INTRODUCTION: A tri-axial test is a common method to measure the mechanical properties of many deformable solids, especially soil and rock, and other granular materials or powders. There are several variations on the test. In a tri-axial shear test, stress is applied to a sample of the material being tested in a way which results in stresses along one axis being dierent from the stresses in perpendicular directions. This is typically achieved by placing the sample between two parallels platens which apply stress in one usually vertical! direction, and applying "uid pressure to the specimen to apply stress in the perpendicular directions. In an unconsolidated undrained test undrained test the load are applied #uickly, and the sample is not allowed to consolidate during test. The sample is compressed at a constant rate strain-controlled!.
OBJECTIVE:
To determined the shear strength parameter of soil which are angle
) of soil with shape of internal friction ( ϕ ) and cohesion ( ∁ changes of cohesive soil.
APPLICABLE STANDARD:
D2850 - 03a $tandard Test %ethod for &nconsolidated-&ndrained Triaxial 'ompression Test on 'ohesive $oils.
PURPOSE OF MEASUREMENT: &ndrained triaxial shear test is one of the indirectly shear test that carried out by imposing a cell pressure to the cylindrical shape soil sample and then increasing the axial load that resulting the shear failure that happen to the soil sample. (hen the test is conducted, maintain the undrained conditions without allowing any pore water dissipation. At least three samples are needed. %ake sure all sample will be imposed with dierent cell pressure and imposed by axial pressure until the entire sample is fail. )rom the value of axial pressure at failure and cell pressure for every sample, %ohr circle can be drawn and the value of
) and angle of internal friction ( ϕ ) cohesion ( ∁
Graph 9.1 Mohr Circle
can be determined.
APPARATUS: $ampling tubes
*ubber liming+membranes
%embrane stretcher
*ubber binder
Tri axial cell+chamber
PROCEDURE: . Three cylinder shaped soil samples, measuring mm long and /0 mm in diameter are prepared. 1. The samples are inserted into a rubber membrane and sealed on the top and bottom part using 2-ring to prevent penetration of water into the samples. /. A soil sample that is wrapped in rubber membrane is placed into the tri axle cell. %ake sure that the sample is standing upright and steady on the centre of compression plate. 3. (ater is inserted into the tri axle cell through intake valve until the whole cell is 4lled with water. Air outlet valve is opened to release the trapped air. 5. All the valves on the tri axle is closed and sample is imposed by 56 k7+m1 of cell pressure. . The reading on the deformation dail gauge and load dial gauge are set to 8ero. The test is started with loading rate of .51 mm+min. Axial load is added onto the sample until it fails. At the same time, the proving ring reading that represents the axial load is recorded for every 16x6.6 mm standard dial reading that gives the value of vertical transparency. . *ecord gauge readings for every 6, 16, 36, 6, 06 and so on until one of the following instances occur. i. *eduction of load gauge reading is clearly seen. ii. 7ext three reading of load gauge is constants. iii. $hift more than 169 strain. . The form of the fail soil sample is sketched and moisture content for every tested sample is determined. 0. The same procedure as the above is repeated for the other samples for cell pressure 66 k7+m1 and 166 k7+m1. :. The used proving ring number is noted and calibration data is obtained. $tress and strain calculated for each reading. A graph of stress versus strain is plotted and maximum shear strength of each sample is shown. %ohr circle is drawn to determine cohesion '! and friction angle ;!.
DATA/RESULT: Sample ! (eight < /.03 g =imension > =iameter < /.0 cm ?eight < .1 cm @uas penampang < ./:53 cm Tegangan sel < 6.5 kg+cm Balibrasi Alat Terhadap @oad < 6.:00 kg+mm
T"me "# M"#$% e 6 1 3 0 6 1 3 0 16 11
De&'(ma %"'# O# D"al
S%(a"# Ra%e) *+
6.6666 .5136 /.6306 3.516 .6:6 .166 :.336 6.06 1.:16 /.6 5.1366 .36
6 1 3 0 6 1 3 0 16 11
C'((e,% eA(ea), m.+ .36 ./3 .0 1.1: 1./:1 1.0 1.:5 /.15 /.5/ /.:63 3.15 3.
D"al Rea-" #
L'a)+
112 )P/A+ )/,m.+
6.6 5.6 :.6 11.6 13.6 15.6 15.5 1.6 1.1 1.1 1.1 1.1
6.6666 1.:01 /.3 /.:53 3./ 3.3:6 3.506 3.5: 3.1: 3.1: 3.0 3.0
6.6666 6.1/: 6.100 6./1/ 6./303 6./556 6./53 6./510 6./31 6.//:6 6.//35 6./1
Sample 2! (eight < /5.0 g =imension > =iameter < /.0 cm ?eight <.1 cm @uas penampang < ./:53 cm Tegangan sel < .6 kg+cm Balibrasi Alat Terhadap Ceban < 6.0/03 kg+mm
Cell )13+ )/,m .+ 6.5 6.5 6.5 6.5 6.5 6.5 6.5 6.5 6.5 6.5 6.5 6.5
T"me "# M"#$% e 6 1 3 0 6 1 3 0 16 11
De&'(ma %"'# O# D"al
S%(a"# Ra%e) *+
6.6666 .5136 /.6306 3.516 .6:6 .166 :.336 6.06 1.:16 /.6 5.1366 .36
6 1 3 0 6 1 3 0 16 11
C'((e,% eA(ea), m.+ .36 ./3 .0 1.1: 1./:1 1.0 1.:5 /.15 /.5/ /.:63 3.15 3.
D"al Rea-" #
L'a)+
112 )P/A+ )/,m.+
6.6 0.6 15.6 1:.6 /1.6 /3.6 /.6 /0.6 36.6 3.6 3.6 3.6
6.6666 /./60 3.5:3 5./1: 5.00 .130 .1 .:0/0 ./53 .5/5 .5/5 .5/5
6.6666 6.1033 6./0: 6.3/:3 6.33 6.3:// 6.56 6.510 6.53 6.5316 6.510 6.555
D"al Rea-" #
L'a)+
112 )P/A+ )/,m.+
6.6 11.6 /1.5 /0.6 31.6 31.5 30.6 56.6 51.6 5/.6 5/.6
6.6666 /.:5: 5.0/5 .05 .5:63 .060 0.30 :.6/1 :./: :.503 :.503
6.6666 6./30 6.3:3 6.51 6.15 6.6/ 6.: 6.0 6.:13 6.00: 6.1
Cell )13+ )/,m .+ .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6 .6
Sample 3! (eight < /.03 g =imension > =iameter < /.0 cm ?eight < .1 cm @uas penampang < ./:53 cm Tegangan $el < .5 kg+cm² Balibrasi Alat Terhadap Ceban < 6.0613 kg+mm
T"me "# M"#$% e 6 1 3 0 6 1 3 0 16
De&'(ma %"'# O# D"al
S%(a"# Ra%e) *+
6.6666 .5136 /.6306 3.516 .6:6 .166 :.336 6.06 1.:16 /.6 5.1366
6 1 3 0 6 1 3 0 16
C'((e,% eA(ea), m.+ .36 ./3 .0 1.1: 1./:1 1.0 1.:5 /.15 /.5/ /.:63 3.15
Cell )13+ )/,m .+ .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5
11
.36
11
3.
53.5
:.03:5
6./:
.5
DISCUSSION: . The advantage and disadvantage of Tri-axial test Advantage> • • •
• •
Accuracy of the test results is mostly reliable. Dxact 4eld conditions of the soil can be simulated in a tri-axial shear test. 'ontrolling factors are many and reliable. As clinger valves are used for drainage, volume change and pore pressure measurement is possible. 7o leaking is possible. A perfect undrained test can be successfully performed. *esult obtained from the tri-axial shear test is reliable and highly accurate. =isadvantage>
• •
• • •
7ot as easy implement as the direct shear test. %ore complicated in every respect and the one has to be very conscientious in strictly observing the steps given in the earlier test procedure. %ore complicated and time consuming test. @eak proo4ng the whole system is diEcult. *am friction cannot be totally avoided.
1. =etermined the two types of analysis from this test. Drror Analysis An error with the actual machine could have occurred thus giving inade#uate readings, that is, the machine calibration error. The recording of the actual readings. 'alculation error. %iss-interpretation of the results The test could have failed from the start Fraph Analysis
=eviator stress against strain is calculated. The data is then used to plot the curve of deviator stress against strain.
CONCLUSION: In the tri axial test this, ideally mohr circle produced a collapse of the hori8ontal or f < 6 the result of experiment is not the case!. This happens because the water content in the samples was not 669, so that the sample is not fully saturated specimens still exist that cause friction between soil particles. Apart from that, the oense or careless in carrying out tests, in which the probability of occurrence of this error is spread because of increased water "ow in and out of the specimen.
REFERENCE: • • •
•
•
@ab sheet '/66/, GBA,H%&, 166: @ab sheet '366/, GBA,H%&, 166: =as, C.%. ,Fundamental Geotechnical Engineering, Crooks+'ole Thomson @earning, ::: ?uat, C.C.B Ali, ). %aail, $.,Kejuruteraan Geoteknik , Henerbit &niversiti Hutra %alaysia, 1661 *amamurthy, T.7 $itharam, T.F., Geotechnical Engineering 1665 ,
