Groundwater pressure monitoring in the Mizunami Underground Research Laboratory Project; Hydrogeological and groundwater flow characterization

Takeuchi, Ryuji  ; Saegusa, Hiromitsu; Onoe, Hironori ; Beppu, Shinji

The Mizunami Underground Research Laboratory (MIU) is now under construction by the Japan Atomic Energy Agency. Long-term monitoring (LTM) of groundwater pressure has been carried out to understand the baseline conditions and to obtain information on changes of groundwater flow during MIU construction. As the results of LTM. In the baseline monitoring, hydrogeological compartmentalization is formed by faults. The result also shows that faults make the hydraulic gradient in the divided domain smaller. The pressure changes associated with MIU construction is heterogeneous due to the distribution of faults. Hydraulic connectivity and continuity of hydraulic structures could be evaluated based on the monitoring results. The spatial distribution of hydraulic properties could also be estimated by calibration of the hydrogeological model based on monitoring data. Thus, the LTM of groundwater pressure is useful for hydrogeological and groundwater flow characterization.