Development of multi-physics numerical simulator for describing coupled thermal-hydraulicmechanical-chemical processes within fractured rocks

Abstract

When investigating the long-term performance of various rock engineering projects, such as the geological disposal of high-level radioactive waste (HLW), enhanced geothermal system (EGS), it is essential to accurately predict the permeability evolution within fractured rocks due to coupled thermal-hydraulic-mechanical-mechanical (THMC) phenomena including fracture generation and subsequent geochemical creep. In this paper, we introduced our coupled THMC simulator that can explicitly introduce the fracture surfaces to describe the permeability change within fractured rocks as realistically as possible. The numerical results of long-term change in rock permeability during a disposal period of HLW computed by our simulator, showed that the permeability reduction with time was observed only within specific fractures where the geochemical creep (i.e., pressure dissolution) had been activated depending on the heterogeneous properties of each fracture. It may suggest that our simulator has a possibility to reveal the detailed spatial distribution of permeability within rock masses containing the newly generated fractures.