Bench Stability Design Based on SMR, Q-Slope, Block Theory and Kinematic Analysis

Abstract

The slope angle is one of the key parameters conditioning the stability of rock cuts such as roads, rails and surface mines. In open pit mine projects, the choice of the maximum safe slope angle (MSSA) is an essential step for the calculation of ore-to-waste ratios, for preliminary layout and excavation of stable and safe pit slopes. This step requires a lot of geotechnical information on the rock mass properties mainly on discontinuities and intact rocks. Since the geotechnical data are generally so limited at this stage, it is difficult to use conventional methods such as limit equilibrium analysis or numerical methods. In this paper, the slope mass rating (SMR), Q-Slope method and kinematic analysis, were employed to evaluate the maximum safe slope angle of four benches at different zones of an open pit mine in Morocco. At first, the available data on the intact rock and discontinuities of each rock mass were determined and used to assess the quality of the rock mass of each studied bench. Then, these data were employed as inputs of SMR, Q-Slope and kinematic analysis to obtain the MSSA of each bench. The results show that SMR, KBT and kinematic analysis provide stable slope angles that seem very closer to the real slope face angles reported by the mine than those obtained by Q-slope method. This study demonstrates clearly that block theory and kinematic analysis provide helpful tools and an advance procedure to estimate the suitable rock slope angles for either mining or civil engineering projects.