ABSTRACT:
The paper deals with the geotechnical study and optimum ultimate pit slope design of Ashok opencast project with special reference to the highwall stability of slopes created by surface miner. It was also aimed to know the influence of slope design parameters on the safety factor by sensitivity analysis. Geotechnical mapping was done on the exposed benches of the surface mine as per the norms of International Society of Rock Mechanics. The different geo-mechanical properties of lithological units were determined. The failure analysis was done by GALENA software based on limit equilibrium method and optimum slope design was recommended.
1 INTRODUCTION
The geotechnical study was conducted for the optimum ultimate pit slope design of the highwall slopes at Ashok opencast project. The mine is producing 6.5 million tonnes per year. It is located in Jharkhand state of India and being mined by Coal India Ltd. The coal is of non-coking category and is suitable for use in powerhouses. It was also aimed to know the influence of slope design parameters on the safety factor by sensitivity analysis, which tells the importance of the parameter in the critical slope. A more justified and suitable remedial measure can be planned for any critical slope after sensitivity analysis. The geotechnical characteristics of joints in overburden and coal cleats were measured on the exposed benches of the surface mine as per the norms of International Society of Rock Mechanics (ISRM 1978). The different geo-mechanical properties of lithological units were determined at the Rock and Soil Mechanics Laboratories of CMRI. Initially the average orientations of the discontinuity sets determined from the geologic structural mapping were analyzed to assess kinematically possible failure modes involving structural discontinuities in the sandstone as well as coal slope faces.
