Affected by the complex engineering environment in cold regions

it is difficult to predict the water and heat states of saline soil

and the research of the interaction process among water

heat

and salt is the core and foundation of frozen soil to reveal the mechanism of frost heave and salt heave. In this study

the crystallization temperature range of sodium sulfate saline soil was obtained through indoor test

the water-heat-salt interaction calculation model of saline soil during a cooling process was established

and the accuracy of the calculation model was verified. Results show that the crystallization temperature varied with initial salt content of soil samples; the salt crystallization for the soil samples with high initial salt content was at positive temperature

while that for the soil samples with low initial salt content was at negative temperature. The water-heat-salt interaction calculation model proposed based on the physical phenomena could effectively predict the variations of temperature

unfrozen water content

amount and distribution of sodium sulfate crystallization during a cooling process. The salt would migrate through the sodium sulfate saline soil when the crystallization occurred during a cooling process

which could increase the salt concentration and the amount of crystallization. Besides

the salt migration ability varied with initial salt content; the soil samples with high initial salt content had more salt crystallization in positive temperature range

and those with low initial salt content had strong salt migration ability in the temperature range of -4 ℃ and -6 ℃.