Stability Evaluation of an Opencast Coal Mine with Difficult Ground Conditions: A Case Study

Any nation's ability to grow is reliant on the expansion of its various industries, each of which adds to the GDP of the nation. With a 2.5 % GDP contribution, the mining industry is one of the major sectors. In mining, coal is an important and abundant fossil fuel in India, and it accounts for 55 % of the country’s energy needs. The increase in coal production can be largely attributed to the rapid increase in open-cast mining activities and intensified mechanization. This has resulted in the opencast mines going deeper day by day with a maximum stripping ratio of 1:15, at a depth of about 500 m. For any opencast mine, a safe, properly designed, and scientifically engineered slope is essential for the economical, safe, and successful operation. In this paper, the stability evaluation of the pit slope at Bhanegaon Opencast Mine of M/s Western Coalfields Limited (WCL), which is centrally located Coalfields in India has been carried out. The loose and saturated thickness (20 m to 57 m) of the alluvial deposit (mixed with Black Cotton soil and sludge) with Kamthi series formation has high transmissivity which creates a stability problem. In this study, the slope stability analysis has been performed by using the computer program RocScience two dimension (RS2) to assess the effect of difficult ground conditions on stress distribution pattern and safety factor of pit slope. Sections were obtained by Terrestrial Laser Scanner (TLS) and analysed with the help of RS2 software. From the analysis, it was found that the Stress Reduction Factor (SRF) of sections where sand/clay band is present was less compared to other working areas because the cohesion of the upper layer material was less.