Composite collapse mechanism of an anti-dip rock slope

Collapse is a common instability mode of anti-dip rock slopes. This type of failure involves a complex geo-mechanical process. This work investigated the collapse mechanism of an anti-dip rock slope in a granite mine in Shanxi Province, China. A detailed field survey was carried out to analyze the inducing factors and failure process of collapse. Then, discrete element numerical simulations were conducted by the Universal Distinct Element Code (UDEC) to determine the microscopic damage and macroscopic failure of collapse. Through these works, the composite collapse failure mechanism of the anti-dip rock slope was investigated comprehensively. Results show that the structural planes perpendicular to the slope surface and the steep anti-dip structural planes are the prerequisites of collapse. Strength softening of the structural planes caused by rainfall is the triggering factor of collapse. The collapse of such a rock slope can be considered as a composite failure composed of shear sliding, block toppling, and flexural toppling. In addition, the numerical results indicate that the composite failure of shear sliding and block toppling occurs at the toe of and the middle of the slope, followed by flexural toppling failure at the rear edge of the slope. Therefore, the monitoring and treatment of such type of collapses should be concentrated on the composite failure zone where shear sliding and block toppling occur. The high consistency between the numerical results and field observations shows the feasibility and rationality of using UDEC to study such collapse from the microscopic damage to macroscopic failure. The results enrich the type of collapse of anti-dip rock slopes and provide a scientific reference to the design treatment for such slopes.