This study analyzes the propagation of fractures around a gallery submitted to fluid injection. After recalling some concepts of fracture modeling in a porous medium, 2D simulations are carried out with the finite element code Disroc®. These simulations account for the anisotropy of the in-situ stress state. The impact of hydro-mechanical couplings under the effect of fluid injection is addressed by three approaches of increasing complexity: 1- The pressure is assumed to act only in the existing fractures and in the tunnel with no coupling in the rock mass. 2- The pressure field is assumed stationary, obtained from an independent simulation, and used as an input for the mechanical calculation. 3- The transient flow of the fluid in the fracture and in the rock, mass is considered and coupled with the mechanics. A comparison of these approaches clarifies the various contributions of hydromechanical couplings on fracture propagation over different time horizons.