Design of Stable Slopes for Dumps Admixture with Flyash

Abstract

The waste dump has been a major issue in mining industries in recent years since there is a huge demand of minerals. With a limited availability of land there is more waste material to dump, Huge amount of fly ash is generated in India by coal fired thermal power plants. Here is a question about their disposal which leads to adverse effect on local environment. As per Ministry of Environment and Forests (MOEF) guidelines, at least 25% fly ash is used as back filled material in mine which is located within 50km from the power plant. In this project the stability of overburden dumps mixed with fly ash of JPOCCM mine of JPL Tamnar (Raigarh) was carried out by field monitoring using total station and monitoring stations. For the stability of OB dump, it was proposed to use fly ash mixtures. Different geo technical parameters such as cohesion, frictional angle and density were found out and were used to model the dumps in FLAC SLOPE software and OASYS software to find out the value of FOS. 1. The safe slope angle for 30m OB bench height for OB, OB+15% fly ash, and OB+30% fly ash were found out to be 29°, 26°, and 28° respectively. 2. From the analysis it is concluded that with increase in slope angle of the deck and height, the factor of safety decreases. With the addition of 15% fly ash the safe bench angle decreases by 2° due to partial filling of void space but when 30% fly ash were added then there will be an increase in 1° of safe bench angle. This is due to more void spaces that were filled with again 15% fly ash. Thus, the Factor of safety as well as safe slope angle are increased. 3. On comparison between OASYS and FLAC, they show same slope angle but different factor of safety. It is due to the change in grid size from medium to fine. Hence the results were changed. More over in OASYS it is assumed that the failure of surface to be moving in a direction lying in the arc of a circle. But in FLAC SLOPE the direction of failure may be in any direction. 4. From the analysis of total station monitoring it was found that both pits are stable due to the admixture of fly- ash and OB dump to be used.