###### Abstract
These insights bridge microstructural evolution with macro-mechanical degradation. With the growing demand for cold-region infrastructure development, research on the mechanical behavior of soils under FT effects has gradually become a major focus in cold-region geotechnical engineering [14; 15; 16]. [PERSON] et al. [9] conducted rock FT experiments to elucidate the relationship between FT damage mechanisms and micro-pore quantification, finding that the presence of large pores played a dominant role in strength degradation. [PERSON] et al. [17] and [PERSON] et al. [18] systematically examined the evolution of peak strength, residual strength, resilient modulus, and dynamic shear modulus in a CGM (cement-gravel mixture) under varying FT cycles and confining pressures through triaxial testing. They further proposed distinct evolution models applicable to seasonally cold regions. Recent studies have made significant progress in understanding the FT effects on coarse-grained soils. [PERSON] et al. [19] conducted unidirectional frost heave tests and numerical analyses, revealing that coarse-grained soils containing fine particles exhibit significant frost heave under unrestricted water supply conditions. The degree of frost heave increases with higher water availability and finer particle content. [PERSON] et al. [20] performed pore structure and uniaxial compression tests, finding that as the number of FT cycles increases, the porosity of coarse-grained soils gradually increases while their strength decreases. They developed a quantitative model linking pore structure to mechanical properties. [PERSON] et al. [21] investigated the strength variations of coarse-grained soils under low temperatures and variable confining pressures, proposing a strength criterion with broad applicability. [PERSON] et al. [22] conducted resistivity and mechanical tests on coarse-grained soils from Mozhugongka, Xizang, revealing that with increasing FT cycles, resistivity gradually rises, while unconfined compressive strength, the deformation modulus, and the brittleness index significantly decline. Thesechanges stabilize after seven to nine FT cycles. [PERSON] et al. [23] used low-temperature triaxial compression tests to examine the nonlinear deformation behavior of frozen soils with varying coarse particle contents under FT cycles. They developed a binary medium constitutive model based on micromechanics, successfully predicting mechanical behavior from the microscopic to macroscopic scales. While previous studies have provided insights into the effects of FT cycles on the mechanical properties of coarse-grained soils, systematic research on the coupled effects of varying moisture conditions and FT cycles in southeastern Xizang remains limited. The underlying mechanisms of mechanical deterioration have yet to be fully elucidated. Furthermore, climate projections reported by the IPCC (2021) indicate that under global warming scenarios, alpine and marginal permafrost regions are likely to experience increased FT frequencies and greater thermal volatility, which will further aggravate soil degradation in seasonally frozen zones [24]. This context highlights the need to develop predictive, climate-adaptive geotechnical models. Although previous studies have explored the effects of freeze-thaw cycles on the mechanical behavior of coarse-grained soils, several critical gaps remain. First, most existing research has focused on laboratory conditions under simplified environmental inputs, often overlooking the combined influence of seasonal permafrost, high-altitude climatic gradients, and monsoonal moisture fluctuations that are characteristic of the southeastern Qinghai-Xizang Plateau. Second, while the mechanical degradation trends of soils have been studied, limited attention has been given to region-specific parameterization and its integration into numerical slope models for assessing long-term stability.