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Ozaki, Yusuke; Ishibashi, Masayuki; Matsushita, Tomoaki*; Masumoto, Kazuhiko*; Imasato, Takehiko*
Proceedings of 13th SEGJ International Symposium (USB Flash Drive), 4 Pages, 2018/11
In the Mizunami Underground Research Laboratory, Groundwater REcoverty Experiment in Tunnel (GREET) is performed to understanding the recovery process of geological environment after the closure of drift. In this experiment, we performed 2D electrical resistivity surveys three times. First survey was performed before the closure of test drift. Second and third surveys were performed after the closure test. The first survey detected two layers conformation that consists of conductive and resistive zones at shallower and deeper part from the drift surface, respectively. These layers correspond to the shotcrete and host rock, respectively. Second and third measurements show that the conductive zone expanded to deeper resistive part while the shallower conductive part did not change. We concluded that we captured the saturation process of dried fractures near the drift wall by closure of drift as an electrical resistivity response.
Ozaki, Yusuke; Matsushita, Tomoaki*; Masumoto, Kazuhiko*; Imasato, Takehiko*
no journal, ,
In Mizunami Underground Research Laboratory, Groundwater REcovery Experiment in Tunnel (GREET) is performed to capture the post closure behavior of geoenvironment near the test drift. For the evaluation of physical property near the drift wall, repetitive electrical resistivity surveys are performed. The tomography results indicate the resistivity change following to the change in water saturation in the host rock. In this study, we convert the resistivity value to the saturation by using the equation proposed by Kusumi et al., (2006) to clear the degree of change in saturation. Estimated saturation clearly shows the abrupt rise and gentle reduction after drift closure and release of drift, respectively.