Mode II Fracture Properties and Microscopic Damage Characteristics of Granite Under Freeze-Thaw Cycles: Laboratory Testing

Rock masses in alpine regions inevitably undergo freeze-thaw (F-T) cycles, which affects the safety of infrastructure such as slopes, with shear failure being a significant concern. This study investigates the Mode II fracture behavior of F-T treated granite via the short core in compression (SCC) test, analyzing the related physical properties and mechanical properties while also discussing F-T damage mechanism at a microscopic level. Results reveal that as F-T cycles increase, the dynamic elastic modulus and P-wave velocity decrease, whereas porosity and backbone fractal dimension of pore scale increase, indicating a transition towards a large-scale pore. Mode II fracture toughness decreased by 31.19% and fracture process zone width increased by 248.49% with F-T cycles rising from 0 to 80, and related fractal dimension of surface morphology also increased by 11.17%. Microscopic observation reveals the microstructure deterioration induced by F-T treatment, indicating the correlation between microscopic damage and macroscopic fracture properties.