Post-mining pit lakes and slope stability — The Águas Claras Mine example

After being in operation since 1973, the Águas Claras Mine is approaching completion, scheduled for the year 2002. The pit will be later filled with water to create a lake, the Águas Claras Lake. Analyses of the progressive submergence of the slopes and their relative stability were performed, initially using Limit Equilibrium methods. Supplementary numerical analysis was also performed, using two-dimensional finite difference and distinct element codes. The aim was to address specific problems not handled by Limit Equilibrium methods, such as assessment of stress-strain behaviour of the slopes upon excavation and lake filling, and analysis of a toppling-prone sequence at the South wall. The results of the analyses showed that the implementation of the lake is feasible, provided that special attention is devoted to the initial stages of filling.