Assessment of Fly Ash and Mine Overburden Blends for Underground Backfilling

Abstract

Underground mining operations generate substantial volumes of overburden waste while coal-fired thermal power plants produce massive quantities of fly ash, creating significant environmental management challenges. This study evaluates the geotechnical performance of fly ash and mine overburden blends as sustainable backfilling materials for underground mine voids. The research examines various blend proportions through comprehensive laboratory testing including unconfined compressive strength, California bearing ratio, shear strength parameters, and compaction characteristics. Results demonstrate that optimum blend ratios of 70% overburden with 30% fly ash and 6% cement binder achieve unconfined compressive strength values of 4.01 MPa at 56 days curing period. The investigation reveals significant improvements in mechanical properties, with blends containing 20-30% fly ash exhibiting enhanced strength characteristics suitable for underground backfilling applications. Statistical analysis confirms the effectiveness of fly ash incorporation in modifying engineering properties while providing economical and environmentally sustainable solutions for waste utilization. The findings establish technical feasibility for large-scale implementation of these composite materials in underground mining operations, contributing to waste management, ground control, and subsidence prevention objectives.