Insights into the shallow landslide mechanism of expansive soil slope induced by freeze–thaw cycles and snowmelt infiltration

For rigorous understanding the shallow landslide mechanisms and deformation characteristics of expansive soil slopes, a comprehensive in-situ monitoring platform is established. Triaxial creep tests and microstructure analysis with scanning electron microscopy are also conducted on expansive soil samples obtained from Binxi station. Field monitoring data indicates that freeze–thaw (F–T) cycle and snowmelt infiltration significantly increase the creep deformation of expansive soil slope during spring melting period. Due to the influence of F–T cycle and snowmelt infiltration, more soil grains are involved in the shear deformation contributing to a large, localized shearing. Additionally, the microstructural analysis shows that F–T cycle influences the relationship between expansive soil grains that gradually change from face–face contact to point–face contact or edge–edge contact form. The shallow landslide mechanisms of expansive soil slope are revealed from creep deformation and microstructure characteristics of soils after the F–T cycle and snowmelt infiltration, which can be summarized into two stages, namely, the snowfall accumulation state and snow melt-shallow infiltration stage. These results can serve as a good reference for the prevention of expansive soil slopes in seasonally frozen regions.