A new method for estimating salt expansion in saturated saline soils during cooling based on electrical conductivity

Salt expansion is known as a type of soil deformation induced by salt crystallization. In order to reveal the development of salt expansion or salt crystallization in saline soils during the freezing process, we propose a new model for estimating the variation of the pore solution concentration according to the strong dependence between electrical conductivity and concentration. Moreover, the proposed model can further calculate the crystallized salt content, salt expansion, and frost heave during the cooling process. Meanwhile, a series of experiments are conducted on the unfrozen water content, electrical conductivity, and deformation of saline soil with different salinity. The results show that the deformation of saline soil undergoes three stages and increases rapidly in the second stage. Meanwhile, the soil deformation can be well predicted by our model and has similar characteristics with the salt expansion calculated by our model during the cooling process. Salt expansion mainly occurs in the latter two stages for the saline soil with low salt content and throughout the process for the saline soil with high salt content. Meanwhile, the contribution of the ultimate salt expansion to the soil deformation increases significantly with the increase of the salt content, which conforms to the parabolic relationship. Thus, the prediction of crystallized salt by this model is conducive to monitoring salt expansion in the field and laboratory, and further to reveal the mechanism of salt expansion in saline soils.