Hydraulic Conductance of the EDZ around Underground Structures of a Geological Repository for Radioactive Waste

The present study focuses on the temporal evolution of hydraulic parameters of the Excavation Damage Zone (EDZ hereinafter). To that end, a hybrid finite/discrete element method (FEMDEM) was first used to simulate the geometry and geomechanical conditions of discrete fracture networks forming the EDZ, which develop in response to the excavation process in the rock mass around the underground structures of a radioactive waste repository ( NAGRA, 2013 ). The simulated geometry and geomechanical properties are mapped onto a finite element mesh, which allows us to solve the fluid motion equations at the near-field.

The resaturation of the EDZ causes a pore pressure increase at that zone. This leads to a decrease of the normal effective stress and, correspondingly, to the progressive closure of the fracture. This closure causes fracture hydraulic conductivity to drop in time, while matrix conductivity increases due to swelling.

The objectives of this study are:

1. To quantify the temporal evolution of hydraulic properties in response to pressure variations caused by
2. To quantify the temporal evolution of the specific axial flux through the EDZ.
3. To quantify the total time required for a full resaturation of the EDZ.