Abstract: The behavior of clay liner at the bottom of landfill site plays an important role in the effective performance of its long-term seepage and pollution control. In view of the high saturation state of soil barrier in the actual yard, the liquid phase (pore water) and gas phase (block bubble) are considered as mixed fluid in this study. By establishing soil stress equilibrium equations, mixed fluid mass conservation equations, and solute mass conservation equations, the interaction mechanism of soil particle, pore fluid, solute is considered comprehensively; and a hydraulic- mechanical-chemical fully coupled model for solute transport in high saturated clay liner is presented. The model can directly and accurately solve the deformation of soil layer, mixed fluid pressure and solute distribution with time and space. The multi-field coupled finite element analysis software COMSOL is used to carry out numerical simulation on the model; the results show that the model results are in good agreement with the results obtained by Peters. Meanwhile, the existence of compressible gas in the clay liner delayed the dissipation of the excess pore fluid pressure, increased the settlement of the soil layer, and had a delayed effect on solute transport in the clay liner.

Key words: hydro-mechanical-chemical coupling, high saturation, mixed fluid, solute transport