STABILITY STUDIES OF THE EASTERN SLOPES OF AFŞİN-ELBİSTAN, KIŞLAKÖY OPEN-PIT LIGNITE MINE (KAHRAMANMARAŞ, SE TURKEY), USING THE ‘FINITE ELEMENTS’ AND ‘LIMIT EQUILIBRIUM’ METHODS

In open pit mining from the safety point of view it is very important that physical and mechanical characteristics of the dug-out materials are carefully studied, and geological and geotechnical characteristics should also be considered in planning bench slopes of the dug-out materials. The purpose of this study is to work out the stable slope geometry of the eastern permanent slopes in the Kışlaköy open pit lignite mine of the Afşin-Elbistan Linyit İşletmesi. In the Kışlaköy open pit mine, 35 geotechnical drillings totalling 3393.20 m were made for the geotechnical studies and to work out slope sizing. A total of250 vertical electrical drillings (DES) were also made to study tectonic features and lithological changes which do not have surface expressions. All these data have been used in this study. Design analyses showed that black coloured clay bands with high plasticity present in between lignite horizon is the most important unit controlling slope stability. Slope stability analyses have in general been conducted using the ‘finite elements’ and the ‘limit equilibrium’ method to suit block sliding model and to suit different groundwater conditions. In the analyses for the stresses affecting the slices; central part of the slice has been taken as a base and the ‘finite elements’ stability studies have been conducted then the findings have been compared. According to this it is understood that if stresses affecting the slices are conducted by the ‘finite elements’ method then calculated factor of safety on the bench base would be more from 1% to 7%, and in the slope angles it would be more from 1% to 23%.