Toppling deformation mechanisms in layered rock slopes controlled by bedding dip angle

Rock slope toppling is a widespread geological hazard, and a clear understanding of its deformation and failure characteristics is essential for slope engineering and hazard mitigation. Investigating the mechanisms governing toppling failure provides a scientific basis for optimizing slope design and reducing associated geological risks. In this study, the deformation evolution and failure mechanisms of layered rock slopes with different bedding dip angles were investigated through a combination of base-friction physical model tests and numerical simulations. The results show that bedding dip angle plays a critical role in controlling the deformation pattern and instability behavior of layered rock slopes, leading to distinct failure processes under different structural conditions. For slopes with bedding dip angles of 45° and 60°, cracking initiated near the slope toe and subsequently propagated upward. In contrast, when the bedding dip angle increased to 75°, cracks first developed at the slope crest and gradually extended downward toward the slope toe. With increasing bedding dip angle, the rear boundary of the toppling zone progressively migrated backward, accompanied by greater rock mass damage depth, expansion of the toppling zone, and more pronounced toppling deformation. Furthermore, image-based tracking and identification techniques were employed to monitor displacement variations during the toppling process. The monitoring results indicate that slope deformation exhibits clear stage-dependent characteristics, evolving progressively from localized deformation to global instability. The observed differences in toppling behavior among slopes with varying bedding dip angles are mainly attributed to bedding-orientation-induced variations in the underlying failure mechanisms. These findings provide valuable insights into the toppling deformation mechanisms of layered rock slopes and offer a scientific basis for stability assessment and hazard evaluation of slopes prone to toppling failure.