Evaluation of Underground Coal Pillar Design

Abstract

Mining is the extraction of valuable minerals or other geological materials from the earth, usually from an ore body, vein or (coal) seam. Mining involves different processes like prospecting for ore bodies, analysing the feasibility of extraction, profitability of the operation, extraction of the desired materials. One of such methods is the Bord and Pillar method of mining which is one of the oldest methods of mining. The success of Bord and Pillar mining is selecting the optimum pillar size. If the pillars are too large, then the extraction ratio decreases leading to less profitability and if the pillars are too small it endangers the overall mine safety. Indian mines have about 60 % of the coal blocked in the form of pillars. This investigation critically reviews the different practices of pillar design followed around the world in general and evaluates the existing practices of an Indian mine in particular. Geotechnical factors of a nearby underground coal mine has been determined in the laboratory. Different approaches of pillar design have been compared. Variation of safety factor with width to height ratio of pillar, extraction percentage and depth of cover has been determined and conclusion has been made. The safety and feasibility of mining method is obtained through an optimum correlation between safety factor and extraction percentage.