Development and Demonstration of High Concentration Fill Technology on Utilization of Fly Ash as a Filling Material for Underground Coal Mines

A relatively new technology, high concentration backfilling, enables mining industry to think on the use of fly ash as underground back fill material. The advantages are enormous. Jharia and Ranigunj coalfields being the oldest in the country had adopted unscientific mining during pre-nationalization period. In many cases mining was conducted without proper stowing and that had resulted in severe problem in these two townships. Both these townships are suffering from severe problems of subsidence. It is anticipated that with the development of this technology it will be possible to solve this intractable problem. The problem of underground fire can also be controlled once this technology is adopted. Due to over exploitation sand for construction industry and nonreplenishment of sand in the rivers due to construction of dams at the upstream, sand is gradually becoming a scare material. It is anticipated that it will be extremely difficult to get plenty of sand for stowing purpose in future. So the time is ripe to search for alternate material to replace sand for underground stowing. A survey conducted by CMRI indicates that there are about 25 power plants situated within a distance of 20 Km. of underground coal mines using sand as stowing material at different coalfields of India. These power plants are producing a huge quantity of fly ash which can be used as an alternate stowing material. Ash has several other advantages compared to sand as a stowing material. Once this technology of ash stowing is developed with high concentration form, it will be possible to get a very high rate of stowing which will eventually increase the coal production from depillaring panels.