Seismic Response and Dynamic Failure Mode of a Class of Bedding Rock Slope Subjected to Freeze-Thaw Cycles

Natural freeze-thaw (FT) cycles and earthquakes are two key triggers for landslides in cold regions. However, investigations on their coupled effect are rare. In the current work, this coupled effect was investigated by shaking table tests of two slopes, namely a non-freeze-thaw (NFT) slope and a FT slope. Results indicate that the slope's natural frequencies decrease, whereas the damping ratios increase, indicating that dynamic cumulative damage occurs, thereby relationships between damage coefficients and earthquake intensities have been established. The acceleration amplification coefficients of both slopes initially increase and then decrease as the seismic amplitude increases, with the critical amplitude for the NFT slope being 0.4 g and the FT slope being 0.3 g. After FT cycles, the development of tiny cracks within the FT slope enhances the reflection and refraction of earthquake waves, and the decrease in the slope's natural frequency brings it closer to the dominant frequency of the seismic waves, resulting in the amplification coefficients of the FT slope being greater than the NFT slope. Slope surface displacement evolves through elastic deformation, plastic deformation, and failure phases. Regarding the dynamic failure modes, the crack at the slope top and the bedding planes form a locked segment to maintain initial slope stability. Accumulated stress leads to sudden shear failure. With the elapse of earthquake excitation, the NFT slope shows a cracking-shearing-sliding failure mode. As for the FT slope, the shallow rocks above the FT interface experience strength degradation, leading to small-scale sliding and collapses, followed by instability and sliding of the slope behind that portion of the rock mass.