Stability analysis of overburden rocks—a new approach

Overburden dumping is an important issue in consideration of economy and safety for surface mining of coal. The higher slope angle and increased dump height improve the economic benefits, however decrease the stability of the dumps. Dumping methods are classified as (i) end-tipping method and (ii) paddock-dumping method. However, the stability analysis models practised for both the cases are same. The dump slope stability models consider internal friction angle, cohesion and some other properties as the essential parameters affecting the stabilising and destabilising forces. These parameters are significantly changes with the types and sizes of the rock materials. While the dumping methods are different, these properties are changing at different depths of dump. This consideration is missing in the current dump slope stability modelling. This paper focusses on the comparative analysis of stability achieved by forming an overburden dump by an end-dumping approach as well as the paddock approach. From a dump stability analysis, it is found that end dumping exhibits a better factor of safety up to a dump height of 90 m (3 benches of 30 m each) and paddock dumping exhibits better factor of safety than the end-dumping method beyond that and up to a dumb height of 150 m. The paddock-dumping method poses a better factor of safety as compared to the end-dumping method as the number of benches goes up. The reason for higher safety factor in paddock dumping as compared to end dumping may be attribute to the better size distribution and compaction due to machine movements.