关键词: 应力腐蚀, 压力溶解, 双重孔隙介质, 热-水-应力-迁移耦合, 有限元分析

Abstract: On the basis of using the models of stress corrosion and pressure solution established by Yasuhara et al, the solute concentration field is introduced into the 2D FEM code of thermo-hydro-mechanical coupling analysis for dual-porosity medium developed by the authors. Aiming at a hypothetical nuclear waste repository in unsaturated rock mass from which there is a nuclide leak, two computation conditions are designed: (1) the fracture apertures are changed with the stress corrosion and pressure solution (the porosity of intact rock is also a function of stress); (2)the fracture apertures and the porosity of intact rock are constants, then the corresponding two-dimensional numerical simulation for the coupled thermo-hydro-mechano-migratory processes is carried out; and the states of temperatures, rates and magnitudes of aperture closure, pore and fracture pressures, flow velocities, nuclide concentrations and stresses in the rock mass are investigated. The results show that 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 and then decline, furthermore tend towards stability; when the effects of stress corrosion and pressure solution are considered, the negative fracture pressures in near field rise very high; the fracture aperture and porosity decrease in the case 1, so the relative permeability coefficients reduce; therefore the nuclide concentrations in pore and fracture in this case are higher than those in case 2 because the effects of negative pore and fracture pressures on the stress balancing are not reckoned in; the magnitudes and distributions of stresses within the rock mass in two calculation cases are almost the same.

Key words: stress corrosion, pressure solution, dual-porosity medium, thermo-hydro-mechano-migratory coupling, FE analysis