Characterization of the hydromechanical behavior of argillaceous rocks with effective gas permeability under deviatoric stress

The realization of nuclear waste storage in the deep geological formation will change the hydromechanical properties of the host rocks around the man-made openings due to the stress redistribution during the excavation stage and the variation of the hydraulic conditions during the open drift stage and the closure stage. This paper mainly presents an experimental study on the evolution of effective gas permeability of Callovo–Oxfordient argillaceous rocks during dehydration and rehydration processes and its variation under loading and unloading conditions. The experimental results show that effective gas permeability increases with the diminution of degree of saturation, and the logarithm of effective gas permeability is in quasi linear relation to saturation for the degree of saturation less than 90%. But effective gas permeability is not sensitive to the deviatoric stress, even if the deviator exceeds the damage threshold. The method of mercury intrusion has also been used in studying the microstructure of argillaceous rocks.