UDEC-based stability analysis of jointed bedding slope and slope parameter optimization suggestions: a case study

Abstract

The major hazard in open pit mining is ground movement resulting from the instability of the mining slopes. Among the factors that influence slope instability, external loads from earthquake and rainfall are of serious concern. In this paper, the conventional and numerical methods of slope stability study have been used to investigate the stability of the designed mining slopes and subsequent optimization of the slope parameters at Tanjiashan mine in P.R. China. The mine is on a rugged terrain with complex geology having bedded rock strata with highly developed joints. The simulation to understand the stability of the overall slope (before and after mining) was explored using UDEC software by considering four working conditions: natural, natural + earthquake, heavy rainfall, and heavy rainfall + earthquake. Rocscience DIPS software was used for the kinematic feasibility study to determine the failure mechanisms in the slope forming rock masses. SLIDE and SWEDGE software were used to determine the factor of safety for expected sliding and wedge sliding blocks and subsequent optimization of step slope angles in the different slope forming rock masses. It was established that the overall natural slope is stable. However, the overall mining slope is not stable due to the steepness of the step slopes which allow for the bedding planes (planes of weakness) to daylight on the slope faces. The compression shear bi-planar sliding is the potential failure mechanism. The optimization of the step slopes angles by rock formation resolved the instability problem on the overall mining slope.