuresshouldnormallycorrespondtoawatertableatthesurfaceoftheretainedmaterial.

18


9.4.2DrainagesystemsContiguous wall

groundwater

(1)PIfthesafetyandserviceabilityofthedesignedstructuredependsonthesuccessfulperformanceofadrainagesystem:

specifymaintenanceprogrammeandorspecifyadrainagesystemthatwilloperatewithoutmaintenance.

Permeablewalls,e,g,contiguouswallsreducebackofwallwaterpressureswhilstpermeabilityp p yismaintainedbutconsiderationofbuildupbehindneedsseriousthoughtasconsequencessevere.

19


groundwater Suggestionofhowtoproceed:SLS ULS

ULS

SLS

1. Apply safety margin to the characteristic water level to determine ULS design value water level. This would normally be close to the ground surface;2. Ensure 1.35 x SLS

For ULS Combination 1 use SLS Design value (since will be

groundwater pressures ~ ULS groundwater pressures, then:

g (factoring up by 1.35 see later)

For ULS Combination 2 use ULS Design value water level without f th f t i

20

any further factoring


But be aware of Section 8.2 of Concrete Basements published by MPA The Concrete Centre

itisrecommendedthatforULSverificationF =G,unfav=1.35shouldbeappliedtonormalgroundwaterlevelsandF =Q=1.20F Qshouldbeappliedtopressurefromwateratthemost unfavourable levelmostunfavourablelevelthatcouldoccurduringthelifetimeofthestructure

21


Actions basic list in 2 4 4 (4)

Otheractionsactingonwall

Actions,basiclistin2.4.4(4) 9.3.1.3Surcharges

(1)Ptakeaccountofthepresence,onornearthesurfaceof( ) p ,theretainedground,of,forexample,nearbybuildings,parkedormovingvehiclesorcranes,storedmaterial,goodsandcontainers.

Nominimumdesignsurchargespecified. Weadopttheminimum10kPasurchargeasrecommendedinBS8002andC580.Mightreducethisforwallswith


Determinewalltype&initialsizingC ti B d Pil W ll ContiguousBoredPileWalls

500to2100mmdiameter Largediameter/CFAboredpilesystems Subjecttogroundconditions

Secant Pile WallsSecantPileWalls 600mmto1050mmtypically Largediameter/CFAboredpilesystems

DiaphragmWalls 500to1500mmwallthickness

23

Grab,hydraulicGrab,MiniCutter,Cutter


24


Determinewalltype&initialsizing Reinforcedconcreteembeddedwallstiffness(EI):

EC2(BSEN199211:2004,clause3.1.3and3.1.4)providesamechanismfordeterminingconcretestiffnessintheshorttermandlongterm.Thestiffnesscalculationstakeaccountofconcretestrength,cementtype,aggregatetype,creepduration(time),environmentalconditions.

f f Theprocessrequiresanumberofassumptionstobemade,followedbythecomputationofanumberofequationsandlookupofcreepfactorfromgraphs.

h h h l d h d Havinggonethroughthiscycle,recommendtheadvicegiveninC580(section4.2.3)issuitable,i.e.:

25


D 4For contiguous and secants:walltype&initialsizing

mms

DI /.64

. 4=For diaphragm walls:

C580(section4.2.3)issuitable,i.e.:

Adopt0.7E0.Iduringconstruction

mmdI /12

43

=

p gp 0 g

Adopt0.5E0.Iduringlongterm

D is structural pile diameter

s is pile spacing

E0 isuncrackedYsM(typically28GPa)Iis2ndmmtofarea

d is wall thickness

I is second moment of area

E0 ~19.6GPaduringconstructionand14GPainlongterm

26


Setupcalculationsforultimatelimitstate(ULS)

UKNationalAnnex DesignApproach1

Two separate checks required:Twoseparatechecksrequired:

Combination1A1+M1+R1

Combination2A2+M2+R1

A denotespartialfactorsonactionsp M denotespartialfactorsonmaterials/strengthparameters R denotespartialfactorsforresistances

27


LoadCombinationsPartialFactorsBS EN 1997-1: 2004. National Annex A BS EN 1997-1: Design Approach 1

Combination 1 Combination 2

A1 M1 R1 A2 M2 R1

Unfv 1.35 1

Fav. 1 1

Action Values (A) Permanent, G

Combination 1 Combination 2

Unfv 1.5 1.3

Fav. 0 0

1 1.25

Variable, Q

Material P ti (M)

Friction angle, Tan1 1.25

1 1.4

1 1.4

Properties (M) Eff. Cohesion, c

Undr. Strengh, cuUnc.Compr.Strength

1 1

1 1

1 1

1 1

Resistances (R) Bearing resistance, Rv

E th i t

Sliding resistance, Rh

Weight density,

28

1 1Earth resistances, Re


CarryoutULScombination2(usuallygovernstoedepth)Action Symbol SetA2

factors A:Increaseunfavourable

variableactionsby1.3factor

M: Apply partial factors to

factors

PermanentUnfavourable G

1.0

favourable 1.0M:Applypartialfactorstomaterialparameters

Factoronsoilstiffness?Recommend use 1 4

VariableUnfavourable Q 1.3favourable 0

Recommenduse1.4.Soilparameter Symbol SetM2

factors

Angle of shearing resistance tan 1 25Angleofshearingresistance,tan 1.25Effectivecohesion c 1.25

Undrainedshearstrength cu 1.4

29

Unconfinedstrength qu 1.4


CarryoutULScombination1 A:Needtoapplyvariablefactorstoactions

dependingonwhetherunfavourableorfavourable & permanent or variable;favourable&permanentorvariable;

A:2.4.2(9)NOTEUnfavourable(ordestabilising)andfavourable(orstabilising)permanentactionsmayinsomesituationsbe

id d i f i l If c = 1.35consideredascomingfromasinglesource.Iftheyareconsideredso,asinglepartialfactormaybeappliedtothesumoftheseactionsortothesumoftheireffects.

c = 1.0c = 1.0c = 1.35

A:thereforejustfactorupunfavourablevariableactionsby(1.5/1.35)andthenfactorresultingactions(SFs,BMs)by1.35.

Action Symbol Set A1Action Symbol SetA1factors

PermanentUnfavourable G

1.35

favourable 1 0

30

favourable 1.0



CarryoutULScombination1

M:Applypartialfactorof1.0tomaterialparameters.

Soilparameter Symbol SetM1factors

Angleofshearingresistance,tan 1.0Effectivecohesion c 1.0

Undrainedshearstrength cu 1.0Unconfinedstrength qu 0

31


SetupcalculationsforSLSandruncalc 2.4.8(2)Valuesofpartialfactorsforserviceabilitylimitstatesshouldnormally

be taken equal to 1 0betakenequalto1.0. 2.4.8(5)PAlimitingvalueforaparticulardeformationisthevalueatwhicha

serviceabilitylimitstate,suchasunacceptablecrackingorjammingofdoors,isdeemedtooccurinthesupportedstructure.Thislimitingvalueshallbeagreedd h d f h dduringthedesignofthesupportedstructure.

9.8.1(2)PDesignvaluesofearthpressuresfortheserviceabilitylimitstateshallbederivedusingcharacteristicvaluesofallsoilparameters;

il b lSoilparameter Symbol SLSMfactors

Angleofshearingresistance,tan 1.0Effectivecohesion c 1.0

Undrainedshearstrength cu 1.0U fi d t th 1 0

32

Unconfinedstrength qu 1.0


9.8.1(3)PPermanentsurchargeloadsbehindtheretainingwallshallbederivedi th i h t i ti l

calculationsforSLSusingtheircharacteristicvalues;

9.8.2(4)PItshallbeconsideredtowhatextentvariableactions,suchasvibrationscausedbytrafficloadsbehindtheretainingwall,contributetothewalldisplacement;

AccidentaloverdigneednotbeconsideredintheSLSanalysis. Checkifwalldisplacementisacceptable

Action Symbol SLS AAction Symbol SLSAfactors

PermanentUnfavourable G 1.0Permanent Gfavourable 1.0


installation movements ref C580

33

favourable 0


Determinedesignforcestobeusedforthestructuralpiledesign

Thedesignsectionforces(i.e.bendingmomentandshear)intheULSshallbethemaximumoftheresultingvaluesbetweenCombination1andCombination2.

Ifcrackcontrolisrequired(e.g.forwalltobedesignedasgpermanentstructure),crackwidthcalculationwillbecarriedoutusingtheresultingsectionforcesfromtheSLSanalysis.

34


Structuraldesignofpilesection

Reducedconcretesectiondiameterforstructuraldesign;

Lap length & anchorage different;Laplength&anchoragedifferent; Rulesonlappingbundlebars;A h t h d i diff t Approachtosheardesigndifferent.

35


Example cantileverwithlongtermproppingg p pp gComparisonwithC580

Characteristic values of geotechnical parameters [ = design parameters for SLS analysis]:

Stratum Top Level cu cu with z ' 'cv k d = k.'cv c' ko Eu Eu with z E'v E'v with zmOD kN/m3 kPa kPa kPa kPa kPa kPa kPa

Made Ground 8.03 18 n/a n/a 30 28 1.0 28.0 n/a 0.50 n/a n/a 20,000 0Sand 7 18 n/a n/a 30 28 1.0 28.0 n/a 0.50 n/a n/a 20,000 0Drained Clay 5 20 n/a n/a 30 25 1.0 25.0 0 1 n/a n/a 16,200 0Undrained Mudstone 4 21 300 150 n/a n/a 1.0 n/a n/a 1 180,000 90,000 n/a n/aDrained Mudstone 4 21 n/a n/a 28 23 1 0 23 0 5 1 n/a n/a 108 000 54000Drained Mudstone 4 21 n/a n/a 28 23 1.0 23.0 5 1 n/a n/a 108,000 54000

Design values of geotechnical parameters for ULS Combination 1:

Stratum Top Level cu cu with z ' 'cv k d = k.'cv c' ko Eu Eu with z E'v E'v with zmTD kN/m3 kPa kPa kPa kPa kPa kPa kPa

Made Ground 8.03 18 n/a n/a 30.0 28.0 1.0 28.0 n/a 0.50 n/a n/a 14285.7 0.0Sand 7 18 n/a n/a 30.0 28.0 1.0 28.0 n/a 0.50 n/a n/a 14285.7 0.0Drained Clay 5 20 n/a n/a 30.0 25.0 1.0 25.0 0.0 1.00 n/a n/a 11571.4 0.0Undrained Mudstone 4 21 300.0 150.0 n/a n/a 1.0 n/a n/a 1.00 128571.4 64285.7 n/a n/aDrained Mudstone 4 21 n/a n/a 28.0 23.0 1.0 23.0 4.0 1.00 n/a n/a 77142.9 38571.4

Design values of geotechnical parameters for ULS Combination 2:

Stratum Top Level cu cu with z ' 'cv k d = k.'cv c' ko Eu Eu with z E'v E'v with z3

36

mTD kN/m3 kPa kPa kPa kPa kPa kPa kPaMade Ground 8.03 18 n/a n/a 24.8 23.0 1.0 23.0 n/a 0.5 n/a n/a 14285.7 0.0Sand 7 18 n/a n/a 24.8 23.0 1.0 23.0 n/a 0.5 n/a n/a 14285.7 0.0Drained Clay 5 20 n/a n/a 24.8 20.5 1.0 20.5 0.0 1 n/a n/a 11571.4 0.0Undrained Mudstone 4 21 214.3 107.1 n/a n/a 1.0 n/a n/a 1 128571.4 64285.7 n/a n/aDrained Mudstone 4 21 n/a n/a 23.0 18.8 1.0 18.8 4.0 1 n/a n/a 77142.9 38571.4


Comparisonofdisplacements

6.00

6.50

7.00

7.50

8.00

3 00

3.50

4.00

4.50

5.00

5.50

v

a

t

i

o

n

(

m

O

D

)

Groundwater SLS Design value

0.50

1.00

1.50

2.00

2.50

3.00

E

l

e

v

-2.00

-1.50

-1.00

-0.50

0.00

0 0.01 0.02 0.03

Displacement (m)

37

Displacement (m)

C580 SLS displacements

EC7 SLS displacements


ComparisonofBMs ULS capacity C580 ULSC580 SLS * 1.35 ULS Combination 1

ULS C bi ti 2ULS Combination 2

6.50

7.00

7.50

8.00

EC7peak


ComparisonofSFs ULS capacity C580 ULSC580 SLS * 1.35 ULS Combination 1

ULS C bi ti 2ULS Combination 2

6.50

7.00

7.50

8.00

3 50

4.00

4.50

5.00

5.50

6.00

o

n

(

m

O

D

)

1.00

1.50

2.00

2.50

3.00

3.50

E

l

e

v

a

t

i

o

Groundwater ULS Comb 1 SLS Design value

Groundwater ULS Comb 2 ULS Design value -2.00

-1.50

-1.00

-0.50

0.00

0.50

EC7peak~15%higher

39

value value -300 -200 -100 0 100 200 300ULS Shear Force per pile (kN)


Execution of special geotechnical works:

Constructiondifferences Executionofspecialgeotechnicalworks:

BSEN12063:1999 Sheetpilewalls BSEN1536:2010 Boredpiles

BS EN 1538: 2012 Diaphragm walls BSEN1538:2012 Diaphragmwalls

Differencesbetweenthesecodesandindustrystandard ICE SPERW e g wrt bored piles:standardICESPERW,e.g.wrtboredpiles: Differencesinplanlocationandverticalitytolerances; Differencesincageinstallationtolerances; Differences in minimum amount of reinforcement;Differencesinminimumamountofreinforcement; Limitsonreinforcementspacing; Differencesinacceptablemethodsofconcretingindryconditions;

40


KeystepsinthedesignofembeddedwallstoEC7Conclusion&summary

y p g

Highlightedthedifferencesandsimilarities SimilarphilosophytoC580andBS8002 OurinitialexperienceisthatEC7providesslightlyhigher

BMsandSFs

Groundwater & drainage Groundwater&drainage Beawareofdifferences

inexecutionstandards

41


KeystepsinthedesignofembeddedwallstoEC7Conclusion&summary

y p g

Highlightedthedifferencesandsimilarities SimilarphilosophytoC580andBS8002 OurinitialexperienceisthatEC7providesslightlyhigher

BMsandSFs

Groundwater & drainage Groundwater&drainage Beawareofdifferences

inexecutionstandards

Thankyou

42

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Ec7 Embedded Wall Design Nigg

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