Analysis of The Slope Stability of the Overburden Dumps Mixed with Fly Ash and Various Stabilization Techniques for Slope Stability

Abstract

Slope stability is the major issues associated with the overburden dumps in the opencast mining scenario. Statistical data reveals that more than half of the accidents occurring in the opencast working are due to the failure of the slope and reason behind this is the improper design of the benches and insufficient works on finding the geo- technical parameters. The most effective and simple way to cope with the slope failure are precise determination of the geo-technical parameters of the overburden dump and then proper designing of the benches using numerical modeling, water pressure simulation, Limit Equilibrium Method etc. The most influencing factors that contribute to the enhanced slope stability are: cohesion and angle of internal friction. In recent year a new trend has come i.e. using of fly ash mixed with the overburden dump. There are few reasons and advantages associated with this, like huge amount of the fly ash being generated from the thermal power plants raise a serious question about their disposal besides creating adverse effects on the local environment. According to Ministry of Environment and Forest i.e. MoEF’s guidelines, any mine situated within 50 km from a power plant must use at least 25% fly ash as its backfill material. In this project the stability of overburden dumps mixed with fly ash at KTK opencast mine of SCCL was studied. Coming to advantage with it is that optimum mixing of the fly ash with the dump raises the cohesion which imparts a better factor of safety than the conventional method of dumping. The reason for the increase in the cohesion of the fly ash and overburden dump mixture is fly ash has ability to bind the particles strongly. This project work exhibits the extensive study of the factors contributing to the slope stability, various stabilization techniques for slope stability, laboratory oriented works regarding finding the geo-technical parameters of the overburden and fly ash, and finally then optimum design of the bench of the overburden dump mixed with fly ash using the geotechnical parameters. For designing the bench numerical modeling software FLAC SLOPE is used. Dumps of 30 m height were modeled in FLAC SLOPE to find out the safe slope angle i.e. angles for which the factor of safety > 1.2.