E-proceedings of the 38 th IAHR World Congress September 1-6, 2019, Panama City, Panama doi:10.3850/38WC092019-0428 5080 COPPER CONCENTRATE AND GRAVEL BEDS BUSTAMANTE-PENAGOS N. (1) & NIÑO Y. (2) (1) Universidad de Chile, Santiago, Chile e-mail: nataliabustamante@ug.uchile.cl (2) Civil Engineering Department and Advanced Mining Technology Center, Universidad de Chile, Santiago, Chile, e-mail: ynino@ing.uchile.cl ABSTRACT Mining accidents can pollute gravel bed rivers with fine, metal materials, in particular with copper concentrate. This research shows the experimental advances on the spill of copper concentrate in gravel beds, with two approaches; first, in a flume with a bed and second, in a sediment column with surface flow and subsurface flow. Particle Image Velocimetry was applied for the measurement of the flow velocity before and after the spill, finding a maximum decrease of 9% in the bed shear stress. On the other hand, considering both facilities, the thresholds to characterize unimpeded static percolation and bridging, as types of percolation, were specified. Keywords: Percolation; copper concentrate; suspension; unimpeded static percolation; bridging 1 INTRODUCTION The Chilean geomorphology in the regions north and center of the country are controlled by Los Andes Mountain range. This lithological control leads to high slopes and gravel bed rivers. Niño (2002) reported median sediment size between 0.3-250 mm and slopes between 0.04-8.61%. On the other hand, mining is the most common economic activity in those regions, that is, the extraction, refining, and exportation of copper concentrate. Mining is located far from the ports where the copper concentrate goes or the places where the tailings are placed, so the material is transported through pipelines or channels, which are nearby to rivers. Hence, mining accidents, for example, pipeline failure, have a high environmental impact on water resources, because mining materials contain toxic material and heavy metals. For example, naming a few accidents, failures in the dam of Harmoni Golden mine spilled 2.5 Mton of tailing that destroyed the mining village of Merriespruit, South Africa (Van Niekerk & Viljoen, 2005); failures in a valve generated 45 m 3 spill of copper concentrate into the Choapa River, Chile (El Ciudadano, 2009); breakdown of an underground pipeline spilled 50 m 3 of copper concentrate into the Blanco River, Chile (La Tercera, 2016); the breakage of the tailings dam at Mount Polley spilled 25 Mm 3 into the Hazeltine Creek, Quesnel Lake and Polley Lake, Canada (Byrne et al., 2015); a failure of Fundão tailings dam spilled 43 Mm 3 into the Doce River to the Atlantic Ocean, Brazil (do Carmo et al., 2017). On the other hand, the contamination of gravel-bed rivers with a fine material has high environmental impact. Due to the presence of fine sediment in the bed, it could change the roughness, velocity field and shear stress (Niño et al., 2018; Sambrook et al., 2005). Additionally, there are changes in the hyporheic zone because the fine particles can change the permeability by filling the pores of the sediment (Mcdowell-boyer et al., 1986). Several researchers have studied the pollution of gravel bed with sand or glass spheres as fine material. Einstein 1968 in Diplas & Parker (1985), Beschta & Jackson (1979), Cui & Parker (1998), Diplas & Parker (1985), Iseya & Ikeda (1987) researched experimentally the percolation dynamics of fine sediment into the gravel beds. They reported that the percolation depth depends on the size of the coarse material. They also identified two mechanisms of percolation such as unimpeded static percolation and bridging. Additionally they could not find a relationship between the hydraulic parameters and the percolation depth. On the other hand, Cui & Parker (1998) proposed that the gravel porosity is a reservoir for the interstitial deposition of fine sediment. Cui et al. (2008) could report a decrease in the accumulation of fine sediment deposited with depth into the substrate. Several studies show different thresholds to characterize the percolation type, such as the relationship of the sediment sizes, for example, Beschta & Jackson (1979), Gibson et al. (2009), Huston & Fox (2014), Dudill et al. (2016). In fact, when sands are the pollutant material, typical mechanisms of sediment transport are observed, and its advance is a wavefront (Niño et al., 2018). Nowadays, not too many papers have used mining materials as pollutants. Aceituno (2017) studied the pollution of gravel bed with tailings as fine material, finding that tailings are deposited in sort of dunes in the gravel bed and advance is not a wavefront but is in individual particles. Bustamante & Niño (2018) and Bustamante et al. (2017) used copper concentrate as fine material. They found that the movement of copper