Non-isothermal behavior of excavation damaged zone around deep radioactive waste disposal

Abstract

Indurated argillaceous rocks are being investigated as suitable hosts for high-level nuclear waste storage. An important aspect in evaluating the efficiency of waste disposal is the examination of the thermal impact's potential effects on the excavation damaged zone (EDZ) near the field. Increased temperatures could alter the EDZ's crack network, potentially leading to hydraulic failure through thermal pressurization. To accurately understand and model the EDZ surrounding repository cells at higher temperatures, it is essential to account for the coupled influence of thermal-hydraulic-mechanical (THM) phenomena in the constitutive model. Recent studies [1] underline two crucial behaviors in the thermomechanical response of argillaceous rocks: a gradual change in mechanical properties, such as strength and stiffness, with temperature that leads to a more ductile state at higher temperatures; and the occurrence of reversible expansive strains due to temperature increase, which, upon exceeding a specific threshold, turn into irreversible contractive strains.