Coupled thermo-hydro-gas-solute modeling on layered unsaturated soil

A coupled thermo-hydro-gas-solute modeling is presented to investigate their migrations in layered unsaturated soil under unsteady conditions based on thermal and mass transfer in porous media. The effects of non-convective fluxes of gas and liquid phases are considered in the mass and energy conservation equations. The solutions of the pore non-convective fluxes, the dry gas and water vapor non-convective fluxes are derived. The effects of salt non-convective fluxes, gas phase non-convective fluxes and thermal conductivity of each component on the energy conservation of layered unsaturated soil are considered. A mathematical model for the one-dimensional unsteady-state problem is established with the state equations using Laplace transform and solved using the shooting method to obtain the frequency domain solution which is transformed into the time domain solution. A series of laboratory experiments were conducted to verify the accuracy of the proposed theoretical model. The accuracy of the proposed model is also verified by the experimental and numerical results in the literature. The reasonable agreements verified the accuracy of the proposed coupled thermo-hydro-gas-solute model. Parametric studies are conducted to investigate the effects of the interlayer on the behavior of the thermo-hydro-gas-solute coupling in layered unsaturated soil.