Numerical modeling of a real-scale nuclear waste engineering barrier experiment

Deep geological repository involving a multi-barrier system constitutes one of the most promising options to isolate high-level radioactive waste from the human environment. The efficiency of Engineered-Barrier Systems (EBS) is highly based on the complex behaviour of bentonite. To improve the understanding of the processes involved in the EBS, results from a near-to-real scale experiment, the FEBEX experiment, are studied by means of a thermo-hydro-mechanical (THM) finite element approach including a consistent thermo-plastic constitutive model for unsaturated soils. The model also features a coupled THM approach of the water retention curve. The results of the numerical simulations are compared with sensor measurements and show the ability of the model to reproduce the main features of the mechanical, hydraulic and thermal behaviour of the system. Finally, those results are interpreted in the light of thermo-plasticity of unsaturated soils, which reveals the highly coupled and non-linear characters of the encountered processes.