Design of Embankment for High Concentration Ash Slurry Filling in Opencast Mines – A Case Study

Abstract

Disposal of coal ash on surface comes as a part and package for meeting the society needs for thermal power. The conventional method of disposing it in ash ponds leads to requirement of more than 3 lakh acres of valuable land for its construction and can have damaging consequences with respect to water, air and land pollution. Hence, the need of the hour is to utilize this ash in an environment friendly manner. This paper throws light on the scheme for high concentration slurry disposal of ash in abandoned portion of the mine and design of embankment to contain it against the highwall. Two most common method for embankment construction, viz. upstream and downstream was modelled to evaluate its factor of safety with the help of PLAXIS software. Downstream method of embankment construction showed promising results and was selected for further analysis. Numerical simulation was carried out with downstream mode of construction in drained condition with and without the incorporation of vertical and horizontal drains. The embankment with drains exhibited higher safety factor which decreased when the embankment was raised. The construction scheme involves raising of embankment with slope angle of 27° in eight stages of ten meters height each and filling it with high concentration ash in layers. In the final stage, the top soil of 5m thick is proposed to be spread for revegetation.