DEVELOPING A DEVICE AND A METHOD FOR REMOVING STALE TAILINGS FROM A RIVER -TYPE MOTHBALLED TAILING DAM

The upstream valley-type tailings dam exhibits a longitudinal profile that resembles an inverted triangle or a shape approximating an inverted triangle. This unique dam structure and its mechanical characteristics mean that the influence of longitudinal stress on the stability of the dam cannot be overlooked. However, the two-dimensional Swedish slip circle method calculation model does not take into account longitudinal stress, necessitating the development of a three-dimensional model specifically for the stability analysis of upstream valley-type tailings dams. Utilizing the Beijing Lizheng Geotechnical Calculation Software 5.3 standalone version, a three-dimensional calculation model was constructed based on the Swedish slip circle method. Taking the Cangyuan Jinla Lead-Zinc Mine tailings dam as an engineering example, this model was used to calculate five cross-sections, including 1–1′, of the dam. The results were then compared and analyzed with those obtained from the Swedish slip circle method, the simplified Bishop method, and the Janbu method. Using this three-dimensional model, the safety factors for cross-sections 1–1′, 2–2′, 3–3′, 4–4′, and 5–5′ of the tailings dam were calculated to be 2.798, 1.348, 1.332, 1.466, and 2.134, respectively. Analysis concluded that the most dangerous sliding surface of the tailings dam is located at the 3–3′ cross-section, with an overall dam safety factor of 1.332, indicating that the tailings dam is in a relatively stable condition. The safety factor of the tailings dam calculated using the finite element software MIDAS is 1.3531, verifying the accuracy of this three-dimensional model. For upstream valley-type tailings dams, the results from ordinary two-dimensional models tend to be on the dangerous side and thus should be corrected using this three-dimensional model to obtain more accurate and conforming safety factors.

Non-coal mining generally produces a large amount of tailings, and tailings usually accumulate in the canyon between two mountains, and the downstream of the tailings is intercepted by the dam. The dam is called a tailings dam. The development of safety monitoring technology for tailings dam is accompanied by the history of dam construction. The safety of tailings dam is not only related to the normal operation of mining industry, but also to the life safety of downstream residents. Once the tailings dam break, the loss caused by the dam is inestimable. In this paper, the laser collimation system is used to monitor the displacement of the dam, and the center of light is measured by the center of gravity, and the laser beam is reconstructed by a lens. The method has the advantages of high accuracy and simultaneous detection of horizontal displacement and vertical displacement of tailings dam. It is a new monitoring technology for dam displacement and has good application prospects.

Residues of industrial mining activities like rock waste, tailings, and stockpiles are amongst the largest human-made structures in both area and volume. In the case of tailings dams, the risk posed by failure is well documented and has led to the implementation of regulatory standards. As one of the measures to reduce potential harm to the environment and people, the Global Industry Standard on Tailings Managment (GISTM) implemented by UNEP in 2020 proposes the installation of "monitoring systems to manage risk at all phases of the facility lifecycle". This is one of the objectives of the EU-funded project MOSMIN (Multiscale observation services for mining-related deposits), which strives to develop holistic, full-site services for the geotechnical and environmental monitoring of mining-related deposits through the combination of Earth observation with in situ geophysical data. The integrated data sets should then be leveraged by using modern analysis approaches like machine-learning to characterize deformations and identify environmental hazards. In this work, we present the in situ geophysical campaigns conducted to acquire passive seismic data at two tailings dam facilities both related to copper mining, namely the tailings storage facilities of the FQM Trident mine in Kalumbila, Zambia, and the Codelco Chuquicamata mine near Calama, Chile. Both installations combine conventional seismic sensors with the deployment of a fibre-optic sensing array over targeted tailing dam sectors, for the continuous recording of ambient seismic noise. The main goal of this approach will be to both characterise the internal structure of the dams underneath the fibre-optic array and to monitor subsurface processes at different scales, resolutions and depths of investigation. We aim to apply several seismological methods for structural and material property characterization, the investigation of temporal changes in seismic properties and the evaluation of material contrasts in the body of the tailings dam. Suitable methods are ambient noise tomography and horizontal over vertical spectral ratios (H/V). Details of both setups like instrument deployment, fiber cable and trajectory, the procedure and construction of the layout, as well as preliminary results will be discussed.

The presence of lenses such as tailings slurry, frozen soil, and saturated zones disrupts the continuity of tailings dams and their normal seepage patterns, elevating the seepage line of the dam body and significantly impacting local stability. This study, to investigate how lenses affect the stability and failure mechanisms of tailings dams, employs numerical simulation and physical models and constructs a model of the tailings dam, incorporating tailings clay lens and void lens, to investigate variations in hydraulic gradients, seepage velocities, seepage flow, pore water pressure, and the patterns of seepage failure. This research reveals that the tailings clay lens within the dam body increases the hydraulic gradient in its vicinity due to its low permeability and raises the phreatic line. As the tailings clay lens approaches the dam body, the phreatic line tends to escape along the upper part of the lens towards the dam surface. In addition, the void lens could lead to a more pronounced seepage gradient along its path on the dam surface, with a liquefaction beneath it. As the void lens nears the toe of the slope, the dam failure mode transitions from a step-like progressive failure to an arch-shaped settlement failure along the void lens.

The tailing flow generated after dam failure will evolve into Geo-hazards like debris flows. Therefore, it is of great significance to study the evolution and influence range of tailing flow for disaster prevention and mitigation. Physical model experiments and numerical calculation are two major methods in Dam-failure research. These two methods can verify and complement each other, because the former can modify parameters of the latter and the latter can expand the research scope. In this study, a proposed tailing dam was simulated and calculated by using physical model experiment and simulation (Ramms). The erosion process of the dam body of the tailing flow was monitored by the model experiments. The numerical calculation parameters were adjusted to make the results closer to the actual conditions. This study aim to verify the reliability and effectiveness of the debris flow Ramms based on Voellmy model in dam failure simulation. The experiment showed that the velocity (Vmax =38.3 m/s), submerge area (Smax=0.558 km2) and the deposition depth (Hmax=36 m) of the tailing flow. It reflected that the Voellmy model can predict the flow state of tailing flow in the physical model experiments. So it can provide theoretical support and technical reference for the design and management of tailing dam.

Factors which play a role in acid mine drainage (AMD) formation were investigated over a period of 12 months. These include climatic, mineralogical, hydrological and oxygen diffusion parameters. The oxygen diffusion data reveal that the flow of oxygen in the Witwatersrand tailings dams is controlled by secondary porosity (i.e. cracks caused by roots on the dam surface). The age of the dam does not have a significant bearing on the extent to which the oxidised zone development and subsequently AMD can progress. Most of these processes take place within the first 3 m of the dams. The amount of rainfall plays a crucial role in determining the extent to which an oxidised zone progresses. The average oxidised zone in the 5 sites is 2.4 m ranging from 2.2 to 3.5 m. Water SA Vol.32 (4) 2006: pp.499-506

Embankment dams' failure is often caused by overtopping during flood wavecaused by insufficient spillway capacity.Failure can also be caused by progressive seepage through the dam's body as a result of increased contact seepage alongside an internal manmade waterway.Other causes for dam failure, include: slope instability of embankment dams, damages in the dam body caused by earthquakes, liquefaction of earth dams under static and seismic action, and flood waves caused by earthquakeinduced landslides into the reservoirs from the valley sides [1].According to ICOLD, the most common reason for embankment dams' failure is overtopping -3035% of all registered cases.During dam failure, as result of the immediate discharge of the impounded water in the reservoiror impounded flotation tailings at tailings waste lagoon -in the downstream river valley, a catastrophic flood wave makes its hazardous way towards destruction.Normally, the time needed for the flood wave warning system to activate, is much shorter than the time needed for the formation of the flood wave caused by rainfallrunoff.Thereafter, depending on the location of the dam, a potential dam failureespecially in case of tailings dam failurecould result in catastrophic losses of human lives, destruction of agricultural land and long-term degradation of the environment.In this manner, as follows, results of 2D analysis for flood propagation at a cascade system of tailings dams Sasa 3-2 and Sasa 4 are analyzed.Both cascade dams are located in the northeast part of RN Macedonia, on river Saska.The analysis is conducted with the use of the software program HEC RAS.

Summary Water consumption related to the life cycle of metals is seldom reported, even though mines are often situated in very dry regions. In this study we quantified the life cycle consumption of groundwater and fresh surface water (blue water footprint [WF blue ]) for the extraction and production of high‐grade copper refined from both a copper sulfide ore and a copper oxide ore in the Atacama Desert of northern Chile. Where possible, we used company‐specific data. The processes for extracting copper from the two types of ore are quite different from each other, and the WF blue of the sulfide ore refining process is 2.4 times higher than that of the oxide ore refining process (i.e., 96 cubic meters per metric ton [tonne] of copper versus 40 cubic meters per tonne of copper). Most of the water consumption (59% of WF blue ) in the sulfide ore process occurred at the concentrator plant, via seepage, accumulation, and also by evaporation. In the oxide ore process, the main user of water is the heap‐leaching process, with 45% of WF blue . The crushing and agglomeration operations, electrowinning cells, and solution pools are also significant contributors to the total consumption of water in the oxide ore process. Most of the water consumed in the oxide ore process was lost to evaporation. The WF blue of the oxide ore process can be reduced by preventing water evaporation and using more sophisticated devices during irrigation of the leaching heaps. The WF blue of the sulfide ore refining process can be reduced by improving water recovery (i.e., reducing seepage, accumulation, and evaporation) from the tailings dam at the concentrator plant. Using seawater in the production of copper is also a promising option to reduce the WF blue by up to 62%.

Not long ago, certain iron ore processing plants in Brazil were unable to efficiently recover iron ore fines and, as a result, operated only with high grade iron ore. For this reason, material stored in some iron ore tailings dams have considerable amounts of iron content with a potential to produce pellet feed fines through a concentration process. This study presents the results of magnetic concentration tests carried out on samples from four iron ore tailings dams located in Minas Gerais, named as A, B, C and D. The average iron content is 54% for A dam, 36% for B dam, 49% for C dam, and 58% for D dam. This material had a significant amount of ultra-fine particles, with more than 50% below 0.045mm for all dams, particularly the A and D dams, which present more than 80% of the below 0.045mm on average. Magnetic concentration tests were conducted on bench and pilot scales. The resulting concentrates showed the following average iron content: 66% for dam A, 63% for dam B, and 67% for dams C and D, with a mass recovery of 42% for dam A, 38% for dam B, 75% for dam C, and 63% for dam D. These results confirm the potential for pellet feed production from tailings dams through magnetic concentration.

paper deals with high ecological risk situation caused by the hydraulic structures state in the Tyrnyauz tailings dam (Gizhgit River valley mouth part), conditions of the water and debris flow discharges passing. Using publications and multi-temporal satellite images analysis authors provide data on the Fundão and Córrego do Feijão (Minas Gerais, Brazil) tailings dam disasters with human losses in 2015 and 2019. Based on this background, it’s described specific features of the situation developing around the Tyrnyauz tailings dam, which has not been functioning since 1997 and contains finely dispersed and toxic products of tungstenmolybdenum ore processing. It’s characterized possible, but not previously taken into account results of the impact of Gizhgit River debris flow and suspended flow on the tailings dam. Analysis of 2002 and 2014 critical situations is conducted. State of hydraulic structures not adapted to the current situation is assessed. It’s noted that there is a high degree of general risk. There are recommendations for preventing an unforeseen but real ecological catastrophe danger. Possibility of dam and banking stability loss during seismic impact is shown. Authors noted that inflow of seepage toxic waters into the Baksan River cannot be allowed. It’s concluded that there is the necessity to develop the comprehensive project for solving the problem and priority measures for its implementation. Authors emphasize the possibility of more significant consequences for the population and infrastructure in the Baksan River valley, downstream the Gizhgit River mouth (Bylym village) in comparison with the Brazilian events of 2015 and 2019.

Filtered tailings (FT) deposition is experiencing a worldwide growing application as a potential alternative to overcome several constraints associated with land use and fresh water availability in areas near mining operations. Implementation of FT deposition can significantly reduce the volume of the tailings dam; the result is a lower impact on the project development area compared to conventional slurry and thickened tailings deposits. Furthermore, the associated costs and the physical and environmental risks, during both the overall tailings disposal operation and closure, may be significantly reduced. Water and land use can be reduced not only in arid to semiarid regions, where the FT technology is currently being applied, but also in rainy regions. A comprehensive study of the implementation of the FT technology is required because of two major issues: (1) project development areas characterised by total annual rainfall higher than 1,000 mm and seismic activity higher than 8 Mw, and (2) very fine tailings types generated in the mine process plant. These factors push geotechnical-geochemical engineering knowledge to the limit and make the industry develop novel technologies for tailings filtration and transportation to meet new necessities. This paper presents geotechnical-geochemical considerations, including the rheological, thickening, filtering, and desiccating tailings characteristics obtained through an extensive laboratory testing program. The testing program examines a number of key parameters: the density and moisture requirements for the FT compaction, the criteria for the required area for the FT deposition for its subsequent compaction, criteria to meet the long-term physical and chemical stability during the FT disposal operation and closure, and the associated water management plan. This paper also describes experience regarding the criteria for the selection of FT equipment and transportation systems, their implementation and operation, and the operation and management of the FT deposit as a whole. Finally, future trends of FT applications associated with both the new generation of tailings filtration and transportation systems and the combined application of other tailings disposal technologies, such as the co-disposal of tailings and mine waste, are discussed.

Water recovery has become a critical issue for brown field and green field projects in the last couple of years, especially when mining takes place in hot and dry or mountainous areas. Where process water and energy costs are key components, dry stacking and mine back filling should be carefully compared to tailing dams in order to determine which technologies give clear high water recovery in the most cost effective way with the added benefit of reducing the risk of dam failures. High water recovery technologies should be considered where the process is conducted with sea water, where the cost of water is high, where space is limited, where tailing dams are restricted by law, or where the production capacity is limited by water availability. Pre-feasibility studies show that high water recovery technologies make it possible to decrease power consumption, reduce maintenance costs, and decrease the use of flocculants. It also means that a high level of process water recovery is possible. Consequently, the flow sheets for bulk material dewatering all over the world should be reviewed to increase plant efficiency by means of bigger and more efficient equipment. Outotec develops, designs, and manufactures industrial filters and is a leading technology company in its field. Companies in mining and metallurgy, chemical processing, and related industries benefit from our high-performance, high-efficiency process solutions, technologies, and products. Our focus in technology development is to achieve an optimum water recovery while at the same time satisfying the growing demand for handling huge tonnages. Hence, this paper shows new ways of treating tailings using bigger and more cost effective technologies.

Tailings slurry storage and management continues to be a significant consideration for the safe and environmentally complaint operation of a coal processing facility. Further, as the scarcity of, and stringent application requirements for, raw water sources increase in this country, it is becoming ever more important to critically account for every litre of water lost from a processing plant. These requirements, among others, have driven the need for development of techniques and technologies to minimise water losses from every stream exiting a coal plant. A major contributor to such water losses arises from the slimes slurry which has traditionally been stored in tailings dams. Typically, significant quantities of water are lost from these facilities due to evaporation and seepage, placing pressure on raw water make-up sources as well as polluting, rivers, dams and ground water. One solution at the forefront of this technological development drive is the incorporation of filtration technologies into the slimes slurry streams. Competent, low-moisture filter cake can then be safely and compliantly stored in dry facilities or, in the case of a filtered froth flotation concentrate, blended and sold as additional tons along with the coarse product. The filtrate water is then directly returned to the processing plant, eliminating water losses to the environment. This paper considers 3 case studies of the successful application of plate and frame filter presses.

Tailings generated during ore processing may host significant residual contents of valuable commodities, including critical metals. The particle properties of the tailings, such as mineralogy, particle size, and the surface liberation of ore minerals, strongly control processing behaviour. This study explores a novel combination of methods for incorporating particle data, derived from automated mineralogy, into geometallurgical models of tailings deposits to better understand their reprocessing potential and the economic feasibility of re-mining. This was achieved through binning of different particle types, geostatistical modelling of particle bin frequencies, and bootstrap resampling to reconstruct particle populations. The spatial distributions of processing-relevant particle properties throughout the tailings deposit were predicted with corresponding uncertainties. There are clear systematic trends in the spatial distributions of different particle types, resulting from the sedimentary-style deposition of the tailings. For instance, the tailings nearer the dam walls comprise coarser, silicate-rich particles, while fine-grained and well-liberated sulphide mineral particles are more abundant in the centre of the tailings deposit. As a result, robust models could be developed for the spatial distributions of particle size and mineralogy, which strongly control the sorting of particles during deposition, and other related properties, such as sulphide mineral grain sizes. Finally, a bulk sulphide flotation process was simulated and acid mine drainage potential estimated using the interpolated particle data. Around 58% of the sulphide minerals present could be recoverable by flotation, with the recoverable sulphide portion decreasing towards the centre of the TSF due to the fine-grained nature of the sulphide minerals. The acid mine drainage potential of the tailings is estimated to be moderate to high, indicating that the carbonate minerals present are not sufficient to neutralise the high acid-generating potential of the sulphide minerals. Overall, this study demonstrates how particle-based geometallurgical models can be developed and utilised for practical applications, with the aim of improving the accuracy of resource and reserve estimations of tailings deposits and the sustainable and responsible management of anthropogenic resources. The methodology proposed here can be easily transferred to other tailings deposits.

This paper describes and analyzes several aspects observed during the exploration of mine tailings deposits in Mexico using the CPTu_∆u, test: high ground temperatures, interstratification, chemical reaction, dissipation curves with negative pore pressure, and S-wave profile. It was observed that the use of sensors with temperature compensation for the q T and f s measurements produces satisfactory results if temperature changes are not abrupt. For the case of the dynamic pore pressure sensor u 2 , where no temperature compensation was made, the measurements are within the range mentioned in the standard except in the case when the temperature increases to values of 50°C or higher. The presence of high interstratification between thin layers of hard and soft soils, with different degrees of saturation, leads to errors in the measurement of the tip resistance and can produce deviations from the verticality of the cone, making it necessary to carry out corrections. The different types of dissipation curves observed in the tailings dams studied, where the soils are partially saturated, are generally the same as those described by Sully et al. (1999), with the particularity that in some cases, the equilibrium pressure reaches negative values. Finally, the S-wave profile obtained with correlations reproduces the general trend of the measured S-wave profile. Nevertheless, it was not possible to capture the variations in this type of deposit. In the case history described in this paper, the maximum values were not reproduced. Therefore, in this type of deposit, it is advisable the direct measurement of the shear wave and to use the smaller intervals of measurement according to the technique used.