Finite element implementation of a fully coupled hydro-mechanical model and unsaturated soil analysis under hydraulic and mechanical loads

The finite element implementation of a fully coupled hydro-mechanical constitutive model Zhou et al. (2012a, b) is presented here. An explicit integration scheme with four main steps is adopted to integrate the constitutive relation coupling with the soil water retention model. The finite element program can simulate complex hydro-mechanical processes with highlights on flow-deformation coupling and hydraulic hysteresis. The performance of the developed program is validated at both element level (against unsaturated triaxial test results) and small-scale model set-up level (against 1-d consolidation, sand column and loading/wetting test results). Several applications for unsaturated soils are analysed, including: (1) equilibrium processes after fast-drying/wetting (1-d); (2) slow-loading after different suction histories (1-d, compared with the finite element results by Sheng et al. (2003b); and (3) a flexible footing (2-d) affected by a leaking underground pipe.