Deformation of open pit mine slopes by deep seated toppling

ABSTRACT

The relationships between engineering geology, structural geology, strength properties and failure mechanisms of several large slope failures in western North America are examined. The main failure mechanism identified at each site involves primarily deep seated toppling. Characteristics, diagnostic features and behaviour of each failure are reviewed. Back analyses of two failures using limit equilibrium techniques as well as numerical modelling confirms that the toppling mechanism is extremely sensitive to mining activity and groundwater pressure. Although deep seated toppling failures may involve more than several million tonnes, large deformations of the order of several tens of metres have been documented without catastrophic failure. These deformations are explained from the results of numerical modelling using a distinct element finite difference code. Ongoing research and documentation of such failures is providing a clearer understanding of the deformation behaviour of high rock slopes.