A theoretical investigation of a mechanical response of fluid-saturated porous materials based on a coupled discrete-continuum approach

We propose a numerical model of liquid-saturated porous material, based on a coupled approach combining a discrete elements method and finite difference method. An ensemble of discrete elements simulates processes of deformation of a porous solid and filtration of single-phase liquid in an interconnected network of "micropores". Mass transfer of a fluid between the "micropores" and "macropores" (the latter are considered as the areas between spatially separated and non-interacting discrete elements) is calculated on a finer grid superimposed on an ensemble of movable discrete elements. The developed model was applied to study a mechanical response of brittle samples with water-saturated pore volume. It has been shown that the strength of liquid-saturated samples is determined not only by strength properties of "dry" material and a pore pressure, but largely by sample geometry, deformation rate and characteristics of porosity of a material. We suggest a generalizing dependence of the uniaxial compressive strength of water-saturated permeable brittle material on the specific diameter of filtration channels, which is the ratio of the characteristic diameter of the filtration channels to the square root of the strain rate. Values of parameters of mentioned dependence are strongly connected with the character of the relation between pore volume and pressure of a liquid.