Mapping Surface Moisture of a Gold Heap Leach Pad at the El Gallo Mine Using a UAV and Thermal Imaging
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Mapping Surface Moisture of a Gold Heap Leach Pad at the El Gallo Mine Using a UAV and Thermal Imaging Mingliang Tang 1 & Kamran Esmaeili 1 Received: 24 April 2020 / Accepted: 5 October 2020 # Society for Mining, Metallurgy & Exploration Inc. 2020
Abstract An understanding of the spatial and temporal variations of surface moisture content over a heap leach pad (HLP) is essential for leaching production and to achieve a high ore recovery. The current practice of leach pad monitoring and data collection remains highly manual and labor-intensive, and exposes technical staff to hazardous material (i.e., cyanide solution). To address these challenges, we propose using unmanned aerial vehicles (UAVs) equipped with thermal imaging sensors to remotely obtain high temporal and spatial resolution image data for monitoring the surface moisture distribution over HLPs. A field study was conducted over a sprinkler-irrigated HLP at El Gallo gold mine in Sinaloa State, Mexico, and the acquired data were used to derive an empirical relationship between the surface moisture content and the remotely sensed surface temperature using linear regression. Moreover, the data were used to generate moisture distribution maps of the entire HLP surface. In situ samples were taken manually during the field experiments to measure the ground-truth material moisture at selected sampling locations. The results show a good agreement between the remote sensing method and the measured ground-truth samples. Keywords Heap leach pad monitoring . Remote sensing . Unmanned aerial vehicle . Moisture mapping . Gold leaching
1 Introduction Heap leaching (HL) is a mineral extraction technology which has been widely adopted in recent years due to its high economic feasibility for low-grade ore deposits. One of the key design factors of HL operations is that the moisture from leach solution is retained by the heap leach pad (HLP) material [1]. A high metal recovery requires a uniform leach solution coverage over the entire HLP surface because an uneven distribution of moisture can lead to challenging operational problems [2]. Lankenau and Lake [3] stated that a non-uniform distribution of surface moisture can lead to undesirable leaching agent percolation beneath the surface, resulting in a suboptimal leaching condition. According to Marsden et al. [4], an uneven distribution of moisture over the HLP can result in ponding on HLP. This may require a reduction in the solution application rate, which can further affect the scheduling of the HL operation. Therefore, a fundamental task in HL production * Kamran Esmaeili [email protected] Mingliang Tang [email protected] 1
Lassonde Institute of Mining, University of Toronto, 35 St George St, Toronto, ON, Canada
optimization is to collect representative data from the HLP to monitor production performance. However, the conventional data collection method relies on manual sampling and nakedeye observation of the HLP by technical staff, which exposes the personnel to hazardous material (i.e., c
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