Coupled thermal–hydraulic–mechanical–chemical modeling for permeability evolution of rocks through fracture generation and subsequent sealing

Abstract

The coupled THMC model, Interface for Pressure Solution Analysis under Coupled Conditions, IPSACC, that was proposed by the authors and can describe the long-term evolution in rock permeability due to mineral reactions (i.e., pressure solution and free-face dissolution/precipitation) within rock fractures, was upgraded in the present study by incorporating the processes of fracture initiation/propagation. The remarkable characteristic of the proposed model is its ability to simulate the generation of fractures and the mineral reactions within the generated fractures as well as the subsequent changes in permeability. The proposed model was applied to predictions of the long-term changes in the permeability of rock located near high-level radioactive waste within a geological repository. The predicted results revealed that fractures were generated near the disposal cavity and that the permeability of the damaged zone increased significantly more than that of the intact rock during the excavation, while the permeability in almost the entire damaged zone decreased by about one order of magnitude due to pressure solution at the contacting asperities within the rock fractures after setting virtual radioactive waste into the disposal cavity. Overall, it was clarified that the proposed model is capable of calculating the permeability evolution of rock through fracture generation and subsequent sealing due to mineral reactions at the actual field scale. Thus, the potential for using the proposed model to examine the long-term performance of natural barriers for delaying the transport of radionuclides has been shown.

Effect of Leaching Behavior on the Geometric and Hydraulic Characteristics of Concrete Fracture

“…The leaching method used was relatively simple and the proposed model is straightforward because the interactions of normal pressure in the leaching processes are omitted; these are, however, applicable to open fracture without normal pressure in concrete structures. Generally, when considering a closed fracture under normal pressure, the phenomenon of pressure leaching may occur and be significant [44,[55][56][57]. This phenomenon will make the concrete fracture leaching model more complicated but is a longstanding inspiration in the field of rock engineering [57][58][59].…”

Guest Editorial to the CouFrac 2018 Special Issue Coupled Thermal-Hydro-Mechanical-Chemical Processes in Fractured Media: Microscale to Macroscale Numerical Modeling

“…In order to study the long-term evolution in rock permeability due to mineral reactions (i.e., pressure solution and free-face dissolution/precipitation), Ogata et al [7] developed a new model that considers fracture initiation and propagation as a result of the coupled THMC processes and applied it to analyze long-term changes in the permeability of rock at a high-level radioactive waste repository. The results show that pressure solution at the contacting asperities of generated fractures can reduce permeability in the excavation damage zone by one order of magnitude.…”

Reactive Solute Transport in Fracture Media: the Role of Mineral Precipitation

“…In the subsequent study, THMC coupling analysis model was proposed to investigate the effect of temperature [15] . Ogata et al [16] further improved the model by integrating the fracture initiation and propagation, and analyzed the mineral reaction and permeability evolution during the fracture propagation process. However, the existing models focus more on the effect of mineral dissolution and precipitation in the fracture cavity on the fracture permeability and aperture, while there is less research on the solute transport characteristics.…”