This paper on "Hydro-Mechanical Coupling in Unsaturated Porous Media: An Experimental and Numerical Approach" was presented at the NAFEMS World Congress on Effective Engineering Analysis - 25-28 April 1999, Newport, Rhode Island, USA.

Summary

Recently, a numerical model for unsaturated porous media based on the theory of mixtures has been developed by the authors [1]. In the past, the model has been successfully applied to simple, one-dimensional cases [2].
This model is based on the continuum theory of mixtures and treats a three phase porous medium (solid, liquid and gas). Principal field variables are solid deformation, liquid pressure and gas pressure. The specific density of the solid grains is considered constant, the gas phase is governed by the ideal gas law. The two fluid phases flow freely and a nonlinear pore pressure - saturation relation is used. The resulting system of equations is discretized in space using the finite element technique and in time via an explicit Euler scheme.
In this paper, an extension to nonlinear-elastic soil behavior is proposed. Duncan's model is implemented using a predictor-corrector-type approach.
Furthermore, this paper deals with the validation of the above coupled hydromechanical model. The hydromechanical-nonlinear elastic model is applied to both 1D and 2D cases. The 1D case involves a drainage processes for silty sand and a the 2D calculations are concerned with a slope stability problem. The results are compared to laboratory experiments.
These laboratory experiments conducted at the LMS/EPFL involve pore pressure and solid displacement measurements (both surface displacements and in-plane displacements on a sidewall using image processing techniques) as well as flux data.
It is shown that the numerical results obtained with the model are in good agreement with the experiment. The validity of this approach is demonstrated and the importance of considering the three phase formulation is emphasized.