Evaluation of changing water content around tunnel during drift closure test by using resistivity method

Ozaki, Yusuke  ; Matsushita, Tomoaki*; Masumoto, Kazuhiko*; Imasato, Takehiko*

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.