A coupled approach for the simulation of hydro-mechanical fracturing in porous rocks

The hydro-mechanical coupled problem in jointed or susceptible of fracturing rocks is formulated via the FEM with "zero-thickness" interface elements and double nodes. Poro-elasticity is assumed in the continuum medium. The cubic law is considered to govern the longitudinal flow along the discontinuity, and the influence of a head drop transversal to the joint is introduced by means of a transversal transmissivity that takes into account the possible existence of a fracture skin. The mechanical constitutive model depends on the type of problem being analyzed, whether it is a pre-existing joint (rock mechanics-based model) or a developing crack (fracture mechanics-based model). The problem is formulated in terms of the displacements and the fluid pressure at the nodes, leading to a system of equations that can be solved simultaneously or via a staggered strategy. Application examples are analyzed using both procedures.