Mizunami Underground Research Laboratory project (Study on hydrogeology in crystalline fractured rock); Geo-risk management focused on water inrush using discrete fracture network model

Onoe, Hironori ; Saegusa, Hiromitsu; Motoshima, Takayuki*; Ijiri, Yuji*; Otsu, Hiroyasu*

It is important to evaluate the influence of water inrush into underground facility on costs and schedules for construction of deep underground facility based on prior information. In this study, risk assessment method using a combination of discrete fracture network model with financial engineering theory has been developed taking into account unexpected water inrush into the underground facility constructed in crystalline fractured rock. The risk assessment method has been applied to the construction of the Mizunami Underground Research Laboratory. The relationship between the amount of information due to the progress of investigations and the risk regarding cost variation for the countermeasure against water inrush has been evaluated. As a result, site characterization procedure for decreasing the water inrush risk efficiently was suggested. The applicability of the risk assessment method for the ex-post-facto assessment of construction of the underground facility was also confirmed.