Numerical investigation on vapor transfer in unsaturated soil during freezing

Abstract

This paper presents a new approach for modelling moisture migration in unsaturated freezing soil, in which the evaporation and condensation processes of water vapor are taken into account. Comparing predicted date with the measured result of one-dimensional soil freezing test shows proposed model is capable of effectively simulating the freezing process of unsaturated soil. Parametric analysis is carried out to clarify the role of vapor in moisture migration during freezing, which shows that vapor largely contributes to ice formation, occupying around 10%~60% of total water fluxes in an unsaturated and closed system. The result also shows that, total ice content and vapor flux percentage increases and decreases with the increase of initial water content, respectively. The higher the temperature gradient, the greater the vapor flux percentage, while the total ice content is insensitive to the temperature gradient. Peak values exist for the variations of total ice content and vapor flux against saturated hydraulic conductivity.