An Analysis of Influencing Factors for Vapour Transfer in Freezing Soils in High-filling Engineering

Canopy effect has been paid more and more attention in high-filling engineering in cold and arid regions of China. Vapour transfer is considered as the main cause of canopy effect in freezing soil in the literature. However, the influencing factors of vapour transfer in freezing soils have not been systematically analyzed in the literature. Based on the coupled heat and mass transfer model proposed by the authors, the effects of hydraulic parameters and environmental factors on vapour transfer in freezing soils will be analyzed in this paper. The results show that the effects of the hydraulic parameters, such as the fitting parameters of the soil water characteristic curve (SWCC) and the saturated hydraulic conductivity, on the vapour transfer and the total water content are significant, even if the values of these parameters vary within a quite small range. The temperature gradient, the cooling rate, the water flux at the top and the sealing conditions at the bottom can also lead to an increment of the total volumetric water content. Therefore, these hydraulic parameters and environmental factors can all promote vapour transfer under suitable conditions. The effects of the terms related to vapour transfer in the governing equations on the total water volumetric content are also analyzed. In total, the water increment caused by vapour transfer is large, which can then cause frost damage in silt. The research results in this paper are helpful to understand the influence of factors for canopy effect and also have a great significance for guiding the design and maintenance of high-filling engineering.