Underground Coal Mines Research Articles

Genotoxicity and Cytotoxicity Induced In Vitro by Airborne Particulate Matter (PM2.5) from an Open-Cast Coal Mining Area

This study evaluates the cytotoxic and genotoxic effects of PM2.5 collected from an open-cast coal mining area in northern Colombia. Cyclohexane (CH), dichloromethane (DCM), and acetone (ACE) extracts were obtained using Soxhlet extraction to isolate compounds of different polarities. Human lymphocytes were exposed to the extracted compounds, and cytotoxicity and genotoxicity were assessed using the cytokinesis block micronucleus (CBMN) and comet assays, incorporating FPG and ENDO III enzymes to detect oxidative DNA damage. Chemical analysis revealed that the organic fractions consisted mainly of modified hydrocarbons and volatile organic compounds. The CBMN assay showed a significant increase in micronuclei in binucleated (MNBN) and mononucleated (MNMONO) cells and nucleoplasmic bridges (NPB) in exposed lymphocytes. The comet assay revealed substantial oxidative DNA damage, particularly with the ACE extract, which significantly increased oxidized purines and pyrimidines. DCM induced similar effects, while CH showed moderate effects. CREST immunostaining revealed aneugenic activity, particularly in cells exposed to ACE and DCM extracts. These results suggest that polar fractions of PM2.5, likely containing metals and modified PAHs, contribute to DNA damage and chromosomal instability. The study highlights the need to monitor the composition of PM2.5 in mining regions to implement stricter environmental policies to reduce exposure and health risks.

Mechanistic and Kinetic Analysis of Complete Methane Oxidation on a Practical PtPd/Al2O3 Catalyst

A PtPd/Al2O3 catalyst developed for the complete oxidation of methane from the ventilation air of underground coal mines is compared against a model PdO/Al2O3 catalyst. Although the PtPd/Al2O3 catalyst is substantially more active and stable than the model catalyst, the nature of active sites between the two catalysts is deemed to be fundamentally the same based on their response to different feed gas compositions and the evolution of surface CO adsorption complexes during time-resolved CO adsorption DRIFTS experiment. For both catalysts, coordinatively unsaturated Pd sites are considered the active centers for methane activation and the subsequent oxidation reaction. H2O competes with CH4 for the same active sites, resulting in severe inhibition. Additionally, the CH4 oxidation reaction also causes self-inhibition. Taking both inhibition effects into consideration, a relatively simple kinetic model is developed. The model provides a good fit of the 72 sets of kinetic data collected on the PtPd/Al2O3 catalyst under practically relevant reaction conditions with CH4 concentration in the range of 0.05–0.4%, H2O concentration of 1.0–5.0%, and reaction temperatures of 450–700 °C. Kinetic parameters based on the model suggest that the CH4 activation energy on the PtPd/Al2O3 catalyst is 96.7 kJ/mol, and the H2O adsorption energy is −31.0 kJ/mol. Both values are consistent with the parameters reported in the literature. The model can be used to develop catalyst sizing guidelines and be incorporated into the control algorithm of the catalytic system.

Assessment of Sub-micrometer-Sized Particles with Practical Activities in an Underground Coal Mine

Assessment of Sub-micrometer-Sized Particles with Practical Activities in an Underground Coal Mine

Experimental Investigations on Repair and Permeability Reduction for Single Sandstone Fracture Using a Mixed CaCO3 and Fe(OH)3 Precipitate

In China, groundwater loss caused by underground coal mining is becoming increasingly serious. The key to groundwater restoration is to repair mining-induced water-conducting fractures (WCFs) in the overlying strata. In this study, the adsorption–consolidation sealing characteristics of chemical precipitates were used to conduct permeability reduction (PR) experiments, including adding mixed CaCO3 and Fe(OH)3 to a sandstone specimen with a single fracture at room temperature. An aqueous solution of Na2CO3 was used as the simulated groundwater, and a solution of mixed CaCl2 and FeCl2 was used as the repair reagent to simulate the water seepage conditions of a fractured rock mass. The two aqueous solutions were simultaneously injected into a single-fractured rock specimen at a constant flow rate. The experimental results show that the Fe(OH)3 colloid encapsulated CaCO3 crystals in a mixed precipitate, reducing the overall structural stability of the mixed precipitate and restricting repair and PR efficiency. However, the Fe(OH)3 precipitate had better PR efficiency in the initial stage of the experiment. Therefore, a better scheme was put forward to repair the WCF, utilizing a mixed Fe(OH)3 and CaCO3 precipitate with a molar ratio close to 1:4 in the early stage and a single CaCO3 precipitate in the later stage.

Controlling large deformations in soft rock roadways with integrated anchor shotcrete and grouting techniques

Effective and safe support in soft rock roadways remains a critical challenge in underground coal mining due to the extreme weakness of the rocks and their susceptibility to weathering and water invasion. This paper examines the tailgate of longwall panel 2606, a typical soft rock roadway excavated along the edges of mined-out areas with thin pillars at the Lvtang Coal Mine in Guizhou, China. Despite employing a combination of rock bolts, cable bolts, and surface support systems, significant roadway deformation was observed. The mechanisms behind this deformation were analyzed through in-situ tests and clay mineral composition analysis. These analyses revealed that the primary causes of the roadway’s substantial deformation were the low strength and weathering susceptibility of the coal and surrounding rock. A novel synergistic control strategy combining anchoring, shotcreting, and grouting was proposed for supporting soft rock roadways. Detailed numerical simulations were conducted to evaluate the deformation and stability of the tailgate under various support scenarios, validating the effectiveness of the proposed support scheme. The synergistic support strategy was implemented to reinforce the 2606 tailgate, and field monitoring was conducted to assess its effectiveness. Monitoring data indicated that rib deformation with the new support design was reduced by 66% compared to the original design. The results demonstrate that the improved synergistic support system effectively mitigated large deformations and maintained the stability of the tailgate. These findings provide a valuable engineering reference for supporting and reinforcing soft rock roadways under similar geological conditions.

The Influence of the Key Characteristics of Overburden Rock Structure on the Development Height of Water-Conducting Fracture in Yushenfu Coal Mine Area, China

The destruction of shallow aquifers by water-conducting fractures of overlying strata caused by underground coal mining is the most representative form of mining-induced damage in the Yushenfu mining area. It has become an important factor restricting the green mining of coal in the Yushenfu mining area and even the ecological protection and high-quality development of the middle reaches of the Yellow River. As the key scientific problem of water-preserved coal mining, the scientific understanding of the development law and main influencing factors of water-conducting fractures in overlying strata has attracted great attention. Taking the geological occurrence characteristics of the main coal seam in Yushenfu mining area as the prototype, 24 different types of numerical models are constructed with the key characteristics of the overburden structure, such as the number of layers of sandstone in the overburden (sand layer coefficient) and the thickness ratio of sandstone and mudstone in the overburden (sand–mud ratio), as the main variables. By means of numerical simulation experiment and theoretical calculation, combined with field measurement and comparison, the influence of the key characteristics of overburden structure on the development height of water-conducting fracture is studied and revealed. It is proposed that the effective area for the study area to achieve water-preserved coal mining by using the height-limited mining method must conform to the coal seam overburden structure characteristics of “sand–mud ratio 6:4 and sand layer coefficient less than 70%” and “sand–mud ratio 8:2 and sand layer coefficient less than 80%”. The results not only enrich and deepen the research on the influence of geological factors and the law of controlling the development of water-flowing fractures in overlying strata, but also provide theoretical support for the precise protection of groundwater resources in the Yushenfu mining area in the middle reaches of the Yellow River.

Feasibility Study on the Construction of Underground Reservoirs in Coal Goaf—A Case Study from Buertai Coal Mine, China

The construction of underground reservoirs in coal goaf is a new technology aimed to realize the sustainable development of coal mining-water storage-surface ecology in arid areas of northwest China. The key to the feasibility of this technology is that underground coal mining cannot affect the near-surface aquifer, and the amount of water entering the underground reservoir must meet the needs of the coal mine. Taking Buertai Coal Mine, one of the largest underground coal mines in the world, as an example, this article used similar simulation, numerical simulation and in-situ test methods to study the height of the water-conducting fracture zone of overlying strata and water inflow of underground reservoirs. The results show that, under the repeated mining of the 22- and 42-coal seams, the maximum height of the water-conducting fracture zone is 178 m, and the distance between the near-surface aquifer and the 42 coal is about 240 m, so the mining has little effect on the near-surface aquifer. During the mining period of the 22-coal seam, the groundwater of the Zhidan and Zhiluo Formations was mainly discharged vertically, while the groundwater of the Yanan Formation was mainly a horizontal flow during the period of the 42-coal mining. In this way, the total water inflow of Buertai Coal Mine reaches 500 m3/h, which not only meets the needs of the mine, but also, the rest of the water can irrigate about 98 hectares of farmland nearby. Underground reservoirs in coal goaf could achieve sustainable development of coal mining, groundwater storage and surface ecology in semi-arid areas.

Application of Modern Machine Diagnostic Systems to Improve Safety in the Underground Mining Process

Abstract Currently used machine diagnostic systems are based on very modern solutions based on the acquisition and recording of their operating parameters in real time. Increasingly available and high-tech sensor systems mean that the number of recorded parameters is increasing and their quality is improving. These data are mainly used to assess the technical condition of machines and the processes they perform. In mining, these data can also be used to assess and, at a later stage, improve the safety of the underground mining process. Referring to this issue, the paper presents examples of the use of diagnostic systems for powered roof supports and longwall shearers to assess the safety status of the underground hard coal mining process. In the case of the wall support, the focus was on measuring the pressures in the stands of its individual sections. Temporary changes in the values of these pressures constitute a valuable source of information regarding the interaction of the support with the rock mass. In particular, this concerns the identification of the effects of the informational impact of the rock mass on the longwall excavation protected by the support. The research results presented in the paper, especially in the case of very dangerous dynamic impacts, indicate the possibility of both diagnosing the operating condition of the section and identifying symptoms of exposure to such events. This undoubtedly significantly expands the possibilities of using the measured pressures. Diagnostic signals from a longwall shearer are also widely used. The current intensities drawn by its motors while cutting the rock mass, as well as the advance speed and its position in the wall make it possible to analyze these parameters and their changes before, during and after the occurrence of various types of events. These data enable the assessment of the effects of the rock mass on its operational efficiency and safety status. It also enables the identification of symptoms that precede the occurrence of such events. The presented examples indicate the need for a broader and more holistic approach to the use of diagnostic parameters of mining machines. In particular, this concerns the study of the cooperation between the support and the rock mass and its influence on the efficiency and safety of the rock mass mining process. The subject matter addressed relates to very important and current issues, and the developed methodology and obtained results should be applied in practice as soon as possible.

Deformation and Fracture Mechanisms of Thick Hard Roofs in Upward Mining Coalfaces: A Mechanical Model and Its Validation

The safety and efficiency of underground coal mining are threatened by thick hard roofs characterized by large overhang areas, problematic spontaneous caving, and high dynamic load upon their breakage. In this study, a mechanical model of the bearing capacity of thick hard roofs in upward mining coalfaces associated with mining activities is built based on bending theories for beams with single generalized displacement and the elastic foundation beam theory. Using this method, we analyze the deformation and fracture mechanisms of a thick hard roof during upward mining. We further derive the mechanical equations of rotational angle, bending moment, shear force, and deflection of the free overhang and coal-bearing zone in the thick hard roof and an equation for calculating the limiting span. The mechanical behaviors of the thick hard roof bearing state are analyzed under different parameters. The results show that the foundation coefficient, roof thickness, and angle of upward mining have little influence on the roof bending moment but are positively correlated to the limiting span. Roof load and overhang length have a significant influence on the roof bending moment. They are negatively and positively correlated with the limiting span, respectively. Finally, a case study is performed on the Ш601 upward mining coalface in the Zhuzhuang Coal Mine. The distribution characteristics of the bending moment of the thick hard roof at different extraction stages are analyzed. At each stage, the limiting spans of the thick hard roof upon breaking were calculated as 13.18, 18.82, and 22.50 m, respectively, being close to the on-site measured periodic weighting lengths of 13.33, 19.33 m, and 22.67 m. This close fit proves the feasibility and accuracy of the developed mechanical model. The present study offers theoretical guidance for estimating the weighting length of thick hard roofs in coalfaces and for engineering technology control in similar scenarios.

IoT-Enabled Methane Monitoring and LSTM-Based Forecasting System for Enhanced Safety in Underground Coal Mining

IoT-Enabled Methane Monitoring and LSTM-Based Forecasting System for Enhanced Safety in Underground Coal Mining

Coal Mine Dust Size Distributions, Chemical Compositions, and Source Apportionment

Current regulations mandate the monitoring of respirable coal mine dust (RCMD) mass and crystalline silica in underground coal mines to safeguard miner health. However, other RCMD characteristics, such as particle size and chemical composition, may also influence health outcomes. This study collected RCMD samples from two underground coal mines and performed detailed chemical speciation. Source apportionment was used to estimate RCMD and silica contributions from various sources, including intake air, fire suppression limestone dust, coal dust, diesel engine exhaust, and rock strata. The mine dust mass-based size distributions were comparable to those recorded over a decade ago, with a peak around 10 μm and the majority of the mass in the supermicron size range. The current mine conditions and mining practices do not appear to have significantly increased the generation of smaller particles. Limestone rock dust was prevalent in many locations and, along with coal dust, was the main contributor to RCMD at high-concentration locations. Silica accounted for over 10% of RCMD mass at several active mining locations, primarily from limestone and rock strata dust. Reducing the concentration of limestone dust and its silica content could reduce RCMD and silica levels. Further cleaning of the intake air could also improve the overall mine air quality.

Preparation and performance study of low heat storage flame retardant polyurethane for coal mines

In order to meet the requirements for the use of polyurethane for reinforcement in mines, the synthesis temperature of polyurethane needs to be lowered, and the flame-retardant and mechanical properties of polyurethane should also be considered comprehensively. Factors affecting the synthesis temperature of polyurethanes are investigated, low heat storage polyurethanes that meet the temperature requirements for use in plugging crushed coal bodies in coal mines are formulated, and the synthesized polyurethanes are characterised for their flame retardant properties by FTIR, SEM, TG-FTIR and CONE experiments. It was found that in this paper, a new type of polyurethane for coal mines was formed by flame retardant modification of polyurethane by adding nano-system flame retardant and phosphorus-system flame retardant, and the synthetic reaction temperature of the material could reach as low as 51.2 °C, and the pyrolysis onset temperature was increased to 286 °C. The experimental results show that the flame retardant property of this synthetic polyurethane has been significantly improved, and the heat accumulation effect of the synthesis process on the surrounding coal body has been greatly reduced. The physical properties and thermal stability of this synthetic polyurethane in the grouting process meet the safety requirements for use in underground coal mines.

An investigative and simulative study on the wetting mechanism of alkaline dust suppressant acting on long-flame coal

In order to tackle the issue of excessive coal dust and hydrogen sulfide (H2S) concurrently in underground coal mines, an alkaline dust suppressant was formulated by combining surfactant sodium sec-alkyl sulfonate (SAS60) and sodium carbonate (Na2CO3) at a certain mass ratio, meant for injection into coal seams. This study principally targeted long-flame coal extracted from Hequ County, located in Shanxi Province, China. The objective was to investigate and analyze the underlying process of how alkaline dust suppressants affect the wettability of coal. A comprehensive strategy including contact angle determination, Fourier transform infrared absorption spectrometer(FTIR) analysis, low-temperature nitrogen adsorption tests, scanning electron microscope(SEM) experimental studies, and molecular dynamics simulations was employed for this examination. The results revealed that merging Na2CO3 with SAS60 could reduce the coal’s contact angle. Despite the core structure of the coal surface staying unchanged after alkaline dust suppressant treatment, a rise in the number of hydrophilic functional groups was observed. This count notably surpassed the amount of hydrophobic functional groups, consequently boosting the coal’s hydrophilicity. The permeability of the examined coal specimens was chiefly affected by the existence of macropores and mesopores. Processing with 0.05 wt% SAS60 and 1.0 wt% Na2CO3, the coal acquired additional pores and cracks, causing an upswing of average pore size by 25.79% and a 30.64% increase in the maximum gas adsorption. This facilitated more straightforward infiltration of water into the coal dust. Molecular dynamics simulation outcomes indicated a closer affiliation between coal and water following the incorporation of Na2CO3. It led to a heightened activity in water molecule movement, fortifying intermolecular electrostatic interactions, and fostering the creation of hydrogen bonds. Consequently, this improved the coal’s wettability. The increase in the mass fraction of Na2CO3 directly corresponds to a more considerable enhancement in the solution’s ability to wet the coal. The outcomes of the molecular dynamics simulation validated the experimental results’ precision.

Measurement of sulfur content in coal mining areas by using field-remote sensing data and an integrated deep learning model

High-quality coal emits a smaller amount of harmful substances during the combustion process, which greatly reduces the environmental hazard. The sulfur content of coal is one of the important indicators that determine coal quality. The world’s demand for high-quality coal is increasing. This is challenging for the coal mining industry. Therefore, how to quickly determine the sulfur content of coal in coal mining areas has always been a research difficulty. This study is the first to map the distribution of sulfur content in opencast coal mines using field-remote sensing data, and propose a novel method for evaluating coal mine composition. We collected remote sensing, field visible and near-infrared (Vis-NIR) spectroscopy data and built analytical models based on a tiny neural network based on the convolutional neural network. The experimental results show that the proposed method can effectively analyze the coal sulfur content. The coal recognition accuracy is 99.65%, the root-mean-square error is 0.073 and the R is 0.87, and is better than support vector machines and partial least squares methods. Compared with traditional methods, the proposed method shows many advantages and superior performance.

A new frequency domain denoising method for coal mine transient electromagnetic measuring data

Abstract Due to limitation of space in mine tunnel, only a 2 m × 2 m rectangle coil can be employed to collect the electromagnetic signals for the mine transient electromagnetic analysis. Hence, a small emission magnetic moment and weak detection signal strength will increase the electromagnetic analysis difficulty. Moreover, the transient electromagnetic response signal in mines exhibits exponential decay over time, with late-stage amplitudes being notably small, which makes these signals susceptible to noise interference. As a result, it is necessary to study effective noise removal methods to enhance the signal-to-noise ratio of the late-stage electromagnetic data. Addressing this challenge task, this study proposes a new method for frequency domain denoising of transient electromagnetic data. This new method utilizes the Fourier Transform to convert the original transient electromagnetic data from the time domain to the frequency domain, and then, the noise is identified and removed through the frequency characters. Lastly, the processed frequency domain information is transformed to the time domain by the Fourier Inverse Transform to restore the time domain signals. The effect of this frequency domain denoising method is demonstrated through numerical simulations and underground coal mine field data to show significant noise reduction performance on the abnormality detection in the underground coal mine.

Coal mining activities driving the changes in bacterial community

The mechanism of the difference in bacterial community composition caused by environmental factors in the underground coal mine is unclear. In order to reveal the influence of coal mining activities on the characteristics of bacterial community structure in coal seam, 16S rRNA gene amplicon sequencing technology was used to determine the species abundance, biodiversity, and gene abundance of bacterial community in a coal mine in Shanxi Province, and the environmental factors such as metal elements, non-metal elements, pH value, and gas concentration of coal samples were determined. The results showed that environmental factors and bacterial communities had obvious regional characteristics. Mining activities greatly affected the α diversity of bacterial communities, mining working face > main airway > roadway roof > unexposed coal seam > tunneling roadway. The bacterial community composition of each sample point is also very different. The main airway, roadway roof, and unexposed coal seam are dominated by Actinobacteria while the mining working face and tunneling roadway are dominated by Proteobacteria. Among the gene abundances of metabolic pathways in each site, Citrate cycle had the greatest difference, followed by glycine, serine and threonine metabolism, and oxidative phosphorylation and methane metabolism had little difference. RDA analysis showed that the environmental factors affecting the bacterial community were mainly cadmium, oxygen, hydrogen, and gas content. CCA analysis divided the bacterial community into three categories. Degradation functional bacteria are located in mining working face, bacteria that tolerate poor environments are located in main airway and tunneling roadway, and human pathogens are mostly located in roadway roof and unexposed coal seam. The research results would provide support for realizing green and safe mining in coal mines.

Study on the Identification Method of Planar Geological Structures in Coal Mines Using Ground-Penetrating Radar

The underground detection environment in coal mines is complex, with numerous interference sources. Traditional ground-penetrating radar (GPR) methods suffer from limited detection range, high noise levels, and weak deep signals, making it extremely difficult to accurately identify geological structures without stable feature feedback. During research, it was found that the detection energy of the same target significantly changes with the antenna direction. Based on this phenomenon, this paper proposes a geological radar advanced detection method using spatial scanning. This method overcomes constraints imposed by the underground coal mine environment on detection equipment, enhancing both detection range and accuracy compared to traditional approaches. Experiments using this method revealed pea-shaped response characteristics of planar geological structures in radar images, and the mechanisms behind their formation were analyzed. Additionally, this paper studied the changes in response characteristics under changes in target inclination, providing a basis for understanding the spatial distribution of geological structures. Finally, application experiments in underground coal mine environments explored the practical potential of this method. Results indicate that, compared to drilling data, this method achieves identification accuracies of 91.88%, 90.42%, and 78.72% for the depth and spatial extent of geological structures, providing effective technical support for coal mining operations.

Enhancing gas drainage and ventilation efficiency in underground coal mines: A hybrid expert decision approach for booster fan prioritization

Expanding mining operations in goaf zones heightens gas production potential, posing challenges in maintaining adequate ventilation within development panels, consequently impacting coal production. Various strategies have been explored to enhance mine ventilation and gas drainage effectiveness. However, deficiencies persist in the proposed ventilation system for the Okaba underground coal mine, prompting this study’s necessity. Addressing these concerns, the study evaluates the feasibility of employing booster fans to mitigate the identified drawbacks. Prioritizing booster fans for airflow distribution in underground mines is a complex decision-making process, requiring an advanced expert system approach. To address this, the study proposes an intuitionistic-based fuzzy TOPSIS (IFT) method for booster fan prioritization in the Okaba mine. Results indicate that booster fan 4 (BF4) ranks highest, followed by booster fan 3 (BF3), consistent with fuzzy TOPSIS findings. Sensitivity analysis supports the predicted importance order, affirming the efficacy of the hybrid expert decision method in selecting a booster fan capable of enhancing the overall efficiency of gas drainage and ventilation systems in underground mines. This study introduces a Hybrid Expert Decision Approach that integrates IFT and traditional fuzzy TOPSIS methodologies. This hybrid approach is particularly novel because it combines the strengths of both methods to prioritize booster fans in underground coal mines.

Application and Prospect of Strapdown Inertial Navigation System in Coal Mining Equipment.

In recent years, with the rapid construction of a safe, clean, efficient and sustainable modern energy system, the intelligence of coal mining has become the inevitable direction of the development of the coal mining industry. The intelligence of coal mining system and equipment is the core of intelligent mining, and the positioning technology of mining equipment is the key to underground intelligent mining. The strapdown inertial navigation system can make up for the shortcomings of traditional GPS positioning systems and laser positioning because of its strong anti-interference, high precision and real-time monitoring, and ability to carry out real-time dynamic positioning of mining equipment in underground coal mines. This paper briefly introduces the basic principle of the strapdown inertial navigation system, analyzes the application of the existing strapdown inertial navigation system in mining equipment, and lists and analyzes the research status of the improvement strategy of the inertial navigation system, such as zero speed correction and integrated navigation technology. Finally, by analyzing the application and future development trend of inertial navigation systems in mining equipment, this paper provides more data and method support for the positioning of mining equipment in the future.

Reduction of production delay cost in underground coal mines: An FMEA-based method study approach

Coal is the backbone of the Indian economy, essential for electricity, steel, cement, and other vital items. Although India aims to be carbon emission-free by 2070, it must rely on coal for a few more decades. In the fiscal year 2021–22, India produced 96 percent of its coal from open-cast (OC) mines, whereas 70 percent of India's total coal reserve is in deep undergrounds. Despite underground (UG) coal mining being eco-friendly and yielding richer coal, its production cost is nearly four times higher than OC mining. Therefore, further research on UG mines is necessary to address these challenges. This study analyzed an underground coal mine production system in India and identified production delays as a major cost driver. Causes of delays were categorized by their association with machine, material, and man. An innovative technique, the Machine Criticality Score (MCS), has been developed to quantify production delay costs and guide management in mitigating them. Additional methods like failure mode and effects analysis (FMEA), standard operating procedure (SOP), inventory management tools, and method study were also used in this study to reduce production delay costs.