Characterization of particle size segregation and heterogeneity along the slopes of a waste rock pile using image analysis

Abstract

Large amounts of waste rock are produced during mining operations and often disposed of in large piles. Particle size segregation usually occurs during waste rock disposal, which can lead to high variations of particle size distribution (PSD) along the pile slope, increasing the risk for hydrogeotechnical instabilities. Determining segregation in situ is, therefore, critical to implement control measures and optimize deposition plans. However, characterizing PSD at field scale remains challenging because of the large dimensions of the pile, the instability of the blocks and the steep slopes. In this study, images, covering a 1400 m wide and 10 m high section of a waste rock pile, were taken and analyzed using image analysis to characterize segregation along the slope of the pile. PSD curves in different sections along the slope were determined and the segregation degree and characteristic diameters (e.g., D10, D50, D80,D95) were quantitatively compared. Results allowed to quantify segregation along the vertical direction of the pile, showing that segregation degree increased from − 0.77 ± 0.39 in the top (finer zone) to + 0.4 ± 0.14 in the bottom (coarser zone). Significant lateral heterogeneity was also observed with maximum diameters varying between 80 and 180 cm in the bottom section. Such segregation and lateral heterogeneity could induce significant variations of waste rock properties, with, for example, hydraulic conductivities varying by more than 2 orders of magnitude within the pile.

Particle size distribution (PSD) estimation using unmanned aerial vehicle (UAV) photogrammetry for rockfill shear strength characterization

“…However, these techniques are ineffective for low to intermediate normal stress [37]. Inverse correlations between particle size and strength can lead to decreased particle crushing in finer samples, while sizeshape correlations might cause increased crushing in finer samples comprised of more elongated grains [35]; vertical and lateral segregation can result in overestimation or underestimation of the final shear strength; this is due to significant lateral heterogeneity, which causes considerable variations in the geotechnical properties of waste rock in practical scenarios [83]. It follows, by analogy, that friction angles of field samples, when evaluated using the scalping scaling-down technique, can be accurately predicted.…”

Study on the Influence of Particle Size Distribution on the Separation of Pyrite from Coal Gangue by Jigging

“…The study of the particle size distribution of fine powder has been applied in many aspects [27,28], but there are still few studies on jigging separation by particle size distribution. In view of this, taking coal gangue as the research object, the raw ore is crushed to −2 mm by a jaw crusher and sieved, and the cumulative distribution curve is drawn with the particle size as the horizontal coordinate, and the determination coefficient R 2 [29][30][31] is used as the determination index to determine the distribution curve of the raw ore.…”