Stepwise Hydrogeological Modeling and Groundwater Flow Analysis on Site Scale (Step0 and Step1)

Oyama, Takuya ; Saegusa, Hiromitsu; Onoe, Hironori ; 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 Step 0 and 1, 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 understanding of groundwater flow was enhanced from Step0 to Step1, and the hydrogeological model could be revised;2) The importance of faults as major groundwater flow pathways was demonstrated;3) Geological and hydraulic characteristics of faults with orientation of NNW and NW were shown to be especially significant;The main item specified for further investigations is summarized as follows: Geological and hydraulic characteristics of NNW and NE trending faults.