Effects of Snowmelt and Rainfall Infiltration on the Water and Salt Migration of Earthen Sites during Freeze-thaw Process

The precipitation accelerates the migration of water and salt in the soil, and aggravates the deterioration of saline earthen sites. Based on the freeze-thaw tests of soil column, the water and salt migration process of earthen sites in northwest China after rainfall in early winter and snowfall in late winter was simulated. The results show that when providing the same quality of rain or snow, the water basically migrated to all parts of the soil column under the initial condition of rainfall infiltration, while the water redistribution range after snowmelt infiltration was just the upper part of the soil column. With the infiltration and evaporation of water, the salt in the surface layer of soil column leached downward and then migrated upward. After 20 freeze-thaw cycles, the contents of SO2–4 and Cl− in the surface layer of soil column under rainfall condition were 89.13% and 99.27% of the initial value, respectively, while those under snowmelt condition were 61.58% and 60.65%, respectively. Snowmelt caused the soil surface to form rolled mud and salt efflorescence, while rainfall led to the formation of crust on the top surface of the soil column and saline zone at the bottom.