Underground Metal Mines Research Articles

Traffic Congestion Scheduling for Underground Mine Ramps Based on an Improved Genetic Scheduling Algorithm

The dispatching of trackless transportation on the ramp of underground metal mines is closely related to the transportation efficiency of daily production equipment, personnel, and construction materials in the mine. The current dispatching of trackless transportation on the ramp of underground metal mines is discontinuous and imprecise, with unscientific vehicle arrangement leading to low efficiency and transportation congestion. This paper presents this study, which puts forward a kind of trackless transportation optimization method that can fully make use of the ramp in the roadway, and the slow slope fork point can be used for the trackless transportation vehicle passing section to improve the efficiency of trackless transportation on the ramp. This study adopts the principles of fuzzy logic and uses interval-based positioning instead of real-time positioning to effectively reduce the spatial complexity inherent in the algorithm. At the same time, this research presents a modified genetic algorithm that incorporates a time-loss fitness calculation. This innovation makes it possible to differentiate traffic priorities between different types of vehicles, thus bringing the scheduling scheme more in line with the economic objectives of the mining operations. Various parameters were determined and several sets of simulation experiments were carried out on the response speed and scheduling effect of the scheduling system, resulting in a 10 to 20 percent improvement for different vehicles in the efficiency of underground mining transport operations.

Development of Fuzzy-AHP and WPM based MCDM Model for Mining Method Selection

The study aims to select the proper mining method for underground metal mines using the Fuzzy-Analytical Hierarchical Process (FAHP) and Weighted Product Method (WPM). The study considered various deposit characteristics such as dip of the orebody, orebody thickness, shape of the orebody, depth of the orebody from the surface, and grade distribution. Based on these characteristics block caving, sublevel stoping, sublevel caving, room and pillar, shrinkage stoping, cut and fill stoping methods are evaluated. FAHP method calculates the weights for each deposit characteristic and WPM calculates the scores of mining methods for the given mine body characteristic. FAHP and WPM models are applied to a uranium mine in India. The appropriate extraction method for the considered mine is found as cut and fill stoping. The same method is also used at the mining location.

Improvement of Fluidity and Long-term Strength of Cemented Paste Backfill with Low Calcium Fly-ash

ABSTRACT Waste rocks and tailings are widely applied materials in underground metal mines to backfill mined-out areas. To test the effect of low calcium fly ash on slurry fluidity and long-term strength of cemented paste backfill, orthogonal experiments of backfill proportions with variable levels of waste, tailing, fly ash, water and their combinations were carried out. Results show that slurry slump is most sensitive to mass concentration, and slurry fluidity is optimal when fly ash-cement ration is 1:1. The longterm strength of cemented paste backfill after curing for 56 days is significantly affected by cement-(tailing + waste) ratio, and slightly evolves regardless of fly ash-cement ratio. Fly ash promotes the generation of active silicon oxide and aluminum oxide, which fills the pores within the backfill. The optimal proportion of cemented paste backfill is 77% mass concentration, 8:2 tailing–waste ratio, 1:30 cement-(tailing + waste) ratio and 1:1 fly ash–cement ratio. The correlative slurry slump and long-term backfill strength meet the requirement of pumping and backfill mining. Additionally, an industrial scale loop pumping test of backfill slurry shows the pipeline transportation resistance is 4 kPa/m, pipeline diameter is optimal at 150 mm, and flow rate is optimal at 90–100 m3/h. The experiment confirms that proper addition of low calcium fly ash is conducive to improve the slurry fluidity and long-term strength of cemented paste backfill.

Functionalization of Filter Media for Improved Crystalline Silica Analysis Using Raman Spectroscopy

ABSTRACTRespirable crystalline silica (RCS) poses significant health risks in workplaces, including underground coal mines, metal and nonmetal mining, construction sites, fire suppression, and oil and gas industries. Raman spectroscopy offers a promising avenue for direct analysis of RCS on sample filters with minimal pretreatment. However, the presence of organic compounds (OC) in the samples can generate fluorescence signals that interfere with RCS measurements, potentially saturating the detector even at short integration times, particularly when using portable Raman instruments. This study explores a novel approach to address these challenges by functionalizing filters with a hydroxyapatite/silver bromide/titanium dioxide (HAT) photocatalyst, facilitating the oxidation and removal of OC using the Raman excitation laser. Photocatalytic degradation experiments conducted on polyvinyl chloride (PVC) filters preloaded with HAT and anatase titanium dioxide (TiO2) particles demonstrated that HAT significantly enhances the degradation of OC, such as oxalic acid, under visible light irradiation compared to TiO2. Additionally, fluorescence interferences were reduced for coal dust samples analyzed on functionalized silver filters using a portable Raman instrument. The efficacy of HAT in OC photocatalytic degradation on silver filters was further confirmed using a benchtop micro‐Raman system. Filter functionalization had minimal impact on filtration efficiencies and pressure drops, indicating the feasibility of this approach for improving RCS analysis while maintaining filter performance.

Mechanism, prevention, and control of mining-induced dynamic disasters in underground metal mines in China: Challenges and solutions

Mechanism, prevention, and control of mining-induced dynamic disasters in underground metal mines in China: Challenges and solutions

Numerical study on the gas-solid diffusion characteristics of airflow and dust particles in metal mine blasting excavation under three hybrid ventilation modes

Dust pollution has long been a challenge in the blasting excavation of underground metal mines, and uncontrolled diffusion of dust particles seriously endangers the health and safety of workers as well as the environment in underground space. Most existing research on dust diffusion focuses on fully mechanized coal mining face or borehole drilling, where the dust source emission characteristics differ significantly from metal mine blasting excavation. Furthermore, it is still unclear how the ventilation modes of Far-Pressing-Far-Absorption (FPFA), Near-Pressing-Far-Absorption (NPFA), and Far-Pressing-Near-Absorption (FPNA) affect the mechanism of dust diffusion in the breathing zone. In this work, gas-solid flow characteristics in a typical metal mine blasting tunnel are numerically studied based on Euler-Lagrange method. The interphase forces between airflow and dust particles are comprehensively modeled, and the particle diffusion effect caused by fluid turbulence is described by the discrete random walk model. Five typical regions for airflow disorder phenomena in the working tunnel are predicted, including the jet development region, the return airflow core region, the airflow reversal region, the airflow recirculation region, and the secondary flow region. The spatial distribution of dust exhibits nonuniform characteristics under turbulent airflow transport. The time results of the monitored dust concentration reveal that the junction of the working tunnel and the return airway is a key area of focus for the prevention and control of dust pollution. Among the three ventilation modes, the Far-Pressing-Near-Absorption (FPNA) ventilation mode has the best dust removal efficiency. The supply vent further from the blasting face allows the jet to fully develop, while the exhaust vent closer to the blasting face allows dust particles to be drawn in and discharged earlier. Under the condition of fixed total power consumption for the supply and exhaust fans, a larger exhaust airflow velocity helps remove dust from the breathing zone.

A New CRITIC-GRA Model for Stope Dimension Optimization Considering Open Stoping Stability, Mining Capacity and Costs

In the long-hole stage open stoping with subsequent backfill mining of underground metal mines, the selection or optimization of stope dimension parameters is significant for safe and economic mining operations. To analyze the optimal stope sizes, the Mathews empirical graph method and FLAC3D numerical method can be used, but the analyzed safety results of the two methods are generally independent from each other. More importantly, economic indicators including production capacity and mining costs should be considered simultaneously to optimize the stope dimension which was mostly ignored in previous reports. In this paper, a new CRITIC-GRA model was proposed for the first time to build up a multi-factor quantitative optimization for stope dimension, which allows for a comprehensive analysis with preset influential safety and economic indicators. The indicators considered include the safety indicators such as stability probability for the side walls and roof of the open stope via the updated Mathews graph method, maximum displacement, plastic zones volume and maximum principal stress via FLAC3D simulations, as well as economic indicators such as mining costs and stope production capacity in mine operations. The model was then illustrated in an underground iron mine. With the given rockmass quality in the mine, the overall stability of the open stope can be improved instead of reduced to enlarge the single stage stope height (60 m) to a double stage height (120 m) by reducing the stope width from 20 m to 15 m, thereby significantly increasing the mineable ore amount and improving the stope safety. An integrated evaluation of open stope stability, mining capacity and costs objectively determined that scheme No. 10, with a slope length of 50 m, a width of 15 m and a height of 120 m, was the optimum out of the 20 preset schemes. The new CRITIC-GRA model offers a dependable reference tool for determining the optimal stope dimensions in similar underground mines.

Gas-Solid Flow Characteristics of Airflow and Dust Particles in Blasting Excavation of Underground Metal Mine Tunnels.

Effective dust removal has long been a challenge in the blasting mining of underground metal mine tunnels, and uncontrolled dust diffusion seriously endangers workers' respiratory systems and the underground space safety environment. However, the vast majority of existing numerical studies on dust diffusion are focused on coal mine fully mechanized mining, which is different from metal mine blasting excavation in terms of stope structure and dust properties. Furthermore, the mechanism by which the forced and exhaust ventilation modes affect the diffusion characteristics of inhalable particles is unclear. In this work, gas-solid flow characteristics for dust diffusion in a typical metal mine blasting tunnel were numerically investigated based on the Euler-Lagrange method, where the blasting face instantly released 6.37 × 107 particles with 100 different sizes, ranging from 0.8 to 200 μm. The interphase forces between airflow and dust particles are comprehensively modeled, and the particle diffusion effect caused by fluid turbulence is described by a discrete random walk model. Detailed information for airflow turbulence and particle migration was revealed, and dust removal efficiencies for inhalable particulate matter (PM10) by forced, exhaust, and hybrid ventilation were analyzed. Numerical results predict a complex airflow pattern in the working roadway, including the jet-flow region, return airflow core region, airflow disorder region, and secondary flow region. Dust diffusion temporal characteristics can be divided into three stages, namely, the initial stage of dust generation, the efficient ventilation and dust removal stage, and the later stage of dust diffusion. Dust diffusion spatial characteristics indicate that under the Coanda wall attachment effect, the dust concentration exhibits nonuniform distribution in both vertical and horizontal directions of the return air roadway. The dust removal efficiency of hybrid ventilation on inhalable particles above respiratory height is better than that of forced ventilation, especially in the return air roadway. The additional exhaust air duct based on forced ventilation can discharge more inhalable particles from the tunnel.

Study on the Movement of Overlying Rock Strata and Surface Movement in Mine Goaf under Different Treatment Methods Based on PS-InSAR Technology

The goaf treatment of underground metal mines is an important link in mining, and it is particularly important to master the laws of overlying rock strata and surface movement of goaf. In this paper, Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) technology is used to monitor the surface subsidence of the Taibao lead-zinc mine, and the surface subsidence laws of goaf-closure, partial-filling, and full-filling treatments are analyzed by the time-series method. The findings indicate that the surface subsidence of the closed goaf is solely governed by the pillars, with the quality of these pillars playing a pivotal role in controlling such subsidence. Factors like stope span also influence the surface subsidence of partially filled goaf. Prior to compaction, it is primarily the pillars that control surface subsidence; however, after compaction, filling and pillars jointly regulate this phenomenon. Notably, in filled goaf, the quality of both roof and pillars significantly impacts surface subsidence. Before compaction occurs, control over surface subsidence is not evident, yet post-compaction, the filling is effective and tends to stabilize this process. The research findings are significant in enhancing goaf’s treatment efficacy, mitigating surface damage and minimizing ecological environmental impact.

Study of the Critical Safe Height of Goaf in Underground Metal Mines

The empty-space subsequent filling mining method is the main mining scheme for underground metal mines to achieve large-scale mechanized mining. The stage height, one of the main parameters of this method, affects the various production process aspects of the mine and influences the stability of the goaf. In order to determine the stage height scientifically and rationally in the empty-space subsequent filling mining method, a formula for the stabilized critical safe height of a high goaf in an underground metal mine was derived based on Pu’s arch equilibrium theory, Bieniawski’s pillar strength limit theory, and the Kastner equation and combined with the results of an orthogonal analysis to rank the importance of the main factors in the formula. A copper mine in Jiangxi Province was used as a case study, with the reliability of the formula verified by numerical simulation and industrial testing. The factors in the formula influencing the critical stabilized safe height of the goaf were, in descending order, the compressive strength of the rock body, the width of the two-step mining pillar, the width of the one-step mining room, the mining height, and the depth of mining. Based on the calculation results, the recommended stage heights are 30 m (−378 m middle section) and 25 m (−478 m middle section) in the area of poor rock body stability and 50 m in the area of better rock body stability. The simulation results show that the goaf is significantly affected by the compressive stress under the condition of a certain rock body stability and that the compressive stress increases with increasing goaf height. The minimum recommended values of the sidewall safety coefficients in areas of poor and better rock stability are 1.04 and 1.06, respectively. The volume deviation coefficients of the three industrial test mines were all controlled within 3%, indicating that no obvious collapse and destabilization phenomenon occurred in the goaf. This paper provides some theoretical and applied guidance for the stage height design of similar underground metal mines using the empty-space subsequent filling mining method.

Revamp of Diesel LHD to Battery LHD for Minimising Operational Cost in Underground Metal Mines

In underground mines, haulage vehicles are routinely employed to move ore from subterranean loading stations to the surface. It's occasionally possible for descending empty cars to stop in a passing lane and wait for moving, heavier vehicles to pass. This is how traffic moves downhill. The number and placement of passing bays affect the haulage productivity of a mine. The operational expenses of the battery LHD and the diesel LHD have been contrasted in terms of gases released, diesel costs, and charging costs. According to our data, using a rechargeable LHD can cut operational costs by 90%.

Investigation of the Application of Complex Function Theory in Underground Mine Design: A Case Study

This study, with the engineering background of the design of a stope involving a sublevel mining method in a certain underground metal mine, explored the application of stress-solving methods based on the complex variable function theory in actual engineering. Three mathematical calculation models based on the functions of a complex variable were established. Through triangle interpolation, mapping functions of a plane with a roadway section and a plane with the stope section were determined. An improved Schwarz alternating method was adopted to study the stability of the roadway and the influence of an adjacent roadway from the perspective of the stress field. In addition, in light of the distribution characteristics of a gangue in the stope, the design parameters of a pillar were optimized, with the pillar’s optimal dimensions determined. The results showed that when the magnitudes of two far-field principal stresses in the rock mass are relatively close, the distribution of the surrounding rock stress around the roadway is more uniform, and tensile stress is less likely to occur. The excavation of a neighboring roadway exacerbates to some extent the side stress of the other roadway, especially the compressive stress concentration on the side closer to the neighboring roadway. However, when the distance between the two roadways is significantly larger than the roadway size, this effect is not pronounced. In the engineering case studied in this research, the thickness of the pillar is approximately linearly positively correlated with the safety factor of the pillar approximately linearly negatively correlated with the recovery rate. Overall, this research explored the application of the complex variable function theory in an underground mine design, demonstrating its accuracy and practicality.

Development of a mixed reality assisted escape system for underground mine- based on the mine water-inrush accident background

The underground mine is an essential infrastructure for national resources and economy, and its safety system is an important issue, especially the miners’ safety. They should not only enhance their preventive awareness of disasters but also enhance their response capability. When miners are in danger with invalid escape lighting, it is difficult for them to overcome panic. Therefore, the automatic assisted escape system has a particular engineering significance in underground space. This study attempts to develop a reference technical framework for emergency evacuation of underground space workers. A human-environment-computer interaction system is developed, which combines the A*-3D Time algorithm with mixed reality (MR) technology. It is constrained by the spatial geometric information of the mine and the escape time. Firstly, the target mine’s geographic information and spatial structure are surveyed on the field, and a 3D digital model is built by the 3DMine; the BIM is used to integrate 3DMine information (data and material) and design the spatial structure. Secondly, based on the A* algorithm in 3D space, the escape time is introduced to evaluate the escape capability and construct the A*-3D Time model. Thirdly, the timeliness of mine water-inrush scenario is simulated by the Comsol; the interaction method and navigation map are developed by the OpenXR and MR Toolkit (MRTK) in Game Engine; the A*-3D Time model is introduced into the C# script and assigned to the digital objects (Mine and Miners). Finally, the performance of this system is analyzed based on the underground metal mine. Based on game thinking to solve safety problems can be used as a reference for underground space engineering.

Efficient and accurate mapping method of underground metal mines using mobile mining equipment and solid-state lidar

Aiming at the problems of difficult sampling of environmental data, low efficiency, and accuracy of mapping in underground metal mines, this research uses remote control mobile mining equipment, solid-state lidar, and IMU as the hardware system to build an efficient mapping system for underground metal mines.A voxel grid-based point cloud processing method for solid-state lidar is proposed, which can extract planar features and segment ground point clouds more efficiently.An improved point-to-planematching method is proposed, which can improve the matching efficiency and obtain more accurate matching results. The ground point cloud isaddedto the sliding window optimization as a constraint, which overcomes the problem of large vertical error in the process of drawing. Through multiple sets of experiments and comparisons with multiple methods, the results show that the errors, verticaldrifts,and mapping efficiency of the proposed method are the best among the above methods.

Quantitative evaluation of carbon emissions with mining technology development: a case study of an iron mine in China.

To quantitatively evaluate the carbon emission effects of various underground mining schemes in metal mines, a carbon emission calculation model specifically for underground metal mines was established. The carbon emissions stemming from the mine's production process were categorized into three components: carbon emissions from the production of consumed materials, fuel, and electricity; carbon emissions resulting from fuel combustion and explosive explosions, and the reduction of CO2 absorption due to the occupation of the surface industrial site. Subsequently, the carbon emission impact of underground metal mines was assessed using an example from an iron mine in Anhui Province, China. The results showed: (1) Among the underground mining processes, electricity consumption emerged as the primary source of carbon emissions. This underscores the potential for significant carbon emission reduction through the implementation of innovative electric power technologies in underground metal mines. (2) Mining methods with higher productivity showed clear advantages. They not only contribute to the reduction of carbon emissions per kiloton of ore from multiple perspectives but also led to a shorter mine lifespan and decreased CO2 absorption by woodlands occupied by the surface industrial site. Furthermore, these methods resulted in lower carbon emissions throughout the mine's lifespan. (3) Backfill mining proved to be effective in curbing tailings emissions and reducing the required area for a tailings pond. Consequently, this approach minimizes the CO2 absorption by woodlands occupied by the tailings pond.

Stability analysis of crown pillar under the zone of relaxation around sub-level open stopes using numerical modelling

The stability of stopes and pillars is a critical concern in deep underground metal mining due to the potential for stress concentration and relaxation that can cause the dynamic failure of pillars. This study employs a finite element approach to investigate the behaviour of crown pillars to various stress and geo-mining parameters. The analysis includes examining stresses, deformations, and yielding zones around the crown pillars using variations in rock mass parameters. The study involves 240 non-linear numerical models with the Mohr–Coulomb elastoplastic failure criteria under plane strain conditions. The results indicate that increasing the crown pillar thickness from 5 to 8 m reduces maximum vertical deformation by 55.8% and the maximum extent of yielding zones from 2.2 to 0 m. The study suggests a 6 m crown pillar for depths up to 670.56 m and thicker pillars of 7 m or more for greater depths.

Intelligent Safety Risk Analysis and Decision-Making System for Underground Metal Mines Based on Big Data

In view of the new situation faced by safety risk management in underground metal mines, based on a comprehensive analysis of the current situation of mine safety management business and system construction requirements, the main functional modules, overall architecture, and data interaction mode of the intelligent safety risk analysis and decision-making system were analyzed and designed. On the basis of elaborating the implementation process of the main functional modules of the system, such as multi-source safety information collection and governance, and safety risk intelligence analysis and visualization, a safety risk intelligence analysis and decision-making system was constructed, which provided efficient and real-time intelligent application and analysis services for safety in the production of underground metal mines and realized the whole process information management of collection, aggregation, processing, analysis, and visual display of multi-source mine safety risk information. The application of the system has made an essential change in the mode of mine safety risk management, realizing the active safety management goal of shifting safety risk management from post-analysis to pre-prevention, helping to improve the pertinence and efficiency of safety risk management, and greatly reducing the risk of mine safety accidents.

A Dynamic Scheduling Model for Underground Metal Mines under Equipment Failure Conditions

Equipment failure is a common problem in mining operations, resulting in significant delays and reductions in production efficiency. To address this problem, this paper proposes a dynamic scheduling model for underground metal mines under equipment failure conditions. The model aims to minimize the impact of equipment failures on production operations while avoiding extensive equipment changes. A case study of the southeastern mining area of the Chambishi Copper Mine is presented to demonstrate the effectiveness of the proposed model. The initial plan was generated using the multi-equipment task assignment model for the horizontal stripe pre-cut mining method. After equipment breakdown, the proposed model was used to reschedule the initial plan. Then, a comparative analysis was carried out. The results show that the proposed model effectively reduces the impact of equipment failures on production operations and improves overall mining execution at a low management cost. In general, the proposed model can assist schedulers in allocating equipment, coping with the disturbing effects of equipment failure, and improving mine production efficiency.

Relative Importance of Certain Factors Affecting Air Exchange in a High-Altitude Single-Heading Tunnels Based on the Numerical Simulation Method

Single-heading tunnels in underground metal mines have high air pollutant concentrations, chaotic airflow, and low pollutant diffusion efficiency in high-altitude areas, resulting in poor air exchange. Based on Pulang copper mine (China), a computational fluid dynamics case using the steady Reynolds-averaged Navier–Stokes equations with a k-omega turbulence model was developed to study certain factors influencing the air exchange of single-heading tunnels, and was combined with an orthogonal experimental method to simulate the mean age of air (MAA) under different working conditions. This study revealed the ranking of the importance of some factors on the air exchange via sensitivity analysis. The MAA generally increases with the increasing distance between the duct and the heading face and the increasing diameter of the oxygen supply duct. This study’s optimal distance and diameter can reduce MAA by 14.7% and 9.9%, respectively. Placing the oxygen supply duct and the duct on the same side and using an 800/1000 mm inner diameter duct can effectively reduce the MAA by 6.7% and 4.2%, respectively, in this study. The findings of this study can optimize air exchange in the Pulang copper mine, and can also be referenced for the optimization of air exchange in high-altitude highway or railway tunnels being excavated.

Curing conditions effect on pore structure, compressive strength and elastic modulus of cementitious tailings backfills

As a widespread application in underground metal mines, cementitious tailings backfill (CTB) has a significant implication for recycling dangerous process tailings and enhancing the safety of mining voids. The pore structure of CTB that is liable on the features and proportions of tailings and binders is correlated to its mechanical characteristics (i.e., elastic modulus, uniaxial compressive strength). This study deals with the influence of curing conditions such as temperature (20–50 °C), stress (0–540 kPa), and time (3–28 days) on mechanical and pore structure characteristics of CTB. Fill samples were prepared in a stable solid dosage and cement/water ratio of 76% and 1/6, respectively, and put into cylindrical molds (D × H: 50 × 100 mm). A new lab instrument with adjustable curing conditions was adopted for fills. A PC-controlled mechanical press and Hg intrusion porosimetry were applied to assess CTB's strength and pore structure properties. Results suggest that, with advancing curing temperature/stress, the strength and elastic modulus of CTB show a rising trend, while its growth rates show a falling trend. CTB's porosity shows a declining trend, and it exists a good linear correlation between fill's strength and apparent porosity. CTB's strength essentially depends on the volume of medium (1–10 μm) and micro (0.01–1 μm) pores. As a result, several practical equations for CTB specimens are established, which consider types of tailings and admixtures.