Study and Analysis of Fly Ash for Stowing in Underground Coal Mine Voids

Abstract

About 73% of the India's total installed power generation capacity is thermal of which coalbased generation is 90%. Around 85 thermal power stations, besides several captive power plants use bituminous and sub-bituminous coal and produce large quantities of fly ash. High ash content (30% - 40%) coal contributes to these large volumes of fly ash. The country’s dependence on coal for power generation has never gone down. The term “fly ash‟ is used to describe any fine particulate material precipitated from the stack gases of industrial furnaces burning solid fuels. The amount of fly ash collected from furnaces on a single site can vary from less than one ton per day to several tons per month. The characteristics and properties of different fly ashes depend on the nature of the fuel and the size of furnace used. A cause of concern for the future is fly ash management. We have a lot of avenues for use of fly ash, yet we have not yet achieved 100 percent utilization of fly ash generated from coal based thermal power plants resulting in accumulation in ash ponds near the plant and creating environmental hazards to local community. Production of fly ash relies on the coal source, plant activities and numerous more factors. In the present study lime was added with fly ash to gain strength of fly ash to be placed in mine voids for filling purposes. Research facility tests were carried out in our laboratory to assess the strength gain in the fly ash by adding lime to it. Standard proctor hammer test, unconfined compression test, and tri-axial test were carried out to decide about its suitability for placement in mine voids where large amount can be utilized releasing a great stress to the environment. From the results of laboratory study using lime as an additive to the flyash encouraging properties are obtained for filling it in mined out areas. The aim of this study was to find a suitable utilization avenue for a particular fly ash sample depending upon its geotechnical properties and thus reduce the need for vast areas for disposal of fly ash which in turn causes considerable damage to the environment in the form of particulate matter in summer season. By filling these waste materials in underground mine voids this perennial problem of environmental hazard can be addressed suitably.