Abstract: The study of the degradation mechanism of freeze-thaw damaged rock holds significant theoretical importance in understanding freeze-thaw disasters, predicting disasters, and designing tunnel protection systems in cold regions. Based on the volume expansion theory, this research establishes a correlation between irreversible volume increase and the number of freeze-thaw cycles, and also deduces the law of radial heat transfer for cylindrical samples during freeze-thaw cycles. Considering the freeze-thaw damage process of saturated samples, a model of rock freeze-thaw damage based on discrete elements is developed. The physical and mechanical properties of sandstone with different freeze-thaw cycles are tested to validate the model, using stress-strain curves and uniaxial compressive strength. Building upon this, the growth and distribution of cracks in rock samples during freeze-thaw cycles are analyzed, and the crack growth process under coupled freeze-thaw-stress conditions is studied. The research findings indicate that as the number of freeze-thaw cycles increases, the development of cracks undergoes three stages: slow, fast, and then steady. The number of cracks increases radially from the inside to the outside of the sample. Approximately 80% of the frost heave cracks are distributed in the circular column area 10–25 mm away from the sample’s axis. When the number of freeze-thaw cycles is less than 80, the increase in the number of cracks follows an exponential function relationship. However, when the number of freeze-thaw cycles exceeds 80, the number of cracks increase logarithmically with their distance from the center of the circle. During the freeze-thaw cycle, the damage in the sample primarily occurs through tensile failure, and the freeze-thaw damage process of the rock is influenced by the initial pore structure.

Key words: freeze-thaw damage, discrete element method, volume expansion, heat conduction, cracks