Thermo-Hydraulic-Mechanical Coupling Analysis on Heating Test in Unsaturated Ground

In relating to the feasibility of geological disposal of high-level nuclear waste, numerous experimental investigations and numerical simulations have been conducted to guarantee the safety and the efficiency of the geologic sealing structure in a long time period. The thermo-hydraulic-mechanical (THM) coupling problem is considered as one of the most important factors in evaluating the whole process of the geological disposal of nuclear waste. In this paper, a heating experiment (Munoz, 2006) has been simulated to investigate the THM problem in the unsaturated ground using a program of finite element method (FEM) named SOFT. The program is based on the finite element-finite difference (FE-FD) scheme in fully coupled soil-water-air, three-phase field theory under non-isothermal conditions. In the simulation, a rational constitutive model that takes Bishop-type effective stress and the degree of saturation as the state variables, is adopted. The model can describe the behavior of saturated and unsaturated soil automatically. According to the simulation results, it is known that the present simulation can properly describe the THM behaviors observed in the heating experiment such as the hydration of water, the evolution of temperature, and the evolution of pore water pressure to some extent.