Optimization of ash content in overburden dumps: a numerical approach

摘要

Coal mines and associated power stations generate significant waste volumes, including mineoverburden (OB) and ash (both fly and bottom ash).The current practice of wastemanagement (OB and ash) in these industries around the world consists of disposal to eitherdumps or landfills. The safe and successful management of huge volumes of ash representsa major challenge - especially with the scarcity of land space available. An important stepforward in the coal mining-power generation complex is to increase the utilization of ash.The conventional utilization techniques (ash in backfilling operations, construction bricks,etc.) have certainly helped these industries, but still they are far from complete.This paper examines the utilization of ash in stabilization of overburden dumps inopencast mines. The safety of waste dumps is of key economic importance in mine planningand has been among the important challenges for surface mines. Using ash as stabilizerreduces the disposable ash volumes and also helps to increase the effective slope angle anddump height due to the strengthening properties of ash when mixed with appropriateconstituents. The geotechnical properties of such mixtures capable of strengtheningoverburden material were identified in laboratory experiments and mine dump slopes werenumerically simulated on software based on the finite element method. Variations in dump;bench height, slope angle, and thickness were carried out in numerical simulator for judgingtheir factor of safety (FoS) by finite element analysis. It was observed that the FOS increasedwith use of ash layer to a certain optimum value beyond, which it plateaued. The optimumheights, thickness and angle of slopes in the use were found for each case. This impliespossible improved design of overburden dumps capable of holding larger quantities of OBin same volume with higher degree of safety. This further improves the economics of themine as well as helps increase the utilization of fly ash, hence creating a multidimensionaladvantageous scenario.