Tailings Storage Facility Research Articles

MONITORING IS ONE OF THE MAIN SAFETY FACTORS OF TAILINGS STORAGE FACILITIES

Tailings or tails are a common byproduct of metal and mineral extraction. Typically, from ore-dressing and processing enterprises, tailings are pumped into tailings storage facilities (TSFs) which are constructed using earth-filled dams. Under improper management, tailings can have a systematic adverse impact on the environment, human health, and safety. Besides, sewage pollution and dust emissions can be potentially toxic to humans, animals, or plants. One of the key challenges currently faced by the mining sector is the industry-wide initiative to implement the most effective and efficient methods for monitoring tailings storage facilities. In the event of the physical destruction of a tailings storage facility, there can arise acute and potentially very dangerous consequences. In such cases, liquid materials of TSF can inundate the environment causing significant impact and even loss of life. Managing tailings storage facilities during and after the completion of field development is a long-term responsibility of mining companies, and it is regulated by various normative systems. TSF management should be effective throughout the entire operational lifespan, from the initial feasibility assessment of the project to the closure and post-closure. Managing critical control means is one of the main tasks facing the mining and metallurgical industry, aiming to minimize the number of fatal cases and large-scale disasters. Therefore, the rational utilization of tailings storage facilities is an integral part of corporate operational and risk management strategies. Managing critical control means is defined as an approach to managing low-probability, large-scale destructive events such as catastrophic accidents at tailings storage facilities. Achieving this goal requires technological efforts to utilize the most reliable methods for monitoring tailings storage facilities. Keywords: tails, tailings storage facilities, monitoring.

Application of Dynamic Time Warping to Determine the Shear Wave Velocity from the Down-Hole Test

A tailing storage facility (TSF) is a complex hydrotechnical structure that requires continuous monitoring to prevent catastrophic dam damage. One critical issue to control is the soil’s characteristics, which is why many field and laboratory tests are carried out on the dam to determine the relevant soil parameters. Among these tests, down-hole seismic tests, such as SCPT, are performed to determine, e.g., the shear wave velocity. However, accurately calculating the difference in the times of the arrival of the wave at the two geophones is crucial to determining its value. This article proposes a novel method for estimating this variable using the DTW (Dynamic Time Warping) algorithm, which calculates the shift between two signals by determining their optimal match. The article also addresses signal interference and proposes methods for clearing it to obtain more accurate results. Furthermore, the article introduces a method for measuring the signals’ quality based on their similarity, which helps assess whether determining the shear wave velocity is possible for a given sample.

A study on the desulfurization of sulfidic mine tailings for the production of a sulfur-poor residue

The mining industry generates large amounts of tailings every year. The most common destination for the tailings is deposition in tailings storage facilities (TSFs), which can have enormous dimensions. The management and storage of such large volumes of material pose many challenges in terms of dam stability and immobilization of hazardous contaminants that represent human-health and environmental risks, particularly for sulfide-containing materials. In addition, considerable amounts of precious and base metals can be lost in the tailings. Due to the economic value and growing industrial demand for precious and base metals, tailings may therefore be potential sources of secondary raw materials. This contribution investigates the flotation of pyrite-rich tailings, containing residual chalcopyrite, galena, and sphalerite, and high amounts of ultrafine particles. Flotation was used to recover the sulfide minerals and generate tailings with low sulfur content. The Cu-Pb-Zn-rich product could go to further treatment (e.g. (bio)hydrometallurgy) to recover the metals, while the low sulfur fraction could be used in the civil construction industry. Automated mineralogy (MLA) was used to provide quantitative mineralogical and textural data. Bench-scale experiments were performed by combining classic flotation and floc flotation (flotation of flocs of targeted minerals). Flotation of the material as received, as well as after classification into two fractions was performed. The samples as received and the coarser fraction (+37 µm) underwent classic flotation, while the finer fraction (−37 µm) was processed either by using the classic or the floc flotation approach. The flotation of the coarser particles provided higher sulfide recoveries, higher combined Cu-Pb-Zn grades in the concentrate (3.66%), cleaner residues (1.6% S), faster flotation rates, and reduced reagent consumption. Likewise, the results from the fine particle flotation allowed lower S content in the residues (3.4% S) as compared to the flotation of the original material. The results of the use of floc flotation for the finer fraction show an increase in the mass pull with a slight increase in the recovery of sulfides. Overall, the development of a route to process the tailings proved to be promising and the use of a two-route approach indicates advantages as compared to a single route.

Instrumented column testing on long-term consolidation and desiccation behaviour of coal tailings under natural weather conditions

AbstractThe sedimentation, consolidation and desiccation behaviour of sub-aerially deposited tailings in tailings storage facilities, despite occurring simultaneously and being essential to maximise tailings dry density and dewatering efficiency, are usually analysed in laboratories using distinctive testing equipment, which is unable to reveal their interactions. A large instrumented column was constructed to test the three processes of tailings in a single apparatus, capable of monitoring the changes in the hydrological parameters of coal tailings with depth and surface settlement under natural weather conditions. The column was initially filled with coal tailings slurry and exposed to natural weather for two years, during which five wetting–drying periods were identified. The monitored results indicate that exposing the slurry tailings for one month would lead to the formation of an unsaturated tailings layer with a thickness of 150 mm, likely representing the optimised tailings deposition cycle and thickness, respectively, under the given tailings characteristics and semi-arid climates. Settlement mainly occurred after major rainfall events due to the collapse of cracks and cavities formed during the preceding desiccation. The maximum thickness of the unsaturated tailings increased over the first four periods as the predominant desiccation and settlement strengthened the evaporative capillary forces, despite it decreasing greatly in the last period due to insufficient desiccation. An empirical model was proposed to consecutively estimate the surface moisture content of deformable tailings and validated by achieving a good agreement in the water mass estimated by two methods during wetting–drying cycles.

A predictive assessment of the uranium ore tailings impact on surface water contamination: Case study of the city of Kamianske, Ukraine

In this study, we present an assessment of the uranium ore tailings impact on groundwater and surface water contamination. The radioactive materials were deposited in the tailings storage facility “Dniprovske” (the city of Kamianske, Ukraine) from 1954 to 1968; now it contains about 5.85·106 m3 of hazardous waste on the area of about 76 ha in the floodplain of the Dnipro river. The lack of a proper waterproof screen below deposited tailings and in the earthen dam led to permanent watering of radioactive materials, their leaching and migration in groundwater into the nearest small Konoplianka river. We used the reports on previous site-specific studies conducted in 1999–2016, monitoring results, and the field studies conducted in 2022 with the authors’ team participation. The calculations performed with the advection-dispersion model to simulate transport of radionuclides 238U, 230Th, 226Ra and 210Pb through the embankment to the Konoplianka river and dilution relations were compared to the monitoring data of the surface water quality. Among four radionuclides, uranium poses the greatest risks today; the subsurface runoff increases its concentration in the Konoplianka river water by several times over the background value. It is estimated that due to much more intensive sorption in the shallow aquifer, the contribution of 226Ra and 210Pb to the increase in radioactivity of Konoplianka river water is insignificant compared to uranium, whereas the migration front of 230Th has probably not yet reached the riverbank. In the next 50 years the radionuclide fluxes will increase by 1.3–3.7 times for different isotopes, with the uranium subsurface runoff growing at a slower rate than nowadays. These results are of high significance for improving hydrological, hydrogeological, and geotechnical monitoring on this hazardous facility to maintain its radiation safety.

Gravity separation of fine itabirite iron ore using the Reflux Classifier – Part I – Investigation of continuous steady state separations across a wide range of parameters

High grade iron ore resources are becoming depleted in Brazil, with relatively low-grade ores requiring more intensive concentration to achieve a premium product. Accordingly, a typical industrial itabirite concentration circuit includes desliming in hydrocyclones and concentration via reverse flotation, product thickening and filtration, with the slimes sent to tailings thickeners, and onto tailings storage facilities. This work examined the potential for applying a vastly simpler approach, a single stage of gravity separation using the Reflux Classifier. Here the classified feed, 90 % finer than 0.150 mm, is sent directly to the Reflux Classifier, leading immediately to a high-grade concentrate at high solids concentration.Part I describes the findings from a comprehensive series of experiments covering the effects of bed density set point, feed pulp density, throughput, fluidisation water rate and lamella channel spacing. The main program, based on an ore with 8 % goethite and 45 % hematite, achieved a feed upgrade from 37 % to 65.6+/−0.4 % iron and iron recovery of 72.9+/−0.4 % at 9 t/m2/h. A second feed with 1 % goethite and 57 % hematite was upgraded from 41 % to 66.3+/−0.4 % iron at an iron recovery of 84.7+/−0.5 % at 10 t/m2/h. (The grade of pure hematite is 69.9 % iron). It was essential to run the Reflux Classifier at a sufficient volumetric rate to achieve shear induced inertial lift of the coarse silica within the closely spaced inclined channels, to reject the gangue minerals from the high-grade product. The results demonstrate the technical feasibility of applying the Reflux Classifier to upgrade itabirite feeds.

Environmental and operational safety of tailing storage facilities: analysis of accidents, causes and technical state diagnostic methods

A number of high-profile industrial accidents occurred at sludge and tailings storage facilities in different countries of the world are considered. The problem of ecological and technogenic danger of operating such objects, which leads to significant casualties among the civilian population, serious economic losses and harms the surrounding natural environment, is illustrated. The main causes of emergency situations have been established and analysed, it will help to reduce the risk of accidents and to minimize negative environmental consequences for similar facilities in Ukraine. The retrospective review covers the period from 1960 to 2022. During this time, about 150 cases of soil dams’ destruction in waste storage facilities were recorded. The different tendency in the frequency of accidents is noted. In particular, during the period from 1960 to 2009, there were 98 accidents with an average frequency of nearly two (1.98) per year. Over the last decade (2010-2020), the number of accidents reached 36 cases, and their frequency almost doubled to 3.6 accidents per year. Over the past two years, from the beginning of 2021 to December 2022, 10 accidents have already been registered. The vast majority of accidents during this period occurred in 34 countries of the world. The largest number of them was noted in the USA (22.4%), China (10.4%), Brazil (7.5%), Chile (6.7%), the Philippines (6.0%), Canada (5.2 %), Great Britain (4.5%) and other countries. Studies note jumps in the increase of accidents that have ten-year trends (1975, 1985, 1995, 2005). The general tendency of mass accidents since the beginning of 2015 is shown, which is substantiated by the expired terms of operation of many mining and ore enterprises (mines) and significant (exceeding normative) terms of operation of tailings storage facilities, which in some places were left without proper supervision and care. It was established that a violation of the dam slope stability (37%), an overflow of the designed capacity of the tailings storage facility (12%), seismic activity (11%), etc., are the main causes of accidents. A review of modern approaches to the management of dangerous anthropogenic objects and methods of diagnosing the technical condition of such structures was conducted. The use of a complex of organizational and technical solutions about the implementing the modern methods of assessment and control the technical condition of waste storage facilities at various levels of their operation and stages of the life cycle is proposed.

Design criteria for upstream raised tailings storage facilities

For more than 100 years upstreaming has been the dominant raising method for tailings storage facilities in Southern Africa. However, there is a growing view worldwide that upstreaming is inherently less safe than centreline or downstream raising of tailings storage facilities. Considering that more than 90% of the 250 plus operational tailings storing facilities in Southern Africa are upstream raised and cannot economically be converted to, or replaced by, downstream raised facilities, the arguments for and against upstreaming were examined in this study. It was found that no compelling reason exists to ban upstreaming in Southern Africa, provided that failure mechanisms are thoroughly considered to prevent serious design omissions. The ALARP (as low as reasonably practicable) approach is introduced as a practical method to deal with the risk of failure, and its hierarchical application is illustrated.

Predicting beach profiles for thickened tailings surface deposition

Thickened tailings deposition technology can form a stack with a certain slope by depositing high-concentration tailings slurries to reduce the footprint of tailings storage facilities and water consumption. Thickened tailings slurries exhibit complex non-Newtonian behaviors. Predicting the beach profile evolution of thickened tailings is important for the tailings storage facility design and management. A novel governing differential equation (GDE) derived from the lubrication theory is proposed in this work to capture laws of beach profile formation. Experimental data from three-dimensional laboratory-scale flume tests are analyzed using the proposed GDE. The GDE avoids the discrepancy from an inappropriate coordinate system, which exists in some state-of-the-art models and exhibits higher accuracy when predicting the beach shape near the toe of a preexisted layer. Compared with the Herschel–Bulkley (H–B) model, the Zhang’s equilibrium rheological model is preferred to determine the static yield stress, which leads to the accurate estimation of the stack profile in single- and multilayer thickened tailings depositions. The in-situ beach profile of thickened tailings is predicted using a numerical technique. A case study is included to demonstrate that the prediction based on the proposed GDE is consistent with the field measurement. The beach profile prediction of thickened tailings considering thixotropy is also discussed in this study. Results indicated that the decrease of yield stress along the flow path due to thixotropy leads to the concave beach shape of thickened tailings.

Air quality risks pertaining to tailings storage facilities within the Witwatersrand goldfields

Air quality risks pertaining to tailings storage facilities within the Witwatersrand goldfields

Experimental and numerical evaluation of the critical degree of saturation and critical exposure time of acid generating filtered tailings

Tailings filtration has many advantages (e.g., water recirculation, progressive reclamation, reduction of geotechnical risks and of environmental footprint) and is increasingly used by mining companies to improve the geotechnical stability of tailings storage facilities (TSF). However, low water content also exposes filtered tailings to oxidation thus increasing the risk for acid mine drainage (AMD) generation. Tailings management techniques must therefore be adapted to prevent contamination during operations. More specifically, tailings degree of saturation and exposure time should be controlled so they do not remain exposed too long to oxygen before reclamation work starts. The main objective of this research was therefore to evaluate the combined influence of the mineralogy and the degree of saturation on the time before filtered tailings start generating AMD. This work included (i) physical, chemical, hydrogeological and mineralogical characterization of different tailings, (ii) laboratory kinetic tests, (iii) calibration and validation of reactive transport numerical simulations, and (iv) numerical extrapolations and analysis. Results showed that AMD started when carbonates were depleted and that the critical time (i.e., the time tailings could be left exposed before AMD starts) strongly depended on the mineralogy. Maintaining the degree of saturation above 90% could contribute to delay the generation of AMD, and the greater the degree of saturation, the longer the critical time. However, the critical time became independent of the degree of saturation and depended only on the mineralogy when Sr< 90%. The results of this study tend to show that it should be possible to plan the deposition of reactive filtered tailings to limit the generation of AMD, for example by mixing reactive tailings with other tailings containing a greater neutralization potential and/or by regularly disposing of a new layer of tailings on the surface, with the maximum delay between two layers being shorter than the critical time.

Legal regulation of ecological rehabilitation of radioactively contaminated territories in Ukraine: problems and ways to solve them

Purpose. The purpose of the research is to identify the shortcomings of the current legislation of Ukraine in the field of ecological rehabilitation of radioactively contaminated territories, as well as to provide proposals for possible ways to overcome them. Methodology. The methodology includes a comprehensive analysis and generalization of the available scientific and theoretical material and the formulation of relevant conclusions and proposals. During the writing of the article, both general scientific methods of scientific knowledge and special-legal ones were used, including formal-legal, structural-functional, systemic and other methods. Results: in the process of research, it was established that the current legislation of Ukraine in the field of ecological rehabilitation of radioactively contaminated territories contains norms of a local nature, which determine the legal regime of the territories affected by the disaster at the Chernobyl nuclear power plant. At the same time, radioactively contaminated territories in Ukraine are the territories of former uranium mining and processing plants, tailings storage facilities (Dnipropetrovsk and Kirovohrad regions). Based on this, the expediency of supplementing the Law of Ukraine "On the Use of Nuclear Energy and Radiation Safety" with the section "Radioactively Contaminated Territories" was determined, the effect of which would extend to the entire territory of Ukraine. In addition, the article proposes to give the land plots on which uranium production waste storage sites, buildings and structures contaminated with natural radioactive substances, which due to their ecological danger cannot be used in economic activities, the legal status of those that are not subject to taxation, as well as to establish additional subsidies from the State Budget of Ukraine for the relevant local budgets in order to compensate for the loss of revenues of local budgets as a result of the exemption from taxation of land plots that are radioactively contaminated. Originality. The scientific novelty of the research lies in the possibility of using the obtained results for further scientific developments in the field of legal regulation of ecological rehabilitation of radioactively contaminated territories. Practical significance. The results of the research can be used in law-making activities with the aim of improving the provisions of the current legislation of Ukraine in the field of ecological rehabilitation of radioactively contaminated territories.

Monitoring and modelling the deformation state of a dyke of a flotation tailings reservoir of a copper ore mine

The mining areas of the copper ore mines in Poland contain tailings storage facilities. Because of operational safety issues and to minimize the exposure of local neighbourhoods to the risk of such reservoirs failing, mining operations are limited during the period of waste storage, thereby reducing the impact of exploitation on these objects. Nevertheless, continuous monitoring and analysis of the deformation state of reservoirs and associated facilities are required. Monitoring is most often carried out using geodetic methods, while the deformation analysis is based on determining the displacements of control points and making short- and long-term forecasts of changes in land surface deformation. Presented here is an analysis of changes in the state of displacements and dyke deformations of a currently closed copper flotation tailings reservoir that was used in the 1970s. After the storage of waste was stopped, an intensive two-stage mining operation was carried out under the reservoir. The results obtained from the geodetic monitoring of displacements and deformations of the reservoir dyke are compared with the model values, and the usefulness of the applied theoretical model for describing the vertical and horizontal displacements and horizontal deformations is verified. Based on the comparison results, a hypothesis is presented regarding the causes of the actual condition of the movements of the reservoir dam crest against the background of the expected movements obtained from theoretical modelling. The presented conclusions revise a very rigorous approach to protecting flotation tailings reservoirs against the effects of underground mining.

Investigation of Properties of Domestic Binders for Dust Suppression at Tailings Storage Facilities

Investigation of Properties of Domestic Binders for Dust Suppression at Tailings Storage Facilities

Improvement of operation of tailings storage facilities at mining and processing plants

Purpose. To study the schemes of transportation of iron ore enrichment tailings for their storage in the mined-out space of the spent mines in conditions of increased production of iron ore concentrate. The methods. The results of the study were obtained by means of a feasibility study for the comparison of five different schemes of transportation of enrichment tailings: rail transport, belt conveyor, rope-belt conveyor, tubular conveyor, pipeline. A comparative assessment of capital costs, annual operating costs and the number of employees of the process of transportation and storage of enrichment tailings in the mined-out space of the spent mine was carried out. Findings. The issue of transportation of iron ore enrichment tailings in conditions of open development of mineral deposits is considered. Different types of transport were considered from the point of view of delivery and storage of enrichment tailings. It has been established that the most effective modes of transport, from the point of view of cost reduction and environmental protection, are a tubular conveyor for transporting dry mass and a pipeline for pulp. It has been established that in some cases –provided there is a corresponding technological necessity –it is advisable to use the lower branch of the tubular conveyor for transportation. The originality. The dependence of capital and annual operating costs for the transportation and storage of enrichment tailings in the spent pit on the considered options for transportation by rail transport, belt conveyor, rope-belt conveyor, tubular conveyor, and pipeline was established. The dependence of the change in the number of workers involved in the process of transportation and storage of enrichment tailings on the scheme of their transportation has been established. Practical implementation. Reasonable conditions for the use of a tubular conveyor for the transportation of enrichment tailings to the produced space of the spent pit and to the beneficiation factory are substantiated. In schemes that provide for the reprocessing of enrichment tails, both branches of the tubular conveyor can be used as transport: the lower and the upper.

Reply to the discussion by Reid et al. on “Mechanism of failure of the Mount Polley Tailings Storage Facility”

Reply to the discussion by Reid et al. on “Mechanism of failure of the Mount Polley Tailings Storage Facility”

Discussion of “Mechanism of failure of the Mount Polley Tailings Storage Facility”

Discussion of “Mechanism of failure of the Mount Polley Tailings Storage Facility”

Socio-Environmental Risks Linked with Mine Tailings Chemical Composition: Promoting Responsible and Safe Mine Tailings Management Considering Copper and Gold Mining Experiences from Chile and Peru.

There is a need to define mine tailings in a clear, precise, multidisciplinary, transdisciplinary, and holistic manner, considering not only geotechnical and hydraulic concepts but also integrating environmental and geochemical aspects with implications for the sustainability of mining. This article corresponds to an independent study that answers questions concerning the definition of mine tailings and the socio-environmental risks linked with mine tailings chemical composition by examining the practical experience of industrial-scale copper and gold mining projects in Chile and Peru. Definitions of concepts and analysis of key aspects in the responsible management of mine tailings, such as characterization of metallic-metalloid components, non-metallic components, metallurgical reagents, and risk identification, among others, are presented. Implications of potential environmental impacts from the generation of acid rock drainage (ARD) in mine tailings are discussed. Finally, the article concludes that mine tailings are potentially toxic to both communities and the environment, and cannot be considered as inert and innocuous materials; thus, mine tailings require safe, controlled, and responsible management with the application of the most high management standards, use of the best available technologies (BATs), use of best applicable practices (BAPs), and implementation of the best environmental practices (BEPs) to avoid risk and potential socio-environmental impact due to accidents or failure of tailings storage facilities (TSFs).

Remediation of grassland subsidence and reduction of land occupation with tailings backfill technology: a case study of lead-zinc mine in Inner Mongolia, China

The mining industry provides essential mineral resources for human society’s development. However, this industry generates a large quantity of waste material while rapidly extracting valuable elements from ore, such as processed tailings. The existence of mined voids will cause surface subsidence, and the surface stockpiling of tailings and waste rocks occupy a large amount of land and the risk of Tailings Storage Facility (TSF) failure. This paper proposes tailings backfill technology to mitigate surface subsidence and provides an alternative disposal method for tailings generated during ore extraction. Tailings backfill technology prepares the slurry by adding a certain amount of cementitious material into the tailings and transporting it to the underground goaf through a pipeline. The backfill slurry could then gradually build up its strength during the hydration of. Cementitious material. A case study of a lead-zinc mine in the Inner Mongolia Autonomous Region of China using tailings backfill technology was introduced in detail to solve the problems of grassland collapse caused by mine excavation and environmental damage due to tailings disposal. Spread test and rheological test were carried out to study the flow characteristics of filling slurry and the uniaxial compressive strength (UCS) of backfill was tested as well. The result illustrates that the spread of the filling slurry with a solid content between 72% and 76% and cement-tailings ratio between 1:4 and 1:8 is greater than 14 cm, and the UCS of backfill is above 1 MPa. The research shows that the tailings backfill technology recycles tailings waste while mitigating surface grassland subsidence and land occupation of waste disposal. Tailings backfill technology can significantly reduce tailings discharge or even achieve no discharge. A leaching test for heavy metal element classification of the backfill sample was carried out. The results show that the heavy metal detection indicators meet the environmental protection standard requirements and will not cause secondary environmental pollution. Therefore, tailings backfill technology can realize green and efficient management of mine waste and has great application and promotion prospects.

Clarification of tailings storage facility water by acoustic impact methods

Clarification of tailings storage facility water by acoustic impact methods