Geotechnical Characterization and WRCC for Spatially Varied Pond Ash within an Ash Pond

Abstract

Thermal power plants produce a large quantity of coal ash as a by-product from the combustion of pulverized coal. A small quantity of total coal ash produced is currently being utilized, whereas unutilized coal ash is deposited in vicinity of thermal power plant as waste material which covers several hectares of useful land. The utility of coal ash in various applications related to geotechnical and geoenvironmental field has been increased manifold. In most of these applications, thorough understanding of geotechnical characteristics and water retention characteristics curve of pond ash is required. There are not many studies that deal with study of effect of spatial distribution of pond ash within the ash pond on the geotechnical characterization and soil water characteristic behavior of ash. This paper presents the results of geotechnical characterization and water retention characteristics curves of pond ash which were collected from different locations from inflow to outflow of Ropar thermal power plant (India). Index properties and engineering properties (permeability, strength parameters) of ash changed significantly upon the spatial variation from inlet of slurry point to outflow of decanted water. Classification of ash changed from SM to ML as it is moved away from inlet to outflow point. Distinctly different drying and wetting curves were observed for ash samples collected from inflow to outflow points. Results revealed that inflow points exhibited higher specific gravity, low air entry value as compared to outflow points. Further, investigation was carried out to study WRCC hysteresis of samples collected from inflow to outflow in an ash pond. It is concluded from the results that coarse ash sample exhibits lesser degree of WRCC hysteresis. The results presented in this paper signify the importance of considering WRCC hysteresis for a pond ash samples spatially distributed in an ash pond. The results obtained for pond ash was also compared with the natural sand in order to make a comparison with natural sand for its possible replacement in place of sand in various civil engineering applications.