FEM analyses for influences of pressure solution on thermo-hydro-mechanical coupling in porous rock mass

Abstract

The model of pressure solution for granular aggregate was introduced into the FEM code for analysis of thermo-hydro-mechanical (T-H-M) coupling in porous medium. Aiming at a hypothetical nuclear waste repository in an unsaturated quartz rock mass, two computation conditions were designed: 1) the porosity and the permeability of rock mass are functions of pressure solution; 2) the porosity and the permeability are constants. Then the corresponding numerical simulations for a disposal period of 4 a were carried out, and the states of temperatures, porosities and permeabilities, pore pressures, flow velocities and stresses in the rock mass were investigated. The results show that at the end of the calculation in Case 1, pressure solution makes the porosities and the permeabilities decrease to 10%–45% and 0.05%-1.4% of their initial values, respectively. Under the action of the release heat of nuclear waste, the negative pore pressures both in Case 1 and Case 2 are 1.2–1.4 and 1.01–1.06 times of the initial values, respectively. So, the former represents an obvious effect of pressure solution. The magnitudes and distributions of stresses within the rock mass in the two calculation cases are the same.