Consideration on pressure response to shaft excavation

Toya, Naruhisa; Takeuchi, Ryuji  ; Onoe, Hironori ; Keya, Hiromichi

At the Mizunami Underground Research Laboratory construction site in Gifu Pref., construction of two vertical shafts, each to a depth of 1000 m, began in 2003. The hydraulic groundwater pressure of the bedrock is monitoring in order to understand the change in the geological environment resulting from the shaft excavation activities. Several near-vertical faults that cross the URL site ware identified some our study. One fault (NNW fault) in particular is hydrogeologically significant groundwater flow barrier. In 2007, we drilled a borehole at 200 m depth of Shaft. This borehole is nearby the estimated NNW fault. Multi-level groundwater pressure monitoring data show significant pressure response resemble to the reverse water-level fluctuation to the drilling work. In this study, we report the usability of the significant pressure response "reverse water-level fluctuation" for estimation of the hydrogeological flow.