Failure mechanism and stabilization of a basalt rock slide with weak layers

Multiple slides of rock slopes with dip weak layers have occasionally occurred in Chinese roadway engineering, representing a very complex problem associated with roadway excavation. Unfortunately, the failure mechanisms of such slopes are not clearly investigated prior to excavation, thus leading to expensive remedial work installed after the significant deformative phenomena occurred. Furthermore, pre-reinforced piles have not received enough attention to be used to stabilize the slopes during the excavation process, which enables the slope movements. This paper, therefore, aims to explore the failure mechanisms of a basalt rock slide with dip weak layers and analyse the impacts of pre-reinforced piles on the slope stability. Field investigations, laboratory tests, and in situ deformation monitoring are conducted. Slope stability before and after excavation is analyzed using the finite element and limit equilibrium analysis methods, respectively. The outcomes of the analyses reveal that excavation and the presence of dip weak layers are the main contributory factors to the rock slide. The failure surface of the slope varies with increases in excavation rather than always occurring along the revealed weak layers. The instability appears to be multiple translational slides. Additionally, a finite element analysis for the slope pre-reinforced with row piles during different stages of excavation is conducted. Based on the study results, the pre-reinforced pile is crucial for the slope stability, and the impact of pile position should be prudently considered in design.