The following parameters are known for a saturated normally consolidated clay: N = 2.32, = 0.15, = 2.17 and M = 0.94.
i. Estimate the value of void ratio (e) and principal stress difference (q) at failure if an undrained triaxial compression test was conducted on the clay specimen consolidated under cell pressure (3) of 350 kPa, with back pressure of 200 kPa. Sketch the effective stress path of the test on the q-p’ plane. Describe the change of pore water pressure in the soil during undrained compression. (6 marks)
ii. Derive the relationship between undrained shear strength (c) of normally consolidated clay, and the parameters , M, N, and mean effective stress after isotropic
consolidation (p′ ). c
Equation of ICL: Equations of CSL:
= − p′ ′ = p′
= − p′