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Closure planning is a fundamental requirement for all existing and planned future mines. However, there are no accepted industry guidelines for how to assess options for open pit closure or for advancement of the closure plan in parallel stages with overall project development and operation. Ideally, closure planning needs to consider the site sett...
Context in source publication
Context 1
... Reducing the time required for stabilization of the pit lake and surrounding groundwater system • Improving the post-closure water quality of the pit lake • Allowing pore pressures to rapidly equalize in order to improve the stability of the pit walls A pit lake developed immediately upon shut down of the pit floor sump and in-pit dewatering wells ( Figure 5). The rise of the lake level has occurred in accordance with the pit lake model predictions developed in 2018, and the lake level is now about 40 m depth below the pit rim. ...
Citations
... Mine closure activities include a set of procedures from concept planning to a detailed closure plan, post-closure monitoring activities, and post-closure land re-use [2,3]. These critical parameter because it controls the stability of the lake when the inflows are equal to or less than the outflows [18]. ...
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, inWestern 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.
