Search Results (1,164)

Gangue backfilling has become an important technique for promoting environmentally friendly and low-carbon coal mining. The long-term creep behavior of cemented backfill plays a critical role in maintaining stope stability and controlling surface subsidence during long-term service. Although considerable research has been conducted on cemented tailings backfill, systematic investigations on the triaxial creep evolution, long-term strength characteristics, confining pressure effects, and the applicability of the classical Burgers model for gangue–gypsum cemented backfill under engineering-relevant confining pressures remain limited. In this study, the experimental scheme was designed based on field monitoring data from practical backfill mining operations, which indicate that the in situ backfill generally remains stable without significant deformation or instability under normal working conditions. Multi-stage loading triaxial creep tests were conducted on gangue–gypsum cemented backfill under confining pressures of 1, 2, 3, and 4 MPa. The creep deformation characteristics were analyzed using Chen’s superposition method, while the long-term strength was computed via inflection point method of isochronous stress–strain curves. The parameters of the Burgers creep model were identified using the Levenberg–Marquardt optimization algorithm, and numerical verification was performed using FLAC3D. Our findings demonstrate that the creep deformation process of the backfill consists of three typical stages: instantaneous deformation, attenuated creep, and steady-state creep, and no accelerated creep was observed within the applied stress range. The absolute creep strain surges nonlinearly with increasing stress level (S_L), whereas higher confining pressure significantly suppresses the creep response of the material. Within the investigated stress range, the backfill exhibits mainly linear viscoelastic behavior, and its critical long-term strength is not less than 0.9 times the failure deviatoric stress (qf). Although confining pressure enhances the long-term strength, the strengthening effect weakens as the confining pressure increases. Model fitting outcomes imply that Burgers model precisely describes the creep behavior of gangue–gypsum cemented backfill under all test conditions, with correlation coefficients (R²) exceeding 0.97. The identified parameters show systematic variation with S_L, reflecting stiffness degradation and viscous evolution during loading. Numerical simulation results agree well with the experimental data, providing theoretical guidance for mixture proportion optimization, long-term stability evaluation, and stope support parameter design in gangue backfill mining engineering. Full article

Coal preparation tailings from the K18 seam of the Abayskaya mine were evaluated as a potential secondary source of critical rare earth elements (REEs). The study showed that REEs are predominantly associated with the mineral fraction of coal; therefore, during beneficiation, approximately 70% of their total content is transferred to flotation tailings. The concentrations of valuable elements in the tailings are as follows (g/t): Li—65; Sc—16; Y—17; Yb—2.5; V—135; and Ti—2293. These values significantly exceed the Clarke values and are comparable to those of some low-grade primary ores, indicating the potential of coal preparation wastes as a technogenic raw material for critical elements. To extract REEs from the resistant aluminosilicate matrix, a fluorine–ammonium sulfate thermochemical activation method was proposed. Using a probabilistic–deterministic experimental design approach, a mathematical model of the process was developed and optimal parameters were determined (400 °C, 120 min, (NH₄)₂SO₄ consumption—140% relative to Al, NH₄HF₂ consumption—110% relative to Si), providing a feed liberation degree (by Al extraction) of up to 94%. Under optimal conditions, high leaching efficiencies of key elements were achieved: Sc (95%), Y (100%), Yb (100%), and Li (100%). The results demonstrate the significant potential of coal preparation tailings as a secondary resource of rare earth elements and confirm the efficiency of fluorine–ammonium sulfate technology for processing this type of technogenic waste. Full article

Tailings backfilling (TB) is widely recognized as an environmentally friendly and engineering safe technique to enhance mining efficiency. However, the heterogeneous particle distribution in TB slurry, also-named the segregation phenomenon, can significantly affect the mechanical strength of the backfill, especially under high goaf conditions. Therefore, elucidating the spatial distribution characteristics of particles during high-goaf filling has become a crucial research focus for improving the mechanical behavior of tailings backfill. A systematic experimental investigation was conducted in this study, incorporating the similarity principle, to analyze the migration behavior of backfill slurry particles and to clarify how the different backfill heights influence the spatial distribution of fine, medium, and coarse particles. The results indicate a clear vertical variation in PSD. Based on statistical analysis of samples collected from different backfill height experiments, coarse particle content increased progressively from the upper to lower layers (median: 16.2%, 23.6%, and 25.0%), while medium-sized particles remained relatively stable (37.0%, 37.3%, 37.0%). Fine particles dominated overall but decreased with layers (45.6%, 38.8%, 38.3%). Coarse particles tended to settle downward due to gravitational forces, whereas fine particles migrated upward. The distribution of medium-sized particles remained largely homogeneous. Fine and coarse particles were subjected to opposing driving forces. Meanwhile, particles maintained an approximately symmetrical distribution in the horizontal direction. Moreover, when the backfill height exceeded 800 mm, a notable intensification of stratification occurred, indicating a strong height-dependent transition in segregation behavior. In contrast, in the horizontal direction, the PSD showed no clear dependence on backfill height. These findings provide new insights into the mechanisms of particle segregation within backfill materials, offering a theoretical foundation and experimental support for optimizing PSD within the backfill body and elucidating the collapse mechanisms of high goafs. Full article

This study assessed the feasibility of cultivating Lavandula dentata in Technosols produced from fine and coarse coal mining waste, focusing on plant development, substrate functionality, essential oil production, and post-mining ecosystem restoration. The Technosols were formulated using coal waste from the Moatize Coal Mine, Mozambique, combined or not in different configurations with agricultural soil and amended with sewage sludge (3% organic matter) and chemical fertilizer to ensure adequate nutrient availability. The experiments were conducted in 30 L containers, performed in triplicate for each experimental group. All settings allowed good plant growth, although the treatment that used only fine waste presented the closest performance to agricultural soil in terms of the production of aerial biomass. In this case, the dried biomass production of the shoots reached an average of 165 g per pot over 8 months (with a standard deviation of 20.3). The study showed a positive correlation between plant development and the available water capacity of the substrates. The plant tissue of L. dentata, in all the Technosols configurations studied, presented a similar composition to the control, with a biomass composition within the standard range established by the literature. The essential oil production ranged from 0.3 to 0.7% (m/m), averaging 0.5% (m/m), with chemical characteristics also alike the control trial. Technosols composed of coal waste from Moatize appear to be an alternative, both to provide a suitable destination for mining waste and to provide conditions for the revegetation and recovery of degraded areas by coal mining. This avoids the commissioning of nearby areas to supply soil for the restoration process. L. dentata, in addition to its various medical, ornamental, and aromatic uses, has potential as an “ecological trigger” in the restoration process with environmental and socioeconomic benefits. Full article

Uranium mining generates complex multi-element contamination that affects interconnected ecosystem components, posing long-term ecological and sanitary risks; this review places these impacts in a broad environmental context and aims to synthesize current knowledge on the distribution, migration, and accumulation of uranium and associated heavy metals in water, soil, and plants. A structured analysis of international peer-reviewed literature was conducted, focusing on documented pathways of metal release from tailings and waste dumps, geochemical controls on mobility, and biological uptake by vegetation. The reviewed studies consistently show that tailings and disturbed ore-bearing strata act as persistent sources of uranium and heavy metals (e.g., Cd, Pb, Cr, Ni, Zn, Mn, As), which migrate through infiltration, acid mine drainage, and atmospheric dispersion, leading to elevated concentrations in surface and groundwater and long-term accumulation in soils. Soils function as the principal sink controlling metal bioavailability, while vegetation reflects the bioavailable fraction and exhibits pronounced species-specific accumulation patterns. These processes establish an active “soil–water–plant” transfer chain that facilitates entry of contaminants into food webs. The synthesis indicates that combined uranium and heavy metal contamination represents a sustained ecological and public health concern in uranium-mining regions and underscores the need for integrated monitoring of soils, waters, and vegetation, along with quantitative risk assessment and scientifically grounded remediation strategies. Full article

While mining is a highly important economic activity, it generates considerable environmental impact, especially during the grinding and extraction stages of metallic minerals, leading to the formation of waste known as mine tailings. These mine tailings, often abandoned in various regions of Mexico due to a lack of prior environmental regulations, contain heavy metals that pose a risk to both the environment and human health. In Huautla, Morelos, where metals such as silver (Ag), gold (Au), copper (Cu), lead (Pb), and zinc (Zn) were extracted from the 16th century until 1988, it is estimated that there are approximately 780,000 tons of mine tailings. These mine tailings are contaminated with heavy metals such as cadmium (Cd), Cu, chromium (Cr), manganese (Mn), Pb, and Zn, and the bioaccumulation and biomagnification of these metals have been documented in various plant and animal species in the region, indicating their bioavailability. The study conducted in this area consisted of determining the concentration of Cd, Cu, Cr, Mn, Pb, and Zn, as well as the sequential extraction of mine tailings 1 and 2 to identify metal bioavailability. The results showed for both mine tailings, that the metals with the highest concentrations were Pb (mine tailing 1: 1666 ± 317.7 mg/kg, mine tailing 2: 1329 ± 30.8 mg/kg) and Zn (mine tailing 1: 1327 ± 314.9 mg/kg, mine tailing 2: 1099 ± 34.3 mg/kg), found in fractions IV and VI, respectively. In mine tailings 1, the main bioavailable metals were Cd (75.3%), Mn (53%), Pb (39.8%), and Cu (36.4%), while in mine tailings 2, the bioavailable metals were Cd (56.8%), Pb (37.9%), and Cu (29.3%). In general, Cd and Pb exhibited the highest bioavailability in both mine tailings. According to the calculated risk indices, bioavailable Cd and Pb pose the highest pollution, ecological, and non-carcinogenic risk in both mine tailings, while bioavailable Cr showed the highest determined carcinogenic risk. This study demonstrated that the mining waste from Huautla contains high levels of bioavailable heavy metals, posing ecological and public health risks, and provides valuable information for the development of effective environmental remediation strategies. Full article

Soil heavy metal pollution caused by mineral resource extraction activities poses a serious threat to the ecological environment within and surrounding mining areas. As a highly concealed toxic heavy metal, arsenic (As) urgently requires the establishment of efficient pollution monitoring methods to achieve pollution prevention and control, as well as environmental remediation in mining areas. This study investigated the feasibility of hyperspectral remote sensing inversion for soil heavy metal arsenic based on ZY-1 02E hyperspectral satellite imagery, focusing on a mining area and its surrounding soils in Sanlisha’an, Wuxuan County, Guangxi. Full Constrained Least Squares (FCLS) was employed to separate mixed pixels and enhance soil spectral contributions in ZY-1 02E imagery, thereby mitigating vegetation interference. Six mathematical transformations, including RT, AT, FD, RTFD, ATFD, and SD, were applied to both the original and enhanced spectra to enhance spectral features. The correlations between the transformed spectra, as well as the original image spectra (S), and soil As concentration were analyzed; then the spectra strongly correlated with soil As concentration were selected to construct Ratio Spectral Index (RSI) and Normalized Difference Spectral Index (NDSI). Correlation matrices were calculated between RSI/NDSI indices and As concentration. Sensitive features were screened using an improved Successive Projection Algorithm (SPA). As concentration inversion was also performed with four models: traditional regression models, PLSR and MLR, and ensemble learning models (RF and XGBoost). In the soil contribution-enhanced spectral modeling results, the optimal transformation–index combination is ATFD-NDSI. The performance indicators of each model are as follows: MLR test set R² = 0.65, PLSR test set R² = 0.62, RF test set R² = 0.7, and XGBoost test set R² = 0.64. The results indicate that the ATFD-NDSI-RF ensemble model provides the best performance. By integrating multiple decision trees, RF effectively handles complex nonlinear relationships, thus enhancing the accuracy and generalization ability of predication. The analysis of NDSI–ATFD–RF inversion results based on sampling points indicates that model error correlates with the pollution intensity gradient, showing greater errors, especially in high-concentration areas, but still maintaining strong correlations (tailings reservoir: r = 0.92, forested areas: r = 0.96, and cropland: r = 0.83). The spatial distribution reveals that the inversion results are closely similar to the spatial distribution of IDW interpolation. Areas with high As concentrations are concentrated in the tailings reservoir and in the southeastern part of the study area. The correlation coefficient between the inversion results and IDW interpolation is 0.6, which further verifies that the inversion results effectively reproduce the spatial distribution trend of highly polluted areas. Full article

Low-saturated hydraulic conductivity covers (LSHCC) or hydraulic barriers are one of the reclamation techniques used to control the acid mine drainage generation (AMD). These covers are intended to limit the infiltration of water into reactive tailings. Compacted clays are among the materials used as LSHCC. The performance of clay-based hydraulic barriers can be affected by their geotechnical and hydrogeological properties. Freeze–thaw cycles can increase their saturated hydraulic conductivity (k_sat). However, these effects can be minimized by adding amendments. To evaluate the performance of these clay-based covers, four field experimental cells were built. The first one simulates a cover composed entirely of clay, the second a clay–silt mixture, the third a clay–sand mixture and the last two layers of clay with an intermediate layer of silt. Each cell has been equipped with a monitoring station with continuous measurements of volumetric water content, suction and temperature. In situ permeability tests were also conducted to assess field hydraulic conductivity. Numerical simulations were also conducted to evaluate the water balance for each cover scenario. The laboratory results showed low-saturated hydraulic conductivity values meeting waterproofing criteria, whereas field measurements and calibrated model values were consistently higher and exceeded the waterproofing criteria. Infiltration monitoring indicated that 15 to 40% of precipitation infiltrated the covers, with possible overestimation due to preferential flow. Discrepancies between laboratory and field-saturated hydraulic conductivity values were mainly attributed to inadequate compaction, unfavorable weather conditions, and excessive water content during cover installation. Variations in saturated hydraulic conductivity over time were generally within statistical variability, although differences among cells and responses to wetting–drying cycles highlight the influence of construction conditions on field performance. Full article

Mining tailings are waste generated continuously in large quantities and have accumulated over time, posing significant environmental challenges. This study evaluates the influence of low (MinPC) and high (MaxPC) current densities on the recovery of elements from untreated mining tailings obtained from SCM Paicaví by electrodeposition. To define both conditions, tailings were placed in containers with electrodes spaced 3–18 cm apart, and controlled currents of 1–100 mA were applied. Although MaxPC electrodes recovered a greater mass of material (1.51 g) than MinPC (0.22 g), the latter achieved higher enrichment of elements such as Ni and Mn. Under MinPC conditions, Ni exhibited the highest recovery, enrichment (19.3), and selectivity (4.8), whereas under MaxPC, the enrichment and selectivity decreased to 9.6 and 2.0, respectively. Elemental analyses (XRF, AAS, ICP-MS), together with mineralogical characterization (XRD, FT-IR, and SEM-EDS), identified quartz, pyrite, and chlorite as the main phases associated with the recovered elements. Overall, the results demonstrate that direct electrodeposition enables selective metal recovery from untreated tailings without pretreatment, chemical reagents, or additional water consumption, providing a novel and environmentally sustainable route for tailings valorization. Full article

Securing mine sites is a challenging task due to the complexity of the infrastructure, the variety of physical and digital components, the distribution of assets and machineries, and the large number of stakeholders involved. Given the risks that are present in Tailings Storage Facilities (TSFs), mine operators are seeking technologies to accurately monitor the state of their dams. The latest developments implement evolutive monitoring and responsive risk management systems by adapting accurate Internet of Things technologies, automated mathematical model calculation to continually monitor the structural/geotechnical aspects of TSF, and a portfolio of innovative applications to support decision-making. Within this study, a comprehensive methodology is developed for assessing the environmental sustainability of a smart monitoring solution combining the life cycle assessment (LCA) method with the environmental risk assessment, which quantifies risk reduction potential. The use case scenario is identified based on real industrial data, also aligned with the common characteristics of tailing dams in Europe. Environmental sustainability of the smart monitoring solution is assessed through a cradle-to-grave LCA based on the ReCiPe 2016 (v1.1 Midpoint (H)) method. Monitoring impact alone is reduced primarily by the 40% reduction in monitoring visits, while the results show the environmental improvement of the TSF life cycle by 24% for CO₂-eq., as a step in-line with the EU’s long-term strategy for total decarbonisation in 2050, and Sustainable Development Goal 9 for Industry by the United Nations. Additionally, the 27% freshwater ecotoxicity reduction, 20% human toxicity (cancer) decrease, and the rest of the studied categories indicate an overall footprint improvement for the monitoring solution application on TSFs. The findings demonstrate clearly theoretical, practical and policy implications, not only for the benefit of such solutions for environmental protection, but also for the necessity of integrating risk in sustainability analysis approaches. Full article

This study examines the environmental risks associated with talc mining in Slovakia, focusing on various aspects. It applies a structured risk assessment methodology to evaluate the probability and severity of environmental impacts stemming from talc extraction, flotation, and tailings pond operations. Key stressors include chemical pollutants such as oils, diesel, and flotation reagents, as well as physical disruptions like georelief alteration and vegetation loss. The findings highlight high environmental risks from technical infrastructure leaks and tailings pond operations, particularly regarding groundwater contamination and landscape modification. Moderate risks were identified in diesel and oil substance leakage, while flotation processes posed minimal risk. The research underscores the need for improved risk mitigation strategies, such as enhanced monitoring and containment systems, to protect local ecosystems and water resources. The study contributes to a better understanding of the long-term environmental impacts of mineral resource exploitation and provides a foundation for more sustainable mining practices. Full article

Mining tailings are considered a significant environmental challenge due to their large quantities and high residual metal content, particularly iron. Recent developments in biogenic technologies offer a sustainable approach to recovering valuable materials from these waste streams. We consider a biogenic iron oxide nanoparticles production process from mining tailings as an environmentally friendly route to magnetic materials. Microorganisms, including iron-oxidizing and iron-reducing bacteria, microalgae, and fungi, can convert soluble and mineral-bound iron into iron oxide nanoparticles (NPs) phases such as magnetite, maghemite, and hematite. These biogenic iron oxide NPs often exhibit specific physicochemical properties, including controlled particle size, high surface area, and engineered magnetic properties, which make them potentially important for applications in environmental remediation, catalysis, and agriculture. The processes behind microbial iron conversion, the parameters governing mineral phase formation, and the approaches for optimizing the process are presented. This strategy supports the circular economy concept by combining biogenic synthesis with various forms of mining waste, thereby reducing environmental threats associated with tailings confinement and providing an environmentally friendly mechanism for the production of value-added magnetic materials. Full article

Aiming at cemented tailings backfill (CTB) damage and collapse induced by secondary stope blasting in the sublevel open stoping with a subsequent filling method, a new CTB damage control technology termed “Synergistic Utilization of Cumulative Blasting Damage (SU-CBD)” is proposed. First, theoretical analysis is conducted to reveal the influence mechanism of rock mass damage accumulation on its blastability, verifying the feasibility of the SU-CBD technology. Subsequently, based on the LS-DYNA R11.1 software and RHT material model, a numerical model is established, and the small restart technique is adopted to realize the continuous simulation of multi-row blasting. By comparing the rock mass fragmentation ratio, energy distribution, and CTB damage degree among different charge structure schemes, the optimal charge structure combination is obtained. To address the issues of retained rock mass damage and overbreak caused by multiple blasting operations, a dynamic adjustment method for blasthole row spacing is proposed, with the optimal row spacing increment determined as 1.0 m. To verify the technical effectiveness, field industrial tests are carried out in Stope No. 5 of the 4500 m–4550 m mining level in the Bangzhong Zinc-Copper Mine. The results show that the optimized blasting scheme keeps the CTB intact without collapse and achieves uniform ore fragmentation, and the oversize ore ratio (particle size > 50 cm) is only 2.4%, with the numerical simulation results in good agreement with the field test results. The research indicates that the SU-CBD technology can effectively reduce the powder factor and CTB blasting damage while ensuring the blasting fragmentation effect, providing reliable blasting design support for the secondary stope. Full article

Subsequent backfilling mining methods are critical technologies for the safe exploitation of deep metal mines, while the resource utilization of ultrafine tailings is a core component of green mining practices. This study focuses on the ultrafine tailings from the Tianxing iron mine to investigate the preparation and optimization of backfill slurry. The goal is to develop a low-cost, high-strength slurry suitable for large-scale preparation and long-distance pipeline transportation. The main findings are as follows: the 6920-type anionic flocculant was identified as the optimal agent, with an optimal dosage of 20 g/t, achieving an underflow concentration of 70.1% under dynamic testing conditions; a novel cementitious material (NCM) exhibited a 28-day uniaxial compressive strength of 3.14 MPa at a low binder-to-tailings ratio of 1:10, outperforming ordinary Portland cement and Slag Micro-powder; and the optimal slurry concentration was determined to be 70%, which provides a favorable balance between mechanical strength and flowability. Furthermore, economic analysis indicates that adopting NCM can reduce annual backfilling costs by approximately 13 million RMB. By establishing an integrated technical framework that includes “property characterization–flocculation optimization–binder selection–rheological regulation,” this study addresses key technical challenges associated with ultrafine tailings backfilling, significantly reduces binder consumption and overall backfilling costs, and provides precise parameter guidance for industrial-scale applications. The proposed approach demonstrates significant practical value for promoting green and sustainable mining development. Full article

The mining industry still faces major environmental and socioeconomic problems as a result of tailings dam failures, which highlights the urgent need for improved monitoring and early-warning systems. This research offers practical recommendations for improved monitoring and safer design practices, in addition to investigating the use of digital image processing (DIP) as a non-invasive technique for tracking slope deformation in tailings dam models subjected to incremental pore water pressure increases. To replicate real-world conditions as closely as possible, a scaled laboratory embankment was built using coarse and fine tailings. During controlled pore-pressure loading, more than 500 high-resolution photos were taken, recording the entire deformation sequence from initial displacement to slope failure. The images were processed using Mathematica to generate pixel-by-pixel displacement fields and vector plots, providing a detailed visualization of deformation mechanisms. The findings demonstrated that DIP accurately detects and measures surface displacement, revealing the mechanisms, direction, and intensity of deformation. This study illustrates the extensive potential of DIP for real-time monitoring by directly connecting slope instability triggered by incremental pore water pressure with visual indications of slope deformation. While the results confirm the strong potential of DIP for deformation monitoring with a minimum detectable displacement of approximately 1.0 mm under controlled laboratory conditions, its field application may be affected by scale effects, variable lighting, and environmental occlusion. The mining industry benefits greatly from the insights gained through in-depth image analysis, which promotes safer tailings dam design and management. Overall, DIP can provide a reliable, scalable foundation for real-time deformation monitoring in operational tailings dams, where continuous image-based measurements can help identify early signs of instability and support proactive risk management. Full article