Stability of open pit lignite excavations during flooding: comparison of a simplified analytical tool with limit equilibrium computational analysis

Abstract

A common practice for valorizing abandoned open-pit mines is flooding them to form pit lakes. Slope stability in post-coal areas is critical due to failure incidents reported in surface coal mines during operation and valorization. An analytical model was recently presented concerning evaluating the pit lake’s slope stability in the presence of a weak zone. The present work compares that analytical model with a limit equilibrium computational approach for lignite mines’ stability. Assumptions of each model are discussed, and identical geometries and geotechnical parameters are implemented. It is concluded that the Safety Factor and its evolution are very sensitive to the water regime and the lake’s depth for the analytical model. On the other hand, the limit equilibrium analysis considering the same piezometric and lake levels proposes a drastically different SF evolution. Overall, the differences between the analytical and the limit equilibrium analysis might refer to different water conditions in practice and should be implemented with due caution.