Water and salt migration and deformation mechanism of sodium chloridesoil during unidirectional freezing process

The mechanism of water and salt migration in the freezing process has long been a hot spot in the study of frozen soil. The water and salt transport processes and the deformation of soil are studied through the unidirectional freezing experiments. The results show that the deformation of soil with the initial salt content decreases significantly compared with that of desalinized soil, and the salt has a strong impact on the accumulation of water in the frozen fringe, and it can mitigate the frost heave of soil in the freezing process. Supplied with different concentrations of NaCl solution, the deformations of the samples are consistent in the early stage. With the accumulation of salt at the freezing front, the driving force of moisture migration is not so sufficient during the subsequent period when the frost heave decreases significantly. Based on the properties of the solution, a model is established to describe the water and salt migration and deformation in the freezing process, where the influence of salt on the freezing temperature and unfrozen water content are considered. The calculated results illustrate that the proposed model can reflect the laws of temperature, water, salt and deformation in the freezing process well, and it will provide a theoretical basis for understanding the deformation mechanism of saline freezing soil.