A significant amount of coal is left behind underground when using traditional mining methods in underground coal mines. To overcome this problem, researchers from the Mining Engineering Department at the Visvesvaraya National Institute of Technology (VNIT) have developed a new technology. Researchers claim that this technology has the potential to excavate up to 95 per cent of extractable coal. The researchers have also received a patent for this technology. Associate Professor Dr A K Agrawal and Assistant Professor Dr Anupam Anant Khere from VNIT developed this method after about a year and a half of research. The patent is titled ‘A Method for Underground Coal Pillar Extraction Using Continuous Miner with Real Time Backfilling’. In this technology, a system has been created to backfill the voids created during the extraction of coal pillars in the ‘board and pillar’ method simultaneously. Currently, the ‘sand stowing’ (sand filling) method is primarily used to fill the void created after excavating coal from underground mines. However, because the sand-filling speed is lower compared to modern machinery like the ‘continuous miner’, the pace of extraction and backfilling does not match.

 

Therefore, there was a need to develop a backfilling method compatible with the speed of modern machinery. In the method developed by VNIT researchers, coal pillars are divided into smaller sections and extracted sequentially using a ‘continuous miner’. As soon as the coal is extracted, pumpable backfill material is discharged into the newly created void. Simultaneously, measures such as ‘roof bolting’ are undertaken to support the mine roof. In the ‘board and pillar’ method, using traditional technology, generally 60 to 65 per cent of extractable coal is extracted. The remaining coal remains underground due to safety parameters, geological conditions, and technical limitations. For example, if a mine has 100 million tonnes of extractable coal available, about 60 to 65 million tonnes of coal is extracted using traditional methods, while the remaining 35 to 40 million tonnes stays underground. With the proposed technology, this recovery could reach up to approximately 95 million tonnes. However, the actual recovery rate will vary depending on geological, geo-mechanical, and local site conditions, requiring testing in individual mines. Because the processes of mining, roof support, and backfilling voids are carried out in a coordinated manner, the likelihood of creating large, unsupported voids in underground sections will decrease. Consequently, stress on the strata can be reduced, roof stability maintained, and mining safety enhanced. Fly ash, mine waste, and other industrial residues can also be utilised as backfill material in this technology.