The lignite deposits from Oltenia’s mining area consist of several lignite layers, separated by sterile formations. The thickness of the coal layers, as well the sterile intercalations varies in a wide enough range, not only among the entire coalfield, but even in the same exploitation field. Taking into account the geological specificities of the deposit and the large number of open pits in which is extracted, the analysis of the opportunity to introduce highly selective extraction of thin layers in each open pit is difficult because of the large amount of calculations to be performed. For this reason, in this paper an open pit model is discussed, in which the selective extraction of a thin lignite layer is analyzed, in terms of different layer thicknesses and three different lengths of the exploitation front. In order to determine the influence of layer thickness and front length on the main economic indicators of the exploitation activity, not only quantitatively but also qualitatively, on the proposed open pit model the sensitivity analysis realized, which takes into consideration three different extraction technologies: nonselective extraction, limited selective extraction and highly selective extraction. In order to establish the optimal technological variant for extracting of the thin lignite layers in various concrete conditions (length of the exploitation front, layer thicknesses) a flexible multi-criteria multi-attribute type optimization method has been used, namely the weighted average maximization method. In order to generalize the conducted study for other concrete exploitation conditions (front length and coal layer thickness), a nomograph has been drawn-out based on the extrapolation of the calculated values and on the regression equations of the curves representing the separation limit between optimal zones.
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- Research on the Optimal Technology for Exploitation of the Thin Lignite Layers in the Open Pits from Oltenia Coalfield