In India, accelerated demand of coal resulted in rapid development of open pit mines. This has resulted into adoption of stripping ratios ranging between 1:15 to 1:25 and mine depths of open pit mines greater than 300 m, from topographic surface, being reached. All this reguires removal of huge guantities of overburden material needing to be accommodated in properly planned and designed containment systems within the worked out part of the mine. In any open pit mining venture, transportation cost is approximately 40% of the mineral mining cost. In-pit dumping of overburden material is always preferred to minimise the cost of transportation. However, destabilisation of internal dumps, as seen in the recent past, hampers the smooth functioning of mining operations and severely affects economics. To ensure long-term stability, vis-a-vis enhanced capacity of internal dumps, scientific understanding and practical know-how is necessary.In this study, detailed stability analysis of internal dumps was done at one of the coal mines of Western Coalfields Limited, India. Pertinent physico-mechanical properties of the dump material were determined and used as inputs for numerical simulation. Four different methods were used in simulating and analysing the existing and optimised dump slopes. Stability analysis of dump slopes was carried out for monsoon season of the year, when dump material possesses least shear strength. Factor of Safety determined by different analytical technigues is presented. Also, distribution of stresses, strains, plastic points, tensile zones along with various failure surfaces were determined. Based on the results of numerical modelling, an increase of nearly 22% of the existing dump capacity is recommended, whilst maintaining a safe range of Factor of Safety.
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