Direct Shear Test

TEST TITLE : DIRECT SHEAR TEST 1.0

OBJECTIVE TO DETERMINE THE PARAMETER OF SHEAR STRENGTH OF SOIL, COHESION, c AND ANGLE OF FRICTION, ø.

2.0

LEARNING OUTCOME At the end of this exe!i"ent, st#dent $!e $%&e to ' • Dete!"ine the she$! st!en(th $!$"ete! of the soi& •

3.0

H$nd&e she$! st!en(th test, di!ect she$! test

THEORY

The (ene!$& !e&$tionshi %et)een "$xi"#" she$!in( !esist$nce, Շf $nd no!"$& st!ess, *n fo! soi&s c$n %e !e!esented %+ the e#$tion $nd -no)n $s Co#&o"%s L$) ' τ   f  

=

c + σ tan φ 

/he!e ' c 0 cohesion, )hich is d#e to inte!n$& fo!ces ho&din( soi& $!tic&es $!tic&es to(ethe! to(ethe! in $ so&id   "$ss 1 0 f!iction, )hich is d#e to the inte!&oc-in( of the $!tic&es $nd the f!iction %et)een the" )hen s#%2ected to no!"$& st!ess

The f!iction co"onents inc!e$se )ith inc!e$sin( no!"$& st!ess %#t the cohesion co"onents !e"$ins const$nt. If the!e is no no!"$& st!ess the f!iction dis$e$!s. This !e&$tionshi sho)n in the (!$h %e&o). This (!$h (ene!$&&+ $!oxi"$tes to $ st!$i(ht &ine, its inc&in$tion to the ho!i3ont$& $xis %ein( e#$& to the $n(&e of she$!in( !esist$nce of the soi&, 1 $nd its inte!cet on the 4e!tic$& 5she$! st!ess6 $xis %ein( the $$!ent cohesion, denoted %+ c.

Fi(#!e 7.7 ' G!$h she$! st!ess 4e!s#s no!"$& st!ess 4.0

TEST EQUIPMENTS 7. She$! %ox c$!!i$(e 8. Lo$din( $d 9. Pe!fo!$ted &$te :. Po!o#s &$te ;. Ret$inin( &$te

Fi(#!e 7.8 ' She$! %ox c$!!i$(e

Fi(#!e 7.9 ' Lo$din( $d, e!fo!$ted &$te, o!o#s &$te $nd !et$inin(

&$te

5.0

PROCEDURES 7. The inte!n$& "e$s#!e"ent is 4e!ified %+ #sin( the 4e!nie! c$&ie!s. The &en(th

of the sides, L $nd the o4e!$&& deth, . The &o$din( +o-e is &$ced on the &o$din( $d $nd the h$n(e! is &ifted c$!ef#&&+ onto the to of the &o$din( +o-e. ?. The co!!ect &o$din( is then $&ied to the h$n(e! $d. @. The sc!e)s c&$"in( the #e! h$&f to the &o)e! h$&f is c$!ef#&&+ !e"o4ed. 7. The test is cond#cted %+ $&+in( ho!i3ont$& she$! &o$d to f$i&#!e. R$te st!$in sho#&d  %e .8""B"in. 77 .Reco!d !e$din(s of ho!i3ont$& $nd fo!ce di$& ($#(es $t !e(#&$! inte!4$&s. 78. Fin$&&+ the test is cond#cted on th!ee identic$& soi& s$"&es #nde! diffe!ent 4e!tic$& co"!essi4e st!sses, 7.>;-(, 8.;-( $nd 9.8;-(. ,.0 RESULT Seci"en No ' 7 Lo$din( ' 7.>;-(

Dis&$ce"ent D$i& G$#(e

L 5""6

; 7 7; 8 8; 9 9; : :; ; ;; = =; > >; ? ?; @ @; 7 7; 77 77; 78 78; 79 79; 7: 7:; 7; 7;; 7=

.7 .8 .9 .: .; .= .> .? .@ 7. 7.7 7.8 7.9 7.: 7.; 7.= 7.> 7.? 7.@ 8. 8.7 8.8 8.9 8.: 8.; 8.= 8.> 8.? 8.@ 9. 9.7 9.8

P!o4in( Rin( D$i& G$#(e 7 @ 79 8 8: 8? 97 9: 9> 9@ :8 :: := :? :@ ;7 ;8 ;: ;; ;; ;= ;> ;? ;? ;@ = = =7 =7 =8 =8 =8

Lo$d, P 5-N6 .8 .7?: .8=; .:? .:@ .;>7 .=98 .=@: .>;; .>@= .?;> .?@? .@9? .@>@ .7 .7: .7=7 .778 .7788 .7788 .77:8 .77=9 .77?9 .77?9 .78: .788: .788: .78:: .78:: .78=; .78=; .78=;

She$! St!ess 5-NB"86

St!$in

.;> ;.7 >.9> 77.99 79.= 7;.?> 7>.;> [email protected]> 8.@> 88.7 89.? 8:.@9 8=.> 8>.8 8>.>> 8?.@ 8@.:> 9.= 97.7> 97.7> 97.>9 98.9 98.?> 98.?> 99.:9 9:. 9:. 9:.;> 9:.;> 9;.79 9;.79 9;.79

.7> .99 .; .=> .?9 .7 .77> .799 .7; .7=> .7?9 .8 .87> .899 .8; .8=> .8?9 .9 .97> .999 .9; .9=> .9?9 .: .:7> .:99 .:; .:=> .:?9 .; .;7> .;99

She$!

St!$in

Seci"en No ' 8 Lo$din( ' 8.;-( Dis&$ce"ent

P!o4in( Rin(

D$i& G$#(e

L 5""6

; 7 7; 8 8; 9 9; : :; ; ;; = =; > >; ? ?; @ @; 7 7; 77 77; 78 78; 79 79; 7: 7:; 7; 7;; 7=

.7 .8 .9 .: .; .= .> .? .@ 7. 7.7 7.8 7.9 7.: 7.; 7.= 7.> 7.? 7.@ 8. 8.7 8.8 8.9 8.: 8.; 8.= 8.> 8.? 8.@ 9. 9.7 9.8

D$i& G$#(e 7? 87 8: 97 9; 9@ :9 := :? ;7 ;9 ;; ;> ;@ =7 =9 =; == =? =@ > >7 >9 >: >; >; >= >> >> >? >? >?

Lo$d, P 5-N6 .9=> .:8? .:@ .=98 .>7: .>@= .?>> .@9? .@>@ .7: .7?7 .7788 .77=9 .78: .78:: .78?; .798= .79:= .79?> .7:? .7:8? .7::? .7:?@ .7;7 .7;9 .7;9 .7;; .7;>7 .7;>7 .7;@7 .7;@7 .7;@7

St!ess 5-NB"86 7.8 77.@ 79.= 7>.;> 7@.?9 88.7 8:.9> 8=.> 8>.8 8?.@ 9.9 97.7> 98.9 99.:9 9:.;> 9;.> 9=.?9 9>.: 9?.;9 [email protected] 9@.=> :.89 :7.9> :7.@9 :8.; :8.; :9.> :9.=9 :9.=9 ::.8 ::.8 ::.8

.7> .99 .; .=> .?9 .7 .77> .799 .7; .7=> .7?9 .8 .87> .899 .8; .8=> .8?9 .9 .97> .999 .9; .9=> .9?9 .: .:7> .:99 .:; .:=> .:?9 .; .;7> .;99

Seci"en No ' 9 Lo$din( ' 9.8;-( Dis&$ce"ent D$i& G$#(e

L 5""6

P!o4in( Rin( D$i&

Lo$d, P

She$! St!ess 5-NB"86

St!$in

; 7 7; 8 8; 9 9; : :; ; ;; = =; > >; ? ?; @ @; 7 7; 77 77; 78 78; 79 79; 7: 7:; 7; 7;; 7= 7=; 7> 7>; 7? 7?; 7@ 7@; 8 8;

.7 .8 .9 .: .; .= .> .? .@ 7. 7.7 7.8 7.9 7.: 7.; 7.= 7.> 7.? 7.@ 8. 8.7 8.8 8.9 8.: 8.; 8.= 8.> 8.? 8.@ 9. 9.7 9.8 9.9 9.: 9.; 9.= 9.> 9.? 9.@ :. :.7

G$#(e

5-N6

 7; 87 8? 9= :: ;7 ;> ;@ =; =@ >8 >= >@ ?7 ?: ?> ?? @ @8 @9 @: @= @? @@ @@ 7 77 78 79 7; 7= 7= 7> 7@ 7@ 77 777 777 778 778

. .9= .:8? .;>7 .>9: .?@? .7: .77=9 .78: .798= .7:? .7:=@ .7;; .7=78 .7=;8 .7>7: .7>>; .7>@; .7?9= .7?>> .7?@> .7@7? .7@;? .7@@@ .88 .88 .8: .8= .8?7 .877 .87:8 .87=8 .87=8 .87?9 .888: .888: .88:: .88=: .88=: .88?; .88?;

. ?.; 77.@ 7;.?> 8.: 8:.@9 8?.@ 98.9 99.:9 9=.?9 [email protected] :.? :9.> ::.>> :;.@ :>.= :@.9 :@.?> ;7. ;8.79 ;8.> ;9.8> ;:.: ;;.;9 ;=.7 ;=.7 ;=.=> ;>.89 ;>.? ;?.9> ;@.; =.> =.> =.=9 =7.>> =7.>> =8.99 =8.@ =8.@ =9.:> =9.:>

.7> .99 .; .=> .?9 .7 .77> .799 .7; .7=> .7?9 .8 .87> .899 .8; .8=> .8?9 .9 .97> .999 .9; .9=> .9?9 .: .:7> .:99 .:; .:=> .:?9 .; .;7> .;99 .;; .;=> .;?9 .= .=7> .=99 .=; .==> .=?9

87

-.0

:.8

778

.88?;

=9.:>

.>

DATA ANALYSIS She$! St!ess 5 8"" di$& ($#(e !e$din( 6 * 0 PBA 0  5 di$& ($#(e x .8:6 B A!e$  St!$in 5 8"" di$& ($#(e !e$din( 6  0 5 ∆ L B L 6 0  5 D$i& G$#(e x .76 B Tot$& Len(th  Ex$"&e c$&c#&$tion to find she$! st!ess $nd st!$in fo! seci"en 7 ' ∆ L

5""6

0 7; x .8 0 .9

Lo$d, P 5-N6 0 79 x .8: 0 .8=; She$! St!ess 5 8"" di$& ($#(e !e$din( 6 ' 0

79 x .8: .= x .=

0

>.9> -NB"

St!$in 5 8"" di$& ($#(e !e$din( 6 ' 0

7; x .8 =

0 .; No!"$& St!ess 5 -NB"6 Seci"en No ' 7 Lo$din(' 7.>; -( No!"$& St!ess

0 0

P

A 7.>; x 7 x @.?7

5.= x .=67 0 :>.=@ -NB" Seci"en No ' 8 Lo$din(' 8.; -( No!"$& St!ess

0

P

A 0 8.; x 7 x @.?7 5.= x .=67 0 =?.79 -NB"

Seci"en No ' 9 Lo$din(' 9.8; -( No!"$& St!ess

Seci"en 7 Lo$din( 7.>;-( '

0

P A 0 9.8; x 7 x @.?7 5.= x .=67 0 ??.;= -NB"

Seci"en 8 Lo$din( 8.;-( '

Seci"en 9 Lo$din( 9.8;-( '

She$! St!en(th F!o" the (!$h, d$t$ o%t$ined ' 1 0 7> , c 0  τ   f  

=

c

+

σ tan φ 

7. * 

0 :>.=@ -NB"8 0   :>.=@ t$n 7>  0 7:.;? -NB"8

8. * 

0 =?.79 -NB"8 0   =?.79 t$n 7>  0 8.?9 -NB"8

9. * 

0 ??.;= -NB"8 0   ??.;= t$n 7>  0 8>.? -NB"8

.0

DISCUSSION

Di!ect she$! test is si"&e $nd f$ste! to oe!$te. As thinne! seci"ens $!e #sed in she$! %ox, the+ f$ci&it$te d!$in$(e of o!e )$te! f!o" $ s$t#!$ted s$"&e in &ess ti"e. This test is $&so #sef#& to st#d+ f!iction %et)een t)o "$te!i$&s one "$te!i$& in &o)e! h$&f of %ox $nd $nothe! "$te!i$& in the #e! h$&f of %ox. Fo! this exe!i"ent )e #se s$nd soi& $s the seci"en. As )e -no), the s$nd soi& does not h$4e $n+ cohesion. The f!iction %et)een s$nd $!tic&e is d#e to s&idin( $nd !o&&in( f!iction $nd inte!&oc-in( $ction. Si(nific$nce $nd A&ic$tions $. Jn&i-e "$te!i$&s &i-e stee&, "ost of the soi&s $!e 4iscoKe&$stic, "e$nin( the f$i&#!es $!e ti"e deend$nt %. Fo! "ost of the (eotechnic$& desi(ns conce!nin( fo#nd$tions, e$!th)o!-s $nd s&oe st$%i&it+ iss#es the soi&s $!e !e#i!ed to withstand shearing stresses $&on(  )ith co"!essi4e st!esses c. She$! st!esses tend to dis&$ce $ $!t of soi& "$ss !e&$ti4e to !est of the soi& "$ss d. Shear strength is the c$$cit+ of the soi& to !esist she$!in( st!esses e. Re&$ti4e s&idin( %et)een soi& $!tic&es is the "$2o! f$cto! cont!i%#tin( to the she$! !esist$nce f. If the no!"$& fo!ces inc!e$se, the n#"%e! of cont$ct oints $&so inc!e$se th#s inc!e$sin( the !esist$nce. (. The !e4e!se "$+ h$en if the no!"$& &o$ds dec!e$se 5)hich is the c$se in excavations6 h. Hence the she$! st!en(th is $ f#nction of no!"$& &o$d, $n(&e of f!iction 5$"o#nt of inte!&oc-in( $"on( the soi& $!tic&es6 $nd cohesion 5int!insic !oe!t+ of c&$+s d#e to )hich the+ st$+ c&ose to e$ch othe! e4en $t 3e!o no!"$& &o$d6.

The $d4$nt$(es of the di!ect she$! test $!e' i. Che$, f$st $nd si"&e K eseci$&&+ fo! s$nds. ii. F$i&#!e occ#!s $&on( $ sin(&e s#!f$ce, )hich $!oxi"$tes o%se!4ed s&is o! she$! t+e f$i&#!es in n$t#!$& soi&s. Dis$d4$nt$(es of the test inc&#de' i. Diffic#&t o! i"ossi%&e to cont!o& d!$in$(e, eseci$&&+ fo! fineK(!$ined soi&s. ii. F$i&#!e &$ne is fo!cedKK"$+ not %e the )e$-est o! "ost c!itic$& &$ne in the fie&d iii. NonK#nifo!" st!ess conditions exist in the seci"en. i4. The !inci$& st!esses !ot$te d#!in( she$!, $nd the !ot$tion c$nnot %e cont!o&&ed. P!inci$& st!esses $!e not di!ect&+ "e$s#!ed. /.0

CONCLUTION

As the conc&#tion, the o%2ecti4e of this exe!i"ent is to dete!"ine the $!$"ete!s th$t in4o&4ed s#ch $s she$! st!en(th of soi&s, cohesion $nd $n(&e of f!iction is $chie4ed. Fo#! (!$h h$s %een &otted $nd the 4$&#e of cohesion $nd $n(&e of f!iction h$d %een o%t$ined. F!o" this exe!i"ent, the 4$&#e of cohesion, c is  -NB" $nd the 4$&#e of $n(&e of f!iction is 7> . 10.0

QUESTIONS

#estion 7 a. Why perforated plate in this test with teeth? The e!fo!$ted &$te in this test )ith teeth %ec$#se %+ the teeth, the exe!i"ent c$n %e !od#ce $ (!i fo!ces %et)een the in4o&4ed &$te $nd the s$nd $nd c$n $ssists in dist!i%#tin( the she$! st!ess. This is $&so to ens#!e the soi& does not s&ide $)$+ f!o" the "et$& &$te. /hen the &o$d is $&ied on the soi&, the e!fo!$ted &$te )i&& (!i the soi& $nd #sh the soi&.

b. What maximum value of displacement before stop the test? The "$xi"#" 4$&#e of dis&$ce"ent %efo!e )e sto the test is )hen the 4$&#es $!e const$nt fo! "o!e th$n th!ee ti"es o! )e c$n sto the test )hen the inc&ine 4$&#e s#dden&+ d!oed. #estion 8

a. What is the purpose of a direct shear test? Which soil properties does it measure? The di!ect she$! test is one of &$%o!$to!+ exe!i"ent $nd no!"$&&+ #sed %+ (eotechnic$& en(inee!s to find $nd c$&c#&$te the she$! st!en(th $!$"ete!s of $n+ soi& th$t in4o&4ed. The di!ect she$! exe!i"ent "e$s#!es the she$! st!en(th $!$"ete!s  )hich inc&#ded the soi& cohesion 5c6 $nd the $n(&e of f!iction 5f!iction $n(&e6. b. Why do we use fixing screw in this test? What will happen if you do not removed them during test?  /e #sed fixin( sc!e) in this di!ect she$! test %ec$#se in o!de! to $4oid she$!x7 fo! h$enin( %efo!e the exe!i"ent is c$!!ied o#t. If )e dont !e"o4e the" d#!in( the test, the f!iction c$n not occ#! $t the sc!e) $nd the!e h$4e )i&& %e no she$! on the s$"&e $nd th#s the !es#&t )i&& %e not $cc#!$te.