Simulation of the hydro-mechanical behaviour of bentonite seals for the containment of radioactive wastes

Geological disposal of radioactive wastes relies on a multiple barrier system to provide long-term containment and isolation of the wastes. The excavation of the repository creates openings and disturbed zones in the host rock formations that need to be properly sealed. Bentonite-based materials are being considered worldwide as a preferred type of sealing material. The French Institute for Radiation Protection and Nuclear Safety (IRSN) has led an experimental program consisting of a series of laboratory and large in-situ experiments in order to assess the hydro-mechanical behaviour of bentonite seals. The experiments consisted of the forced re-saturation of pre-fabricated blocks of bentonite-sand mixture, with technological voids between bentonite seals and the walls of the steel cell (in the laboratory tests) and the host rock (in the in-situ experiment). Relative humidity and total stress were monitored during both tests. The authors developed a mathematical model to simulate the above experiments within the framework of poromechanics, with the inclusion of partial saturation characteristics and swelling potential in order to simulate the behaviour of the bentonite-based material. The model results were in good agreement with the experimental measurements for relative humidity and swelling stresses. The model also predicted the closure of technological voids and gaps due to swelling. Permeability of the material remains low, although an overall permeability increase is predicted as the material swells.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author