Development of Coupled Thermal-Hydraulic-Mechanical-Chemical Models for Predicting Rock Permeability Change

摘要

This article is a summary of the author’s thesis (Ogata, 2019) which won the best doctoral thesis award from the Japanese Society for Rock Mechanics (JSRM). Coupled thermal-hydraulic-mechanical-chemical (THMC) models were developed for realistically estimating the long-term permeability evolution within rock enhanced by mineral reactions such as pressure dissolution. Two coupled THMC models that incorporate the pressure dissolution within the rock matrix and rock fractures were firstly developed, and the validity of the models was examined by replicating the experimental data. Subsequently, a coupled THMC model that can consider the mineral reactions within dual-porosity media was proposed and applied to predict the long-term evolution of the permeability of fractured rock in a geological repository of high-level radioactive waste (HLW). The results revealed that the pressure dissolution within rock fractures has a critical influence on the permeability evolution of fractured media. Finally, a THMC coupled model incorporating the damage theory to consider the influence of fracture generation was developed, and the consecutive processes in rock permeability evolution, from fracture generation to subsequent sealing during the period of the geological disposal of HLW, were shown.