Numerical analysis of coupled hydro-mechanical and thermo-hydro-mechanical behaviour in buffer materials at a geological repository for nuclear waste: Simulation of EB experiment at Mont Terri URL and FEBEX at Grimsel test site using Barcelona basic model

Abstract

We investigated the applicability of a thermo-elasto-plastic model using a TOUGH2-MP/FLAC3D simulator to reproduce the coupled hydro-mechanical behaviour at the engineered barrier emplacement experiment in Opalinus Clay and the coupled thermo-hydro-mechanical behaviour at the full-scale engineered barrier experiment in a crystalline host rock, as part of the DECOVALEX-2019 project Task D. In the numerical models, we adopted Darcy's law, Fick's law, and Fourier's law for the advective flux of fluid, vapour diffusion, and conductive heat flux, respectively. We also used the mechanical constitutive law, which explicitly considers the effects of temperature, pore pressure, suction, and strain changes using the elastic model and the Barcelona basic model. In general, the numerical models in the simulator successfully represented the coupled behaviour in bentonite buffer materials at the two long-term in situ experiments in terms of evolution and spatial distribution for temperature, relative humidity, total stress, and displacement. The performance of the models for the dismantling of the in-situ experiments is globally satisfactory compared with the post-mortem results for saturations, water contents, and dry density.