This thesis deals with the constitutive modeling of low permeability partially saturated geomaterials, in the framework of enhanced poromechanics. Partial saturation means in this context that the porous network is occupied at least by two different fluid phases, having their own wetting properties. The classical poromechanical model, based on Biot’s theory, will be therefore generalized in order to account for stress/strain localization, within the solid phase, and fluid fingering, within the fluid phases. Strain localization will be treated making use of strain gradient theory and plasticity whilst partial saturation following a phase-field modeling approach to multi-phase fluid flow. To this aim, on the one hand, a fully coupled gradient constitutive law of the porous skeleton and the saturating (mixture of) fluid(s) will be assumed, which means that the free energy of the overall continuum will be a function not only of strain and mass concentrations of the fluid components, but also of their gradients. On the other hand, irreversible deformations of the solid skeleton will be modeled adopting a suitable plasticity model. This approach stems from previous results published by the
coordinator of the project [1-2] and can be partly retrieved in a line of research pursued by Collin and Kotronis, see e.g. [3-4], for what concerns the gradient approach to (un)saturated poromechanics.
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