Abstract: To unify the source power of water migration, a pressure-suction element model of film water is constructed on the basis of the film water hydraulic driving force model and the surface adsorption force model. Model analysis shows that under the dual action of net suction and actual liquid pressure (or theoretical suction and actual ice pressure), the surface adsorption force can be generated, which drives the tangential migration of water along the surface of the substrate. In view of the fact that the surface adsorption force has nothing to do with the boundary conditions, it is suitable for any form of unfrozen water, and it is the unified source power of water migration. Based on this, the pressure?suction element model is introduced into the frozen fringe theory, and it is found that the actual ice pressure determines the temperature and position of the segregated ice formation, the theoretical suction determines the direction of water migration, and the surface adsorption force determines the velocity of water migration. Finally, substituting the main parameters from the Konrad (1980) test into the surface adsorption force equation, it is found that even if the temperature gradient increases from 0.1 ℃ /cm to 0.67 ℃ /cm, the sample height increases from 6.4 cm to 28 cm, as long as the segregation freezing temperature and the overburden pressure keep unchanged, the surface adsorption force is always constant at ?23 kPa, which verifies the correctness of the surface adsorption force equation. In short, the development of this model has important theoretical value and practical significance for improving the existing frost heave theory and guiding engineering practice.

Key words: film water, pressure?suction element model, surface adsorption force, segregated ice, water migration velocity