Water flow and heat transport including ice/water phase change in porous media: Numerical simulation and application

According to the basic law of water flow and heat transfer in porous media under freeze/thaw condition, based on the theories of continuum mechanics, thermodynamics and segregation potential, the governing equations for thermo-hydro (TH) coupling model are established. These equations include not only the effects of thermal conductivity, latent heat of phase change and the seepage velocity on temperature distribution, but also the effects of water flow in porous resulted by Soret effect and segregation potential on seepage velocity and water pressure distribution. Compared with the famous TH coupling laboratory test conducted by Mizoguchi, it was found that the presented TH coupled model predicts the freezing process in porous media well and satisfactorily reflects observed phenomena. Combining this basis and the construction of Galongla tunnel in Tibet of China, the effect of insulation materials is analyzed at first, and then research work is done to study the influence of position, thickness and types of insulation materials on heat preservation effect. The research results indicated that the application of insulation material with 6 cm thickness and 600 m long at the entrance, while 400 m long at the exit of Galongla tunnel can prevent the lining and surrounding rock from freezing–thawing damages effectively.

Research Highlights
► A new thermo-hydro (TH) coupling model are established.
► Effects of thermal conductivity, latent heat of phase change and the seepage velocity on temperature distribution are considered.
► Effects of water flow resulted by Soret effect and segregation potential on seepage velocity and water pressure distribution are considered.
► The presented TH coupled model predicts the freezing process in porous media well and satisfactorily reflects observed phenomena.
► Research work is done to study the insulation materials on heat preservation effect in tunnel.