advanced foundation engineering (57011)

7/24/2019 Advanced Foundation Engineering (57011)

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AdvancedFoundationEngineering

IVYear

B.Tech,

ISemester

Dr.PVSNPavan Kumar

Associate Professor

GuruNanakInstitutionsTechnicalCampus

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Syllabus Unit 1BearingCapacitytheories,eccentricand

,

Unit 2

Settlement

of

foundations

Unit 4

Pile

foundations

Settlement

of

piles

Unit 5Lateralearthpressuretheories

Retainingwalls

Unit 6

sheet

pile

walls

Unit 7Caissons&wellfoundations

Unit

8

Expansive

soil

and

treatment

methodsDr.PVSNPavanKumar


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TEXTBOOKS

th. , . . ,PWS Publishing, Singapore

2. Bowles, J.E., (1988) Foundation Analysis and Design 4th edition,- .

3. Geotechnical Engineering : Principles and practices of soil mechanics and

foundation engineering by VNS Murthy, Taylor & Francis Group

REFERENCE BOOKS

1. Geotechnical En ineerin b C. Venkataramah NewA e InternationalPvt. Ltd, Publishers (2002).

2. Analysis and Design of structures Swami Saran, Oxford & IBH. .

3. Basic and Applied Soil Mechanics by Gopal Ranjan & ASR Rao, NewAge International Pvt. Ltd, Publishers (2002).

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Unit I

Bearingcapacitytheories

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Contents

Introduction

Terminology,Terzaghi andMeyerhofbearingcapacity

theories Hansenbearingcapacitytheory

Vesic bearingcapacitytheory

Foundationsonlayeredsoil

Tutorialsand

assignments

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IntroductionFoundation

e es gne s ruc uresres ngon eear

mustbecarriedbysomekindinterfacingelementca e oun a on.

Foundation

transmits

the

load

into

the

supporting

soilorrock.

Structurewillconsistofthreeparts Super

structure,sub

structure

and

foundation.

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Introduction

Foundationsare

classified

as

shallow

foundations

anddeepfoundations.

Shallow

foundation

have

D/B

1.Footings,combinedfootings,strapfootingsormat/raftfoundations.

Dee

foundationhave

L B

4.Exam les ilesdrilledpiersordrilledcaissons.

spreadingtheloadslaterallyandsupportcolumn.

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Introduction

Matisaspecialfootingusedtosupportseveral

randoml s acedcolumnsortosu ortseveral

rowsof

parallel

columns.

ratherthanhorizontally.

tostructureislessthanbearingcapacityofsoiland

.

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Introduction

Fewbuildingscollapsefromexcessivesettlements,

member.Unsightly

wall

and

floor

cracks

uneven

, .

Variability

of

soil

in

combination

with

unanticipated

oa sorsu sequen so movemen s ear qua es

canresultinsettlementproblems.

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Bearingcapacity

Soilmustbecapableofcarryingtheloadsfromthe

structure lacedonitwithoutshearfailureandwith

resultingsettlements

within

tolerable

limits.

, u

pressurethefootingissubjectedforshearfailureof

Footingpunchesintothegroundwitha

.

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thefooting

is

subjected

to

avoid

abase

shear

.

qa=

FSult

q

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Bearingcapacitytheory(=0)

S=c+tan

Unitwidthstrip

footing,Element1

Rotationoffootin about ointo

Element2

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Bearingcapacitytheory

Element1Element2

1and3=Majorandminorprincipalstress

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Bearingcapacityequation

Element2

32

12=q +2c(for=0)Element1

= =q +2c11 =q +2c+2c=q+4c(for=0)

ult

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Bearingcapacity(csoil)Element2

Soilwedge

agb moves

down

Lateralpressures

develo alon lineag andtranslates

blockagf

horizontallyagainst

Element1

.

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Bearingcapacity(csoil)

DeterminethepassivepressurePPandconsiderthe

bearingcapacity,

qultas

follows

ult c q

Some

limitations

of

the

above

procedure

isZoneagf isneglected.

Footinginterfaceisroughandcontributestoroughness

e ect

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Bearingcapacity(csoil)Shapeofblockagfe poorlydefinesthezoneresistingthe

wedgemovementintothesoil.Alogarithmicspiralbetter

defines

the

slip

surface

from

g

to

f

and

partly

along

f

to

e.Solutionisforunitwidthstripacrossaverylongfooting,so

ithastobeadjustedforround,square,orfinitelength

footings

(it

needs

shape

factors).Shearresistancefromplaneae tothegroundsurfacehas

beenneglected,itrequiressomekindofadjustment(i.e.

Ifloadisinclinedfromvertical,inclinationfactorsare

.

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,

Meyerhofbearing

capacity

theory,

1963

Hansen earingcapacityt eory,1970

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Terzaghi bearingcapacityequation(1943)

Acomprehensivetheoryfortheevaluationofthe

ultimatebearin ca acit ofrou hshallowfoundations

(DfB). A licableforacontinuous orstri foundation i.e.

onewhosewidthtolengthratioapproacheszero).

mayalsobeassumedtobereplacedbyanequivalent

surchar e, = D where isaunitwei htofsoil .

Generalshearfailureisassumed.

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Terzaghi bearingcapacitytheory

Radial shear zones ADF and CDE, with the curves DE and DF being arcs of a

lo arithmic s iral.

Two triangular Rankine passive zones AFH and CEG

Shear resistance of soil above the base of footing is neglected i.e. along the failure

Dr.PVSNPavanKumar

surfaces GI and HJ was neglected.


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Terzaghi bearingcapacityequation

Consideringverticalequilibriumofforcesonfooting

Sc=1+0.3

L

B

Rectangularfooting

Sq=1

S=10.2L

B

, ,

=angleofinternalfriction,q=effectiveoverburdenpressureatbase

Dr.PVSNPavanKumar

o oo ng

kp

=Coefficientofpassivepressure


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Terzaghi bearingcapacitytheory

Terzaghi developedbearingcapacityequations

considerin a eneralshearfailureinadensesoil

andalocal

shear

failure

for

aloose

soil.

cohesionandas"

.

For local shear failure modified bearing capacity

ac ors are e erm ne rom = an

. an

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Tutorial1

equation for a square footing and soil properties shownin Figure below. B = 3m Use factor of safety = 3.0ca cu a e qa

=20

c . , q . , .

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Meyerhofbearingcapacitytheory

Terzaghi bearingcapacitytheoryhasfollowingshortcomings

Shearresistance

along

failure

surface

in

soil

above

the

basefoundationisneglected(alongGIandHJ).

Loadonthefoundationmaybeinclined.

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Meyerhofbearingcapacitytheory

bearingcapacity

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Meyerhofbearingcapacityequation

qult=cNcScdcic+qNqSqdqiq+0.5BNS d i c, q,

Sc,Sq,S

Shape

factors

c, q, ept actors

ic,iq,i

inclination

factors

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MeyerhofbearingcapacityequationAny

Anycot1= qc NN

tan2 LB

KS pc 2.01+= D

Kd pc 2.01+=

>10 >102q

=

( ) 4.1tan1= qNN B

KSS pq 1.01+== D

Kdd pq 1.01+==

=0 =0

1== SSq1== ddq

Any

FordepthD=BMeyerhof

qultissameasTerzaghi

theory.Differenceismore

2

901

==

qc ii

>10 pronouncedat

larger

D/B

ratios.

Inclinationfactorsreduce

1

=

i

Dr.PVSNPavanKumar

=0 thebearingcapacitywhen

theload

is

inclined

from

vertical.

=


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Tutorial

A foundation column has to carr a ross allowable total mass of15,290 kg. The depth of foundation is 0.7m. The load is inclined at

angle 20 to the vertical as shown in Fig.1 below. Determine thew t o t e oun at on, . se actor o sa ety o . se

Meyerhofs method. For = 30, Nc = 30.14, Nq = 18.4, N = 22.4Dec 2012

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Tutorialqult=cNcScdcic+qNqSqdqiq+0.5BNS d i C=0;=30;Nc=30.14,N =18.4,N =22.4

q=18*0.7=12.6

kN/m

2

= = = c q

kp =3

c . . q . .

ic=iq=(1(20/90))2=0.60i=(1(20/30))

2 =0.11

qult =15290 BB=0.75m

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Pavan

Kumar


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Tutorial

Afooting

of

size

2m

x4m

is

placed

at

adepth

of

1.5m

belowthegroundsurface.Estimatethenetsafe

loadthatcanbesupportedbythefooting.Take

factorofsafety=2.5,c=22kN/m2.=30 Nc=30.1,Nq=18.4,N=16.7.UseMeyerhof

recommendation

(June/July

2014)

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Pavan

Kumar


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Hansenbearingcapacitytheory(1970)

Hansen theory extends the bearing capacity equation for a footing

Dr.PVSN

Pavan

Kumar

tilted from horizontal and possibility of slope of ground supporting the

footing.


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qult=cNcScdcicgcbc+qNqSqdqiqgqbq+0.5BNS d i gb

B.C.Factors ShapeFactors

BNq=qc

tan2

45tan eNq

+=

LNcc

tan1

B

Sq +=

tan15.1 = qNN 6.04.01 =L

BS

IncaseofeccentricloadingBandLarereplacedbyBandL,the

effective dimensions of footin B=B2e L=L2e

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Pavan

Kumar


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DepthFactors InclinationFactors

c .. +=

1/ =B

DforBDK 1

=q

q

qc

N

ii

1)/(tan 1 >= B

forBDK

Kin

radians

cot

5.01

+

=a

qAcV

Hi

kdq2

)sin1(tan21 +=5

7.01

= H

i

Hishorizontalloadonfooting,Vverticalloadonfooting,A=BL(effectivearea),

. co+ a

c

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Pavan

Kumar

a . .


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Groundfactors baseonslo e

Basefactors(tiltedbase)

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Pavan

Kumar


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For=0

qult=5.14su(1+sc+dcicbcgc)+q

Kisdefinedabove

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Pavan

Kumar


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Vesic bearingcapacitytheory(1973)

Vesic conformed the basic nature of failure surface

similar to Terza hi.

Inclined surface AC and BC make an angle 45+ with

horizontal instead of . 2

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Pavan

Kumar


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Sameas

Hansen

theory

except

N

qult=cNcScdcicgcbc+qNqSqdqiqgqbq+0.5BNS d i gb

B.C.Factors ShapeFactors DepthFactors

=

cot1= qc NN LB

NS

c

q

c +=1c ..

1/ =

B

DforBDK

tan2

245tan eNq

+=

tan1L

Sq += 1)/(tan 1 >=

BforBDK

Kinradians

tan12 += qNN 6.04.01 = LS kdq2

)sin1(tan21 +=

allford 0.1=

Dr.PVSN

Pavan

Kumar

b h ( )


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InclinationFactors Ground factors

isinradians

Basefactors tilted

base

Dr.PVSN

Pavan

Kumar

V i b i i h (1973)


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u=0

Dr.PVSN

Pavan

Kumar

T i l


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Tutorial

Compare the ultimate bearing capacity of a strip footing 1.5m

wide with its base at a depth of 1m resting on a dry sand

stratum with c = 0, = 3 8 and d = 17 kN/m3. UseMeyerhof, Hansen and Vesic theory (June 2010)

Dr.PVSN

Pavan

Kumar

I li d l d d f ti


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Inclinedloadedfooting

Anal sisofhorizontalload Eccentricload

Dr.PVSN

Pavan

Kumar

Bearing capacity of footings subjected to


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Bearingcapacityoffootingssubjectedto

Foundation subjected to lateral loads and momentsresult in eccentric loadin .

If point of application of resultant of all loads is awayfrom centriod results in eccentric loading.

Eccentricity, e is distance between the point of

application of resultant load and centre of footing. Thiss ou e < .

Foundationsubjectedtoaneccentricverticalloadtilts

pressureincreasesonthesideoftiltanddecreaseson

Dr.PVSN

Pavan

Kumar

Bearing capacity of footings subjected to eccentric


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Bearingcapacityoffootingssubjectedtoeccentric

loadin

Eccentricallyloaded

footing

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Pavan

Kumar



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loadin

Eccentricityabout

yaxisEccentricityabout

xandyaxis

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Pavan

Kumar



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loadin

Meyerhofindicatetheeffectivefootingdimensions

L'=L2exand

B'

=B

2ey

Effectiveareaoffooting,A=L'B

Ultimateload

bearing

capacity

of

afooting

subjectedtoeccentricloads=Q'ult=quA

=ultimatebearin ca acit ofthefootin of

dimensionL

xB

Dr.PVSN

Pavan

Kumar

M i d i i b


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Maximumandminimumbasepressures

Maximumpressuredevelops

atCandminimumatDgiven

asfollows

Dr.PVSN

Pavan

Kumar

Eccentric loading


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Eccentricloading

ncreaseo

eccen r c y

o

oa

ncreases

e

maximumpressureatoneedgeoffootingand

ecreases epressurea o eren ens on .

Soilis

poor

in

carrying

tensile

stress

and

the

eccentricityislimitedtoanareaknownasKern.

ex1

11

5.014.4

d

BN s += 2

1.114.4

d

BN s +=

21

212

NN

NNNc +

=Circularfooting33.005.5

BN +=

66.005.5

BN +=

Dr.PVSN

Pavan

Kumar

1d 1d

Foundation on layered soil


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Foundationonlayeredsoil

( )dHdModi ied 2111

+=

H

( )cdHcdcModified 2111

+=

Ultimatebearingcapacity,qultisdeterminedfrommodifiedc,

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Pavan Kumar


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UNITIISettlementoffoundations

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Elasticsettlementoffootingsinsandsandclays

FootingsonsoilsofFinitethickness

Schmertamann's method

Janbu method

Dr.PVSNPavanKumar

Allowable bearing capacity


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Allowablebearingcapacity

Inmanycases,theallowablesettlementofa

bearingcapacity.

Settlementsarelargewhenthewidthoffootingis

large

Dr.PVSNPavanKumar

Causes of settlement


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Causesofsettlement

Duetoweightofrecentlyplacedfill Fa o groun water eve orpumping

Under

ground

mining/tunneling Formationofsinkholes

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duetotheapplicationofloadisknownas.

Dr.PVSNPavanKumar

Introduction


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Introduction

Foundationsettlementsmustbeestimatedwithgreat

careforbuildin s brid es towers ower lants and

similarhighcoststructures.

Forstructuressuchasfills earthdams braced

sheeting,andretainingwallsagreatermarginoferror

inthesettlements. WhatistheconsequenceofUnderandoverprediction

ofsettlements?

Underprediction Unsafedesignandfailureofstructure.

caissonfoundationorimprovementofsoil.Dr.PVSNPavanKumar

I i


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In r i n

D

Dqult

Additional stress due to the footing produces a time

, , ,

and elastic distortions in a limited influence zone beneath theloaded area.

The statistical accumulation of movements in the direction of

interest is the settlement. Dr.PVSNPavanKumar

Introduction


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Introduction

Particleslidingandrollingproduceadecreaseinthe

Onlyasmallfractionofsettlementiselasticand

ofsample.

nsp eo a oveso s rea e asae as cma er a

withparametersEs,G', , and ksto estimate

se emen s.

Dr.PVSNPavanKumar

Classification of settlements


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Classificationofsettlements

Immediate, or those that take place as the load isli r i hin im ri f 7

Applicable for all fine-grained soils including silts andclays with a degree of saturation,s 90 % and for allcoarse-grained soils with a large coefficient of

permeability above 10-3m/s.

onso a on se emen s are ose a are me-dependent and take months to years to develop.

consolidation settlement for over 700 years. The lean iscaused b the consolidation settlement bein reater onone side.

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important.

(S=100%)andnegligibleforS=0

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LeaningtowerofPisa


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g

Towercompletedbetween1360to1370.Angleof

tiltatthattimeis3fromrestoftower.

Ittook

200

years

to

complete

project.

,

about2.5metersintotheground.

yen o e cen ury e o a wasa ou

5.5degrees.

Towerisclearly

on

the

brink

of

collapse.

Pressureonsoil62to930kPa.

Aminorearthquakecouldcauseittotopple.Dr.PVSNPavanKumar

Classificationofsettlement


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Secondary

Compression:

e aye progress ve s ppage o gra n as e par c es

adjust themselves to a medium dense condition.Settlement due to secondary compression

tcp

ste

og1 0+

= e0initialvoidratio

Hthicknessoflayer

tisanytimetptimeforcompletionofprimary

conso at on

Dr.PVSNPavanKumar

Depth of influence, H is taken as

4B to 5B or hard layer with bottom


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4B to 5B or hard layer with bottom

qulth1

layer having E ten times higherthan top layer

E1,1,1,q 1

.

Theory of elasticity assumes thatsoil is homo enous and isotro ic

E , ,q

h2 H

=

n

iihsettlementTotal H

,

h3

=1

= =q

3,3,3, q3

sE

foundationonlayeredsoilDr.

PVSN

Pavan

Kumar


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(Es9

G', , and ks)

Duetoaboveproblemsgreatertendencytouse

ns tutestssuc asSPT,DCPT,SCPT,P ate oa

testetc.

Thesetestsgivehorizontalvaluesinsteadofverticalvaluesactuallyneeded(Anisotropy)

Dr.PVSN

Pavan

Kumar


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UnconfinedCompressiontest Triaxial Compressiontest

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Pavan

Kumar


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s

Triaxial test Insitutestssuc asSPT,CPT,pressuremeter

test,flatdilatometer.

Theabovetestsgivemodulusofelasticityin

horizontaldirectionbutthemodulusofelasticity

v u .

Dr.PVSN

Pavan

Kumar

Modulusofelasticityfromfieldtests


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y

Dr.

PVSN

Pavan

Kumar

Stressincreaseinsoilduetofootingpressure


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2V:1HMethoderme o s

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PVSN

Pavan

Kumar



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Dr.

PVSN

Pavan

Kumar



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Boussinesq theory(1885)givethestressatdifferent

ointsbelowthe roundsurfacedueto

concentratedload,lineandstriploads,rectangular

andcircularloadedareas.

Westergaard (1938)equationisusedestimateof

v strataoffineandcoarsematerials,asbeneatha

Dr.

PVSN

Pavan

Kumar

Immediatesettlement


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Settlement of the corner of a rectangular base of

' '

half

space can be computed from an equation

and Goodier (1951)] as follows

Dr.PVSNPavanKumar

Immediatesettlement


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q0=intensityofcontactpressureinunitsofEs

= east atera mens on o contr ut ng ase area

Es, = elastic soil parameters (Avg. mod of different layers)

1

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Depth

factor,If

ground,dependingonPoisson'sratioandL/B.Dr.PVSNPavanKumar

Immediatesettlement


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Aboveequationisapplicableforflexiblefootings.

decreasesby7%offlexiblefootings.

Settlementofrigidfooting=0.93xSettlementofflexiblefooting

Settlementofrigidfooting=0.8xSettlementofflexible

Obtaintheweightedaveragemodulusofelasticityofsoil

Dr.PVSNPavanKumar

Estimatethesettlementoftheraftormat

foundationforthefollowingdata.


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q0=134kPa BxL=33.5x39.5m

surfacetosandstonebedrockat 14m.Raftisat .

Esofclaylayerfrom3to6m=42.5Mpa

Esofclaylayerfrom6to14m=60Mpa

E forsandstone>500Mpa

=0.35

Dr.PVSNPavanKumar

Elasticsettlementoffoundations


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Netelasticsettlementforaflexiblesurface

footingis

e

B=widthoffoundation

=

Poisson

ratioE =Modulusofelasticityofsoil

If=InfluencefactorDr.PVSNPavanKumar

Elasticsettlementoffoundation


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InfluencefactorIf(Bowles,1988)

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SdCS =

Cr

=Rigidityfactortakenas0.8forhighlyrigid

foundation

d =de thfactor

Se=Settlementofasurfaceflexiblefooting

Dr.PVSNPavanKumar

Depthfactor,df


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Correction curves for elastic

settlement for rectangular

footings at different depthsDr.PVSNPavanKumar

Arectangularfootingof1.5mx1.0msizeexertsapressure

of150kN/m2 onacohesivesoilhavingEs=3x104 kN/m2


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andm=0.5.Determinetheelasticsettlementatthecenteroffootingassumingthefootingisflexible.Takethevalueof

, f . . , .

Asquarefootingof1.2msizeissubjectedtoapressureof2 .

settlementatthecornerofthefootingassumingthe

footin

is

ri id.

Take

the

avera e

influence

factor

I

=

0.82

andEs=4x104 kN/m2.

Dr.PVSNPavanKumar

Schmertmann method


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Schmertmann (1970) observed that variation ofstrain under the footing over sand is similar to thedistribution of vertical stress due to footing

pressure. Pressure bulb changes more rapidly from a depth of

about 0.4B to 0.6B and this depth is interpreted to

footings.

diagram to model the strain distribution with. , . , , . , ,

respectively for square and circular footing.Dr.PVSNPavanKumar

Schmertmann method


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ForstripfootingofL/B>10,maximumstrainwill

thebaseiszeroandimmediatelybelowthebase

Dr.PVSNPavanKumar

Schmertmann method

d l f


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SquareandcircularfootingStripfooting

z

q

I

+= 1.05.0

q=Netfoundationpressure=q0q

0 effectiveoverburdenpressure

atbase

q

p0 = effective overburdenpressure at depths B/2 and B for

square and strip foundations

respectively.Dr.PVSNPavanKumar

Schmertmann method


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Settlement=Areaofthestrain

0.1

0.5B

embedmentdepthandtimeshall

beadoptedasfollows:0.6 Variation

ofstrain

influenceForembedment

factor,Iz

forsquareFortime

2B

circular

footing

tinyearsDr.PVSNPavanKumar

Schmertmann method


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Forsquarefooting

Es=2.5qcForstripfooting,L/B10

Es

=3.5qcqc=Staticconepenetrationresistance

q=Netfoundationpressure=q0 q

Dr.PVSNPavanKumar

Schmertmann method


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Static cone penetration test is conducted in sub soil

layers of approximately constant values of qc

.

The strain influence factor I dia ram is laced

alongside cone penetration diagram beneath the

foundation to the same scale.

Settlement of each layer resulting from the net

contact pressureq is then calculated using the values

of Es

and Iz

appropriate to each layer.

Sum of the settlements in each layer is then

correcte or t e ept an creep actors

Dr.PVSNPavanKumar


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StaticCone

penetrationtest

Dr.PVSNPavanKumar

Estimate the elastic settlement by

S h t ' th d b ki f th


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Schmertmann's method by making use of therelationship qc = 4 Ncor kg/cm

2 where qc = static

cone penetration value in kg/cm2. Assume

settlement is required at the end of a period of 3years. Depth of foundation = 2m

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Dr.PVSNPavanKumar

Acontinuousfootingonalayerofsandisshownin

gure

e owa ong

w t

t e

var at on

o

t e


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gure e ow a ong w t t e var at on o t emodulusofelasticityofthesoil,Es.Assumingthat

= m an assum ngacreept meo

yearsforthecorrectionfactorC2.Calculatethee as cse emen o e oun a on,us ng e

straininfluencefactor(Nov2012).

Dr.PVSNPavanKumar


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Dr.PVSNPavanKumar

Janbu method

Janbu et al (1956) proposed an equation for


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Janbu et al. (1956) proposed an equation for evaluating the average settlement of flexible strip,

rectangular, square or circular foundations on

saturated clay soils (Poissons ratio, 0.5)

q0footingcontactpressure

Dr.PVSNPavanKumar

Janbu method


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Dr.PVSNPavanKumar

Janbu method


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Dr.PVSNPavanKumar


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ConsolidationtestsetupDr.PVSNPavanKumar

Consolidationtestme

(Min)

a gaugerea ng

0.5kg/cm2 1kg/cm2 2kg/cm2 4kg/cm2 8kg/cm2 16kg/cm2


100/535

g/ g/ g/ g/ g/ g/

Load

in

Unload

in

Loadin Unload

in

Loadin Unload

in

Loadin Unload

in

Loadin Unload

in

Loadin Unload

in

0

0.5

2

4

8

16

25

1

2

8

16

Dr.PVSNPavanKumar

Consolidationsettlements


101/535

VirginCompressionornormal

RecompressionorOverConsolidation

VirginCompression

ornormal

consolidation

Swelling

Resultofconsolidationtest

Dr.PVSNPavanKumar


Settlements of finegrained, saturated cohesiveil ill b ti d d t d lid ti


102/535

Settlementsoffine grained,saturatedcohesivesoilswillbetimedependent,andconsolidation

eory susua yuse .

Incaseofnormallyconsolidatedclays

wherecc=compression index from the e versuslog p plot = 0.009(LL 10),LL=Liquidlimit(%)

eo= in situ void ratio at the middle of clay stratumH = Stratum thickness for a thick stratum divide

into several layersDr.PVSNPavanKumar


po =effectiveoverburdenpressureatmidheightof


103/535

p o effective overburden pressure at mid height of

p = average increase in pressure at middle of clay

Overconsolidated clays

Dr.PVSNPavanKumar

Preconsolidated clay


104/535

Recompression

Vir in

Compression

Normal

Dr.PVSNPavanKumar


If soil is preconsolidated


105/535

p

Crrecompressionindex

C com ressionindex

Dr.PVSNPavanKumar

Consolidationsettlement

Otherequationtodeterminethesettlementof


106/535

qfoundationis

mv=Coefficientofvolumecompressibility

p=increaseofpressureinmiddleofclaylayer

H=thicknessofclaylayer

Dr.PVSNPavanKumar

A square footing 1.2m1.2m rests at a depth of 1m

.

normally consolidated, having an unconfined


107/535

y , g2.

liquid limit of 30%, sat= 17.8 kN/m3, w=28% and

G = 2.68. Determine the load which the footin

can carry safely with a factor of safety of 3

against shear. Also determine the settlement if the

footing is loaded with this safe load (May 2010).

Square footing

qu= 1.3cNc+ Nq+ 0.4BN= = =, q ,

Dr.PVSNPavanKumar


108/535

Maximum

settlement

Dr.PVSNPavanKumar

Allowablesettlement

Settlements can be computed for various points suchas corner center or beneath the lightest and heaviest


109/535

as corner, center, or beneath the lightest and heaviest

differential settlement between adjacent points.

If the entire structure moves verticall some amountor rotates as a plane rigid body, this movement willnot generally cause structural or architectural distress.

a s ruc ure se es mm on one s e an mmon the other with a linear settlement variationbetween the two oints structural dama e is notlikely to develop but there are aesthetic and publicconfidence considerations.

e emen = mm eren a se emen = mm

Tilt = (10020)/L Dr.PVSNPavanKumar

Allowablesettlement

Localsettlementsbelowtiltlinewillcausethe


110/535

.

Initialsettlements

that

occur

during

construction

canusua y e en ur ngcomp e ono

building.Acrackedwallorwarpedroofismuch

more cu oconcea .

Dr.PVSNPavanKumar

Allowablesettlement


111/535

Longtimespansallowthestructuretoadjustandbetter

resistdifferentialmovementDr.PVSNPavanKumar


112/535

foundations

Whatarethetypesofsettlementsandhow

conso at onsett ement sest mate

Dr.PVSNPavanKumar


113/535

UNITIIIPileFoundations

Dr.PVSNPavanKumar


114/535

Dynamicmethods Pi egroups

Negativeskinfriction

Underreamedpiles.

Dr.PVSNPavanKumar

Necessity

Shallowfoundationsarenormallyusedwherethesoil close to the round surface and u to the


115/535

soilclosetothe roundsurfaceandu tothe

influencezonepossesssufficientbearingstrength

tocarr thesu erstructureloadwithoutcausin distresstothesuperstructureduetosettlement.

theloadfromthestructureistobetransferredto

Thestructuralloadsmaybetransferredtodeeper.

Dr.PVSNPavanKumar


116/535

Dr.PVSNPavanKumar

Endbearingandfrictionalpiles


117/535

Endbearingpile Frictionalpile

Dr.PVSNPavanKumar


118/535

through water or soft soil to a suitable bearing

.

strata and settlements are less.

surrounding granular soil along their length by

.

Piles carry super imposed load through endear ng an s n r ct on.

Dr.PVSNPavanKumar

En rin n fri i n l il


119/535

EndbearingcumfrictionalpileDr.PVSNPavanKumar

Pilefoundations

Piles are long slender columns either driven,


120/535

.

Driven piles are made of a variety of materialssuch as

concrete, steel, timber

Castinsitu piles are concrete piles.

If the diameter of a boredcastinsitu ile is

greater than about 0.75 m, it is referred as adrilled ier caisson or shaft.

Dr.PVSNPavanKumar

ClassificationofPilefoundations

Pilesmaybesubjectedtoverticalcompression,


121/535

, .

PilesareclassifiedasshortorlongbasedonL/dratio.

Pilesareconstructedasverticalorinclinedpiles.

Inclinedorbatterpilesareusedtocarrylargelateralloads.

Dr.PVSNPavanKumar

Usesofpiles


122/535

U lift tension

/anchorPiles

CompressionPilesDr.PVSNPavanKumar


123/535

W

Pilessubjectedtolateralload

Dr.PVSNPavanKumar

Timberpiles


124/535

Protectingshoe

SplicingDr.PVSNPavanKumar

Timberpiles

Materials:Timberpilesaremadeoftreetrunkswiththebranchestrimmedoff.Suchpilesshallbeofsoundquality


125/535

andfreeofdefects.

Length

of

piles:15mormore.Forlargerlengthstheendsarespliced.

Diameterofthepilesatthebuttendvaryfrom30to40

cmandattipendmorethan15cm.

Life:Pilesentirelysubmergedinwaterlastlongifmarine

borersarenotpresent.Thelifeofpilessubjectedto

alternatewettinganddryingisless.Pilesshallbetreatedw awoo preserva ve,usua ycreoso ea g m

forpilesinfreshwaterand350kg/m3 inseawater.Dr.PVSNPavanKumar

Timberpiles

Driving:Crushingofthefibersonthehead(or


126/535

,

ringaroundthebutt(top).

ax mum es gn oa perp e s ess an

kN.

Timberpilesarelessexpensiveinplaceswheretimberisplentiful.

Afterbeingdriventofinaldepth,allpileheads,

treatedoruntreated,shouldbesawedsquareto

soundundamagedwoodtoreceivethepilecap.Dr.PVSNPavanKumar

Timberpiles


127/535

Dr.PVSNPavanKumar

ConcretePiles

Eitherprecastorcastinsitupiles.


128/535

castingyardandthentransportedtothesiteof

.

Precastpilesaremadeofuniformsectionswith

. Taperedpilesaremanufacturedwhengreater

ear ngres s ance srequ re .

Normallypilesofsquareoroctagonalsections

aremanufactured.Theseshapesareeasytocast

inhorizontalposition.Dr.PVSNPavanKumar

ConcretePiles

Necessaryreinforcementisprovidedtotakecareofhandlin stresses.


129/535

Pilesarealsoprestressed.

approximately2000kN andforprecastpiles

. .

Dr.PVSNPavanKumar


130/535

Castinplace

concretepiles

Dr.PVSNPavanKumar

PrecastDrivenpiles

es may e o m er, s ee or precas concre e.

They are driven either vertical or inclined.

,


131/535

,single acting, double acting and differential acting steam

hammer, diesel, hydraulic and vibratory hammers. Compaction piles: Pile is driven into granular soil

displaces the surrounding soil equal to the volume of the.

Compacts the soil around the sides of pile.

The dis laced soil articles enter the soil s aces of theadjacent mass which leads to densification of the mass.

compactionofthesoilmassaroundapileincreasesitsbearingcapacity.

Dr.PVSNPavanKumar

Compactionpiles

Compacts

sandy

soil


132/535

2 1

Decreases

strength

of

clay

soil

which

gradually

regains

with

time

Dr.PVSNPavanKumar

PrecastDrivenpiles

e s r ven n osa ura e s y orco es veso w

notdensify thesoilaroundthepilebecauseofitspoordrainagequalities.

Di l d il i l h id


133/535

Displacedsoilparticlescannotenterthevoidspace

unlessthewaterintheporesispushedout. tress eve ope nso uetop e r v ng aveto

bebornebyporewater.

andaconsequentdecreaseinthebearingcapacityofthesoil.

Immediateeffectofpiledrivingistodecreasein

bearingcapacityofsoil.Remoldedsoilregainspart

disturbedparticleswithtime(thixotrophy).Dr.PVSNPavanKumar

PrecastDrivenpiles

Advantages: Can be precasted to the required specifications, any

, .


134/535

,

Progress of the work is rapid.

capacity.

Construction work is neat and clean,

Supervision of work at the site is reduced Storage space required is very much less.

Used in sites where a fear of meeting ground water

under pressure due to drill holes. re erre orp es nw ar s ruc uresor e es.

Dr.PVSNPavanKumar

PrecastDrivenpiles

Disadvantgaes: Must be properly reinforced to with

stand handling stresses during transportation and

r v ng.


135/535

g

Requires heavy equipment for handling and driving. Method involves cutting off extra lengths or adding

more lengths thus increases the cost of project.

They are not suitable in soils of poor drainagequalities due to heaving of the soil or the lifting of

the driven piles during the driving of a new pile.

Foundationsofadjacentstructuresarelikelytobe

affectedduetothevibrationsgenerated.Dr.PVSNPavanKumar

Drivencastinsitupile


136/535

Dr.PVSNPavanKumar


137/535

depthwiththeendclosedbyadetachable

.

Tubeisnextconcretedandtheshellis

. Insomecasestheshellwillnotbewithdrawn.

Dr.PVSNPavanKumar

BoredCast insitupiles

Constructedbymakingholesinthegroundtotherequireddepthandthenfillingtheholewithconcrete.


138/535

concrete.

Straightboredpilesorpileswithoneormorebulbsatintervalsmaybecastatthesite.Thelattertypearecalledunderreamedpiles.

Advantages:Pilesofanysizeandlengthareconstructed,damageduetodrivingandhandling

,

adjacentstructuresaresafe.Suitableinsoilsof.

Dr.PVSNPavanKumar

BoredCastinsitupiles

Disadvantages: Careful su ervision and ualit control of all the

materials is necessary for casting of piles


139/535

materials is necessary for casting of piles.

Sufficient stora e s ace is necessar forconstruction materials used in the construction.

No advantage of increased bearing capacity due

to compaction in granular soil.decreases by 3. Construction of these piles in holes with a heavy

ground water flow or artesian pressure is very

difficult.

Dr.PVSNPavanKumar

Steelpiles

They are rolled H shapes or pipe piles.

Designed to withstand large impact stresses

during hard driving


140/535

during hard driving.

Pi e iles are either welded or seamless steelpipes which may be driven either openend or

closedend.

Pipe piles are often filled with concrete after

.

Optimumloadrangeonsteelpilesis400to

.

Dr.PVSNPavanKumar

SteelHpiles

Before

driving Afterdriving


141/535

Dr.PVSNPavanKumar

Steelpipepiles


142/535

Dr.PVSNPavanKumar

Methodstodetermineloadcarrying

capacityofsingleverticalpilea c ear ngcapac yequa ons


143/535

UseofSPTandCPTvaluesFieldpileloadtests

Dr.PVSNPavanKumar

Staticcapacityofsinglepile

Bearingcapacityofpiledepends ,

T f il i i f bl


144/535

Typeofsoil,positionofwatertable

et o o nsta at on

Designofpileshouldbesafeagainstshearfailure

andsettlementswithinlimits.

Dr.PVSNPavanKumar


Ultimateload,Qu=Qb+Qf=

q = Ultimate bearing capacity of


145/535

qb=Ultimatebearingcapacityof

Ab=bearingareaofbaseofpile

f

s sfs=unitskinfriction

s= o a sur aceareao p e

embeddedbelowground

Dr.PVSNPavanKumar


Netultimateloadcapacityofpile,

'

s

n

isbqu AkqANqQ tan

100 += =

o

pile


146/535

pile

q

=averageeffectiveoverburdenpressureoverthe0

'q

=averagelateralearthpressurecoefficientsk

Pile Values of

n=no.oflayers

material

LowDr HighDr

Steel 20 0.5 1.0

s

oncrete . .

wood 2/3 1.5 4.0

Drivenpiles

Maximum

skin

friction

0.3m for

proper placement of concrete in

stem.

ep o oun a on, e ow

g.l > 0.6m.

Base width of wall is between

0.5 H to 0.7H.

For Rankine theory a vertical

line AB is drawn through the

heel point.0.6m

assumed along the vertical line

AB. This is justified if AC makes

an angle


277/535

does not intersect stem

i = angle of surcharge

To check the stability of wall, weight of soil above the heel in the zone ABC, Ws shall beconsidered, Weight of concrete in stem, Wc and active earth pressure force Pa shall be

considered. Dr.PVSNPavanKumar

Proportioningofgravityretainingwalls


278/535

Coulombtheorydirectlygivesearthpressureonthebackfaceofwall,

we g o so , sno o econs ere .

Dr.PVSNPavanKumar

Proportioningof

semi

gravity

retaining

slightly smaller than gravity retaining wall.

gravity retaining wall.


279/535

Dr.PVSNPavanKumar

Proportioningofcantileverretaining

Topwidthofwall>0.3m

Widthofbaseslabranges

from0.4Hto0.7H.

Widthofstematbottomis0.1H

Thicknessofbaseslabis

0.1H


280/535

Lengthoftoeprojectionis

0.1H

Dr.PVSNPavanKumar

ProportioningofretainingwallsProportionsforstemand

baseslabaresameas

cant everwa

Counterforts maybe

0.3mthick

0.3Hto0.7H


281/535

Conterfort retainingwallDr.PVSNPavanKumar

Stabilityofretainingwalls

Pa=activeearthpressure

Ph =PacosPv =Pasin=slopeangle

=wt w s

heelslabWc=Weightofwall

nc u ng ases a

Wt=resultantofwall,Wcandsoil,WsP = passive earth


282/535

Pp=passiveearth

pressureatthetoesideof

FR=Basesliding

resistanceDr.PVSNPavanKumar

StabilityofretainingwallsForceresistingsliding,FR=caB +Rtan+Pp

c =unitadhesionB=Widthofbaseofretainingwall

= =s

c

v =angleofwallfriction

Factorofsafetyagainstsliding,

IfF


283/535

ThepassivepressurePpshouldnotberelied

.Sliding

Dr.PVSNPavanKumar

Stabilityofretainingwalls

ac oro sa e yaga ns s ng


284/535

y g g y p

baseofwall

Dr.PVSNPavanKumar

Stabilityof

retaining

walls

Overturningandstabilizing

aboutpointo.

Factorofsafetyagainst

overturning,

Fo=o

R

M

> 2 0


285/535

>2.0

OverturningDr.PVSNPavanKumar

Stabilityofretainingwalls PRistheresultantofPaand

Wt.PRmeetsthebaseatm.

Ristheresultantofallthe

verticalforcesactingatmwithwt

aneccentricity

e.

Pressuredistributionattheaseo wa w amax mumqt


286/535

t

atthetoeandaminimumqhat

theheel.

BearingcapacityfailureDr.PVSNPavanKumar

Stabilityofretainingwall

Stressattoe,FS

q

b

e

b

Vq ut

+= 6

1

quultimatebearingcapacityconsideringthe

,

061 > = eV ,


287/535

.

BearingcapacityfailureDr.PVSNPavanKumar

StabilityofretainingwallAretainingwall

restingonmedium

oso so w a

byglobalfailure.

Slopestabilityisanalyzedbymethod

ofslices


288/535

BasefailureDr.PVSNPavanKumar

StabilityofretainingwallDraina e

Saturation of backfill of a retaining wall is

accompanied by a substantial pore water

ressure on the back of the wall andincreases the earth pressure on wall.

ItisessentialtoeliminateorreduceporeWee holepressurebyprovidingsuitabledrainage.

Drainscollectthewaterthatentersthe

backfillanddisposesofthroughoutletsin

thewallcalledweepholes.

t t l i b fi t i l


289/535

Verticaldraintopreventcloggingbyfinematerials.

Presentpracticeistousegeotextiles orgeogrids.

Dr.PVSNPavanKumar


weep holes are usually made by

em e ing 100 mm iameter pipes in

the wall

Vertical spacing between horizontal

rows of weep holes should not exceed.Weep hole


290/535

Horizontal spacing in a given row

Weephole

Inclineddrain epen s upon t e prov s ons ma e todirect the seepage water towards the

weep holes.Dr.PVSNPavanKumar



291/535

Horizontaldrain CombinationofHorizontalandinclineddrain

Dr.PVSNPavanKumar

Reinforcedearth

Soilcancarrycompressivestressbutitstensile

.

Reinforcedearthtechniqueisstrengtheningof

soil

by

inclusion

of

rods,

fibers,

bars

or

nets,

metalstrips,geogrids andgeotextiles.

Thisisaoldtechniquebutstudiedsystematically

byVidal(1969). Reinforced earth has several applications and


292/535

Reinforcedearthhasseveralapplicationsand

oneamon themisreinforcedearthretainin

walls.Dr.PVSNPavanKumar

MechanicallyStabilizedwalls


293/535

Wallunderconstruction Wallafterconstruction

Dr.PVSNPavanKumar

Typeofreinforcements Metallic

Metalstrip


294/535

BarmatDr.PVSNPavanKumar

Typeofreinforcements Ploymeric

Geogrid


295/535

GeogridDr.PVSNPavanKumar


296/535

ar san

mens ons

o

e n orce

so

waDesign consists of verifying external and internal stability

Dr.PVSNPavanKumar

TutorialAtypicalsectionofwallwithgranularbackfill

reinforcedwith

metal

stri s

is

ivenin

Fi ure

5.

Thefollowingdataareavailable.

= = = = , , , y ,

steel=1.75,FSonsoilfriction=1.5.Theother=

andS=1m.Checkforexternalstability?(Nov


297/535

Dr.PVSNPavanKumar

Metalstripsb=75mm,t=5mm

h=0.6mBackfill

3

S=1m

=34,C=0

6m wall

=36,c=0,=24,=18kN/m3For=36N =37.75

N=56.31


298/535

FoundationSoil

=36,=17kN/m3

Figure.5Dr.PVSNPavanKumar

Assignment4(Unit

5)

1. Aboveproblem

. retainingwalls

.

sketch

. r eas or no eson ou om ear pressure

theoryalong

with

assumptions.

5. ExplainhowtodetermineRankine Activeearth


299/535

pressureforinclinedbackfill

Dr.PVSNPavanKumar

UNITVI

Timberingoftrenches


300/535

Dr.PVSNPavanKumar

AnchoredSheetpiles

Determinationo Dept o em e mentin

sandsandclays

Timberingoftrenches

Earth ressuredia rams

Forces in struts.


301/535

Forcesinstruts.

Dr.PVSNPavanKumar

SheetpilewallsIntroduction

retainearth,wateroranyotherfillmaterial.

masonrywalls. Uses of sheet ile wall

Waterfrontstructures,forexample,inbuilding

wharfs,quays,andpiers

Buildingdiversiondams,suchascofferdams


302/535

Riverbankprotection

RetainingthesidesofcutsmadeinearthDr.PVSNPavanKumar

Useofsheetpilewalls


303/535

Earthretention

Dr.PVSNPavanKumar

Useo s eetpi ewa s


304/535

Waterfrontstructures,forexample,inbuildingwharfs,quays,andpiersDr.PVSNPavanKumar

Useo s eetpi ewa s


305/535

u ng

vers on

ams,

suchascofferdamsDr.PVSNPavanKumar

Useofsheetpilewalls


306/535

RiverBankprotectionDr.PVSNPavanKumar

Useofsheetpilewalls


307/535

RiverBankprotectionDr.PVSNPavanKumar

Useofsheetpilewalls


308/535


Useofsheetpilewalls


309/535


Reinforcedconcrete

Stee


310/535

Dr.PVSNPavanKumar

Timbersheetpilewalls


311/535

.

Usedfortemporarystructuressuchasbracedsheetingincuts.Dr.PVSNPavanKumar

Timbersheetpilewalls

Foruseinpermanentstructuresabovethewaterlevel,

properpreservativetreatmentisnecessary.

Theyhaveshortlife. m ers ee p esare o ne oeac o er y ongue

andgroovejoints.


312/535

ofstonesastheydislodgethejoints.Dr.PVSNPavanKumar

Concretesheetpilewalls


313/535

FlatsheetpileDr.PVSNPavanKumar



314/535

CorrugatedsheetpileDr.PVSNPavanKumar


Tongueandgroovejoint

Reinforced concrete sheet piles are precast concrete members

Thesepilesarerelativelyheavyandbulkyandtheydisplacelarge

volumesofsolidduringdriving.Increasesdrivingresistance.

Designofpilesshalltakeintoaccountthelargedrivingstresses

and suitable reinforcement has to be provided for this purpose


315/535

andsuitablereinforcementhastobeprovidedforthispurpose.

Dr.PVSNPavanKumar

Steelsheetpilewalls

Straightsheetpiling Shallowarchwebpiling

Archwebpiling Zpile


316/535

Dr.PVSNPavanKumar

Stee s eetpi esArchweb iles

Shallowarch

piles

.

To resist large bending moments archweb and Zpiles are used.

When bending moments are less, shallowarch piles with smaller section moduli

can be used.


317/535

Ballandsocket type of joints offer less driving resistance than the thumbandfinger jointsDr.PVSNPavanKumar

Steelsheetpilewalls

a an soc e

interlock


318/535

HookandgripsheetinterlockDr.PVSNPavanKumar

Steelsheetpilewalls

sheet piles. They have several advantages over

.Lighter in section

hard or rocky materialCan be used several times

Can be used either below or above water and

possess longer life. Suitable joints which do not deform during driving

can be provided to have a continuous wall.


319/535

boltingDr.PVSNPavanKumar

Canti evers eetpi ewa

eetp es xe at ottoman

freetorotateattoparecalled

cantileversheetpiles.

Acquiresstabilitydueto

embedmentintothesoilbelowthe

.

Thesepilesareeconomicalonlyformoderatewallheights,sincethe

requiredsectionmodulusincreasesrapidlywithanincreaseinwall

hei ht asthebendin momentincreases.

Lateraldeflectionofthistypeofwallisbecauseofthecantilever

action,willberelativelylarge.


320/535

, . ., ,

shouldbecontrolledsincestabilityofthewalldependsonthepassive

pressureinfrontofthewall. Dr.PVSNPavanKumar


321/535

Dr.PVSNPavanKumar

Sheetpilestructures

held in place by anchors

attached with anchor rods

buried in the backfill at a

considerable distance.

Used for dock and harbor

.

Use of an anchor rod tends

Anchoredsheetpilewallto reduce the lateral

deflection, the bending


322/535

moment and the depth of thepenetration of the pile. Dr.PVSNPavanKumar

Freecantileversheetpilewall

Pp Pa b

Pa Pp

c

de=k D

Sheetpile

subjectedto Activeand assive

ap

K=kpka


323/535

P pressureson

sheetpileNet

pressure

Dr.PVSNPavanKumar


b

c

de


324/535

NetpressureNetpressuresimplified

Areabcef iscommon

Dr.PVSNPavanKumar


=0H

,

fromtwoequilibriumequations

0211 2 =+ hDkDkP

Determineh

c

=asea ouomen s

1

)( 2

++

D

DkDHP

d

ef0

32

2

1=

hhDk


325/535

Substitutehinaboveeqn.Dr.PVSNPavanKumar


0322

14 =+++ CDCDCD


326/535

Dr.PVSNPavanKumar

FreecantileversheetpilewallBendingmomentismaximumatpointfat

k

PxxkP

2

2

1 2 ==

f

x

3

61)( xkxHPmomentBendingMaximum +=

b

c

de


327/535

Dr.PVSNPavanKumar

CantileversheetpilewallsinsandysoilWatertableisatgreatdepth

Pa1

Pp1

EF

Pp2Pa2

ee p e wa


328/535

ee p ewa

supportingsandy

soil

pressureson

sheetpileNet

pressure

AreaGOEFiscommonDr.PVSNPavanKumar


pa=kaH

E

EFpp = 0 p= p


329/535

Netpressure

pp 0 p p

AreaGOEFiscommon

Dr.PVSNPavanKumar


1)Atpoint,OPassivepressure=

Activepressure

Determiney0

Pay

2)0=H

11J

PaareaofFig.BAOJ

22 00 =++ pp ppa

ExpresshintermsofD0

3) 0= pileofbaseaboutMoment

32

1)( 0000 ++

DDDkDyPa


330/535

03

)(21 =+ hhpp pp

Substituteh obtainedinstep2instep3.DetermineD0,depthofembedment,D=D0+y0Dr.PVSNPavanKumar



331/535

Dr.PVSNPavanKumar


Equationissolvedbytrailand

error.Obtaineddepth,Dmaybe

increasedby20to40%.

MaximumBendingMoment

MaxB.Moccursatapointof

zeroshearatdepthx,below

.

P

xxkP

a

a

21 2

==

31)( kxxyPa +

Maximumbendingmoment=Mmax


332/535

bfMmaxSectionModulus,Zs= fb=allowableflexuralstressofsheetpile

Dr.PVSNPavanKumar


Fourthorderdegreeequation

isquitelaborious.Passiveearthpressure, is

replacedbyconcentratedforce

R.


333/535

Actualpressurediagram AssumedsimplifiedDr.PVSNPavanKumar


Takingmomentofforcesabout

baseofsheetpilewall,

where

substituteandresultingeqn.is


334/535

Assumedsimplified

SolveforDandincreaseby20%Dr.PVSNPavanKumar

Cantileversheetpilewallsinsandysoil

Watertableisatshallowdepth

11 hkp a=

21 hkhkp baaa +=

y0 isdepthbelowdredge

eve w erene pressure=

0Dkp pp =B

Dkhhkp bpp ++= )( 21J

Pa

areaofFig.BAJO

PointofapplicationofPay

Take 0=H


335/535

Dr.PVSNPavanKumar

CantileversheetpilewallsinsandysoilWatertableisatshallowdepth

Passivepressure atpointo


336/535

bendingmomentiscalculated.DepthDcomputedshouldbeincreasedby20to40percent.Dr.PVSNPavanKumar

FreeStandingCantileverSheetPileWall

Penetratin

Cla

uqcp 24 == uqcp 24 ==

quunconfinedcompressivestrength

0=H

1

042

2 =+ qqP uu

shearzeroofpotoDepthq

Pint

2==


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Dr.PVSNPavanKumar

FreeStandingCantileverSheetPileWall

Penetratin

Cla


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Dr.PVSNPavanKumar

CantileverwallsincohesivesoilActiveearth ressure,

paatadepthzis

aaa kczkp 2=

Passivepressure,ppat

adepthyis

app

kczkp 2+=

Activeearth ressure

actingtoleftatdepthHis

aaa kcHkp 2=

ua

a

qHp

cHp

=

==

2,0

f


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qu=UnconfinedcompressivestrengthDr.PVSNPavanKumar

Cantileverwallsincohesivesoil

Pass vepressureact ng

towardsrightsideatdredge

level

up qcp ==2

atdredgelevel

HqqHqq uuun == 2)(

Netpressuretowardsrightat

dredgelevelatdepthy

)2)((2 cyHcyppq apn ++==

= un

P i


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Pressureremainsconstant

atalldepthDr.PVSNPavanKumar


onbackfillsidetowardsright

Atbottomofwall

cDHpp 2++=

=a

un qHcHp 24 +=+=

=0H

12

uua

au PDHqh )2(

=

u


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Dr.PVSNPavanKumar


Forequ r um,moments

aboutbaseshouldbezero

D

03

42

1

2

=

++

hhq

qy

u

ua

Substitutinghinaboveequation


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Dr.PVSNPavanKumar


equationisincreasedby20

to40%

Maximumbendingmoment

occurswithinthedepthDh

.

Let bethedepthbelowdredgelevelwhereshearforce

iszero

P

ypyP a

a == 00 0

p

)( 000maxy

ypyyPM a +=

F rther section mod l s


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Furthersectionmodulus

isdetermined.Dr.PVSNPavanKumar


Backfillis

Sand

with

Water

Table

at

Great

De th

Hkp aa =

dredgelevelNetpressureatbaseofwall

cHcppp ap == )2(2

actingtowardsright

qu =

Thisremainsconstantalong

Netpressureatbaseofwallacting

towardsleft

ap cDcDHppp )2(2)( ++


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u

ap

qHcDcDHppp

2)2(2)(

+=++==

Dr.PVSNPavanKumar


11 hkp a=

21p baaa +=

HqcHcp u == 2)2(2

Hq

cDcDHp

u

+=

++=

2

)2()2(


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Dr.PVSNPavanKumar

Thefigure4belowshowsacantileverwall. 1 , 2 ,=16kN/m3,sat=18kN/m

3 andC=35kN/m2 and= .

pilewall(Nov/Dec2012).

ofthedredgelevelis9m.Thewaterlevelinthebackfillisat2mfromtop.Findthedepthofpenetrationrequiredforafactorofsafetyequalto1.Assumethatabovethewatertable,thesoil

isdry.Theotherpropertiesofsoilare:sat=20kN/m3,Ka=0.33,Kp=3.0,Gs=2.6.(June2010,Set


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Dr.PVSNPavanKumar

Fi 4


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Figure4Dr.PVSNPavanKumar

Acantileversheetpileistobeconstructedto.weightofsandis16kN/m3 andthesaturated

3 .resistanceofsandis32.Thewaterlevelis3mabovethedredgelinecomputethedepthofembedmentofthesheetpile(June2010Set3).

ComputetheembedmentlengthDofthesheet

pilewallinagranularsoiltoretaingranularsoilof6mhighononesidewithunitweightof20 N m an ang eo s earingresistanceo 30 .Watertableisatadepthof3mfromthetopof

.


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Dr.PVSNPavanKumar

7 a) Fig.7 shows a cantilever sheet pile wall penetrating a granular

soil. What is the theoretical depth of embedment?

b) What should be the minimum section modulus of the sheet piles

for the Fig.7 shown below. Assumeall = 172 MN/m2.


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Dr.PVSNPavanKumar

AnchoredSheetpilewall eses ee p esares a e ue opass ve orce

andanchorforce.

Depthofembedmentisless.


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Dr.PVSNPavanKumar

Anchoredsheetpile

changesitscurvatureat

point,I

Freeearthsu ortmethod Fixedearthsupportmethod

FixedendFreeend

Lower end B is simply supported and

soil into which sheet pile is driven

Soil into which sheet pile is driven

exerts a large restraint on lower part of


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soil into which sheet pile is driven

does not produce effective restraint

exerts a large restraint on lower part of

sheet pile causes change of curvatureDr.PVSNPavanKumar

AnchoredSheetpilewall

FreeearthsupportmethodCohesionlesssoil

1) p1=kah

2) Atpoint0pn=0

ka (h+a) k a=0

a

a

kk

hka

=

3) At point A p = k (a+b) k (h+a+b) p = k b


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3)AtpointA,pn kp(a+b) ka(h+a+b)pn kbDr.PVSNPavanKumar


FreeearthsupportmethodCohesionlesssoil

4)H=0,P1 P2 T=0 2

22

1bkP =

5)Momentaboutanchorrod=0

P1(h+aeZ1) P2(h+ae+2b/3)=0x

Fromstep4and5determinedepthof

,

6 Maximumbendingmomentoccursbetweenpoint

Manddredgelevel,whereshearforceiszero

,wherexisdistanceofpointfromtopof02

2

= Txka


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, p pbackfillwhereshearforceiszero

Dr.PVSNPavanKumar


FreeearthsupportmethodCohesivesoil

Atdredgelevel,infrontofsheetpile

pn=pp pa=2c (h 2c)=4c h

At ointA

pn=pp pa=(2c+d)

H=0P1 P2 T=0

Momentaboutanchorrod=0

P1xf P2x(h+d/2e)=0

SolvefordandT


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Dr.PVSNPavanKumar

Tutorial

depth of embedment of

sheet pileshown in Figure.Determ ne orce

in anchor permeter of wall.Assume freeearth support


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Dr.PVSNPavanKumar


Fixedearthsu ortmethod

h

h

Deflectioncurvechangesits

curvatureatpoint,I

d

Fixedend

NetPressure

diagram

D PVSN P K


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Dr.PVSNPavanKumar


Fixedearthsu ortmethod

h h

Equivalent Bending

Net

Pressure

diagram

diagram

L ti f di i l d b t t d f R t i t k

eam

method

Diagram

Dr PVSN Pavan Kumar


357/535

Lowerportionofpressurediagramisreplacedbyconcentratedforce,RkatpointkDr.PVSNPavanKumar


Fixedearthsu ortmethod Exactanalysisofanchoredsheetpilebyfixedearth

.

Equivalentbeammethodisused Sheetpileissimply

Depthofpointofinflexion,i isdeterminedfromfollowingchart.

Dr PVSN Pavan Kumar


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Dr.PVSNPavanKumar


Fixedearthsu ortmethodUpperBeamBI

Determinepressurep atdredge

level

Determineifromchart

Determineapointofzeronet

pressure= =n p a ,

determinea

Determinepressureatpointof

inflexionfromrelation

ForbeamIBtakemomentsabout

reactionRIDr PVSN Pavan Kumar


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Dr.PVSNPavanKumar


Fixedearthsu ortmethodBeam IK

Determine pressure p2 from

p2=(kp ka) (da)

I ,equal and opposite to that acting

on beam BI.

Consider moment of forcesacting on beam IK about k anddetermine da and d.

Determine tension T in anchorby considering equilibrium ofbeam IB.

I= 1

P1total force due to pressure on IBDr. PVSN Pavan Kumar


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1 p Dr.PVSNPavanKumar

Tutorial

Determine the

depth of

the anchored

sheet ile

shown in

Figure. Also

determine

force per meter

.fixed end

conditions.Dr.PVSNPavanKumar


361/535

Anchoragesforbulkheads

knownasdeadmen oranchorsaretiedtosheetpile.

Anchorsoffer assiveresistance.

Waleisabeamplacedatfrontorback

sideofsheetpileattachedtothe

anchoredbeamorblockwithanchor

rod.Dr.PVSNPavanKumar


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Anchoragesforbulkheads

Anchorblocksmaybesupportedbybatteredpiles.Theseareemployedwhenthesoilbelowisfirmat

.

Shortsheetpilesaredriventoformacontinuous

pressureDr.PVSNPavanKumar


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Anc orages or u ea s

Sheetpileistiedtoalargestructure

oca ono anc or

NoresistancefromanchorDr.PVSNPavanKumar


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Locationofanchor

Two sliding wedges interfere with each other.

Efficiency of anchor decreases

Full capacity of anchor will be available

if the active wedge of backfill do not interfere

with passive sliding wedge of anchor.

ea man s ocate e ow ne ae ma ng an

angle with the horizontal.Dr.PVSNPavanKumar


365/535

Capacityof

anchor

Anchornear Anchoratlarge

B>5h,Long

anchor

B5h,Long B


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soil soil soil soil soil

CapacityofanchorTen 1962 avethefollowin e uationsforcalculatin ultimate

resistanceofanchorlocatedatorneargroundsurface.

Assumedthatanchorextendstogroundsurface

B=Lengthofanchor,h=heightofanchor,H=depthofbottomofanchorfromground

Dr.PVSNPavanKumar


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Capacityofanchor a esor eamsw


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Capacityofanchor

surfaceisequaltobearingcapacityoffootingatdepth

Ultimatehorizontalresistanceofanchoris 2

hh +

A . , . , .

=Unitweightofsand

A=Areaofanchorplate=bh,h=heightofplate,b=widthofplate

H=Depthfromgroundsurfacetobottom

=Angleoffrictionofsoil ,

. , . , . plate

Horizontaldisplacement,uatanyloadlevelTis

Dr.PVSNPavanKumar


369/535

BracedCuts

orcons ruc onexcava onsare

necessary.TheseexcavationsSheeting

s a econs ruc e a sa eslopeangleifsufficientspaceis

Wale Struts

ava a e.

Fordeepexcavationsinbuiltup

areasadequatespacemaynot

beavailableandthecostof

earthworkwillbehuge.

Excavationslaterallysupported

arecalledbracedcuts.Dr.PVSNPavanKumar


370/535

Typesofsheetingandbracingsystems

sheeting consisting of

timber planks of about 8

to 10 cm thick are

driven around theboundary of excavation

to some depth below

Soil between the sheeting is excavated. Sheeting is held in place by a system of

excavation.Verticaltimbersheeting

.

Wales are horizontal beams running parallel to the excavation wall. Wales are

supported by horizontal struts extended from side to side of excavation.

known as rakers.

If soil can stand unsupported to a limited depth, sheeting can be installed in open

.

Vertical timber sheeting are economical to a depth of 4 to 6m.

Dr.PVSNPavanKumar


371/535


Inthismethodsteelsheet

pilesaredrivenalongthe

excavation.

Asthesoilisexcavated

andstrutsareinserted.

Walesaremadeofsteel

Steelsheetpiles

Strutsmaybesteelor

timber

sexcava onprocee sano erse o wa es an s ru sare nser e .

Processiscontinuedtillexcavationiscompleted.

Topreventlocalheavessheetpilesaredrivenseveralmetersbelowthe

excavation

Dr.PVSNPavanKumar


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SoldierBeams

Dr.PVSNPavanKumar


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SoldiersbeamsareH

pilesdrivenata

spacingof1.5mto2.5maroundthe

boundar of

excavation.

Asexcavation

procee s or zonta

timber plankscalled

laggingsareplaced

betweensoldier

beams.

SoldierBeams

sexcava ona vanceswa es an s ru sarep ace .

LaggingisproperlywedgedbetweenpileflangesDr.PVSNPavanKumar


374/535


Steps involved in construction of tieback

a Inclined Holes are drilled into soil or rockb) Tensile reinforcement cable, Bar or tendon is inserted in the hole

c) Concrete poured for anchor

d) wall connection made

Tieback

This method does not have struts or inclined rakers and no hindrance to

construction activity inside excavationDr.PVSNPavanKumar


375/535

Slurrywall

Slurry trench or wall is

Trench surrounding an open

of bentonite and water

They are useful in areas where

so t soi is existing at groun

surface with high water table.

Slurry produces a pressure that

counteracts the hydraulic pressure

from surrounding soil that would

inconvenience to construction

process.Slurrywall/trench

Concretewallsareconstructedaroundtheexcavationbyplacing

reinforcementinbentonite andconcreting.Dr.PVSNPavanKumar


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Lateralearthpressureonsheeting

Rankine andcoulombtheory

lateralpressureonsheetpileas

retainingwallsrotatingabout

Sheetingandbracingsystemis

ofwall.

Dr.PVSNPavanKumar


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Lateralearthpressureonsheeting o ow ngapparenteart pressure agramson

sheetingbasedonfieldstudiesispresentedby, .

HomogenoussoilDr.PVSNPavanKumar


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Lateralearthpressureonsheeting,

Equivalentcohesionofsandandclaylayers

'2

Hc usssss

e 2

=

Kslateralearthpressurecoefficient

quuncon ine compressivestrengt

ncoefficientofprogressivefailure

HHH +

Equivalentunitweight,e

He =

Anyofthediagramshownaboveisusedtodetermineearthpressure

Nonuniform

soilDr.PVSNPavanKumar


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Lateralearthpressureonsheeting

Bracedcutpassesthrough

anumberofcla la ers

Equivalentvaluesare

Dr.PVSNPavanKumar


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Designofstruts

trutss ou avem n mumvert ca spac ngo .5m.Dept o

firststrutinclaysoilshouldbebelowthedepthoftensioncrack.

sheetpilesarehingedatstrutlevelexceptattopandbottom.

Spanad

Md=0,DetermineR1H=0,DetermineR2

Spandf

Mf=0,DetermineR2

H=0,DetermineR3

= 2 2 2

Strutload,P1=R1xS,P2=R2xSwhereSishorizontalspacingSuitablesectionsofstrutsaredesignedtocarryloadP1,P2.Dr.PVSNPavanKumar


381/535

Designofwales

Walesarehorizontalbeamspinnedatstrutlevel.

Maximumbendingmomentwilldependonstrut

loadandspan,S. 21SR=

Forsecondwale

8max

2

1max SRM =

Sectionmodulus,z=all

M

max

Sheetpiledesign:Anappropriatesectionis

identifiedforthesheet ilebasedonthe

maximumbendingmomet andallowablebendin stress.

Dr.PVSNPavanKumar


382/535

Otheraspectsofdesignofbracedcuts

Incaseofclaythebottomofthecutmayheave

andisat eofbearin ca acit roblem.

Insandheavingfailuremaynotoccur.Butthereis

levelssurroundingarelarger.

settlementinthesurroundingarea.Thisshould

adopted.

Dr.PVSNPavanKumar


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ASSIGNMENTQUESTIONS1. How do ou desi n the bulkheads b free earth su ort

method?

2. What are the different types of sheetings and bracing

systems for braced cuts and describe them?3. The height of a cantilever sheet pile from the top of the

dredge level is 9m. The water level in the backfill is at

2m from top. Find the depth of penetration required fora ac or o sa e y equa o . ssume a a ove e

water table, the soil is dry. The other properties of soil

sat , a . , p . , s . .4. Discuss the procedure for checking the stability of a

.

5. Discuss various methods for providing anchors for asheet ile wall.

Dr.PVSNPavanKumar


384/535

UnitVII

CaissonsWellFoundations

Dr.PVSNPavanKumar


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Syllabus

Caissonsandwellfoundations:

Wellfoundations

Differentshapesofwellfoundation

Componentsofwellfoundations

Functionsanddesign

Sinkingofwells

LateralstabilitybyTerzaghi analysisDr.PVSNPavanKumar


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Caissonsorwellfoundations

Pier

Well

Dr.PVSNPavanKumar


387/535

Caissonsorwellfoundations

Dr.PVSNPavanKumar


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Bridge

Dr.PVSNPavanKumar


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Bridge

Dr.PVSNPavanKumar


390/535

Bridge

Dr.PVSNPavanKumar


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Bridge

Dr.PVSNPavanKumar


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Bridge

Dr.PVSNPavanKumar


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Bridge

Dr.PVSNPavanKumar


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Bridge

Dr.PVSNPavanKumar


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Cofferdamcofferdamisdefinedasatemporarystructurewhichisconstructedsoas

toremovewateran orsoi romenc ose areaan ma eitpossi eto

carryontheconstructionworkunderreasonablydrycondition.

T esofcofferdam

SinglesheetpilewallcofferdamEarthembankmentcofferdamDr.PVSNPavanKumar


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Embankmenttype

cofferdamfor

construction

ofearthdamDr.PVSNPavanKumar


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Cofferdam

Water

body

Dr.PVSNPavanKumar


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Cofferdam

Dr.PVSNPavanKumar


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CellularCofferdam

Dr.P

advanced foundation engineering (57011)

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