Development of a constitutive model for a bedded argillaceous rock from triaxial and true triaxial tests

In this work, a constitutive model that predicts the mechanical behaviour of Opalinus clay is developed. The model is based on the theory of plasticity, and takes into consideration the inherent anisotropy due to the existence of bedding planes, hardening behaviour before the peak strength, softening behaviour after the peak, and creep effects. The model was implemented into the equations of pseudostatic equilibrium to simulate the mechanical response of Opalinus clay during conventional triaxial tests (using cylindrical samples) and true triaxial tests (using cubic samples). The model satisfactorily reproduces the main physical processes that prevailed during those tests.