Saturation-Induce Failure: Mechanics of a Class of Unstable Processes

This paper presents an analytical investigation on the stability of multiphase porous media subjected to changes in fluid pressures and/or saturation conditions. For this purpose, we revisit the concept of second-order work and explore its relation with the incremental energy input in partially saturated media. Our analytical results show that second-order work contributions do not involve only effective stresses and skeletal deformation, but also depend on the changes in fluid pressures and degree of saturation. This result provides a novel approach to address unstable processes in unsaturated porous media and enables a number of theories originally conceived only for fluid-saturated compounds to be extended for unsaturated media.