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Recent changes in the fossil-fuel energy sector require coal mining industries to plan for the future, including developing procedures for decommissioning and closure associated with mines. In surface coal mining, the geotechnical issues of decommissioning include the long-term stability of the pit slopes, particularly as the pit is gradually filled with water. This paper investigates such slope stability issues, with emphasis on the conditions prevailing in the Amyntaion surface lignite mine, in Western Macedonia, Greece. Analytical and numerical methods have been developed and used to estimate the temporal evolution of the overall safety factor, as the water level in the pit rises, creating a lake. It is shown that until the water level in the lake reaches a critical depth of approximately 15–35% of the final equilibrium condition, the safety factor against the overall slope instability decreases slightly (by about 3% in the case study, and up to 5–10% in other conditions) compared to its value at the end of exploitation. At higher lake levels, the safety factor increases significantly, as the beneficial effect of the lake water pressure acting on the slope overcomes the adverse effect of pore water pressure rise inside the slope. In typical mines, the critical water depth is achieved within a few years, since the surface area of the pit is smaller at deeper levels; thus, more favorable slope stability conditions are usually reinstated a few years after mine closure, while the small reduction in safety during the initial stages after closure is inconsequential. The paper investigates the parameters influencing the magnitude of the small reduction in the short-term safety factor and produces normalized graphs of the evolution of the safety factor as the lake water level rises. The results of the analyses can be used in preliminary closure studies of surface coal mines.

The lignite surface mines often occupy large areas to develop the mining activities: pits, dumping areas, bunkers, buildings, workshops, and other auxiliary facilities. The land reclamation methods and the corresponding land use alternatives after the mine closure constitute an important part of an integrated mining planning. In the present contribution, the main parameters of geospatial planning are investigated in order to assess the changes in land uses in a mining area and to correlate them with the spatiotemporal development of the extraction works. As a case study, geospatial analysis of the current situation in Ptolemais mines is presented. In particular, seven dumping areas are assessed regarding their suitability for specific land uses. The assessment is based on the following criteria: a) slope gradient, b) reclamation works already completed, c) slope aspect, d) proximity to the road network, and e) proximity to residential areas. Furthermore, the ArcGis software is used to compile the layer maps of the corresponding parameters.

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