Investigation of groundwater level change and its impact on slope stability in the Sector-E of Afsin-Elbistan Open-Pit Lignite Mine in Turkey

The objective of this study was to examine the stability of the bench and overall slope angles that would result from the open pit mining of 1.5 billion tonnes of lignite in Sector-E of the Afşin-Elbistan lignite basin. Eleven geological sections have been developed so far for the stability investigation of the final slopes in the eastern and southern portions of Sector-E. The Slide2 program was employed in these experiments to conduct slope stability analyses. The Spencer method, which is a type of limit equilibrium method, was employed in these analyses. Different analyses were conducted in the studies on bench slope angle and overall slope angle in accordance with the circular and non-circular slip models that occurred and/or were anticipated to occur in the region. The range of overall slope angles with acceptable coefficients of safety (SF ≥ 1.5) and reliability index (RI ≈ 3) for east slopes was 8.94˚ to 13.30˚, and for south slopes was 6.33˚ to 13.49˚, as determined by the slope stability analyses conducted at various groundwater levels. In addition, the relationships between the groundwater level and the overall slope angles were presented for each section.