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Tailings dams constructed using the upstream method are generally less stable, because of its operational and constructive approach; this presents increased risks, which is the reason why such structures are being closed in Brazil. A feasible option to ensure the safety of closing operations in such dams consists of extracting tailings from behind the dam (reservoir), reducing moisture content through dewatering and compacting it into stable stacks. This demands knowledge of the compacted material's response. Thus, the present research assesses the mechanical response of compacted copper ore tailings extracted from two different sampling locations within the dam reservoir (i.e. about to be de-characterised) from northern Brazil. For this, drained and undrained triaxial compression tests were carried out on compacted dewatered dense, medium and loose specimens, which were assembled using the tailings retrieved from upper and lower beaches to evaluate the influence of grading, as well as the influence of the fabric arising from the initial compaction on the critical state lines (CSLs) of these saturated non-plastic silty sand tailings. The results indicated that the critical state parameters, in the υ–ln p′ space, are dependent on the fabric arising from the initial compaction. Distinct CSLs, which are all curvilinear and parallel to each other, were found in the research. [ABSTRACT FROM AUTHOR]

This paper re-evaluates the Edenville earth dam that failed in 2020 after a rapid rise in reservoir level caused by prolonged significant rainfall. The dam instability and possibility of static liquefaction–induced flow failure are assessed in the framework of critical state soil mechanics (CSSM). Both undrained loading and drained unloading stress paths are considered for flow liquefaction assessment. Using documented triaxial compression tests, the Norsand constitutive model is calibrated for finite-element numerical models. This study supplements the analyses conducted by an independent forensic team (IFT) in charge of failure investigation. The advances achieved by tailings dam practitioners are leveraged here to study flow liquefaction as recommended by the IFT. Multiple ways are employed to generate reasonable initial field stresses. Simulation of dam construction coupled with steady-state seepage analysis creates an appropriate starting condition for further flow liquefaction assessment. The numerical outputs confirm the result of the IFT's limit equilibrium analyses for an undrained boundary condition. Stress analyses with a drained boundary condition show that a major stress change with a constant-shear-drained (CSD) stress path develops below the dam crest due to a rising reservoir level. The results of our models with a CSD stress path and drained-to-undrained transition better explain the evolution of the Edenville dam failure. The current study provides a practical approach to earth dam design and evaluation. [ABSTRACT FROM AUTHOR]

Sudden displacement of large volumes of liquid–granular mixtures in nature (dam-breaks, landslides, floods, etc.) are often reported to be deadly and destructive. The flow behavior of those mixtures is complex and depends on a large variety of parameters, e.g., size distribution of the solid phase, viscosity of the fluid, predisplacement packing conditions, ratio of solid to liquid phase, and geometry of the domain. Because of the multitude of parameters and the large displacements involved, the numerical modeling of these phenomena is complex. A two-phase double-point material point method formulation in Anura3D, a particle-based continuum numerical method, was tested against two experimental cases. Model simulations showed that simple constitutive models such as Mohr-Coulomb (MC) with perfect plasticity can be sufficient to accurately model bulk granular flow behavior. However, with slightly different initial conditions, these flows can exhibit more complex features such as progressive block failures, which necessitates a more advanced solid constitutive model such as MC strain softening. Further, other simulation parameters like wall friction boundary conditions and fluidization threshold are also crucial in these types of numerical simulations. The ability of such models to capture complex failure modes is critical to assess dam safety. The sudden release of a mixture of granular materials and water, for example, after failure of a tailings dam, can have devastating consequences on downstream infrastructure and communities. We investigated how such flows can be accurately predicted using the computer model Anura3D, which uses a special technique, where material points separately represent the water and the grains because those points can efficiently represent the large deformations that these types of granular flows exhibit. We found that, at higher water content, a simple model of the mechanical properties of the granular and water mixture suffices. However, at lower water content, the more complex behavior of the granular flow requires a specific model that takes into account the local history of deformations. This study is relevant to the analyses of dam safety, post-wild fire hillslope debris flows, and landslides. [ABSTRACT FROM AUTHOR]

The 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. [ABSTRACT FROM AUTHOR]

Upstream tailings dams are high-risk structures that have experienced several failures worldwide, particularly with iron ore tailings (IOT). In this study, new disposal methods/techniques, such as cement-stabilized dry stacking, are discussed that provide enhanced mechanical behavior while reducing failure risks. Alkali-activated materials are used as cementing agents due to their mechanical and environmental advantages compared to ordinary Portland cement. This study evaluates the mechanical and microstructural behavior of IOT stabilized with an alkali-activated cement (AAC) composed of two by-products from the IOT beneficiation process, metakaolin and sodium silicate, tested under plane strain conditions. Simple shear tests and microstructural analysis were performed. Mixtures of IOT were produced with 0%, 1%, 3%, and 5% AAC to examine the influence of such variables on strength and deformability parameters under undrained conditions. The mixtures with 3% and 5% AAC showed the greatest impact on the strength; however, the addition of 1% AAC was able to reduce positive pore-pressure generation. Cementitious bounds were evidenced by forming a sodium aluminosilicate hydrate gel. The studied AAC was effective in stabilizing IOT, even at small contents. [ABSTRACT FROM AUTHOR]

In view of many past failures of tailings storage facilities, practising engineers have been analysing current design guidelines for different elements of these facilities, including for tailings dams. In this paper, an attempt is made to investigate how varying tailings slurry solids concentration (${c_s}$ c s ) affects the stability of tailings dam embankment slope. To achieve this, elaborate two-dimensional limit equilibrium and finite element simulations were conducted and a steady-state seepage analysis was performed so as to obtain accurate free surface water flux through the slope. Initially, numerical analyses were performed for the downstream embankment slope when no material is retained upstream. Subsequently, with all parameters kept constant, the same slope was then checked when water is retained upstream, and finally for varying slurry solids concentration. Special attention was paid to the boundary between sedimentation and consolidation, defined as the solids concentration limit beyond which effective stresses start to develop. From the stability analyses performed, it is found that the factor of safety of embankment slope varies nonlinearly with total unit weight of the slurry. For coal tailings slurry, factor of safety reduced from 1.24 when water is retained to 1.15 when tailings slurry with ${c_w}$ c w = 60% is retained, representing a drop by 7.3%. [ABSTRACT FROM AUTHOR]

Numerous recent failures of tailings storage facilities (TSFs) (e.g., the 2019 Brumadinho failure in Brazil, the 2018 Cadia failure in Australia) have occurred in the last decade, providing important case histories and lessons to improve the design of TSF facilities. This study is focused on the Cadia TSF failure; specifically, we reexamine and expand the triggering analyses conducted in the forensic study after the failure. In addition, this study also presents the first comprehensive posttriggering and runout assessment of the Cadia failure. The triggering mechanisms were evaluated through Lagrangian-based analyses with the finite-difference method (FDM), which is well suited for small to moderate deformations, whereas the posttriggering mechanisms and runout were evaluated using the material point method (MPM), which is well suited for the evaluation of large deformations. The FDM-based analyses show that the interaction between a relatively weak layer in the foundation [Forest Reef Volcanic Unit A (FRV-A)], the deposited tailings, and the construction of a buttress system is critical in explaining the failure triggering. The MPM-based assessments are useful in investigating posttriggering mechanisms, suggesting a retrogressive failure and stress redistribution occurring within the mine tailings. In addition, the MPM-based assessments also explore the influence of key factors on the posttriggering mechanisms and runout. These factors include the tailings liquefaction extent and strength, the failure propagation rate, the strength of the foundation materials, and the buttress construction. The analyses suggest that the foundation strength, mine tailings liquefaction extent, and buttressing affect the runout assessments significantly. In this context, MPM proves to be especially useful in investigating postfailure conditions. [ABSTRACT FROM AUTHOR]

Tailings dam breaches (TDBs) and subsequent flows can pose significant risk to public safety, the environment, and the economy. Numerical runout models are used to simulate potential tailings flows and understand their downstream impacts. Due to the complex nature of the breach-runout processes, the mobility and downstream impacts of these types of failures are highly uncertain. We applied the first-order second-moment (FOSM) methodology to a database of 11 back-analyzed historical tailings flows to evaluate uncertainties in TDB runout modelling and conducted a sensitivity analysis to identify key factors contributing to the variability of the HEC-RAS model output, including at different locations along the runout path. The results indicate that prioritizing resources toward advancements in estimating the values of primary contributors to the sensitivity of the selected model outputs is necessary for more reliable model results. We found that the total released volume is among the top contributors to the sensitivity of modelled inundation area and maximum flow depth, while surface roughness is among the top contributors to the sensitivity of modelled maximum flow velocity and flow front arrival time. However, the primary contributors to the sensitivity of the model outputs varied depending on the case study; therefore, the selection of appropriate rheological models and consideration of site-specific conditions are crucial for accurate predictions. The study proposes and demonstrates the FOSM methodology as an approximate probabilistic approach to model-based tailings flow runout prediction, which can help improve the accuracy of risk assessments and emergency response plans. [ABSTRACT FROM AUTHOR]

In Chile, the budget for managing environmental liabilities such as abandoned tailings impoundments is limited. Using native and endemic plant species to remove heavy metals from tailings represents a low-cost alternative. Ex situ phytoremediation experiments were conducted over a period of seven months. The endemic species Lycium chilense and native species Haplopappus foliosus were used to remove copper and lead from mine tailings. The results indicate that both species can concentrate levels of Cu and Pb higher than the toxicity threshold in the roots and aerial parts, and present high removal efficiency for Cu higher than 50%. In both species, the concentrations of the target elements are higher in the roots than in the aerial parts. Haplopappus foliosus presents the best performance, accumulating higher concentrations of Cu and Pb than Lycium chilense, and presenting a bioconcentration of over one for Cu. [ABSTRACT FROM AUTHOR]

Due to the logistical challenges associated with using nuclear densitometers at remote sites, the industry is seeking an alternative method to determine the in situ density and moisture content during the construction of filtered tailings facilities. This study aims to investigate the impact of salinity on soil electrical properties and evaluate the feasibility of using an electrical density gauge (EDG) to measure the in situ density and moisture content of saline filtered tailings. The results indicate a dependence of electrical measurements on salinity. To develop procedures for soil calibration models of filtered tailings, standard Proctor tests were first conducted using Devon silt. These procedures were then applied to the filtered tailings to establish correlations between electrical properties (dielectric constant, impedance, capacitance-to-resistance ratio) and physical properties (density and moisture content) at varying salinities. It is suggested to build the soil calibration model using an EDG within a water content range of 10% to 18%. Furthermore, the effectiveness of the developed calibration models has been validated, demonstrating the applicability of the EDG instrument for filtered tailings in a saline environment. However, applying the salinity correction is crucial when the sample has a considerably different salinity than the calibration model. [ABSTRACT FROM AUTHOR]

A method to assess the influence of tension cracks on the seismic external stability analysis of geosynthetic-reinforced soil slopes is carried out in the present study. In addition to being subjected to uniform surcharge loading, hydrostatic and hydrodynamic pressures with water on both sides of the c-ϕ soil slope and seismic inertia forces are considered, and the reinforcement length for both sliding and overturning conditions is evaluated by using a two-part wedge mechanism. The analysis is implemented separately by considering and neglecting the effect of the formation of tension cracks, and reinforcement lengths are evaluated for both the slope angles 60° and 70°. It is seen that when the horizontal seismic acceleration coefficient increases from 0 to 0.2 for a 60° slope angle under the direct sliding mode of failure for a particular set of input parameters as shown in Table 3, the required minimum length of the geosynthetic reinforcement increases from 0.59H to 1.30H, and in the overturning mode, it increases from 0.46H to 0.60H, when the analysis is implemented without considering similar tension cracks when tension cracks are considered in the study, for the increases in kh, as mentioned previously, required minimum length of the geosynthetic reinforcement against direct sliding mode of failure increases from 0.80H to 1.67H, and increases from 0.55H to 0.64H for overturning mode of failure. In addition to kh, the influence of the height of water on the downstream side, pore pressure ratio, soil friction angle, cohesion, and surcharge on the length of reinforcement against sliding and overturning modes of failure are presented in this paper in the form of design charts. The results obtained from the present study are compared with the previous literatures and usefulness of the present method in analysis of reinforced soil slopes against direct sliding and overturning modes of failure has been proposed. The present research work delves into the external stability analysis of reinforced soil slopes. This analysis evaluates the optimal length of reinforcement necessary to maintain long-term safety and stability against potential failures, such as direct sliding and overturning. While direct sliding is influenced by forces pushing the slope forward, overturning is concerned with rotational risks. Geosynthetic reinforcement for soil slope stability plays a crucial role in stabilizing slopes across various infrastructures: highways, railways, airports, landfills, mining operations such as tailings dams and heap leach pads, urban developments, and erosion control measures along riverbanks and shorelines. Adopting the insights and methodologies of this research can amplify the safety benefits by reducing landslide risks and facilitating the customization of designs according to specific site conditions. This approach paves the way for a more efficient use of resources, ultimately slashing costs and bolstering the long-term reliability of slope performance. Furthermore, the study presents a clear analysis of geosynthetic-reinforced soil slopes, considering soil properties, failure risks, seismic forces, and water effects. This framework, suitable for both experts and novices, bridges academic research with practical engineering, making the latest insights usable and valuable for the engineering community. [ABSTRACT FROM AUTHOR]

Intensive economic development is associated with an increasing demand for raw materials, including minerals. An illustrative example of this issue is the development of the copper industry. A significant problem arising from the scale of copper production is the management of an ever-growing amount of post-flotation tailings. This necessitates the need to ensure the continuity of safe storage. This study presents the results of studies on the behavior of deposits in the Żelazny Most Tailings Storage Facility (Poland). The primary objective of this study was to estimate the settlements of tailings under variable deposition conditions. The results were assessed using two methods: indirect and direct; this was based on cone penetration test (CPTU) results. The results were verified using Modified Cam Clay (MCC) modeling. Depending on the type of test, settlements ranged from several dozen centimeters to over three meters. Despite the observed differences, the results of both CPTU methods indicate a convergent trend in tailings behavior. Conversely, the results estimated using the direct method and numerical modeling demonstrate a high level of agreement. [ABSTRACT FROM AUTHOR]

On March 27, 2022, a tailings dam in Jiaokou County, Shanxi Province, China, experienced a sudden breach leading to 224,000 m3 of released tailings that flowed downstream and damaged infrastructure. The tailings flow exhibited relatively slow movement according to eyewitnesses, with the complete duration of the failure process lasting 20–30 min. In order to reconstruct the slow motion of the tailings flows, we have adapted the mass flow simulation software r.avaflow to effectively simulate the slow-flow dynamic. In addition to the numerical simulation, we conducted a comprehensive investigation using satellite-based interferometric synthetic aperture radar (InSAR), optical satellite images, field surveys, unmanned aerial vehicle (UAV) photogrammetry, borehole drilling, and laboratory tests, with the aim of identifying underlying causes of this failure incident. The numerical simulation results showed a good representation of the observed impact area and reported time span, illustrating that the maximum simulated velocities during the entire flow slightly exceeded 6 m/s. InSAR analysis indicated a phase of rapid deformation that coincided with an unprecedented autumn storm in early October 2021, followed by a prolonged period of slow movements until the collapse, with an average line-of-sight (LOS) velocity of 24 mm/year. Through remote sensing surveys and field investigations, we observed the following deficiencies in design, construction, and operation of the Jiaokou TSF: (i) the TSF underwent an extra round of excessive loading from July 2021 onwards, despite being decommissioned in December 2019. and (ii) the TSF fell short of conventional design standards by the absence of drainage and seepage control measures and inappropriate dam construction methods (loess stacking). We conclude that the stability of the Jiaokou TSF was adversely affected by the extreme storm event in conjunction with deficiencies in TSF management, in particular the overloading that likely led to pore water pressure build-up and sudden strength loss. This failure incident is of significance as it draws attention to the need for more robust risk management of the thousands of existing TSFs in China. [ABSTRACT FROM AUTHOR]

The study specifically focused on the Hongliulin mining area, where a total of 40 soil samples were meticulously collected and analyzed from within a 1000 m radius extending from the tailings dam. The findings revealed that soil pH within the 0–1000 m range generally leaned towards the alkaline side. In terms of soil nutrient content, encompassing factors such as soil organic matter (SOM), total nitrogen (TN), total phosphorus (TP), total potassium (TK), alkali nitrogen (AK), available phosphorus (AP), and quick-acting potassium (AK), the variations fell within the following ranges: 2.23–13.58 g/kg, 0.12–0.73 g/kg, 0.18–1.15 g/kg, 9.54–35.82 g/kg, 2.89–6.76 mg/kg, 3.45–11.25 mg/kg, and 5.86–130.9 mg/kg. Collectively, these values indicate relatively low levels of soil nutrients. Within the 0–500 m range of soil samples, the average concentrations of Cd, Hg, Pb, and As were 0.778, 0.198, 24.87, and 17.92 mg/kg, respectively. These concentrations exceeded the established soil background values of Shaanxi Province and emerged as the primary pollutants in the study area. Within this same range, the mean values of eight toxic metals (Pi) were ranked in the following descending order: 1.726 (Hg), 1.400 (As), 1.129 (Cr), 1.109 (Pb), 0.623 (Zn), 0.536 (Cd), 0.309 (Cu), and 0.289 (Ni). With the exception of Hg, As, Cr, and Pb, which exhibited slight pollution, the other toxic metals were found to be within acceptable pollution limits for this sampling range, in line with the results obtained using the geo-accumulation index method. The average potential ecological risk index for the eight toxic metals in the study area stood at 185.0, indicating a moderate overall pollution level. When assessing individual elements, the proportions of ecological risk attributed to Hg, As, Pb, and Cd were 34.57%, 27.44%, 25.11%, and 23.11%, respectively. This suggests that the primary potential ecological risk elements in the study area are Hg and As, followed by Cd and Pb. Notably, toxic metals Hg and Pb, as well as As and Pb, exhibited significant positive correlations within the sampling area, suggesting a common source. An analysis of the relationship between soil physicochemical properties and toxic metals indicated that soil pH, SOM, TN, and TP were closely linked to toxic metal concentrations. The toxic metal elements in the research area's soil exhibit moderate variability (0.16 < CV < 0.36) to high variability (CV > 0.36). Within the range of 0–200 m, the CV values for Cd and Hg exceed 1, indicating a high level of variability. The coefficient of variation for SOM, TP, AP, AK and TK is relatively high with the of 2.93, 2.36, 2.36, 21.01, 7.54. The soil in the sampling area has undergone significant disturbances due to human activities, resulting in toxic metal pollution and nutrient deficiencies. [ABSTRACT FROM AUTHOR]

To investigate the influence of a geogrid-reinforced tailings dam on the seepage stability of the dam body, this paper was based on the field test of a reinforced tailings accumulation dam. The study utilized the finite element strength reduction method to simulate the stability of the main dam of the Fengshuigou tailings reservoir under different seepage conditions using ABAQUS software. Additionally, the paper discussed the impact of conventional heightening, dry beach length, and geogrid reinforcement on the position and safety factor of the saturation line of the dam body. The results showed that when the dam body was raised, the saturation line rose by 2.8–5.3 m, resulting in a decrease in the safety factor. The geogrid effectively reduced the height of the saturation line in the tailings dam. In comparison to the unreinforced condition (dam heightening), the saturation line of the tailings dam decreased by 0.9–2.8 m under the local reinforcement condition and by 3.2–12.5 m under the overall reinforcement condition. The geogrid significantly improved the stability of the tailings dam. Furthermore, under the local reinforcement condition, the safety factor of the dam increased by 3.8–5.5%, and under the overall reinforcement condition, it increased by 35.9–42.9%, when compared to the unreinforced condition. Increasing the dry beach length improved the stability of the tailings dam, and under normal working conditions, the safety of the tailings dam was much higher than under the minimum dry beach condition. These results served as a reference for the design of the dam and the new tailings reservoir, laying a foundation for the sustainable development and environmental protection of the tailings pond. [ABSTRACT FROM AUTHOR]

The dynamic stability of tailing ponds depend largely on the dynamic characteristics of tailings sand. To explore the dynamic characteristics of tailings sand under different consolidation conditions, consolidated undrained triaxial tests under different dry densities, consolidation ratios and containing pressures, the dynamic shear stress, liquefaction stress ratio, dynamic strength index, dynamic pore water pressure, dynamic modulus, and damping ratio of tailings sand under different consolidation conditions were analyzed. The dynamic shear stress linearly changed with the number of failure vibrations. The liquefaction stress ratio increases with an increase in consolidation ratio, conforming to the quadratic polynomial of the origin. With an increase in failure vibration times, the dynamic internal friction angle decreases gradually. Under different failure vibration times, the dynamic internal friction angle increases with an increase in consolidation ratio and dry density. An exponential function model of dynamic pore pressure growth suitable for equal pressure and bias consolidation conditions is proposed, and the fitting effect is favorable. The dynamic shear modulus ratio decreases with an increase in dynamic shear strain; the damping ratio increases with an increase in dynamic shear strain. The research results can provide a theoretical reference for seismic liquefaction of tailings dams in high-intensity seismic areas. [ABSTRACT FROM AUTHOR]

Breaches of tailings dams have had catastrophic consequences in the mining industry worldwide. Therefore, the characteristics of tailings and their effects on the stability of tailings dams need to be investigated. In this paper, the mechanical properties of uniform tailings and smaller sedimentary tailings are analyzed in laboratory testing. The critical hydraulic gradient of tailings is explored and a tailings dam model is constructed. The results of testing indicate that the strength of tailings gradually decreases with an increase in the content of fine particles smaller than 0.075 mm. The critical content of fine particles is 35% fine particles smaller than 0.075 mm. The strength, cohesion, and internal friction angle of uniform tailings are greater than those of smaller sedimentary tailings. The critical hydraulic gradient decreases with an increase in the content of fine particles smaller than 0.075 mm, and the critical content of fine particles is again approximately 35%. However, the critical hydraulic gradient of smaller sedimentary tailings is higher than that of uniform tailings. An equation is presented to calculate the critical hydraulic gradient of tailings. The seepage failure of the tailings dam can be divided into four parts. An equation is presented to calculate the critical hydraulic gradient of a tailings dam. [ABSTRACT FROM AUTHOR]

Tailings volumes continue to collectively increase worldwide, leading to larger dams and tailings management facilities. With numerous high-profile dam failures in the past decade, the risks of these management practices are also growing. A potential shift to waste management practices at mineral mines is to commingle waste rock and dewatered tailings. This blended material should have superior physical strength properties provided by the waste rock together with improved chemical stability characteristics associated with the low permeability of the tailings. Ideally, commingled tailings and waste rock can be used to construct various mined earth landforms that are both physically and chemically stable, which will enhance operational performance and ultimately provide for the sustainable decommissioning and closure of the mining facility. To study these materials, the University of Alberta Geotechnical Centre is working with global industry partners to test commingled materials from several mine sites with varying ore and host rock types and climate regimes. The first stage of this study is described here and is focused on the optimum density, saturated hydraulic conductivity, and soil–water characteristic curves of various blend ratios, performed at laboratory scale. [ABSTRACT FROM AUTHOR]

An instrumented test section was constructed and monitored for 14 years to characterize the hydrology of rock-armored earthen final covers used for uranium mill tailings disposal facilities in semiarid and arid environments. The test section included two different test areas constructed with the same earthen materials and methods employed at an adjacent disposal facility. Both test areas contained a large (10×20 m) instrumented drainage lysimeter to monitor the water balance at near-field scale. Herbicide was applied to the surface of both test areas to preclude vegetation for the first 7 years, simulating conventional practices used by the DOE. After 7 years, herbicide application ceased on one test area ("naturalized" test area), and vegetation was allowed to establish. Treatment of the other ("conventional") test area continued as before. Percolation rates increased in both test areas during the initial 7 years while herbicide was being applied. Percolation rates ranging from 10 to 47 mm/year were measured in wetter years, which is considerably higher than anticipated (3 mm/year). Increases in saturated hydraulic conductivity of the protection layer and the radon (Rn) barrier contributed to the higher percolation rates. Ceasing herbicide application in the naturalized test area had a profound effect on the hydrology. As vegetation established, evapotranspiration increased, volumetric water contents in the protection layer and Rn barrier decreased, and the percolation rate decreased significantly. In contrast, the conventional test area continued to perform as before, with elevated volumetric water contents and higher percolation rates in wet years. [ABSTRACT FROM AUTHOR]

In this study, a robust non-Newtonian numerical model that can simulate coupled mudflow and sediment transport processes is used to model downstream geomorphic changes during a tailings dam failure. The catastrophic breach of the Mount Polley tailings dam is studied to assess the model performance. Spatial and temporal variation of flow properties like density, viscosity, yield stress, sediment size fractions, and friction are considered in the model. A flexible triangular mesh is adopted, and this helps reduce the computational time significantly compared with structured grid with the same average resolution. High resolution multitemporal digital elevation models (DEMs) are used for the detection of geomorphic changes and estimation of erosion and deposition volumes. The results indicate that the final distribution of tailings deposits obtained from the model results is in good agreement with that obtained from topographic analysis. The model predicted the total volume of erosion and deposition with almost 93% accuracy. The tailings characteristics followed the full Bingham model during the propagation. Different runout scenarios obtained from the mudflow-morphodynamic model and a mudflow fixed-bed model are analyzed, and it was concluded that maximum mudflow depth of the flood wave is higher when bed entrainment is considered. Sediment concentration is higher in the wavefront and middle regions and lower in the tail zone. The mudflow fixed-bed model could underestimate the downstream flood arrival time. The results also confirm that the adopted approach can efficiently model the sediment budget in the study site and the volume of tailings and bed materials released to the downstream lake. Tailings dams are used to store waste solids and water generated during mining operations. Failure of such dams can cause serious damage to human settlements and the downstream environment. For public safety, it is necessary to conduct proper risk assessment, and numerical modeling is crucial for estimating flood magnitude, flood path, and flood arrival time. Tailings water is high in sediment concentration and is viscous; thus, its flow characteristics are different from that of pure water. During the collapse of tailings dam, erosion of the downstream terrain occurs, and changes in the downstream channel morphology can be potentially significant. There can also be a change in the total sediment load when additional solids get eroded from the bed layer. The modeling approach used in this study helps to model erosion and deposition patterns and estimate the downstream flood arrival time when transport of sediment in the downstream channel is considered along with the viscous nature of tailings. When conducting risk assessment of tailings dam failures and when planning for evacuation, this mobile-bed modeling approach can be implemented by design engineers and emergency planners. [ABSTRACT FROM AUTHOR]

The No.4 tailings pond of the Dexing Copper Mine is the second largest in Asia. The tailing pond is a dangerous source of man-made debris flow with high potential energy. In view of the lack of effective and low-cost global safety monitoring means in this region, in this paper, the time-series InSAR technology is innovatively introduced to monitor the deformation of tailings dam and significant key findings are obtained. First, the surface deformation information of the tailings pond and its surrounding areas was extracted by using SBAS-InSAR technology and Sentinel-1A data. Second, the cause of deformation is explored by analyzing the deformation rate, deformation accumulation, and three typical deformation rate profiles of the representative observation points on the dam body. Finally, the power function model is used to predict the typical deformation observation points. The results of this paper indicated that: (1) the surface deformation of the tailings dam can be categorized into two directions: the upper portion of the dam moving away from the satellite along the Line of Sight (LOS) at a rate of −40 mm/yr, whereas the bottom portion approaching the satellite along the LOS at a rate of 8 mm/yr; (2) the deformation of the dam body is mainly affected by the inventory deposits and the construction materials of the dam body; (3) according to the current trend, deformation of two typical observation points in the LOS direction will reach the cumulative deformation of 80 mm and −360 mm respectively. The research results can provide data support for safety management of No.4 tailings dam in the Dexing Copper Mine, and provide a method reference for monitoring other similar tailings dams. [ABSTRACT FROM AUTHOR]

Tailing ponds are a major hazard source with the risk of dam breaks. To predict the impact of tailings pond dam breaks more accurately, one needs to quantitatively understand the dam-breaking process of the tailings reservoir and its downstream impact. This study is based on an old tailings pond that is about to be put out of service and the proposed new tailings pond next to it. Study the inundation range of the new and old tailing ponds with simultaneous overtopping dam breaks under actual terrain conditions. First, fine-grained tailings and expanded perlite were selected as the model sand materials, and the appropriate model sand ratio was determined through laboratory tests. Second, the two tailings ponds were tested (at a scale of 1:200), for flood overtopping and simultaneous dam breaks. The dam break, flow, section morphology evolution, submerged elevation, and range were analyzed. Finally, a numerical model was developed using MIKE 21 to simulate the simultaneous overtopping and collapse of the new and old tailings ponds, and the impact of rainfall intensity on the inundation range of the simultaneous overtopping of the dam was analyzed. The research results will guide disaster prevention and mitigation in tailings reservoirs. [ABSTRACT FROM AUTHOR]

Numerical models are used for detailed and site-specific tailings dam breach analyses (TDBAs) to estimate the downstream inundation and deposition resulting from a potential breach at a tailings dam. The results of TDBAs are key inputs into risk assessments, consequence classification, and emergency planning. This paper describes the research and development of a database of 12 tailings dam breach events with a specific focus on observations that are needed for numerical modelling, in conjunction with an assessment of existing dam breach conventions to improve consistency in reporting. The characteristics relevant to modelling include outflow volumes, breach processes, breach geometries, and runout observations local to the downstream area. This study and the new database shed light on the diversity of outflow materials, facility arrangements, breach processes, and downstream environments that affect the breach development and tailings runout. Familiarity with case studies is a crucial element of expert judgement for forward-analysis TDBAs, which this database supports. The database can also be used to define model inputs for back-analysis of additional tailings dam breach events, and simultaneously provides calibration or validation constraints with the runout observations. Continued review and critical assessments are needed to reduce uncertainties and to enhance case history data availability and quality in this database. [ABSTRACT FROM AUTHOR]

Tailings storage facility (TSF) failures have tremendous impacts on surrounding populations, communities, and ecosystems. Therefore, a three-dimension risk matrix considering failure probability, event intensity, and exposure of failure-bearing bodies is established to assess the risk of TSF failure. First, based on the established assessment indicator system, the probability level is determined by the uncertainty measurement theory combined with the extension analytic hierarchy process. Then, the event intensity level is determined by two parameters, namely the volume of released tailings and the maximum distance traveled by tailings. The exposure level is characterized by the potential loss of four failure-bearing bodies, including population, economy, environment, and society. Finally, the risk index is calculated by the Euclidean distance method and the risk level is determined. In the proposed model, the probability, intensity, exposure, and the risk of TSF failure are all divided into four levels (Level I, Level II, Level III, Level IV) from high to low. The application of the case verifies the applicability and availability of the proposed model. [ABSTRACT FROM AUTHOR]

Co-disposition of tailings and waste rocks in open pits in the form of a permeable envelope and/or waste rock inclusions (WRI) can efficiently prevent the transport of contaminants to the environment. Such drainage paths could also accelerate tailings consolidation rate, similarly to WRI in tailings storage facilities, and therefore improve tailings mechanical properties in the short term and maximize the volume of mine waste that can be disposed of. These geotechnical benefits have, however, not been demonstrated yet nor thoroughly investigated. In this research, three-dimensional models were performed to examine the evolution of tailings consolidation in pits under the influences of co-disposed waste rocks. Various disposal scenarios were investigated, including the presence of a permeable envelop only and the addition of WRI as a central inclusion. The influences of operational and practical aspects such as the tailings filling rate, pit slope angles, waste rock and tailings hydro-geotechnical properties, and pit morphology were investigated. Results indicated that a permeable envelope could promote the dissipation of excess pore water pressure (PWP) and accelerate tailings consolidation. The influence zone of the permeable envelope was relatively limited and around 2 times the tailings height. Using a WRI combined with a permeable envelope could be geotechnically beneficial for wide pits whose radius was larger than twice of its depth. Slope angles, filling rate and pit morphology somewhat affected tailings consolidation rate, but their effect was relatively limited and decreased with the increase in the distance to the drainage paths. [ABSTRACT FROM AUTHOR]

Mining Exploration, excavation, and construction are considered as mining activities which are recently growing dramatically. Therefore, utilizing the mining wastes with the least environmental damage is a significant concern. Tailings dams are one of the conventional solutions that store the extracted hazardous substances safely for water resources management and environmental protection. This reseach deals with the effects of monotonic and seismic loadings on silt-sized copper wastes existed in a tailings dam at Northwest Iran as a case study. Various values of initial static shear stress are performed using an automated cyclic triaxial system. Monotonic undrained compressive tests were performed with a relatively constant density and considering three values of 50, 100, and 150 kPa for mean effective stress. Depending on the first density of samples, applying a mean effective confining pressure of 100 kPa, increased the initial densities by 25 to 30% as compared to the initial condition. Moreover, the effect of initial shear stress ratio with three values of 0, 0.2, and 0.4 was evaluated. No peak point was observed for samples under a = 0, whereas, samples with α = 0.4 encountered a peak point before reaching to the phase transformation point. The results of cyclic experiments were used to evaluate capacity energy and residual pore pressure based on the strain energy approach. Cyclic tests on the samples were performed considering the shear amplitude of 0.75% and frequency of 0.3 Hz. It is shown that the most energy dissipation occurs at the first cycle possessing the highest stiffness. For α = 0, energy density increased from 474 J/m³ to 1147.4 J/m³; however, a more intense increase was measured from 682 J/m³ to 5839 J/m3 when α = 0.4. It is also found that applying initial shear stress has a pretty considerable influence on monotonic strength and the liquefaction resistance of silts. The increase of α from 0 to 0.4 yielded a linear increase in the shear strength of samples in the range of 20 kPa to 70 kPa. The results of this paper were then validated accurately through some previous studies. [ABSTRACT FROM AUTHOR]

This study examines the widespread practice of upstream tailings dam construction in metallurgical mines in China, conducting comprehensive testing and research on tailings from various depositional zones of the Caijiagou tailings pond. Analysis of the test results from three types of tailings reveals a systematic relationship between the mechanical characteristics of tailings and their depositional zones: the farther from the dam, the finer the tailings particles, categorized as silty clay tailing, silt tailing, and sandy silt tailing. Consistent patterns were observed in the consolidated-drained shear strength and consolidated-undrained effective shear strength of these tailings. Among these, sandy silt tailing exhibited the highest strength, whereas silty clay tailing displayed the lowest. The dynamic stress–strain relationships of all three tailings types are described using the Hardin equivalent viscous-elastic model, where the initial dynamic shear modulus and the maximum dynamic shear stress in the model increased with effective confining pressure. The damping ratios exhibited a three-stage trend with increasing dynamic strain: gradual increase, rapid growth, and then gradual stabilization. Under various consolidated stress conditions, the ratio of the damping ratio to the maximum damping ratio versus the reduction in dynamic shear modulus showed a favorable linear relationship. Under vibration conditions, the dynamic shear stress corresponding to tailings failure increased with higher effective confining pressure and consolidated stress ratio. Finally, this study summarizes the parameters and indicators related to the saturated tailings of iron mines used in the research. Our work provides a foundation and reference for the design of tailings dams and the development and utilization of abandoned tailings ponds. [ABSTRACT FROM AUTHOR]

Sulfides are usually associated with deposits of metals and coal. The reactive wastes from their exploitation, typically stored in piles and tailings dams, are often the mining sector's primary source of environmental problems. The surrounding river waters can present signs of acid mine drainage, responsible for aquatic ecosystem degradation. So, the main target of the present study is to investigate the impact of this process on the water's environmental quality and potential ecological risk. The study area is located at the Iberian Pyrite Belt, in an old sulfide exploitation, closed without environmental rehabilitation measures. The results exhibit high sulfate concentrations (410,601 mg/L) and potentially toxic elements, with prominence of Fe (134,000 mg/L), overcoming many other extreme cases of AMD pollution. The Ficklin diagram exposes that most samples are classified as "high-acid, high-metal." Two of them have extreme classifications (high-acid, extreme-metal). The pH value is well below the acceptable range for the environmental quality of superficial waters (5–7), measuring at a minimum of 0.84. Regarding seasonal variability, the study showed a higher degree of contamination in dry conditions (e.g., 4,420 mg/L of Cu), while the rainy month had lower concentrations of PTE (186.8 mg/L of Cu for the same sampling point). In addition, the water does not accomplish the environmental objectives established by the EU Water Framework Directive. According to the new approach developed based on a scale adjustment, the potential ecological risk index studied indicates that most sampled sites present strong, very strong, and even extremely potential ecological risk. With a typical Mediterranean climate, the region suffers from water scarcity, predicting increasingly in the future more degrading scenarios for water environmental quality. Consequently, urgent mitigation and remediation measures are necessary to improve and preserve water quality and fulfill the objectives of the United Nations Sustainability Development Goals. [ABSTRACT FROM AUTHOR]

The rupture of the Fundão dam is considered the largest mining failure in history, which had a particularly detrimental impact on fish populations, as the mud from the ore tailings significantly altered the water quality and habitat of Doce River basin. This study aimed to assess the trophic structure of fish communities in areas impacted and not impacted by the dam rupture in the Doce River basin. To evaluate the food web structure, community-wide trophic niche, and trophic positions of fish, stable isotopes of carbon (δ13C) and nitrogen (δ15N) were utilized across ten sites (seven impacted and three control). In general, fish appeared to assimilate resources such as invertebrates, algae, and periphyton, although the importance of each resource varied among sites. The site closest to the dam rupture exhibited a more simplified trophic structure compared to the control sites and those nearer the river mouth. In this site, most fish species occupied a similar trophic position. Trophic niches also exhibited the greatest dissimilarity between the site closest to the dam failure and those farther away from it, with an expansion of trophic niche breadth observed with an increase in the distance from the dam rupture. Our study provided valuable insights into the trophic structure of fish communities within the Doce River basin, shedding light on the trophic ecology of the 59 fish species investigated. We also emphasize the importance of our study for future assessments of ore tailings dam failure disasters and evaluating the effectiveness of mitigation measures for Doce River basin recovery. [ABSTRACT FROM AUTHOR]

The effective detection and monitoring of mining tailings' leachates (MTLs) plays a pivotal role in environmental protection and remediation efforts. Electrical resistivity tomography (ERT) is a non-invasive technique widely employed for mapping subsurface contaminant plumes. However, the efficacy of ERT depends on selecting the optimal electrode array for each specific case. This study addresses this challenge by conducting a comprehensive review of published case studies utilizing ERT to characterize mining tailings. Through numerical simulations, we compare the imaging capabilities of commonly used electrode configurations, six ERT arrays, aiming to identify the optimal array for MTLs' detection and monitoring. In addition, field surveys employing ERT were conducted at the El Mochito mine tailings site to detect zones saturated with leachates within the tailing storage facilities (TSFs). The findings indicate that the "Wenner-Schlumberger" array exhibits superior data resolution for MTL detection. However, the choice of the optimal electrode array is contingent on factors such as survey location, geological considerations, research objectives, data processing time and cost, and logistical constraints. This study serves as a practical guide for selecting the most effective electrode array in the context of pollutant penetration from mining tailings, employing the ERT technique. Furthermore, it contributes valuable insights into characterizing zones saturated with mining tailing leachates within the TSFs, providing a solid foundation for informed environmental management and remediation strategies. [ABSTRACT FROM AUTHOR]

This study provides a predictive analysis of the potential disaster trajectory and extent of a tailings dam in Guangdong Province using GDEM-GAVA technology. Tailings dam failures are complex events characterised by high non-linearity and unpredictability. The research results show that the tailings debris flow followed an inverted V-shaped pattern. The tailings sand travelled approximately 800 m down the valley, with the furthest edge reaching 1387 m and the widest cross-valley spread at 90 m. The average deposition thickness was approximately 6 m and the peak velocity of the debris during erosion reached approximately 35 m per second. In particular, the debris flow engulfed and eroded significant parts of the processing plant, including the main plant area, the washing and screening workshop and the thickener basin. It also affected the storage area, covering approximately 10,000 square m. These findings provide an important scientific basis for early warning and risk assessment of potential tailings dam failures. [ABSTRACT FROM AUTHOR]

A considerable amount of ultrafine magnetite as the iron source will end up in the tailing dams since the magnetic separation process markedly drops as the particle size. Cationic reverse flotation could be one of the main alternatives for recovering ultrafine magnetite. As a systematic approach, this study explored the flotation efficiency and interaction mechanisms of two biodegradable ether amines (diamine and monoamine) to separate ultrafine quartz from magnetite (− 20 µm). Several assessments (single and mixed mineral flotation, zeta potential, contact angle, surface tension measurement, turbidity, and Fourier transform infrared) were conducted to explore the efficiency of the process and the interaction mechanisms. Results indicated that ether diamine and monoamine could highly float ultrafine quartz particles (95.9 and 97.7%, respectively) and efficiently separate them from ultrafine magnetite particles. Turbidity assessments highlighted that these cationic collectors could aggregate magnetite particles (potentially hydrophobic coagulation) and enhance their depression. Surface analyses revealed that the collector mainly adsorbed on the quartz particles, while it was essentially a weak interaction on magnetite. [ABSTRACT FROM AUTHOR]

Remining has been researched for decades, but its potential to supplement virgin extraction is currently unknown. This review addresses the remining of tailings/waste rock, coal residues, and byproduct and primary production materials for renewable energy metals (e.g., Co, Ni, REEs, Mn, Li). Geochemical characterization methods for estimating pollution potential must be supplemented with mineral liberation analysis and process testing to reliably estimate remining's economic potential. National and regional remining characterization efforts currently exist in the U.S., Europe, Australia, and China but will take years to produce viable operations at scale. Tailings hold the most promise due to their large amounts worldwide and the fact that they are already extracted and pre-processed, which reduces energy and water use. Of the processing approaches examined, bioleaching appears to offer the most benefits with the fewest potential downsides. The advantages and challenges of the processing methods and remining sources are presented. Best remining practices are urgently needed to improve resource estimates and avoid impacts such as the tailings dam failures that occurred at remining operations in Romania and South Africa. Interest in remining is booming because it can increase domestic supply. If properly conducted, remining can also improve circularity and environmental conditions in areas affected by existing and legacy mining activity. [ABSTRACT FROM AUTHOR]

Communities and authorities have been dismayed by globally recorded tailings storage facility (TSF) failures in recent years, which have negatively affected the safety of people and the integrity of the environment. In this context, obtaining the social and environmental license to operate TSFs has become a challenging process for mining companies. This has promoted the trend of using mine tailings dewatering technologies in the mining industry, with dry stacking of filtered mine tailings being recognized worldwide as one of the most acceptable, safe, and environmentally friendly solutions. This article presents a new paradigm in managing mine tailings, with disruptive and futuristic characteristics, considering the dry stacking of filtered mine tailings for large-scale industrial production rates over 100,000 metric tons per day (mtpd). Aspects of filtered tailings management are discussed, such as (i) dewatering process plant with thickening/filtering equipment, (ii) conveyance using fixed and movable conveyor belts, (iii) construction of dry stacking of filtered mine tailings facility, and (iv) implementation of Industry 4.0 technologies for automation of the mining processes. Finally, the article discusses how the large-scale filtered mine tailings solution is applied, considering the advances in the equipment's performance and implementation of Industry 4.0 technologies as well as the experience gained worldwide in several mining operations. The future global trend is that mining operations with high daily production of mine tailings will apply dry stacking technology without dams to guarantee sustainability, promote continuity of the mining business, ensure the safety of communities, and conserve the environment. [ABSTRACT FROM AUTHOR]

Significant interest has been focused on recovery rates, recovery options, and recovery utilization when tailings impoundments are re-mined. However, the stability of the tailings dams during the recovery process is also a severe issue. Based on engineering geological surveys and laboratory tests, the evolution of the Tongling tailings impoundment's instability characteristics under different recovery heights and diverse working conditions was analyzed by numerical simulation. Firstly, with the help of 2D software, the position of the tailings dam infiltration line and the alteration of the dam safety factor during the stoping process were calculated. Secondly, 3Dmine (2017) software was used to create the 3D surface structure of the tailings impoundment, and then a 3D numerical analysis model was established by means of Midas GTS NX software. The numerical simulation of seepage and stress analyses were conducted based on the model. Consequently, the evolution of the stability characteristics of tailings dam under different operating conditions was calculated. The research demonstrates that the dry beach length of the tailings pond gradually reduces with a decrease in the extraction height, resulting in a lower infiltration line. Under flood conditions, the saturation line has partial overflow due to the poor seepage discharge capacity of the dam. The total displacement of the dam body is inversely proportional to the retrieval height. The more extreme the analyzed working conditions, the more the safety factor will be reduced. Additionally, the plastic variation area of the dam body will be more comprehensive, which will increase the risk of a dam collapse. [ABSTRACT FROM AUTHOR]

Piping-seepage damage is one of the major factors leading to tailings dam failure. To explore the microscopic influence mechanism of tailings with different fine content on piping development, on the basis of the indoor permeability test, combined with the coupling method of discrete particle flow at the microlevel, through the small seepage model test, the discrete element model of the model test was further constructed. The effects of different fine particle contents on particle size composition, permeability, critical water head, fine particle migration, and porosity of samples were analyzed by an indoor small-scale seepage model and the corresponding numerical simulation study. The results showed that before the occurrence of piping, with the increase of fine particle content, the gradation constant is less than 0.074 mm, and the downward trend changes abruptly, showing a concave curve change. The permeability coefficient showed a decreasing trend, and the critical water head increased. The maximum void ratio and the minimum void ratio generally decreased first and then increased. The strong force chain decreased, and the total force chain increased; there were obvious differences in the change of porosity of different fine particle contents before, during, and after destruction. This was verified by the indoor physical model test that different fine particle contents will lead to different sand inflows in seepage dam break. In practical engineering, it is more helpful to provide a new way for the comprehensive prevention of seepage failure of tailings dam by clarifying the disaster-causing mechanism of piping and seepage failure of tailings dam from the mesostructure. [ABSTRACT FROM AUTHOR]

Tailings impoundments are often prone to failure due to various causes related to complex loading conditions. For instance, tailings impoundments can fail during or after a seismic event, mainly because of the liquefaction of loose, cohesionless tailings. To improve the seismic stability of impoundments, the density of the tailings can be increased or waste rock inclusions (WRI) can be added in the impoundment. This paper presents the results of numerical analyses of the impoundments loaded with a variety of ground motions with different frequencies, scaled at two different levels of intensity representative of two mining regions of Eastern Canada. The results show that the conventional impoundments are subjected to medium to high displacements at the end of shaking; these show a high probability of rupture during the earthquake or in the post-seismic phase. Tailings densification can decrease the volume of liquefied tailings and displacements during the seismic phase but does not significantly reduce the probability of post-seismic failure. WRI can slightly reduce the volume of liquefied tailings, depending on the intensity of the motions, but the reinforcement reduces significantly the lateral displacements; impoundments with WRI show even better performances during the post-seismic phase. The use of WRI is deemed a good approach to ensure the seismic stability of tailings impoundments and reduce the risk of seismically induced failure. [ABSTRACT FROM AUTHOR]

There is a critical need for a global monitoring capability for Tailings Storage Facilities (TSFs), to help protect the surrounding communities and the environment. Satellite Synthetic Aperture Radar Interferometry (InSAR) shows much promise towards this ambition. However, extracting meaningful information and interpreting the deformation patterns from InSAR data can be a challenging task. One approach to address this challenge is through the use of data science techniques. In this study, the representation of InSAR metadata as Entity Embeddings within a Deep Learning framework (EE-DL) is investigated for modelling the spatio-temporal deformation response. Entity embeddings are commonly used in natural-language-processing tasks. They represent discrete objects, such as words, as continuous, low-dimensional vectors that can be manipulated mathematically. We demonstrate that EE-DL can be used to predict anomalous patterns in the InSAR time series. To evaluate the performance of the EE-DL approach in SAR interferometry, we conducted experiments over a mining test site (Cadia, Australia), which has been subject to a TSF failure. This study demonstrated that EE-DL can detect and predict the fine spatial movement patterns that eventually resulted in the failure. We also compared the results with deformation predictions from common baseline models, the Random Forest model and Gaussian Process Regression (GPR). Both EE-DL and GPR greatly outperform Random Forest. While GPR is also able to predict displacement patterns with millimetric accuracy, it detects a significantly lower number of anomalies compared to EE-DL. Overall, our study showed that EE-DL is a promising approach for building early-warning systems for critical infrastructures that use InSAR to predict ground deformations. [ABSTRACT FROM AUTHOR]

This article analyzes the communication actions and response strategies adopted by the State Secretariat for the Environment and Sustainable Development, of the State of Minas Gerais (Semad) and by the National Mining Agency (ANM), public bodies that act in the concession and inspection mining activity in the State and Brazil, during the crises caused by the failure of the ore tailings dams in Mariana (2015) and Brumadinho (2019), operated by the mining companies Samarco and Vale, respectively. From the content and discourse analysis of a set of 357 notes issued to the media, notices, bulletins and videos published on their websites and online social networks, it was concluded that state bodies failed to provide local communities with information that could be substantial in providing security for their lives, property and the environment in which they live. It was found that there was: i) the production and dissemination of information, but without attention to message recipients and marked by unidirectional, top-down, non-dialogical communication; ii) intergovernmental communication, when state organizations speak within the very government entities to which they are linked or hierarchically submitted; iii) low presence and use of social media; iv) low interactivity with users on online social networks; and, v) non-existent interactivity channels, for direct communication with local communities. [ABSTRACT FROM AUTHOR]

Among influencing biotic and abiotic factors, microorganisms predominate litter decomposition, playing an important role in maintaining the ecosystem material cycle. Bothriochloa ischaemum was the dominant plant species in China's Eighteen River tailings dam, and it was selected as the research object. We explored the dynamic of fungal community characteristics in B. ischaemum litter during different decomposition stages and investigated relevant driving factors affecting associative dynamic changes. Results showed that Ascomycetes and Basidiomycetes were the dominant phyla during litter decomposition. At a class level, the relative abundance of Dothideomycetes gradually decreased as litter decomposition progressed while Sordariomycetes gradually increased, ultimately becoming the dominant class. The community structure of the fungal community was mainly affected by litter pH, total carbon (TC), and copper (Cu) content. The fungal community's network structure was the most complex compared to other decomposition stages after 200 days of litter decomposition. Additionally, the fungal community's modularity gradually increased, while the degree of functional differentiation also increased, strengthening fungal community stability during litter decomposition. This study clarifies fungal community structure during litter decomposition in this copper tailings area, and provides a scientific basis for further improving soil fertility and nutrient cycling in mining areas. [ABSTRACT FROM AUTHOR]

The seismic response analysis of a tailing dam is studied using a fully coupled effective stress approach in conjunction with an advanced multi yield surface plastic constitutive model for tailing material. Strain controlled static and cyclic triaxial tests were carried out to obtain the constitutive model for the tailing material. The tailing materials were collected from the Rampura Agucha tailing dam (Rajasthan State, India). A 2D nonlinear finite element (FE) model was then developed using different boundary conditions from the tailing embankment constructed using the downstream and upstream method of rising using OpenSees software. In first case, the model boundary was fixed in both the X and Y directions, and in the second case, viscous dashpots were introduced for both side and horizontal boundaries. The model was validated with experimental results on tailing material. Analyses were carried out considering five different earthquake motions, which were applied at the base. Comparisons of the different boundary conditions in terms of displacement flow vectors, pore pressure and stress-strain curves during shaking are presented. From the analysis, it was observed that the viscous boundary condition replicates the actual field conditions more accurately than the fixed boundary condition. In addition, it was found that the tailing embankment constructed by the downstream and upstream method of rising is not susceptible to liquefaction and lateral spreading for earthquake motions, even for a magnitude > 5.5. [ABSTRACT FROM AUTHOR]

An estimated 23 million people live on floodplains affected by potentially dangerous concentrations of toxic waste derived from past and present metal mining activity. We analyzed the global dimensions of this hazard, particularly in regard to lead, zinc, copper, and arsenic, using a georeferenced global database detailing all known metal mining sites and intact and failed tailings storage facilities. We then used process-based and empirically tested modeling to produce a global assessment of metal mining contamination in river systems and the numbers of human populations and livestock exposed. Worldwide, metal mines affect 479,200 kilometers of river channels and 164,000 square kilometers of floodplains. The number of people exposed to contamination sourced from long-term discharge of mining waste into rivers is almost 50 times greater than the number directly affected by tailings dam failures. [ABSTRACT FROM AUTHOR]

Marilia is the most diverse genus of the caddisfly family Odontoceridae, being distributed throughout the Oriental, Australasian and Neotropical regions. Herein, we describe four new Neotropical species from the Atlantic Forest, Rio Doce basin, Brazil. This basin was partly affected by a flood of 50 million m3 of mud and mining debris in 2015. Due to this disaster, numerous monitoring activities have been carried out to assess the impact generated. Material from one of these attempts was used to describe the new species: Marilia aranan sp. nov., Marilia krenak sp. nov., M. maxakali sp. nov. and M. mukurin sp. nov. Additionally, we provide a new state record of M. guaira from Minas Gerais. Marilia aranan sp. nov. was collected in tributaries as well as in the impacted area 7 years after the disaster. Marilia guaira and M. krenak sp. nov. were collected only in the impacted area. The other species were found only in tributaries. Odontoceridae are considered highly sensitive to disturbance. The presence of Marilia species suggests that parts of the riverbed have recovered from the fine tailing sediments and also highlights the importance of tributaries in the recolonization process. [ABSTRACT FROM AUTHOR]

Tailings dams have relatively high failure rates throughout the world and the consequences of these failures often result in significant loss of life and damage to the environment and property. However, the triggers and failure mechanisms are typically hypothesized and not well understood. To investigate potential triggers and the corresponding failure mechanisms, two centrifuge model tests were conducted on loose slopes made of gold tailings using a scaled viscous fluid to induce instability in flight. A numerical back-analysis was also carried out to investigate and verify the associated mechanisms. Two failure mechanisms were observed in the centrifuge tests. In the first test, large seepage forces caused sloughing at the toe. The initially drained instability at the toe induced significant positive excess pore pressures due to the loose state, as well as to the initially higher degree of saturation in the toe region, triggering localized liquefaction at the toe (undrained response). Due to the localized liquefaction, the tailings at the toe could not support the tailings upstream of the toe, triggering a retrogressive flowslide failure. In the second test, a slope failure occurred due to drained instability, i.e., failure occurred once the drained factor of safety approached unity. No liquefaction was evident, due to the initially lower degree of saturation in the toe region, as well as to the slower rate of shearing compared to the first test. As revealed by both physical and numerical simulations, the structural collapse of the soil resulted in the drained instability of the slope, which triggered a slide-to-flow failure. [ABSTRACT FROM AUTHOR]

Degree of the radon and α-aerosol deviations proposed to obtain the influence of internal damage in the safety assessment of the uranium tailings dam are combined with the cloud model to establish the security and stability assessment of an uranium tailings dam, which take into account imperceptible internal damage of the dam, assisting in improving the technical evaluation. An evaluation of a large uranium tailings dam in southern China shows that the model can accurately evaluate the safety and stability of the uranium tailings dam and can provide guidance for subsequent decommissioning management. [ABSTRACT FROM AUTHOR]

The magnitude of the impacts caused by tailing dam failures represents, in a very short space of time, the potential risks of metals on the environment along time. In riparian soils affected by the failure of Córrego do Feijão Mine dam (Brazil), potential pollution risks were estimated using geochemical indices. Based on background and baseline values, strong anthropogenic interferences in the soil metal enrichment has been evidenced after collapse. Abnormal levels of Cd (1.01 mg kg−1), Cr (80 mg kg−1), As (28 mg kg−1), Cu (90 mg kg−1), Pb (80 mg kg−1), and Ni (35 mg kg−1) in soils were associated to the highest risks. Overall, the potential ecological risk (>600) and pollution load (>5) indices indicated Brumadinho, Mário Campos, Betim and São Joaquim de Bicas as the areas most affected by the tailings spill. For the most areas, the geological accumulation index calculated from baseline values showed high commitments in soil quality, with pollution degree from moderately to strongly polluted (from 3 to 5, for Hg and Ni) and extremely polluted (>5, for Cd and Pb). In order to maintain the functional ecosystem integrity, restorative and reparative actions must be urgently carried out in these areas [ABSTRACT FROM AUTHOR]

Microorganisms have the potential to address environmental pollution, but the interaction mechanism between microorganisms and mine tailings is not well understood. This work was aimed at determining the bacterial isolates in soils and mine tailings and evaluating the distribution of metals, antimony (Sb), and arsenic (As) in the soils around the Komsomolsk tailings. Areas with high concentrations of As, Sb, cadmium (Cd), and lead (Pb) were found. Assessment based on the value of the contamination factor (CF) indicated large-scale As, Sb, Pb, Cd, iron (Fe), bismuth (Bi), and beryllium (Be) pollution, especially in soils sampled from the northeast direction of the mine tailings. Soils had a higher number of CFUs per g of dry weight than did the tailings, ranging from 84 × 106 to 3.1 × 109 and from 20 × 106 to 1.7 × 109, respectively. Arsenic exhibited a positive statistical correlation with the number of CFUs of Agrococcus and Staphylococcus. In addition, a positive correlation was found between the concentration of Co and the number of CFUs of Moraxella and Microbacterium. The Sb exhibited a positive correlation with Streptomyces. These results can be used to develop methods for waste reclamation, including the use of isolated bacterial strains for arsenic removal by precipitation. [ABSTRACT FROM AUTHOR]

The article presents a method for the intensification of a tailings pond. A tailings pond serves for the hydraulic storage of silt-sand waste arising during a flotation treatment and the processing of polymetallic ores. The intensification of the tailings pond consisted of raising its dam system to increase its accumulation space. The total proposed height of the tailings pond dam system after its elevation will be 60 m. The structural and shape arrangement of the dam in the dam system of the tailings pond was the result of a stability analysis of the state of the tailings pond before and after the dam system was raised. The article presents the results of experimental verifications of the geomaterial properties that form quasi-homogeneous units of the tailings pond (subsoil, dam system, and sediment) that serve as the inputs for stability analyses. New limiting and critical water levels are modelled based on the stability analysis for the intensified dam system of the tailings pond, taking into account the standard requirements for its overall stability. [ABSTRACT FROM AUTHOR]