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Abstract Exposure to respirable coal mine dust (RCMD) can cause chronic and debilitating lung diseases. Real-time monitoring capabilities are sought which can enable a better understanding of dust components and sources. In many underground mines, RCMD includes three primary components which can be loosely associated with three major dust sources: coal dust from the coal seam itself, silicates from the surrounding rock strata, and carbonates from the inert ‘rock dust’ products that are applied to mitigate explosion hazards. A monitor which can reliably partition RCMD between these three components could thus allow source apportionment. And tracking silicates, specifically, could be valuable since the most serious health risks are typically associated with this component-particularly if abundant in crystalline silica. Envisioning a monitoring concept based on field microscopy, and following up on prior research using polarized light, the aim of the current study was to build and test a model to classify respirable-sized particles as either coal, silicates, or carbonates. For model development, composite dust samples were generated in the laboratory by successively depositing dust from high-purity materials onto a sticky transparent substrate, and imaging after each deposition event such that the identity of each particle was known a priori. Model testing followed a similar approach, except that real geologic materials were used as the source for each dust component. Results showed that the model had an overall accuracy of $$86.5\%$$ 86.5 % , indicating that a field-microscopy based monitor could support RCMD source apportionment and silicates tracking in some coal mines.

The coal mining changes the overburden boundary conditions and causes the redistribution of the in-situ stress and the deformation, movement, fracture of overburden rock. The damage conducts from the bottom to top in overburden and causes the damage of aquifers, surface appurtenances, and mining area ecosystem. Besides, while the modern mining ensures the energy demand of social development, it also causes great damage to groundwater , ecological environment and construction/construction facilities in mining areas. In order to solve the problem of large-scale coal mining damage and the safe coordination of protected objects in the mining area, based on the systematic analysis of the damage reduction mining theory and technology and long-term practice worldwide, according to the concept of “source damage reduction” and “pre-mining source control, mining optimization reduction and post-mining collaborative repair” for the entire mining process reduction, a pre-mining, mid-mining, post-mining reduction technology is proposed as the main measures for reducing mining damage throughout the entire mining process, which includes the three types and four technologies: “source reduction technology based on mining process parameter optimization, hard rock pre-fracturing-soft rock grouting modification and postmining water conduction fracture sealing and water control technology, as well as maintaining the stability of the overburden bearing structure during mining”. And the theoretical and technical system for reducing mining damage in underground coal mines has been constructed, and the focus and direction of research on reducing mining damage has also been clarified. In terms of mining damage monitoring, due to the significant spatiotemporal differences in monitoring technology, it is difficult to achieve a synchronous monitoring of surface deformation and cracks in the same space-time, as well as an integrated monitoring of multiple elements of the surface ecological environment. Therefore, it is still necessary to propose the targeted methods for correcting and processing asynchronous data from the multi-source monitoring of coal mining induced damage. In terms of damage conduction theory, based on the theory of overburden damage conduction, a mining damage field model is proposed from the perspective of energy indicators. Combined with the differences in the combination of soft-hard rock layers and the media of rock-soil layers, a unified damage field quantity and cross interface conduction theory for the multiple factor indicators of “overburden-aquifer-surface-ecology” is proposed. The 12401 longwall face of the Shangwan coalmine has adopted the measures of pre-mining parameter optimization and grouting in the caving zone during mining, the maximum surface settlement amount has been relatively reduced by 25%, and the surface cracks have been adjusted from step-like cracks to dynamic small cracks. In addition, since the technical implementation at the Shendong mining area in 2010, the vegetation coverage has increased from an average of 31% to a maximum of 74.1%.

Abstract Chisel pick is a basic and important rock cutting tool, and the performance of chisel pick directly affects rock mining. In this paper, a rock cutting device was developed for chisel picks cutting experiments. The influence of the depth of cutting, width of chisel pick, rake angle, back clearance angle and tip fillet radius on the cutting performance such as cutting force, normal force, and specific energy has been comprehensively studied. In addition to the general conclusions, the experimental results show that the back clearance angle has an influence range on the cutting, and the ratio of the normal force to the cutting force decreases with the increase of the rake angle; the tip fillet radius greatly improve the mean cutting force and specific energy. The experimental results will provide data support for the design of chisel picks on rock excavation machinery and a more reasonable chisel pick cutting rock mechanics model.

Abstract Ground subsidence in Western coal mining areas is characterized by rapid deformation, extensive damage, and a wide range of impacts. The conventional observation methods are inappropriate for surface damage monitoring in high-intensity mining areas of Western China. Therefore, it is a crucial problem to quickly, accurately, and comprehensively monitor the ground subsidence and environmental damage caused by high-intensity and large-scale mining. In this study, we propose a monitoring method for the ground subsidence of high-intensity mining with Unmanned Aerial Vehicle Lidar (UAV-LiDAR) measurement technology. Taking a mine in Ordos of China as an example, the Digital Elevation Model (DEM) is obtained by Kriging Interpolation of the ground point cloud from UAV-LiDAR. Then, the multi-stage DEM differential processing is employed to get ground subsidence. Finally, the median and bilateral filters combine for denoise to obtain the high-precision ground subsidence. The results show that the accuracy of the ground DEM generated by UAV-LiDAR is 15 mm and the mean square error of the ground subsidence basin is 39 mm. UAV-LiDAR technology can quickly obtain abundant surface data and obtain high-precision ground subsidence. Therefore, the application of this technology and method in subsidence monitoring in mining areas is feasible. And it can provide support for ecological environment monitoring, land reclamation, and ecological restoration in mining areas. The research results can provide a useful basis for monitoring the surface damage of coal mining in Western China.

In addressing the issue of poor gas sensitivity in semiconductor CO sensor materials used in mining, such as pure PANI. This study utilized an ice‐water bath in combination with an in‐situ polymerization method to synthesize a new composite material consisting of Cu(II)‐racemic glutamate nanofibers and PANI. The morphology, structure, and chemical bonds of the composite material were analyzed using scanning electron microscopy‐energy dispersive spectroscopy (SEM‐EDS) and spectral analysis. The material's ability to detect CO (100–500 ppm) at room temperature was investigated, revealing a response value of up to 6.8 % for 400 ppm CO detection when the composite material was deposited on a ceramic interdigital electrode. The material exhibited good selectivity and responsiveness to CO detection at room temperature, attributed to the heterojunction formed between Cu(II)‐racemic glutamate nanofibers and PANI, which enhanced carrier migration. Consequently, the Cu(II)‐racemic glutamate nanofiber/PANI composite(Cu(II)‐RGlu/PANI) material shows promise as a high‐performance sensing material for CO detection at room temperature and as a low‐power, integrable sensor material for underground coal mines. This research contributes to the development of a theoretical framework for such applications. [ABSTRACT FROM AUTHOR]

Assessing the appropriateness of existing native plant materials can both determine which seed source to utilize for restoration projects, and identify locations for which new seed sources need to be developed. Here, we demonstrate an approach to meet these needs. This method identifies areas of high restoration need based on disturbance patterns, assesses the regional suitability of existing native plant materials based on climate similarity, and highlights geographic (and climatic) gaps where existing materials are likely unsuitable and where plant material development projects can be prioritized. We examined 12 high priority restoration species across the Colorado Plateau, a 38‐million‐ha region of the Intermountain West, United States to test our methodological pipeline. Fifty‐four percent of the Colorado Plateau is disturbed by livestock grazing, wildfires that have burned in the past 20 years, or energy production from oil and gas wells, natural gas pipelines, and coal mines. Of the 28 commercially available plant materials for six of the focal species, only 3 have climate similarity that encompass more than 50% of the species modeled habitat on the Colorado Plateau. Across all commercial materials, most species (10 of 12) do not have any suitable plant material for 70% or more of their geographic range on the Colorado Plateau. Of those areas identified as not having any suitable plant materials, 47–56% are also disturbed. Our method provides usable, flexible protocols and spatially referenced data sources for optimizing the planning of new native plant materials in any region where restoration is needed and spatial data are available. [ABSTRACT FROM AUTHOR]

As the shallow coal seams are gradually being exhausted, mining of the lower group of coal seams in the shallowly buried proximity coal seam group becomes inevitable. Due to geological conditions affecting the upper group coal seams, various coal mining methods have resulted in a significant number of non-sufficient and sufficient collapse mining areas. The presence of water and gas in these mining areas can potentially impact the safe production of the lower group coal seams through inter-layer rock fractures. Therefore, studying the evolution characteristics and formation mechanism of inter-layer rock fractures is of utmost importance. In this paper, we employ theoretical analysis, numerical simulation, and similar simulation methods to investigate the evolution characteristics and formation mechanism of inter-layer rock fractures during the mining of the lower 3–1 coal seam. We specifically focus on the formation of different mining areas in the upper 2–2 coal seam, using the mining of 2–2 and 3–1 coal seams in the Hanjiawan coal mine as our research context. The study results reveal that the inter-layer rock fractures exhibit an overall positive trapezoidal distribution in different mining areas. We quantify the variation in density and width of inter-layer rock fractures in the two mining areas by utilizing the concept of rock damage degree. We analyze the overall damage degree, tensile damage degree, and shear damage degree ratios. The formation of inter-layer rock fractures is primarily influenced by the combined effect of various coal mining methods in both the upper and lower coal seams. The stress changes resulting from mining activities in these seams contribute to the development of transverse separation fractures and longitudinal breaking fractures within the inter-layer rock. The stress changes induced by mining operations in the upper and lower coal seams have been analyzed, and distinct stress regions have been identified. To understand the mechanism of inter-layered rock fracture development in the upper and lower coal seams, a mechanical expansion model of inter-layer rock fractures has been constructed for different stress regions. Highlights: The evolution process and development characteristics of inter-layered rock fractures, as well as their differences when different coal mining methods are employed in the upper coal seam, have been revealed. To determine the influencing factors and development patterns of inter-layered rock fractures under different coal mining methods. Quantitatively comparing and analyzing the damage of inter-layered rock and the percentage of damage degree under different coal mining methods, we found that the damage degree was 61% and 52%, respectively. The study shows that when mining the upper coal seam, the inter-layer rock primarily extends through primary microscopic fractures. On the other hand, when opening the lower coal seam, the main development is observed in macroscopic tension fractures and shear misalignment fractures. Based on the study of the development process of macroscopic fractures and microscopic fractures in the inter-layered rock, the mechanism of fracture development and evolution of the inter-layered rock under different coal mining methods has been determined. [ABSTRACT FROM AUTHOR]

The coal mining business is quickly expanding to meet the increasing demand for coal for power plants. They are introducing a variety of intricate and sophisticated equipment for the system's mechanization and atomization. The mining industry spends a significant amount of money on this equipment. The equipment's reliability, maintainability, and availability have all become critical parameters in ensuring ongoing output. The greatest option for mechanization in underground mines for making holes for coal preparation and roof rock support is to use UDM in tandem with LHD. UDM has the ability to drill holes in any direction and at any angle. It is necessary to measure and ensure its reliability to reduce coal production downtime. OEM has designed the UDM to serve at minimum for 8 years of life, 25,000 h of operation, and 473,000 m of total drilling, whichever comes later. The Markov approach was used to assess the UDM system's reliability by examining the failure and repair rates of seven modules of UDM connected in series, which is novel to this study, as no prior antecedent research has been done in this area. UDM's reliability declined after 8 years of operation, while its maintainability skyrocketed. The availability of the UDM may be increased from 79 to 88% by lowering the unavailability of hydraulic, electrical, and drill units by 4, 2, and 3%, respectively. This study demonstrates how strengthening the maintainability of the allied system of UDM, as well as resolving operating faults, can improve UDM availability and assure a smooth and continuous production rate in the mines. Highlights The UDM (Underground Drilling Machine) and LHD (Load-Haul-Dump) were introduced as the superior possibilities for mechanization in underground mines for coal preparation and roof rock support, offering the capacity to drill holes in any direction and angle. UDM's reliability, maintainability, and availability are rigorously assessed using the Markov approach, with a focus on meeting the OEM design requirements of 8 years of service life, 25,000 operating hours, or 473,000 m of total drilling. To evaluate the UDM system's dependability and how it changes over time, as shown in tables and graphs, it is necessary to identify specific modules within it and their connections, treating them as a series system. Exhibiting how improving system availability by reducing the unavailability of specific modules can have a significant positive impact on the availability of the entire system. Recommendations for specific training programs for UDM operators to help them handle the equipment while it is in use and prevent mechanical damage, improving the machine's overall safety and dependability in underground coal mining operations. [ABSTRACT FROM AUTHOR]

In order to safeguard the surface structures from mining damage while optimizing the liberation of coal resources under the dense surface buildings of the Cedi River coal mine. Considering that the analysis of the structure and type of surface buildings and the geological mining conditions of the mine, a wide strip mining design with a retention width of 70 m and a mining width of 50 m was finally determined by using the pressure arch theory and Wilson's theory, combined with the actual layout of working faces 51,002, 51,004 and 51,006 at the site.The strip mining design is verified by probability integral method and FLAC3D numerical simulation calculation respectively, The findings indicate that the highest value of earth surface subsidence created by the mining of the wide strip is 210 mm, the surface horizontal deformation value is 1.0 to − 1.4 mm/m, the damage to surface buildings is less than Level I, which satisfying the prerequisites of the surface building protection level, and can realize the continuous advancement of mine 51,002, 51,004 and 51,006 working faces, The coal pillars of the retained strip have sufficient support strength and long-term consistency, and the movement and deformation of the overburden after mining will not cause undulating subsidence of the surface, which effectively solve the mine's technical difficulties in safely coal mining under surface buildings. [ABSTRACT FROM AUTHOR]

To enhance the accuracy of identifying water sources in mine inrush incidents, this study, taking the Shengquan coal mine in Shandong, China, as a case study, proposes a novel water source identification model based on an improved autoencoder—the "Masked Autoencoder-based Classifier" model. This model, through a unique autoencoder framework and a custom 'masked_loss' loss function, achieves semi-supervised learning and dimensionality reduction of groundwater sample ionic data. By configuring the hidden layers, the classifier component of the model directly receives data processed by the encoder component. This not only improves the model's performance but also optimizes its complexity. Through an evaluation of the model's fitting effectiveness, our model achieved an average accuracy of 88.8% across 20 runs, with precision, recall, F1-score, and MCC reaching 88.1%, 80.6%, 0.827, and 0.833, respectively, significantly outperforming other classic models. The model successfully identified the sources of three sets of inrush water samples, with a high number of successful runs and clear average probabilities. This work contributes not only to the field of mine water inrush source identification but also offers a new perspective for the broader field of machine learning. [ABSTRACT FROM AUTHOR]

Coal mining in Central Kalimantan, Indonesia, evokes not only struggles on the control of land but also conflicts between different notions of land. Based on ethnographic research in a mining area, I describe a relational attached notion of land which is subdued by a detached, monetary-based understanding in the course of increased mining. In negotiations on the compensation of land with representatives of the mining companies, members of the village elite, which are entangled in patronage networks with the companies, ignore the various notions of land by other villagers and sideline those who are critical. With my article, I contribute to the ontological dimension of environmental conflicts with insights from Southeast Asia thereby giving a diversified picture of the struggles on access and the lacking acknowledgement of different notions of land. [ABSTRACT FROM AUTHOR]

Human activities have seriously affected the quality of shallow groundwater in coal mining areas and understanding the spatial and temporal evolution of groundwater is a widespread concern. This study was conducted to determine the primary hydrogeochemical processes in the Sunan Mining region, China. We collected 84 groundwater samples from a Quaternary loose aquifer and tested the macronutrient content using standard methods. Multivariate statistical analysis and hydrochemical analysis were conducted to analyze the sources and formation mechanisms of groundwater constituents in the early, middle, and late stages of mining. Results show that the water quality evolved from Cl·SO4-Na.Ca type to SO4-Na.Ca type. Mineral dissolution, halite dissolution, cation exchange, and desulfurization primarily occurred in the groundwater, and the hydrogeochemistry was strong in the northern part of the study area; however, the degree of both dissolution and reaction gradually weakened with increasing mining activities. [ABSTRACT FROM AUTHOR]

On February 22, 2023, a devastating landslide occurred on the mining slope of an open-pit coal mine in Inner Mongolia, China, leading to the mining area being buried and 53 fatalities. The source area of the landslide measured approximately 500 m in both length and width, with an estimated volume of the deposited material reaching approximately 5 million cubic metres. Based on the severe impact of this incident, our study conducted preliminary research using a combination of methodologies, including particle image analysis, synthetic aperture radar interferometry, interpretation of optical remote sensing data, and post-event news reports analysis. The results indicated that the landslide lasted 23 s from initiation to cessation of movement. The historical deformation indicated that prior to the resumption of the mining activities, only localized deformation was observed at the rear edge of the landslide. However, when mining activities resumed in April 2021 and extended to the vicinity of the north slope, the deformation range and rate in the source area of the landslide rapidly increased. The investigation deduced that the soft foundation at the slope bottom and mining activities are the primary causative factors of this event. Mining activities, which stripped coal seams within the slope and surface rock masses, led to the expansion of tension cracks within the landslide body, weakening resisting forces at the leading edge and thus playing a significant role in destabilizing the landslide body. The evolution of the landslide from incubation to instability could be divided into four stages: early microcrack development, slow creep, accelerated deformation after resumption of mining, and ultimate instability. Therefore, it is of great significance to advance real-time deformation monitoring and early warning systems specifically those designed for mining slope areas by comprehensive measures. Furthermore, enhancing the high-frequency monitoring capabilities of synthetic aperture radar satellites is crucial to reducing the occurrence of these catastrophic events. [ABSTRACT FROM AUTHOR]

Objective: Whether coal mine dust exposure increases cardiovascular diseases (CVDs) risk was rarely explored. Our objective was to examine the association between coal mine dust exposure and cardiovascular risk. Methods: We estimated cumulative coal mine dust exposure (CDE) for 1327 coal miners by combining data on workplace dust concentrations and work history. We used brachial-ankle pulse wave velocity (baPWV, a representative indicator of arterial stiffness) and ten-year atherosclerotic cardiovascular disease (ASCVD) risk to assess potential CVD risk, exploring their associations with CDE. Results: Positive dose-response relationships of CDE with baPWV and ten-year ASCVD risk were observed after adjusting for covariates. Specifically, each 1 standard deviation (SD) increase in CDE was related to a 0.27 m/s (95% CI: 0.21, 0.34) increase in baPWV and a 1.29 (95% CI: 1.14, 1.46) elevation in OR (odds ratio) of risk of abnormal baPWV. Moreover, each 1 SD increase in CDE was associated with a 0.74% (95% CI: 0.63%, 0.85%) increase in scores of ten-year ASCVD and a 1.91 (95% CI: 1.62, 2.26) increase in OR of risk of ten-year ASCVD. When compared with groups unexposed to coal mine dust, significant increase in the risk of arterial stiffness and ten-year ASCVD in the highest CDE groups were detected. Conclusion: The study suggested that cumulative exposure to coal mine dust was associated with elevated arterial stiffness and ten-year ASCVD risk in a dose-response manner. These findings contribute valuable insights for cardiovascular risk associated with coal mine dust. [ABSTRACT FROM AUTHOR]

The anthracite coal mining landscape of northeastern Pennsylvania is in ruin, a by-product of two centuries of unchecked capitalism. Much of the land is stripped of its timber and surface mines lay abandoned. The industry began its decline after WWI and virtually collapsed during the post-WWII era. Waste piles of coal litter the landscape, and the streams and rivers are considered dead because of the minerals and high acid content of water draining from abandoned mines. Many scholars have written about the extreme work conditions the coal workers faced, the demise of the coal industry, and the impact of deindustrialization on the region's people. Often overlooked is how members of the mining communities had a radical hope. Radical hope helps oppressed people to see that another condition and another world is possible, although not guaranteed. Re-examining oral histories from the anthracite region recorded in the 1970s, when the industry was in its great decline, demonstrates how these mining communities anticipated a future good, understanding the struggle to attain it. [ABSTRACT FROM AUTHOR]

As coalmines extend more deeply, strong mining-induced earthquakes occur more frequently; these seriously threaten the safety of underground miners and aboveground residents, as well as the productivity and effectiveness of mining activities. The distribution of mining-induced earthquake characteristics and hard roof breaking mechanisms are analyzed and revealed using the methods of field monitoring and theoretical analysis, and prevention and control technology were proposed and applied in a field application, for a typical dynamic disaster problem at Dongtan Coalmine. As indicated by the results, strong mining-induced earthquakes (E ≥ 105 J) were mostly related to the coordinated failure of several strata, and the migration and fracture of the overlying strata led to significant subsidence of the surface. As mining activities advance, the abutment stress within the coal seam in front of the coalface will dynamically change and be transferred more deeply into the coal seam under the influence of a mining-induced earthquake. Based on the mechanical behavior, the fracture structures of the overlying multiplicity of key strata are divided into main and subordinate "O-X" types. As the coal is exploited, the O-X scope gradually increases from the near field to the far field. As indicated by the field application, the implementation of deep-hole blasting could effectively weaken the integrity of the thick and hard rock strata and change the length of the overhang roof, so as to reduce the risk of strong mining-induced earthquakes, i.e., the incidence of strong mining-induced earthquakes above 5 × 105 J would be significantly reduced. Meanwhile, the frequency of rock strata collapse increases, and the average distance from the epicenter centrum to the coal seam is reduced to 47 m. The governing effect is good. We expect that the results of this study could provide references for dynamic disaster governance in similar mine areas. [ABSTRACT FROM AUTHOR]

In order to efficiently and accurately control coal dust pollution in coal mining faces, this study addresses the insufficient research on the dust generation mechanism during cutting. Firstly, a similar experimental platform for simulating coal wall cutting with a drum cutter was used to investigate the changes in coal wall fragmentation and dust generation at drum speeds of 35 r/min, 50 r/min, 65 r/min, and 80 r/min. The experimental results revealed that the degree of coal wall fragmentation and dust generation increased with the increase in rotational speed, leading to a wider range of particle size distribution and an increase in the generation of fine dust particles. A 1:1 scale discrete element simulation of coal wall cutting with a drum cutter was conducted based on the experiments. The results indicated that, under the four rotational speeds, the cracks generated during coal wall fracture were predominantly tensile cracks, accounting for over 76% of the total crack count. The total number of cracks increased from 10,600 to 11,200, the number of free single particles increased from 2555 to 2728, and the fragmentation volume increased from 0.021607 to 0.023024 m3. The range and degree of coal wall fragmentation increased with the increase in drum speed. [ABSTRACT FROM AUTHOR]

Coal is a non-renewable fossil energy source on which humanity relies heavily, and producing one ton of raw coal requires the discharge of 2–7 tons of mine water from the ground. The huge drainage task increases the cost of coal mining in coal mines significantly, so saving the drainage cost while guaranteeing the safe production of coal mines is a problem that needs to be solved urgently. Most of the fuzzy controllers used in the traditional dynamic planning methods applied to mine drainage are two-dimensional fuzzy controllers with limited control effect, so the traditional two-dimensional fuzzy controllers are improved by introducing the rate of change of gushing water to form a three-dimensional fuzzy controller with three-dimensional control of instantaneous section—water level—rate of change of gushing water, and at the same time, the optimized dynamic planning method is designed by combining the Avoiding Peak Filling Valley strategy and the optimal dy-namic planning method is used in conjunction with the un-optimized dynamic planning method. The optimized dynamic planning method is applied to the same coal mine water silo gushing water experiments; experimental comparison found that the pumping station system before the optimi-zation of the electricity consumed is 52,586 yuan/day, while after the optimization of the electricity consumed is reduced to 41,692 yuan/day, the cost per day consumed compared with the previous reduction of 20.69%, a year can be saved 3,969,730 yuan. Therefore, the mine water bin drainage method based on fuzzy control and Avoiding Peak Filling Valley strategy proposed in this paper can be used as an improvement method of the existing mine drainage method, which can further ex-pand the economic benefits of coal mines and realize safe production while realizing cost savings. [ABSTRACT FROM AUTHOR]

Fire and smoke detection is crucial for the safe mining of coal energy, but previous fire-smoke detection models did not strike a perfect balance between complexity and accuracy, which makes it difficult to deploy efficient fire-smoke detection in coal mines with limited computational resources. Therefore, we improve the current advanced object detection model YOLOv8s based on two core ideas: (1) we reduce the model computational complexity and ensure real-time detection by applying faster convolutions to the backbone and neck parts; (2) to strengthen the model's detection accuracy, we integrate attention mechanisms into both the backbone and head components. In addition, we improve the model's generalization capacity by augmenting the data. Our method has 23.0% and 26.4% fewer parameters and FLOPs (Floating-Point Operations) than YOLOv8s, which means that we have effectively reduced the computational complexity. Our model also achieves a mAP (mean Average Precision) of 91.0%, which is 2.5% higher than the baseline model. These results show that our method can improve the detection accuracy while reducing complexity, making it more suitable for real-time fire-smoke detection in resource-constrained environments. [ABSTRACT FROM AUTHOR]

Coal gangue is a byproduct of coal mining and processing, and according to incomplete statistics, China has amassed a substantial coal gangue stockpile exceeding 2600 large mountains, which poses a serious threat to the ecological environment. Utilizing gangue as a coarse aggregate to produce gangue concrete (GC) presents a promising avenue for addressing the disposal of coal gangue; however, gangue concrete presents several challenges that need to be tackled, such as low strength and poor resistance to repeated loads. In this study, polypropylene fibers (PPFs) were incorporated into gangue concrete to enhance its utilization rate. Uniaxial compressive and repeated loading experiments were then conducted to investigate the uniaxial strength and fatigue properties of polypropylene fiber-reinforced gangue concrete (PGC) with varying gangue substitution rates (20%, 40%, and 60%) and different polypropylene fiber admixtures (0, 0.1%, 0.2%, and 0.3%). The findings indicate that incorporating gangue at a substitution rate of 40% could notably enhance the uniaxial compressive strength of PGC, resulting in a maximum increase of 19.4%. In the repeated loading experiments, the ductility of PGC was enhanced with the incorporation of PPFs, resulting in a reduction of 33.76% in the damage factor and 19.42% in residual strain for PGC-40-0.2 compared to PGC-40-0. A PPF content of 0.2% was found to be optimal for enhancing the fatigue performance of PGC. Scanning electron microscope (SEM) testing proved the improvement effect of polypropylene fiber on gangue concrete from a microscopic perspective. This study provides crucial experimental data and a theoretical foundation for the utilization of gangue concrete in complex stress environments. [ABSTRACT FROM AUTHOR]

To study the influence of coal mining on the water richness overlying strata in the mining area using time-lapse electrical monitoring technology, four dataset acquisitions were completed with the same acquisition method, equipment, parameters, and processing flow. According to the characteristics of the data, major problems such as topographic correction, high-precision denoising, spatial and temporal normalization, and resistivity data inversion have been solved. Precise tomographic imaging was achieved through high-precision data processing and difference inversion. The results show that the electrical stratification characteristics of the overlying soil and rock layers are clear, the resistivity from the surface down gradually increases, and the electrical layers are not uniform locally. During mining, the overlying strata are affected by mining, the electrical resistivity of the underlying aquifers increased to varying degrees, and the fluctuation of electrical resistivity increased while the aquifer's water content decreased. After mining, the overlying aquifer has the phenomenon of 'reduced resistivity and water recovery'. After a period of time, the overlying soil disturbance and overlying rock failure zone will gradually tend to be stable. Meanwhile, the aquifer structure and water content will also gradually recover. Our results could provide guidance for water resources protection in this region. [ABSTRACT FROM AUTHOR]

Horizontal wells within the roof are an effective method to develop gas in broken and soft coal seams, and layer-penetrating fracturing is a key engineering method for the stimulating of horizontal wells within the roof of a coal seam. To understand the propagation law of fracture in the composite roof of coal seams, this study conducted research using numerical simulation and physical similarity simulation methods. Furthermore, engineering experiments were carried out at the Panxie coal mine in the Huainan Mining Area and the Luling coal mine in Huaibei Mining Area, to further validate this technology. The numerical simulation results indicated that fracture within the coal seam roof can propagate from the roof to the target coal seam, effectively fracturing the coal seam. Due to the coal seam's plasticity being greater than that of the roof mudstone, the coal seam forms a broader fracture than the roof. With the increase in pseudo roof mudstone thickness and being under constant fracturing displacement, the energy consumed by the pseudo roof mudstone during fracturing causes a decrease in pore pressure when fracture extends to the coal seam, resulting in a reduction in fracture width. Therefore, the pseudo roof mudstone is an adverse factor for the expansion of hydraulic fracturing. Physical similarity simulation results demonstrated that when horizontal boreholes were arranged within the siltstone of the coal seam roof, were under reasonable vertical distance and high flow rate fracturing via fluid injection conditions, and if the coal seam had a thin pseudo roof mudstone, the fracture could propagate through the direct roof-pseudo roof interface and the pseudo roof-coal seam interface, extending to the lower coal seam. The fracture form was curved and had irregular vertical fractures, indicating that hydraulic fracturing can achieve production enhancement and the transformation of soft and hard coal seams. However, when the coal seam had a thick pseudo roof mudstone, the mudstone posed strong resistance to hydraulic fracturing, making it difficult for the fracture to propagate to the lower coal seam. Therefore, the pseudo roof mudstone plays a detrimental role in hydraulic fracturing and the production enhancement of coal seams. The engineering verification conducted at Panxie coal mine and Luling coal mine showed that by utilizing a construction drainage rate of 7.5 cubic meters per minute at Panxie coal mine, the maximum fracture length reached 218.3 m, with a maximum fracture height of 36.8 m. The maximum daily gas production of a single well reached 1450 cubic meters per day, with a total gas extraction volume of 43.62 × 104 cubic meters across 671 days. At Luling coal mine, utilizing a construction drainage rate of 10 cubic meters per minute, the maximum fracture length reached 169.1 m, with a maximum fracture height of 20.5 m. The maximum daily gas production of a single well reached 10,775 cubic meters per day, with a total gas extraction volume of 590 × 104 cubic meters for 1090 days. This indicated that the fracture within the roof of coal seams can penetrate the composite roof of coal seams and extend to the interior of the coal seams, achieving the purpose of transforming fractured and low-permeability coal seams and providing an effective mode of gas extraction. [ABSTRACT FROM AUTHOR]

Despite the pressure of carbon emissions and clean energy, coal remains the economic backbone of many developing countries due to its abundant resources and widespread distribution. The stable supply of coal is also vital for the global economy and remains irreplaceable in the future global energy structure. China has been a major contributor to annual coal output, accounting for nearly 50% worldwide since 2014. However, despite implementing intelligent coal mining technology, China's coal mining industry still employs over 1.5 million underground miners, posing significant safety risks associated with underground mining operations. Therefore, the introduction of coal mining robots in underground mines is an urgently needed scientific and technological solution for upgrading China's and even the world's coal energy industry. The working face needs a shearer, hydraulic support, a scraper conveyor, and other equipment for coordination. The deep integration of intelligent technology with factors such as "humans, machines, the environment, and management" in the workplace is the core content of intelligent coal mines. This paper puts forward an advanced framework for robot technology systems in coal mining, including single robots, robotized equipment, robot crowds, and unmanned systems. The framework clarifies the common key technologies of coal mining robot research and development and the cross-integration with new technologies such as 5G, the industrial internet, big data, artificial intelligence, and digital twins to improve the autonomous and intelligent application of coal mining robots. By establishing a scientific and complete standard system for coal mining robots, we aim to achieve the customized research and development and standardized production of various types of robot. A specific analysis is conducted on the research progress of common key technologies such as the explosion-proof design, mechanical system innovation, power drive, intelligent sensing, positioning and navigation, and underground communication of coal mining robots. The current research and application status of various types of coal mining robots in China are summarized. A new direction for future coal mining robot research and development is proposed. Robotic mining systems should be promoted to enhance the overall intelligence level and efficiency of mining equipment. To develop human–machine environment-integrated robots to improve the autonomy and collaboration level of coal mining robots, the digital twinning of the entire mine robot system should be accelerated; the normalized operation level of coal mine robots should be improved; research on coal mining robots, shield support robots, and transportation robots should be performed; intelligence should be achieved in fully mechanized mining faces; and equipment shield support for fully mechanized mining faces should be provided. The practical process of implementing coal mining robotization is summarized in this paper, and the technical and engineering feasibility of the coal mining machine population is verified. [ABSTRACT FROM AUTHOR]

Seismic methods are extensively used in coal mining for expanding resource discoveries and definition as well as for mine monitoring. However, the use of borehole seismic methods is relatively uncommon due to the high cost of borehole seismic acquisition using conventional downhole tools. The introduction of distributed acoustic sensing (DAS), which uses optical fibres to record seismic data, has dramatically increased the cost-effectiveness of borehole seismic methods. Fibre-optic cables are inexpensive and, once deployed in a borehole, can be abandoned or used later for further monitoring of the subsurface. The case study presented here concerns the use of DAS to record a 3D VSP (vertical seismic profiling) for coal seam exploration in Queensland, Australia. This study trialled effective strategies for deploying cables into boreholes and demonstrated how this technology could be incorporated into the standard coal exploration process. The final processing results produced a high-resolution 3D seismic cube where the coal seams below the basalt cover are clearly identifiable around the boreholes. Permanent installation of the fibre-optic cables into a set of boreholes provides immediate benefits of 3D seismic imaging and can create additional value in utilising these sensors for further discrete or continuous subsurface measurements, including stability monitoring of underground workings and detection of methane accumulations. [ABSTRACT FROM AUTHOR]

Accurate and reliable pose estimation of boom-type roadheaders is the key to the forming quality of the tunneling face in coal mines, which is of great importance to improve tunneling efficiency and ensure the safety of coal mine production. The multi-laser-beam target-based visual localization method is an effective way to realize accurate and reliable pose estimation of a roadheader body. However, the complex background interference in coal mines brings great challenges to the stable and accurate segmentation and extraction of laser beam features, which has become the main problem faced by the long-distance visual positioning method of underground equipment. In this paper, a semantic segmentation network for underground laser beams in coal mines, RCEAU-Net, is proposed based on U-Net. The network introduces residual connections in the convolution of the encoder and decoder parts, which effectively fuses the underlying feature information and improves the gradient circulation performance of the network. At the same time, by introducing cascade multi-scale convolution in the skipping connection section, which compensates for the lack of contextual semantic information in U-Net and improves the segmentation effect of the network model on tiny laser beams at long distance. Finally, the introduction of an efficient multi-scale attention module with cross-spatial learning in the encoder enhances the feature extraction capability of the network. Furthermore, the laser beam target dataset (LBTD) is constructed based on laser beam target images collected from several coal mines, and the proposed RCEAU-Net model is then tested and verified. The experimental results show that, compared with the original U-Net, RCEAU-Net can ensure the real-time performance of laser beam segmentation while increasing the Accuracy by 0.19%, Precision by 2.53%, Recall by 22.01%, and Intersection and Union Ratio by 8.48%, which can meet the requirements of multi-laser-beam feature segmentation and extraction under complex backgrounds in coal mines, so as to further ensure the accuracy and stability of long-distance visual positioning for boom-type roadheaders and ensure the safe production in the working face. [ABSTRACT FROM AUTHOR]

Understanding the mechanical properties of coal is crucial for efficient mining and disaster prevention in coal mines. Coal contains numerous cracks and fissures, resulting in low strength and challenges in preparing standard samples for testing coal fracture toughness. In engineering, indicators such as the hardness coefficient (f value) and Hardgrove grindability index (HGI) are straightforward to measure. Various experiments, including drop weight, grinding, uniaxial compressive strength and three-point bending experiments, were conducted using notched semi-circular bend (NSCB) specimens and particle sizes of 1–2 mm/0.425–1 mm. Theoretical and experimental results indicate that the hardness coefficient of coal and rock is proportional to the crushing work ratio and inversely proportional to the mean equivalent diameter. Moreover, the square of the fracture toughness of coal and rock is directly proportional to the crushing work ratio, inversely proportional to the newly added area, directly proportional to the mean equivalent diameter and directly proportional to the hardness coefficient. The Mode-I fracture toughness of coal and rock can be rapidly determined through the density, the equivalent diameter after crushing and the elastic modulus, with experimental verification of its accuracy. Considering that smaller particle sizes exhibit greater resistance to breakage, the distribution mode of new surface areas after particle breakage was established, influenced by the initial particle size and the energy of a single broken particle. This study can assist in quickly and accurately determining the fracture toughness of coal. [ABSTRACT FROM AUTHOR]

Coal, extensively used in many countries across various industries, particularly as a fuel in the energy sector, poses significant environmental challenges due to process-related implications and their complex characteristics. A notable obstacle arises from its heterogeneous and complex submicron–nano-molecular structure, often leading to operational issues that are challenging to predict. This research aims to comprehensively assess the environmental impact of bituminous coal sourced from the Barapukuria Coal Mine (NW Bangladesh). This study focuses on elucidating the intrinsic properties of coal, with specific attention to its thermal behavior, structural composition, and surface morphology, aiming to understand the implications for energy production. Advanced techniques, such as TGA/DTG, CHNS-O, XRD, FTIR, XRF, ICP-OES, XPS, SEM with EDX, and TEM, were employed. Rigorous experimentation and analysis provided valuable insights into combustion and pyrolysis processes, illuminating the release of environmentally hazardous pollutants and their negative consequences associated with the utilization of Barapukuria coal for energy generation. Thermogravimetric analysis indicates coal bond breakdown at 573–933 K, releasing gases and liquids during the breakdown stage, resulting in mass loss from moisture evaporation, protogenic gas release, and volatile matter loss. Despite being of the bituminous type, the coal exhibits a mean carbon concentration of 78.24% and a low sulfur content of 0.42%, signifying relative environmental friendliness compared to high-sulfur coals, which is crucial for preventing acid rain. The average higher heating value (31.04 ± 0.74 MJ kg−1) and calorific value (30.20 ± 0.95 MJ kg−1) indicate that the studied coals have high energy potential. This study also suggests that optimizing thermochemical conversion for power generation may enhance energy efficiency and mitigate potential environmental impacts. The research findings contribute to the scientific understanding of coal thermal properties, serving as a foundation for informed decision-making in energy production strategies that prioritize both efficiency and environmental sustainability. [ABSTRACT FROM AUTHOR]

Outburst of coal and gas is a major hazard in underground coal mining where coal seam gas content/pressure is high. A cone‐shaped cavity is often observed in the coal seam after bursting, implying the likely mechanical structure being formed during outburst propagation. Although the mechanism for outburst initiation and propagation is very complex, mining‐induced fracturing and damage of the coal material is an essential component. This paper investigates the mechanical conditions that are essential to initiate fractures around a spherical cavity, a simplified form of the cone‐shaped outburst cavity. The cavity is assumed to be situated in an infinite isotropic homogeneous elastic body under internal gas pressure and far‐field hydrostatic compressive stresses as a further simplification for analytical investigation. The analytical conditions under which circumferential and radial fractures can initiate around the cavity are formulated, based on extensional strain criterion for fracture initiation. Low internal pressure on the cavity surface and high far‐field compression lead to circumferential fractures. In contrast, high internal pressure and low far‐field compression lead to radial fractures. Subsequent numerical simulations with FRACOD3D and FRACOD, the 3D and 2D in‐house fracture simulation codes, were carried out to investigate fracture patterns around a cavity and inclusion. The simulation results confirmed the analytical results, including fracture shapes and the size of fractured zone. These results provide a new angle to understand the complex mechanism of outbursts. [ABSTRACT FROM AUTHOR]

This study presents a case of weakly consolidated strata developed in Dananhu No.7 coal mine. Using a combination of numerical simulation, field measurement comparison, and the critical hydraulic gradient criterion, we investigate the overburden failure and the risk possibility of water–sand mixture inrush during excavation. The following are the principal findings: (1) Weakly consolidated rocks have poor physical characteristics, particularly when they are mudded and disintegrated after encountering water, which may become a favorable source of water–sand inrush; (2) The water-conducting zone develops to a height of 160.5 m with a crack-mining ratio of 15.29 times, extending upward to Toutunhe Formation aquifer. The predictions are consistent with measurements in adjacent mines with similar geological conditions; (3) Cracks without larger subsidence are developed at the front edge of the mining direction, and some parallel stepped cracks behind the goaf could be easily observed. Ground subsidence along the goaf center finally displays a symmetrically wide-gentle U shape; (4) The critical hydraulic gradient of Toutunhe Formation aquifer, aquifer above 3# coal seam, and aquifer of 3#–7# coal seam in Xishanyao Formation is 1.314, 1.351, and 1.380, the actual value is 0.692, 2.089, and 7.418 accordingly. It is inferred water–sand mixture outburst will not occur in Toutunhe Formation aquifer, while the potential risk exists in the aquifers of Xishanyao Formation. Through drainage and depressurization projects, a water–sand mixture outburst accident does not occur during excavation. This study reveals the overburden failure characteristics and the initiation mechanism of water–sand inrush in weakly cemented strata, as well as the internal relationship between them, which provides new research ideas for safe operation in other mining areas with similar geological conditions. The research work has certain practical guiding significance. [ABSTRACT FROM AUTHOR]

In view of the problem of poor coupling adaptability and easy rib spalling of coal wall in large mining height comprehensive mining, based on the effective inhibition effect of face guard mechanism on coal wall spalling, the structural characteristics and bearing capacity of different structural forms of the face guard mechanism are compared and analyzed. According to the surrounding rock adaptability of the face guard mechanism, established a numerical analysis model for rigid-flexible coupling of the face guard mechanism under different spalling forms. In order to accurately simulate the stress state of the protective mechanism, a variable stiffness spring damping system is used to replace the hydraulic cylinder. The load-bearing performance and response characteristics of the face guard mechanism under rib spalling coupling conditions were analyzed by applying uniform normal load and impact load to the face guard. The findings indicated that, the integral-type face guard mechanism has a better effect on suppressing rib spalling. When the face guard mechanism bears the static load of the coal wall, the entire response process of the face guard jack can be divided into three stages: initial support, increasing resistance bearing, constant resistance bearing; both the impact load position and the coupling state of the rib spalling will affect the characteristics of force transmission at the face guard mechanism's hinge point, the hinge point between the extensible canopy and the primary face guard is most sensitive to biased load. The research results can provide reference for optimizing the face guard mechanism of large mining height hydraulic support and improving the reliability of coal wall support. [ABSTRACT FROM AUTHOR]

High-pressure air storage is an important part of a gas storage system. Abandoned coal mine roadways can provide a large number of air storage spaces. The geological conditions of coal mines in different areas vary, such as depth, surrounding rock grade, in situ stress state, and surrounding rock permeability, which directly affect the mechanical behavior and air tightness of roadway surrounding rock under high internal pressure. Therefore, the suitable internal pressure must be selected for abandoned roadways with different geological conditions. In this study, the numerical simulation software FLAC3D was used to calculate the stress, deformation, plastic zone volume, and pore pressure of surrounding rock of an abandoned roadway under 5–10 MPa internal pressure. Results show that some differences exist in the suitable internal pressure of the abandoned roadway under different geological conditions. When the in situ stress state was σH > σh > σv or σH > σv > σh, the suitable internal pressure of grade I, II, and III surrounding rocks was 5–7 and 8–10 MPa at the depth greater than 200 and 300 m, respectively; the suitable internal pressure of grade IV and V surrounding rocks was 5–6, 7–9, and 10 MPa at the depth greater than 200, 300, and 400 m, respectively. When the in situ stress state was σv > σH > σh, the suitable internal pressure of grade I, II, III, IV, and V surrounding rocks was 5–7 and 8–10 MPa at the depth greater than 300 and 400 m, respectively. Surrounding rock permeability can be used to evaluate the air tightness of roadway surrounding rock under high-pressure air. The surrounding rock permeability that can meet the sealing requirements of compressed air energy storage (CAES) caverns is less than 1 × 10−14 m2, which are low-permeability strata. Low-permeability hard rock should be selected as much as possible. The research results provide a theoretical basis for the determination of internal pressure and the sealing evaluation of an abandoned coal mine roadway used for gas storage cavern. [ABSTRACT FROM AUTHOR]

Real-time microseismic observations are extensively used in underground hard rock mines. However, microseismic monitoring in coal mines is not common. In this study, the features of microseismic (MS) event waveforms were discussed under conditions of thin-layered sedimentary media. The possibility of source mechanism evaluation was considered for the MS event recorded in coal mine. Moment tensor (MT) inversion of the waveforms can be challenging due to influence of thin-layered medium structure. Splitting of shear SH- and SV-waves is one of the characteristic features that affect MS records in coal mines. The effect of splitting was demonstrated using real microseismic data collected by an underground seismic array installed in the Polosukhinskaya coal mine, Russia. Velocities of shear SH- and SV-waves were estimated from travel times. The results reveal significant variations in shear wave velocities composed of a radial anisotropy of 75%, thus confirming the importance of a thin-layered model for moment tensor inversion. The thin-layered model was built for geological conditions at the Polosukhinskaya coal mine and synthetic seismograms were generated using QSEIS (Pyrocko OS). A full moment tensor of a single typical event was found employing the layered 1D velocity model. [ABSTRACT FROM AUTHOR]

Algae growth can be carried out in treated mine waters, providing biomass and helping to achieve the standards for water discharge. However, efficient separation of algae from the aqueous medium is crucial. The present work investigated the stability of Scenedesmus sp. in treated acid drainage from coal mining and assessed the harvesting of microalgae via coagulation/flocculation and dissolved air flotation (DAF). Successful algae growth was achieved, with cells remaining suspended in the water at a wide range of pH values, requiring the use of reagents for destabilization/aggregation. Algae coagulation/flocculation was attained with the use of tannin or ferric chloride associated with an anionic polymer flocculant at a pH of 8.0 ± 0.1. When combined with the flocculant, both tannin and the inorganic coagulant proved effective in enhancing floc stability and hydrophobicity for the DAF process. In summary, this operational approach facilitated algae biomass recovery and significantly reduced turbidity in the treated water. Finally, a schematic diagram illustrating the algae cultivation and harvesting process is presented, offering a practical alternative to acid mine drainage (AMD) treatment refinement associated with algae biomass production. [ABSTRACT FROM AUTHOR]

Microbial residual carbon is an important component in soil carbon pool stability. Here, we tested soils collected from the early (first year, R1), middle (10 years, R10), and long-term (30 years, R30) stages of reclamation in a coal mining area in China. Two treatments with straw materials, namely maize straw + soil (S+M) and wheat straw + soil (S+W), were used for a decomposition experiment. The glucosamine and muramic acid contents were assessed. Accumulation of microbial residual C and its contribution to soil organic carbon (SOC) were analyzed at various intervals. Straw incorporation resulted in higher amino sugar accumulation than that of the control. The amino sugar content was considerably higher in R30 than that in R10 and R1; S+M and S+W showed average increases of 15 and 4%, respectively, compared to the control after 500 days. The total microbial and fungal residual C contents under S+M and S+W treatments were substantially higher than those of the control on days 33, 55, and 218 in R30. The contributions of soil microbial residues to SOC at R1, R10, and R30 were 73.77, 71.32, and 69.64%, respectively; fungal residues contributed significantly more than bacterial residues. The total amino sugars and microbial residual C content increased with increasing reclamation period. The addition of maize straw promoted the accumulation of microbial residual C, especially in the early stages of reclamation. Therefore, the addition of maize straw improved the stability of microbial carbon sources in coal mine reclamation soils. [ABSTRACT FROM AUTHOR]

The technology of CO2 geological storage and CH4 intensive mining (CO2-ECBM) in coal seams integrates greenhouse gas emission reduction and new fossil energy development and has great development prospects. The CO2 injection, CO2 sequestration mechanism and storage capacity, and CH4 stimulation effect constitute the core content of the effectiveness of CO2-ECBM, among which CO2 injection is the most critical. Traditional seepage analysis methods often struggle to tackle flow-related issues influenced by microscale effects and intricate channels. This paper highlights the advantages of employing lattice Boltzmann (LBM) numerical simulations to study CO2 seepage behaviors when teaching a Rock Mass Seepage Mechanics Course. This course primarily covers topics such as the pore structure of rock, unstable liquid seepage, gas seepage theory and related subjects. Its goal is to provide students with a solid theoretical foundation to address the complexities of fluid seepage in pours media encountered in practical scenarios. A novel LBM-based methodology was employed to estimate the CO2 seepage capacity by incorporating the effects of different concentrations of [Bmin]Cl solution (0 wt%, 1 wt%, 3 wt%, and 5 wt%). The CO2 velocity distribution cloud map of each coal sample was simulated; the average velocity distribution curve of each coal sample was obtained; and the velocity profile of the seepage channel of each coal sample was described. This study can provide theoretical guidance for the technology of CO2 geological storage and CH4 intensive mining in coal seams. [ABSTRACT FROM AUTHOR]

The China–Pakistan Economic Corridor is a featured project of China's Belt and Road Initiative that is creating new resource frontiers in Tharparkar, Pakistan. Centered around coal mining and energy production, these new sites of resource extraction and their infrastructures have sparked dissensus throughout the Desert district of Sindh, Pakistan. Our analysis draws on research on socio-technical imaginaries and Rancière's thoughts on political change and aesthetics. In doing so, we examine how political dissensus is represented though graffiti and works in contrast to the socio-technical imaginaries represented by the state in public signage. The differences, we suggest, represent socio-technical counter imaginaries that form a politics that disrupts the established socio-political order embedded within the political goals of the China–Pakistan Economic Corridor. These counter imaginaries have important implications for the creation of just and equitable opportunities for people impacted by the emerging coal extraction and power generation complex. Our ethnographic approach provides a street-level analysis of the politicization of imagined socio-technical futures in the Tharparkar desert and emerging energy resource frontiers. [ABSTRACT FROM AUTHOR]

In view of the problem strong rock pressure is easy to occur in coal seam mining in western gully terrain. Based on the coal seam mining conditions in the gully area under the compound key strata of Zhujiamao Coal Mine, the methods of similar simulation, theoretical calculation and analysis, numerical simulation and field measurement are adopted. The dynamic structure model of the key strata of the gully is constructed, and the mechanism and prevention and control measures of the strong rock pressure in the gully area of the working face under the compound key strata are analyzed. The research shows that the upper slope section of the gully area first undergoes rotary deformation, and then the chain structure formed by the broken block occurs sliding instability and impacts inferior key strata, resulting in strong rock pressure behavior in the working face. The calculation formula of the first breaking step distance of the main key strata rotation deformation and sliding instability during the movement of the overlying strata is derived. The calculation results show that the initial rotation deformation and sliding instability breaking step distances are 27 and 142 m, respectively, which are in good agreement with the support crushing at 145 m of the first gully. Using 3DEC numerical simulation, the stress of the second gully is reduced by 3.8 MPa after pressure relief, which verifies the position of strong rock pressure calculated by the formula and provides a theoretical basis for subsequent hydraulic fracturing. According to the mechanism, the comprehensive prevention and control measures of strong rock pressure in gully terrain are put forward. The support resistance of the working face is calculated to be 10,011 kN by the support resistance formula, and the ZY11000/14/34D hydraulic support is used. The working resistance of the calculated dangerous area after hydraulic fracturing is basically lower than 30 MPa, and the control effect is good. It has reference significance for coal seam mining through gully terrain. [ABSTRACT FROM AUTHOR]

With the engineering background of the gob‐side entry of panel SA1104 in Heiyanquan Coal Mine, the deformation characteristics and control technology of the surrounding rock for gob‐side entry with small pillar in gently inclined coal seam have been studied by field observation, numerical simulation, and theoretical analysis. The study show that: (1) The surrounding rock has obvious asymmetric deformation characteristics, the roof subsidence on the solid coal side is larger than that on the small coal pillar side; the deformation of small coal pillar side rib is more significant than that of the solid coal side rib, which is concentrated in the middle and upper part, and slip deformation occurs at the upper sharp corner; the middle part of solid coal side rib exhibits prominent deformation; and floor heave is shifted to the small coal pillar side. (2) The stress concentration zone on the small coal pillar side is located 1.9 m from the high rib, while the stress concentration zone on the solid coal side is located 4.1 m from the low rib. The difference in the rib‐to‐rib peak stress is 4.2 MPa, and the stress concentration on the solid coal side is larger than that on the small coal pillar side. (3) Poor physical and mechanical properties of the surrounding rock, high in‐situ stress, and high deterioration degree of the surrounding rock structure are the main internal causes of the entry deformation; strong mining disturbance, arbitrary support parameters, and large section sizes are the main external causes of the entry deformation. (4) The asymmetric combined support program is proposed, featuring "non‐equidistant cable + inclined bolt on the roof, bolt extension + cable supplement on the small coal pillar side rib, and bolt encryption on the solid coal side rib", and it had a positive on‐site application effect. [ABSTRACT FROM AUTHOR]

In coal mines, the effective extraction of relief gas and the prevention of dynamic disasters depend on accurate predictions of the spatial distribution of mining stress in the overlying rock. However, at present, the prediction of stress relief and concentration zones based on operational experience or empirical modeling differs significantly from actual measurements in the field. The fundamental problem is the difficulty in modeling the transfer mechanism of the mining overburden load under the influence of key strata. In this study, a mechanical model of the spatial distribution of the mining stress field based on the structure of overburden key strata was established. The model demonstrates that the key strata are the main bearing bodies of the overlying rock, both before and after the fracture, and the overburden rock load can be transferred to the coal and rock mass around the stope through the key strata in the fracture and bending subsidence zones, thus forming a mining stress field. Equations for calculating the plane distributions of mining stress under the key strata at different horizons and abutment pressures on the stope were established, and a spatial distribution prediction method for the mining stress field based on the overburden key strata structure was proposed. The study area was the Gaojiapu Coal Mine, where it was found that the key stratum of the 400.45 m thick Luohe Formation sandstone bore most of the overlying rock load and transferred the load to the coal and rock mass around the stope. This load distribution is the root cause of a high concentration and wide influence range of mining stresses, leading to serious deformation of the main roadway and frequent dynamic disasters. The mining stress concentration was maximized at a mining length of 1458 m × 1458 m. [ABSTRACT FROM AUTHOR]

The stress concentration caused by the presence of the remaining coal pillar in the overlying goaf can easily cause large deformation of the roadway in the lower seam and other problems. To solve this problem, the reasons for stress concentration caused by the remaining coal pillar in the overlying goaf were analyzed. A hydraulic fracturing method for relieving stress concentration has been proposed. By using hydraulic fracturing technology to remove the hanging roof on both sides of the coal pillar and weaken the coal pillar system, high stress is transferred to the goaf. The degree of stress concentration in coal pillars and surrounding rock of roadway can be reduced by 47% and 26%, respectively. This method can also solve the stress concentration problem of the remaining ore pillar in the overlying goaf of the metal ore. This method has been applied in the coal mine. The deformation of the surrounding rock of the test roadway after hydraulic fracturing has been reduced by more than 60%. [ABSTRACT FROM AUTHOR]

Globally, coal is a critical energy source, and the profits of related enterprises are highly related to changes in the coal price. A robust coal purchasing cost forecasting method may enhance the coal purchasing strategies of coal‐consuming enterprises and obtain key information for reducing global carbon emissions. However, forecasting the price of coal is a challenging task due to the noise and high random fluctuation of coal price data. To overcome these obstacles, this research proposes a novel forecasting method combining data decomposition, semisupervised feature engineering, and ensemble learning to forecast coal prices. Initially, the Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN) method is employed to decompose the coal price series to reduce the complexity. Second, considering the fluctuation of coal price is influenced by various factors (such as transportation cost and coal mine production), the proposed system incorporates an adaptive data fusion module to fuse data from multiple sources. Finally, a stacking‐based ensemble learning model is adopted in the method to increase the forecasting accuracy by combining the forecasting results of multiple models. The Bohai‐Rim Steam‐Coal Price Index was used to validate the proposed method, and the result of the case study shows that the proposed method provides superior performance than the other nine baseline models in all measured indices. The outcomes of ablation tests indicate the precision of each algorithm is improved by combining CEEMDAN, which proves that the decomposition algorithm is necessary. [ABSTRACT FROM AUTHOR]

To facilitate the efficient exploration and development of coalbed methane of the Longtan Formation in the Guxu coal mining area, Sichuan, it is essential to evaluate the reservoir characteristics of the main production layers. In this study, scanning electron microscopy, low-temperature liquid nitrogen adsorption experiments, high-pressure mercury pressure experiments, and isothermal adsorption experiments were conducted to investigate the reservoir characteristics of favorable coalbed methane reservoirs. The results indicate that the main coal seams in the Longtan Formation are medium-to-high ash content anthracite with a well-developed pore–fracture system. The pore size distribution exhibits both unimodal and bimodal types, while the pore morphology includes impermeable pores closed at one end, open permeable pores, and ink bottle-shaped pores. It shows that the middle part of Longtan Formation acts as an enrichment zone for coalbed methane, which is characterized by a stronger adsorption capacity, high Langmuir volume, high gas content, and high gas saturation distribution. The pH value, mineralization degree, and hydrogen–oxygen isotope of the produced water in the main coal seams indicate that the enrichment zone is typically located in a stagnant flow zone with a reducing environment and favorable storage conditions. [ABSTRACT FROM AUTHOR]

A considerable number of coal mines employed room and pillar mining in the last century in northern China, where the goaf remained stable for a period of time; however, with the increased exposure of coal pillars, their collapse may gradually increase. The stability assessment of these old rooms and pillar goafs is challenging due to their concealment, irregular mining patterns, and the long passage of time. The methodology developed in this study, based on "space-sky-earth" remote sensing such as InSAR to trace historical deformation, the UAV observation of current surface damage, and comparison of mining spaces, can rapidly detect on a large scale the collapse of old goafs and the trend of damage. This study is conducted with an example of a coal mine in Yulin, Northern China, where obtained quantitative surface deformation values were integrated with qualitative surface damage interpretation results, followed by a yearly analysis of the overlying rock movement in accordance with the underground coal mining process. The results show that from 2007 to 2021, corresponding surface deformation and damage occurred following mining progress. However, the room and pillar goaf areas had not undergone any surface deformation, nor had there been incidents of landslides or ground fissures; therefore, it was speculated that no roof collapse had occurred in this region. The surface deformation and damage associated with underground coal mining are complex and influenced by the coal seam occurrence, mining methods, strata lithology, terrain slope, temporal evolution, and anthropogenic modifications. These phenomena are representative of the coal mining area, and this methodology can provide a reference for similar endeavors. [ABSTRACT FROM AUTHOR]