In cold region engineering construction

freeze-thaw (F-T) degradation and particle crushing of a coarse-grained soil fill are critical factors affecting the long-term stability of engineering projects. To reveal the underlying F-T degradation mechanism

this study conducts single-particle flat platen compression tests for spherical red sandstone particles under 0 to 40 F-T cycles. We examine the influence of F-T action on the macro- and meso-mechanical properties of the particles

by combining the Weibull statistical theory

Hertz contact theory

and a scanning electron microscope (SEM) microstructural analysis. The results indicate the F-T action produces a significant dual degradation effect. First

it leads to a noticeable reduction in the peak load

elastic modulus

and fracture energy of the particles; The peak load degrades nonlinearly in three-stages－initial rapid decline

an intermediate stable stage

and severe deterioration. Secondly

it exacerbates the heterogeneous degradation of internal structure

resulting in an increased dispersion of strength distribution and the attenuation of the Weibull modulus. The SEM analysis reveals that the repeated frost heaving of pore water induces interconnection of micro-pores

propagation of micro-cracks

and damage to cementing materials

which consequently triggers the deterioration of macroscopic mechanical properties of the granular materials. We develop a theoretical analytical model for the characteristic strength of particles subjected to F-T action

based on the linear elastic fracture mechanics and the Hertz contact theory

and validate it using experimental data. Our findings reveal the F-T degradation mechanism

which is useful for evaluating the long-term performance of dam-building materials in cold regions.