Understanding gas transport processes is one of the key issues in the assessment of radioactive waste repository performance and is the focus of this research. To this aim, this research programme was started with the following specific objectives. 1) To develop and calibrate an experimental set-up to perform controlled flow-rate gas injection experiments using a high-pressure triaxial cell to apply isotropic/anisotropic stress states. 2) To carry out a series of tests on Opalinus clay OPA samples to study the conditions under which gas breakthrough processes occur, to analyse the influence of the gas injection rate, the stress state, the orientation of rock discontinuities and other relevant hydro-mechanical variables (porosity, degree of saturation, …), as well as the observation of the induced desaturation (pore water displacement by gas), ingoing and outgoing gas fluxes, aperture and preferential paths created, and so on.

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