Microstructural modelling of stress-dependent behaviour of clay

The purpose of this paper is to investigate the stress-dependent behaviour of clay during drained and undrained shearing by means of a micromechanical approach. A new micromechanical stress–strain model is developed for clay using the approach developed in earlier studies by Chang and Hicher [Chang, C.S., Hicher, P.Y., 2005. An elastic–plastic model for granular materials with microstructural consideration. International Journal of Solids and Structures 42(14), 4258–4277]. In order to model the extension test on a K0 consolidated sample, a formulation is developed to account for the stress reversal on a contact plane. The model is then used to simulate numerous stress-path tests on Lower Cromer Till and kaolin clay, including triaxial compression and extension tests, under both undrained and drained conditions, with different K0 consolidation, and different over-consolidation ratios. The applicability of the present model is evaluated through comparisons between the predicted and the measured results. The evolution of local stresses and local strains at inter-particle planes are discussed in order to explain the stress-induced anisotropy due to externally applied load. All simulations have demonstrated that the proposed micromechanical approach is capable of modelling the stress-induced anisotropy and other major features of the complex behaviour in clay.