The soils in the eastern region of Qinghai, China, are characterized by typical unsaturated loess with poor engineering properties, rendering them susceptible to geological disasters such as landslides. To investigate the mechanical properties of these soils, triaxial and direct shear tests were conducted, followed by simulations of deformation and stability under freeze-thaw cycles using the discrete element software MatDEM, based on the experimental data. The findings indicate that (1) the stress-strain curves from both tests typically exhibit weak strain-softening behavior, with increased matric suction enhancing shear strength; (2) in the direct shear test, both cohesion (c) and the angle of internal friction (phi) rise with matric suction, whereas in the triaxial test, cohesion increases while phi decreases; and (3) an increase in freeze-thaw cycles results in a gradual decline in slope safety factor, though the rate of decline diminishes over time. Additionally, initial water content and slope gradient changes significantly affect slope stability. These insights are essential for geohazard risk assessment and the formulation of prevention and control strategies in Qinghai and similar alpine regions.

Block stone structural layers are commonly utilized in roadbed projects within permafrost areas. However, due to significant temperature fluctuations and frequent freeze-thaw cycles, some of these rock layers have weathered and fractured. Continuous weathering of these rocks results in the block stone embankment gaps becoming clogged, reducing macropore and porous media areas. Consequently, the convective heat transfer function of the block stone roadbed diminishes, failing to adequately protect the frozen soil. This study aims to assess whether recycled weathered rock materials, modified with cement, can match the mechanical properties and damage expansion characteristics of unweathered rocks. Weathered sandstone was selected for modification into rock-like materials. Detailed investigations were conducted into their physical and mechanical properties, alongside damage propagation characteristics following freeze-thaw cycles. Compared to red sandstone, weathered sandstone rock materials exhibit significantly enhanced compressive strength, aligning freeze-thaw damage models with red sandstone rock characteristics, thereby affirming the feasibility of reusing weathered sandstone rocks.