Implementation algorithm of a generalised plasticity model for swelling clays

A multi-mechanism generalisation of Sloan’s integration scheme for elasto-plastic laws has been developed in order to implement a double structure model for expansive clays into a FE code. The constitutive model is built on a conceptual approach for unsaturated expansive soils in which the fundamental characteristic is the explicit consideration of the two pore levels often present in expansive clays. The distinction between macro and microstructure provides the opportunity to take into account the dominant phenomena that affect the behaviour of each structural level and the main interactions between them. The model is formulated using concepts of classical and generalised plasticity theories. The integration scheme proposed can deal with the two plastic mechanisms defined in the model and can incorporate the effects of strains, suction and temperature in the stress integration process. A large scale heating test is analysed to check the capabilities of the implemented model to simulate an actual problem involving complex thermo-hydro-mechanical stress paths. The performance of the model has been very satisfactory and the proposed integration scheme has proved to be robust and efficient in solving a highly non-linear coupled problem.