Geotechnical Issues in Decommissioning Surface Lignite Mines—The Case of Amyntaion Mine in Greece

Abstract

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.

A Scenario-Based Analysis for the Selection of Post-Mining Land Uses Applying a Cellular Automata Model

“…This study examines the Ptolemais mining area, located in the Kozani Province of Western Macedonia, where lignite extraction has been carried out for over six decades [10]. Over the years, the Public Power Corporation (PPC) of Greece has utilized both continuous and non-continuous mining methods to operate multiple mines located within the extensive lignite fields of Western Macedonia [11]. Figure 1 depicts three distinct maps representing the existing land uses, predetermined land uses, and the land uses employed within the model.…”

Reassessment of the Stability Conditions in the Lignite Open Pits of Oltenia (Romania) in Relation to the New Local Seismic Context as an Imperative for Sustainable Mining

“…For the sustainable development of lignite mining, whenever unexpected sliding phenomena occur their causes must be identified, and appropriate measures must be taken in order to eliminate their effects [1,2,[11][12][13][14][15][16]. Monitoring stability conditions and the development of early warning systems are the main ways to prevent slope failure that may result in material and/or human loses [1,[17][18][19][20][21][22][23][24].…”

Investigation Into the Impact of Mining and Geological Structure on the Geomechanical Parameters of Open Pit Walls During Mining Operations at the Synclinal Two-Seam Coal Deposits

“…При этом в мировом случае имеется много случаев уничтожения горнотранспортного оборудования и гибели производственного персонала, как это было на месторождении медно-порфировых руд в штате Юта на территории СШа («Бингем-карьер»). В горном деле исследованиям устойчивости горных выработок при ведении как открытых, так и подземных горных работ уделяется большое внимание, о чем свидетельствуют результаты работ по геомеханике, представленные в краткой подборке тематических научных трудов [1,2,3,4,5,6,7,8,9,10]. Предложенный подход определению геометрии тех нологических параметров элементов бортов карьеров в зависимости от угла наклона угольных пластов в углевме щающей толще позволит формировать предложения по оптимизации конструкции борта карьера, удовлетворяю щей как требованиям экономической эффективности до бычи угля, так и требованиям безопасного производства открытых горных работ.…”