Modeling clay response along slip surfaces

The paper proposes and validates a constitutive model simulating the change of resistance along clay slip surfaces under both undrained and drained conditions. The proposed model is based on (a) the critical state theory and (b) the assumption that the critical state changes once failure is reached, in terms of the further shear displacement. Under undrained conditions, the proposed model simulates the excess pore pressure generation and subsequently the change of clay resistance along the slip surface from its initial value to the peak strength and then at large displacement the residual value measured in constant-volume ring shear tests. Under drained conditions, the model simulates the normal displacement change and subsequently the change of clay resistance along the slip surface in clays as measured in drained ring shear tests.