Long-term groundwater pressure monitoring in deep boreholes in the Horonobe Underground Research Laboratory Project

Yabuuchi, Satoshi; Kurikami, Hiroshi  ; Seno, Shoji*; Hara, Minoru; Kunimaru, Takanori; Takeuchi, Ryuji  

Long-term groundwater pressure monitoring has been performed in HDB-1,2,3,6,7 and HDB-8 boreholes in the Horonobe Underground Research Laboratory Project. Groundwater pressure in many levels in the boreholes shows an almost steady state at present, however it is still recovering since the beginning of the observation in some levels. Relatively high groundwater pressure is observed in HDB-2 borehole, about 7km away from the URL area. According to the groundwater pressure monitoring in deep boreholes so far, it is inferred that hydraulic head becomes higher with the increase of the depth and hydraulic head in the east is higher than in the west around the URL area. Through the groundwater monitoring, performance of the long-term groundwater monitoring systems could be examined and some problems of the parts could also be found.