Interaction of water saturation and freeze-thaw cycles on stress wave attenuation and dispersion in sandstone

Investigating the interaction of water saturation and freeze-thaw (F-T) cycles on stress wave propagation in sandstone is significant for dynamic stability analysis of rock engineering in cold regions. This paper investigates the attenuation and dispersion of stress waves in sandstone with varying saturations during F-T cycles. Sandstone specimens with different initial saturations (0%, 30%, 70%, 80%, 90% and 100%) were subjected to different F-T cycles (0, 5, 10, 15 and 20). Impact tests employing high-speed photography and digital image correlation (HS-DIC) were conducted to study the loss ratio of wave velocity and the attenuation ratio of peak velocity in sandstone with varying saturations during F-T cycles. The effects of the saturation and F-T cycles on the attenuation coefficient of velocity pulse were discussed. The dispersion of velocity pulse with saturation and F-T cycles was revealed through time-frequency spectrograms. The results show that the loss ratio of wave velocity approximately linearly increases as saturation increases. The attenuation ratio of peak velocity and attenuation coefficient exhibit three stages as saturation increases, including rapid increase stage (0% to 30%), slow increase stage (30% to 70%) and rapid increase stage (70% to 100%). The dispersion of velocity pulse in water-saturated sandstone significantly exceeds that in dry sandstone and progressively intensifies with increasing saturation. With increasing F-T cycles, the loss ratio of wave velocity, attenuation ratio of peak velocity and attenuation coefficient increase. More F-T cycles lead to more observable dispersion of velocity pulse.