ABSTRACT
Many projects of underground repositories for high level radioactive waste involve an engineered clay barrier, made of dried and compacted clay and placed between the waste canister and the surrounding rock. When hydrated, this barrier seals the gap and provides a good watertightness, thanks to the hydro-mechanical coupled behaviour of the clay. In order to model this coupled behaviour, a macroscopic thermodynamical approach extending Biot’s theory to unsaturated porous media is proposed. This thermodynamical modelling founds a general framework for non linear poro-elastic coupled behaviours, inducing consistent symmetrical couplings which allow to take into account the often neglected influence of the mechanical state on the hydraulic problem of the resaturation of the clay. The symmetry of these couplings allows a restricted experimental determination focused on few intrinsic curves. It also allows, reciprocally, a validation of the whole thermodynamical approach through dual experiments. Finally, the influence of mechanics on hydraulics due to this symmetrical hydro-mechanical coupling makes it possible, when introduced into the complete resolution of the flow problem, to study the influence of the rheological behaviour of the clay on the evaluation of its resaturation time.
