Development of modeling methodology for hydrogeological heterogeneity of the deep fractured granite in Japan

Constructing and operating a large underground facility for the geological disposal of high-level radioactive waste decades will cause changes in environment around facility. Since permeability heterogeneity fractured granite Japan are higher than those Europe, disturbance to groundwater due tunnel excavation is expected be complex. Therefore, modeling fracture characteristics important accurately predict construction after closure However, approach focused on deeper several hundred meters has not been completely established Japan. this study, we investigated methodology drift at depth 500 m Mizunami Underground Laboratory, as case study. As result, developed method estimate only parameters fractures but also hydraulic based reproducibility trace length distribution fractures. By applying method, it was possible construct Discrete Fracture Network (DFN) model that can reproduce statistical Besides, application conditioning correct location transmissivity match observation data specific site demonstrated enable evaluation local characteristics. Furthermore, relationship between in-situ investigation required hydrogeological clearly described, strategy investigation, modeling, panel design using DFN during phase useful knowledge project proposed.