Abstract: The damage of rock caused by freezing and thawing is closely related to its bedding structure, and the freeze-thaw damage is a comprehensive performance. A simple consideration of the change of a single defect inside rock mass or a single external factor under freezing and thawing cycles is insufficient to objectively reflect the damage. In this paper, freeze-thaw tests subjected to 0, 20, 40 freeze-thaw cycles were carried out on the vertical and parallel layered samples. The damage development characteristics of the layered sandstone during the freezing and thawing process were explored. Based on the ?100 mm SHPB test device, impact tests at five types of speed were carried out, and the distribution law of impact crushed degrees of layered sandstone under the condition of freeze-thaw cycles was analysed. Based on the correlation between the accumulation of freeze-thaw damage and the degree of crushing, a freeze-thaw degradation model of layered sandstone was established by the deterioration of mechanical properties. It is found that under the action of freezing and thawing, the longitudinal wave velocity, pore development and impact crushing morphology of these two types of layered sandstone samples are significantly different. There are three correlations between the degree of fragmentation and the number of freeze-thaw cycles, i.e. positive correlation, negative correlation and fluctuation. The calculated values of the intensity and peak strain obtained from the negative correlation region data, as well as the proportional and overlapping area data, are very close to the measured values. The calculated values of the intensity based on the positive correlation data are also in good agreement with the measured values.

Key words: rock mechanics, freeze-thaw cycle, layered sandstone, damage coefficient, deterioration model