unconsolidated undrained

TITLE: Unconsolidated Undrained Triaxial Test

OBJECTIVE

To determine the shear strength parameters for clayey soil.

THEORETICAL BACKGROUND 

Triaxial test is more reliable because we can measure both drained and undrained



shear strength. Generally 1.4” diameter (3” tall or !."” diameter (#” tall specimen is used. $pecimen is encased by a thin rubber membrane and set into a plastic cylindrical



chamber. ' 

σ 3



%ell pressure is applied in the chamber (which represent



fluid (generally water. 'ertical stress is increased by loading loading the specimen specimen (by raising the platen platen in strain

 by pressuri&ing the cell

cont contro rolle lled d test test and and by addi adding ng load load direc directly tly in stress stress cont contro roll lled ed test test but but strain strain controlled test is more common until shear failure occurs. Total )ertical stress which ' 

is

σ 1

' 

 is e*ual to the sum σ d

σ 3

 and de)iator stress (

σ d

.



+easu +easurem remen entt of (



changed are recorded. ,epending on the nature of loading and drainage condition triaxial tests are conducted

 axia axiall defo deform rmati ation on pore pore pres pressu sure re and and sampl samplee )olu )olume me

in three different ways. UU Triaxial test • %U Triaxial test • %, Triaxial test •



UU test measures the undrained shear strength of soils by means of axial compression test on cylindrical specimens in which no drainage is permitted during the test.

APPARATUS a) b) c) d) e) f) g

$train controlled triaxial load frame Triaxial cell assembly %ell pressure supply panel $cale -alance sensiti)e .1 g +oisture cans /)en

PROCEDURE

1. !. 3. 4.

The diameter diameter length length and initial initial mass mass of the the specimen specimen measured. measured. The The thic0ne thic0ness ss of the the rubber rubber memb membran ranee measure measured. d. $oil $oil specim specimen en is set set in a triax triaxial ial chamb chamber er.. The cell cell pressure pressure increased increased to a desired desired )alue )alue ( 02a 02a for the the first case and and 14 02a 02a in the second case. . The specimen specimen sheared sheared at at the rate of of 15min 15min or .5min .5min (for  mm sample sample height. height. 6n automated de)ice the software calculates it automatically based on the soil type. #. The ∆7  and

σ d

 recorded in e)ery 1 seconds (computer does it automatically.

. The test test continued continued until until the de)iator de)iator stress stress shows shows ultimate ultimate )alue or or ! axial axial strain. strain. ". 8fter 8fter the test complet complete e the cell pressure pressure release release to  the pressur pressuree )ent and the cell  bring down by bring the the lower platen down the cell drained and the porous stone clean and assembly. 9. The The mode mode of of failu failure re then then s0etch s0etch.. 1. The weight of specimen measured again and the the specimen put into the o)en. 11. 11. The weight weight measured again after !4 hour. hour. 1!. The test repeated using second second specimen(14 specimen(14 02a of cell pressure and third specimen specimen !1 02a of cell pressure.

USER’S GUIDELINE FOR THE ELE TRIAXIAL DEVICE UU TRIAXIAL TEST) A! PO"ER AND #AIN SUPPL$ SUPPL$ SETTINGS  T%&' '(e &' a*+ead, d-.e) 1. 2ress the :2ower :2ower ,isplay” ,isplay” power power button button to the :/;” :/;” position. position. 8fter 8fter $tabili&atio $tabili&ation n (approx. 1 min. push the :Tare” button to &ero the display. !. Turn Turn on the laboratory laboratory )acuum )acuum supply supply.. The The associated associated amount amount of )acuum a)ailable a)ailable to your system will be displayed on the :'acuum :'acuum $upply Gauge”. 3. Turn Turn on the laborato laboratory ry compressed compressed air supply supply.. 'iewi 'iewing ng the :2ress :2ressure ure $upply” $upply” gauge ad8iri :,e>8iring ng ?ate ?aterr %ontrol” %ontrol” )al)e )al)e to he :@ill” :@ill” position. position. !. ?hen ?hen the tan0 tan0 water water le)e le)ell is about about 1” from from top top turn turn the :,e>8i :,e>8irin ring g ?ater  ter  %ontrol” )al)e to the ::)ent” )ent” position ( 'ery 'ery $lowly to allow water to drain.

C! DE6AIRING THE "A "ATER TANK TANK T%&' '(e '(e &' a*+ead, d-.e) 1. Turn Turn the :,e>8iring :,e>8iring ?ate ?aterr %ontrol” %ontrol” )al)e to the :'a :'acuum” position position.. !. 8pply )acuum form 1>1 1>1 minutes minutes and and at the same same time gently gently sha0e sha0e the tan0  tan0 

/cciasionally to enhance the remo)al or air from water. 3. Turn Turn the :,e>8iri :,e>8iring ng ?ate ?aterr %ontrol” %ontrol” )al)e )al)e to the )ent )ent position. position.

D! FILLING THE BURETTE BURETTE CHANNELS CHANNELS  T%&' '(e '(e a*+ead, a*+ead, d-.e)! d-.e)! 1. $et all all fi)e )al)es )al)es on the test test cell to he closed position. position. !. $et the :,e>8iri :,e>8iring ng ?ater ?ater %ontrol %ontrol”” )al)e to the :2ressure” :2ressure” position position.. 3. $et the :-urette5 :-urette58nnul 8nnulus us 6nput 6nput %ontrol” %ontrol” )al)e )al)e to the :)ent” :)ent” position position.. 4. $et the the :8nnulus :8nnulus %ontrol %ontrol $witch” $witch” to the :open” :open” position position (;ormal (;ormal. . . $lowly turn the the :-urette58nn :-urette58nnulus ulus 6nput 6nput %ontrol %ontrol”” )al)e to the the :@ill” :@ill” position. position. ?hen ?hen the the wate waterr reach reaches es the the desir desired ed le)el le)el turn turn the the :-ur :-uret ette5 te58n 8nnu nulu luss @low @low %ontrol” )al)e to the :%ell /perate” position. ,o not o)erfill. ?ater should not be allowed to flow into the cell pressure tube at the top. #. =epe =epeat at the abo) abo)ee step stepss unti untill two two buret burette te channe channels ls being being used used are fiile fiiled d to the desired le)el.

 ;ote A 6f the water le)el in the :,e>8ired ?a ?ater ter Tan0 $ystem” drops to about 1” from the bottom repeat the filling and de>airing procedures described abo)e. E! DE6AIRING DE6AIRING THE THE BURETTE BURETTE CHANNELS CHANNELS T%&' T%&' &' a*+ead, a*+ead, d-.e)! d-.e)! 1. $et the :-urette :-urette58n 58nnul nulus us 6nput 6nput %ontrol” %ontrol” )al)e )al)e for each channel channel to the :)acuu :)acuum” m”  position. Under normal operating conditions the de>airing process should be complete in about >1 minutes. minutes. !. 8fter completio completion n set all :6nput :6nput %ontrol” %ontrol” )al)es )al)es bac0 bac0 to the the :)ent” positio position. n.

F! PREPAR PREPARAT ATION ION OF THE SA#PLE SA#PLE 1. Trim Trim the the sample sample to be be tested tested using using a +ite +iterr -ox. -ox. !. +easu +easure re the height height and diamet diameter er of the the sampl samplee at )ariou )ariouss locat locatio ion n to get an a)erage )alue. 3. +easure the weight of the the trimmed trimmed sample before before test. 4. ?r ?rap ap the sample sample in in a plastic plastic sheeting sheeting to to pre)ent pre)ent any moisture moisture loss. loss. . Use trimmings trimmings to to get the the moisture moisture content content of of the sample sample before before test.

G! PREPARA PREPARATION TION FOR THE TRIAXIAL LOADING 1. ,ouble ,ouble clic0 clic0 on on software software icon :,$” on the des0top des0top.. !. %lic0 %lic0 on on the the butto button n :;ew :;ew Te Test”. 3. $elect : UU1 BTriaxi BTriaxial al Cuic0 Cuic0 undraine undrained d Test> Test>8$”. 8$”. 4. %lic0 %lic0 on the the butto button n : $elect $elect a +achine +achine for for the test”. test”.

. @ill in the the spaces in this this window window and clic0 on the button button :o0” :o0” to the right right sight sight of  the screen. The fields mar0ed D by their side can not be left blan0 and characters 5D.AEFH can not be used while filling up the spaces. #. 6n the window window :Test :Test in 2rogress” 2rogress” ma0e ma0e sure that that you select select the test test that you you want to run and then clic0 on the button :o0” at the bottom of the screen. . $witch on the the 7oad %ell machine machine using using the the button button at the the bac0. bac0.

H! #ONIT #ONITOR ORING ING THE THE TEST TEST 1. 6n the :Test :Test +onitor +onitoring” ing” window window ma0e sure sure that all the the test data shown shown in the upper upper box is correct. !. %lic0 on on the button button :$tart :$tart Test Test $tage” $tage” located located to the upper upper right right side of the screen. screen. 3. 6n the next next window select select :Test :Test 6nitiali& 6nitiali&ation ation”” and clic0 on on button :/I” :/I” in the bottom. bottom. 4. 6n the :Test :Test 6nitiali&ation 6nitiali&ation”” window window enter the the pre)iously pre)iously measured measured sample sample ,iameter ,iameter ?eight and Jeight. . The bul0 bul0 density density of the sample sample will be be calculated calculated automa automatically tically by the software software.. #. The informatio information n regarding regarding the +embrane +embrane Thic0nes Thic0nesss and Ko Koungs +odulus +odulus are default default )alue and may not be changed unless using a different 0ind of membrane around the sample. . 8fter enterin entering g all data data clic0 clic0 on the the green green button button :%onfir :%onfirm m $etup ,ata”. ". This will will bring bring you you bac0 to to the :Te :Test st +onitoring +onitoring ?indow” ?indow”.. 9. 8gain clic0 clic0 on button button ”$tart ”$tart Test Test $tage” located located to the the upper right right side of the the screen. screen. 1. This time select :%ompression” from the menu and and then clic0 on button :/I” at the  bottom of the window. window.

I!

CO#PR O#PRES ESSI SION ON ST STA AGE

@rom the pre)ious stage you will be directed to the screen titled :%ompression $tage for Undrained Test”. 6.

'ent %ell %ell 2ressu 2ressure re Trans Transduc ducer er to 8tmosp 8tmospher heree and and =esetA =esetA a $et the the :-urette58n :-urette58nnulus nulus 6nput 6nput %ontrol” %ontrol” )al)e )al)e to the the :2ressure” :2ressure” 2osition 2osition..  b $et the :8nnulus %ontrol $witch” )al)e to the :on” position. position. c $et the :-uret :-urette58nn te58nnulus ulus @low @low %ontrol” %ontrol” )al)e )al)e to the :%ell /perate” /perate” positio position. n. d +a0e sure sure all the cell pressur pressuree transducer transducer is open open to atmosphere atmosphere and wait wait for 1 seconds seconds e 6n the ,$> ,$> software software window window clic0 clic0 on the red red button button :=eset :=eset %ell 2ressur 2ressure”. e”.

66.

@ill and 2ressurise the %ell. $elect +aterial Type Type and 2ress -utton to %alculate $uggested =ate of $train on Lnter ,irectlyA a %lose %lose the the )al)e )al)e on on the the test test :+ar0e :+ar0ed d %2”. %2”.  b %arefully place the sample on the Triaxial Triaxial cell base pedestal. c 2lace the the top pressure pressure pad pad and use blac0 blac0 />rings />rings to secure secure the the membrane membrane around around the base base  pedestal and top pressure pad. d 2lace the Triaxial Triaxial cell cell co)er o)er o)er the sample sample and use the the three rods rods to secure it in place. place.

e

f g h i

  software window to get the accurate reading. $et the :-urette58nnulus 6nput %ontrol” )al)e )al)e to :2ressure” position. $lowly open open the )al)e )al)e on the test test cell mar0ed mar0ed :%2”. This This will transfer transfer the cell cell pressure pressure to the water inside the glass cylinder. 6n the ,$> ,$> software software window window select the the right right :+aterial :+aterial Ty Type” to the the right side side of the the window and clic0 on the button :calculate =ate of $train”. 6nput the :%alculated rate of of displacement” )alue )alue from the the computer screen screen to display window at the bottom of the test cell and press Lnter .

666.

%alculate 7ogger $ampling =ates (based on percentage of length of specimen at failureA a /n the ,$> software window window fill up the boxes boxes mar0ed :first :first increments” :upto” :upto” and :second increments”. This is the increment at which the result will be captured by the transducer. The The default )alues are from the 8$T+ $tandard. $et both for .1.

6'. 6'.

=eset @orce Transducer M -ring 2iston  software to . lbf 

'.

=eset 8xial ,isplacement M $tart %ompression at Lnd of %ount ,ownA a 2lace the :axial :axial displaceme displacement nt transducer” transducer” bottom bottom touching touching the the hori&ontal hori&ontal rod and and clic0 on on the button :=eset 8xial ,isplacement Transducer” on the ,$> software window.  b This should reset lower left window on the :Test :Test +onitoring” window of the the ,$> software to . inches.

'6. '66. '66.

%lic0 %lic0 on the the green green :con :continu tinue” e” butto button n at the the bottom bottom of of the page page of of the soft softwar waree window window.. 8 wind window ow will will appear appear that that will will instr instruct uct you you to press press enter enter (Gree (Green n -utton -utton to start start the the Test Test %ountdown. 6f e)erything is ready clic0 on the green button : $ tart Test Test %ountdown”. /nce /nce the two two whistl whistles es go go press press the gree green n button button :=un” :=un” on the the 0eypad 0eypad at at the bott bottom om of the the test test cell.

'666. '666.

J! TO STO STOP P TH THE E TES TEST T 1. To stop the loading loading at any any time press press red button button :$top” :$top” on the 0eypad 0eypad of the load load frame. frame. !. 6n the ,$> softwar software e on :Test :Test +onitor +onitoring” ing” window window clic0 on on button :Lnd :Lnd Test Test stage” stage”

3. %lic0 %lic0 on button button :$ta :$tart rt Tes Testt $tage” $tage” butto button. n. 4. $elect $elect :@in :@inal al +easu +easurem rement ents” s” and and clic0 clic0 on on /I  . Lnter Lnter all para paramet meters ers that that are are a)ailab a)ailable le at this this time time @inal $pecimen weight (wet @inal $pecimen ?e ?eight ight (,ry 6nitial +oisture %ontent from Trimmings 7ab Temperature Temperature during test #. .

". 9.

2article $pecific Gra)ity %lic0 on green button :%onfirm ,ata”. %lic0 :/I” on the window stating :@6;87 $T8GL $T8GL 6$ ;/? %/+27LTL. 2=L$$ /I / I T/ $T/=L TJL TL$T ,8T , 8T8 8 =L8,K @/= 8;87K$6$ 8;87K$6$ /= 2=L$$$ %8;%L7 T/ 2L=@=/+ @U=TJL= $T8GL$” $a)e the =aw data obtained from the test to a directory of your choice. The software will prompt to a default directory. %lic0 on button :exit” to exit from the software.

K! DRAINI DRAINING NG TH THE E CELL CELL 1. Turn Turn the :$et 2ressure 2ressure %ontrol” %ontrol” 0nob 0nob in counter>c counter>cloc0w loc0wise ise direction direction to reduce reduce the cell pressure. !. Turn Turn the :-urette58n :-urette58nnulus nulus 6nput 6nput %ontrol” %ontrol” )al)e )al)e to :-ridge :-ridge /ff” position position.. 3. /pen the the top 0nob of the glass cylinder cylinder in the load cell cell assembly. assembly. 4. $et the the :-urette58n :-urette58nnulu nuluss @low %ontrol” %ontrol” to :drain” :drain” position. position. . /pen the the )al)e on on the test mar0ed mar0ed :%2 :%2. This will will drain the water water from the glass glass cylinder.

L! DIS#A DIS#ANTL NTLING ING TH THE E CELL CELL 1. Use the button button O on the 0eypad 0eypad of of the load frame to lower lower the sample sample away away from the load piston. !. Unscrew Unscrew the three three rods rods from the the sides sides of the the glass cylinder cylinder and ta0e ta0e out the the cylinder. 3. ,ismantle ,ismantle the sample sample from the the test cell cell and secure secure the membrane membrane top top and bottom bottom end plates.

DATA Sample Data: Diameter, Do = 33.35 mm 3 = 62.02 cm Water content, w = 61.0 $oa% rate cm2

= 13.7

= 12.7 mm&min

Volume, Vo

De!ree o" #aturation, #

Area, Ao

= '.735

$en!t(, $ o = )' -a

= 70.) mm

$oa% $o a% rin! rin! con# con#ta tant nt,, $* $*

*cl e

#t

1

2n%

3r%

t(

$oa % %ial unit #

*ell pre##ure, +3

= 5.6 5.6' ' /&% /&%i i

De"or m, %ial 0.01 unit#  0

4$ m m

Sam ple loa%, /

0.00

0

0.000

25

0.25

3

0.017

50

0.50

9

0.051

75

0.75

16

0.091

85

0.85

17

0.097

78

0.78

0

0.000

100

1.00

17

0.097

125

1.25

26

0.148

150

1.50

29

0.165

175

1.75

32

0.182

200

2.00

34

0.193

177

1.77

0

0.000

180

1.80

10

0.057

540

5.40

0

0.000

550

5.50

15

0.085

650

6.50

46

0.261

750

7.50

55

0.312

 4$&$

1 

o

0.00 00 0.00 35 0.00 71 0.01 05 0.01 20 0.01 10 0.01 41 0.01 76 0.02 12 0.02 47 0.02 82 0.02 50 0.02 56 0.07 62 0.07 76 0.09 17 0.10

1.00 00 0.99 65 0.99 29 0.98 95 0.98 80 0.98 90 0.98 59 0.98 24 0.97 88 0.97 53 0.97 18 0.97 50 0.97 44 0.92 38 0.92 24 0.90 83 0.89

*orr Area A1 cm2 

8.73 5 8.76 6 8.79 7 8.82 8 8.84 1 8.73 5 8.86 0 8.89 1 8.92 4 8.95 6 8.98 8 8.95 9 8.96 4 9.45 6 9.47 0 9.61 7 9.76

Deiat or #tre## 4+1=-& A1 -a 0.00

/orm al #tre# # 4+1&+

19.39

0.198

57.97

0.592

103.08

1.052

109.72

1.120

0.00

0.000

109.48

1.117

166.46

1.699

184.89

1.890

203.22

2.074

214.73

2.191

0.00

0.000

63.59

0.649

0.00

0.000

89.76

0.916

271.39

2.770

319.38

3.259

3

0.000

1200 1300 20

1418

12.0 0 13.0 0 -

66

0.375

67

0.381

-

-

58 0.16 93 0.18 34 -

42 0.83 07 0.81 66 -

9 10.5 2 10.7 0 -

356.46

3.637

350.47

3.576

-

-

Maximum deviator stress (from stress-strain curve !" 1

# 360 $%a

Maximum va&ue of vertica& stress

# 458 $%a

"1#"3 ' !"1

D8S*9SS8/

n t)is ex*eriment+ t)ere are 4 c,c&es done on t)e same sam*&e+ )ic) is t)e &ue c&a, co)esive soi&. n t)eor,+ t)e sam*&e i&& fai& eit)er at t)e maximum deviator stress va&ue or at 20/ of t)e axia& strain. n t)is ex*eriment+ t)e soi& sam*&e fai&s fu&&, at t)e 4t) c,c&e+ it) t)e va&ue of deviator stress at 350.47 $%a and at a strain of 0.1834. ince t)is test on&, use one va&ue of ce&& *ressure " 3+ )ic) is at 98 $%a+ $%a+ on&, one Mo)rs circ&e can e *&otted at t)e ra*) of s)ear strent)  aainst norma& stress ". )e va&ues of " 1 can e otained from t)e stressstrain curve and in t)is ex*eriment+ e )ave ta$en t)e va&ue of !" 1 from t)e maximum deviator stress at t)e 4 t) c,c&e+ )ic) is )ere t)e soi& sam*&e fai&s. ext+ to et t)e va&ue of " 1+ e )ave used t)e formu&a "1#"3 ' !"1 and e )ave determined t)e va&ue of " 1 as 458 $%a. Mean)i&e+ t)e va&ue of "3 is ta$en direct&, from t)e ce&& *ressure+ )ic) is at 98$%a.  )e )orionta& va&ue of of t)e ra*) is determined determined as 180 $%a+ $%a+ and t)is va&ue indicates t)e u+ s)ear strent) of t)e soi& sam*&e. oever+ some *recautions a&so s)ou&d e ta$en to ma$e sure to increased t)e *roai&it, t)at our rou* can et t)e exact va&ues and avoided more an errors suc) as t)e e,es must e *er*endicu&ar to t)e readin+ do not exceeded 150 *si (1034 :%a+ and t)ere are a numer of ma;or error sources in t)is ex*eriment - in fact t)is ex*eriment uses some instrumentation )ic) is not )i)&, accurate and t)at ), sometimes t)e dinis)in t)e ex*eriment and ca&cu&ations+ e can conc&ude t)at from t)e ex*eriment+ t)e o;ective are ac)ieved )ic) is to determine t)e s)ear strent) of t)e sam*&e.

;fee+ )a*ter 2 (oi& trent) trent) @e)aviour @e)aviour ote+ ?acu&t, of ivi& Anineerin+ BiM :ota amara)an. 2. @ud)u+ @ud)u+ M. oi& oi& Mec)anics Mec)anics and and ?oundat ?oundations ions 3rd Adition.+ Co)n Di&e, E ons+ nc.+ 2011. 3. ir Amam =$ Faud+ oi& oi& Mec)anics Gaorator, Manua&+ ?acu&t, ?acu&t, of ivi& Anineerin+ BiM :o :ota ta amara)an. 4. BB riaxi riaxia& a& est+ est+ )tt*HIIfacu&t,.fu&&erton.eduItiariIeo )tt*HIIfacu&t,.fu&&erton.eduItiariIeotec)JGaImain*aeJ>&esIo tec)JGaImain*aeJ>&esIot)erI t)erI BB. Ketrieved on 8t) Marc) 2015. 5. Bnconso& Bnconso&idated idated Bndrain Bndrained ed est+ est+ )tt*HII.uta.eduIceIeotec)I&aI )tt*HII.uta.eduIceIeotec)I&aIMainIoi&/20GaI10JBB MainIoi&/20GaI10JBB /20testIBB.*df. Ketrieved on 8 t) Marc) 2015.