A thermodynamic-based macroelement framework for soil-foundation systems with coupled hydro-mechanical behaviour

The plasticity-based macroelement approach for simulating soil-structure interaction in the analysis of structures is rapidly extending by virtue of its efficient balance between accuracy and computational demand. This approach has been mostly developed neglecting the effect of any excess pore water pressures produced by load cycles which can be, however, somewhat unrealistic in the case of saturated soils under dynamic loading. To overcome this long-standing limitation, the present paper develops a formulation comprising the effects of the hydro-mechanical coupling of the soil behaviour on the multiaxial foundation response. This is handled through a consistent thermodynamic framework, in which the time evolution of the stiffness and resistance of the macroelement is controlled by an internal variable accounting for drainage conditions. A complementary damage variable simulates the temporary degradation of the macroscopic mechanical features induced by the pore water pressure build-up. The macroelement is tested under different conditions, highlighting the importance of the coupled hydro-mechanical soil behaviour on the foundation performance.