Two drained triaxial compression tests are carried out on "identical" specimens of clean sand. In each test, a fully saturated specimen is consolidated to a confining stress and then failed by increasing the vertical stress. The test results are summarized in the following table. Assume the specimens in these two tests are uniform and have the same density. Cell pressure Deviatoric stress q (kPa) σ3 (kPa) Test No. Test 1 (Drained) Test 2 (Drained) Test 2a (Undrained) 100 200 200 Peak stress state 270.0 540.0 150.0 Residual state (or critical state) 200.0 400.0 70.0 (a) Using the results of Tests 1 and 2, determine the effective friction angle of the sand at peak failure state. (b) What is most likely the orientation of the shear failure plane in Test 1? (c) When repeating Test 2, the technician did not open the drainage valve by mistake when shearing the specimen after consolidation. In other words, the consolidated specimen was sheared under the undrained condition. The maximum deviatoric stresses were measured as 150 kPa with the deviatoric stress of 70 kPa at the residual state. Explain why the test results in Test 2 and Test 2a are different.

Two drained triaxial compression tests are carried out on "identical" specimens of clean sand. In each test, a fully saturated specimen is consolidated to a confining stress and then failed by increasing the vertical stress. The test results are summarized in the following table. Assume the specimens in these two tests are uniform and have the same density. Cell pressure Deviatoric stress q (kPa) σ3 (kPa) Test No. Test 1 (Drained) Test 2 (Drained) Test 2a (Undrained) 100 200 200 Peak stress state 270.0 540.0 150.0 Residual state (or critical state) 200.0 400.0 70.0 (a) Using the results of Tests 1 and 2, determine the effective friction angle of the sand at peak failure state. (b) What is most likely the orientation of the shear failure plane in Test 1? (c) When repeating Test 2, the technician did not open the drainage valve by mistake when shearing the specimen after consolidation. In other words, the consolidated specimen was sheared under the undrained condition. The maximum deviatoric stresses were measured as 150 kPa with the deviatoric stress of 70 kPa at the residual state. Explain why the test results in Test 2 and Test 2a are different.

Fundamentals of Geotechnical Engineering (MindTap Course List)

5th Edition

ISBN:9781305635180

Author:Braja M. Das, Nagaratnam Sivakugan

Publisher:Braja M. Das, Nagaratnam Sivakugan

Chapter10: Shear Strength Of Soil

Section: Chapter Questions

Problem 10.12P

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