Effect of Berms on the Seismic Stability of Benched Excavations in Rocks

Berm is an integral part of any benched excavations. Berms of adequate width usually serve multiple purposes, including rockfall retention, debris collection from bench excavations, mining equipment operations, and transportation utilities. Therefore, determining the optimum dimensions of berms is one of the design criteria in slope engineering. This study investigates the effect of berms on the stability of such benched excavations in rocks under seismic conditions. The finite difference method-based software FLAC/Slope is used to perform the stability analysis. In FLAC/Slope, the modified Hoek-Brown criterion, a more relevant rock strength criterion, can be directly employed to model the rock mass strength. Besides, FLAC/Slope does not require prior assumptions of the failure surfaces and can incorporate the pseudo-static inertia forces in the analysis. Accordingly, benched slopes with varying berm widths and numbers are analyzed for different excavation gradients, rock mass properties, and seismic scenarios. Increasing the number of berms with a reduced bench height is meant to improve slope stability, which can be further optimized by providing an appropriate berm width.