Computational Analysis for the Stability of Black Cotton Soil Bench in an Open Cast Coal Mine in Wardha Valley Coal Field, Maharashtra, India

Coal is a prime source of energy in India and its demand is increasing every day due to faster rate of development and consumption of energy per capita. To bridge the gap between demand and supply of energy sector, there is a need for huge quantity of coal. The open cast mines are helpful to fulfill the demand to a large extent because of their higher productivity rate. Large quantity of overburden material is required to be removed to reach the underlying coal seams. Higher stripping ratio and increased depth of mines pose serious problem to the stability of mine slope due to variation in rock mass as well as mining method adopted. These problems are more chronic, where soft layers of black cotton soil occur in the slope, which behaves erratically in different environments. The bench slopes in Wardha Coal Field, face such kind of conditions, which are delicate when it comes to the safe mining activity. In this paper, an attempt has been made to simulate the condition of a black cotton soil bench imbedded in mine slope using two dimensional numerical tools. The study mainly focuses on the numerical examination of a failed Black Cotton Soil (BCS) bench, from Sasti Coal mine of Wardha valley coal held, which has translated forward by 5m on the berm. The 15m thick BCS bed is underlain by Kamthi Sandstone (KS). The numerical analysis was done under both saturated and dry conditions. This study also deals with the understanding on the effect of water on the stability of the bench slopes as the BCS usually fail during the rainy season. The numerical investigation after the exhaustive geotechnical examination found a 35% rise in factor of safety from saturated to dry condition