Mining, Metallurgy & Exploration最新文献

Strategies based on the repowering existing and powering new mobile equipment with contemporary diesel engines with substantially lower tailpipe and crankcase emissions are expected to play an important role in the efforts to curtail exposures of underground miners to criteria diesel pollutants. Laboratory characterization of tailpipe emissions for three "clean" engines that meet U.S. Environmental Protection Agency (EPA) Tier 4 final emissions standards were used to assess the viability and effectiveness of those strategies. The evaluated engines were representative of those that achieve the emission standards through implementation of various in-cylinder emissions control strategies, use of crankcase filtration, and use of three types of exhaust aftertreatment systems: (1) diesel oxidation catalytic converter (DOC), (2) combination of DOC and the full-flow wall flow monolith diesel particulate filter (DPF), or (3) combination of DOC, diesel exhaust fluid (DEF)-based selective catalytic reduction (SCR) system, and ammonia slip catalyst (ASC). The study showed that the highest reductions in concentrations of diesel aerosols in underground workings, in terms of both mass and number, could be achieved if the engines, preferably in all power classes, are fitted with viable DPF systems. The use of U.S. EPA Tier 4 final engines equipped with DOC and DOC/SCR/ASC systems could help operators to considerably reduce mass, but not number concentrations of aerosols. The emissions of two of the evaluated engines, one equipped with DOC and the other equipped with DOC/DPF systems, were characterized by substantial secondary NO₂ emissions that would limit the viability of those engines for underground mining applications. The catalyst formulations used in the exhaust aftertreatment systems of the diesel engines marketed to the underground mining industry need to be formulated to minimize the potential for generation of secondary NO₂ emissions. Engines fitted with viable SCR/ASC systems present a low-NO₂ alternative. All three of the evaluated advanced engines were found to have low CO output. Due to nuances associated with the use of diesel-powered mobile equipment in underground mines, the selection and potentially optimization of advanced engines for underground mining applications deserves special consideration.

Maintaining the particulate emissions from contemporary diesel engines equipped with diesel particulate filter (DPF) systems at targeted levels and assuring the effectiveness of DPF systems retrofitted to traditional diesel engines are critical to the efforts of underground mining operations to reduce exposures of miners to diesel particulate matter. The methodologies and instrumentation currently used to support the emission-assisted maintenance (EAM) programs for previous generations of diesel engines are in need of improvement to allow for monitoring low concentrations of complex aerosols emitted by the advanced diesel engines. The results showed that of the test conditions currently used in EAM programs, the torque converter stall and hydraulic stall are the most suitable for assessing the effectiveness of the DPF-based advanced aftertreatment systems. The low idle and high idle test conditions, frequently used in EAM programs for traditional engines, did not produce reliable and reproducible data. The solid particle number (SPN) concentrations proved to be more suitable than total particulate number concentrations as a metric for EAM monitoring of diesel aerosols emitted by advanced diesel engines. Both of the evaluated direct reading instruments, TSI 3795-HC and Pegasor Mi3, provided comparably accurate results of assessments of the SPN concentrations in the targeted range of concentrations between 2 × 10³ and 3 × 10⁶ #/cm³. Those proved to be viable EAM tools for determination of the efficiencies and performance degradation of the DPF system. The findings of this study should provide the underground mining industry with valuable information needed to enhance their EAM programs.

Accurately predicting haul truck (HT) travel times (TT) in underground mines is essential for enhancing operational planning, as it allows planners to forecast extraction rates at each work face, minimize queue-related downtime, and ultimately increase productivity. However, in underground environments where GPS signals are unavailable, beacon-based locating systems have not yet been utilized for this predictive purpose. This study addresses that gap by introducing a machine learning approach for HT TT prediction that relies exclusively on beacon detection data, thus eliminating the need for traditional telemetry. The proposed method combines three route-segmentation strategies-full-route, short-segment, and major-segment predictions-with Gaussian mixture models, long short-term memory networks, and a stacking ensemble. Validated on two underground mines, it outperformed industry benchmarks, reducing prediction error by up to 34% on ascending routes and 18% on descending routes while achieving even greater precision for autonomous HTs. It showcases the untapped potential of beacon-based location systems for predictive applications, supporting mine planners.

Underground mining operations use several remedial measures to alleviate the miners' exposure to respirable dust. This includes maintaining the ventilation airflow, deploying scrubbers on equipment, and using water sprays to move air and dust away from the miners and to capture them. Despite these engineering controls, recent research shows an increased occurrence of exposure-related issues in the impacted miners. Masks and other PPE devices are considered the least preferred in the hierarchy of controls. However, they show a high protection factor if designed properly and according to recommendations. A Powered Air Purifying Respirator (PAPR) is a battery-operated personal scrubber that has found widespread application in industries. This respirator uses a blower to move air through a high-efficiency particulate air (HEPA) filter, delivering the purified air to the user. Its popularity is attributed to its high protection efficiency. This paper summarizes the current applications and evaluation methods of PAPRs. It strongly recommends their usage in underground mines to reduce the risk of mine dust lung diseases such as pneumoconiosis, asbestosis, silicosis, and others that do not have any conclusive treatment. While the high efficiency of the respirators has been demonstrated, we recommend further studies to investigate the unique challenges associated with their use in underground mines. Therefore, this paper also presents computational fluid dynamics (CFD) simulations as a tool to understand the performance of PAPRs in underground tunnels, which could help to understand not only the efficiency, but also the challenges associated with their implementation.

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.

Research on mine self-escape often focuses on coal mining, while perspectives from underground metal/nonmetal miners remain understudied despite their distinct emergency response challenges and unique operating environments. Using a scenario-based survey approach, this study evaluated underground metal/nonmetal miners' perceptions of the usefulness of 18 hypothetical self-escape interventions and how these perceptions are influenced by worker characteristics. Employment type was the strongest predictor of usefulness ratings, with hourly employees rating several self-escape interventions significantly higher than salaried employees, including those related to improving self-contained self-rescuers (SCSRs) and tethered guidance systems. The data suggested potential trends where perceived usefulness increased with more time spent underground and decreased with higher education levels. While previous research found no relationship between these characteristics and coal miners' perceptions of self-escape technologies, our findings suggest these factors do influence metal/nonmetal miners' views. This work contributes to the broader understanding of human systems integration in mining self-escape, reinforcing the notion that technology priorities can differ by user groups, while acknowledging that certain core safety needs may transcend these differences.

This laboratory-scale study presents the development and validation of a hydraulic fracturing technique to directly measure the tensile strength of cemented paste backfill (CPB), providing an alternative to traditional strength testing methods. Fracture initiation pressure (FIP) was used as the primary measure of CPB strength. Experimental results were compared with traditional benchmark measures such as uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), and critical Mode-I fracture toughness (K_Ic). Regression analysis of experimental results revealed a strong linear relationship between FIP and these benchmark strength measures, indicating that FIP can be used as a reliable predictor of CPB strength. However, traditional linear elastic failure models did not adequately explain the observed FIP values, as they significantly over-predicted the CPB tensile strength. To address this, the Point Stress (PS) model was applied, which provided a more accurate prediction of tensile strength, especially in cases involving small boreholes. The PS model explained observed effects of borehole size on the material's response to hydraulic pressurization. This study confirms that hydraulic fracturing, interpreted through the PS model, is an effective method for determining CPB strength and provides a practical alternative measure to conventional testing methods.

Occupational exoskeletons (EXOs) have received growing attention as a new ergonomic intervention to reduce physical demands in various industries (e.g., manufacturing, logistics, construction, and agriculture). However, their potential use in mining has not yet been reported. Survey data (n = 135) were obtained from mining workers in the United States (US) and Indonesia (ID). Qualitative and frequency analyses were used to summarize and compare respondents' perceived barriers, benefits, and promoters to EXO use and adoption. Beta regression analyses were also used to examine whether the perceived likelihood to use arm-support EXOs or back-support EXOs differed between the countries and was affected by demographic or job characteristics, or by perceptions regarding EXOs. Both US and ID respondents reported potential benefits of EXOs for physically demanding tasks such as lifting and overhead work, and they shared concerns about adaptation, uncertainty or lack of knowledge, confined spaces, device weight, potential failure or damage, and costs. However, some key differences also emerged: US respondents were more likely to consider using arm-support EXOs and back-support EXOs, despite expressing concerns about their use; ID respondents, although they reported more existing health and safety hazards, appeared more hesitant about adopting EXOs, possibly due to these additional hazards. These results demonstrate that miners appear to have an interest in EXOs but also emphasize the need to ensure task compatibility, comfort, and affordability to ensure the safe and effective adoption of EXO technology in mining in both developed and developing countries.

Supplementary information: The online version contains supplementary material available at 10.1007/s42461-025-01189-1.

The collapse of a mine pillar is a catastrophic event with great consequences for a mining operation. In spite of the low probability of occurrence for a pillar collapse in comparison to other ground control instability issues, these consequences make these events high risk. Therefore, the design of these structures should be considered from a risk perspective rather than from a factor-of-safety deterministic approach, as it has been traditionally done. This work presents a risk-based pillar design framework that enables to characterize discontinuities' effect in pillar strength, as well as accounting for the possible range of stresses that will be acting on pillars. The proposed methodology is based on the integration of stochastic discrete element modeling for pillar strength estimation, and stochastic continuous modeling for pillar stress determination. This approach was evaluated in an underground dipping stone mine. Using the reliability analysis method, results from the stress estimation model were integrated with those obtained from the stochastic DEM approach, thereby enabling the probability of failure estimation for the pillars throughout the mine. Finally, the methodology was validated by comparing numerical modeling results with LiDAR and photogrammetric surveys from the mine. Results from this design framework provide additional decision-making tools to prevent pillar failure from the design stages by reducing uncertainty. The proposed method enables the integration of pillar design into the risk analysis framework of the mining operation, ultimately improving safety by preventing future pillar collapses.

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.