Propagation analysis of fluid-driven fracture using the discrete crack approach

The hydro-mechanical (HM) coupled problem in jointed or susceptible of cracking concrete or rock is formulated by means of the Finite Element Method (FEM) with interface elements of “zero-thickness” and double nodes. Both types of elements (continuum and interface) are formulated in terms of the displacements and the fluid pressure at nodes. After assembly, a highly non-linear system of equations is reached due to the strong dependence between the permeability and the aperture of joints. Poro-elasticity is assumed in the continuum. The cubic law is considered to govern the longitudinal flow along the discontinuity, and the influence of a transversal potential drop is introduced by means of a transversal transmissivity that accounts for the possible existence of an interface skin. Application examples consisting of hydraulic fracture and pressure driven wedge-splitting tests are solved following two numerical strategies: staggered and fully coupled.