Principles of Foundation Engineering
9th Edition
ISBN: 9780357684832
Author: Das
Publisher: Cengage Learning US
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Chapter 2, Problem 2.20P
To determine
Find the pore water pressure within the specimen.
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A consolidated undrained triaxial test was
performed on a normally consolidated clay
with a critical state friction angle of 230. After
an initial isotropic consolidation at a cell
pressure of 50 kPa, drainage was turned off,
the cell pressure was increased to 85 kPa,
and the sample was loaded to ultimate
conditions. A pore pressure of 55 kPa was
measured at ultimate state. What value of
major principal total stress was measured at
the ultimate state?
A consolidated drained (CD) triaxial test was carried out on a normally consolidated clay. The specimen was consolidated under a cell pressure of 100 kPa and back pressure of 30 kPa. The axial deviatoric stress was increased very slowly to failure, so that there was no excess pore water pressure developed during the shearing. The specimen failed under a deviatoric stress of 130 kPa. The back pressure of 30 kPa was maintained throughout the test.
(i) What is the friction angle in terms of effective stresses? (ii) What are the shear stress and normal stress acting on the failure plane?
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A consolidated drained (CD) triaxial test was carried out on a normally consolidated clay. The specimen was consolidated under a cell pressure of 100 kPa and back pressure of 30 kPa. The axial deviatoric stress was increased very slowly to failure, so that there was no excess pore water pressure developed during the shearing. The specimen failed under a deviatoric stress of 130 kPa. The back pressure of 30 kPa was maintained throughout the test.
(1) What is the friction angle in terms of effective stresses?
(ii) What are the shear stress and normal stress acting on the failure plane?
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Principles of Foundation Engineering
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- In a triaxial test, a specimen of saturated [normally consolidated] clay was consolidated under a chamber confining pressure of 80 kPa. The axial stress on the specimen was then increased through the allowing the drainage from the specimen. The specimen fails when 120 kPa. The pore water pressure at the time was 50 kPa. What is the consolidated undrained friction angle [phi]?arrow_forwardThe shear strength parameters in terms of effective stress are: C = 15 kPa and o' = 30°. In an unconsolidated undrained (UU) triaxial test on a sample of this clay, the cell pressure was 250 kPa and the deviator stress at failure was 136 kPa. The pore water pressure at failure will be (in kN/m2, upto one decimal place).arrow_forwardA drained triaxial compression test on a saturated clay yielded the effective shear strength parameters as c' = 15 kPa and o'= 22°. %3D Consolidated Undrained triaxial test on an identical sample of this clay at a cell pressure of 200 kPa developed a pore water pressure of 150 kPa at failure. The deviator stress (expressed in kPa) at failure isarrow_forward
- 5. A consolidated, undrained triaxial test is being caried out on a normally consolidated clay where c = 0 and 41= 26'. The triaxial specimen was consolidated under a cell pressure of 300 kPa and backpressure of 80 kPa. Skempton's A parameter at failure is estimated to be 0.80. The drainage valve has since been dosed and the vertical deviator stress increased to failure. What would be the deviator stress and pore water pressure at failure?arrow_forwardThe results below were obtained at failure in a series of consolidated-untrained triaxial tests, with pore water pressure measurement, on specimens of a fully saturated clay. Determine the values of the shear strength parameters c' and 'If a specimen of the same soil were consolidated under an all-round pressure of 300 kN/m² and the principal stress difference applied with the all-round pressure changed to 400kN/m², what would be the expected value of principal stress difference at failure" 150 300 450 600 03 (kN/m²) 01-03 (kN/m²) u (kN/m²) 103 202 305 410 82 169 252 331arrow_forwardA consolidated-undrained triaxial test was conducted on a dense sand with a chamber-confining pressure of 20 lb/in?. Results showed that o' = 24° and o = 31°. Determine the deviator stress and the pore water pressure at failure.arrow_forward
- • In consolidated-drained triaxial test on a normally consolidated clay, the specimen failed at a deviator stress of 124 KN/sq.m. If the effective stress friction angle is known to be 31°, what was the effective confining pressure at failure?arrow_forwardA consolidated-drained triaxial test is carried out on a sand specimen that is subjected to 80 kN/m² confining pressure. The vertical deviator stress was increased slowly such that there is no built-up of pore water pressure within the specimen. The specimen failed when the addition axial stress reached 240 kN/m². Find the friction angle of the sand. If another identical sand specimen was subjected to 150 kN/m' confining pressure, what would be the deviator stress at failure.arrow_forward5. A consolidated, undrained triaxial test is being carried out on a normally consolidated clay where c - 0 and p'= 26'. The triaxial specimen was consolidated under a cell pressure of 300 kPa and backpressure of 80 kPa. Skempton's A parameter at failure is estimated to be 0.80. The drainage valve has since been dosed and the vertical deviator stress increased to failure. What would be the deviator stress and pore water pressure at failure?arrow_forward
- Undisturbed samples from a normally consolidated clay layer were collected during a subsoil exploration .Drained triaxial tests showed that the effective friction angle was ? ′ = 25°. The unconfined compressive strength, ??, of a similar specimen was found to be 133 KN/m2 . Find the pore pressure at failure for the unconfined compression test.arrow_forwardProblem 3: A consolidated-drained triaxial test is carried out on a sand specimen that is subjected to 80 kN/m? confining pressure. The vertical deviator stress was increased slowly such that there is no built-up of pore water pressure within the specimen. The specimen failed when the addition axial stress reached 240 kN/m?. Find the friction angle of the sand. If another identical sand specimen was subjected to 150 kN/m? confining pressure, what would be the deviator stress at failure.arrow_forwardIn a tri-axial test of normally consolidated clay, the sample subjected to chamber confining pressure of 250 kPa and failed when deviator stress is 350 kPa. Which of the following gives the angle of internal friction? Which of the following gives the shear stress at failure? Which of the following gives the effective normal stress at maximum shear?arrow_forward
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