Geotechnical Characterisation and Stability Assessment of Two Pitwall Slopes at a Large Aggregate Quarry, Durban, South Africa

Abstract

Two unique pitwall slopes have been identified as major zones of potential slope instability at Coedmore Quarry. The first pitwall is a highly jointed rock slope known as a bullnose, whilst the second is a rehabilitated slope comprising cohesionless waste rock material resting at the angle of repose on the mined out pit slope benches. Consideration was given to all the internal and external aspects governing the stability of each slope, including geotechnical properties of the materials, ground induced acceleration due to blasting and the presence of groundwater from rainfall infiltration. Analyses of the bullnose comprised kinematic analysis and limiting equilibrium analysis, whilst analyses of the rehabilitated soil slope comprised an infinite slope stability analysis and pseudostatic analysis. Overall, it was concluded that both slopes are stable during aseismic and dry conditions, although the influence of groundwater and the occasional peak ground accelerations may result in slope instability.