Search

This paper primarily explores the modeling method of n-level complex helical structures with coal mining machine cables as the research object. The paper first elaborately introduces the modeling method of n-level helix curves based on parametric equations and coordinate transformations, and compensates for the n-level helix curves with corrected pitch, which can obtain more accurate n-level helix curves and improve the accuracy of n-level helix curves modeling. Subsequently, based on this high-precision n-level helix curves modeling method, the paper elaborates on the method of solving pitch and twisting radius of multi-layer helical structure. Calculation scripts were written based on the above methods, which can be used to batch calculate the twisting radius and pitch of each layer structure in multi-layer structures when satisfying the conditions of in-layer tangency, inter-layer tangency, and extrusion deformation, and retain the actual results through logical judgment. Then, based on the above two methods, the paper developed a modeling method for braided structures based on piecewise functions containing fifth-order polynomials, which can effectively avoid the problem of insufficiently dense arrangement of braided lines and easy interference in traditional methods. Finally, a set of modeling tools was developed using C# and Python in Grasshopper to implement the modeling algorithm. Taking the MCPT-1.9/3.3 3120 + 170 + 4 * 10 coal mining machine cable as an example. The cable was modeled using both the method proposed in this paper and the traditional method. Comparative data shows that the method proposed in this paper can reduce errors by 3.31E6 times in the second-level and above helical structures. In addition this paper compares the standard line length, measured line length, and the line length established by the proposed model, showing that the relative errors are both less than 0.1941%. This paper provides a new, systematic, high-precision, and full-process cable modeling method, in which all parameters except the process parameters are accurately solved by equations. It lays a theoretical foundation for the high-precision simulation and intelligent sensing cables, which is of great significance for improving the safety, stability, and efficient development of the coal mining industry. The research results of the paper can not only be applied to the modeling of coal mining machine cables but also can be extended to the modeling of other complex multi-layer helical structures. [ABSTRACT FROM AUTHOR]

The scarcity of water resources and environmental pollution in the coal mining areas of western China severely restricts high-quality mine development and construction there. Treating mine water as a valuable unconventional water resource for large-scale processing and efficient utilization is a crucial approach. This paper discusses the current status of mine water treatment technology in this region and provides a systematic comparison and analysis of common and emerging treatment technologies for mine water containing suspended solids, high salinity, and fluoride. The paper extensively elaborates on the fundamental principles, process routes, and technical features of these technologies, citing typical engineering cases. It also outlines the challenges that mine water treatment in the coal mining areas of western China is likely to face in the future. Based on the current status of mine water resource utilization in China, various pathways forward are clarified. Finally, this paper presents a scientific reflection and proposed solutions for mine water treatment technology and resource utilization in the coal mining areas of western China, concluding with a prospective outlook on the future development of this field. [ABSTRACT FROM AUTHOR]

Green mining is the basic background of high-quality mining, and source reduction is the most important part, among which the optimization of working face height and length is the most active. How to control the working face parameters, reasonably evaluate the surface subsidence characteristics of the super-long working face, and identify the limit working face length and the surface discontinuous deformation threshold is particularly important. In order to solve the problem of irreversible damage to the surface caused by the mining process of the working face, this paper discusses the whole process of surface movement in the 8.8 m super-large mining height working face of Shangwan Coal Mine through field investigation, the maximum subsidence is 6.20 m, with a subsidence coefficient of 0.72. Combined with the inflection point trajectory, advancing degree and subsidence coefficient, the 0.9 coefficient of the working face subsidence basin boundary and the loss reduction strategy far from the limit working face threshold are proposed. The results show that the subsidence basin of 12,401 working face accounts for 34%, the continuous deformation area of surface accounts for 64%, and the influence area of discontinuous deformation area is within 10 times of mining height. With the help of borehole detection verification, the caving zone height within the coal seam overburden to be between 33.2 and 33.25 m and the fracture zone height between 118.08 and 132.83 m. Therefore, the caving ratio is about 3.8, and the fracture ratio is about 13–15, which provides a strong basis for the optimization design of working face and the timing of surface ecological management. [ABSTRACT FROM AUTHOR]

To solve the problem of controlling mining in the open-pit mine end slope fire-burned area, applying multivariate function fitting to the roof and floor modeling of multi-coal seam open pit mines, introducing the factor of coal quality changes in the fire-burned area, determining coal quality information at each location through proximate analysis of coal, to establish the net profit model of the mining area, it is determined the net profit of each mining position by numerical integration, the final mining position was determined without failure by calculating the slope stability based on the numerical simulation of strength reduction. Taking the Dananhu No. 2 open-pit mine in Hami, Xinjiang, China as the engineering background, the fire-burned area III within the southern end slope boundary of the first mining area is 240 m. It was finally determined that the optimal mining position is when the advancement degree is 182 m, the ultimate pit slope angle is 25°, the three-dimensional slope stability is 1.305, the profit is 671.96 million yuan, The deep boundary of the southern end slope fire-burned area of the slope is reduced by 58 m. This paper solves the problem of end slope mining in Dananhu No. 2 mine, and maximizes its net profit under the condition of ensuring safe production. [ABSTRACT FROM AUTHOR]

Rock burst disasters severely restrict the safe and efficient mining of coal. The fundamental cause of their occurrence is the concentration of stress within the coal mass. Stress monitoring in coal seam drilling is widely used as an effective method for rock burst monitoring. However, how to scientifically and reasonably set the critical values of early warning indicators that match the conditions of each mine has always been a key issue restricting the accurate prediction of rock burst by the drilling stress method. This paper adopts a method combining theoretical analysis and field practice to conduct research on the critical values of drilling stress early warning indicators. Based on perturbation response instability theory, a mechanical model for the occurrence of impact ground pressure has been established. Based on the instability theory of disturbance response, a mechanical model for the occurrence of impact ground pressure has been established, leading to the derivation of the expression for the near-field critical stress of impact ground pressure events. The theoretical formula for the critical value of drilling stress early warning indicators was obtained based on the difference between the critical stress of rock burst occurrence and the actual stress in the roadway. This formula includes the mechanical parameters of the coal mass and its propensity for rock burst, roadway support stress, mining depth, stress concentration coefficient, and the initial installation pressure of the stress gauge. They can be determined by the geological and mining technical conditions of each mine. This theoretical formula breaks the uniformity of the critical values for stress warning indicators in various mine drill holes, allowing each mine to scientifically determine its critical value based on its own conditions. This theoretical method has been applied to a high-stress mine in Shanxi, China, and the critical values of drilling stress early warning indicators were obtained. When the monitored stress exceeded the critical value, dynamic phenomena of anchor rod and cable fractures occurred in the roadway roof. The distribution of microseismic events also shifted towards the warning area, and the microseismic monitoring indicators reached the warning values. This confirmed the engineering feasibility of the critical values for drilling stress early warning indicators determined by the theoretical method. [ABSTRACT FROM AUTHOR]

In order to quantitatively calculate the critical depth and critical load of mines affected by rock burst, and to achieve effective prevention and control of rock burst in coal mines, this paper proposes a mechanical model for predicting the occurrence of rock burst in coal mine roadways based on catastrophe theory. Additionally, a theoretical calculation formula for initiating rock burst is derived. The first step was to establish a mechanical analysis model, which directly correlated with the in-situ stress, physical and mechanical characteristics of the coal-rock mass, and engineering structural parameters. Following this, a mechanical instability criterion was derived for the key load-bearing circle within the surrounding rock of the roadway. In the final step, the critical depth and load for rock burst initiation were verified for 25 distinct coal mines in China that were prone to rock burst hazards. The research results demonstrate that the discrepancy between the theoretically calculated critical depth and the actual measured statistical values was less than 35%. In addition, the difference between the theoretically determined critical depth and the value calculated by Pan Yishan was less than 32%. Notably, the ratio of the theoretically calculated critical load to the uniaxial compressive strength of the coal-rock mass ranged from 0.38 to 1.93. This aligns with empirical data on rock burst occurrences, as set out in the engineering classification standards for rock masses. These research outcomes substantiated the practical utility of the proposed theory, thereby laying a robust theoretical groundwork for the quantitative control of rock burst. [ABSTRACT FROM AUTHOR]

The TRIZ theory was used to accurately discover the problems to be solved in the design of roadway surrounding rock control technology. This paper tried to solve the complex issue of surrounding rock control in deep roadways from a new perspective. Based on the functional component analysis and causal axis analysis of the problem's primary reason, simultaneously, the surrounding rock control technology was optimized through technical contradiction analysis, physical contradiction analysis, and substance and field model analysis. As a result, a fully enclosed wire-shell support technology was proposed. Finally, taking the typical soft rock roadway engineering of Pansan Coal Mine in Huainan Mining Area, Anhui Province, China, as the engineering background, the engineering application and effect evaluation were completed. This paper provides a reference for controlling the instability of deep soft rock roadways in coal mines. A new idea of optimizing roadway support engineering based on TRIZ theory was proposed. [ABSTRACT FROM AUTHOR]

To build a digital twin model of intelligent longwall coal mining, this paper presents a new full-parameter position and attitude digital twin model of hydraulic supports. A full-parameter matrix describing the position and attitude of a support is established first. Then, the position and attitude digital twin model of a support based on this matrix is built. Afterward, a position and attitude digital twin model of the hydraulic support system in the workface is established using the Unity3D software and the Runge–Kutta algorithm as a motion calculation method. Finally, a simulation experiment is conducted based on the digital twin model of hydraulic supports, and results show its effectiveness. This digital twin model has the potential to control the hydraulic support system in future intelligent coal mining. [ABSTRACT FROM AUTHOR]

As mechanized open-pit coal mining intensifies, assessing and predicting slope stability has become increasingly important. To address the limitations of traditional mechanical calculations, numerical simulations, and physical experiments, this paper identifies the key factors impacting slope stability in open-pit mines and develops a multi-parameter sample data set. The study employs hyperparameters optimized using a Bayesian algorithm, introduces additional convolutional layers, and combines the Adam optimizer with dropout techniques to enhance the feature extraction and performance of one-dimensional convolutional neural networks (1D-CNN). This leads to a Bayesian-optimized one-dimensional convolutional neural network (B-1D MCNN) model for predicting slope stability.The study evaluates the classification performance and accuracy of various models for slope stability, including BP neural networks, genetic algorithm-optimized convolutional neural networks, 1D-CNN, and B-1D MCNN, using accuracy, precision, and F1-score as metrics. The analysis also examines the influence of factor indicators and training set length on the model's output to assess its generalization capabilities.The research findings suggest that: (1) the B-1D MCNN model for evaluating slope stability demonstrates the capability to accurately depict the nonlinear correlation between influencing factors and slope stability. (2) Compared with other models, the B-1D MCNN model has shown enhancements of 10.96% to 27.85%, 10.26% to 28.55%, and 8.98% to 25.05% in terms of Accuracy, F1-Score, and Precision, respectively. (3) As the length of the training dataset increases, the performance of the model improves accordingly. (4) The B-1D MCNN model shows a generalization power of 87.5%. [ABSTRACT FROM AUTHOR]

Intelligent computing is transforming safety inspection methods and response strategies in coal mines. Due to the significant safety hazards associated with mining excavation, this study proposes a multi-source data based predictive model for assessing gas risk and implementing countermeasures. By examining the patterns of gas dispersion at the longwall face, utilizing both temporal and spatial correlation, a predictive model is crafted that incorporates safety thresholds for gas concentrations, four-level early warning method and response strategy are devised by integrating weighted predictive confidence with these correlations. Initially tested using a public dataset from Poland, this method was later verified in coal mine in China. This paper discusses the validity and correlation of multi-source monitoring data in temporal and spatial correlation and proposes a risk warning mechanism based on it, which can be applied not only for safety warning but also for regulatory management. [ABSTRACT FROM AUTHOR]

With the deep extension of coal mining in China, fault water inrush has become one of the major disasters threatening the safety production of coal mine. Based on the control equations of steady state and non-Darcy seepage in fractured rock mass, the multi-parameter nonlinear dynamic seepage equations of fractured rock mass are established in this paper. Based on the nonlinear dynamics theory, the function of the state variable in the system is derived, and the influence of the gradual change of non-Darcy flow factors on the structural stability of seepage system is studied. The research achievements show that there are three branches in the equilibrium state of the seepage system. Specifically, the stability of the equilibrium state changes abruptly near the limit parameter. The seepage dynamic system of fractured rock mass has the delayed bifurcation, and the coal mine disaster such as fault water inrush occurs easily at the bifurcation point. The research results are of great significance to enrich the theory of fault water inrush in coal mine, and to reveal the disastrous mechanism of fault water inrush and guide its prevention and control technology in coal mine, which can provide the theoretical reference for predicting the water seepage stability in fractured rock mass. [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]

Coal mining machine drums are prone to damage and malfunction under extremely complex working conditions, which seriously affects the efficiency and safety of coal production. In this paper, based on the theory of coal rock cutting and virtual simulation technology, finite element models of drum cutting coal rock were established and then verified by physical experiments. Through simulation analysis, the dynamic reliability of the drum was studied from three aspects: load, stress and wear, and a mathematical model of drum load was established with respect to the traction speed and drum rotation speed; based on the orthogonal test, the optimal working parameters to improve the wear resistance of the drum were derived. The results of the study found that when the traction speed increases, the load on the drum increases, and when the drum rotation speed increases, the load on the drum decreases; when the traction speed is increased from 2 to 6 m/min, the stress on the pick body under different rotation speeds increases to different degrees, with an average increase rate of 27.394%; when the drum rotation speed is 90 r/min, the traction speed is 3 m/min, and the coal loading mode is projectile loading, the wear depth of the picks and spiral blades is relatively small. The research method and results of this paper can provide a reference for the selection of the drum working parameters. [ABSTRACT FROM AUTHOR]

In this paper, a thick plate structural mechanical model was established for the hard-thick rock strata in the Ordos region, which was characterized by the occurrence of high-energy strong earthquakes caused by the fracture of hard-thick rock strata. Subsequently, based on Vlasov's theory, the evolution process of hard-thick rock strata was analyzed. And the paper validated the analysis results using high-energy mine earthquake and surface subsidence data. The following conclusions were drawn: (1) The hard-thick strata in the cretaceous system will not be broken during the advancing and mining process of the test panel of the Shilawusu coal mine. (2) When the test panel is mined to a distance of two panel widths, no fracture occurred in the lower part of the hard-thick strata, because no separated space was formed. (3) When the test panel was advanced to about 856 m, the hard-thick strata have fractured in a vertical direction. (4) No high-energy mine earthquake event has occurred during mining at test panel, and the amount of surface subsidence is approximately 200 mm. (5) In the mining at test panel, two high-energy mining earthquakes occurred at 837 m, 1153 m away from the initial position of the panel, respectively, and the maximum amount of surface subsidence increased to 1397 mm, which accords with the results of the first and periodic breaks calculated by theory. The research results of this paper are of guiding significance for the study of the breaking law of hard-thick strata under similar engineering geological conditions and disaster pre-control. [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]

The continuous large deformation of the surrounding rock during gob-side entry driving in a 1000-m-deep mine requires frequent renovation of the mining roadway, seriously restricting the normal mining operations at the coal face. Taking 11,216 headgate of a coal mine as the engineering background, this paper expounds that the large deformation factors of the gob-side entry driving of a 1000-m-deep mine are stress-field factors dominated by high in-situ stress, side abutment pressure, front abutment pressure and tectonic stress, and stress-related factors dominated by coal body crushing, unreasonable support, large section size and broken narrow coal pillar. The two-stage pressurization of the surrounding rock of the section roadway of the mine is governed by the following fundamental law: After pressurization, the peak area of the original abutment pressure of the roadway transfers to the lower parts of the surrounding rock, resulting in an increased stress in the surrounding rock at the side of the roadway. A targeted cooperative control involving external anchor-internal unloading of the surrounding rock of the roadway during gob-side entry driving is proposed, and the pressure relief mechanism in the surrounding rock during the static and dynamic pressure stages of the hole-making process is elucidated: the hole-making space transfers the peak stress to the deep during the static pressure stage, and it transfers the high stress to the deep during the dynamic pressure stage. The pressure relief laws of the surrounding rock were analyzed for different hole-making parameters during the static and dynamic pressure stages of deep gob-side entry driving, the hole-making parameters of the 11,216 headgate were as follows: the hole-making depth, length, and spacing were 8, 4, and 3.2 m. A "four-in-one" double space monitoring method was developed to evaluate the control effect of the support structure on the surrounding rock. The results indicated that the surrounding rock deformation remained within a controllable range, the support structure did not experience any breakage or detachment throughout the service period, and the hole-making space played a pressure relief role. The successful application of this technology to control the large deformations in the surrounding rock of coal roadways in deep mines via gob-side entry driving is of great scientific significance. Highlights: The influencing factors of surrounding rock stability during gob-side entry driving in a 1000-m-deep mine are of two types: stress-field factors and stress-related factors. During gob-side entry driving, the two-stage pressurization of the surrounding rock in the 1000-m-deep mine is influenced by the adjacent gob and front mining. The collaborative control of the surrounding rock of the roadway of a 1000-m-deep mine during gob-side entry driving can be facilitated using external anchor-internal unloading. Clarified the principle of pressure relief during the static and dynamic pressure stages of gob-side entry driving in the 1000-m-deep mine. A capsule-like system can monitor the deformation of the nonvisible spaces in pressure relief holes. [ABSTRACT FROM AUTHOR]

Excessive strain energy accumulation in the coal seam is one of the essential conditions for rockbursts to occur. It is imperative to understand the parameters that affect the strain energy accumulation in retreating longwall mining to optimise the design and minimise rockbursts occurrences. In this paper, new analytical models were developed to calculate the strain energy accumulation considering the current state-of-the-art longwall machinery being used in the industry. Seven parameters, i.e., mining depth, length of the cantilever roof, coal seam thickness, thickness of the immediate roof, Young's modulus of coal and the roof, and Poisson's ratio of the coal seam, were identified as the parameters affecting the strain energy accumulation. A detailed statistical analysis of the parameters was conducted using the orthogonal testing method, which revealed that mining depth, Young's modulus of coal and the coal seam thickness significantly influence the strain energy accumulation within a 99% confidence interval. Highlights: An analytical model to calculate strain energy accumulation in longwall mining panels. Excellent agreement between analytical and numerical models. Parametric dominance was determined using the orthogonal testing method. Easy to use equations to calculate rockburst risk in longwall mining panels. [ABSTRACT FROM AUTHOR]

The Double-Yield (D-Y) model is a widely used method for predicting the mechanical properties of caved rock. However, determining the numerical simulation parameters for this model typically requires extensive trial and error. In this paper, a new approach for parameter inversion of the D-Y model is proposed and applied to a real case study involving repeated mining in multiple coal seams. The proposed framework combines FLAC3D, a finite element numerical simulation software, with a new computational tool developed using MATLAB® App Designer. By applying this framework to the case study, the accuracy and efficiency of parameter determination in the mining area are improved. In addition, a 3D finite element model of multiple coal seams is generated based on the geological information of the case study, and the stress evolution is analyzed. The simulation results are then validated through field measurements, providing valuable reference information for safe and efficient production. Overall, this improved method for parameter inversion of the D-Y model, along with the combined numerical simulation and field measurement approach, enhances the understanding of stress evolution in multiple coal seams and contributes to safer and more efficient mining operations. Highlights: An in-depth analysis was conducted to examine how variations in Double-Yield parameters impact the numerical simulation curve. A breakthrough approach for parameter inversion of the Double-Yield (D-Y) model is introduced, and the computational tool is developed. A 3D finite element model is crafted to analyse the dynamic stress evolution during repeated mining of multiple coal seams. The accuracy of simulation outcomes is bolstered by validation against field measurements of mining-induced stress. [ABSTRACT FROM AUTHOR]

Microseismic monitoring technology has developed rapidly in recent years, and effectively evaluating the risk of water inrush from coal seam floor using microseismic monitoring is a research method with development potential, which is of great significance for ensuring the safe and efficient mining of coal resources. Based on the research background of the threat of Ordovician limestone water inrush during the mining process of the 9212 working face in Dongpang Coal Mine, this paper proposes a new method for evaluating floor spatial failure characteristics and water inrush risk based on microseismic monitoring. First, three research stages are established according to theoretical analysis and comprehensive geophysical exploration, and the response characteristics and temporal and spatial distribution of the microseismic events in the different stages are analysed. Second, the weighted coefficient of variation ( CV W ) and three floor factors (S, e , and θ ) are introduced as new risk evaluation indices for the risk of floor water inrush in the vertical direction. The comprehensive weight is determined based on the analytic hierarchy process (AHP) and the entropy weight method, and then the water inrush evaluation model is established by the vulnerability index method. For the water inrush risk of the floor in the horizontal direction, the stratified cumulative kernel density estimation method is employed to determine the degree of water inrush risk and distribution location of different layers from the perspective of microseismic frequency and microseismic energy. Finally, the potential location of the water-conducting channel in the three-dimensional space of the floor is successfully predicted in the analysed working face, and targeted grouting reinforcement and other treatment measures are effectively implemented to ensure the safe mining of the working face. Highlights: Based on microseismic monitoring, a new universally applicable method for analysing the characteristics of floor failure and evaluating the risk of water inrush is proposed. The Weighted Coefficient of Variation ( CV W ) and Three Floor Factors (S, e , and θ) are introduced to analyse the migration characteristics of floor strata and used as the new indices to evaluate the risk of water inrush in vertical direction. The method of stratified cumulative energy kernel density and stratified cumulative frequency kernel density evaluation (SC-KDE) is introduced to comprehensively determine the connectivity degree and range of transverse fractures in the horizontal direction. The potential location of the water-conducting channel in the floor space has been successfully predicted in field engineering. [ABSTRACT FROM AUTHOR]

High-temperature coal oxidation generates a substantial amount of CO and CO2, especially CO, rapidly, which is a primary factor leading to casualties. The oxygen concentration is the predominant factor affecting the high-temperature oxidation of coal, particularly in the generation of CO and CO2. Understanding the generation patterns and relationship characteristics of CO and CO2 under various oxygen concentrations is important for predicting high-temperature coal oxidation and ensuring personnel safety. The paper used TG–MS and FTIR to study the formation characteristics of isothermal oxidation of CO and CO2 in long-flame coal under different oxygen concentrations. The results indicate that there exists an optimal threshold for CO production when the oxygen concentration is about 9% during the isothermal temperature oxidation process at 200.00–350.00 °C. When the oxygen concentration is less than 13%, the influence of oxygen on CO2 production is weakened. As the temperature increases, the pattern of CO + CO2 production and CO/CO2 is reversed, with CO + CO2 increasing and CO/CO2 decreasing. The relationship between the total production of CO and CO2 and the loss of coal mass follows the function y = a + bx at the isothermal temperatures of 300.00 °C and 350.00 °C. An increase in oxygen concentration does not alter the linear relationship. In the isothermal oxidation process of coal, carbonyl and carboxyl groups are the key groups for CO and CO2 production. At 200.00 °C and 250.00 °C, carbonyl and carboxyl groups increase, and other groups are being converted to carbonyl and carboxyl groups while decomposing into CO and CO2. At 300.00 °C and 350.00 °C, the relative content of carboxyl groups decreases. The research findings play a fundamental role in coal mine disaster prevention and control. [ABSTRACT FROM AUTHOR]

Deep coal seam mining causes instability and collapse of coal seam roof frequently, which seriously affects the safety production and threatens the personal safety of underground personnel. In order to evaluate the stability of coal roof accurately, this paper select 6th coal seam in Kongduigou Coalfield of Jungar Coalfieldas research object, analyzes the geological and hydrogeological data, and study the lithology, rock combination, sandstone thickness, fault, fold, seam inclination, rock quality index, and rock compressive strength on the influence of the roof stability, drawing the main control factor 3D mapping projection surface maps. Select 58 borehole data points as the input samples (50 training sets and 8 test sets), use genetic algorithm (GA) to optimize the network random initial weights and threshold initial and sparrow search algorithm (SSA) for secondary optimization for the BP neural network training and learning, establishing GA-BP neural network based on SSA optimization (SSA-GA-BP neural network) coal roof stability evaluation model, which is used to predict and evaluate the 6th coal roof stability of the research area after the training error accuracy reached the requirements. The fuzzy comprehensive evaluation method, BP neural network, GA-BP neural network and SSA-GA-BP neural network are also used to predict and evaluate the 6th coal roof stability. Compare the evaluation results of each model with the actual value. The results show that the error of coal seam roof stability evaluation of SSA-GA-BP neural network is smallest, with the accuracy 88%, and the model is successfully applied to predict the roof stability of the 6th coal seam in Kongduigou Coalfield, which provides a scientific evaluation method and theoretical basis for the evaluation of coal seam roof stability. [ABSTRACT FROM AUTHOR]

In order to quantitatively calculate the critical depth and critical load of mines affected by rock burst, and to achieve effective prevention and control of rock burst in coal mines, this paper proposes a mechanical model for predicting the occurrence of rock burst in coal mine roadways based on catastrophe theory. Additionally, a theoretical calculation formula for initiating rock burst is derived. The first step was to establish a mechanical analysis model, which directly correlated with the in-situ stress, physical and mechanical characteristics of the coal-rock mass, and engineering structural parameters. Following this, a mechanical instability criterion was derived for the key load-bearing circle within the surrounding rock of the roadway. In the final step, the critical depth and load for rock burst initiation were verified for 25 distinct coal mines in China that were prone to rock burst hazards. The research results demonstrate that the discrepancy between the theoretically calculated critical depth and the actual measured statistical values was less than 35%. In addition, the difference between the theoretically determined critical depth and the value calculated by Pan Yishan was less than 32%. Notably, the ratio of the theoretically calculated critical load to the uniaxial compressive strength of the coal-rock mass ranged from 0.38 to 1.93. This aligns with empirical data on rock burst occurrences, as set out in the engineering classification standards for rock masses. These research outcomes substantiated the practical utility of the proposed theory, thereby laying a robust theoretical groundwork for the quantitative control of rock burst. [ABSTRACT FROM AUTHOR]

The boom-type roadheader plays a crucial role in coal mining. However, conducting the real-time monitoring of the mechanical performance and comprehensive adaptive cutting in the dynamic cutting process are challenging. To address these issues, a digital twin system that integrates the elements of "shape, performance, and control" for roadheaders is presented in this paper. The system comprises three components: physical space, service space, and twin space. The service space forms the core of the entire system. Within this space, twin models and control models are created using numerical simulation, artificial intelligence and multi-source data fusion technology. These models serve the purpose of predicting the roadheader's mechanical performance and controlling the swing speed of the cutting arm. The physical space is built using technologies such as robot kinematics, electrical systems, hydraulic transmission, and other relevant techniques. This approach facilitates the transmission of multi-sensor data to twin models. The control model then manages the roadheader's function based on the output signals from the control model. The twin space is constructed utilizing physical rendering engines, databases, and 3D modelling tools. This space visualizes and stores the movement, performance, and control parameters of the roadheader. The results demonstrate that the average absolute error between the measured data from the test's three position strain gauges and the predicted data from the twin system is 10.38 MPa. Furthermore, the twin system achieves an average update interval of 0.34 s, allowing real-time stress monitoring of the structural components of the roadheader and preventing damage caused by overload. The proposed control model enables adaptive adjustment of the swing speed of the cutting arm in approximately 0.3 s. This improvement significantly enhances the adaptive cutting capabilities of roadheaders when dealing with complex coal and rock formations. [ABSTRACT FROM AUTHOR]

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 FROM AUTHOR]

The water-rich burnt rock may threaten the safe production of coal mines. Identifying the boundaries of burnt rock and the water-rich area is of great practical significance for the ensuring the safety of mining operations. Transient electromagnetic and high-density resistivity methods are commonly employed in geophysical exploration, such as for investigating the presence of groundwater or delineating boundaries of altered rocks. These methods are non-invasive and provide detailed information about subsurface conditions without the need for drilling or excavation. The Jiangjun Gobi No. 1 open-pit coal mine is situated in the Kalamaili fault zone and is characterized by a high groundwater content. In certain mining sites within the study area, the inflow of water reaches tens of thousands of cubic meters per day, which significantly impacts production and presents major risks. To accurately determine the boundaries of burnt rock and water accumulation areas in the Jiangjun Gobi No. 1 open-pit coal mine, this paper uses different geophysical prospecting methods based on the depth of the strata. The middle and deep parts are investigated using the high-resolution transient electromagnetic method, while the shallow parts are examined using the high-accuracy high-density electric method. Through analyzing the electrical characteristics of the study area, it is inferred that the low-resistivity area in the northwest represents a shallow surface water-rich region. This area extends continuously towards the northwest, is not trapped, and is supplied by surface water. The deep low-resistivity zone primarily consists of sandstone and coarse sandstone. It is inferred that the low-resistance area in the southern part of the study area is also a shallow surface water-rich region, extending towards the east and west sides, not trapped, and supplied by surface water. The deep low-resistivity zone mainly comprises a combination of sandstone, coarse sandstone, and burnt rock, with intermittent layers of mudstone and argillaceous sandstone. The boundary line of burnt rock (coal-bearing strata) is located in the south of the study area. The resistivity of burnt rock (coal-bearing strata) is higher than that of the surrounding rocks, and the resistivity of coal seams is slightly higher than that of sandstone with larger porosity. Estimating the boundaries of groundwater and altered rocks serves to prevent geological disasters and provides valuable information for mineral development and ecological protection. [ABSTRACT FROM AUTHOR]

Based on the 7618 working face in Yaoqiao coal mine of Datun mining area, the activation mechanism of water-rich faults and the development characteristics of water-conducting fractures in overlying strata under the influence of faults are studied by theoretical analysis, numerical simulation and field measurement in this paper. The research results show that Anderson model and Mohr–Coulomb strength criterion are combined to establish the fault failure mechanical model, and the fault activation criterion under the influence of mining is obtained. FLAC3D numerical simulation results show that with the advance of the working face, the fault begins to be affected by the mining effect of the working face at the distance of 20 ~ 30 m from the fault. Meanwhile, with the advance of the working face, the overburden shear failure range also expands, and the fault fracture gradually expands from top to bottom. The failure zone of the working face roof is connected with the fault fracture zone. Then the fault is "activated" and causes the fault to become a water gushing channel, and finally the water gushing disaster occurs. Through numerical simulation and comparative analysis, the development height of water-conducting fracture is 73.2 m in the absence of fault, and 73.7 m in the presence of fault, indicating that the fault has little influence on the maximum development height of water-conducting fracture. The actual development height of the water-conducting fracture zone in the 7618 working face is 73.97 m and the fracture production ratio is 13.7. The research results can provide theoretical reference for the safe mining of similar working faces across faults. [ABSTRACT FROM AUTHOR]

Aiming to accurately assess the intensity of rockburst in coal mines, we propose a rockburst risk assessment model using the improved catastrophe progression method based on its sudden, complex, and non-linear characteristics. A risk assessment indicator system for rockburst is established based on the occurrence conditions of rockburst, which comprehensively considers 10 main influencing factors. We introduce a combined weighting method consisting of the variation coefficient method and analytic hierarchy process (AHP) to determine the weight and ranking of evaluation indicators, which improves the catastrophe progression method. Finally, by applying 10 coal mine cases into the established model and comparing them with the unimproved catastrophe progression method and several other risk assessment methods, we conclude that the accuracy of the model in assessing rockburst intensity level has increased by a maximum of 42.85%. Our work proves the effectiveness and practicality of the risk assessment model, which can provide good theoretical guidance for assessing rockburst intensity level in coal mines. Furthermore, based on the model risk assessment results and comparative analysis, this paper provides feasible suggestions for reducing the intensity of rockbursts. [ABSTRACT FROM AUTHOR]

The direct emission of coal mine methane caused serious environmental pollution and resource waste. To improve the methane utilization, the porous media burner was regarded as an efficient method. In this paper, the bluff body was proposed to combine with porous media to optimize the combustion characteristics. The effects of bluff body position, size and shape on the temperature distribution and gas emission were studied at different operating conditions. The results indicated that the position of the bluff body greatly influenced the combustion characteristics, and the maximum temperature of 1295 K was obtained at the position of 62 mm. The increase of the bluff body diameter promoted the flame moving to the burner outlet. And the combustion temperature increased first and then decreased when the bluff body height increased. Moreover, the CO and NOx emissions at the height of 20 mm reached 31 and 16.8 ppm respectively. The combustion temperature was significantly improved by increasing the equivalence ratio and velocity. Compared with the single porous media, the addition of the bluff body increased the combustion temperature and reduced the CO emission by 11%. [ABSTRACT FROM AUTHOR]

Knowledge of how to define and estimate the dependence among multivariate hydrological series is essential for detecting abrupt changes in the dependence. In this paper, a new method (BMCTC) is proposed to detect all possible abrupt change points in the dependence among multivariate hydrological series. The total correlation estimated by the matrix-based Renyi's alpha-order entropy functional is firstly introduced to define and measure the dependence strength among multivariate hydrological series. Then, the moving cut total correlation (MCTC) sequence is built by the moving window technique, which is used to measure changes in the dependence strength among multivariate hydrological series. Finally, the Bernaola-Galvan algorithm is used to detect all change points of the MCTC sequence. Simulations are performed to compare the effectiveness of BMCTC with Pearson correlation (BMCPC) and Spearman correlation (BMCSC), Cramer-von Mises (CvM) and copula-based likelihood-ratio (CLR). The results show that all change points are detected by BMCTC regardless of the samples size, but wrong change points or no change points are detected by other methods in most cases. BMCTC is applied to detect change points in the dependence among annual runoff, precipitation and sediment discharge series in the Xiliugou and the Kuyehe River, China. It is found that the dependence among runoff, precipitation and sediment discharge changed abruptly in 1980 and 1996 in the Kuyehe River and in 1999 in the Xiliugou River. These changes are mainly caused by human activities such as construction of water conservancy projects and coal mining. [ABSTRACT FROM AUTHOR]

Coal and gas outburst is a type of coal mine dynamic disaster with complex causes and serious consequences. In China, the number and scale of outburst disasters are among the highest in the world. It is an inevitable stage for outburst that the mechanical instability of the combination of intact coal and tectonic coal (CICTC) in strata. The dip angle of the interface has an important influence on the instability of CICTC-containing gas. To further understand the instability process of CICTC, the uncoordinated deformation of CICTC was defined. According to this, three strain conditions were delimited. The variations of stress under three strain conditions were analyzed, the expressions of additional interfacial stress were established. Then, based on the Mohr–Coulomb criterion, the strength characteristics and failure forms were analyzed. It was found that the dip angle deflects the principal stress in the interface, and the influences of additional stresses on the value of principal stress are opposite. These two reasons make the principal stress state and instability process of the combination complicated. Finally, combined with actual parameters, the instability processes of CICTC under different stress paths and buried depths were studied. It can be found that the failures of CICTC under different stress paths were concentrated appearing in the tectonic coal body, intact coal interface, and tectonic coal interface. With the increase of buried depth, the initial maximum principal stress increases and the reduction from additional stresses to the strength of intact coal interface enhances, which makes the combination damage easily and the failure form change. The research results in this paper can provide a theoretical basis to prevent and control the outburst of the combination containing gas considering the dip angle of the interface. Highlights: The uncoordinated deformation of combination considering the dip angle was first defined. The expressions of additional interfacial stress of combination considering the dip angle were established The influences of different stress paths and buried depths for the instability of combination were discussed quantificationally. [ABSTRACT FROM AUTHOR]

Underground rocks in coal mining and oil exploration are usually subjected to in-situ stress and dynamic loading. In this paper, the tensile fracture behaviors of brittle rocks under coupled in-situ stress and dynamic loading are investigated numerically via the simulation of Brazilian disc (BD) tests of the modified split Hopkinson pressure bar (SHPB). To achieve this purpose, a cohesive zone model in the framework of the finite element method is used to model the cracking of the rock Brazilian disc under confining pressure. The pressure-dependent property of the rock is considered using the recently proposed bi-linear constitutive law. Dynamic Brazilian disc tests of the SHPB with two impact velocities of a striker are simulated for the rock. Comparisons between the simulated results and the reported experimental ones show a good agreement, demonstrating the accuracy and validity of the simulation models and the numerical approach. Due to the existence of holes in the rock in underground rock engineering practices, a pre-hole is inserted in the BD rock specimen in the modified SHPB tests to more realistically consider the rock fracture. The effects of the in-situ stress, the pre-hole size, and the pre-hole position on the dynamic fracture characteristics of the rock are numerically investigated using the modified SHPB test for BD rock specimen. [ABSTRACT FROM AUTHOR]

Solid backfilling in coal mining refers to filling the goaf with solid materials to form a support structure, ensuring safety in the ground and upper mining areas. This mining method maximizes coal production and addresses environmental requirements. However, in traditional backfill mining, challenges exist, such as limited perception variables, independent sensing devices, insufficient sensing data, and data isolation. These issues hinder the real-time monitoring of backfilling operations and limit intelligent process development. This paper proposes a perception network framework specifically designed for key data in solid backfilling operations to address these challenges. Specifically, it analyses critical perception objects in the backfilling process and proposes a perception network and functional framework for the coal mine backfilling Internet of Things (IoT). These frameworks facilitate rapidly concentrating key perception data into a unified data centre. Subsequently, the paper investigates the assurance of data validity in the perception system of the solid backfilling operation within this framework. Specifically, it considers potential data anomalies that may arise from the rapid data concentration in the perception network. To mitigate this issue, a transformer-based anomaly detection model is proposed, which filters out data that does not reflect the true state of perception objects in solid backfilling operations. Finally, experimental design and validation are conducted. The experimental results demonstrate that the proposed anomaly detection model achieves an accuracy of 90%, indicating its effective detection capability. Moreover, the model exhibits good generalization ability, making it suitable for monitoring data validity in scenarios involving increased perception objects in solid backfilling perception systems. [ABSTRACT FROM AUTHOR]

To solve various extraction-related problems existing in the deep Jurassic mines in the Inner Mongolia-Shaanxi (IM-S) mining area, this paper puts forward a method to control roof water hazards based on the sedimentary facies pattern of the aquifers. The problems we addressed are: high volumes of goaf water, mixing of coal-based water in the stope, the proximity of the upper coal seam to water-enriched aquifers, and the inability for safe excavation and stoping. We first investigated the spatial distribution patterns of the aquifers and their related storage properties. A zone model of water yield compatible with the hydrogeological characteristics of a deep Jurassic mine was evaluated for the aquifers in the roof of the 3–1 coal mine, and a "low-position and lateral interception" control method was proposed based on the water yield zonation. The results demonstrated that the depositional environment for the sandstone aquifer in the first member of the Zhiluo Formation had a channel bar paleoenvironment that was characterized by a varying water table. This proved to be the key layer for preventing and controlling the water hazards. The method described in this paper effectively mitigated the water hazards associated with that aquifer in the study area and thus provide a theoretical and practical basis for controlling mine water hazards in the IM-S mining area. [ABSTRACT FROM AUTHOR]

To accomplish various and efficient inhibitions of coal spontaneous combustion (CSC) and solve the safety hazards of CSC encountered in the production and operation of coal mining enterprises, inhibitors play an important role in the prevention and management of CSC. Herein, we report quercetin, which is selection as an antioxidant to prepare a composite solid lipid inhibitor. The concentration of the composite solid lipid inhibitor with the best inhibition effect on the active groups is selected by Fourier pressure infrared experiments, the change pattern of gas content and characteristic temperature released from coal samples during an oxidation process warming process was tested by using a programmed warming test system and simultaneous thermal analysis experiments, and finally, the inhibitory rate and combustion characteristic index were calculated. The results of the research showed that 10 mass% of quercetin had the most impact on the various groups, the highest inhibitor rate of the composite solid lipid inhibitor is 80.67% in the coal low-temperature oxidation process, compared to the raw coal, the heat release of coal treated with the composite solid lipid inhibitor was decreased by 507.65 J g−1, the maximum amount of heat emitted was lowered by 60%, and the flammability index was reduced by 56.4. A composite solid lipid inhibitor containing quercetin developed in this paper indicated high effectiveness in inhibiting CSC, which is vital for coping with the safety management of coal mine production. [ABSTRACT FROM AUTHOR]

Underground coal mining leads to land subsidence, which, in turn, results in damage to buildings and infrastructure, disturbs the original ecological environment, and hinders the sustainable development of coal mining cities. A reasonable estimation of land subsidence, on the other hand, is the foundation for building protection, land reclamation, and ecological environment reconstruction. However, when we applied the existing land subsidence estimation theory to the deep mining areas of the Ordos coalfield in western China, there was a significant deviation between the estimations and the measurements. To explain such unusual case, we propose using the overburden's average GSI (Geological Strength Index) value instead of the compressive strength (UCS) of rock specimens for a better representation of the overburden's overall properties. By using on-site subsidence monitoring results and historical data, we provided evidence which supports that the overburden's average GSI value has a much greater impact on subsidence rates than the UCS. Subsequently, we investigated the relationship between three typical overburden's GSI values and the subsidence rates via a calibrated numerical model, revealing the variation patterns of maximum surface subsidence when the overburden's average GSI value is set at 30, 50, and 75, respectively. Finally, on the basis of the measured and simulated results, we discussed a non-conventional strip mining method for mining subsidence control in the deep mining areas of the Ordos coalfield in western China, and explained why it is possible and what are the significant advantages behind. The proposed methods, findings, and suggestions in this paper are therefore quite helpful for researchers and engineers who wish to estimate and control the mining-induced land subsidence, as well as for those who are particularly interested in the study of environment science related to land subsidence. [ABSTRACT FROM AUTHOR]

Coal mine water outburst under fluid-solid coupling is a hot topic in coal geology. In this paper, the FLAC 3D simulation method is used to systematically study the water outburst problem of fluid coupling with coal mine floor. The results show that the vertical stress of the floor in the goaf has an obvious downward trend after coal seam excavation. Under the joint influence of mine pressure and bearing water pressure, the working face before the old roof pressure can be affected by two stages: the first stage is the advance pressure compression section on both sides of the working face, and the other stage is the pressure relief expansion section under the goaf. Before the old roof is pressed, the shear stress near the roof and floor is also affected to some extent. The front and rear displacement value of the goaf is negative, which is the result of the advance supporting pressure. The effective thickness of the floor waterproof layer decreases gradually with the advance of the working face. When the working face continues to advance, there will be a risk of water outburst. With the increasing width of the working face, the height of the guide belt increases. Therefore, in the process of mining activities, a variety of factors should be considered comprehensively, and a reasonable width of the working face should be selected to ensure the safety of mining. [ABSTRACT FROM AUTHOR]

The instability control of deep mining roadway is currently dominated by ejection and grouting, as well as floor support, which contradicts the economic and excavation efficiency of production. Taking the failure site of Xin'an Coal Mine in China as an example, this paper systematically analyzes the failure characteristics of supporting components, crack propagation, and surrounding rock deformation in situ, and the impact of failure on the rights and interests of staff, enterprise benefits, and low-carbon environmental protection. Then, a three-way continuous anchorage theory and the derived control technology are proposed based on the exploration of the instability mechanism. Besides, the UDEC Trigon model is adopted to reproduce the instability process and demonstrate the effect of the proposed control technology. According to the subsequent industrial test, the plastic deformation developing from shallow to deep parts leads to the bending, subsiding, swelling, and deformation of rock mass within 5.5 m of the roof, and the surrounding rock failure mainly features the shear failure in the middle of the tail of the supporting components and anchorage relaxation. Meanwhile, it wrecks huge havoc on the rights and interests of staff, enterprise benefits, and CO 2 emission. Following the smooth application of the new technology to roadway excavation, the roof subsidence and two side displacements are reduced by 91.18% and 58.5%, respectively, compared with the original scheme, the rock mass fractures within 1.71 ~ 3.92 m of the roof is effectively sealed, the evolution depth of bed separation is down by 78.6%, and the excavation efficiency rises by 50% while ensuring the supporting cost. In addition, the defects of the new technology in engineering application are also discussed. Accordingly, the R&D and application of this new technology provide a positive reference for the efficiency control of deep mining roadway. Highlights: A three-way continuous anchorage theory and relevant technique are proposed. Multiscale original position analyses are conducted on the failure features of deep coal roadway. The impact of surrounding rock instability on sustainability was considered for the first time. The new scheme reduces roof subsidence by 91.2% and sides' displacement by 58.5%. [ABSTRACT FROM AUTHOR]

In the N00 coal mining method, one of the most critical issues is ensuring the safety of the entry behind the working face. To address this challenge, various roof control techniques, such as precise directional roof-cutting technology (PDRCT), constant-resistance cable supporting technology (CRCST), and dynamic pressure-bearing supporting technology (DPBST), have been developed. However, the design method for these technologies has not been clearly defined, resulting in a lack of theoretical basis for parameter selection. This paper seeks to address this gap by further studying the mechanisms of PDRCT, DPBST, and CRCST in the N00 coal mining method, and proposing corresponding mechanical calculation models, design ideas, and calculation methods for these technologies. The results reveal that the primary function of PDRCT is to expand the height range of the caved rock mass in the mined area, thus reducing the subsidence space of the high-level roof and mitigating the dynamic pressure effect of the entry surrounding rock. The height of the roof cutting is crucial to the design, and its theoretical value must satisfy the condition that the broken expansion volume of the caved rock mass is equal to the volume that is mined. DPBST is essential for protecting the entry immediate roof and preventing internal damage during the movement of the upper roof. The dynamic pressure-bearing support strength should be appropriately designed to prevent the short cantilever roof structure from breaking within the entry's width during the movement of the high-level roof. Similarly, CRCST's most critical function is to maintain the long-term stability of the entry immediate roof by relying on the cable support forces and the stability properties of the high-level roof strata while it is not moving. The anchor cable support strength should be reasonably designed to prevent the short cantilever roof structure from collapsing under its own gravity. The proposed design method was applied to the Ningtiaota coal mine, leading to a 15.6% reduction in maximum roof deformation and a 12.0% decrease in average deformation, demonstrating the favorable impact of the approach. Highlights: The mechanisms of precise directional roof cutting technology (PDRCT), constant-resistance cable supporting technology (CRCST), and dynamic pressure-bearing supporting technology (DPBST) in the N00 coal mining method were revealed. Corresponding mechanical calculation models, design ideas, and calculation methods for the key parameters of PDRCT, DPBST, and CRCST were obtained. [ABSTRACT FROM AUTHOR]

The grand-scale suspended roofs overlying the goaf are commonly developed under thick-hard rock strata (THRS) during the mining process of the deep coal seam. As a result, strong mine seismicities triggered constantly by deep mining have impeded severely the safety and efficient operation of deep mines. The working-face deep-hole blasting technology has been utilized to weaken the roof for releasing the mine pressure, thereby reducing the risk of violent dynamic hazards. In this paper, Dongtan deep coal mine is taken as an example, the radius of rock failure regions induced by blasting is calculated based on the expansion theory of cylindrical charges. LS-DYNA and UDEC7.0 softwares are employed to simulate the rock pre-splitting and overburden migration under the working-face deep-hole blasting, and the roof pre-splitting and pressure relief mechanism of the working-face deep-hole blasting are revealed. According to the micro-seismic, support working resistance and real-time stress monitoring results, the working-face deep-hole blasting technology could actively break the integrity of the roof. Using the blasting, high-energy mining-induced seisms are decreased dramatically or disappeared fully. The advanced abutment pressure of the coal seam decreases with the increase of the working-face deep-hole blasting time, which indirectly indicates that the weakening degree of the thick-hard roof gradually increases under the action of multiple blasting. The working-face deep-hole blasting technology has achieved the desired effect in the pressure relief in hard suspended roofs for preventing and controlling strong mining-induced seismicity. Highlights: The distribution of mining-induced seismicities before and after the working-face deep-hole blasting is revealed by the micro-seismic system. The rock pre-splitting and overburden migration influenced by the working-face deep-hole blasting are numerically simulated. The effectiveness of strong seismicity prevention and control is systematically evaluated by a series of monitoring technology. The working-face deep-hole blasting technology could achieve the desired effect in the pressure relief of roofs. [ABSTRACT FROM AUTHOR]

Mine Subsidence is a phenomenon of lateral or vertical ground movement caused by a failure initiated at the mine level of man-made underground mines and an abandoned mine is a site where mining activities occurred but acceptable mine closure and reclamation did not take place or was incomplete. Subsidence is one of the major problems which is faced over an old abandoned mine. Presently there are limited means or methods which can predict subsidence over an old abandoned coal mine at a shallow depth efficiently and the precautionary methods that should be taken in these situations. This research paper will cover the possible causes which can lead to subsidence above an old abandoned board and pillar coal mines at a shallow depth. The research includes the calculation of the factor of safety for pillars and analysis of FoS using ANSYS and Monte Carlo Simulations for ascertaining subsidence. An old abandoned coal mine of South Eastern Coalfields Ltd. (SECL, a subsidiary of Coal India Limited), was considered for the study of coal pillar fatigue and eventual crushing of pillars over a long duration of time, simulation analysis of stress and strength of coal pillars over a long period, change in behavior of factor of safety as the dimension of the pillars changes. [ABSTRACT FROM AUTHOR]

Based on the greening and low interference disposal requirements of coal gangue in high-yield and high-efficiency mines in Inner Mongolia and Shaanxi, and by integrating the existing theories and technologies such as underground filling technology of coal gangue, mine yellow mud grouting technology, and the evolution law of mining overburden fractures, a technology of filling goaf with coal gangue slurry for green disposal of coal gangue is proposed. The principle and technical framework of the technology of filling goaf with coal gangue slurry are clarified. This paper expounds on the technological process of technology of filling goaf with coal gangue slurry, establishes three types of slurry filling systems, such as centralized ground layout, ground and underground coordinated layout, and centralized underground layout, and constructs three slurry filling methods, including low-level grouting, adjacent level grouting, and high-level grouting, forming seven kinds of technology models of filling goaf with coal gangue slurry, including ground centralized pulping + high-level grouting, ground centralized pulping + adjacent grouting, ground centralized pulping + low level grouting, ground and underground coordinated pulping + adjacent grouting, ground and underground coordinated pulping + low level grouting, underground centralized pulping + adjacent grouting, and underground centralized pulping + low level grouting, and gives the selection process of technology models of filling goaf with coal gangue slurry. Based on the different conditions and requirements of Haidaze Coal Mine and Huangling No. 2 Coal Mine, engineering tests were carried out on two different technology modes, namely, ground and underground coordinated pulping + low level grouting and ground and underground coordinated pulping + adjacent grouting, based on simulation tests of low level grouting and adjacent grouting. The tests prove the feasibility of filling goaf with coal gangue slurry and explore the way for the theoretical research of the technology of filling goaf with coal gangue slurry and greening and low interference disposal of coal gangue. [ABSTRACT FROM AUTHOR]

Understanding the molecular structure characteristics of coal at the molecular level is of great significance to realize the rational utilization and efficient conversion of coal. This paper gives insights into the acquisition of characterization parameters of coal molecular microstructure by testing and analyzing the long flame coal from Qinggangping (QGP) Coal Mine through proximate analysis, ultimate analysis, vitrinite reflectance determination, fourier transform infrared Spectroscopy test (FTIR), X-ray photoelectron epectroscopy test (XPS), carbon nuclear magnetic resonance (13C-NMR) and X-ray diffraction (XRD). The results show that benzene rings in the QGP coal are mainly connected in a disubstituted way, accounting for 36.48%. Oxygen atoms mainly exist in the oxygen-containing functional groups such as the ether C–O, C=O and –COO. Aliphatic hydrocarbons in the aliphatic group are mainly of symmetrical -CHx stretching vibration. Hydroxyl groups are mainly composed of OH–OH and OH–O hydrogen bonds, accounting for 29.21% and 21.53%, respectively. Nitrogen atoms exist in the form of C4H5N. The coal molecular is mainly of aromatic carbon structure, where the ratio of bridge aromatic carbon to peripheral carbon is 0.198. There are benzene, naphthalene and anthracene in the coal molecular structure, and the former two chemicals play a dominating role. According to the analysis results, the molecular formula of the QGP coal is finally determined as C205H181O29N3S. On this basis, the two-dimensional and three-dimensional macromolecular models are constructed with the assistance of simulation software. In addition, the 13C-NMR spectra and densities of the constructed molecular models are calculated, which verifies the rationality of the models. The macromolecular structure model of bituminous coal constructed in this study provides a theoretical model basis for the optimal surfactant. [ABSTRACT FROM AUTHOR]

Emulsion pump station is widely used to provide power for full-mechanized coal mining face equipment. With the development of the mining technique of longwall face and the extensive use of large mining height and high working resistance of the hydraulic support, the fluid supply pressure is more unstable and the pressure impact is increasingly intensified. The intelligent control of the emulsion pump station is the key to the development of the stable fluid supply technology at the working face. This paper develops a new on-line adaptive learning technique to improve the response speed of pumping station based on the optimal control algorithm of adaptive dynamic programming (ADP). The state space model of the working face fluid supply system in the process of no-load column lifting of hydraulic support is first established using the flow relationship, and the effectiveness of the proposed control algorithm is then verified by simulation validation. Moreover, combined with a certain fluid supply system of a fully mechanized caving face in Shandong Energy Xinwen Group XinJulong Co., Ltd, a technical scheme of adaptive stable fluid supply is verified in engineering practice. The results indicate that the fluid supply system using the proposed control algorithm has a favorable tracking effect on the ideal trajectory, and the tracking error can converge to near zero. The output pressure of the fluid supply system using the stable fluid supply technology is more stable, and the practical effect is good, which meets the demand of stable fluid supply in the mining face. [ABSTRACT FROM AUTHOR]

Underground mining of minerals is accompanied by a change in the rock mass geomechanical situation. This leads to the redistribution of stresses in it and the occurrence of unexpected displacements and deformations of the earth's surface. A significant part of the civil and industrial infrastructure facilities are located within the mine sites, where mining and tunneling operations are constantly conducted. Irrational planning of mining operations can lead to loss of stability and destruction of undermined facilities. Therefore, it is important to study the earth's surface deformation processes during mining operations, which ensures safe and sustainable operating conditions. The research objective of this paper is to analyse the behaviour of a natural gas pipeline under the influence of underground mining activities, with a particular focus on understanding the effects of horizontal surface deformations and their potential impact on pipeline safety and structural integrity. Its performance and safety are determined on the basis of the found parameters of the earth's surface horizontal deformations and their comparison with permissible parameters characterizing the conditions for laying pipelines, depending on the mining-geological conditions and the degree of their undermining. Based on determined conditions for the safe undermining of the natural gas pipeline, it has been revealed that in its section between the PK212+40 and PK213+80 (140 m) pickets, the estimated parameters of the earth's surface horizontal deformations exceed their permissible values. This can cause deformation and damage to the pipeline. For the safe operation of the pipeline during the period of its undermining, in order to eliminate the hazardous impact of mining the longwall face, additional protection measures must be applied. It is therefore recommended that the gas pipeline between the PK212 and PK214+20 pickets be opened prior to the displacement process (200 m from the stoping face), thus reducing the density of the gas pipeline-soil system. Recommendations for controlling the earth's surface deformations within the natural gas pipeline route are also proposed, which will ensure premature detection of the negative impact of mining operations. [ABSTRACT FROM AUTHOR]

This paper addressed the rockburst hazards caused by tectonic stress in the "three hard" coal mine in Datong Coalfield. We analyzed tectonic stress characteristics in the mining area and the mechanism of tectonic stress inducing rockbursts. We built the stress analysis model for rockburst-inducing tectonic stress. The roadway of the coal seam 12# in Xinzhouyao Coal Mine of Datong Coalfield was explicitly analyzed as an example. It was found that roof bedding separation was very likely to happen under the action of local tectonic stress in the roadway of the "three hard" coal seam, causing rockbursts that pushed out the coal wall. Numerical simulation was performed to analyze the occurrence of rockbursts induced by tectonic stress. We validated that stress concentration was more likely to happen in the coal-rock masses under the action of the tectonic stress, causing rockbursts. Besides, a large horizontal stress gradient would be formed near the roadway coal wall when the principal stress was perpendicular to the roadway axis. Rockbursts were highly probable in the coal-rock masses under this situation. [ABSTRACT FROM AUTHOR]

Land subsidence has become a widespread engineering geological problem due to human-induced causes such as the withdrawal of groundwater and the extraction of coal and ores. There is a relative lack of research on land subsidence under the coupling effect of groundwater and coal mining. This paper uses numerical and theoretical computational models to study land subsidence under the coupling effect of groundwater and coal mining. The study area is a coal mine in Jining City from 2000 to 2020. Numerical results show that groundwater withdrawal induces substantial land subsidence over a long period and that the rate of land subsidence decreases over time. The maximum land subsidence was 128 mm in 2010. Due to coal extraction (2015), the area induces significant land subsidence in the short term. The maximum land subsidence in 2016 was 305 mm. Based on the stochastic medium theory, this paper establishes a theoretical model for land subsidence under the coupling effect of groundwater and coal mining. And based on the numerical results, the theoretical subsidence equation applicable to the area is calculated. By comparing the theoretical results with the actual measurement results, the analysis proves that the equation can better calculate the land subsidence of the model. [ABSTRACT FROM AUTHOR]

Given that coal is not a homogeneous substance, it is of great significance to identify and quantify the structural characteristics thereof for comprehensive analysis. In this paper, the non-caking coal in Chicheng Coal Mine was selected as the research object. The C, H, O, N, and S contents in the coal samples were obtained by proximate/ultimate analysis experiments. The structural characteristics of aromatic, aliphatic hydrocarbons, and oxygen-containing functional groups in the experimental coal samples were obtained by Fourier transform infrared spectroscopy (FT-IR) experiments. X-ray photoelectron spectroscopy (XPS) experiments were performed to obtain the occurrence state of N and S elements in coal samples. Nuclear magnetic resonance (13C NMR) experiments provided the carbon skeleton structural information of the coal samples. The macromolecular structure model of non-caking coal in the Chicheng Coal Mine was established on this basis. The molecular formula of non-caking coal in Chicheng Coal Mine was determined to be C207H181O32N3S.The13C NMR-predicted spectrum of the model showed good consistency with the 13C NMR-experimental spectrum obtained from the experiments, providing researchers with reference to the construction ideas and methods of molecular structure models of different coal samples. [ABSTRACT FROM AUTHOR]

High-efficiency rock breaking technology is an important problem to be solved urgently in deep mining. The existing auxiliary rock breaking technology for coal mine excavation has problems such as polluting coal, high requirements for tool materials, and difficulty in subsequent washing. In this paper, an active excitation cutting system for rotary cylinder of cantilever roadheader based on alternating valve is proposed. According to the classical calculation formula of cutting load of roadheader, considering the stiffness-damping characteristics of cutting part and cutting cylinder, the simulation algorithm of cutting load is compiled based on MATLAB simulation analysis software. The excitation cutting experiments of different cutting depths are carried out on the cutting test bench, and compared with the simulation algorithm of cutting load. Taking the cutting load as the discriminant index, the influence of oil supply pressure and excitation frequency of rotary cylinder on the cutting load is analyzed based on the simulation algorithm of cutting load. The results show that the error between the simulation results and the experimental results of the active excitation state is less than 12%, and the two are in good agreement. Under the condition of 30 HZ, when the excitation amplitude is 8 Mpa, 10 Mpa, 12 Mpa, 14 Mpa, when the rotary cylinder excitation amplitude is 10 Mpa, the minimum is 131.42 KN. Compared with the rotary cylinder excitation amplitude under the condition of 10 Mpa, when the excitation frequency is 30 HZ, 35 HZ, 40 HZ, 45 HZ, when the excitation frequency is 40 HZ, the minimum is 83.08 KN, indicating that changing the excitation amplitude or oil supply pressure of the rotary cylinder is helpful to adjust the cutting performance. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental study of flames propagating with an alternating-sign velocity in methane–air and coal dust–methane–air mixtures in a vertically located closed tube at coal dust concentrations of 0.10–0.42 kg/m3. The results of the study can be useful for developing combustion models and assessing dynamic and thermal effects during combustion of methane–air–coal dust mixtures in coal mines. [ABSTRACT FROM AUTHOR]

Understanding the molecular structure characteristics of coal at the molecular level is of great significance to realize the rational utilization and efficient conversion of coal. This paper gives insights into the acquisition of characterization parameters of coal molecular microstructure by testing and analyzing the long flame coal from Qinggangping (QGP) Coal Mine through proximate analysis, ultimate analysis, vitrinite reflectance determination, fourier transform infrared Spectroscopy test (FTIR), X-ray photoelectron epectroscopy test (XPS), carbon nuclear magnetic resonance (13C-NMR) and X-ray diffraction (XRD). The results show that benzene rings in the QGP coal are mainly connected in a disubstituted way, accounting for 36.48%. Oxygen atoms mainly exist in the oxygen-containing functional groups such as the ether C–O, C=O and –COO. Aliphatic hydrocarbons in the aliphatic group are mainly of symmetrical -CHx stretching vibration. Hydroxyl groups are mainly composed of OH–OH and OH–O hydrogen bonds, accounting for 29.21% and 21.53%, respectively. Nitrogen atoms exist in the form of C4H5N. The coal molecular is mainly of aromatic carbon structure, where the ratio of bridge aromatic carbon to peripheral carbon is 0.198. There are benzene, naphthalene and anthracene in the coal molecular structure, and the former two chemicals play a dominating role. According to the analysis results, the molecular formula of the QGP coal is finally determined as C205H181O29N3S. On this basis, the two-dimensional and three-dimensional macromolecular models are constructed with the assistance of simulation software. In addition, the 13C-NMR spectra and densities of the constructed molecular models are calculated, which verifies the rationality of the models. The macromolecular structure model of bituminous coal constructed in this study provides a theoretical model basis for the optimal surfactant. [ABSTRACT FROM AUTHOR]