Assessment of uncertainties associated with the characterization of the geological environment in the Tono Area -Japanese fiscal year, 2005- (Contract research)

Toida, Masaru*; Suyama, Yasuhiro*; Mori, Takayuki*; Inaba, Takeshi*; Atsumi, Hiroyuki*; Tanaka, Toshiyuki*; Kobayashi, Ichizo*; Nakajima, Makoto*; Ogata, Nobuhisa 

"Geoscientific research" at the Tono Area is developing site investigation, characterization and assessment techniques for understanding of geological environment. Their important goal is to establish a methodology for analyzing uncertainties in a heterogeneous geological environment and to develop investigation techniques for efficiently reducing the uncertainties. In Fiscal Year 17, in addition to information from the MIZ-1 borehole investigation, present knowledge has been compiled. The proposed technique has been improved through conceptual geological modeling and groundwater analyses at the Tono Area. Design options for handling geological uncertainties based on the characterization of the geological environment have also been tested. The results of this study can be summarized as follows: (1) It was shown that the fracture group with NW strike has high correlation with maximum measured transmissivity. This was maybe caused by the effect of regional in situ stress. (2) Through conceptual geological modelling and groundwater analysis, a procedure for modelling of the geological environment with heterogeneous characteristics was proposed. (3) From the viewpoint of improving the design of an underground facility, the existence of uncertainties of the geological environment with heterogeneous characteristics requests multiple options. A design option should be adapted to the geological environment with heterogeneous characteristics.