A unified approach to numerical modeling of fully and partially saturated porous materials by considering air dissolved in water

This paper presents a unified mathematical approach to model the hydro-thermo-mechanical behavior of saturated and partially saturated porous media by considering the effects of air dissolved in liquid water. The model equations are discretized by means of the Finite Element method. A correspondingly updated code is used to analyze two examples; the first one is the well known Liakopoulos test, i.e. the drainage of liquid water from a 1m column of sand, which is used to validate numerically the model here developed. As second example, a biaxial compression test of undrained dense sands where cavitation takes place at strain localization is simulated. It is shown that considering the dissolved air has a small influence on the overall results of numerical simulations, while the histories of the fluid variables (gas and capillary pressure and water saturation) differ from other approaches neglecting the air dissolved. This may be important if appropriate constitutive models for partially saturated materials are used. A major advantage of the proposed procedure is that it allows for a unified modeling of partially and fully saturated zones in porous media without application of any `unphysical' numerical technique.