Isikdere open pit mine has been operating since late 2009 by the Turkish Coal Enterprises to provide lignite for a thermal power plant. The technical objectives of this study are to evaluate stability of the final pit slopes and to recommend necessary modifications on the current pit project and remedial measures. The analysis results indicate that stability of the final pit slopes is sensitive to multiplanar failures and pressurized water in the coal seam is also another factor adversely affecting the stability. Problems associated with groundwater at the site were also assessed with the analyses of piezometric level and groundwater inflow. Remedial measures investigated suggest that at some parts of the pit, original project should be modified by flattening or shifting the final slopes towards north or stripping them to a certain elevation.
The Isikdere open pit mine, with a length of 2.5 km, width of 750m and maximum depth of about 150–170m located at western Turkey, has been operating since late 2009 by the Turkish Coal Enterprises (TKI) to extract lignite for a thermal power plant in the vicinity (Figure 1a). Excavation of the pit has been initiated at the SE boundary of the coal sector and is progressing towards NW (Figure 1b). The current width and face angle of the working benches are 7–10mand 60°, respectively, and overall angle of the final sidewall slopes is planned as 30°–32°.
The technical objectives of this study is to evaluate stability of the final pit slopes throughout the coal field, to assess hydrogeological conditions affecting the pit slope stability, and to recommend necessary modifications on the initial pit project and remedial measures based on geotechnical and hydrogeological conditions.
At the Isikdere coal field, Tertiary coal measures, which consist of Turgut, Sekköy and Yatagan formations, overlie the basement rocks (Palaeozoic schist and Mesozoic crystallized limestone at south and north, respectively). The Sekköy formation consists of thick-bedded compact marls overlying the coal seam, thinly laminated marls and limestone alternation and a weak zone at the top at north. The coal seam is underlined by the plastic underclay of Turgut formation (Fig. 2).Yatagan formation is the youngest section of the coal measures mainly consisting of tuffites and marls and exposes at the SE boundary of the pit. An alluvial sequence of 2–8.5m thick and slope debris composed of fine grained material surrounding small pieces of limestone overlie the coal measures at the west and north, respectively.