Tailings Storage Research Articles

Microstructure and mechanical behavior of cemented gold/tungsten mine tailings-crushed rock backfill: Effects of rock gradation and content

Without appropriate and responsible waste management in place, the cursory storage of tailings and waste rocks on the surface can cause devastating damage to the planet's ecosystems. To proactively manage or abolish the damage, some techniques such as mine backfill have been already used repeatedly in mines. Microstructure and strength behavior of cementitious tailings-crushed rock backfill (CTCRB) with gold/tungsten tailings and rock contents (e.g., 10%, 20%, 30%, 40%, and 50%) were conducted in this study by using both UCS (unconfined compressive strength) tests (e.g., peak strengths, stress-strain curves, failure modes) and SEM micro-graphs. Key conclusions were shown that: when gradation and content of crushed rock was considered as 1–3 mm and 50% respectively, the UCS value of gold tailings based backfills was 1.02 MPa. In contrast, the UCS value of tungsten mine tailings based backfills was 1.36 MPa when the amount of crushed rock within the filling matrix became 10%. Tungsten tailings based backfills were more sensitive to crushed rock gradation than gold tailings based backfills. CTCRB's stress-strain curvatures were up-concave in the step of pore compaction. With the increase in the content and gradation of crushed rock, tungsten tailings based backfills showed swelling and crushing in complete destruction. Tailings' particle size, crushed rock content and gradation utterly affected the failure modes of CTCRB. Ettringite/CSH gel was found to be the leading hydration materials in the backfill matrix. The micro-cracks within CTCRB specimens were unfavorably correlated with its UCS data. To conclude, this study's main outcomes could give a significant guide for CTCRB's industrial uses.

In-Pit Disposal of Mine Tailings for a Sustainable Mine Closure: A Responsible Alternative to Develop Long-Term Green Mining Solutions

In the next decades many of the old tailings storage facilities (TSFs) could be re-processed if one considers the prices of metals, new uses of metals which today are not valuable, and the application of new, more efficient metallurgical technologies. In this context, in-pit disposal of mine tailings (IPDMT) is an attractive alternative to be used as part of responsible mine closure: mines could reprocess the mine tailings and place them in an open pit as part of sustainable mine closure. This article explores a little-explored tailings disposal technique that has the potential to be considered as an environmentally friendly solution, returning mine tailings to their place of origin and providing long-term stability under a climate change scenario. This article presents the main features, benefits, and potential drawbacks of IPDMT, with an emphasis on: (i) a description of the main advantages and disadvantages of application; and design issues related to (ii) IPDMT physical stability (pit slope stability, tailings transport, placement systems); (iii) IPDMT hydrological stability (water management, seepage control, hydrogeological monitoring,); and (iv) IPDMT geochemical stability (geochemical characterization, acid rock drainage control, covers). The novelty of this article is the proposal to change the status quo of traditional management of mine tailings to a new paradigm where the technique of in-pit disposal of mine tailings can be considered a green mining solution for mine closure. Finally, some successful cases around the world that involved the implementation of this technique are presented.

Blending bauxite residues with multiple byproducts improves capping materials for tailings storage facilities

Amelioration and management of large volumes of tailings resulting from alumina refining is a major challenge owing to the high alkalinity and salinity of residues. Blended byproduct caps are a potential new and more cost-effective approach to tailings management, where tailings are blended with other local byproducts in order to reduce pH, salinity and toxic elements. Here, alkaline bauxite residue was blended with four byproducts (waste acid, sewage water, fly ash and eucalypt mulch) to create a range of potential capping materials. We leached and weathered materials in the glasshouse with deionized water over nine weeks to investigate if byproducts on their own or in combination improved cap conditions. Combining all four byproducts (10 wt % waste acid, 5 wt % sewage water, 20 wt % fly ash and 10 wt % eucalypt mulch) achieved lower pH (9.60) compared to any byproduct applied individually, or un-remediated bauxite residue (pH 10.7). Leaching decreased EC by dissolving and exporting salts and minerals from the bauxite residue. Fly ash addition increased organic carbon (likely from non-combusted organic material) and nitrogen, while eucalypt mulch increased inorganic phosphorus. Addition of byproducts also decreased the concentration of potentially toxic elements (e.g., Al, Na, Mo and V) and enhanced pH neutralisation. Initial pH with single byproduct treatments was 10.4–10.5, which decreased to between 9.9–10.0. Further lowering of pH and salinity as well as increased nutrient concentrations may be possible through higher addition rates of byproducts, incorporation of other materials such as gypsum, and increasing leaching/weathering time of tailings in situ.

Optical remote sensing of large-scale water pollution in Angola and DR Congo caused by the Catoca mine tailings spill

Billions of tons of hazardous mine waste are stored in thousands of tailings storage facilities around the world. These impoundments represent one of the most important environmental risk factors of industrial mining, since occasional tailings spills or dam failures cause devastating impacts on humans and ecosystems, specifically along river corridors. In this study, we developed a satellite remote sensing methodology to assess the impacts of tailings spills on water quality focusing on the controversial incident that occurred at the Catoca diamond mine in Angola in late July 2021. The spill allegedly caused important river pollution in neighbouring Democratic Republic of the Congo (DR Congo) and led to public health concerns including the loss of human lives – however the mining company denied any responsibility. We processed high resolution imagery acquired by ESA’s Sentinel-2 satellites using the Python package Acolite for atmospheric correction and turbidity retrieval, and applied a river skeletonizing algorithm to automatically extract turbidity values for the entire river system. This allowed tracking the propagation of the pollution front from the source at the Catoca mine through the Tshikapa- and the Kasaï River during more than one month and across 1400 km, until the pollution front finally dissipated after discharging into the Congo River. We further analyzed a 6-year time series of virtual stations in the Tshikapa River located up- and downstream of the effluent discharge to compare the impacts of the tailings spill to seasonal variabilities of water quality. Turbidity values caused by the spill largely exceeded the seasonal variability in the Tshikapa River in recent years. These findings confirm that the Catoca tailings spill has significantly affected water quality of the Tshikapa- and the Kasaï River with total suspended solids concentrations that were several 10-fold above drinking water standards in Lunda Norte Province, Angola, and Kasaï Province, DR Congo, making severe public health impacts for residents and fish kills highly probable. After investigating whether this methodology could be applied to other tailings dam failures that have occurred since the Sentinel-2 mission began in 2015, we recommend to apply it to four other incidents in Mexico, Myanmar, Peru and China, respectively. Overall, this Sentinel-2 workflow provides the opportunity to assess the large-scale impacts of pollution incidents in mining areas around the world in locations where hydrological- and water quality data are scarce and monitoring capacities are limited.

Numerical analysis of aerodynamic regime near tailings storage facility

Tailings formed during the mining and beneficiation of iron ore are sources of intensive dust generation. In order to assess the intensity of dust formation and determine the effectiveness of methods of its reduction, it is necessary to know the local velocity of the air flow near the various surfaces of the tailings storage facility. For the theoretical solution of this problem, a CFD model was developed, which allows determining the velocity field of the air flow when flowing around the tailings storage facility. The model allows you to obtain the value of the wind speed near the surfaces of the structure and, based on this information, to make a forecast of possible dust formation. The constructed CFD model is based on the use of an aerodynamic model of potential motion. The modeling equation is the Laplace equation for the velocity potential. To build a numerical model, the idea of establishing a solution in time is used, therefore numerical integration of the “unsteady equation” for the velocity potential is carried out. Numerical integration is carried out using the finite-difference method of total approximation. The results of the computational experiment are presented.

Assessment of the impact of waste of mining and chemical enterprises on surface water quality

The mining and chemical industry causes pollution of the soil and water environment both during its operation and after its termination. The waste of large industrial complexes poses a particular danger to the aquatic environment. Tailings storage facilities located in the Dniester River basin are characterized by a low level of environmental safety of these facilities, which indicates unsatisfactory management and their neglected state. Violation of the rules for the operation of tailings can lead to industrial accidents on a transboundary scale with uncontrolled emissions of pollutants and devastating consequences for the environment.The purpose of the study is to assess the impact of waste from State Enterprise “Rozdil mining and chemical enterprise “Sirka”” on the quality of the largest water bodies in the area of influence of this enterprise – lakes Serednie, Hlyboke and Kysle, located near industrial waste storage areas, and the mine channel through which water flows into the transboundary river Dniester.The work experimentally determined and analyzed the indicators of water samples taken in 2021–2022 from the largest reservoirs in the zone of influence of SE “Rozdil MCE “Sirka”” – lakes Serednie, Hlyboke and Kysle, located near industrial waste storage sites and the water from which flows into the transboundary Dniester River along the mining channel (channel of Lake Hlyboke-Dniester River).In the analyzed water samples of the Hlyboke, Seredne, Kysle lakes and the mine channel, an excess of the MPC for sulfates is observed by 1.5–6 times, and the mineralization index by 2.3–3 times. There is a tendency to decrease the content of ammonium nitrogen in the studied reservoirs. In 2017 and in 2021–2022, there was a deviation from the water pH standards in Lake Kysle, as well as exceeding the MPC for phosphates, sulfates, ammonium nitrogen, and mineralization. In the mine channel, the maximum limit was found to be exceeded according to the following indicators: pH, sulfates, ammonium nitrogen.It is expedient to consider the issue of environmental safety of tailings at both the international and national levels. It is extremely important to improve the policy of prevention and liquidation of the consequences of accidents, interaction between civil protection management bodies and enterprises.

Environmental Impacts of Gold Mining—With Special Reference to South Africa

Gold mining has serious negative environmental impacts, especially due to pollution emanating from tailings storage facilities (TSFs, tailings dams, slimes dams). The most important forms of pollution from TSFs are acid mine drainage (AMD) and high levels of potentially toxic elements (PTEs). AMD arises from the high levels of pyrite in the mining ores, which become oxidised in the TSFs where the pyrite is exposed to atmospheric oxygen. The sulphate produced from oxidation of the sulphide in the pyrite dissolves in water to form sulphuric acid, a very strong acid. pH levels in the extremely low range of 3–4 are common. At such low pH the mobilities of numerous metallic PTEs present in gold mine tailings become extremely high, causing them to move into the environment in AMD. AMD acidifies soils to very low pH levels at which the mobility and plant-availability of metallic PTEs are very high, causing toxicities. Very disconcerting is that AMD and PTE pollution is in some cases continueing unabated at high rates even more than 70 years after a mine has been abandoned. Rehabilitation of TSFs to contain AMD and PTEs within them is very expensive and there seems to be reluctance to fully commit to their rehabilitation. Rehabilitation of TSFs is also extremely difficult. There does not yet seem to be any guidelines for their effective rehabilitation.

Modelling unsaturated silty tailings and the conditions required for static liquefaction

The potential for static liquefaction of tailings is a major focus in the design and operation of tailings storage facilities. This research models the behaviour of unsaturated tailings, with a variety of degrees of saturation, addressing the propensity for static liquefaction during monotonic loading. Unsaturated triaxial tests, including constant suction conditions and constant water–air mass conditions, were performed. A bounding surface plasticity model was used to simulate the results. The constant mass condition is relevant to undrained closed-system loading, which may prevail during fast deformation after the tailings becomes unstable, when the air and water in the pore space remain locked inside the tailings. Boyle's law and hydraulic hysteresis were accounted for to model the changes of pore air and water pressures, and suction, with the change in tailings volume. Good agreement was achieved between test results and model simulations. Additional simulations to mimic rising water tables under constant total stress states in the field, situations that may trigger instabilities, are also shown. Results are added to charts which relate peak and post-liquefaction strengths, as well as collapse lines, to measures of initial state, for unsaturated conditions, which may be of use in practice.

Spatial and Temporal Study of Supernatant Process Water Pond in Tailings Storage Facilities: Use of Remote Sensing Techniques for Preventing Mine Tailings Dam Failures

Considering the global impact on society due to tailings storage facilities (TSFs) accidents, this article describes a study to monitor mine tailings management and prevent mining tailings dam failures, considering the analysis of different TSFs real cases. The spatial and temporal dynamic behavior of the supernatant process water pond of the TSFs is studied as a critical issue, using remote sensing techniques based on multispectral satellite imagery. To understand the current state of the art, a brief description of engineering studies for the control and management of the supernatant process water pond in TSFs is presented. This research considers the main method of the study of practical cases with the use of techniques of multispectral interpretation of satellite images from the Sentinel 2 remote sensor. In addition, the management of tools such as Geographical Information System (GIS) and Google Earth Engine (GEE) is implemented, as well as the application of some spectral indices such as NDWI and the joint use of (i) NDVI, (ii) mNDWI, and (iii) EVI. Real TSF cases are analyzed, including the dam failures of Jagersfontain TSF in South Africa and Williamson TSF in Tanzania. Finally, this article concludes that the size, location, and temporal variability of the supernatant process water pond within a TSF has a direct impact on safety and the possible potential risk of the physical instability of tailings dams.

A Comprehensive Review of Large Strain Consolidation Testing for Application in Oil Sands Mine Tailings

Oil sand tailings are a mixture of sand, fines, water, and a residual amount of un-extracted bitumen in varying proportions. Tailings management is highly dependent on the consolidation behavior of the tailings. Although a great deal of work on this sector has been performed to study the consolidation behavior of oil sands tailings, it continues to play a critical role in quantifying the long-term geotechnical stability of tailings storage facilities. A review of large strain consolidation testing that exists, whether in the industry or in academia, has been compiled and presented in this manuscript to illustrate the advantages and drawbacks of measuring consolidation behavior of tailings using these tests. For oil sands mine tailings, it has been concluded that the conventional oedometer consolidation test can result in significant errors in quantifying the consolidation behavior. Conversely, testing procedures such as multi-step loading large strain consolidation tests, large slurry consolidometer tests, centrifuge testing, and seepage induced consolidation tests are widely employed to quantify the consolidation behavior of oil sands tailings.

Information Supply of Hydrotechnical Reconstruction Concept of Stebnyk Tailings Storage (Ukraine)

Information Supply of Hydrotechnical Reconstruction Concept of Stebnyk Tailings Storage (Ukraine)

Automated control of earthfill dams at tailings storage facilities

Automated control of earthfill dams at tailings storage facilities

Current condition and potential expansion of tailings storage facilities at an Arctic monotown: A case-study of Karelskiy Okatysh

Current condition and potential expansion of tailings storage facilities at an Arctic monotown: A case-study of Karelskiy Okatysh

Bio-Assisted Improvement of Shear Strength and Compressibility of Gold Tailings

Safe storage of mine tailings has challenged engineers as shown by numerous historical tailings dam failures. While the storing of tailings behind tailings dams is the most practical containment solution, poor mechanical characteristics (low strength and high compressibility) of these waste materials raises serious concerns regarding the stability of tailings dams. In this study, the microbially-induced calcite precipitation (MICP) technique is used to treat gold tailings. Accordingly, tailings were enriched with Sporosarcina pasteurii and flushed with different concentrations of cementation solution to find the CaCl2 amount that produces the highest shear strength in studied tailings. Their shear strength and compressibility were measured in direct shear and one-dimensional oedometer tests and compared with those of the untreated tailings. Results showed that the 50 mM CaCl2 cementation solution proved the most effective treatment solution with respect to MICP, reducing compressibility of tailings by about 300% when loaded up to 800 kPa and improving shear strength by 140%. X-Ray Diffraction (XRD) analysis and Scanning Electron Microscope (SEM) images of treated samples further illustrated the effects of MICP on the composition and structure of the tailings specimens.

3D geostatistical modelling of a tailings storage facility: Resource potential and environmental implications

The management of mine tailings presents a global challenge. Re-mining of tailings to recover remaining metals and other valuable constituents could play a crucial role in reducing the volume of stored tailings. To assess the resource potential of tailings storage facilities, 3D resource models must be constructed. This is not straightforward owing to the heterogeneous nature of tailings. In this case study, modelling of the Davidschacht tailings deposit was performed using universal sequential Gaussian simulation, to account for the strong trends and heterogeneity in chemical distribution. The tonnages of the valuable elements were estimated with reasonable certainty, confirming that relatively few drill holes are required for robust resource estimates of tailings storage facilities. Zinc is the most abundant valuable metal (∼5,170±517 t), followed by Pb (∼2,060±206 t), Cu (∼550±66 t) and In (∼11±1 t), while the toxic elements As and Cd are present in tonnages of ∼8,350±585 t and ∼47±4 t, respectively, with errors given for 95 % confidence levels. Despite the In tonnage being low compared to the other elements, its in situ value is around half that of Cu and Pb, demonstrating the importance of high value by-products for re-mining potential. Although tailings deposits typically have lower grades than primary ore deposits, and the quantities of recoverable valuable elements may be even lower due to current technological limitations, re-mining of TSFs may help to diversify raw materials supply chains and should also be considered for rehabilitation purposes. Geostatistical modelling, particularly universal kriging-based simulation, has been proven to produce robust tonnage estimates of tailings storage facilities and should be adopted in industry to reduce the technical and financial uncertainties associated with re-mining.

Deriving big geochemical data from high-resolution remote sensing data via machine learning: Application to a tailing storage facility in the Witwatersrand goldfields

Remote sensing data is a cheap form of surficial geoscientific data, and in terms of veracity, velocity and volume, can sometimes be considered big data. Its spatial and spectral resolution continues to improve over time, and some modern satellites, such as the Copernicus Programme's Sentinel-2 remote sensing satellites, offer a spatial resolution of 10 m across many of their spectral bands. The abundance and quality of remote sensing data combined with accumulated primary geochemical data has provided an unprecedented opportunity to inferentially invert remote sensing data into geochemical data. The ability to derive geochemical data from remote sensing data would provide a form of secondary big geochemical data, which can be used for numerous downstream activities, particularly where data timeliness, volume and velocity are important. Major benefactors of secondary geochemical data would be environmental monitoring and applications of artificial intelligence and machine learning in geochemistry, which currently entirely relies on manually derived data that is primarily guided by scientific reduction. Furthermore, it permits the usage of well-established data analysis techniques from geochemistry to remote sensing that allows useable insights to be extracted beyond those typically associated with strictly remote sensing data analysis. Currently, no generally applicable and systematic method to derive chemical elemental concentrations from large-scale remote sensing data have been documented in geosciences. In this paper, we demonstrate that fusing geostatistically-augmented geochemical and remote sensing data produces an abundance of data that enables a more generalized machine learning-based geochemical data generation. We use gold grade data from a South African tailing storage facility (TSF) and data from both the Landsat-8 and Sentinel remote sensing satellites. We show that various machine learning algorithms can be used given the abundance of training data. Consequently, we are able to produce a high resolution (10 m grid size) gold concentration map of the TSF, which demonstrates the potential of our method to be used to guide extraction planning, online resource exploration, environmental monitoring and resource estimation.

Applicability of the risk ranking methodology designed for water reservoirs to tailings storage facilities

The risks associated with operating water reservoirs and tailings storage facilities (TSFs) are different because of their different purposes, methods of construction and operation, and characteristics of the materials impounded and their flow behaviour. Regardless of the differences, these two types of structures are often put in the same category when it comes to risk assessment and the application of relevant methodologies, which may result in unrealistic outcomes. In this paper we investigate whether it is possible to apply the risk ranking methodology designed for water reservoirs to TDFs and overview the key differences between these two types of structures. We also provide a comparative analysis of the results obtained by conducting a risk assessment of the operation of a TSF, applying the method recommended by the International Commission on Large Dams (ICOLD), and analyse the results using the failure mode and effects analysis (FMEA) technique. It is concluded that a more realistic evaluation of risk levels can be obtained by adopting a systematic approach to risk assessment in accordance with the traditional risk definition on which the FMEA technique is based.

Mine tailings storage dams modify upstream headwater fish assemblages

Riverscape connectivity is a critically important component determining the ecological condition of lotic ecosystems. We evaluated changes in fish assemblages caused by the loss of connectivity by mine tailings storage dams (TSDs), hypothesizing that headwater fish assemblages are restructured by TSDs located downstream, even though the upstream habitats are not altered. We used standard methods to collect fish in 24 first to third order sites, with half draining to TSDs (dammed) and the other half free from this impact (undammed). To identify differences between treatments, we used PERMANOVA to test both environmental variables and ichthyofauna composition (Bray-Curtis similarity index) and evaluated the biological metrics that most influenced assemblage composition change. As expected, we observed no difference between treatments for environmental variables, but we did observe differences in fish assemblage composition. We also observed five metrics with lower values in dammed streams (richness and abundance of intolerant species, siluriform richness, and abundance of Pareiorhaphis cf. proskynita and Trichomycterus brasiliensis) and two metrics with higher values in dammed streams (perciform richness and abundance of Oligosarcus argenteus). We believe these changes resulted from of stream fragmentation by TSDs, in addition to source-sink mechanisms and conclude that mine TSDs located downstream change headwater fish assemblages, an impact often neglected in biomonitoring and bioassessment studies.

Process Water Management and Seepage Control in Tailings Storage Facilities: Engineered Environmental Solutions Applied in Chile and Peru

In the past thirty years many mining projects in Chile and Peru have used: (i) polymeric geomembranes and (ii) design-and-build cutoff trenches, plastic concrete slurry walls, and grout curtain systems to control seepage at tailings storage facilities (TSFs). Geosynthetics are a viable alternative at a TSF dam for clay cores or impermeable materials, mainly because of their marked advantages in cost, installation, and construction time. This article describes the use of geosynthetics liners and cutoff trench–plastic concrete slurry walls–grout curtain systems in TSF dams in Chile and Peru mining, with the objective to decrease seepage to the environment, considering different dam material cases such as: cycloned tailings sand dams, borrow dams, and mine waste rock dams. Finally, this article discusses aspects of geosynthetic technology acceptance in the local regulatory frameworks, lessons learned, and advances. It focuses on the use and implementation of geosynthetics in TSFs in Chile and Peru, which have some of the highest TSF dams in the world, as well as a wet environment, dry environment, extreme topography, and severe seismic conditions. These conditions constitute a challenge for manufacturers, engineers, and contractors, who must achieve optimal technical solutions, while being environmentally aware and economic.

Analisis neraca air pascatambang pada tailing storage facility

Tailings Storage Facility (TSF) has environmental impacts and risks arising from the tailings storage. Water balance is an important component in TSF management. In this study, the water balance was analyzed to determine the method of handling TSF during mine closure, to reduce the risk of environmental pollution. Analysis of the rainfall and potential evaporation parameters was used to calculate the water discharge that must be managed in mine closure. The method of selecting daily maximum rainfall data was used to analyze the need for TSF facilities. Meanwhile, for mine closure TSF filling, scenarios for extreme climate conditions were made for the rainfall and potential evaporation parameters which were then analyzed to determine the water balance. Based on the daily data analysis, the maximum amount of water discharge that must be managed at the TSF was 1.511 m3/s. Meanwhile, for TSF charging, it was found that the fastest charging scenario took 31.8 months and for the longest charging it took 110.4 months. To determine the method of handling TSF during mine closure, the results of water balance analysis for several scenarios of climatic conditions resulted in the minimum thickness of the water column ranging from 6 - 8 m. Based on the analysis of several scenarios of climatic conditions, the mine closure method for handling TSF was water cover.