Internal Erosion Induced Instability of Coal Ash Ponds: Forensic Analysis using Smoothed Particle Hydrodynamics (SPH)

Abstract

Coal-based power generation will continue to be the backbone of energy supply until renewable energy sources become mainstream. Hence, management of large quantities of coal ash generated as a by-product is a global concern. Coal ash is commonly disposed in ash ponds and is prone to internal erosion because of low specific gravity. The consequent breach of an ash pond may result in severe socioeconomic impacts. Thus, design and analysis techniques incorporating internal erosion are essential for constructing resilient ash ponds. This study investigates the effect of internal erosion on the stability of ash ponds using a five-phase SPH model. The approach is utilised for analysing an operational ash pond from India, where instability due to internal erosion was observed. The results indicate that the amount of erodible fly ash significantly influences the initiation of instability and the subsequent mass flow, with close to 100 % reduction in mass flow as the fly ash content is reduced from 80 % to 20 % by weight. The study also highlights the significance of appropriate coal ash slurry disposal practices and field monitoring for averting such failures. Further, replacing the erodible coal ash with a non-erodible material is validated as a feasible failure mitigation measure.