A two-scale poromechanical model for cohesive rocks: Fid-Bau Portal

A two-scale poromechanical model for cohesive rocks

Frey, J. / Chambon, R. / Dascalu, C.

Abstract This paper presents a computational homogenization approach in the framework of poromechanics. A fully coupled hydromechanics problem is formulated at the macroscopic scale. The constitutive equations are replaced by results of numerical computations on a Representative Elementary Volume in order to obtain the overall stress of the mixture as well as its transmissivity properties. At the microscale, the material is assumed to be composed of an assembly of hyperelastic grains connected by cohesive interfaces. These interfaces are also channels of a network where the fluid can percolate. The fluid acts on the boundaries of the grains and influences the behavior of the cohesive interfaces. Conversely, the opening of the interfaces induces changes in the transmissivity properties of the corresponding channels. This yields a fully coupled hydromechanical problem at the microscopic scale. The finite element method is considered for the numerical solutions at both scales, the present approach extending the purely mechanical $ FE^{2} $ scheme to the coupled hydromechanical framework. The local macroscopic behavior resulting from the homogenization scheme is illustrated on different numerical tests. The results clearly show the coupling between damage and fluid permeability in the overall response, as a consequence of the small-scale interaction between the action of the percolating fluid, the deformation of the solid skeleton, and the failure of the cohesive interfaces.