Coupled thermo-hydro-mechanical-migratory model for dual-porosity medium and numerical analysis

Abstract

A coupled thermo-hydro-mechanical-migratory model of dual-porosity medium for saturated-unsaturated ubiquitous-joint rockmass was established, in which the stress field and the temperature field were single, but the seepage field and the concentration field were double, and the influences of sets, spaces, angles, continuity ratios, stiffnesses of fractures on the constitutive relationship of the medium were considered. Also, the relative two-dimensional program of finite element method was developed. Taking a hypothetical nuclear waste repository as a calculation example, the case in which the rockmass was unsaturated dual-porosity medium and radioactive nuclide leak was simulated numerically, and the temperatures, negative pore pressures, saturations, flow velocities, nuclide concentrations and principal stresses in the rockmass were investigated. The results show that the negative pore pressures and nuclide concentrations in the porosity and fracture present different changes and distributions. Even though the saturation degree in porosity is only about 1/10 that in fracture, the flow velocity of underground water in fracture is about three times that in porosity because the permeability coefficient of fracture is almost four orders higher than that of porosity. The value of nuclide concentration in fracture is close to that in porosity.