Coupled THMC Modelling by Considering Damage Theory for Predicting Permeability Change in Fractured Rocks

Ogata, Sho (Kyoto University) | Yasuhara, Hideaki (Ehime University) | Kinoshita, Naoki (Ehime University) | Kishida, Kiyoshi (Kyoto University)


ABSTRACT: We developed a coupled thermal-hydraulic-mechanical-chemical (THMC) simulator, iPSACC (interface for Pressure Solution Analysis under Coupled Conditions) that can consider the coupled processes including change of physical properties of the rocks due to the cracking by incorporating elastic damage theory. Especially, modeling the relationships between geochemical reactions such as pressure solution within rock fracture and rock damage is most important characteristic of this simulator. By using the developed simulator, long-term prediction of rock permeability was conducted by assuming subsurface environment near the radioactive waste repository. The predictions show that in EDZ many fractures occur near the disposal cavity and permeability increases in damaged zone during the excavation, and after excavation the permeability of the damaged zone decreases with time due to pressure solution at contacting asperities within fractures. It is concluded that pressure solution within the fractures has significant impact on the change of the permeability in EDZ area by cavity excavation.