Stability analysis of mine overburden dump stabilized with fly ash

Stability of mine overburden (OB) dump slope has been a major concern over the years and needs a proper design for safe mining operation and economy of project. Incorporation of fly ash along with the OB materials may provide an alternative mode of fly ash utilization and stability of OB dump. In the present study, fly ash was mixed at a different percentage with OB material to evaluate various geotechnical characteristics. Numerical modelling based on the finite difference method was carried out to assess the stability of fly ash mixed OB dump and to suggest the optimum dump height. The result indicates that addition of 10% fly ash by dry weight with OB material results in 21.38% and 16.31% higher California bearing ratio value than CBR value of native OB material under unsoaked and soaked conditions, respectively. The maximum unconfined compressive strength and cohesion values are observed for the OB material mixed with 20% fly ash. Based on the stability analysis, optimum dump height of 55 and 50 m is observed for 35° and 37° slope angle, respectively, with an addition of 10% fly ash with OB material. The decrease in shear strain rate and the vector velocity with the addition of fly ash makes it suitable to utilize with OB material. Mathematical expression presented in this paper provides a reliable prediction of factor of safety.Abbreviations: ASTM: American Society for Testing and Materials; CBR: California Bearing Ratio; EDX: Energy Dispersive X-ray; FLAC: Fast Lagrangian Analysis of Continua; FOS: Factor of Safety; MDD: Maximum Dry Density; OB: Overburden; OMC: Optimum Moisture Content; SEM: Scanning Electron Microscope; SSR: Shear Strain Rate; UCS: Unconfined Compressive Strength; V.V. : Vector Velocity