The friction angle obtained for clean sand at its loose state is 30°. When this sand is tested…
3. (a) The friction angle obtained for a clean sand at its loose state is 30°. When this sand is tested at a dense state under a drained condition, the mobilized friction angle becomes 40°. What would be the maximum dilatancy ratio, dEuP/dEIP obtained?
(b) The critical state lines (CSL) and the normally consolidation line (NCL) for a reconstituted clay have been determined to be: CSL: qcs = 0.95p’cs vcs = 2.06 — 0.1 In p’us NCL: v = 2.12 — 0.1 In p’ where, p’ = + 2o3 )13, q = a, — 03, and v is the specific volume. The soil parameter K = 0.02 is also known.
An isotropically consolidated undrained compression (CIUC) triaxial test was carried out on this clay under an effective consolidation stress of 400 kPa. The clay was normally consolidated under this consolidation stress.
(i) Calculate the undrained shear strength and the pore-water pressure at failure obtained from this CIUC test.
(ii) Sketch schematically the likely effective stress path q – p’ and the specific volume versus p’ curves. Plot the CSL and NCL with all the values marked clearly on the same graphs.
(iii) Calculate the effective friction angle obtained from this CIUC test.
(iv) What will be the deviator stress and specific volume at failure if the above test is carried out under a drained condition given the other test conditions the same? What will be the maximum dilatancy ratio obtained from this test?
(v) If the above CIUC test is carried out by firstly consolidating the soil specimen under 400 kPa and then under 100 kPa before the undrained shearing, what would be the cu value obtained from this test? (20 Marks)