TEST TITLE : DIRECT SHEAR TEST TEST TITLE : DIRECT SHEAR TEST 1
1..00 OOBBJJEECCTTIIVVEE
TO DETERMINE THE PARAMETER OF SHEAR STRENGTH OF
TO DETERMINE THE PARAMETER OF SHEAR STRENGTH OF SOIL,SOIL, COHESION, c AND ANGLE OF FRICTION, ø.
COHESION, c AND ANGLE OF FRICTION, ø. 2
2..00 LLEEAARRNNIINNG G OOUUTTCCOOMMEE
At the end of this exe!i"ent, st#dent $!e $%&e to ' At the end of this exe!i"ent, st#dent $!e $%&e to '
•• Dete!"ine the she$! st!en(th $!$"ete! of the Dete!"ine the she$! st!en(th $!$"ete! of the soi&soi& •• H$nd&e she$! st!en(th test, di!ect she$! testH$nd&e she$! st!en(th test, di!ect she$! test
3
3..00 TTHHEEOORRYY
The (ene!$& !e&$tionshi %et)een "$xi"#" she$!in(
The (ene!$& !e&$tionshi %et)een "$xi"#" she$!in( !esist$nce,!esist$nce,ՇՇff $nd no!"$& st!ess, $nd no!"$& st!ess, *
*nnfo! soi&s c$n %e !e!esented %+ the e#$tion $nd -no)n $s Co#&o"%s L$) 'fo! soi&s c$n %e !e!esented %+ the e#$tion $nd -no)n $s Co#&o"%s L$) '
φ φ σ σ τ τ ==cc++ tantan f f /he!e '
/he!e ' c c 0 cohesion, 0 cohesion, )hich is )hich is d#e to d#e to inte!n$& inte!n$& fo!ces ho&din( fo!ces ho&din( soi& $!tsoi& $!tic&es tic&es to(ethe! ino(ethe! in $ so&id
$ so&id "$ss "$ss
1 0 f!iction, )hich is d#e
1 0 f!iction, )hich is d#e to the inte!&oc-in( of the $!tic&es to the inte!&oc-in( of the $!tic&es $nd the f!iction$nd the f!iction %et)een
%et)een
the" )hen s#%2ected to no!"$& st!ess the" )hen s#%2ected to no!"$& 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 $nd its inte!cet on the 4e!tic$& 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$&ie!s. The &en(th of the
sides, L $nd the o4e!$&& deth, <.
8. The %$se &$te is fixed inside the she$! %ox. Then o!o#s &$te is #t on the %$se
&$te. Next, e!fo!$ted (!id &$te is fitted o4e! o!o#s so th$t the (!id &$tes sho#&d
App!"#$ %& '(p'!)*'+".
9. T)o h$&4es of the she$! %ox is fixed %+ "e$ns of fixin( sc!e)s.
:. Fo! cohesi4e soi&s, the soi& s$"&e is t!$nsfe!!ed f!o" s#$!e seci"en c#tte! to the
she$!%ox %+ !essin( do)n on the to (!id &$te. Fo! s$nd+ soi&, soi& is co"$cted in
&$+e!s to the !e#i!ed densit+ in she$! %ox.
;. The she$! %ox $sse"%&+ is "o#nted on the &o$din( f!$"e. =. The di$& is set of the !o4in( !in( to 3e!o.
>. 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
Seci"en No ' 7 Lo$din( ' 7.>;-(
Dis&$ce"ent P!o4in( Rin( She$! St!ess 5-NB"86
St!$in D$i& G$#(e L 5""6 D$i&
G$#(e Lo$d, P 5-N6 ; .7 7 .8 .;> .7> 7 .8 @ .7?: ;.7 .99 7; .9 79 .8=; >.9> .; 8 .: 8 .:? 77.99 .=> 8; .; 8: .:@ 79.= .?9 9 .= 8? .;>7 7;.?> .7 9; .> 97 .=98 7>.;> .77> : .? 9: .=@: [email protected]> .799 :; .@ 9> .>;; 8.@> .7; ; 7. 9@ .>@= 88.7 .7=> ;; 7.7 :8 .?;> 89.? .7?9 = 7.8 :: .?@? 8:.@9 .8 =; 7.9 := .@9? 8=.> .87> > 7.: :? .@>@ 8>.8 .899 >; 7.; :@ .7 8>.>> .8; ? 7.= ;7 .7: 8?.@ .8=> ?; 7.> ;8 .7=7 8@.:> .8?9 @ 7.? ;: .778 9.= .9 @; 7.@ ;; .7788 97.7> .97> 7 8. ;; .7788 97.7> .999 7; 8.7 ;= .77:8 97.>9 .9; 77 8.8 ;> .77=9 98.9 .9=> 77; 8.9 ;? .77?9 98.?> .9?9 78 8.: ;? .77?9 98.?> .: 78; 8.; ;@ .78: 99.:9 .:7> 79 8.= = .788: 9:. .:99 79; 8.> = .788: 9:. .:; 7: 8.? =7 .78:: 9:.;> .:=> 7:; 8.@ =7 .78:: 9:.;> .:?9 7; 9. =8 .78=; 9;.79 .; 7;; 9.7 =8 .78=; 9;.79 .;7> 7= 9.8 =8 .78=; 9;.79 .;99 Seci"en No ' 8 Lo$din( ' 8.;-(
St!ess 5-NB"86 D$i& G$#(e L 5""6 D$i&
G$#(e Lo$d, P 5-N6 ; .7 7? .9=> 7.8 .7> 7 .8 87 .:8? 77.@ .99 7; .9 8: .:@ 79.= .; 8 .: 97 .=98 7>.;> .=> 8; .; 9; .>7: 7@.?9 .?9 9 .= 9@ .>@= 88.7 .7 9; .> :9 .?>> 8:.9> .77> : .? := .@9? 8=.> .799 :; .@ :? .@>@ 8>.8 .7; ; 7. ;7 .7: 8?.@ .7=> ;; 7.7 ;9 .7?7 9.9 .7?9 = 7.8 ;; .7788 97.7> .8 =; 7.9 ;> .77=9 98.9 .87> > 7.: ;@ .78: 99.:9 .899 >; 7.; =7 .78:: 9:.;> .8; ? 7.= =9 .78?; 9;.> .8=> ?; 7.> =; .798= 9=.?9 .8?9 @ 7.? == .79:= 9>.: .9 @; 7.@ =? .79?> 9?.;9 .97> 7 8. =@ .7:? [email protected] .999 7; 8.7 > .7:8? 9@.=> .9; 77 8.8 >7 .7::? :.89 .9=> 77; 8.9 >9 .7:?@ :7.9> .9?9 78 8.: >: .7;7 :7.@9 .: 78; 8.; >; .7;9 :8.; .:7> 79 8.= >; .7;9 :8.; .:99 79; 8.> >= .7;; :9.> .:; 7: 8.? >> .7;>7 :9.=9 .:=> 7:; 8.@ >> .7;>7 :9.=9 .:?9 7; 9. >? .7;@7 ::.8 .; 7;; 9.7 >? .7;@7 ::.8 .;7> 7= 9.8 >? .7;@7 ::.8 .;99 Seci"en No ' 9 Lo$din( ' 9.8;-(
Dis&$ce"ent P!o4in( Rin( She$! St!ess 5-NB"86
St!$in D$i& G$#(e L 5""6 D$i& Lo$d, P
G$#(e 5-N6 ; .7 . . .7> 7 .8 7; .9= ?.; .99 7; .9 87 .:8? 77.@ .; 8 .: 8? .;>7 7;.?> .=> 8; .; 9= .>9: 8.: .?9 9 .= :: .?@? 8:.@9 .7 9; .> ;7 .7: 8?.@ .77> : .? ;> .77=9 98.9 .799 :; .@ ;@ .78: 99.:9 .7; ; 7. =; .798= 9=.?9 .7=> ;; 7.7 =@ .7:? [email protected] .7?9 = 7.8 >8 .7:=@ :.? .8 =; 7.9 >= .7;; :9.> .87> > 7.: >@ .7=78 ::.>> .899 >; 7.; ?7 .7=;8 :;.@ .8; ? 7.= ?: .7>7: :>.= .8=> ?; 7.> ?> .7>>; :@.9 .8?9 @ 7.? ?? .7>@; :@.?> .9 @; 7.@ @ .7?9= ;7. .97> 7 8. @8 .7?>> ;8.79 .999 7; 8.7 @9 .7?@> ;8.> .9; 77 8.8 @: .7@7? ;9.8> .9=> 77; 8.9 @= .7@;? ;:.: .9?9 78 8.: @? .7@@@ ;;.;9 .: 78; 8.; @@ .88 ;=.7 .:7> 79 8.= @@ .88 ;=.7 .:99 79; 8.> 7 .8: ;=.=> .:; 7: 8.? 77 .8= ;>.89 .:=> 7:; 8.@ 78 .8?7 ;>.? .:?9 7; 9. 79 .877 ;?.9> .; 7;; 9.7 7; .87:8 ;@.; .;7> 7= 9.8 7= .87=8 =.> .;99 7=; 9.9 7= .87=8 =.> .;; 7> 9.: 7> .87?9 =.=9 .;=> 7>; 9.; 7@ .888: =7.>> .;?9 7? 9.= 7@ .888: =7.>> .= 7?; 9.> 77 .88:: =8.99 .=7> 7@ 9.? 777 .88=: =8.@ .=99 7@; 9.@ 777 .88=: =8.@ .=; 8 :. 778 .88?; =9.:> .==> 8; :.7 778 .88?; =9.:> .=?9
87 :.8 778 .88?; =9.:> .>
-.0 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! seci"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 Seci"en No ' 7 Lo$din(' 7.>; -( No!"$& St!ess 0 P A 0 7.>; x 7 x @.?7
5.= x .=67 0 :>.=@ -NB" Seci"en No ' 8 Lo$din(' 8.; -( No!"$& St!ess 0 P A 0 8.; x 7 x @.?7 5.= x .=67 0 =?.79 -NB" Seci"en No ' 9 Lo$din(' 9.8; -( No!"$& St!ess 0 P A 0 9.8; x 7 x @.?7 5.= x .=67 0 ??.;= -NB" Seci"en 7 Lo$din( 7.>;-( '
Seci"en 8 Lo$din( 8.;-( '
Seci"en 9 Lo$din( 9.8;-( '
She$! St!en(th
F!o" the (!$h, d$t$ o%t$ined ' 1 0 7> , c 0
φ σ
τ =c + tan
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 oe!$te. As thinne! seci"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 exe!i"ent )e #se s$nd soi& $s the seci"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 deend$nt
%. Fo! "ost of the (eotechnic$& desi(ns conce!nin( fo#nd$tions, e$!th)o!-s $nd s&oe 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 $nd cohesion 5int!insic !oe!t+ of c&$+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 $nd si"&e K eseci$&&+ fo! s$nds.
ii. F$i&#!e occ#!s $&on( $ sin(&e s#!f$ce, )hich $!oxi"$tes o%se!4ed s&is 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$(e, eseci$&&+ fo! fineK(!$ined soi&s.
ii. F$i&#!e &$ne is fo!cedKK"$+ not %e the )e$-est o! "ost c!itic$& &$ne in the fie&d iii. NonK#nifo!" st!ess conditions exist in the seci"en.
i4. The !inci$& 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 exe!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$ined. F!o" this exe!i"ent, the 4$&#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 exe!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$&#e s#dden&+ d!oed.
a. What is the purpose of a direct shear test? Which soil properties does it measure? The di!ect she$! test is one of &$%o!$to!+ exe!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$! exe!i"ent "e$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$enin( %efo!e the exe!i"ent is c$!!ied o#t. If )e dont !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.
