关键词: 红砂岩, 冻融循环, 颗粒破碎, 破碎强度

Abstract: 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.

Key words: red sandstone, freeze-thaw cycle, particle crushing, crushing strength