FEM analyses for influences of stress corrosion and pressure solution on THM coupling in dual-porosity rock mass

Abstract

With the models of stress corrosion and pressure solution, by Yasuhara et al., two computation conditions were designed for a hypothetical nuclear waste repository in an unsaturated dual-porosity rock mass: (i) the fracture apertures are changed with the stress corrosion and pressure solution (the porosity of rock matrix is also a function of stress); (ii) the fracture apertures and the porosity of rock matrix are constants. Then the corresponding two-dimensional FEM analyses for the coupled thermo- hydro-mechanical processes were carried out, and the states of temperatures, rates and magnitudes of aperture closure, pore pressures, flow velocities and stresses in the rock mass were investigated. The results show the followings: The aperture closure rates caused by stress corrosion are almost six orders higher than those caused by pressure solution, and the two kinds of closure rates climb up, then decline, furthermore tend towards stability; the fracture apertures decrease from the original value and tend towards the residual value, and the contact-area ratios of asperities increase also from the original value and tend towards the nominal value; when the effects of stress corrosion and pressure solution are considered, the negative fracture pressures in near field rise very highly; the differences between the magnitudes and distributions of stresses within the rock mass in two calculation cases are very small.