Hydro-mechanical modelling of the development of preferential gas pathways in claystone

During long-term repository of radioactive waste in argillaceous formation, the gas migration in the host formation and in the engineered barriers is a crucial issue, because it could affect the safety function of the clay barriers. Gas migration tests on Callovo-Oxfordian argillite have been performed by the British Geological Survey. The observations show that gas migration is often accompa-nied by the development of preferential pathways, which propagate through the sample. Hydro-mechanical numerical modelling of these tests is performed. It ap-pears that a continuum approach to the movement of gas is not sufficient to repro-duce the experimental observations. A coupling between deformation of the me-dium, permeability and air entry pressure is proposed. The numerical results show that such coupling play an important role in a successful simulation of such gas flows.