chapter 2-soil strength behaviour part 1

8/9/2019 Chapter 2-Soil Strength Behaviour Part 1

http://slidepdf.com/reader/full/chapter-2-soil-strength-behaviour-part-1 1/34

G G G G 2

SOIL STRENGTHBEHAVIOUR

HAPTER 2 :



LEARNING OUTCOME

At the end of the lecture, student should e !le tounderst!nd"

• Conce#t of tot!l !nd e$ect%&e stresses, #ore#ressure !nd e'cess #ore #ressure

• Conce#t of fr%ct%on (odel !nd so%l she!r stren)th*Mohr+Coulo( f!%lure theor, she!r stren)th

#!r!(eters

• -eter(%n!t%on of she!r stren)th #!r!(eters ofso%ls . she!r o' !nd tr%!'%!l test



EAM3LES O4 4AILURE O4 SHEARSTRENGTH



C!(eron H%)hl!nd



3ul!u 3%n!n)



Ger%5 + Len))on)



6!l!n Tun5u



3res%nt 9, 4!s! II, 3utr!8!!


http://slidepdf.com/reader/full/chapter-2-soil-strength-behaviour-part-1 12/34Precint 9, Putrajaya 2009

TANAH RUNTUH JENIS CETEK

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SHEAR STRENGTH

• She!r stren)th 1%th%n ! so%l (!ss %sdue to the de&elo#(ent of fr%ct%on!lres%st!nce et1een !d8!cent#!rt%cles

• The force tr!ns(%tted et1een t1ood%es %n st!t%c cont!ct c!n eresol&ed %nto t1o co(#onents"! nor(!l co(#onent N,#er#end%cul!r to RS, !nd !t!n)ent%!l or she!r co(#onent T,#!r!llel to %t

• The so%l )r!%ns sl%de o&er e!ch other!lon) the f!%lure surf!ce* There %sno crush%n) of %nd%&%du!l )r!%ns*

T

N

N

T

R

S



WHY SHEAR STRENGTH?

• $i#s genera##& ai# in sear HEAR*A+,-

RE

At f!%lure, she!r stress !lon) the f!%lure surf!ce re!ches the she!r

stren)th*



SHEAR STRENGTH O4 SOIL



MOHR COULOMB

• The strengt en.e#$/es %s ! )r!#h%c!lre#resent!t%on of ! #!rt%cul!r l%(%t%n) cond%t%on ofshe!r stress@nor(!l stress r!t%o

• The f!%lure en&elo#e %s 5no1n !s the $r1C$u#$mb ai#ure en.e#$/e

• The f!%lure en&elo#e %s ! cur&ed l%ne

• 4or (ost so%l (ech!n%cs #role(s, %t %s suc%entto !##ro'%(!te the she!r stress on the f!%lure

#l!ne !s ! l%ne!r funct%on of the nor(!l stress• The l%ne!r funct%on %s 5no1n !s C$u#$mbs ,a%



MOHR COULOMB 4AILURE CRITERION



MOHR COULOMB

4 5 c 7 tan

•1heref + the she!r stren)th of the so%l

c . the cohes%on of the so%l 1h%ch re#resents the !ttr!ct%onforces et1een the #!rt%cles

σ . the nor(!l stress !##l%ed to the so%l

φ . the !n)le of %ntern!l fr%ct%on of the so%l



MOHR COULOMB

• In saturate' s$i#, the tot!l nor(!l stress !t !#o%nt %s the su( of the e$ect%&e stress, σ !nd#ore 1!ter #ressure, u

σ = σ ’ + u

• The Mohr-Coulomb failure criterion,expressed in terms of eective stress, σ will be

as follows

4 5 c 7 tan



COHESION >C?

(a) Cohesionless Soil (c = 0) (b) Pure cohesie soil (φ D =? (c) Cohesie!"ric#ional soil (c!φ)

c for s!nd !nd %nor)!n%c s%lt %s =

c for nor(!ll consol%d!ted cl!sc!n e !##ro'%(!ted !t =

c for o&erconsol%d!ted cl!s !re)re!ter th!n =



INTERNAL ANGLE O4 4RICTION

• T#%c!l &!lues of %ntern!l !n)le of fr%ct%on, φ !re)%&en %n t!le elo1 "



ANAL<SES O4 STRESS USING MOHRSCIRCLE

• Mohr c%rcle of stress #ro&%des ! con&en%ent (ethod of!n!l%n) t1o+d%(ens%on!l stress st!tes

• As st!ted Mohr+coulo( f!%lure cr%ter%on, f!%lure fro(she!r 1%ll occur 1hen the she!r stress on ! #l!ne

re!ches ! &!lue )%&en the coulo( l!1 >f ?

4%)ure ;" Incl%n!t%on of f!%lure #l!ne %n

so%l 1%th (!8or #r%nc%#!l #l!ne

Nor(!l stress %nduced!re σ

!nd σ

',1here σ

F σ'* So th%s h!&e

c!use she!r τ.



ANAL<SES O4 STRESS USING MOHRSCIRCLE

4%)ure 2" Mohrsc%rcle !nd f!%lureen&elo#e

• σ$% = &a'or rincial s#ress• σ$ = &inor rincial s#ress• The "ailure lane E* &a+es an an,le

- .i#h #he &a'or rincial lane

• To /e#er&ine #he an,le - an/ #herela#ionshi be#.een &a'or an/&inor rincial s#ress re"er *i,ure 1

• *,h is #he "ailure eneloe /e"ine b2#he coulo&b la. rela#ionshi

• 3# can be sho.n #ha# ba/ = 1- = 405 φ, or

D J φ@2



SHEAR STRENGTH TEST

• She!r Bo' Test

• Tr%!'%!l Test

• UnconKned Co(#ress%on Test

• V!ne She!r Test

chapter 2-soil strength behaviour part 1

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