Comparative Analysis of the Hard Hillsides Stability by Empirical Methods and Limit Equilibrium: Case of Ultra Basic and Andesites of Mako and Marbles of Bandafassi (Senegal)

The purpose of this paper is to characterize rock mass stability using basic rock mass method and to compare them. Rock mass quality and strength are determined using rock mass classification and numerical methods. The Factors of safety are calculated with the results of stereographic projection. Results show that quality of ultrabasite and marble are better than quality of andesite. The Slope Mass Ratings (SMR) show that rocks with the best quality are stable and andesite partially stable. The calculation of the factors of Safety by limit equilibrium assigns a stable state for ultrabasite and marble and instable for andesite. Calculation of Safety factor using stereographic parameters in one hand and finite element code in another shows more possibility of planar sliding along discontinuities than rock matrix failure. At last, quality of endogeneous rock mass is correlated with its stability state. The better rock mass is, the more stable the rock it is.