ABSTRACT
A very complex slope failure took place at an open-pit coal mine in 1984 in the eastern Turkey. The earlier investigations showed that a basal clay layer at the bottom of the coal seam was the main cause of the failure. The failure took place while the coal seam was uncovered. In this study, a series of back analyses utilizing the information of geotechnical investigations before and after the failure and static and dynamic limiting equilibrium techniques and finite element analyses were performed, and their outcomes are presented and discussed. It is shown that the failure process was complex and involved the buckling of the lignite seam, sliding along the basal clay layer and shearing failure of overburden layers. The drainage conditions also played an important role in the initiation of the failure. Once the failure as initiated, the failure developed rapidly.
