An unsaturated hydro-mechanical modelling of two in-situ experiments in Callovo-Oxfordian argillite

•Experimental data synthesis for retention curve and relative permeabilities for COx.•Models for fluid transfers in unsaturated conditions are important.•Determination of retention curve and gas permeability close to saturation is needed.•An accurate model for fluid transfers between rock mass and surrounding air is needed.•Dissolved gas plays a significant role on the compressibility of liquid phase.

The unsaturated behaviour of Callovo-Oxfordian argillite is investigated through the modelling of 2 in-situ experiments. The first test studies the influence of ventilation in a gallery on the hydro-mechanical behaviour of the rock mass. The second test consists in a gas injection in the rock mass from an experimental borehole. A hydro-mechanical model is described and used in the modelling of the experiments. A review of the main hydro-mechanical parameters of argillite is presented. The numerical results highlight the need of a flow boundary condition reproducing the fluid transfers between the surroundings and the rock mass. The influence of dissolved gas on the compressibility of the liquid phase is also emphasised.