k0–Undrained shear strength ratio of normally consolidated clays from CIUC tests

Consolidated isotropic undrained compression (CIUC) triaxial tests are commonly used in practice to determine the undrained shear strength of normally consolidated clays, even though consolidated anisotropic undrained compression (Ck₀UC) tests are more appropriate to model in situ conditions. This paper describes a simple procedure to predict the Ck₀UC shear strength ratio directly from the results of a single CIUC test. It is developed within the general framework of the modified Cam–Clay model A reformulation of the plastic volumetric strain ratio Λ as a function of the Skempton’s pore pressure coefficient at failure A_r,i and of the effective angle of shear resistance ϕ′ enables the prediction of the Ck₀UC shear strength ratio using only these two parameters, both obtainable from a single CIUC test. The experimental data avaiable from different clays put into evidence a good agreement between predicted and measured values.