Thermo-hydro-mechanical behavior of clay rock for deep geological disposal of high-level radioactive waste

In the context of deep geological disposal of radioactive waste in clay formations, the thermo-hydromechanical (THM) behavior of the indurated Callovo-Oxfordian and Opalinus clay rocks has been extensively investigated in our laboratory under repository relevant conditions: (1) rock stress covering the range from the lithostatic state to redistributed levels after excavation; (2) variation of the humidity in the openings due to ventilation as well as hydraulic drained and undrained boundary conditions; (3) gas generation from corrosion of metallic components within repositories; and (4) thermal loading from high-level radioactive waste up to the designed maximum temperature of 90 degrees C and even beyond to 150 degrees C. Various important aspects concerning the long-term barrier functions of the clay host rocks have been studied: (1) fundamental concept for effective stress in the porous clay-water system; (2) stress-driven deformation and damage as well as resulting permeability changes; (3) moisture influences on mechanical properties; (4) self-sealing of fractures under mechanical load and swelling/slaking of clay minerals upon water uptake; (5) gas migration in fractured and resealed claystones; and (6) thermal impact on the hydro-mechanical behavior and properties. Major findings from the investigations are summarized in this paper. (C) 2018 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V.