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Salt expansion and frost heave are the main diseases of salted frozen soil roadbeds. Salt swelling and frost heave disease are closely related to the salted soil water–salt migration, temperature variation, and salt crystallization amount change. This article establishes a coupled model of water, heat, and salt fields based on the capillary model and the unfrozen water characteristic curve. The study shows that the different initial moisture contents have minimal effects on the location of soil salt migration and aggregation. The different initial salt concentrations have a substantial effect on the soil water–salt migration aggregation position; when the concentration of sodium sulfate increases, different from chloride saline soils, the position of the freezing front fluctuates up and down over time. The water–salt migration and aggregation are smaller in the closed condition, where they are reduced by 38% and 20%, respectively.

Due to the fact that the permeability coefficient of salinized frozen soil is difficult to measure through experimental test, this paper develops a model of the permeability coefficient of salinized frozen soil by using SFCC curves, which takes into account the effects of velocity slip on pore wall and seepage of unfrozen water film. This model is on the basis of capillary bundle model, and combines with phase diagram theory of water-salt binary system. For the silty clay from Qinghai-Tibet Plateau and silts from Onedia, the permeability coefficient fluctuation vs. temperature is calculated using the model. The estimated calculations of the permeability coefficient model were all found to be in good agreement with the experimental data by comparison. Additionally, the variation trend of permeability coefficient of NaCl, Na2SO4, and Na2CO3 type saline soils containing different salt contents is examined. The results indicate that before saline soils freeze, NaCl does not crystallize and thus has little impact on the permeability coefficient, whereas Na2SO4 and Na2CO3 both crystallize and block the pores, the permeability coefficient decreases with decreasing temperature. Once the saline soils have frozen, the freezing temperature has a larger impact on the permeability coefficient. During the early stage of freezing, the lower the freezing temperature is, the larger the permeability coefficient is. In the late stage of freezing, the permeability coefficients with various salt contents tended to be the same.

The Nyexon Rock Avalanches in the southern Qinghai-Tibet Plateau is a huge scale earthquake-induced slope disaster in the Holocene, the accumulation area has distinct sedimentological characteristics, which is of great significance for studying the intrusion and restraint mechanism during long-distance transportation of large rock avalanches or debris avalanche. This long-distance transportation induced a series of landform types, such as ridges, hills, and ravines; they are widely distributed in all areas and extensively developed shear zones, jigsaw cracks, and other structures within the sedimentary structure. With the analysis of DEM data and geological survey, two main types of basement structures and their transition relationships are distinguished; they play an essential role in the restraining bottom during rock avalanches. In the sedimentary structure, the block facies and mixing facies occupy the main body of the deposition from the center to the distal area. Under the basement restriction, mixing facies are formed between the bottom of the sedimentary layer and the basement sedimentary structure; the shear band is mainly developed along with the mixing facies and basement facies, which is accompanied by basement liquefaction and rheology. A sedimentary facies model is established based on the sedimentary structure sequence of the Nyexon Rock Avalanches transportation. After analyzing the failure mechanism of the rock avalanches, it is believed that in the initial stage of failure, the rock avalanches is transformed into a particle flow that is similar to the debris avalanche, which is restrained by the basement structure and lateral bound; then, an accumulated obstacle highland is formed in the central area after deceleration, making the transportation of the main fluid to deflect quickly.