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• 10th FTC was the threshold number to affect the structural stability of the soil. • Increasing SSC (<0.8 %) did not constantly reduce the water stability of the soil. • The effect of FTC on soil erodibility was more significant than SSC. • Freeze-thaw microscopic deterioration mechanism in soil erodibility was explored. Soda saline-alkali soil, dominated by NaHCO 3 , has complex engineering properties that change with external water, heat, and salt, making it prone to water erosion. By destroying soil microstructure, freeze-thaw (F-T) action can potentially enhance soil erodibility and provide water erosion material. Therefore, this work examined the freeze-thaw erosive properties and microstructural evolution mechanisms of soda saline-alkali soil. Disintegration tests and a series of microscopic tests examined the impacts of freeze-thaw cycles (N = 0, 1, 5, 10, 30, 60) and soluble salt content (η = 0.4 %, 0.8 %, 1.2 %, 1.6 %, 2.0 %) on the soil erodibility index (disintegration rate). The results demonstrated that F-T action continued to weaken the disintegration resistance of the saline soil. Moreover, this trend relatively stabilized after 10 F-T cycles. Soluble salt content had a two-phase impact on the saline soil disintegration. Increased salt content below 0.8 % improved erosion resistance, but salt content above 0.8 % accelerated the soil erosion. According to the Gouy-Chapman diffuse double layer (DDL) theory, the variation in the thickness of DDL induced by higher sodium ion contents and lower sodium ionic valence were deemed as the main causes. When the salt content increased from 0.8 % to 2.0 %, the disintegration rate increased by 49.40–71.43 %. Microscopic results showed that sequential F-T cycles decreased intra-aggregate pores (<4 μm) and increased inter-aggregate pores (>4 μm). This mechanism was attributed to the unfrozen water migration and ice segregation due to the cryo-suction process during the freezing process. Correlation analysis indicated that soil microstructure with a bimodal characteristic dominated the erodibility index. The effect of F-T action on soil erodibility was more significant than the soluble salt content, with both impacted saline soil erodibility by affecting pore distribution characteristics and soil aggregate formation, respectively. These findings may assist soda saline-alkali soil salinity prevention and control of saline soil erosion in seasonally frozen regions globally. [ABSTRACT FROM AUTHOR]

[Display omitted] • 1. The deformation and land surface temperature data were integrated for analysis. • 2. The canal slopes experienced temperature-derived spatially differential deformation. • 3. The mechanisms that the shady slope was prone to landslides were revealed. Hydraulic engineering has positive effects on agricultural production and soil desalination. However, freeze–thaw cycles can cause instability in canal slopes, emphasizing the need for effective deformation monitoring. Using Sentinel-1B data acquired from November 2017 to August 2019 and applying the small baseline subset (SBAS) InSAR method, two unstable canal segments with vertical deformation rates exceeding –40 mm/year were identified in Songyuan, Northeast China. The canal slopes uplifted in winter and experienced accelerated subsidence in spring, with the shady slope experiencing a deformation rate approximately 10 mm/year faster than the sunny slope. Further investigation, integrating Landsat–8 data collected from November 2017 to August 2019, revealed that the shady slope received less thermal radiation than the sunny slope, with an average annual temperature difference on the land surface of approximately 1 ℃. In winter, the saline–alkali soil particles formed a thick unfrozen water film, which, driven by temperature and soil–water gradients, migrated towards the freezing front, froze, and caused soil frost heave. The shady slope experienced longer freezing periods and deeper frozen depths, up to 240 cm, causing more unfrozen water migration and greater uplift deformation than the sunny slope. In spring, as temperature rose, the soil thawed from the surface downward. Notably, the shady slope thawed at a slower rate than the sunny slope, forming a frozen lens near a depth of 100 cm. Frozen lens acted as a barrier for meltwater infiltration, impeding the dissipation of pore water pressure, making the shady slope prone to surface landslides. The integration of multiple data sources is beneficial for identifying deformation risk in hydraulic engineering. [ABSTRACT FROM AUTHOR]