Development of Grouting Technologies for HLW Disposal in Japan (3) – Development of a Hydro-geological Model using a Discrete Fracture Network –

To better understand the grouting process and the effect of grouting on the performance of a nuclear waste repository, the Japanese Atomic Energy Agency has initiated a grouting test carried out in the fractured granite of the Grimsel Test Site in Switzerland. This paper describes the characterization of the rock mass carried out over a three year period, and how the data obtained has been used to make a discrete fracture network (DFN) model that attempts to account for as much known knowledge as possible (e.g. the location and orientation of fractures observed in the boreholes and the measured hydraulic transmissivity of 46 short intervals). Based on the DFN model developed, an equivalent continuous porous media (ECPM) model is generated for the purpose of numerical simulation of the grout injection process. The results of tracer testing have been used to optimize the specific storage and porosity distribution of the ECPM model.