###### Abstract  
To investigate the effects of freeze-thaw (FT) cycles on the mechanical properties of coarse-grained soil in southeastern Xizang under different moisture contents, this study focuses on coarse-grained soil from a large landslide deposit in Linzhi City, Xizang. FT cycle tests, triaxial shear tests, and numerical simulations were employed to systematically examine the comprehensive impact of varying FT cycles, moisture content, and confining pressure on the soil's mechanical characteristics. The results show that FT cycles significantly affect the stress-strain behavior of coarse-grained soil in southeastern Xizang. The degree of strain softening increased from approximately 11.6% initially to 31.2% after 15 FT cycles, with shear strength decreasing by an average of 31.8%. Specifically, cohesion decreased by 38% to 55% after 0 to 15 FT cycles, and the internal friction angle decreased by approximately 29% to 32%. Additionally, higher moisture content led to more pronounced strain softening and strength degradation, while increased confining pressure effectively mitigated these deteriorative effects. Numerical simulation results indicated that as moisture content increased from 7.6% to 11.6%, the number of FT cycles required to reach the critical instability state decreased from approximately 150 to 106, and finally to only 15, with the maximum equivalent plastic strain increasing from 0.20 to 2.47. The findings of this study provide key mechanical parameters for understanding the formation and evolution of FT landslide disasters in southeastern Xizang and lay a scientific foundation for the assessment and long-term prevention of cold-region geological hazards. undergoing frequent freeze-thaw (FT) cycles. This complex interplay of factors not only accelerates the deterioration of the mechanical properties of native soil and rock masses but also poses potential threats to regional engineering stability. In recent years, driven by the Belt and Road Initiative, southeastern Xizang has witnessed rapid expansion in the development of tourism and major transportation infrastructure [7]. However, the prevalent steep coarse-grained soil slopes and artificial slopes in the region are subjected to cyclic FT effects and severe moisture fluctuations over extended periods, leading to strength degradation, structural damage, and deformation failure--critical geotechnical challenges affecting engineering construction. Therefore, systematically investigating the mechanical evolution of coarse-grained soil under varying moisture conditions and FT cycles in southeastern Xizang holds significant practical engineering importance. The influence mechanism of FT effects on soil's physical properties has been well-established within theoretical frameworks. Extensive research has focused on parameters such as the permeability coefficient [8], void ratio [9], particle gradation [10], and electrical resistivity [11]. [PERSON] et al. [8] conducted FT tests on aeolian soil-bentonite mixtures and found that an increasing number of FT cycles led to a decrease in the permeability coefficient while significantly increasing the compression coefficient ratio. [PERSON] [12] discovered that after experiencing FT cycles, the contact mode of particles in loose fine-grained till changed, and the denser the till, the more pronounced its volumetric contraction and performance deterioration. [PERSON] et al. [13] performed a microstructural simulation analysis of claystone, confirming that FT effects increased the average pore size while reducing the specific surface area. Additionally, their microcomputer-computed tomography scanner seepage simulations revealed the relationship between permeability coefficients and microscopic crack evolution. Recent micromechanical investigations using micro-computed tomography (micro-CT) and discrete element modeling have further revealed that repeated FT cycling can disrupt inter-particle contacts, weaken cementation, and promote internal fracture propagation, ultimately leading to irreversible cohesion loss.