Moisture movement in freezing soils under constant temperature condition

In saturated soils, migration of pore water during freezing can be treated as a potential flow problem, and the moisture movement can be idealized by a partial differential equation describing pore water pressure. The equation was solved analytically under constant temperature condition at the boundary by assuming an equation which expresses a relation between velocity of frost penetration and the potential at freezing front. Then the equation of heat conduction was solved by a finite difference appraoch, in which the variation of thermal constants due to moisture movement and freezing was taken into account. In the numerical analysis an empirical equation was used to obtain the potential at the freezing front. Freezing tests were also executed on volcanic ash soils to determine the variation of pore water pressure and temperature during freezing. The results of the laboratory tests were compared with the results of the numerical analysis. Distribution of temperature, water content, depth of frost penetration and heave amount were well approximated by the analysis. The mechanism of frost heave in saturated soils at rapid rates of freezing can be well descibed by this simple model proposed in this study.