The rapid growth of coal-based power generation has led to a substantial increase in fly ash production, particularly in countries like India where coal contains a high ash content (30–55%). The safe disposal and management of this by-product have become major environmental and logistical challenges due to the requirement of large ash ponds and the risk of air, soil, and water contamination. This study explores the potential of utilizing fly ash as a backfilling material in underground mines, presenting it as a sustainable and efficient solution for bulk ash utilization. Underground mine voids offer significant storage capacity and provide an opportunity to convert waste into a valuable resource. The research reviews the physical and chemical characteristics of fly ash and evaluates its suitability for mine backfilling applications. The backfilling process not only enables safe disposal of fly ash but also improves ground stability by supporting overlying strata and reducing surface subsidence. Additionally, it enhances mine safety and facilitates improved resource recovery. The study highlights various backfilling techniques, material preparation methods, and transportation systems used in fly ash utilization. Special emphasis is given to Indian conditions, where the integration of fly ash in mining and construction sectors can significantly reduce environmental impacts while promoting sustainable development. The findings indicate that fly ash-based backfilling is a technically viable and environmentally beneficial approach that addresses both waste management and mining challenges. This approach contributes to circular economy principles by transforming industrial waste into a functional material for geotechnical applications. Overall, the study underscores the importance of adopting innovative strategies for fly ash utilization to achieve sustainable mining practices and environmental conservation.

Keywords:
Fly ash, Mine backfilling, Underground voids, Sustainable mining, Waste utilization, Ground stability