Triaxial Test, Stress and Strain Controlled, UU, CU, CD triaxial test Advantages and Disadvantages of Stress and Strain Controlled test, Servo controlled test, True triaxial test, NR Patra term paper work, IIT Kanpur Coursework Paper

1. TRIAXIAL TEST
(STRESS CONTROLLED – STRAIN CONTROLLED)
Course: GEOTECHNICAL MEASUREMENT AND EXPLORATION
CIVIL ENGINEERING DEPARTMENT
IIT KANPUR (INDIA)
TERM PAPER PRESENTATION
BY
SUVRA SAMAL
Prof. SAMIRSINH P PARMAR
1

2. OUTLINE OF PRESENTATION
 INTRODUCTION: TRIAXIAL TEST
 REVIEW
 DETAIL TRIAXIAL TEST
 RESULT ANALYSIS OF TRIAXIAL TEST
 STRESS- STRAIN CONTROL TEST
 COMMENT ON STRESS- STRAIN CONTROL
TEST
 ADVANCEMENT IN TRIAXIAL TEST
 REFERANCES
2

3. SHEAR STRENGTH OF SOIL
Determination of soil strength parameters ( c and f ) in the lab
1- Direct Shear Test
2- Unconfined Compression Test
3- Triaxial Compression Test
To determine the shear strength of soil Mohr-Coulomb Yield Criterion is used
t = c + sn tan f
Soil Cohesion
Angle of Friction
Where : c & Ø are shear
strength parameters
3

4. STATE OF STRESS IN TRIAXIAL TEST
Pore Water
Pressure u
σc
σc
q
q
σc
σc
σa = q +σc = σ1
Specimen
Length L
Specimen
Area A
ε = Axial Strain = ΔL/L
σ1 = Major Principle Stress
= Axial Stress σa
σ3 = Minor Principle Stress
= Radial Stress σr
q= Deviator stress = F/A
= Axial Load/ Area
σr = σc =σ3 σ‘1 = Major Principle
Effective Stress
= σ1-u
σ‘3= Minor Principle
Effective stress
= σ3-u 4

5. BRIEF REVIEW
Year Authors Title of Paper/ Research
1924 Buisman and
Hveem
Initial Triaxial device was invented
1930 Cassagrande,
Karl Terzaghi
The first device that was similar to modern
equipment was developed
1957 Bishop and
Henkel
designed new test technique for Triaxial test
1962 Bishop and
Henkel
published first book on Triaxial testing named,
“The measurement of soil properties in the
Triaxial test”.
1971 Seed and Silver performed strain controlled test at very small
strains
1975 Kovari V. and
Tisa A.
described multiple failure state and strain
controlled triaxial test
5

6. BRIEF REVIEW
Year Authors Title of Paper/ Research
1975 Bishop and
Welsley
carry out plane strain tests , true triaxial load.
1981 Deveaux D. ,
Vuez A.,
Amoros D.
developed technology for stress and strain controlled
automatic parameter acquisition system for Triaxial
test.
1988 Carrol, W.F developed fast Triaxial test device. performed
nonlinear wave analysis to study the stress and
strain rate effects on the results of soil parameters.
1988 Akitoshi M.
Masato M.
and Shinichi
T.
developed independent principle stress control
apparatus
1997 Claudio D.
and Silvia I.
performed experimental analysis and theoretical
interpretation of Triaxial load controlled loose sand
specimen collapse. 6

7. Example applications of triaxial test:
Stability of shallow foundation or
excavation in soft clay Cyclic loading of gravity base structure
Effect of shallow gas
on cyclic behaviour of
dense sand
7

8. CONVENTIONAL TRIAXIAL TEST EQUIPMENT
Conventional Triaxial Equipment (After K H Head, 1986)
8

9. Ref: Department of Construction Engineering Advanced Geotechnical Laboratory
Chaoyang University of Technology
MERCURY CONTROL
DEVICE
9

10. Triaxial Compression Test
1- Unconsolidated Undrained Test (UU)
Step 1 Step 2
sn
t
cu
t= c
s2 s1
s2 s1
s2 s1
s1 - s2
s1 - s2
s2 s2
s2
s2
Confining
Pressure
s1 = Ds + s2
s2
Ds
Ds
s2
s2
e
Ds
s2
Ds Failure
Deviator Stress
1. Consolidation
Valve Closed
2. Shearing
Valve Closed
10

11. Step 1 Step 2
Triaxial Compression Test
2- Consolidated Undrained Test (CU)
fu
sn
t
cu
e
Ds
s2
Ds Failure
s2
s1
s2 s1
s2 s1
s1 - s2
s1 - s2
s2
s2
s2 s2
s2 s2
s2 s2
s2
s2
Confining
Pressure
Ds
Ds
Ds
s1 = Ds + s2
Deviator Stress
s2
s2
1. Consolidation
Valve Open
2. Shearing
Valve Closed 11

12. Step 1 Step 2
Triaxial Compression Test
3- Consolidated Drained Test (CD)
fd
sn
t
cd
s2
s1
s2 s1
s2 s1
s1 - s2
s1 - s2
s2 s2
s2
s2
Confining
Pressure
s1 = Ds + s2
s2
Ds
Ds
s2
s2
e
Ds
s2
Ds Failure
Deviator Stress
2. Shearing
Valve Open
1. Consolidation
Valve Open
12

13. RATE OF STRAIN AND DRAINAGE CONDITION IN
TYPES OF TRIAXIAL TESTS
Test Rate of axial strain Drainage condition
UU Fastest. failure occur within 20 to
25 minutes
Drainage valves are closed
CU Slow enough to adequate
equalisation of excess pore water
pressure
Drainage valves are closed and
excess pore water pressure
measured
CD Slow enough to result in negligible
pore pressure variation
Drainage valves are opened and
ΔV measured
13

14. STRESS CONTROLLED TRIAXIAL TEST
 In this type of test axial stress is increased by pre-
decided increments and the vertical deformation of the
sample measured.
 Stress controlled tests were carried out by imposing
finite load increments.
 The load increments are followed by time periods at
constant stress level.
 The Stress-controlled test at the stress level
characterized by a mobilized friction angle suffers a
sudden collapse.
14

15. STRAIN CONTROLLED TRIAXIAL TEST
 Soil specimen sheared at a uniform strain rate.
 Shear force acting on soil specimen measured
using proving ring.
 The stress vs. strain curve observed after the peak
point.
 Continuous stress vs. strain curve available so at
every corresponding value of strain, stress is
available and vice a versa.
15

16. GRAPHICAL REPRESENTATION OF STRESS- CONTROLLED VS.
STRAIN CONTROLLED TRIAXIAL TEST
Strain ε
Stress
σ
Strain Controlled Test
Stress Controlled Test
Stress increased from
one stage to another
Continuous behavior of
stress vs. strain observed
Failure Point
ε1 ε2
σ1
σ2
Stress increased from σ1 to σ2 and in
between the failure occurs then the
corresponding value of strain at failure (εf)
not available in stress controlled test
εf
16

17. COMMENT OF STRESS CONTROLLED TRIAXIAL
TEST
 Peak shear resistance can be only approximated
because failure occurs at a stress level somewhere
between the pre failure load increment and the failure
load increment
 (i.e. the failure load may be in between the two stages
of load increment and exact failure load may be
approximated)
 Only the peak shear resistance can be observed and
plotted.
 Simulated field conditions like…
 Foundations, stage wise construction of structure on
soil etc.
17

18. COMMENT OF STRESS CONTROLLED TRIAXIAL
TEST
 Stress controlled test are preferred for conducting
shear test at very slow rate.
 Why?
 Because applied load can easily be kept constant
for any given period of time.
18

19. COMMENT OF STRAIN CONTROLLED TRIAXIAL
TEST
 Most widely used.
 Focus on interdependence of peak strength and
loading history.
 Advantage:
 Peak shear resistance (at failure) as well as lesser
shear resistance (residual stress – ultimate
strength) can be observed and plotted.
 Simulates field Conditions like…
 Embankment, retaining wall, slope stability etc.
19

20. ADVANCEMENT IN TRIAXIAL TEST
 Triaxial test options now a days
 Isotropic, anisotropic and Ko-consolidation
 Monotonic and cyclic loading
 Drained and undrained shearing
 Stress-strain-strength properties
 Creep tests
 Special testing programs
 Temperature controlled test
 Frozen triaxial test
 High pressure- high temperature triaxial test
 Large scale triaxial test. 20

21. SOIL PARAMETERS DERIVED FOR RESEARCH OF
FIELD CONDITIONS LIKE…
 Rainfall induced landslide.
 Swelling soil.
 Collapsible soil, and
 Dynamic effect on geotechnical structures.
21

22. CONCLUSION:
 More realistic
 Reasonably accurate results
 Better control over drainage
 Various modifications can be possible to simulate
field conditions.
 Advance instruments are available.
 Ease of Combination with computer software's.
 Use of data loggers, gauges and sensors makes it
fool proof for research, where accuracy is
important.
22

23. REFERENCES
 Bishop, A. W., and D. J. Henkel, “The Measurement of Soil Properties in the Triaxial
Test,” 2d ed., Edward Arnold, London, 1969.
 Kovari,K : “Multiple Failure State and strain controlled Triaxial tests” Rock Mechanics
7,pp. 17-33(1975) , Springer-Verlag 1975.
 Vaid,Y. P. , Negussey, D., and Zergoun, M.,”A Stress-and strain-controlled monotonic
and Cyclic Loading System,” Advanced Triaxial testing of Soil and Rock, ASTM STP
977, Robert T. Donaghe, Ronald C.Chaney, and Marshall L. Silver, Eds. , American
Society for Testing and Materials, Philadelphia, 1987 , pp.119-131,(1987)
 Mochizuki, A. , Mikasa, M. , and Takahashi, S. , ”A New Independent Principal
Stress Control Apparatus,” Advance Triaxial Testing of Soil and Rock, ASTM STP 977,
Robert T. Donag7he, Ronald C. Chaney, and Marshall L. Silver, Eds., American
Society for testing and Materials,Philadelphia,1988, pp. 844-858.(1988).
 Prisco, Di Claudio., and Imposimato, Silvia. “Experimental Analysis and Theoretical
Interpretation of Triaxial Load controlled Loose Sand Specimen Collapses” Mechanics
of Cohesive Frictional materials, VOL. 2, 93-120(1997)
 Sitharam, T.G. , Ravishankar B.V. , Patil S.M. “Liquefaction and Pore Water
Pressure Generation in Sand: Cyclic Strain Controlled Triaxial Tests”,3(1), pp.57-
85,January-June 2012.
23

24. BRIEF REFERENCE
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Cite this article as:
Samirsinh P Parmar. (2022). Triaxial Test on Soil - Important Insights for
Stress- Controlled and Strain-Controlled Test. Journal of Earthquake
Science and Soil Dynamics Engineering, 4(3), 1–16.
https://doi.org/10.5281/zenodo.6003 832

25. 25
http://hbrppublication.com/OJS/index.php/JESSDE/article/view/2215
Paper Link:
https://www.slideshare.net/samirsinhparmar/triaxial-test-on-soil-important-
insights-formatted-paper

26. Shear Strength ???
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