Fluid fingering and strain localization are manifestations of possibly coupled instability in geomaterials. In order to capture these two phenomena and their possible interaction a phase field approach to partially saturated porous media is adopted, considering the mixture of a liquid and a gas as a Cahn-Hilliard non-uniform fluid; the behavior of the solid skeleton is described extending the variational phase-field approach to fracture to partially saturated porous media within the framework of poromechanics. The proposed model is capable to capture the effects of the fluid fingering on the strain and stress distributions under hydraulic loading (drainage and imbibition) and vice-versa the effects of fracturing and strain localization on the heterogeneous fluid flow through the porous medium.
A parallel experimental campaign is also in progress in order to identify fluid fingering nucleation and propagation and to measure the induced localized strains via a new biaxial apparatus specially designed for this project.
October 30, 2020