Geo-hydrological Stability Analysis of Fly Ash Stabilised Overburden Dump Slopes in Opencast Coal Mines Using Finite Element Analysis

Abstract

Fly ash is one of the major waste line products in coal power sector and simultaneously one of the most desirable products in the construction industry, due to its pozzolanic nature. This has resulted in fly ash being used as a partial replacement of cement and in various composites, for civil and mining industries. Recent studies and applications have shown the viability of fly ash as an economical and eco-friendly stabiliser for dump slopes in opencast mines. Apart from the analysis of structural stability due to the pozzolanic binding nature of fly ash, it is also important to study the hydrological aspects of dump slopes in conjugation with the fly ash stabiliser. This study performs the numerical simulation for the dump slopes using finite element analysis (FEA) for studying the effect of fly ash stabilisation layer on water movement and associated hydrological investigation. The effect of water head build-up (due to fly ash stabilisation layer) on the overall stability of dump slope is analysed and compared to give an estimate for the increase in a factor of safety of slope and a viable dimensional increase of slope geometry. It is seen that fly ash layer stabilisation is effective even in the saturated state of overburden dumps, with the factor of safety increasing from 1.09 to 1.32. Proper drainage channels are found to be essential to prevent any excess stress build-up due to the low permeability of fly ash layers.