The 2D hydro-mechanically coupled response of a rock mass with fractures via a mixed BEM-FEM technique

This paper describes the essential features of a numerical technique for the simulation of the coupled fluid flow and deformation in a 2D assembly of poroelastic blocks and transmissive fractures. The boundary element method (BEM) is applied to each block to reduce Navier and diffusion equations to a set of integral equations involving block boundary terms, whereas a Galerkin weighted-residuals finite element method (FEM) is applied to the fracture diffusion equations. In addition, fracture local equilibrium is rendered through spring-like equations relating the stresses to the relative displacements of the fracture walls. A time-marching process is implemented leading to an algebraic system where the right-hand side vector is built based on the collected solutions of the previous time steps. The technique requires the meshing of the fracture network only. The accuracy of the results is adequate even With relatively coarse meshes without the resort to small time steps at the beginning of the simulation. It furnishes outputs that focus only on the salient features of the response. The efficiency of the technique is demonstrated through the illustration of the results of three examples