3D large-scale numerical model of open-pit lake slope stability—case study of Lake Most

Abstract

Almost all post-exploitation open pit mines in the world are shaped as a final water reservoir. One of the main hazards is the slope stability of lake banks. To develop a reliability methodology for assessing the long-term stability of flooded open-pit lake, a back analysis was conducted using 2D and 3D large-scale numerical models of Lake Most, which is one of the largest mining lakes in Europe (Czech Republic). The large-scale numerical model was built, based on the site observations, large scale LiDAR data, in situ characterisation tests, and statistical analysis of geotechnical data, on DTMs defining the complex geology of the site and on numerous piezometric levels to build the water table. Local and global safety factor (SF) were calculated using the strength reduction method. The results highlighted the reliability of the methodology to combine the geometric model with the geological model to create a large-scale numerical model, to identify local and potentially instable zones, and to highlight the role of a weak contact layer. The calculation of 3D SF has shown a very good correlation between the lowest SF and the ground movement observations noted by the Czech authorities.