Stepwise Hydrogeological Modeling and Groundwater Flow Analysis on Site Scale (Former Stage of Step 3)

Onoe, Hironori ; Saegusa, Hiromitsu; Endo, Yoshinobu*

One of the main goals of the Mizunami Underground Research Laboratory Project is to establish comprehensive techniques for investigation, analysis, and assessment of the deep geological environment. To achieve this goal, a variety of investigations are being conducted using an iterative approach.In this study, hydrogeological modeling and groundwater flow analyses have been carried out using the data from surface-based investigations at former stage of Step 3 (deep borehole investigations without reflection seismic survey and vertical seismic profiling investigations), in order to synthesize the investigation results, to evaluate the uncertainty of the hydrogeological model, and to specify items for further investigation.The results of this study are summarized as follows :1) The uncertainty of hydrogeological model of the site scale is decreased as stepwise research;2) Borehole investigations combined with hydraulic monitoring are useful for decreasing the uncertainty of hydrogeological model;The main items specified for further investigations are summarized as follows :1) Trend, length, and hydraulic parameters of faults confirmed in the MIU construction site;2) Shape of boundary of geological layer, and hydraulic parameters of rock;3) Hydraulic head distribution of deep underground.