Geoenvironmental aspects of coal refuse-fly ash blends

TR Number



Journal Title

Journal ISSN

Volume Title


Virginia Tech


The separate land disposal of coal refuse and fly ash presents difficulties throughout the Appalachian region, both in terms of disposal costs per acre and in terms of its potential environmental impacts on soil, ground water, revegetation, and slope stability. The purpose of this study was to determine how fly ash addition to coal refuse would impact on certain geotechnical properties of the refuse disposal piles, and whether the refuse-fly ash blends would be suitable as co-disposed materials. Accordingly, the compaction, permeability and shear strength characteristics of the refuse-fly ash blends were experimentally determined for varying fly ash percentages. The compaction test results indicated that, with increasing fly ash, the maximum dry density of these blends marginally decreased. The permeability test results showed that the permeability of the test specimens progressively decreased with the increase in fly ash. The shear strength results demonstrated that the addition of fly ash did not significantly influence the shear strength of the refuse. The critical factor of safety determined during slope stability analysis revealed that the tested slope geometries were stable for long term, drained conditions (using the STABGM computer program). The volume change analysis determined that there was a minimal expansion in the volume of refuse when it was blended with fly ash. However, it may be noted that all the stated results depend on a number offactors, including the nature of the refuse and fly ash used. Therefore, these findings would be specific to bulk blends of coal refuse and fly ash only. In general, this study indicates that fly ash can be beneficially reused with respect to the geotechnical properties evaluated. Co-disposal of fly ash and coal refuse may be a reasonable alternative to present disposal methods.