Abstract: Clayey rock, an alternative medium for the geological disposal of high-level waste, is highly valued by many countries. For the clayey rock underground disposal repository, the excavation of the gallery damages the host rock and further induces the propagation of the internal fractures. During this construction process, on the one hand, the permeability of the host rock increases, which reduces its capacity for retaining radionuclides. On the other hand, due to the hydro-mechanical coupling effect, the internal fractures are gradually sealed as the clayey rock has good self-sealing properties. Then the fracture permeability may recover slowly until close to the original rock state after an extremely long time span. In this paper, the experimental studies are carried out to investigate the saturation process of clayey rock under different conditions by means of the resistivity measurements. The effects of damage degree and the saline solution on the saturation process of clayey rock are studied by measuring the equivalent resistivity. The results show that: (1) The equivalent resistivity decreases gradually with the increase of the saturation and finally tends to a steady value. (2) The equivalent resistivity is not only closely related to the saturation but also the internal structure of the clayey rock. The relation between the fissures and the resistivity distribution provides guidance to detect the fissures in the clayey rock by using the resistivity method. (3) The fracture becomes the preferential channel for the water flow in the clay rock. Due to the hydration expansion reaction between water and clay minerals, the fracture seals to a certain extent, which can be indirectly reflected by the resistivity test.

Key words: clayey rock, moisture migration, self-sealing of fractures, resistivity method