Mining, Metallurgy & Exploration最新文献

Stockpiling and storage of topsoil for use in reclamation and revegetation are common practices for many mining operations. However, stockpiling can lead to significant changes in topsoil physical and biogeochemical properties that may be detrimental to reclamation. The objective of this research was to assess the effect of long-term stockpiling on soil biogeochemical properties in a semiarid region. We hypothesized that soil properties would change systematically with depth reflecting a shift to anaerobic conditions and resulting in a general decrease in soil health. To address this hypothesis, boreholes > 20-m deep were drilled into a 14-year-old topsoil stockpile at a copper mine in Arizona and samples collected every ~ 75 cm. Samples were analyzed for soil DNA biomass, texture, general agronomic properties, mineral composition, oxalate and dithionite extraction of active mineral phases, and total elemental composition. Depth profiles revealed non-systematic changes in biogeochemical variables with depth, including variation in soil DNA biomass, organic matter (OM), extractable nitrate (NO₃-N) and ammonium (NH₄-N) nitrogen, plant-available manganese (Mn) and iron (Fe), and oxalate-extractable Mn and Fe. Differences in biogeochemical properties were associated with zones of variable redox state mediated by OM content and layer depth. Anaerobic zones were observed at depths greater than 4 m where OM > 1%, and aerobic zones were observed at depths up to 15 m where OM < 1%. This study demonstrates the importance of stockpile composition on biogeochemical processes during storage and contributes to improved understanding of topsoil management as a resource for reclamation of degraded mine lands in semiarid environments.

Supplementary information: The online version contains supplementary material available at 10.1007/s42461-024-01164-2.

Occupational exposures to respirable dusts and respirable crystalline silica (RCS) is well established as a health hazard in many industries including mining, construction, and oil and gas extraction. The U.S. National Institute for Occupational Safety and Health (NIOSH) is researching methods of controlling fugitive dust emissions at outdoor mining operations. In this study, a prototype engineering control system to control fugitive dust emissions was developed combining passive subsystems for dust settling with active dust filtration and spray-surfactant dust suppression comprising a hybrid system. The hybrid system was installed at an aggregate production facility to evaluate the effectiveness of controlling fugitive dust emissions generated from two cone crushers and belt conveyors that transport crushed materials. To evaluate effectiveness of the system, area air measurements (n = 14 on each day for a total of 42 samples) for respirable dust were collected by NIOSH before, during, and after the installation of the dust control system in the immediate vicinity of the crushers and the nearby conveyor transfer point. Compared to pre-intervention samples, over short periods of time, geometric mean concentrations of airborne respirable dust were reduced by 37% using passive controls (p = 0.34) but significantly reduced by 93% (p < 0.0001) when the full hybrid system was installed. This proof-of-concept project demonstrated that the combined use of active and passive dust controls along with a spray surfactant can be highly effective in controlling fugitive dust emissions even with minimal use of water, which is desirable for many remote mining applications.

In the context of modern industrialization and global development, blasting operations have become essential for meeting the growing demand for raw materials through large-scale opencast mining. However, if not meticulously planned and executed, blasting can lead to adverse outcomes, including backbreak, flyrock, and structural damage caused by vibrations. These issues can significantly undermine operational safety, reduce efficiency, and negatively impact environmental sustainability. Addressing these challenges requires innovative control techniques, including empirical approaches like vibration analysis, machine learning methods, and numerical simulations, to mitigate the negative impacts effectively. This paper focuses on a numerical approach to controlling backbreak, presenting a comprehensive 3-dimensional finite element (3D FE) model developed to simulate rockmass deformation under blast-load conditions. The model is implemented using Ansys Explicit Dynamics, incorporating the Drucker-Prager strength model and the Jones-Wilkins-Lee equation of state for explosives to accurately predict the extent of rock breakage zones. To evaluate its predictive accuracy, this 3D FE model is compared with 3-dimensional nearfield vibration models. Our findings reveal that the FE model closely aligns with both the vibration model outcomes and field observations, establishing its reliability in predicting backbreak without the need for historical blasting data. This aspect is particularly valuable for preliminary checks in new blasting sites, where historical data may not be available. By offering a dependable alternative for predicting the rock breakage zone extent, the FE model significantly contributes to the refinement of blasting designs, enhancing the safety, productivity, and environmental stewardship of surface mining operations.

In this study, feldspar ore was successfully enriched using a two-stage process. Initially, dry magnetic separation was employed to remove iron oxide, followed by cationic flotation to eliminate gangue minerals containing free silica. A feed sample with a size fraction of (− 0.25 + 0.053) mm, pre-treated by attrition scrubbing and dry high-intensity magnetic separation (cleaned twice), was used for flotation. Cetyltrimethylammonium bromide (CTAB) served as a cationic collector for feldspar, while hydrofluoric acid (HF) acted as a depressant for quartz at a pH of 2.5–3. Factors affecting the flotation process were investigated. The flotation resulted in a concentrate with 64.75% SiO₂, 21.00% Al₂O₃, 0.08% Fe₂O₃, 4.00% Na₂O, 10.22% K₂O, and 94.71% feldspar, compared to the feed sample, which contained 76.03% SiO₂, 14.73% Al₂O₃, 0.08% Fe₂O₃, 2.99% Na₂O, 4.77% K₂O, and 59.43% feldspar. Overall, the results indicate that using CTAB as a feldspar collector, combined with a small amount of HF as a quartz depressant in acidic conditions, effectively reduces chemical consumption when compared to alternative methods for treating similar feldspar samples.

Particulate materials are prevalent in the natural and engineering fields, and the screening of particulate materials is constantly improving with the development of industrial needs. New and efficient screening equipment is endless. Discrete element simulation plays a vital role in the design and development of vibrating screens, which improves the design speed of new screening machines and reduces the research and development cost. The purpose of this paper is to collect the literature published in recent years on the research development and application of discrete elements, with the expectation of providing a relatively comprehensive and advanced literature review on the application of discrete components in the field of vibratory screening, which includes the introduction of particle models, the setting of crucial simulation parameters, discrete elements in screening optimization. Meanwhile, the results of many researchers in the field of vibratory screening simulation in recent years are summarized to provide readers with references on the use of the discrete element method in the screening simulation process and to provide a cutting-edge summary for subsequent research.

Slope failures in mine overburden dumps are recurring incidents leading to the loss of life and property. Since slope stability depends on several factors that may vary over a period of time, such as slope parameters and material characteristics, regular slope stability studies performed periodically are necessary for assessing the risk of slope failure more effectively. This study aims to analyse the slope stability of opencast lignite mine overburden dump benches by determining the slope factor of safety via 2-D limit equilibrium software. On the basis of their factor of safety values, slopes are categorized as ‘highly stable’, ‘moderately stable’ and ‘unstable’. Among the three slopes analysed, two are moderately stable, and one is highly stable. Slopes with a factor of safety ≥ 1.3 are considered highly stable, and those with a factor of safety between 1 and 1.3 are considered moderately stable. Unstable slopes have a factor of safety of less than 1. Through a series of iterative procedures, the maximum permissible bench heights for high slope stability are determined. By comparing the results with the present bench heights, height reductions are recommended for each bench. The study found that the heights of benches with moderately stable slopes must be reduced by 10 to 15 m to achieve high slope stability. The heights of the upcoming benches are recommended not to exceed 50 m. This study not only analyses the present conditions of slope stability but also provides recommendations regarding bench heights for attaining high slope stability, thus providing an actionable conclusion that can be implemented in the current state of practice. Although the study has limitations in terms of applicability outside of opencast mines with soft strata, the methods described can prove to be valuable for determining how to approach and proceed with similar case studies on slope stability.

Single-fracture Oriented Roof-cutting Technology (SORT) is a key technology in the pillarless self-formed roadway mining method, which is a popular and widely used new coal mining method in China. In previous model tests, SORT was usually replaced by chain saw cutting or pre-installed isolation boards. This resulted in its process and effect being not realistically simulated. To solve this problem, the process and rock-breaking mechanism of SORT were analyzed in detail in this paper. Meanwhile, some factors affecting the performance of SORT were discussed by using the sensitivity analysis method. Based on this, a new SORT model test method was proposed and verified by a series of experiments. The results show that the most critical factors affecting the technical effect of SORT are blasting energy and energy concentration coefficient. In the model tests, explosive materials with fast reaction speed and good detonation effect should be preferred. On the other hand, compared with flexible energy guiding devices, rigid devices can play a better role in energy focusing and guidance, thus maximizing the simulation of the technical effect of SORT. Based on this idea, a series of tests were carried out with Ningtiaota coal mine as the engineering background. According to the test data, the optimal explosive material was determined to be low-cost black powder composed of potassium nitrate, sulfur and other components. Pre-fabricated slit steel pipe was determined as the optimal energy guiding device. In addition, the optimal values of other parameters were determined, including slit energy agent dosage and simulation device spacing. Finally, the method and device proposed in this paper were applied in the model test. The results show that the model test results are in good agreement with the field monitoring data. This proves that the SORT model test method, device, and test parameters proposed in this paper are feasible. This provides a new reference idea for further research on the pillarless self-formed roadway mining method, as well as other research involving SORT.

Identifying geochemical halos is critical in locating ore deposits and detecting deeper anomalies. This study presents an approach that combines unsupervised random forests and clustering large applications algorithms to identify intricate patterns in a borehole set of 29 elements data in a suspected gold mineralization area in Iran. The raw geochemical data goes through a log-ratio transformation, followed by staged factor analysis to identify ten main elements. The proposed methodology separated the ten main elements into three distinct halos. The clustering process was validated using various statistical parameters to substantiate the approach’s effectiveness in handling data outliers. The Sequential Indicator Simulation method was used as a geostatistical tool to perform conditional simulation of front, near-ore, and tail halos. Multivariate modeling revealed that the primary halos exhibit a specific spatial pattern encompassing the ore deposit, reinforcing the possibility of a more profound anomaly. The three-dimensional (3D) results obtained from this investigation were subsequently compared with existing geological reports and a comparative method (K-means). This comparison revealed the successful detection of the near-ore halo within the subsurface, extending from the Earth’s surface to a depth of 200 m. Existing geological reports and databases confirm that this halo is strongly associated with the oxide zone.

To investigate the failure mechanisms of slopes and develop an integrated approach for slope reinforcement, monitoring, and early warning, the Daye open-pit copper mine slope was selected as the case study. Initially, field investigations and analyses of engineering geological conditions were performed to elucidate the deformation instability mechanisms of the slope. Subsequently, a numerical model was established to evaluate the slope reinforcement efficacy of constant resistance large deformation (CRLD) anchor cables with different anchorage lengths. The results demonstrate that increasing the anchorage length of CRLD anchor cables leads to a reduction in total slope displacement and an enhancement in the slope safety factor. The axial force distribution within the slope was segmented into three distinct zones: concentration area, transition area, and stable area. The optimal safety factor was achieved at an anchorage length of 20 m. This study provides insights into the slope deformation mechanisms, the anchorage performance of CRLD anchor cables, and their optimal anchorage lengths. Based on the findings, an integrated scheme for slope reinforcement, monitoring, and early warning is proposed. The field application results indicate significant improvements in the stability of the Daye open-pit copper mine slope.

This paper synthesizes new and previous work on the tabular sandstone-hosted uranium and vanadium deposits of the La Sal district, one of the principal U-V districts of the Colorado Plateau. Deposits form a 1–3 km wide, E-W trending 30 km long trend spanning the Utah-Colorado border, approximately orthogonal to the Uravan belt. Ore is hosted in the uppermost fluvial subarkosic sandstones of the Salt Wash Member of the Jurassic Morrison Formation and typically forms channel-parallel, elongate orebodies up to 180 m long, 90 m wide, and 1 m thick. Sandstones are interbedded with silty, muddy, and calcareous units. Principal mineralogical changes include quartz overgrowths accompanied by destruction of early diagenetic hematite. Precipitation of compositionally distinct carbonate cements and clays followed. Bleaching was prior to and/or contemporaneous with mineralization, which is restricted to bleached rocks. Petrography shows that ore minerals (uraninite, coffinite, and montroseite) in part predate growth of authigenic quartz and calcite cements, followed by the formation of ferroan dolomites. Abundant V-rich phyllosilicates may reflect back-reaction of montroseite with quartz and other minerals. New U-Pb dating of ore-hosting calcite (~144 Ma) and K-Ar dating of V-clays (~42–36 Ma) parallel published results for elsewhere on the Plateau. Sedimentary structures (e.g., crossbedding), primary porosity, and the distribution of lithofacies in the local Salt Wash channel system control mineral growth. The thin section- to district-scale observations suggest that mineralization formed either by mixing of two fluids, or alternatively by reaction of oxidized fluids with a reductant earlier introduced during bleaching, as has been suggested in other Plateau deposits.