liquifaction due to earthquake

8/18/2019 liquifaction due to earthquake

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“ Towards Global Technological Excellence”

“LIQUEFACTION EFFECT ON SHALLOW FOUNDATION DUE TOEARTHQUAKES”

SEMINAR ON

By

PANKAJ B. DHAWALE

(I.D. 14056004)

Guide

Dr. A. I. DHATRAK

DEPARTMENT OF CIVIL ENGINEERING

GOVT. COLLEGE OF ENGG.AMRAVATI

NOVEMBER 2014


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Contents

Introduction

Ground failure from soil liquefaction

Counter measures against liquefaction

Criteria for liquefaction potential mapCase Study

Analysis with liquefaction

ResultsConclusions

References

2


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Intro!"#t$on

Liquefaction is an earthquake-related haard that

causes unsta!le land and poses risks to !uilding

infrastructure"

Liquefaction is more likely to occur in loose to

moderately saturated granular soil with poor

drainage# such as silty sand or sand and gra$els"

Liquefaction is a phenomenon in which the

strength and stiffness of a soil is reduced !y

earthquake shaking or other rapid loading" 3


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Construction of shallow foundation upon theliquefia!le soil is possi!le when a sufficient thick

non-liquefia!le soil crust !etween the foundation

and liquefia!le soil# e%ists"

&he effect of liquefaction on !uilt en$ironment

can !e e%tremely damaging" Buildings whose

foundation directly !ear on sand which liquefieswill e%perience a sudden loss of support# which

will result in drastic and irregular settlement of

the !uilding causing structural damage"


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5

In%&"en#e o% so$& #on!$t$ons on

&$'"e%#t$on otent$&


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Cont#t %or#es $n so$&

Soil !efore liquefaction

Soil after liquefaction

6


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Sand !oils'ailure of retaining wall

Ground settlement

'low failure of slopeBuoyant rise

Loss of Bearing capacity

Ground oscillation

7

*ro"n! %$&"re %ro+ so$& &$'"e%#t$on


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Ground failures associated with the phenomena ofliquefaction under cyclic loading can !e classified in a

!roader sense as (

,&o- %$&"res-It is o!ser$ed when the liquefaction ofloose# contracti$e soils results in $ery large

deformations"

De%or+t$on %$&"res-It is o!ser$ed when there is a

gain in shear resistance of the liquefied soil at larger

strain"


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t$ons %or &$'"e%#t$on +$t$/t$on

Strengthen structure to resist predicted groundmo$ement"

Select appropriate foundation type and depth

including foundation modification of e%isting

structure" Sta!ilie soil to eliminate the potential for

liquefaction or to control its effect"


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Prere %or &$'"e%#t$on

)ossi!le to identify areas potentially su!*ect toliquefaction with haard one map"

+se of haard map !y pu!lic and pri$ate owners

the seriousness of e%pected damage and most

$ulnera!le structure"

+sing this map# local go$ernment coulddesignate liquefaction potential areas"


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Cr$ter$ %or &$'"e%#t$on otent$&

+

Liquefaction potential map compiled !y superimposinga liquefaction suscepti!ility map and liquefaction

opportunity map"

Area known to ha$e e%perienced liquefaction

during historic earthquake"

Area containing liquefaction suscepti!le material

that are saturated# nearly saturated or e%pected to !ecome saturated"


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Continued,

Area ha$ing sufficient e%isting geotechnical dataindicating the soil are potentially liquefia!le"

Area underlain with saturated geologicallyyoung sediments"


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Cse st"!

iigata earthquake# .apan /01234


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5ino-6wari earthquake# .apan/07104


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An&s$s -$t so$& &$'"e%#t$on

Singh 5" and 5aheshwari B" 8"/9:0;4 has done the analysis(

a4


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foot is calculated at characteristic point"

here#

= thickness of non-liquefia!le layer


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+ltimate degraded !earing capacity of strip footing is gi$en !y#

/qu

4deg

= ϒ 0

/f

DE4q9

D:"F ϒ 9

B9

ϒ D/ ϒ

0

E9B4/0D9'

E48 S

H

tan0- ϒ 0E

Bearing capacity degradation factor is determined from euation(

'Sdeg =/qu4degqu

ynamic settlement is calculated from equation#

Sdyn

here#

c = coefficient /:"::7 to :":;F4

ama% = peak ground acceleration

& = predominant e%citation time period

= num!er of cycle corresponding to )GA"


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Coe%%$#$ent o% P"n#$n/ 2er Res$stn#e "n!er

3ert$#& Lo!


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Ks depend on approximate bearingcapacity ratio which is determined by,

q2/q1 !ϒ 2 "ϒ 2/ ϒ 1 "ϒ 1#

where,

ϒ 1 $nit weight o% non&'iq$e(ed sand

ϒ 2 $nit weight o% 'iq$e(ed sand

"ϒ 1 )*+* %actor o% non&'iq$e(ed sand'ayer

"ϒ 2 )*+* %actor o% 'iq$e(ed sand 'ayer


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Cse 1 A ,oot$n/ Rest$n/ on L$'"e%$e! 2n! Ler

qu = 09F k)a & = :"9F sec

ama%= :"9 ms9


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+nder the 'ree 'ield#


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Cse ,oot$n/ Rest$n/ on Non&$'"e%$&e 2n!

Ler o7er&$n/ L$'"e%$&e 2n! Ler

qu = 09F k)a

& = :"9F sec

ama%= 9 ms9


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)arameter Kaluesc= EDB 7 m

Muff 22 k)a

Mufoot 77 k)a

ϒ ff = Muff ?$@ 2271=:"N3

ϒ foot :"30

ϒ u =

/ϒ ff Dϒ foot49

:"FNF

qult 932";F km9

'Sdeg 0"1N

Sdyn 00"FN mm


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Res"&t

'rom analysis# it can !e o!ser$ed# that the presence of non-

liquefia!le sand layer increases the !earing capacity and

drastically decrease the dynamic settlement"

Ber$n/ C#$t

(8N9+

)

,#tor o% 2%et 2ett&e+ent

W$to"t 2n!

Ler7N"FF :"N: 30"FF cm

W$t 2n! Ler 932";F 0"1N 00"FN mm

Per#ent/e

$n#reses (:)23"32 23"32 -

Per#ent/e

re!"#t$on (:) - - 1N"99


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Con#&"s$on

on-liquefia!le soil crust presence pro$ed to !e

e%tremely !eneficial to the o$erall foundation

performance"

As the dynamic settlements drastically decrease

and the !earing capacity similarly increases forincreasing shear strength and thickness of the

soil crust"

&he footing and free field settlement continued

for a significant period of time after the end of

the seismic loading"


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Continued,

&he presence of non-liquefia!le sand layer

a!o$e liquefia!le sand layer may drastically

reduce the liquefaction induced settlement and

increase the !earing capacity" &his will

strengthen shallow foundation# e$en without the

need for any prior soil impro$ement of the

underlying liquefia!le sand layer"


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References(04 5arques A" S" )" S"# Coelho )" A" L" '"# Cilingir +"# Eaigh S" 8" and

5ada!hushi G" /9:094" O


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F4 Bayat


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2

Thank You

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liquifaction due to earthquake