Numerical Modeling of Coupled THMC Processes for Predicting Fluid Flow and Transport Behavior Within Fractured Rocks

We improved our thermal-hydraulic-mechanical-chemical (THMC) simulator to predict the long-term permeability change of the fractured rocks. The model evaluates the influence of the geochemical reaction on the evolution of the permeability in fractured rocks by considering pressure solution in detail. Pressure solution that occurs at both grain contacts and contacting asperities within fractures was incorporated in the model. By using the developed THMC numerical model, long-term prediction of rock permeability was conducted by replicating the subsurface environment near the radioactive waste repository. As a result of the analyses, the permeability decrease by two orders of magnitude smaller than the initial value occurs due to pressure solution at contacting asperities within fractures in the EDZ area. In carrying out radioactive waste disposal, it is apparent that pressure solution within the fractures has significant impact on minimizing the increase of the permeability in EDZ area.