Influence of freeze–thaw cycling on the dynamic compressive failure of rocks subjected to hydrostatic pressure

Freeze–thaw process has a significant deterioration effect on the rock mechanical performance. Responding to the accelerating changing climate, the investigation of the freeze–thaw cycling (FTC) effect on the dynamic failure of rocks subjected to static hydrostatic stress is crucial for a better design of underground rock structures in cold regions. Thus, the specimens made of a porous and homogeneous green sandstone (GS) were treated at various FTC numbers (0, 10, 20, 40, and 50 times) in this study. The FTC-induced damage was first examined using the scanning electron microscope (SEM) method. Subsequently, dynamic compressive tests were conducted under different hydrostatic pressures (0, 2, and 4 MPa). The results indicate that the dynamic compressive strength of specimens decreases with the FTC number at a given loading rate and hydrostatic pressure. And the hydrostatic pressure enhances the dynamic compressive strength, while the rate dependence is stronger under higher pressure. Furthermore, the larger the FTC number, the greater the enhancement effect of hydrostatic pressure on the strength. Another important observation is that the density of the radial cracks and the total crack volumes in the FTC processed specimens after dynamic tests both increase with the FTC number. Moreover, the increasing confining pressure constrains the growth of crack density. These results are helpful for the safety enhancement and hazard assessment of deep rock engineering applications in cold regions.