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The article provides a historical account of the struggle of mine workers in the U.S. in the Civil War era. Information is provided on the union organized by immigrant Illinois coal miners and their manifesto that called for emancipation of labor, the miners' marching strike following a pay cut, expansion of the miners union and the growing control of Belleville track operators of the coal market, and the collective counteroffensive of Illinois mine operators against the union.

Coal gangues i a solid waste during the coal mining process and the accumulation of coal gangue will harm the environment. Therefore, solid waste utilization of coal gangue is required to reduce the environmental damage. In this paper, cordierite ceramics are successfully prepared via a solid‐phase sintering using coal gangue, Al2O3, and MgO as raw materials. The effects of sintering temperatures on the microstructures, phase stability, and thermal properties of ceramics are investigated. The results show that the properties of cordierites prepared at 1200°C are close to those of prepared by the traditional method, and the synthesized ceramics have thermal expansion coefficients (TECs) and conductivity of 4.1–10−6 K−1 and 1.72 W·m−1 K−1 at 900°C, respectively. The sample prepared at 1200°C has good wear resistance (η) with a wear resistance coefficient of 0.507, and an excellent thermal shock resistance, which can withstand 15 times of cold and hot shocks at 1100°C without any cracks on the surface. This study systematically elucidates the thermal/mechanical properties of the synthesized cordierite, and the feasibility of using coal gangue as raw materials prepared cordierite ceramics as refractory materials. This work presents an effective solution to mitigate the challenge of coal gangue disposal. [ABSTRACT FROM AUTHOR]

ABSTRACT During the mining process, repetitive stress disturbances induced by mining activities can lead to alterations in the physical properties of coal, potentially resulting in rockburst occurrences within tunnels. To investigate the propagation rule of physical field characteristics and characteristics of failure in roadway surrounding rock under multiple disturbance damage caused by dynamic load, a combined experimental and theoretical analysis is conducted to study the weakening effect of rock mass under various disturbance circumstances. A model of roadway surrounding rock loosening and failure under multiple disturbances was proposed. The degree of damage is quantified by defining the weakening coefficient Di, A “weakening variable method” is proposed to confirm the main parameters of the Holmquist‐John‐son‐Cook (HJC) model under different disturbance conditions. The reliability of these findings was validated through a microseismic event at the Tangshan coal mine's 0250 working face in 2020, followed by numerical simulation studies. The results indicate that damaged coal weakens the intensity of stress waves at the same source velocity, with the strongest effect observed at interfaces between different damage zones. Furthermore, damaged coal exhibits a stronger weakening effect on stress wave propagation speed compared to undamaged coal in non‐interface areas. The study on roadway stability reveals that severely damaged coal‐rock samples significantly weaken stress waves; however, they also exhibit lower minimum energy for dynamic failure in roadway surrounding rock, indicating that low‐stress waves cause greater damage under severe damage conditions. The study investigates the impact of coal rock mass degradation on the stability of surrounding roadways under various disturbance conditions, which holds significant implications for the timely identification of potential instability risks in damaged coal bodies, optimization of support strategies, and ensuring mining safety. [ABSTRACT FROM AUTHOR]

Coal in high-temperature deep mines or igneous intrusion mines is prone to complicated spontaneous combustion in the mining process, because it has occurred in a pyrolysis state for a long time. In order to investigate the effect of initial pyrolysis on coal oxidation, in this study, the coal samples were first pyrolyzed to different temperatures in the nitrogen atmosphere and then oxidized in the dry air atmosphere. Meanwhile, the changes in radical parameters (linewidth of ESR spectra, g factor and radical concentration), CO release and O2 content in the process of changing the states of coal samples from pyrolysis to oxidation at 70°C, 110°C, 150°C and 190°C were determined through experiments. The following conclusions were drawn: When the coal samples change from the pyrolysis state to the oxidation state, their linewidths of ESR spectra increase suddenly, and such an increase is more obvious when the change is made at a lower temperature. The linewidth increases by more than 0.066 mT after the change at a temperature lower than 110°C. Initial pyrolysis promotes the turning point temperature of g factor, and the turning point temperatures of g factor of coal after the gas atmosphere is changed from nitrogen to dry air at 70°C, 110°C, 150°C and 190°C are 160°C, 180°C, 190°C and 200°C, respectively. The growth rate of radical concentration surges after the change from the pyrolysis state to the oxidation state, and the radical concentrations of the coal samples whose states are changed after 150°C grow faster than that of the coal sample oxidized in dry air. When the temperature is lower than 110°C, the CO release under the pyrolysis and oxidation conditions is low, the maximum value being only 105 ppm. At the final temperature of 230°C, when the gas atmosphere is changed from nitrogen to dry air at 70°C, 110°C, 150°C and 190°C, the CO produced by coal is 14,386 ppm, 13220 ppm, 11836 ppm and 10,287 ppm, respectively. The mode of the effect of initial pyrolysis on coal spontaneous combustion was discussed in the end, and the conclusions are of guiding significance for coal spontaneous combustion control. [ABSTRACT FROM AUTHOR]

Levenhall Links, an artificial coastal site in eastern Scotland, is examined in relation to the long history of coal extraction and power generation in Scotland; to the aerial geography of mine workings and underground geography of pits and tunnels; and to the railways, sentiments and politics that connected them. The origins of the site as a discard pile are traced, following the construction and operation of networked infrastructures that included the modernist industrial plants, Cockenzie Power Station and Monktonhall Colliery. Levenhall Links appears as the waste-filled culmination of the Anthropocene, and a window into its uncertain aftermath with new, often fractious, accommodations between humans, water, birds and sediments. [ABSTRACT FROM AUTHOR]

To date, there has been little research on the history of work-related mental health issues among coal workers. Much of the coal extraction industry peaked during the early twentieth century and then began its precipitous decline. Mining has high casualty rates, and the medical field did not understand the long-term effects of psychological trauma on mine workers until recently. Newspaper articles and other historical records provide accounts of accidents and tragedies. Heroism is often emphasized in recalling tragic episodes at the expense of recording the emotional stress suffered by survivors. A diverse set of historical sources provides a context for work-related mental health issues in the coal extraction industry. Probing a set of historic oral histories of coal workers and creating analogies to current studies provide additional clues about the under-told story of these historic actors’ general health and well-being. While incorporating oral histories from other regions, focusing on the anthracite coal industry in northeastern Pennsylvania allows us to identify historical actors and helps us think differently about other working-class communities impacted by industrial capitalism. [ABSTRACT FROM AUTHOR]

To ensure that the discrete element model of the coal wall accurately reflects the actual cutting process of coal and rock during virtual prototype simulation of mining equipment, this study aims to expedite the development of intelligent mining machinery. Using coal samples from the 4602 working face of Yangcun Coal Mine, operated by Yanzhou Coal Mining Group, we conducted coal rock packing experiments and uniaxial compression tests to obtain the packing angle and compressive strength of the coal samples. Based on the experimental results, we designed Plackett–Burman experiments (PB experiments), steepest ascent experiments, and Box-Behnken experiments to study the influence of particle contact mechanics parameters and bonding mechanics parameters on the packing angle and compressive strength, using the packing angle and compressive strength as response variables. Our objective is to minimize the relative error between the simulated packing angle and the measured packing angle. We solved and optimized the parameter calibration model and conducted simulation calibration experiments based on the optimization results. A comparative analysis with the actual test results revealed that the maximum relative errors between the simulated and measured values for the packing angle and compressive strength were only 2.9% and 5.0%, respectively. Additionally, a discrete element model of a typical working face coal wall was established based on the parameters obtained from this calibration method. A bidirectional coupling model of the cutting process between the coal and rock was created using EDEM-RecurDyn to simulate the rigid-flexible coupling of the coal cutter. An experimental coal wall model was constructed based on similarity theory, and both simulation and physical experiments were conducted. The evaluation metrics for comparison were the time-domain and frequency-domain characteristics of the drum's vibration signals. The maximum relative error for the time-domain signal characteristics between the two experimental setups was only 4.19%, while the maximum relative error for the frequency-domain signal characteristics was 3.75%. This validates the feasibility of the proposed calibration method for the discrete element coal wall model and the accuracy of the calibration results. Furthermore, it demonstrates that the constructed discrete element coal wall accurately represents the actual coal and rock properties. The virtual simulation based on this model effectively replicates the interaction process between mining machinery and coal, providing a safe, efficient, and low-cost technological approach for performance analysis of mining equipment and intelligent control of supporting devices. [ABSTRACT FROM AUTHOR]

To study the influence of cyclic disturbance stress on the mechanical behavior of coal during mining, a gas containing coal fluid-solid coupling servo seepage experimental system was used to conduct experimental research on the acoustic emission (AE) characteristics of gas containing coal under two stress paths of graded cyclic loading and unloading. The AE characteristics of coal damage and failure processes under different cyclic stress paths were analyzed. The research results indicate that: (1) The overall characteristics of AE signals for both graded cyclic loading and unloading paths are basically the same. With increasing of the amount of graded cyclic loading or unloading, the AE count reaches its maximum value when reaching failure, and the cumulative ringing calculation of AE increases exponentially. (2) The AE signals under the graded cyclic loading or unloading path exhibit obvious zoning characteristics. In the low and medium stress regions, the AE signal basically satisfies the Kaiser effect, while reaching the high stress region before failure, the AE signal exhibits a significant Felicity effect. (3) The concentration coefficient of AE and the intensity coefficient of the Kaiser effect have been newly defined. They are used to quantitatively characterize the extent of the Kaiser effect of AEs under graded cyclic stress. It was found that as the variation of graded cyclic stress increases, the concentration coefficient and Kaiser effect intensity coefficient both show a decreasing trend. (4) Combining the AF and RA values of AE, it was found that the coal failure signals of the two stress paths were basically similar, that is, the overall failure was mainly tensile failure, and the signals of cyclic unloading tensile failure were significantly more than those of cyclic loading. The AE signal characteristics studied in this article are of great significance for predicting coal power disasters. [ABSTRACT FROM AUTHOR]

To address the problem of fault branch recognition in mine ventilation systems, a one-class classification algorithm is introduced to construct the MC-OCSVM ventilation system fault diagnosis model, which is integrated with multiple OCSVMs. This model adopts uniform hyperparameters and transforms the ventilation system fault diagnosis problem into a maximum decision distance problem, to realize the effective use of mine monitoring wind speed data. The experiments on public KEEL datasets verify that the one-class classification integration model can solve the multiclassification problem and that the MC-OCSVM model has better generalizability than other one-class classification integration models do. The experiment is carried out in the Buertai coal mine, and the results show that the proposed algorithm can identify fault branches quickly and accurately, with an accuracy of 93.2% and a single fault diagnosis time is 1.2 s, highlighting its strong robustness. [ABSTRACT FROM AUTHOR]

In response to the problem of significant deformation and obvious strata pressure in tunnel caused by close‐distance repeated mining, along with difficult control of surrounding rocks, theoretical analysis, and numerical simulation methods were employed to study the asymmetric failure characteristics of tunnels under the influence of close‐distance repeated mining. The research provided insights into the mechanism of asymmetric failure of tunnels affected by close‐distance repeated mining, revealed the impact of residual coal pillars in the upper coal seam on the tunnel in the lower coal seam, analyzed the stress distribution of surrounding rocks before and after tunnel excavation under the influence of repeated mining, and proposed asymmetric surrounding rock control techniques for tunnels affected by close‐distance repeated mining. The study results indicate that the protection of coal pillars in the upper coal seam and the adjacent working face mining in the same coal seam are the main reasons for significant stress concentration on one side of the tunnel and the appearance of asymmetric failure characteristics. After tunnel excavation, the stress of surrounding rocks is released into the tunnel, resulting in a significant reduction in stress environment. However, the stress on the left side of the tunnel is significantly higher than that on the right side, showing an asymmetric distribution. The application of active support with anchor net cables and U‐shaped steel frames effectively reduces tunnel deformation, with good on‐site application results. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The mechanism of rock burst induced by the superposition of dynamic and static loads in multicoal seam mining is unique. To investigate the propagation attenuation law of large‐energy microseismic events and the induced mechanism of rock burst under this condition, this study employs FLAC3D's dynamic module to simulate and analyze the influence of propagation distance, overburden structure in multicoal seam mining, and interlayer plastic zone on vibration wave attenuation. Results indicate that when coal seams are mined at close distances, vibration waves experience significant attenuation while passing through the plastic zone between two layers of coal. At equal attenuation distances, multicoal seam mining structures exhibit greater effects on vibration wave attenuation. Considering differences between rock‐burst induction mechanisms in close‐distance coal seam group mining versus single coal seam mining, a discriminant criterion for rock bursts induced by superimposed dynamic and static loads in multicoal seam mining is established along with a monitoring and early warning method suitable for such conditions. [ABSTRACT FROM AUTHOR]

To solve the severe coal dust pollution and dust hazards in underground coal mines, this study utilized graft copolymerization modification technology and compound technology to develop a mining composite consolidation dust suppressant. On this basis, analysis of its consolidation wettability and dust suppression mechanism was conducted through characterization tests and molecular dynamics simulation methods. The results show that polyacrylamide (PAM) had been successfully grafted onto the soybean protein isolate (SPI) molecule, and form a SPI‐PAM complex. After the dust suppressant acted on the coal dust surface, it utilized its wealthy hydrophilic groups, for the adsorption of water molecules and the positive amide group for binding to produce a large area of agglomeration of coal dust particles at the interface, exhibiting good wetting and consolidation into a shell. At the same time, molecular dynamic simulation verified that the diffusivity of water molecules in the dust suppressant‐coal system was 0.30Å2/ps, decreased by 43.3%, and the interaction energy with coal molecules was −200.27 kcal/mol, absolute value increased by 41.35%, which made the dust suppressant molecules more easily adsorb and agglomerate on the surface, demonstrated an excellent solidification and dust suppression effect. [ABSTRACT FROM AUTHOR]

The accurate measurement of coal seam gas content is essential for several aspects of deep coal mining, including disaster management, resource allocation and sustainability. However, obtaining in-situ coal samples while preserving gas content under challenging conditions, such as high stress, temperature fluctuations, and drilling fluid environments, remains a significant challenge. To overcome this difficulty, we present an innovative insitu pressure- and gas-preserved coring tool specifically designed for deep coal mining applications. This device enables the collection of coal seam samples under in-situ conditions while ensuring that both pressure and gas content are preserved, thereby preventing gas escape during sample transfer and providing more accurate parameters for evaluating coal and natural gas reserves. In the demanding environment of deep coal seams, the performance of the pressure-preserved chamber of the corer relies on the reliability of its remote triggering mechanism. The presence of drilling fluid introduces medium resistance, which can impair the triggering process--an issue largely overlooked in previous research. Herein, we propose a robust method to calculate remote triggering forces within liquid media and optimize its key parameters to improve operational stability. Laboratory tests and field validations in coal mining environments are conducted, which confirm the effectiveness of the optimized design and demonstrate the tool's practical applicability. This study offers valuable insights into addressing key challenges in deep coal reservoir exploration and gas resource preservation. [ABSTRACT FROM AUTHOR]

The safe operation of underground reservoirs and environmental protection heavily rely on the water flow through coal pillar dams in coal mines. Meanwhile, research on the flow characteristics in coal pillar dams has been limited due to their low hydraulic conductivity. To address this gap, this study assembled a novel seepage experimental device and conducted a series of carefully designed seepage experiments to examine the characteristics of low‐permeability in coal pillar dams. The experiments aim to explore the relationship between water flux and hydraulic gradient, considering varying core lengths and immersion times. Flow parameters were determined by fitting observed flux‐gradient curves with predictions from both Darcy and non‐Darcian laws. Several significant results were obtained. First, a noticeable non‐linear relationship between water flux and hydraulic gradient was observed, particularly evident at low flow velocities. Second, the non‐Darcy laws effectively interpreted the experimental data, with threshold pressure gradients ranging 13.60 to 58.64 for different core lengths. Third, the study established that water immersion significantly affects the flow characteristics of coal pillar dams, resulting in an increased hydraulic conductivity and flow velocity. These findings carry significant implications for the design of coal pillar dams within underground coal mine reservoirs, providing insights for constructing more stable structures and ensuring environmental protection. [ABSTRACT FROM AUTHOR]

As China enters the stage of deep coal mining, the accidents caused by roof failure pose increasingly serious threats. Current research on roof failure zones often use single methods, but single geophysical data may result in multisolution issues during interpretation. This paper employed similar simulation experiments, exploring the strain failure characteristics and the changes in apparent resistivity caused by stress variations, taking the 11-3106 working face of a mining area as the research object. Through optical fiber strain and apparent resistivity, the locations and degrees of fracture in postmining rock strata were identified. The feasibility of using distributed optical fiber sensing and the parallel electrical method for qualitative and quantitative analysis of mining-induced fractures was verified. The results showed that optical fiber strain increased significantly at the location of rock fracture, with apparent resistivity anomalies rising correspondingly. The peak strain region corresponded well with the region of apparent resistivity anomalies. In a similar simulation with a geometric ratio of 1:100, the height of the caving zone was measured to be 31.65 cm, with a caving-to-mining ratio of 6.33. In the field working face, the caving zone height was 29.47 m, with a caving-to-mining ratio of 6.01, consistent with the actual conditions of the 11-3106 working face. [ABSTRACT FROM AUTHOR]

To investigate the reasonable width of a coal pillar in the downward mining section of close-distance coal seams, the stress state of any point below the residual coal pillar in the overlying goaf and the width of a small coal pillar were studied by theoretical calculation, numerical simulation, similar simulation and field monitoring. The findings indicate that the width range of the small coal pillar is 7.92~11.42 m. The 4-1 coal seam is in the stress reduction zone when it is more than 16.6 m horizontally from the border of the residual coal pillar above it. In addition, the peak stress is situated inside the elastic zone of the coal pillar and is lower than the coal pillar's bearing limit when a small coal pillar of 8 m is maintained. With the help of distributed optical fiber monitoring to model the coal pillars' stress distribution, it is found that 8 m simulated coal pillars have a certain bearing capacity. The practical findings demonstrate that the 8 m small coal pillar that was left on the site satisfies the demand, and the convergence of the roadway's floor and roof, and its two sides fall within the controllable range. The findings of the study offer a reference for the location of a return air roadway and the width of section coal pillars in the downward mining of close-distance coal seams. [ABSTRACT FROM AUTHOR]

Surface mining in the southeastern Gobi Desert has significant environmental impacts, primarily due to the creation of large coal piles that are highly susceptible to aeolian processes. Using spaceborne remote sensing and numerical simulations, we investigated erosional processes and their environmental impacts. Our primary tool was Interferometric Synthetic Aperture Radar (InSAR) data from Sentinel-1 imagery collected between 2017 and 2022. We analyzed these data using phase angle information from the Small Baseline InSAR time series framework. The time series analyses revealed intensive aeolian erosion in the coal piles, represented as thin deformation patterns along the potential pathways of aerodynamic transportation. Further analysis of multispectral data, combined with correlations between wind patterns and trajectory simulations, highlighted the detrimental impact of coal dust on the surrounding environment and the mechanism of aeolian erosion. The lack of mitigation measures, such as water spray, appeared to exacerbate erosion and dust generation. This study demonstrates the feasibility of using publicly available remote sensing data to monitor coal mining activities and their environmental hazards. Our findings contribute to a better understanding of coal dust generation processes in surface mining operations as well as the aeolian erosion mechanism in desert environments. [ABSTRACT FROM AUTHOR]

This study presents the first column-averaged dry-air mole fractions of carbon dioxide (XCO2), methane (XCH4) and carbon monoxide (XCO) in the coal mine aggregation area in Shanxi, China, using two portable Fourier transform infrared spectrometers (EM27/SUNs), in the framework of the Collaborative Carbon Column Observing Network (COCCON). The measurements, collected over two months, were analyzed. Significant daily variations were observed, particularly in XCH4, which highlight the impact of coal mining emissions as a major CH4 source in the region. This study also compares COCCON XCO with measurements from the TROPOspheric Monitoring Instrument (TROPOMI) onboard the Sentinel-5P satellite, revealing good agreement, with a mean bias of 7.15 ± 9.49 ppb. Additionally, comparisons were made between COCCON XCO2 and XCH4 data and analytical data from the Copernicus Atmosphere Monitoring Service (CAMS). The mean biases between COCCON and CAMS were −6.43 ± 1.75 ppm for XCO2 and 15.40 ± 31.60 ppb for XCH4. The findings affirm the stability and accuracy of the COCCON instruments for validating satellite observations and detecting local greenhouse gas sources. Operating COCCON spectrometers in coal mining areas offers valuable insights into emissions from these high-impact sources. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Understanding the effects of abandoned coal mine ecological restoration on soil quality and function is important to protect the regional ecological environment. This study aims to evaluate the ecological restoration effects of soil quality in abandoned coal mine area. Taking Fengcheng County, a typical coal‐rich area in southern China, as a case, this study took 120 soil samples to investigate the influence of restoration years on soil quality by using an integrated soil quality index (SQI). Results indicated that restoration years had significant effects on the saturated hydraulic conductivity (Ks) by affecting the soil bulk density, clay content, and soil water content. Furthermore, clay, soil organic matter, Ks, and pH were selected to assess the effect of ecological restoration years on soil quality. It was found that the ecological restoration 8 years (ER8) site had higher SQI value, indicating ecological restoration years showed a positive correlation with SQI in abandoned coal mine area. Since there was a 4‐year gap between ecological restoration 4 years site and ER8 site, the ecological restoration may be effective between 5 and 8 years. The results of this study are of great significance for improving the effects of ecological restoration and management in abandoned coal mine area. Core Ideas: Soil quality index (SQI) of different ecological restoration years was valued, and ecological restoration in the abandoned coal mine was helpful to improve soil quality.Soil organic matter (SOM), clay content, saturated hydraulic conductivity (Ks), and pH were representative indicators for calculating soil quality index (SQI).SQI was significantly improved with the increase of ecological restoration years.SQI was an effective tool to assess the ecological restoration management practices. Plain Language Summary: Many coal mines close as they reach the end of their viability or in response to policy, which results in the increase of abandoned coal mines. Understanding the effects of abandoned coal mine ecological restoration on soil nutrient condition is vital for environmental protection. In this study, an integrated soil quality index (SQI) was used to evaluate the effect of restoration years on soil quality. Clay, soil organic matter, saturated hydraulic conductivity (Ks), and pH were representative indicators for calculating SQI. SQI was significantly improved with ecological restoration years in abandoned coal mine area. The results of this study are of great significance for improving the effects of ecological restoration and management in abandoned coal mine area. [ABSTRACT FROM AUTHOR]

AbstractThe hydraulic system of the tunneling machine exhibits significant nonlinearity, resulting in increased data measurement costs and reduced the synchronization accuracy of two hydraulic cylinders. The crucial part of the tunneling machine is the cutting mechanism for coal mining, with its hydraulic system primarily comprising the lifting hydraulic system and the rotary hydraulic system. However, the synchronization precision of two hydraulic cylinders greatly impacts the reliability of the lifting and rotary circuits. To reduce data acquisition costs during the operation of the tunneling machine and achieve high synchronization accuracy between hydraulic cylinders, a control method based on an improved extended state observer active disturbance rejection control (ESO-ADRC) is proposed. First, a mathematical model of the valve-controlled hydraulic synchronization system is established, and introduce dead zone compensation in the electro-hydraulic proportional directional valve to improve the response speed of the control system by 0.5–1 sec. Then, improved and traditional extended state observers are integrated into the active disturbance rejection controller. Result indicated that the improved ESO-ADRC system offers better observer tracking speed performance, using displacement and velocity as control objectives, the maximum synchronization error was reduced by 35 and 50%, respectively. Additionally, master–slave control and deviation coupling control methods are applied to the system. The results show that with displacement and velocity as control objectives, the maximum absolute value synchronization error of the hydraulic cylinders in the deviation coupling active disturbance rejection control system was reduced by 66 and 63%, respectively. [ABSTRACT FROM AUTHOR]

A clean and effective unconventional fossil fuel is coalbed methane (CBM). The development of CBM is essential to reducing the lack of oil and gas resources, preventing coal mine gas mishaps, and safeguarding the atmosphere. After the coal samples prepared in this study were frozen and thawed by liquid nitrogen, the change rules of coal surface and internal pores were investigated by metallurgical microscopy and carbon dioxide adsorption. The results showed that: 1) The values of specific surface area, characteristic adsorption energy, and total SF microvolume of coal samples increased after freeze-thawing of liquid nitrogen, but the CO2 adsorption experiments showed that the pore width decreased, which indicated that the mechanism of freeze-thawing fracture effect coal by liquid nitrogen mainly increased the number of micropores in coal. 2) The water saturation of coal samples rose with the degree of surface cracking, but when the water content reached a specific level, the rise in surface porosity of coal reduced with the water saturation. 3) The increase in the number of cycles has a greater effect on the extent of expansion of pores on the coal surface than on the expansion of pores in the coal. [ABSTRACT FROM AUTHOR]

Coal gangue is a bulk industrial solid waste produced in the process of coal mining and washing, with the dual attributes of resourcefulness and hazardousness. It can be used as a reserve resource for valuable critical metals such as aluminum (Al), lithium (Li), gallium (Ga), and rare earth elements (REEs). In this paper, the occurrence modes of Li, Ga, and REEs in coal gangue were studied by sequential chemical extraction method. The extraction of valuable critical metals from the coal gangue was systematically studied by roasting activation-sulfuric acid leaching process, and the activation mechanism was elucidated. The results showed that roasting can destroy the inert kaolinite structure in coal gangue and significantly improve the leaching rate of valuable critical metals. Under the optimum conditions, the leaching rates of Al, Li, Ga, and REEs reached 86.51%, 74.46%, 95.45%, and 77.14%, respectively, and the leaching behaviors of Al, Li, and Ga were highly similar. In addition, the characterization of the leaching residue revealed 83.96% silicon oxide content with a loose and porous surface, which could be used to prepare silicon-based products. This study provides the theoretical basis and technical support for the utilization of valuable metals in coal gangue. [ABSTRACT FROM AUTHOR]

The subsidence caused by coal mining could cause the destruction of roads and houses, and even the failure of infrastructures. Understanding of the mechanism of coal mining subsidence may provide early protecting to infrastructures on coming failure, but dynamic analysis of subsidence due to coal mining is currently needed. In this study we apply particle image velocimetry (PIV) method to reveal strata movement and subsidence according to the prototype and indoor physical model similarity experiment of Henan. Our result shows magnitude of the subsidence of overlying strata during the coal mining at different excavation thickness, that more coal mining thickness may produce more subsidence, and that shallower coal may cause more significant subsidence. Our result suggests that further PIV test combined with field monitoring data may be an effective measure to study subsidence mechanism and pattern helping to predict disaster caused by subsidence. [ABSTRACT FROM AUTHOR]

In response to the frequent occurrence of impact events in isolated coal pillars between the upper (lower) mountain areas of mining areas under conditions without obvious mining disturbance, this study takes multiple isolated coal pillar impact events that occurred in Zhaolou Coal Mine and Gengcun Coal Mine as examples. It conducts a mechanism study on the creep-induced impact ground pressure of isolated coal pillars considering the time effect. The occurrence of such impact ground pressure accidents often exhibits significant "lag" and "spontaneity". Due to the unclear mechanism of occurrence and the difficulty in grasping the unloading timing, this type of impact ground pressure has become a typical hidden disaster, posing a serious threat to the deep mining of coal mines. Based on the analysis of the creep mechanical properties of coal and rock mass, the uniaxial compression acoustic emission creep test of coal body, and the FLAC3D numerical simulation, a creep instability impact mechanical model of coal and rock mass is established. This model reveals the mechanism of creep instability impact and the stress evolution law of coal and rock mass during creep. The mechanical and energy criteria for the occurrence of impact ground pressure in isolated coal pillars under the action of unstable creep are proposed. The study shows that the action of high ground stress is a necessary condition for the occurrence of "lag-type" impact ground pressure in isolated coal pillars. Long-term unstable creep will weaken the support strength of the entry. When the elastic energy accumulated in the isolated coal pillar exceeds its ultimate bearing capacity, impact instability will occur. Based on the mechanism of occurrence of such impact accidents, targeted deep hole blasting unloading measures are proposed, providing a good reference value for the prevention and control of "lag-type" impact ground pressure accidents in isolated coal pillars. [ABSTRACT FROM AUTHOR]

Aiming at the problems of safety production cost caused by the increase of mining face width and pressure mining in Xizhuo Coal Mine in Chenghe Mining area, a mechanical model of floor plastic slip failure is established based on the theory of plastic slip line, and the difference between it and the traditional floor failure model is analyzed. The damaged contour line of the support stress and lateral support stress on the bottom plate through the advancing direction of the working face is the intersection line of a straight line and an arc line. The failure of the floor caused by lateral supporting stress is the failure of the floor again on the basis of the failure of the floor in the advancing direction of the working face, and there is a superimposed failure area. The analysis of the failure form of the stope floor by this mechanical model is closer to the engineering practice. By using "ultrasonic detection method + stress monitoring inverse analysis method," the measured data such as disturbance failure depth and distribution law of large mining width working face were obtained. The test method used in this paper is relatively rare in the monitoring of the depth of floor disturbance failure at home and abroad. Considering that the traditional pressure water test method has disadvantages such as easy collapse hole, long period, and large error in monitoring the failure rule of deep floor rock mass, the embedded stress monitoring and reverse analysis method and ultrasonic detection method are used to successfully collect and real‐time monitor the data of rock floor before, during and after mining in the lower part of wide mining face of Xizhuo Coal Mine for the first time, and several effective data are obtained, which solves the three‐part "spatial‐time" all‐round floor disturbance and failure law field measurement which cannot be realized by traditional testing technology. By comparing the results of theoretical analysis, field measurement, and numerical simulation, the law and depth of floor disturbance failure of a 240‐m wide mining face in the Chenghe mining area are obtained for the first time, which provides scientific guidance for floor water disaster induced by coal seam mining under similar conditions in the future and has an important reference role for the prevention and control of Ordovician ash water disaster in coal mining. It provides important technical parameters for the safe setting of the effective water barrier layer and the selection and timing of the grouting layer of the floor, which can bring considerable economic and social benefits. The research results have important popularization value. [ABSTRACT FROM AUTHOR]

The population loss in mining areas intensifies the imbalance of the development of resource-based cities (RBCs). How to use night-time light to describe the spatial-temporal evolution pattern of population and compare the agglomeration and migration characteristics of population in coal mine concentration area (CMCA) and cities has become an important issue for sustainable development of RBCs. By fitting the DMSP/OLS and NPP/VIIRS night-time lights, this paper completed the simulation of population distribution of Linfen City in 2003/2008/2013/2018 by constructing the population spatialization model, and measured the urban population agglomeration and migration by using the geographical concentration index of population (GCP) and relative population migration index (RPM). The results show that the population agglomeration and migration of CMCA and cities are not synchronized. The GCP of the whole city shows an upward trend, while the GCP of CMCA shows a trend of substantial decrease first and then increase. From 2013 to 2018, the RPM of CMCA rebounded and reached 0.0307, reflecting the alleviation of population loss in CMCA. It is suggested that night-time lights should be used in the dynamic change assessment of population in RBCs, and measures such as coordinated development, acceleration of industrial transformation and promotion of urbanization should be taken to realize the reasonable distribution of population in RBCs. [ABSTRACT FROM AUTHOR]

This is a story of costs of 114 million EUR incurred by stubbornness and unwillingness to cooperate, or, in other words, by sticking to dead ends in discussions where parties disagree strongly enough that they cannot find common ground. This paper proposes an approach to analyzing such cases of disagreement by employing a multidimensional model involving deontic, ontological, and ethical axes. We use an example of the Turów coal mine disputes, which, from March 2020 to February 2022, involved the governments of the Republic of Poland, the Czech Republic, and the European Court of Justice. Our model results in a tree-like structure of the consecutive issues being considered, represented by questions, governed by the dependency between questions and external actions and events related to the dispute. We aim to provide a comprehensive understanding of the dynamics and resolution paths in such complex disagreements. [ABSTRACT FROM AUTHOR]

We evaluated the spatiotemporal evolution of microseismic (MS) sources generated by multiple fracturing of a hard and thick Jurassic rock stratum in the 93upper24 working face of the Nantun coal mine, China. Moment tensor inversion, stress field analysis, velocity tomography, and stress inversion were used to reveal individual rupture types and the failure process of the hard rock stratum in the working face during the mining operation. We simulated the change in Coulomb stress before and after the occurrence of mining-induced tremors, and analyzed its impact on the stability of the surrounding rock close to the working face. Our results demonstrate that the static Coulomb stress change computation is an efficient tool to predict the evolution of subsequent MS events patterns. The outcome of this work allows to identify and better understand the failure mechanism within a hard and thick Jurassic rock stratum during the mining operation, and can be an interesting approach in improving mine safety in similar environments. Highlights Induced microseismic events (evolution of hypocenters, energy, and source types of events) are used to characterize the failure process in a hard–thick Jurassic rock stratum during mining operations. Both the near-field stress evolution during mining (secondary stresses) and the far-field regional stress regime (primary stresses) plays a role in the fracturing and failure process of the Jurassic rock stratum. An interaction mechanism of the 3upperF271 fault instability (tectonic stresses) and the rock mass failure within the working face is identified and quantified via Coulomb stress analysis. [ABSTRACT FROM AUTHOR]

Borehole destressing is one of the most widely used techniques for mitigating coal bursts. Understanding the working principle of destressing boreholes, exploring the main efficiency factors, and proposing a quantitative method for determining the drilling parameters for coal burst control are essential for maximizing coal burst control. This study establishes a unified damage mechanics model of borehole bursts (that is, dynamic collapse in boreholes) and roadway coal bursts, deduces the critical indices of borehole bursts, and identifies the main factors. The theoretical relationship between the critical stresses of borehole burst and roadway coal burst is quantitatively explored, and a theoretical criterion for borehole effectiveness in coal burst control is proposed using the critical indices of borehole bursts. Finally, a design principle, determination method, and calculation formulae for the drilling parameters, which are directly related to the roadway burst risk state, coal seam thickness, coal properties, and drilling size, are proposed. The optimized drilling parameters of typical coal burst mines in Hebei and Inner Mongolia verify the engineering applicability and effectiveness of the proposed design method. This study proposes a quantitative determination method for destressing drilling parameters that supports coal burst occurrence theory. Highlights: Critical conditions for borehole bursts, directly related to the mechanical properties of coal and borehole size, are theoretically provided. Theoretical relationship between boreholes and roadway coal bursts is explored. Quantitative description of the borehole destressing principle to mitigate coal burst is provided. Theoretical criterion for boreholes to mitigate coal bursts, which is directly related to the critical conditions of borehole bursts, is provided. Quantitative method for determining the drilling parameters to mitigate coal bursts is proposed. [ABSTRACT FROM AUTHOR]

Original coal reservoir contains massive free and adsorbed methane, that directly affects the mechanical properties and permeability of coal with its unique dual effects, which may, thus, promote the gestation and occurrence of mine gas disasters. Mining disturbance and borehole drainage can facilitate the plastic rupture of surrounding rock mass, which would result in the gas migration law becoming more complex that, in turn, would be difficult to explain based on classical elastic deformation theory. Therefore, understanding elastoplastic deformation behavior and gas migration law relating to coal under engineering disturbance is crucial for preventing gas disasters. First, when mechanical and adsorption induced effects of gas on coal are considered, a concept of effective total pore pressure has been proposed. From which, calculation of plastic deformation in accordance with non-associated flow rule, a constitutive model that considered elastoplastic deformation (EPC Model) was established to simulate deformation and failure characteristics. Following that, a permeability jump coefficient was introduced to describe the sudden increase in permeability following damage and failure in coal, and an elastoplastic damage-permeability model (EPDP Model) was further deduced on basis of cubic law. Finally, through triaxial compression-seepage experimental data to verify the established EPC Model and EPDP Model. The results revealed that gas would weaken coal's mechanical properties (peak strength and elastic modulus) by changing its microstructure, whose deterioration would become more obvious with an increase of gas pressure. The changes to the permeability curve were of an "S" type, which showed a good corresponding relationship with the change trends relating to whole stress–strain curve. Both the EPC Model and the EPDP Model exhibited satisfactory matching effects with experimental data. Furthermore, EPDP Model was popularized and applied, with its universality being verified by the experimental data relating to a reduction in pore pressure seepage. This research will provide a new thinking for ensuring safe and efficient production in coal mines. Highlights: When the double effect of gas on coal were examined, Terzaghi's effective stress principle was modified appropriately, and a concept of effective total pore pressure has been proposed. The plastic strain on coal during triaxial compression was calculated, and an elastoplastic constitutive model that investigated gas action was further deduced. A permeability jump coefficient was introduced to describe permeability change following damage and failure to coal, thereby, making it possible to establish a damage-permeability model during elastoplastic deformation. The damage-permeability model was simplified appropriately, in order for it to be suitable to be employed as a classical elastic permeability model appropriate during CBM extraction stage, with its application scope of the permeability model being extended. [ABSTRACT FROM AUTHOR]

In many underground coal mines, a seam is underlain by weak floor material, and the load-carrying capacity of a pillar may be limited not by its own strength but by the bearing capacity of the floor. It has been proposed that bearing capacity may be estimated by formulae such as those of Terzaghi for structural footings on soil, but that approach is generally not valid because, for the slip surfaces assumed in the derivations of the formulae, the rock rises out of the floor beneath adjacent pillars. In the limiting equilibrium analysis proposed here, the distance to the side of a pillar to which a slip surface extends can be constrained according to the roadway or bord width. Examples are shown of the computation of bearing capacities of both homogeneous and multilayer dry and fully saturated floors, and results compared with those of elastoplastic finite element analysis. An approximate comparison with bearing capacities according to Terzaghi's formula for a strip footing is also presented for the hypothetical cases of wider roadways for which the assumed slip surfaces do not extend under adjacent pillars. For the cases considered, there is satisfactory agreement with Terzaghi's analysis and good agreement with the results of finite element analysis. However, only one finite element analysis was carried out, and it remains to be seen whether such agreement is consistently achieved for ranges of floor strength parameters and horizontal stress. Highlights: The floor which underlies the coal consists of one or more layers of weak sedimentary rock. The method may be applied to dry or fully saturated floor. Ultimate bearing capacity is computed by a novel limiting equilibrium analysis. Computed results are compared with those of Finite element analysis. [ABSTRACT FROM AUTHOR]

Coal–rock interface recognition is one of the key challenges in advancing unmanned rapid tunneling systems. To address this, a method based on variations in ground-penetrating radar (GPR) reflection wave amplitude is proposed for identifying coal-rock interfaces in soft coal seams. A mathematical model derived from Maxwell's equations calculates the coal seam area based on the reflected wave amplitude. Experiments using a 400 MHz radar antenna show that the method achieves identification errors of 3.58 cm, 3.74 cm, and 4.23 cm for coal-to-rock ratios of 1:2, 1:1, and 2:1, respectively. In practical applications within a coal mine excavation face, the identification error is 6.64 cm. This method provides crucial data for drum height adjustment and cutting arm speed regulation in unmanned tunneling systems. [ABSTRACT FROM AUTHOR]

Similar waveforms and overlapping frequency ranges make distinguishing blasting vibrations and microseismic signals challenging, causing interference with coal mine microseismic monitoring systems. To address this problem, we propose a spectrum dataset (MSData) reflecting the spectrum features of both signal types and present a signal classification network (SCNet) combining CNNs and Transformers for signal classification. The network can learn multi-dimensional features of both signals from MSData and automatically and efficiently identify the two signal types. Experimental results yield F1-scores of 0.991 for microseismic signals and 0.993 for blasting vibration signals, meeting engineering application requirements. [ABSTRACT FROM AUTHOR]

The complex stress environment in deep roadways, often exacerbated by thick and hard strata, frequently precipitates coal bursts, posing significant safety hazards. This paper investigates the mechanisms and preventive methods for coal bursts in the gob-side roadway floor (GSRF) under thick and hard roof in the Ordos region, China. First, the stress-distributing characters of GSRF were analyzed then a stress calculation formula was derived. A mechanical model was developed to determine the critical stress for buckling failure of the roadway floor strata. Criteria for the bursting instability of GSRF were then established. The lateral static load from the adjacent gob, the advancing static load from the working face, and the disturbance load from overlying thick and hard roof fractures combine to transmit high loads and energy to the roadway floor via the "roof → rib → floor" pathway, causing increased stress concentration and energy accumulation. When the conditions satisfy the criteria for bursting instability, coal bursts can occur on the roadway floor. To mitigate dynamic load disturbances, the paper proposes roof regional fracturing and abrasive water jet axial roof cutting. Hydraulic reaming of gutters in the roadway ribs and deep hole blasting at the roadway bottom corners are offered to alleviate the static loads on the surrounding rock. The implementation of targeted prevention measures for dynamic and static loads effectively reduces coal bursts in GSRF. These findings offer an example of preventing and controlling coal bursts in other mines of the Ordos region with comparable geological conditions. [ABSTRACT FROM AUTHOR]

The majority of a coal mine's goaf is semi-closed complex porous medium space, which is a critical place for coal spontaneous combustion disasters. To investigate the flow diffusion pattern of inorganic compounds in fractured coal in the goaf, as well as the capacity to put out coal fires. It examine the viscosity properties of an inorganic material slurry as a function of water/material ratio and time. By building a three-dimensional grouting test platform in the lab, simulating the broken coal body with sand and gravel, designing orthogonal tests to run multiple groups of grouting tests, and analyzing the effects of factors besides grouting pressure, water/material ratio, and air space ratio on the slurry diffusion radius. The effect of grouting pressure on the pattern of slurry diffusion radius of inorganic material and the water/material ratio under the action of grouting pressure is studied. The test of inorganic materials to extinguish coal pile fire is done, and the fire extinguishing and cooling ability is assessed in comparison to mud of the same grade, based on a prior research of inorganic materials to suppress CO formation in coal oxidation warming. According on the findings, the three-dimensional grouting test platform can pass the grouting test of loose sand and gravel bodies at various grouting pressures. The effects of grouting pressure, water/material ratio, and air space ratio on slurry dispersion are discovered to be multivariate power function relationships rather than linear correlations. The related slurry diffusion radius equation is established, and the variables impacting the parameters of the slurry diffusion range are evaluated, with the grouting pressure and water/material ratio having a substantial impact on slurry diffusion. Inorganic materials, as opposed to mud, require less time to extinguish coal pile fires and are less prone to scatter. It can form an oxygen barrier through continually covering the surface of coal. The study's findings might give a solid foundation for the avoidance of slurry and fire suppression of inorganic materials in the goaf. [ABSTRACT FROM AUTHOR]

To solve the problem of early warning of coal spontaneous combustion (CSC) caused by abnormal continuous CO overrun in the tailgate corner of low metamorphic coal seam, this paper takes 1306 working face of Dananhu No. 1 coal mine in Hami, Xinjiang as an example. Field measurement, experimental research and numerical simulation were used to study the sources of CO in the tailgate corner and its overrun mechanism, and a CO early warning limit calculation method suitable for CSC oxidation of low metamorphic coal seam is proposed. The results show that the ambient temperature oxidation is the most important source during non-production periods. When ambient O2 concentration is ≥7.7%, the coal sample can undergo ambient temperature oxidation to release CO, and the CO production rate has a good quadratic function fitting relationship with the ambient O2 concentration. The average CO production rate of the dissipation zone in the goaf is 3.3 times that of the oxidation zone, and the CO output proportion is 1.1. The CO early warning limit calculated can indicate the phenomenon of CSC oxidation well. The relevant research work is significant for the safety management of CSC in low metamorphic coal seam mining. [ABSTRACT FROM AUTHOR]

The cavities formed by the combustion of underground coal fires and the overlying rock damage caused by the combustion will cause the surface to subside or even collapse, forming crisscrossing surface cracks. On the basis of studying the fracture, subsidence and caving characteristics of overlying strata in the coal seam mining-combustion composite open space, the temporal and spatial development of the coal seam mining-combustion composite open space and the three-dimensional movement law of the induced overlying rock are studied in order to build three-dimensional dynamic theoretical distribution model of porosity in coal seam mining and combustion disturbance zone. Based on the porosity evolution model, the fire zone isotope radon method is used to detect the temperature anomalous area in the goaf. According to the location of the abnormal high-temperature area, a comprehensive treatment method is carried out, which is mainly based on the combined grouting of the upper and lower the mine, and supplemented by nitrogen injection and three-phase foam injection, thereby to solve the problem of difficult quantitative characterization of the multi-void medium in the mining-influenced underground coal fire area and targeted treatment for coal fire prevention and control in the mining-combustion disturbance area. [ABSTRACT FROM AUTHOR]

Gob is one of the most serious areas of coal spontaneous combustion. With the continuous increase of mining depth, the residual coal in gob bears increased axial stress, the rise of ground temperature, and the degree of fragmentation of mining coal and rock continues to increase, the external water in the mining process changes the water content of broken residual coal, under the influence of multiple factors, the prevention and control situation of coal spontaneous combustion in gob is becoming more serious. Based on the actual accumulation environment of residual coal in gob, this paper carried out the oxidation and temperature rise experiment of broken coal under the condition of water bearing and pressure. The variation laws of oxidation characteristic parameters such as outlet oxygen concentration, oxidation derived gas, oxygen consumption rate and heat release intensity were obtained. It is found that with the increase of water content of coal sample, the water content first promotes and then inhibits the oxidation process of coal. It is found that after water molecules form a relatively stable hydrogen bond with oxygen-containing functional groups, the total energy of the two-phase materials decreases, and the reason for the decrease of wetting heat release is analyzed. The influence mechanism of axial stress loading on coal spontaneous combustion oxidation process is studied. It is found that the increase of axial stress first promotes and then inhibits the process of coal spontaneous combustion. [ABSTRACT FROM AUTHOR]

When evaluating the suitability of using coal in various industries, it is subjected to technical analysis and a number of special technological studies. The obtained results in combination with elemental and group analysis allow choosing the most rational and economically efficient directions of their use, which plays not the least role in determining the economic significance of coal mining deposits. The work is based on theoretical research methods based on the basics of probability theory and mathematical statistics - to improve the existing methods of processing results and assessing the uncertainty of measurements; theories of accuracy - for the development of procedures for assessing the uncertainty of measurements of the quality parameters of solid mineral fuel during its tests; statistical modeling methods - to check the reliability of the developed provisions. A generalized parameter of the quality of solid mineral fuel has been synthesized, which makes it possible to evaluate its quality based on the results of tests conducted in coal chemical laboratories. improvement of methods of testing solid mineral fuel according to quality parameters by developing uncertainty assessment procedures. [ABSTRACT FROM AUTHOR]

The continuous mechanical mining technology represents the development trend and significant transformation in excavation techniques for non-coal mines. It embodies a systematic and integrated innovation encompassing rock breaking methods, rock-breaking equipment, excavation methods, and excavation processes. Based on the current status of continuous mechanical mining technology in non-coal mines, this paper firstly outlines the technical characteristics of mechanical mining and summarizes the key scientific and technological challenges to be addressed. It provides an overview of various mechanical cutter-based rock-breaking methods, rock mass cuttability, and the development and application of continuous mechanical excavation technology. In response to the problems and challenges facing continuous mechanical mining technology in non-coal mines, this paper proposes a four-tier approach for technological breakthroughs; "process needs-technological breakthroughs-equipment research and development-engineering application." Research will be conducted across multiple aspects, including rock-breaking theory, key technologies, mining equipment, mining methods, and complete sets of processes, aiming to promote the development and advancement of safe, efficient, green, continuous, and intelligent non-explosive mechanical mining technologies and equipment for non-coal mines in China. [ABSTRACT FROM AUTHOR]

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Coal mining in arid and semiarid regions often leads to numerous ecological and environmental problems, such as aquifer depletion, lake shrinkage, vegetation degradation, and surface desertification. The drainage from coal mining activities is a major driving force in the evolution of the groundwater-soil-vegetation system. In order to explore the effect of groundwater level fluctuation on soil properties and the response mechanism of surface vegetation in coal mining areas, this study is based on hydrogeological and ecological vegetation investigations in the Bojianghaizi Basin, and soil and vegetation samples are collected in the areas with different groundwater levels, and soil and vegetation indexes are analyzed with the aid of methods such as numerical statistics, linear regression, and correlation analysis with the aid of the Origin software. The results show that there is a significant negative correlation between groundwater table (GWT) and soil water content (SWC), soil conductivity, soil organic matter (SOM), soil available nitrogen (SAN), and soil available potassium (SAK). Mining activities have led to the destruction of the soil structure, greatly reducing its ability to retain water and fertilizer. The contents of SWC, SOM, and SAN in the mining area are significantly reduced, which are at least 49.73%, 47.56% and 59.90% lower than those around the mining area. On the northern and southern sides of the lake, serious soil salinization exists in the lakeshore zone where the depth to the water table is <0.5 m, and the water required for the growth of vegetation here mainly comes from the groundwater, so there are only a few water-loving and saline-resistant plants; when the depth to the water table is 0.5–7 m, the growth of surface vegetation is influenced by the double impacts of the water table and atmospheric precipitation with a high degree of species richness; when the depth to the water table is >7 m, the surface vegetation is only dependent on the limited atmospheric precipitation for water. When the depth of groundwater is >7 m, the surface vegetation only relies on limited atmospheric precipitation for water, and drought-tolerant plants mainly grow in these areas. This study not only provides a scientific basis for the sustainable development and environmental protection of similar mines in the world, but also has important significance in guiding the ecological management and rational utilization of water resources in coal mine areas. What is more, This study provides valuable insights into sustainable water resource management in arid and semi-arid regions, crucial for mitigating the ecological impacts of coal mining activities. [ABSTRACT FROM AUTHOR]

Abstract\nNovelty statementCoal mine drainage (CMD) is an environmental threat due to its high volume, low pH, presence of toxic metals, and absence of biodegradable organics. The present study aims to treat CMD in a horizontal sub-surface flow constructed wetland (CW) using dairy wastewater as an organic source. CW was planted with Typha angustifolia. Characteristics of synthetic CMD were (except pH, all unit mg/L) pH 1.9; Fe: 100, SO42−: 1,000, Mn: 6, Zn: 5, Co: 1, Ni: 1, and Cr: 1. CMD was mixed with synthetic dairy wastewater (pH: 5.05, COD: 2,700 mg/L, BOD: 1,600 mg/L) in the ratio of 3:1. Alkalinity of 120–190 mg/L CaCO3 was generated and effluent pH improved from 2.2 to 6.6. Metals precipitated as metal sulfide or hydroxide. Sulfate removal was hindered due to the synergistic toxicity of several metals. Except for Mn, all other effluent parameters were within the discharge limit for disposal in inland surface water.There is limited information available on the advantages of using organic rich wastewater as a substrate for treatment of low carbon coal mine drainage (CMD). Coal mine drainage was mixed with dairy wastewater and treated in horizontal flow constructed wetland. Organic removal, metal removal, sulfate removal, and pH improvement of mixed wastewater are investigated in the present study. [ABSTRACT FROM AUTHOR]

AbstractCharacterization of pore structures and flow simulation are essential to spatial migration of coalbed methane. In this paper, coal samples from Xinjing and Xinzhuang coal mines are collected and a comprehensive characterization method by using computed tomography (CT) technique and experiments of mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) is proposed. Pore structure parameters are finely characterized and analyzed. Moreover, the flow process for coal samples is visualized and flow characteristics are analyzed. The result shows that pore structures of coal samples are strongly heterogeneous and are dominated by micropores, and filled with kaolinite, calcium monofluorophosphate, pyrite, etc. The flow velocity increases obviously in micropores and narrow throats. The flow is greatly affected by the pore structure. This study is of practical significance for the coalbed methane recoverability evaluation and exploration. [ABSTRACT FROM AUTHOR]

To address the issues of large anomalous triangulations, invalid interpolations, and uneven boundary interpolations in kriging interpolation, we propose research on a coal seam modeling construction method based on improved kriging interpolation. The work methodology assumes that by introducing kriging interpolation and analyzing its problems, we improve the interpolation method via a local interpolation algorithm for large anomalous triangulations, an optimization algorithm for locally redundant interpolation points, and a nonuniform boundary adaptive local interpolation algorithm. These improvements allow the interpolation method to better reflect the variability and realistic nature of coal seams. The research results indicate that applying this method to the construction of the Dananhu No. 2 open-pit mine coal seam model has improved the issue of coal seam transition stiffness, such as abnormal large-area triangulation in areas with significant elevation differences. This approach appropriately reduces the memory space usage without altering the coal seam morphology (which saves approximately 27,000 KB of memory, equivalent to the space occupied by 4 out of 21 coal seams). It has also prevented inaccuracies in boundary line positioning and transitions caused by too low a density of points on the coal seam reserve boundary line, resulting in smoother model transitions at the boundaries that better align with the actual coal seam change trends, the error rate in coal quality estimation decreased by 62.69%. This study provides data support for mining planning and reduces costs. This method can be extended to the construction of all mine models. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The major ion and stable isotope geochemistry of coalmine water of Talcher coalfield was investigated to identify prominent hydrogeochemical processes controlling mine water composition and estimate annual elemental flux. Mine water samples from opencast and underground coalmines were analysed for EC, pH, TDS, TH, major ions and stable isotopes i.e. δ18O and δ2H. Coalmine water exhibited a wide range of pH values, from highly acidic to alkaline, and were dominated by SO42− and Ca2+ in their total anionic (TZ−) and cationic (TZ+) composition respectively. Ca-Mg-SO4 was the most dominant hydrochemical facies. High contribution of Ca2+and Mg2+ and SO42− towards the TZ+ and TZ− and low HCO3−/(HCO3−+SO42−) ratio suggested a major role of sulphide oxidation in determining coalmine water chemistry. A slight deviation in the regression line towards right side of the Global Meteoric Water Line and Local Meteoric Water Line in the bivariate plot of δ18O vs δ2H implied that water experienced evaporation to some extent and originated mainly from atmospheric precipitation. Most of the mine water were undersaturated with respect to carbonate and sulphide phases. Talcher coal mines annually delivered 47.06 × 106 m3 mine water and 28.481 × 103 tonnes of solute loads into nearby drainage. [ABSTRACT FROM AUTHOR]

Predicting and understanding the phenomenon of surface subsidence caused by coal mining in working faces with faults are important issues for safe coal mining and efficient production. In numerical simulation experiments, it was found that the phenomenon of surface subsidence manifests when faults exist, and the degree of influence of faults with different dip angles on surface subsidence varies. This phenomenon is attributed to fault activation. According to the experimental results, the impact of faults with different dip angles on surface subsidence falls into three levels: level I for 35° faults, level II for 45° and 55° faults, and level III for 65° and 75° faults. Similarly, the relationship between the difficulty of fault activation and the dip angle of faults can be categorized as 35° faults prone to activation, 45° and 55° faults difficult to activate, and 65° and 75° faults not prone to activation. The probability integral correction model for fault mining, which integrates the surface subsidence values caused by fault-induced attenuation and the subsidence arising from separation spaces, was introduced, thereby constructing a surface subsidence prediction model. This proposed prediction model can accurately predict surface subsidence, with a root mean square error of 10.74 mm between the predicted and measured values, as validated using DInSAR results from the III 6301 working face in the Jincheng mining area. [ABSTRACT FROM AUTHOR]