Study on the tensile properties of sandstone with different water contents under freeze-thaw cycles

Mines in cold regions of China are affected by freeze-thaw cycles, resulting in uneven expansion and contraction of rocks, leading to the formation of cracks. At the same time, the expansion of cracks due to water frost heave between cracks leads to rock damage. In turn, it affects the stability of slopes. To study the tensile properties of sandstone with different water contents under freeze-thaw cycles, Brazilian splitting tests are conducted on sandstone with different water contents (0, 35%, 70%, 100%) under different freeze-thaw cycles (0, 10, 20, 30 times). Acoustic emission monitoring is also conducted to analyze the effects of water content and freeze-thaw cycles on the tensile properties of sandstone. The results show the following points. ① When the water content of sandstone is less than 35%, the decrease in tensile strength of sandstone is relatively slow. When the water content is greater than 35%, the decrease in tensile strength becomes faster. ② The peak frequency distribution of sandstone acoustic emission signals has obvious frequency band features. The increase in water content will delay the appearance of the main concentration area of sandstone acoustic emission signal peak frequency. ③ As the number of freeze-thaw cycles increases, the acoustic emission ringing count and cumulative energy peak of non-fully saturated sandstone continue to decrease. The acoustic emission signal of fully saturated sandstone decreases, and the peak acoustic emission ringing count shows a trend of first increasing and then decreasing. The low peak frequency of the acoustic emission signal of sandstone with the same water content decreases from 50 kHz to below 10 kHz. The acoustic emission signals during the loading process of sandstone when freeze-thaw cycle is 10 are mainly low-frequency signals with a peak frequency of less than 20 kHz. After 20 freeze-thaw cycles, the peak frequency of the acoustic emission signals of sandstone decreases to below 10 kHz. ④ The entire loading process of sandstone is mainly characterized by low-frequency and low-amplitude acoustic emission signals, mainly resulting in small-scale cracks.