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Introduction: In the excavation engineering of tunnels and mines in the western cold region, the unloading failure zone is mainly caused by stress release. This study aimed to investigate the deformation and failure mechanism of frozen weakly cemented sandstone (FWCS) when the initial principal stress σ3 was 3, 6, or 10 MPa. Methods: A conventional triaxial compression test and a triaxial unloading test with an unloading rate of 0.05 MPa/s were carried out. Based on the experimental data and mathematical analysis methods, the non-linear criterion was constructed and analyzed. The microfracture characteristics of the damaged surface were studied by scanning electron microscopy (SEM). Results: The results show that compared with conventional triaxial compression and room temperature triaxial compression tests, the strength and plastic deformation characteristics of FWCS during unloading were significantly weakened, with transverse deformation and volume strain increased, showing obvious dilatancy characteristics. Unloading reduced the cohesion of FWCS, increased the internal friction angle, and increased the risk of rock failure. Macroscopic and microscopic analysis revealed the failure mechanism of FWCS. The unloading stress ratio was introduced to establish relationships. A non-linear criterion based on the Mohr–Coulomb strength criterion was established, with the power function strength criterion being more accurate in describing the failure of FWCS. Discussion: This study provides valuable insights into the mechanical properties and failure mechanism of FWCS under unloading conditions, which is beneficial for the excavation engineering of tunnels and mines in the western cold region. [ABSTRACT FROM AUTHOR]

To reveal the rock burst mechanism, the stress and failure characteristics of coal-rock strata under different advancing speeds of mining working face were explored by theoretical analysis, simulation, and engineering monitoring. The relationship between energy accumulation and release was analyzed, and a reasonable mining speed according to specific projects was recommended. The theoretical analysis shows that as the mining speed increases from 4 to 15 m/d, the rheological coefficient of coal mass ranges from 0.9 to 0.4, and the elastic energy of coal mass accumulation varies from 100 to 900 kJ. Based on the simulation, there is a critical advancing speed, the iteration numbers of simulation are less than 15,000 per mining 10 m coal seam, the overburden structure is obvious, the abutment pressure in coal mass is large, and the accumulated energy is large, which is easy to cause strong rock burst. When the iteration number is greater than 15,000, the static force of coal mass increases slightly, but there is no obvious rock burst. Based on engineering monitoring, the mining speed of a mine is less than 8 m/d, and the periodic weighting distance is about 17 m; as the mining speed is greater than 10 m/d, and the periodic weighting distance is greater than 20 m; as the mining speed is 3–8 m/d, and the range of high stress in surrounding rock is 48 m; as the advancing speed is 8–12 m/d, and the high-stress range in surrounding rock is 80 m. Moreover, as the mining speed is less than 8 cut cycles, the micro seismic energy is less than 10,000 J; as the mining speed is 12 cut cycles, the micro-seismic energy is about 20,000 J. In summary, the advancing speed is positively correlated with the micro seismic event; as the mining speed increases, the accumulated elastic energy of surrounding rock is greater, which is easy to cause rock burst. The comprehensive analysis indicates the daily advance speed of the mine is not more than 12 cut cycles. [ABSTRACT FROM AUTHOR]

The document discusses the complexities of rock mechanics, focusing on stability issues in rock engineering and the conditions leading to rock failure. It highlights the importance of interdisciplinary approaches in addressing geotechnical challenges and presents the latest advancements in complex rock mechanics, including mining engineering, underground excavation, and computer technologies. The research papers cover a wide range of topics, such as mining-induced seismicity, hydraulic fracturing, and the mechanical properties of rocks, offering valuable insights into practical engineering applications and theoretical frameworks. [Extracted from the article]

The transient electromagnetic method (TEM) has a wide range of applications in the hydrogeological exploration of mining engineering. This method is highly sensitive to groundwater responses and provides reliable data for the prevention of water-related disasters, such as sudden water surges and gushes. However, there are currently a lack of comprehensive and systematic analyses and summaries regarding the characteristics of magnetic source transient electromagnetic coil devices. Based on the fixed characteristics of the field source, this paper categorizes magnetic source transient electromagnetic coil devices into fixed-source devices and moving-source devices. It provides an in-depth introduction and analysis of the working principles, technical characteristics, existing applications, and development trends of these two types of devices. This study provides important references for the selection and application of magnetic source transient electromagnetic coil devices. In the future, the development of magnetic source transient electromagnetic devices will focus on deeper measurement depths, higher lateral resolution, non-contact coupling, and efficient detection, moving towards multifunctionality, automation, and intelligence. This paper can provide a technical reference for the selection of magnetic source transient electromagnetic coil devices and their application in hydrogeological exploration of mining engineering. [ABSTRACT FROM AUTHOR]

In coal mining operations, it is often challenging to control the deformation of the roadway in front of the working face. The excessive stress from the surrounding rock of the working face and the difficulties in caving the goaf roof have led to a prominent factor that hinders safe and efficient production in coal mines. For this reason, a mechanical model of the stress field in the advance roadway of the working face is established, and the stress evolution law of the surrounding rock before and after cutting the roof of the roadway is analyzed. Key parameters such as cutting depth, cutting angle, and hole spacing are determined through theoretical calculation, numerical simulation with 3DEC numerical software, and field testing. A kind of roof cutting and pressure relief techniques (TCPAF) for enhanced roadway safeguarding in advance mining face is proposed, and its effectiveness is verified through field testing. The results indicate that the stress on the low-stress side of the leading roadway remains slightly increased, while on the high-stress side, stress decreases significantly, optimizing the stress environment of the surrounding rock. In addition, the research results provide a scientific basis for similar conditions of roadway deformation. [ABSTRACT FROM AUTHOR]

The accurate prediction of unconfined compressive strength (UCS) in rock samples is critical for the successful planning, design, and implementation of mining and civil engineering projects. UCS is crucial in assessing the stability and durability of rock masses, which directly influences the safety, efficiency, and cost-effectiveness of construction and excavation operations. Here's a refined version of your text for enhanced clarity and flow: in this part, the execution of the proposed model was compared for both single and hybrid configurations. Hybrid models included support vector regression (SVR) combined with the Seahorse Optimizer (SVSH) and SVR combined with the COOT optimization algorithm (SVCO). For training, 70% of the UCS dataset was utilized, while the remaining 30% was equally divided between testing (15%) and validation (15%). For the model evaluation, several metrics were considered in this work, including the R2, RMSE, WAPE, MAE, and RAE, which ensure fairness in the analysis. The closer the R2 value comes to 1, the better the performance. The error metrics should be close to 0 for better accuracy. From Table 2, one can observe that the result of the standalone SVR model gave an RMSE of 6.213 during training and 9.454 during testing, hence showing poor performance. However, the inclusion of optimization algorithms significantly improved the performance of the SVR framework. Among the hybrid models, the SVSH model had the best performance, with an R2 value of 0.998 and an RMSE of 1.261 during training. The SVCO model performed moderately, with an R2 value of 0.988 during training. [ABSTRACT FROM AUTHOR]

Aiming to address the challenges of determining the coal pillar's width and managing the significant deformation of the surrounding rock in the deep gob-side entry driving, the limiting equilibrium zone theory, employing the operational area of Dongpang Mine 21110 as the engineering setting, states that a coal pillar's appropriate width in the gob-side entry driving falls between 7.9 and 9.8 m. The pattern of vertical stress distribution and the extent of the plastic zone in the roadway for coal pillar widths of 7.0 m, 8.0 m, 9.0 m, and 10.0 m are analyzed, respectively, investigated using the numerical simulation method of FLAC3D. The acceptable coal pillar width in the deep gob-side entry driving is 8.0 m. Combined with the roadway surrounding rock borehole inspection results, the fracture development condition of the roadway's full-face surrounding rock is determined, and the asymmetric aberration characteristics, with significant surrounding rock damage depth at the coal pillar flank location, are obtained. Based on the theoretical calculations, an integrated proposal for a "non-symmetrical bolt and cable anchor" coupling support scheme for the surrounding rock in the gob-side entry driving is put forward. This was applied at the Dongpang coal mine site. Engineering practice shows that leaving an 8.0 m coal pillar width and adopting the "non-symmetrical bolt and cable anchor" support system design can control the deformation of the surrounding rock in the track entry at a reasonable range, which ensures the stability of the surrounding rock in the gob-side entry driving. [ABSTRACT FROM AUTHOR]

Underground coal excavation has caused a series of geological disasters and environmental problems, especially coal mining subsidence. Backfill-strip mining, which combines the advantages of strip mining and backfill mining, can reduce subsidence and improve the recovery rate of coal. Therefore, predicting the impact of backfill-strip mining on the surface environment and strata structure is essential for the better development of backfill-strip mining technology. Here, a scientific and comprehensive mechanical model is creatively proposed. The mechanical model is divided into two systems at the main key strata (MKS): the lower strata of the MKS are regarded as a rectangular plane mechanical model on the Winkler foundation, comprising spaced filling bodies and coal pillars, and the upper strata of the MKS are regarded as a space-layer mechanical model. First, the subsidence function of the MKS is proposed. Then, this function is transmitted to the space-layer mechanical model through the interface. Finally, the mechanical model is used to predict the subsidence of the strata and the surface. The feasibility of the model is verified by numerical simulation and similar material simulation, and the characteristics of strata movement are analyzed. Using the mechanical model, the influences of geological and mining conditions on strata movement are discussed. This provides theoretical guidance for the study of strata movement and mechanisms in backfill-strip mining. [ABSTRACT FROM AUTHOR]

Based on the engineering example of Linsheng coal mine, this paper uses TF1M3D computer simulation platform to systematically analyze the process of smoke flow spreading and air flow disorder disaster from the perspective of the whole mine network, and puts forward corresponding plans and measures. A small scale similar experiment was carried out to study the updraft flow fire in the mine. Through the analysis of the collected experimental data, the variation law of the air volume of the fire source in the main air path, side branch road and total air path with different air volume and the variation characteristics of the temperature at the monitoring point with time were obtained under different air volume conditions, and the critical air volume was fitted as 1.65 m3·s− 1. The CAD digital stereoscopic model of Linsheng mine was established, and the TF1M3D simulation platform was used to simulate the mine fire under normal ventilation condition. The preset fire source point of the conveyor belt roadway in the first west district of Linsheng coal mine was used to observe the change of air volume during the fire process.The smoke flow reversal phenomenon would occur when the fire occurred in the first west district. The reversed smoke flow will flow to the 503 face and cause contamination. In order to inhibit the reversal of smoke flow, the emergency plan is proposed to increase the number of fan rotation and set fire doors in appropriate places, which can effectively inhibit the diffusion of smoke and improve mine disaster resistance. [ABSTRACT FROM AUTHOR]

ABSTRACT To study the stress distribution law under different mining times and spaces of the protected coal pillar in the isolated working face, this paper takes a coal mine in Shanxi as the engineering background and adopts numerical simulation and theoretical analysis to obtain the stress distribution law of protecting coal pillar in the isolated working face during the tunneling period and the mining period of the working face, and proves the reasonable size of protecting coal pillar. The results show that the vertical stress and maximum principal stress increase correspondingly with the decrease of the protective coal pillar size under both stages, and the minimum value of the minimum principal stress occurs on the 8 m protective coal pillar; The values of the principal stress ratio and the principal stress deflection angle do not differ greatly in the protection of the coal pillar, and the fluctuation of the values is mainly concentrated in the vicinity of the back‐mining roadway; The second invariant of bias stress (J2) is mainly concentrated in the protective coal pillar near the side of the extraction zone, when the size of the protective coal pillar is reduced to 10 m, the J2 on the side of the extraction zone and the J2 on the side of the roadway are connected, and the whole protective coal pillar is under the influence of J2, which is basically the same as the damage pattern of the plastic zone; Based on the formula of limit balance theory to calculate the elastic core width of different sizes of protective coal pillars, and combined with the results of numerical simulation analysis, it finally concluded that the reasonable size of the protective coal pillar of this isolated island working face is 15 m. [ABSTRACT FROM AUTHOR]

Rock masses are formed through long-term, complex geological processes, and the presence of joints significantly reduces their strength and increases their deformation. Rock bolts effectively enhance the strength and stability of rock masses and are extensively utilized for reinforcement. According to field investigations, a significant portion of the damage to bolted rock masses stems from shear deformation at joint surfaces. Moreover, roughness affects friction and surface contact, thus influencing the shear behavior between rock and rock bolts. This study considers two crucial factors affecting the shear characteristics of bolted rock joints: joint surface roughness and normal stress. Using the Particle Flow Code discrete element numerical method, the Barton standard joint profile lines were input to establish numerical models of both unbolted and bolted rock joints for direct shear tests. Results reveal that the peak shear stress and stiffness of both unbolted and bolted rock joints increase with rising normal stress and joint roughness coefficient. The peak shear stress and stiffness of bolted rock joints are notably higher than those of unbolted ones, with a maximum increase of 17.5%. Crack development in bolted rock joints occurs in stages of rapid, slow, and stable development, whereas no distinct slow development stage is observed in unbolted rock joints. Additionally, micro cracks in both unbolted and bolted rock joints are primarily tensile cracks, originating around the joint surface and extending outward with increasing shear displacement. These findings offer valuable insights into the microscopic shear mechanics of bolted rock joints and provide practical references for engineering design and applications in rock reinforcement projects. [ABSTRACT FROM AUTHOR]

Unlicensed taxis seriously disrupt the transportation market order, and threaten passenger safety. Therefore, this paper proposes a method for identifying unlicensed taxis based on travel characteristics. First, the vehicle mileage and operation time are calculated using traffic surveillance bayonet data, and variance analysis is applied to identification indicators for unlicensed taxis. Secondly, the mathematical model for identifying unlicensed taxis is established. The model is validated using the Hosmer–Lemeshow test, confusion matrix and ROC curve analysis. Finally, by applying methods such as geographic information matching, the spatiotemporal distribution characteristics of suspected unlicensed taxis in a city in Anhui Province are identified. The results show that the model effectively identifies suspected unlicensed taxis (ACC = 99.10%). The daily average mileage, daily average operating time, and number of operating days for suspected unlicensed taxis are significantly higher than those for private cars. Additionally, the suspected unlicensed taxis exhibit regular patterns in their travel origin–destination points and temporal distribution, enabling traffic management authorities to implement targeted regulatory measures. [ABSTRACT FROM AUTHOR]

In the process of deep coal seam mining, the problem of coal–gas compound disasters is increasingly prominent, with the safe and efficient extraction of gas serving as the key to disaster reduction. A deep coal seam gas extraction project is a complex coupled system involving multiple physical fields, such as stress fields, gas flow fields, and energy. Constructing a systematic theoretical framework of multiphysics field coupling is crucial for improving the safety and efficiency of gas extraction. This paper examines all existing multiphysics field coupling theories. It then suggests a theoretical modeling framework that is based on three important scientific issues: the coal deformation law, the gas flow law, and the coal porosity and permeability spatiotemporal distribution law. We further analyze the application and development of the model in typical coal seam gas extraction engineering on this basis. Finally, this paper points out the shortcomings of the current research and looks forward to the future research directions for the coupled coal and gas multiphysics field model, aiming to provide a theoretical basis and guidance for the model's construction and application in gas extraction engineering. [ABSTRACT FROM AUTHOR]

Due to the difficulty in predicting the occurrence of rockburst in deep mining areas,this paper proposes that the use of Peridynamics to analyze the mechanical characteristics of coal-rock composite structures under loading conditions from the perspective of energy, Determine the impact tendency of coal rock composite structures by combining rock elastic deformation energy index (WET) and rock impact energy index (WCF); Use Lammps software to simulate the loading of composite structural materials and compare and verify with experimental results, to more accurately determine the tendency of rockburst occurrence in different coal-rock composite structures.The results indicate that after the specimen reaches the yield stress, the sample exhibits an "X" shaped failure. The coal body has a significant impact on the overall model's fragmentation, and different combination states and ratios can affect the degree of damage in the coal-rock composite structure. which has important theoretical value for rock mechanics research. The research results can reduce the occurrence of rockburst accidents, the difficulty of mine support, and the cost of mining engineering, as well as improve mine safety levels. [ABSTRACT FROM AUTHOR]

Analyzing geological profiles is of great importance for various applications such as natural resource management, environmental assessment, and mining engineering projects. This study presents a novel geostatistical approach for subsurface geological profile interpolation using a fractional kriging method enhanced by random forest regression. Using bedrock elevation data from 49 boreholes in a study area in southeast China, we first use random forest regression to predict and optimize variogram parameters. We then use the fractional kriging method to interpolate the data and analyze the variability. We also compare the proposed model with traditional methods, including linear regression, K-nearest neighbors, ordinary kriging, and fractional kriging, using cross-validation metrics. The results indicate that the proposed model reduces prediction errors and enhances spatial prediction reliability compared to other models. The MSE of the proposed model is 25% lower than that of ordinary kriging and 10% lower than that of fractional kriging. In addition, the execution time of the proposed model is slightly higher than other models. The findings suggest that the proposed model effectively captures complex subsurface spatial relationships, offering a reliable and precise solution for performing spatial interpolation tasks. [ABSTRACT FROM AUTHOR]

The increasing use of lithium-containing materials highlights the urgent need for their recycling to preserve resources and protect the environment. Lithium-containing slags, produced during the pyrometallurgical process in lithium-ion battery recycling, represent an essential resource for lithium recovery efforts. While multiple methods for lithium recycling exist, it is crucial to emphasize environmentally sustainable approaches. This study employs dry forced triboelectrification (FTC) to recover valuable components from slag powder, commonly known as engineered artificial minerals (EnAMs). The FTC method is used to change the charge of the target material and achieve a neutral state while other materials remain charged. The downstream electrostatic separator enables the charged particles to be separated from the target material, which in this study is lithium aluminate. The results show that the method is effective, and lithium aluminate can be successfully enriched. [ABSTRACT FROM AUTHOR]

Ground-based Interferometric Synthetic Aperture Radar (GB-InSAR) is a valuable technique for monitoring deformation of landslides. GB-InSAR can construct high-resolution 2D images in a range-doppler plane. However, it is difficult for geo-engineers who are unfamiliar with radar monitoring geometry to interpret the results. Geometric mapping method has been applied to the co-registration of terrain models and radar images for the deformation zonation, but the mismatching correction with GB-InSAR and terrain model is not fully investigated by existing researches. To address this issue, this paper proposes a method exploiting an optimum linear transformation based on ground control points (GCPs). The proposed method was evaluated on simulated data and a field campaign in an open pit mine. The deformation mapping result of the method was verified by a collapse event. The method proposed in this paper has an RMSE value ranging from 0.502 to 0.720 m (@700 m average monitoring range) when the average density of the terrain point cloud is 0.5 m. Although this method cannot accurately evaluate the antenna footprint vector deflection parameters, it can meet the needs of coarse matching calibration in relatively flat slope sub-target areas of open-pit mines for engineering applications. [ABSTRACT FROM AUTHOR]

The efficient production of γ-aminobutyric acid (GABA) at a neutral pH remains a challenge due to the pH sensitivity of glutamate decarboxylase (GAD) enzymes. Our study addressed this limitation by identifying and engineering GAD enzymes with high activity under neutral conditions. Through gene mining, we discovered a wild-type GAD from Enterococcus faecalis (EfGAD) with high activity at pH 7.0 and, using zero-shot (ZS) predictor-guided mutagenesis and C-terminal truncation, we developed an EfGAD variant with a significantly enhanced catalytic efficiency. This variant demonstrated a 1.3-fold increase in GABA production (~300 g/L) from monosodium glutamate (MSG) compared to the wild-type EfGAD in 5 L bioreactor experiments. The ability to operate at a neutral pH without the need for acidic conditions reduces production costs and facilitates scalability. Our findings underscore the potential of integrating machine learning tools for enzyme optimization and provide a sustainable approach to GABA biosynthesis using MSG as a substrate. [ABSTRACT FROM AUTHOR]

Slags generated from pyrometallurgical processing of spent Li-ion batteries are reservoirs of Li compounds that, on recycling, can reintegrate Li into the material stream. In this context, γ-LiAlO2 is a promising candidate that potentially increases recycling efficiency due to its high Li content and favorable morphology for separation. However, its solidification kinetics depends on melt compositions and cooling strategies. The Engineered Artificial Minerals approach aims to optimize process conditions that maximize the desired solid phases. To realize this goal, understanding the coupled influence of external cooling kinetics and internal kinetics of solid/liquid interface migration and mass and thermal diffusion on solidification is critical. In this work, the solidification of γ-LiAlO2 from a Li2O-Al2O3 melt is computationally investigated by applying a non-equilibrium thermodynamic model to understand the influence of varying processing conditions on crystallization kinetics. A strategy is illustrated that allows the effective utilization of thermodynamic information obtained by the CALPHAD approach and molecular dynamics-generated diffusion coefficients to simulate kinetic-dependent solidification. Model calculations revealed that melts with compositions close to γ-LiAlO2 remain comparatively unaffected by the external heat extraction strategies due to rapid internal kinetic processes. Kinetic limitations, especially diffusion, become significant for high cooling rates as the melt composition deviates from the stoichiometric compound. [ABSTRACT FROM AUTHOR]

Copyright of Marmara University Journal of Turkology / Marmara Türkiyat Araştırmaları Dergisi is the property of Marmara University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Low-alloy CrNiMo cast steels are often used in the caterpillar boards of excavators in mining engineering machinery due to their good mechanical properties and low cost. Three CrNiMo cast steels with different carbon contents (0.20%, 0.29%, and 0.35% by weight) were developed in this work. The mechanical properties of ingots of these cast steels can be optimized by heat-treated quenching and tempering (QT) and surface induction hardening (QTIH). The wear behavior of QT and QTIH specimens was evaluated under dynamic load and ring block conditions. The results show that the QT specimens exhibit a good mechanical performance and wear resistance. Compared to the QT specimens, the wear resistance can be further improved by QTIH treatment. The wear weight loss of QTIH specimens decreased by 42.7% and 73.2% under dynamic load and ring block wear tests, respectively. Additionally, the strength increased while plasticity and toughness decreased with increasing carbon content. Notably, when the carbon content is 0.29%, the CrNiMo cast steel exhibits an excellent combination of strength, ductility, and wear resistance. [ABSTRACT FROM AUTHOR]

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

Copyright of Environmental & Social Management Journal / Revista de Gestão Social e Ambiental is the property of Environmental & Social Management Journal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Geology & Exploration is the property of Xian Research Institute of China Coal Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Geology & Exploration is the property of Xian Research Institute of China Coal Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract In coal mining operations, the stable operation of hydraulic supports is crucial for ensuring mine safety. However, the nonlinear, non-stationary characteristics and noise interference in hydraulic support pressure data pose significant challenges for anomaly detection and fault diagnosis. This study proposes an anomaly detection and failure identification method based on Gated Recurrent Unit Autoencoder (GRU-AE), aimed at achieving anomaly detection in hydraulic support pressure data and equipment failure early warning. Through in-depth analysis of data from two coal mines in China, we systematically evaluated the model’s key parameters. The study revealed that window size had a limited impact on model performance, with a window length of 144 demonstrating optimal comprehensive performance in both anomaly detection and failure mode identification. The study also investigated the effectiveness of teacher forcing techniques. Although this technique can accelerate model convergence, it may lead to training instability and reduced generalization capability, requiring careful consideration in practical applications. Our proposed Recurrent Reconstruction Network model demonstrated excellent performance in complex coal mine hydraulic support data, effectively identifying anomalous regions and potential equipment failure characteristics while revealing potential deviations between model predictions and actual data, demonstrating its superior learning capability for periodic data patterns and equipment failure characteristics. Experimental results validated the effectiveness of the GRU-AE model in hydraulic support pressure anomaly detection and equipment fault diagnosis, providing an innovative technical solution for coal mine safety monitoring.

This is an article in the field of mining engineering. Aiming at the raw ore mined from Hushugou iron mine, Hushugou copper mine and Xiaoliugou tungsten mine of Jiuquan Iron and Steel Co., Ltd., the experimental study of pre separation and tailing is carried out by using X-ray intelligent sorter, and good treatment effect is obtained. Through the analysis of experimental results, the separation effect of intelligent photoelectric pre separation technology is not only related to the performance of the equipment, but also depends on the mixing amount of surrounding rock and the nature of ore in the mining process. It is analyzed that the ore structure affects the effective dissociation degree of useful minerals and gangue minerals, which affects the surface radiation, transmission and image color separation of X-ray, and determines the difficulty and effect of intelligent photoelectric beneficiation equipment on ore separation.

This is an article in the field of mining engineering. With the increasing application of cyclone in the field of mineral processing, the influence of its operating factors on the separation performance has been paid more and more attention in the production process. At present, various researches on the separation performance of cyclone have been widely reported, but they are generally limited to the structural factors of cyclone, and do not consider the effects of operational factors (inlet pressure P, dispersion concentration Ci) and the interaction between factors on the separation performance. In order to explore the influence of cyclone operating factors on separation performance, response surface analysis was applied to design experiments to optimize the mathematical models of cyclone main diameter Dc and operating factors on cyclone classification efficiency Ef and classifier size Dm, and explore the interaction between them, which can achieve the best separation performance regulation of cyclone. Through the analysis of 17 groups of test results by design expert, the following results are obtained: classification efficiency fitting formulaandgrading granularity fitting formula. The 3D surface response analysis shows that the main diameter, inlet pressure and inlet concentration have a significant effect on the classification efficiency and particle size of Dc> Ci >P, and for the classification efficiency and particle size, the interaction between Dc and Ci and between Dc and P is relatively strong, while the interaction between Ci and P is weak.

This is an article in the field of mining engineering. The process mineralogy is the prerequisite for flotation. The influence of ore fineness and the degree of dissociation of the target mineral monomer on ore floatability can be used to guide the selection of suitable flotation conditions. A systematic study of the process mineralogy of a copper-cobalt ore was carried out using the methods of X-ray fluorescence analysis, X-ray powder diffraction analysis, scanning electron microscopy, and electron polarizing microscopy. Based on the process mineralogy studies, the flotation tests were carried out, at the condition of grinding fineness of -0.074 mm 70%, with a process of one roughing-two scavenging-two cleaning closed-circuit flowsheet. The sulfide concentrate with the grade of Cu 21.04%, Co 9.83% and the recovery of Cu 92.88%, Co 92.84% was achieved.

The isolated island face determination is an important basis for coal mine safety supervision. In order to accurately determine the island attribute of the working face, a method for determining the island attribute of working face under a typical conditions is proposed based on the coal column size effect analysis. Combined with a mine engineering conditions, the size effect of the coal column in the west and north wing of the 305 working face was analyzed by theoretical analysis and engineering analogy. The results showed that: the coal column bodies of the west wing and north wing of the 305 working face did not cause large-scale serious damage of the coal rock mass due to excessive stress concentration. The leading support pressure range of the 305 working face was less than 120 m, which was significantly smaller than the width of the coal column in the north wing. The width of the extreme balance zone of the lateral support pressure of the 305 working face is 52.3 m. The coal column body in the west wing of the 305 working face is wider than the sum of the two extreme balance zones. The west and north wings of the 305 working face are not gob areas. The 305 working face is not an island working face.

Abstract The drilling rate index (DRI) of rocks is important for optimizing drilling operations, as it informs the choice of appropriate methods and equipment, ultimately improving the efficiency of rock excavation projects. This study presents a hybrid machine learning approach to predict the DRI of rocks accurately. By integrating grey wolf optimization with support vector machine (GWO-SVM), random forest (GWO-RF), and extreme gradient boosting (GWO-XGBoost) models, the aim was to enhance predictive accuracy. Among these, the GWO-XGBoost model exhibited superior predictive performance, achieving a coefficient of determination (R²) of 0.999, mean absolute error (MAE) of 0.00043, root mean square error (RMSE) of 1.98017, and severity index (SI) of 0.0350 during training. Testing results confirmed its accuracy with R² of 0.999, MAE of 0.00038, RMSE of 1.80790, and SI of 0.0312. Furthermore, the GWO-XGBoost model outperformed the other models in terms of precision, recall, f1-score, and multi-class confusion matrix results for each DRI class. The GWO-RF model also demonstrated high accuracy, ranking second, while the GWO-SVM model showed comparatively lower performance. This research aims to advance rock excavation practices by providing a highly accurate and reliable tool for DRI prediction. The results highlight the significant potential of the GWO-XGBoost model in improving DRI predictions, offering valuable intuitions and practical applications in the field.

This is an article in the field of mining engineering. The development of aluminum industry is subject to decisive factors such as bauxite resources. As a large aluminum industry country in the world, after nearly two decades of rapid development, domestic bauxite resources are becoming increasingly scarce, and the contradiction between ore supply is becoming increasingly prominent. How to ensure the sustainable supply of China's bauxite resource demand and ensure the sustainable and high-quality development of China's aluminum industry is an urgent problem to be solved. The author believes that in the environment of establishing and improving the economic system of green and low-carbon circular development and promoting high-quality development, in addition to continuously increasing the development and utilization of foreign bauxite resources, we can also strengthen the comprehensive utilization of domestic low-grade bauxite resources, restrict the export of primary aluminum products measures such as transnational transfer of aluminum production capacity and promoting small equity and multi-point investment in overseas aluminum industry, and improve the guarantee ability of sustainable supply of bauxite resources in China.

This is an article in the field of mining engineering. Under the background of "double carbon" and "ballast stone" of refractory gold ore resources, pre-oxidation is an effective pretreatment method for efficient gold extraction from refractory gold ores. Destroying the finely impregnated gold inclusions, and eliminating or avoiding the passivation, robbing or secondary wrapping of gold by harmful substances, are the key and bottleneck problems to determine the gold recovery rate in refractory gold ores. Understanding the phase transformation and reconstruction evolution of gold-bearing minerals during pre-oxidation process is critical for inclusions destruction directly and gold leaching. In this article, the typical characteristics of refractory gold ores and existing pre-oxidation techniques were outlined, and the research advances in phase transformation and reconstruction of gold-bearing inclusions in roasting oxidation, hot-press oxidation, biological oxidation, chemical oxidation and other pre-oxidation processes were summarized. The result shows that the gold-bearing sulfides are mainly transformed into Fe oxides (or As oxides) and sulfate (or arsenate) by pre-oxidation. However, due to the coupling effect of multiple factors such as oxidation temperature, atmosphere or oxygen concentration, pH value, redox potential, Bacterial characteristics, etc., sulfides may also be converted into elemental sulfur, sulfur oxide, thiosulfate, jarosite and scorodite. In addition, jarosite, iron oxide and calcium sulfate are the main solid matters leading to the secondary package of gold. Pre-oxidation process and microscopic mechanisms, such as neutral thermobaric oxidation with low temperature and pressure, bacteria domestication with thermophilic, alkalophilic and arsenic-resistant properties, process enhancement of bacterial oxidation under multi-factor coupling, green and efficient oxidant screening, and chemical oxidation based on multi-field coupling, etc., still need to be deeply researched. The coupling relationship and regulation among ore characteristics, process reaction of pre-oxidation, phase transformation and reconstruction of gold-bearing materials and gold recovery rate are the research hotspots and difficulties in the green and efficient pre-oxidation field for refractory gold ores in the future.

This is an article in the field of mining engineering. Magnesite in China is rich and good in quality. Its mineral quantity and grade rank the first in the world. It is widely used as the raw material for the production of magnesium oxide in industry. The change of microstructure of magnesite during calcination is the key to performance the properties of magnesia products. Taking this as the starting point, the technical progress of preparing high-performance magnesia products from magnesite is summarized firstly. Then, according to the restrictive factors of industry development, this article analyzes the future development trend of this field briefly.

Rockburst is a common dynamic geological disaster in underground mining and tunneling engineering, characterized by randomness, abruptness, and impact. Short-term evaluation of rockburst potential plays an outsize role in ensuring the safety of workers, equipment, and projects. As is well known, microseismic monitoring serves as a reliable short-term early-warning technique for rockburst. However, the large amount of microseismic data brings many challenges to traditional manual analysis, such as the timeliness of data processing and the accuracy of rockburst prediction. To this end, this study integrates artificial intelligence with microseismic monitoring. On the basis of a comprehensive consideration of class imbalance and multicollinearity, an innovative modeling framework that combines local outlier factor-guided synthetic minority oversampling and an extremely randomized forest with C5.0 decision trees is proposed for the short-term evaluation of rockburst potential. To determine the optimal hyperparameters, the whale optimization algorithm is embedded. To prove the efficacy of the model, a total of 93 rockburst cases are collected from various engineering projects. The results show that the proposed approach achieves an accuracy of 90.91% and a macro F1-score of 0.9141. Additionally, the local F1-scores on low-intensity and high-intensity rockburst are 0.9600 and 0.9474, respectively. Finally, the advantages of the proposed approach are further validated through an extended comparative analysis. The insights derived from this research provide a reference for microseismic data-based short-term rockburst prediction when faced with class imbalance and multicollinearity. [ABSTRACT FROM AUTHOR]

Anchor rock bolts are among the essential support components employed in coal mine support engineering. Measuring the axial load of the supporting anchor bolts constitutes an important foundation for evaluating the support effect and the mechanical state of the surrounding rock. The existing methods for measuring the axial load of rock bolts have difficulty meeting the actual demands in terms of accuracy and means. Therefore, we propose a novel inverse method for determining the axial load of rock bolts. On the basis of the dynamic relationship between the axial load of the anchor bolt and the strain of the plate, a calculation model for the inverse analysis of the axial load from the plate strain is presented, and it is verified and corrected through finite element analysis and indoor physical experiments. By combining the calculation model with the digital image correlation method, a low costinversion of the axial load of the anchor bolt in actual support engineering is achieved. The experimental results demonstrate that the average errors of the load inversion of anchor bolts in three different states via the theory and method proposed in this paper are less than 8.8% (4 kN), 3.6% (3.2 kN), and 14.7% (5.5 kN), respectively, and the average error of the axial load of the rock bolts in the proposed method is only 4.23 kN. It possesses relatively high accuracy and can be effectively applied in the actual production processes of mines. [ABSTRACT FROM AUTHOR]

Rockburst, one of the leading types of disaster in mining and rock engineering causing serious injuries and the loss of property, frequently occurs, involving various features and complex evolutionary mechanisms. Compared to rockbursts occurring at mining faces, those occurring in main roadways cause more serious problems for mine production. This paper first analyzes the characteristics of rockbursts in main roadways using two case studies involving the Gaojiapu and Cuimu coal mines. The causes of rockbursts in main roadways were studied using microseismic monitoring, energy density cloud maps, and seismic velocity tomography. During the mining of the 22306 working face in the Cuimu coal mine, targeted measures, such as deep-hole blasting of the roof strata and deep-hole blasting of the coal seam, were implemented to prevent rockbursts in the main roadways. The effectiveness of these measures was verified through long-term analysis of tremor activities. The study found that the influence of mining at two working faces on both sides of main roadways was significantly greater than that from a single-sided working face. The intensity of the tremor activities occurring near the main roadways was correlated with the distance from the working face to the main roadways. The closer the working face was to the main roadways, the stronger the tremor activities were near the main roadways. According to the distribution range of the tremors, the influence area of working face mining exceeded 800 m, with tremors distributed linearly along the main roadways. Even five months after the completion of working face mining, there were still a large number of tremors near the main roadways, which gradually disappeared after another five months. Mining activities were the main reason for the occurrence of main roadway rockbursts and the stress concentration within the main roadways themselves was another reason for the occurrence of rockbursts. The influence of working face mining could be reduced by deep-hole blasting of roof strata and the stress concentration within main roadways themselves could be reduced by large-diameter drilling. Those joint preventive measures effectively prevented the occurrence of rockbursts in main roadways. This study is of important theoretical and practical significance for further studies of rockburst mechanisms and prevention in regard to main roadways in coal mines, and the findings are significant in terms of the enhancement of safety in coal mines. [ABSTRACT FROM AUTHOR]

Rockmass in deep mining is highly susceptible to large-scale collapses under high stress and blast-induced disturbances, leading to casualties and economic losses. To investigate the evolution characteristics of goaf instability and the types of seismic sources that induce instability, an experiment on goaf instability was designed under uniaxial compression conditions based on actual mining operations. The entire experimental process was monitored using digital image correlation analysis and acoustic emission monitoring. By calculating the digital speckle field on the surface of the rock specimen during the experiment, the evolution characteristics of the deformation and strain fields from the beginning of loading to complete failure were analyzed. The study explored the dynamic behavior of cracks from initiation to propagation and eventually inducing large-scale collapse. The results show that the instability process of the goaf begins with the formation of tensile cracks. As stress increases, shear cracks occur in the specimen, leading to macroscopic failure. Furthermore, based on the differences in overall microfracture types measured by RA-AF characteristic parameters during specimen failure, large amplitude acoustic emission events corresponding to the formation of dominant macroscopic cracks were selected, and the focal mechanisms of these events were inverted. The results indicate that shear failure sources are significantly more prevalent than tensile failure sources in acoustic emission events leading to goaf instability. These findings can provide useful guidance for the support design and the prevention and control of rockmass instability disasters. [ABSTRACT FROM AUTHOR]

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With the increase in mining depth and intensity, dynamic disasters such as rockburst in mines are becoming more severe. Deep resource extraction is characterized by a high in-situ stress geological environment, closely associated with geological dynamic disasters. However, there is currently no quantitative analysis method for the correlation between the two. In this study, an elastic energy density calculation method is employed, considering the dissipative effect of the self-weight stress field on the tectonic stress field. The remaining energy, referred to as impact energy, is used to classify the risk of coal seam impact, providing a computational method for rapid assessment of impact risk before mining production. The proposed calculation method is compared with 22 mine impact engineering practices in the literature, showing accurate predictions for 21 mines. Since measuring in-situ stress and coal seam physical and mechanical properties is a preliminary work in coal seam extraction, the comprehensive analysis of these data holds significant research and practical value. [ABSTRACT FROM AUTHOR]

Deep underground galleries are used to access the deep biosphere in addition to mining and other engineering applications, such as geological disposal of radioactive waste. Fracture networks developed in the excavation damaged zone (EDZ) are concerned with accelerating mass transport, where microbial colonization might be possible due to the availability of space and nutrients. In this study, microbial biofilms at EDZ fractures were investigated by drilling from a 350-m-deep gallery and subsequent borehole logging at the Horonobe Underground Research Laboratory (URL). By using microscopic and spectroscopic techniques, the dense colonization of microbial cells was demonstrated at the surfaces of the EDZ fractures with high hydraulic conductivity. 16S rRNA gene sequence analysis revealed the dominance of gammaproteobacterial lineages, the cultivated members of which are aerobic methanotrophs. The near-complete genomes from Horonobe groundwater, affiliated with the methanotrophic lineages, were fully equipped with genes involved in aerobic methanotrophy. Although the mediation of aerobic methanotrophy remains to be demonstrated, microbial O2 production was supported by the presence of genes in the near-complete genomes, such as catalase and superoxide dismutase that produce O2 from reactive oxygen species and a nitric oxide reductase gene with the substitutions of amino acids in motifs. It is concluded that the EDZ fractures provide energetically favorable subsurface habitats for microorganisms. [ABSTRACT FROM AUTHOR]

In order to reveal the failure morphology and mine pressure behavior of overlying strata during shallow buried close multi-coal seam mining, this research takes the Shenmu Zhangjiamao mining area as the engineering background, the study of overlying rock movement and mine pressure distribution law in shallow and close coal seams was carried out. The results show that: with the gradual mining of 2−2 coal seam, the support stress in front and back of the working face increases first and then decreases, and the compaction strength of the collapsed overburden in the middle of the mined-out area increases gradually. With the mining of 2−3 coal seams, the displacement of the direct roof of the lower mined-out area and the rock layer of the upper compaction area increases gradually. With the increase of interlayer spacing, the peak stress in the concentrated stress area on both sides of the 2−3 coal seam decreases gradually. The compaction stress of overlying strata in the upper mined-out area decreases gradually, and the peak value of compaction stress in the middle of the lower goaf increases gradually. Through the measured results of the borehole stress sensor and separation instrument, the obvious influence range of the advance support pressure of the working face is about 40 m. The research results can provide practical experience for similar coal seam group mining in other mines, and can also be used to study the mining pressure behavior of inclined close distance multiple coal seams. [ABSTRACT FROM AUTHOR]

The drilling rate index (DRI) of rocks is important for optimizing drilling operations, as it informs the choice of appropriate methods and equipment, ultimately improving the efficiency of rock excavation projects. This study presents a hybrid machine learning approach to predict the DRI of rocks accurately. By integrating grey wolf optimization with support vector machine (GWO-SVM), random forest (GWO-RF), and extreme gradient boosting (GWO-XGBoost) models, the aim was to enhance predictive accuracy. Among these, the GWO-XGBoost model exhibited superior predictive performance, achieving a coefficient of determination (R²) of 0.999, mean absolute error (MAE) of 0.00043, root mean square error (RMSE) of 1.98017, and severity index (SI) of 0.0350 during training. Testing results confirmed its accuracy with R² of 0.999, MAE of 0.00038, RMSE of 1.80790, and SI of 0.0312. Furthermore, the GWO-XGBoost model outperformed the other models in terms of precision, recall, f1-score, and multi-class confusion matrix results for each DRI class. The GWO-RF model also demonstrated high accuracy, ranking second, while the GWO-SVM model showed comparatively lower performance. This research aims to advance rock excavation practices by providing a highly accurate and reliable tool for DRI prediction. The results highlight the significant potential of the GWO-XGBoost model in improving DRI predictions, offering valuable intuitions and practical applications in the field. [ABSTRACT FROM AUTHOR]

In the past five years, the number of articles related to ultrasonic mineral flotation has increased by about 50 per year, and the overall trend is on the rise. The most recent developments in ultrasonics for flotation process intensification are reviewed herein, including effects of ultrasound treatment on an aqueous slurry, improvement in flotation methods and technological processes, device development tracking, and application effects in mineral process engineering. At this point in time, there are pilot-scale flotation tests to evaluate the feasibility of ultrasonic pretreatment technology for industrial use to enhance residue flotation separation, and the results showed that the recovery rate of concentrate is increased by about 10%. Four aspects of ultrasonic flotation process improvement are summarized, namely, changing the ultrasonic parameters, the synergistic effect of ultrasound and reagents, the ultrasonic effect of particles with different-sized fractions, and application to new systems. In addition, the effect of ultrasonic flotation mechanisms is explored through a quadratic model and numerical simulation. The combination of ultrasonic flotation with other fields, such as magnetic fields, to enhance the separation efficiency and recovery of minerals is also a future trend. It is also proposed that ultrasonic flotation technology will be used with big data, industrial Internet of Things, and automatic control technology to achieve deep bundling, optimizing the flotation process by implementing remote monitoring and control of the flotation process. [ABSTRACT FROM AUTHOR]

The deep integration of computer field and coal mining field is the only way to coal mine intellectualization. A variety of artificial intelligence tools have been applied in open-pit and shallow coal mines. However, with the geometric increase of coal demand, the contradiction between supply and demand is becoming more and more serious, and the exploitation of resources from shallow layer (> 600 m) has become an inevitable trend. Well then, as a new engineering scene, the harsh conditions of "three high and one disturbance" seriously threaten the safety of personnel. The superposition of complex mining environment makes the number of input factors increase sharply, which leads to the application of artificial intelligence in deep coal mine roadway engineering. The guidance is not mature, the construction of various databases is missing, and there are still some problems in universality and applicability. To this end, this paper starts with the introduction of the operating characteristics of various artificial intelligence tools, and conducts a comprehensive study of the relevant high-level articles published in top journals. It systematically sorts out the research progress that has successfully solved the five directions of rock mechanics strength, surrounding rock stability, rock-burst, roof fall risks and micro-seismic events. While objectively evaluating the comprehensive performance of different tools, it also expounds its own views on key research and results. Literature review shows that whether as a development tool or a comparative model, the application of ANN in the field of coal mining is more than 98%, and it performs extremely well in the direction of surrounding rock stability and roof fall risk, with an accuracy rate of more than 90%. As the most mature direction of AI tools application, rock mechanical strength has experienced the development process from "SVM → ANN → DL → XGBoost → RF". The dataset is from small samples (< 100) to big samples (> 1000), and the R2 of tree-based models can be stabilized at more than 95%. The research on rock-burst prediction mainly focuses on field factors and micro-seismic monitoring data. Whether it is a small sample or a large-scale data model, the accuracy of BN remains above 85%. The prediction and evaluation of micro-seismic events is a new direction in recent years. The image processing and application of CNN is extremely important. The signal recognition and classification accounts for more than 90%, and the research potential of source location needs to be further explored. In general, the nature of the rock itself is the first choice for almost all influencing factors. At the same time, the update iteration of monitoring methods (micro-seismic, ground sound, separation, deformation, etc.) expands the development of the database, making it possible to obtain the data due to threat to life and cost of equipment, which is very difficult to obtain before. In the process of parameter selection at the input end, the method of combining lithology conditions, geological environment and monitoring data will gradually become the first choice for research. Finally, in the follow-up work collation and on-the-spot investigation, it mainly focuses on the existing problems of deep coal mines, explores the application potential of artificial intelligence in deep coal mine roadway engineering, puts forward the possible research focus and challenging problems in the future, and gives its own opinions. [ABSTRACT FROM AUTHOR]

Static crushing agent (SCA) offers advantages such as good safety, no harmful gases, and minimal vibration, making SCA ideal for rock crushing in mines or underground engineering. To scientifically implement the section expansion of mine roadway, the rock mechanical parameters, SCA expansion properties, and cracking behavior of surrounding rock were investigated using laboratory tests, numerical simulations, and field experiments. Results indicate that the smaller hole spacing of SCA improves the fracturing effect on rock mass, reduces the required fracture initiation stress and penetration stress, and the presence of a free surface aids in fracture development in the rock mass. Optimal borehole design parameters and spacing distributions of the SCA were determined, and corresponding construction techniques of roadway expansion were proposed. Field tests demonstrate that static crushing technology, under multi-row drilling conditions, is highly effective for rock roadway expansion projects. These findings provide valuable guidance for non-explosive expansion and other roof breaking treatment projects. [ABSTRACT FROM AUTHOR]