Application of aerial image analysis for assessing particle size segregation in dump leaching

Understanding the behaviour of fluid flow through packed ore/rock beds is essential for estimating metal extraction from low-grade ores via dump leaching as well as the release of toxic elements from mine waste rocks. One fundamental factor that determines the flow behaviour in ore/rock beds is particle size distribution. Given the limitations presented by the traditional sieve analysis, we applied aerial imagery to investigate the particle size distribution in ore piles. Using dump leaching as an example, we analyzed the aerial images of a dump leach pad acquired by a camera installed on a drone while the leach pad was under construction. The image analysis results showed that the dump leach pad contained an extremely wide range of particle sizes. A spatial segregation of fine and coarse particles was observed. The widely used P80 was deemed to be questionable to represent particle size distribution in dump leach pads. The Sauter mean diameter (d32) and the dump permeability were found to increase with depth. The technical method described in this study provides a more convenient and reliable tool for particle size distribution analysis, thereby facilitating future studies that will enhance understanding of metal extraction from low grade ores in leaching operations as well as the potential release of pollutants from waste rock piles.