Hydrogeological conceptual model determined from baseline and construction phase groundwater pressure and surface tiltmeter data at the Mizunami Underground Research Laboratory, Japan

Takeuchi, Shinji; Takeuchi, Ryuji  ; Salden, W.*; Saegusa, Hiromitsu; Arai, Takashi*; Matsuki, Koji*

A hydrogeological conceptual model has been developed based on pressure responses observed at multilevel pressure monitoring zones in seven boreholes and surface tilt data in and around the Mizunami Underground Research Laboratory site. Pressure changes caused by some earthquakes, cross-hole hydraulic testing, and shaft excavation activities are considered. Surface tilt has been measured from the half way of the shaft excavation phase. Continuous monitoring with some numerical analysis during the shaft excavation phase show the existence of the flow barrier fault predicted from the surface-based investigation phase and hydraulic parameter around the shafts.