Abstract: In order to study the interaction mechanism between liquid-phase suction and solid-phase ice pressure in frozen soil / rock, the theoretical ice pressure equations under different boundary conditions are first unified according to the fundamental thermodynamics. Then, by combining the generalized Clapeyron equation and the Gibbs-Thomson equation, the freezing temperature equation of liquid phase water at curved interface is given on the basis of interpretation of the physical significance of liquid-phase suction and solid-phase ice pressure. Finally, the freezing temperature equation is introduced into the frozen capillary model, and the liquid-phase suction equation is substituted into Darcy's law to verify the action mechanism of solid-phase ice pressure and liquid-phase suction respectively. The results show that: 1) The theoretical ice pressure in equilibrium state is only linearly related to temperature and has nothing to do with the boundary conditions. 2) The liquid-phase suction stems from the difference between the theoretical suction and the offset factor of solid-phase ice pressure, and it is the unified driving force for water migration, and when the solid-phase ice pressure approaches the theoretical ice pressure, the liquid-phase suction tends to zero. 3) The solid-phase ice pressure is an absolute pressure, which can offset the liquid-phase suction, while the liquid-phase suction is a relative suction and cannot offset the solid-phase ice pressure. 4) The total pressure in the pores is only the solid-phase ice pressure and it can reach the theoretical ice pressure in equilibrium when the capillary is frozen, so it follows the formation mechanism of segregation ice by "ice pressure method". This research reveals the interaction mechanism between liquid-phase suction and solid-phase ice pressure in frozen soil / rock, which has high theoretical value and scientific significance for improving the existing frost heave theory.

Key words: liquid-phase suction, solid-phase ice pressure, theoretical ice pressure, curved interface, freezing temperature