Fully coupled global equations for hydro-mechanical analysis of unsaturated soils

Fully coupled global equations are proposed for enhancing the performance of Finite Element analysis of unsaturated soils. The governing equation describing mechanical equilibrium is formulated in terms of net stress, and in the mass conservation equation the contribution of this net stress in determining the change of degree of saturation is also included. The novelty of this paper is the development of new global finite element equations that can be used to find an approximate solution to these governing equations. The new equations have a mechanical term appearing in the flow matrix that is additional to the usual hydraulic term. This is in contrast to previous studies in which the coupling matrices ignore this effect. A performance study has been conducted for undrained footing problems, which shows that the additional mechanical term appearing in the flow matrix has a large influence on the accuracy of the numerical results.