ABSTRACT
In an effort to optimize remaining coal reserves below dumping material. The general action that could be taken is the re handling of dumping materials in whole or in part. In X Pit Case, re-handling would be taken in part to reduce the volume of dumping material which needed to be removed. Partial removing will be conducted by undercut of dumping material where there is going to have the consequences of reducing the resisting force in slope stability. For minimizing the risk due to reduced restrain force, therefore a mining sequence will do by cut and fill method. This method is going to divide workspace become some smaller block workspace. Each smaller workspace would be conducted cut by excavating until mine out and then back filled before excavating next block to manage reduction of resisting force. Using slide3, we could do a two-dimensional (2D) and three-dimensional (3D) stability analysis with limit equilibrium method in the same model. The 2D force calculation is performed per slice on base and 2 side strength of slice. At the same time, 3D force calculation is performed per column on base and 4 side strength of column. The analysis result show when each block have cut until mined out have Factor of safety (FoS) value on 2D calculation less than 1.2. It also have FoS value less than 1.2 on 3D when re-handle sequence without cut and fill. Whereas 3D analysis result which considering 4 side strength of column calculation and limitation of reduction resisting force by cut and fill mining sequence show FoS value greater than 1.2 where have fitted based on the company standard which refer to government regulation and Stacey criterion.
