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Aiming at the promotion and application of 5G communication technology in coal mines, this paper analyzes the explosion prevention risk of radio frequency (RF) electromagnetic energy under the condition of far field radiation. In this paper, the equivalent model of the loop antenna and the theoretical calculation model of the spark power are established under the assumption that the characteristic impedance of the spark is matched with the internal impedance of the antenna. Secondly, for the 3.55 GHz operating frequency, a narrow bandwidth loop receiving antenna and a horn transmitting antenna by theoretical calculation are designed, and the S11 curve of the designed antenna by CST simulation software is verified. Finally, based on this, a simulation platform for transceiver antenna is built, which can be used to estimate the electric field strength and integrated voltage at both ends of the breakpoint of the loop antenna. The simulation results show that: when the electric discharge machining (EDM) is matched with the internal resistance and impedance of the antenna, the EDM power is maximum, and the impedance value of the EDM has no effect on the induced voltage of the whole antenna, and the power obtained by the EDM decreases with the increase of the distance between the transmitting and receiving antennas. The simulation and calculation show that when the transmitting antenna power is 100 W and the transmitting antenna gain is 5, the theoretical maximum spark power generated under the far-field radiation condition is not enough to ignite the gas. Therefore, the threshold power index in the standard may be too conservative and needs to be further verified.

One-time full-thickness mining with ultra-high mining height has the characteristics of high mining efficiency and high resource recovery rate. In order to explore the further breakthrough of ultra-high mining height fully mechanized mining technology and analyze the feasibility of surrounding rock stability control of its working face, on the basis of investigating the development process of ultra-high fully mechanized mining, this paper summarizes the surrounding rock pressure behavior and coal wall fragmentation law of ultra-high mining height fully mechanized mining working face, and analyzes the overall technical characteristics and applicable performance of the existing ultra-high hydraulic support, the paper also introduces the basic situation of the hydraulic support in the 10 m super-large mining height working face. Through analysis, it is found that the apparent strength of the rock pressure in the working face is basically positively correlated with the mining height. The greater the mining height, the greater the support resistance of the working face, and the coal wall spalling is one of the main factors that hinder the efficient promotion of the super-large mining height mining. The stress of the coal wall can be effectively reduced by improving the initial support capacity of the hydraulic support in the working face; the hydraulic support increases with the mining height of the working face, the selection resistance increases, the support center distance is widened, and the large gradient transition mode can effectively improve the resource recovery rate of the end zone while providing reliable support; in order to adapt to the transportation of large volume mining equipment, the working resistance of the advanced support increases with the increase of the cross section of the trench in the super high mining face; the supporting hydraulic support of the working face is optimized and upgraded through design means, overall structure, manufacturing process and other aspects to improve reliability and adaptability; relative to the support of the working face with lower mining height, the mining with super mining height pays more attention to the safety technical requirements in the support process, and needs to improve the safety measures such as coal gangue protection before the frame, dust prevention and dust reduction between the frames, and safety maintenance and inspection at the later stage; it is considered that the surrounding rock stability control and its supporting equipment of the working face are the key points for the development and promotion of the super-large mining height fully mechanized mining technology. The full life development of the super-large mining height hydraulic support from the selection of support parameters, the design of support structure, the manufacture of hydraulic support, and the later maintenance and inspection is the basis for supporting the efficient promotion of the super-large mining height mining.

Aiming at the problems of low efficiency of coal mine data utilization and less data sharing caused by the lack of standardized coal mine data model, this paper studies the three-dimensional spatial multivariate data relationship and attribute data planning of coal mines. The process and algorithm from mining engineering plan to tunnel 3D modeling are given, the coal mine data model based on ORM mapping is formed, and the 3D model is output under WebGL technology system. The results shows that the spatial data model established in this paper has high storage and utilization efficiency, and can provide support for data utilization and analysis of mine safety information intelligent decision-making.

In order to utilize high-rank coal efficiently and cleanly, based on Shanxi lean coal, this paper explores the molecular structure characteristics of lean coal and constructs a molecular model of lean coal. In this paper, X-ray photoelectron spectroscopy (XPS) and solid-state nuclear magnetic resonance carbon spectroscopy （13C NMR） were used to characterize and analyze the element occurrence and carbon atom structure of lean coal, and a macromolecular model of lean coal was constructed and optimized. The results showed that the molecular aromatic structure of lean coal was composed of 1 naphthalene, 8 anthracene, 1 tetraphenylene, 1 pyrene, 2 pyridine, 2 pyrrole and 1 thiophene. The oxygen-containing structure includes two intramolecular oxygen-bonded aliphatic carbons, two oxygen-substituted aromatic carbons and one carbonyl carbon. Aliphatic hydrocarbons are composed of 2 fatty methyl groups, 3 aromatic methyl groups, 2 methylene groups and 4 methylene groups. The final macromolecular model of lean coal is C200H140O5N4S. After the initial model was optimized, the valence energy and non-bond energy of coal molecules decreased, but the valence electron energy of coal molecules in the final model was higher than that of non-bond energy, which was the main part of the total energy. Therefore, from the point of view of the adsorption space that the surface of lean coal can provide for gas, the adsorption advantage of CO2 gas in lean coal is stronger than CH4 gas.

This paper aims to establish a model that can reasonably reflect the mechanical properties of coal containing gas under different water content and confining pressure conditions. Firstly, the stress-strain characteristics of coal containing gas under different water content and confining pressure conditions are analyzed based on triaxial tests. Afterwards, this paper obtains the Duncan-Chang model parameters by combining the Duncan-Chang model and Janbu formula. Moreover, it establishes the fitting formulas of initial elastic modulus failure stress and various influencing factors, and conducts an improved Duncan-Chang model to characterize the deformation law of coal containing gas under different stress levels. Finally, this paper verifies the improved model and evaluate the accuracy of the mode. The results show that the increase of water content is an important reason for the dynamic change of coal model parameters of coal containing gas. The prediction curve of the improved model is in good agreement with the actual test curve, and the improved model can accurately reflect the stress-strain characteristics of coal containing gas under different confining pressures and water contents.

This paper mainly discusses the development status, pain points and future trend of China’s coal mine robot industry. In the context of the “robot +” era, this paper expounds the development of China’s robot industry from the aspects of the number of robot enterprises, regional distribution, industrial park construction, advantage track, national policy, etc., and expounds the changes and challenges brought by the domestic Internet and manufacturing enterprises. This paper focuses on the analysis of coal mine robot technology and industry pain points, and extracts three major capabilities that coal mine robot should have to realize intelligence. Strengthening the construction of supply chain and standard system is proposed. The classification standard of coal mine robot L0-L5 is introduced in detail.

Long-term work in the environment of high temperature and high humidity underground not only endangers the health of miners, but also easily leads to the occurrence of underground accidents. In view of this situation, personal cooling garments can be used as an individual cooling device. This paper summarizes the existing cooling garments technology and its development, which is divided into air-cooled garments, liquid-cooled garments, phase change garments, semiconductor cooling garments and chemical ice bag cooling garments according to the different cooling medium. This paper discusses the working principle, advantages and disadvantages, as well as the feasibility of existing personal cooling garments in the underground. Finally, this paper looks forward to the future development direction of personal cooling garments.

The occurrence of safety accidents in coal mine caused by unsafe behaviors is related to various inducements. This paper aims to explore the correlation between the core inducements and the inducements of unsafe behaviors and their influence on unsafe behaviors. In this paper, 339 coal mine safety accident reports were collected, and 37 unsafe behaviors and their inducement-related words were extracted with the help of text mining method, and the association rules were mined with Apriori algorithm to build the association network of unsafe behaviors and their inducements. Then, the association rules were analyzed. It is show that six types of core inducements, such as insufficient safety awareness, inadequate investigation and management of hidden dangers, and inadequate implementation of the safety production responsibility system, will have a direct impact on unsafe behavior, and six groups of core correlation factor sets will also have an indirect impact. Therefore, coal mining enterprises should focus on the core inducements and their associated factor sets to prevent the occurrence of unsafe behaviors.

In order to analyze the various influencing factors and their configuration paths of human-caused accidents in coal mines, through adopting the clear set qualitative comparative analysis method(csQCA) and taking 25 typical human-caused accident cases as the research object, this paper selects seven conditional variables: human factors, safety supervision, organization and management, equipment and facilities, complex environment, safety norms and safety culture to discuss the group configuration and multiple paths of human-caused accidents in coal mines. The results show that there are seven configuration paths in the formation of human-caused accidents in coal mines, and the associative effect is shown among the conditional variables in the seven configuration paths. In addition, different conditional variables have different influence on human-caused accidents in coal mines. Among them, safety norms, complex environment, organization management and safety supervision impose important effect on the occurrence of human accidents, and the organization management is particularly critical. Finally, this paper proposes the measures and suggestions to prevent human-caused accidents in coal mines based on the research results.

In order to explore the research trends of thermodynamic disaster in coal mine, based on the perspective of information visualization, 2 845 related papers published in CNKI database from 2002 to 2021 were used as data sources, and CiteSpace was used to conduct scientific measurement analysis on the number of papers, authors, institutions and keywords. The research shows that the research on thermodynamic disaster in coal mine generally shows three stages: slow growth, steady growth and stable development. DENG Jun, WANG Deming, YU Minggao, WEN Hu are the main core authors in this field. China University of Mining and Technology, Xi’an University of Science and Technology, Liaoning Technical University, China University of Mining & Technology（Ｂｅｉｊｉｎｇ） are the main research institutions in this field. Hot keywords mainly focus on gas explosion, coal spontaneous combustion, numerical simulation, mined-out area, etc. The research emphasis in this field is mainly embodied in the research of spontaneous combustion characteristics of coal and gas explosion, in which numerical simulation is an important research method. At present, there are few studies on coal mine thermal power compound disasters and disaster monitoring and early warning. In the future, the research on these two aspects can be strengthened.

In view of the problems of system independence, lack of linkage and interworking, and unified scheduling in the communication system of coal mines, the architecture design requirements for building a 5G integrated communication system in coal mines are studied to meet the typical application scenarios of underground linkage scheduling, remote （unmanned） control, and inspection robots; the technical requirements of the system for low delay / high reliability, data safety and large bandwidth in carrying multiple data services such as collection, control and two-way interaction are analyzed; this paper studies the network extension structure, safety operation mechanism, API multi-level architecture, and the design requirements of the dynamic network control strategy of the coal mine 5G integrated communication platform architecture using NGN network architecture, SIP soft switch protocol and open interface technology; this paper discusses the interface types, business requirements, and construction methods of the wireless bearer network based on 5G communication, and analyzes the conclusions of three typical linkage applications. The research results show that the architecture design and linkage application test of the 5G based coal mine integrated communication system are of great significance to solve the problems of interface compatibility, remote control, unified scheduling faced in the construction of intelligent minemultiple systems.

During and after the in-situ mining of anthracite coalbed methane, the influence of temperature on anthracite coal has become an important factor in judging whether a project can be implemented. In this paper, the stress-strain curves of anthracite at 10 MPa hydrostatic pressure and different temperatures, stress-strain curves at 300 ℃ and different hydrostatic pressures, the stress-strain curves of anthracite under different hydrostatic pressures under temperature rise of 500 ℃ and then slow cooling to 300 ℃, were studied by using the servo experiment device independently developed by the Key Laboratory of In-situ Modified Mining of Ministry of Education, Taiyuan University of Technology. The results show that during the process of heating up, anthracite exhibits different thermal expansion laws under different hydrostatic pressure conditions. The greater the hydrostatic pressure, the smaller the thermal deformation; as the temperature increases, the elastic modulus and peak strength of anthracite will decrease accordingly; the confining pressure will enhance the strength of anthracite, which is specifically expressed in that with the increase of hydrostatic pressure, the elastic modulus and peak strength of anthracite will increase; the weakening effect of high temperature on anthracite is irreversible. The performance is that when anthracite is directly heated to 300 °C, the cohesion and internal friction angle of the two are different from that of anthracite when the temperature is raised 500 °C and then lowered to 300 °C. This paper uses orthogonal experiments to fit the elastic modulus of anthracite within 15 MPa and 300 ℃ as a function of confining pressure and temperature.

In order to solve the problems of unreasonable selection of prediction methods and poor prediction accuracy for gas emission in mining face, with the help of machine learning methods, in this paper, existing data was processed through cross-validation, the support vector and the random forest algorithm were used to construct the prediction model and the prediction performance of the two models before and after dimensionality reduction of the input data were compared and analyzed. The test shows that after cross-validation and data dimensionality reduction, the two prediction models tend to be stable, and the prediction accuracy are greatly improved. The overall prediction performance of the SVR model is slightly better than that of the RFR model; SVR model takes about 0.015 s per round of testing, much lower than the latter one; the average absolute error of the SVR model is about 0.18 m3/min, and the average relative error is about 3.26%, which is relatively better than the other one. The models established in this paper both present good performance, and the SVR model after feature screening by random forest takes less time, has less error and better stability, which effectively realizes the prediction of the gas emission and plays a reference role in simplifying data collection and scientifically formulating gas control measures.

In order to provide a comprehensive reference for the study of carbon dioxide displacement of coalbed methane, this paper explores the influence of different influencing factors on coal adsorption capacity, analyzes the gas migration and adsorption principle in coal bed, as well as the difference and relationship between different adsorption models, and introduces the pilot test and application of CO2-enhanced coalbed methane recovery in different countries. Using VOSviewer software and CNKI metrological visualization analysis function, this paper analyzes the annual publication trend and keyword time trend of CO2-ECBM related literature in CNKI and Web of Science databases, and discusses the problems existing in CO2-ECBM. The results show that coal rank and pore structure, temperature and pressure, moisture content and other factors can affect coal adsorption capacity in different forms. Gas migration in coal seam is a complex system composed of adsorption/desorption-diffusion-seepage. The best adsorption model should be considered in studying coal adsorption gas. Based on VOSviewer analysis, CO2-ECBM research is a hot topic in China. The research direction has gradually shifted from macroscopic geological storage evaluation to reveal the mechanism of coal storage and displacement gas from microscopic or molecular levels such as pore structure and composition of coal, and multi-field coupling simulation of CO2-ECBM.

In view of the current coal mine safety supervision problems of insufficient real-time and pertinence, relying on the basic data support of “comprehensive management and control platform” in the intelligent construction of coal mine, this paper proposes the supervision concept of using information technology to build coal mine safety production risk monitoring and early warning system. This paper analyzes three forms of existing coal mine safety risk data integration, takes the special topic of fire risk in coal mine goaf as an example, and explains the real-time supervision mode of major risk special topic with four risk indexes of blue, yellow, orange and red. Taking an eastern province as an example, the intelligent supervision mode based on coal mine safety production risk monitoring and early warning system is verified, which realizes the remote real-time supervision of some functions of mine end supervision and the drilling query of important safety index data, and greatly improves the real-time and pertinence of coal mine safety supervision and supervision.

This paper introduces the working principle of water sealing fire resistance and explosion venting device to ensure the safety of low concentration gas transportation through water sealing fire resistance and over-pressure automatic explosion venting; this paper analyzes the problems existing in the vertical structure of water sealing fire resistance and explosion venting device for DN1 000 mm gas transmission pipeline, and determines that ZGZS1000 water sealing fire resistance and explosion venting device adopts horizontal structure. Then, based on the principle of gravity settlement and the safe critical velocity of gas, through trial calculation and verification in turn, and considering the economy, the cylinder diameter and cylinder length of ZGZS1000 water sealing fire resistance and explosion venting device are designed. Subsequently, combined with the installation position, explosion pressure and explosion venting pressure of water sealing fire resistance and explosion venting device, the strength and thickness of the cylinder are designed. Finally, a water level control system composed of three water level sensors, a water supply electric valve, a drainage electric valve and a water level controller is designed to realize the automatic control function of water level, so that the water seal height of water sealing fire resistance and explosion venting device is always kept within the effective fire prevention range.

In order to improve the fine management of MA/KA certification and better escort the safety of mining in China, this paper studies MSHA approval for mining products in the United States, including laws and regulations, products categories, approval processes, as well as distinctive practices in issuing versatile approval documents, utilizing social testing resources, and especially approval documents responding to mine operators’ demands. On the basis of the current situation of China MA/KA certification, this paper proposes some suggestions on further improving MA/KA certification in China.

In order to further promote the development of open-pit coal mines with high quality and safety, increase the proportion of open-pit coal output, and enhance the overall level of safety production in China’s coal mines, the analysis of the development situation of open-pit coal mines with high quality and safety and the study of countermeasures are carried out, this paper analyzes the basic development situation of open-pit coal mines in China, puts forward the development trend of open-pit coal mining, and analyzes the short board and difficult problems influencing the safety development of open-pit coal mines, this paper proposes some countermeasures and suggestions for promoting the development of high-quality safety in open-pit coal mines from aspects of promoting the construction of green mines, rectifying and closing mines, formulating and revising standards, raising the level of equipment, building intelligent mines, improving the quality of personnel and standardizing the safety management of contractors, etc. The results show that the safety development of open-pit coal mines should strictly observe the two red lines of ecology and safety, standardize mining and stripping, loading, drilling and blasting, soil discharge, slope, reclamation, outsourcing and other production links, improve the overall level of technical equipment and safety management level, and strictly prevent the accident of death and injury in open-pit coal mines.

Under the background of intelligent construction of coal mine, this paper studies and discusses the construction of AI platform architecture system of the whole coal mine based on video perception, network and information technology as the media, artificial intelligence and big data as the technical support; according to the actual situation of coal mine, the real application scenario is mined and analyzed; the paper carries on research on intelligent sensing, deep learning and intelligent analysis for coal mine equipment status, personnel behavior and environmental changes to realize intelligent alarm and control; the paper researches and analyzes relevant key technologies such as artificial intelligence and deep learning.

In order to study the spontaneous combustion law of close distance easy spontaneous combustion coal seams, taking the mining face of Bulianta Mine No.22 coal seam 3# panel as an example, collected No.22 coal seam samples of Bulianta Mine, three particle size coal samples were selected for programmed temperature rise experiment, the paper analyzed the relationship between the gas concentration generated by coal spontaneous combustion, φ(C2H6)/φ(CH4), φ(C2H4)/φ(CH4), numerical values of R1, R2, R3 and the temperature changes of the coal samples in the experiment. According to the principle of index gases optimization, the gas concentration of CO and numerical value of R2 were selected as the main indexes for predicting and forecasting spontaneous combustion of Bulianta Mine, the gas concentration of C2H4, C2H6 and numerical value of R1 were selected as auxiliary index, the spontaneous combustion critical temperature and dry cracking temperature of Bulianta Mine samples were 60 ℃ to 75 ℃ and 100 ℃ to 120 ℃. Combining with the occurrence features of shallow depth, close distance and easy spontaneous combustion of coal seam, considering the ventilation system in mining face and the condition of mining deployment, by the use of the programmed temperature rise experiment results and theoretical research, the paper comprehensive analyzed the influence factors of spontaneous combustion of close distance goaf. The results showed that the haulage gate, air return way, starting cut and stopping line of the No.22 coal seam goaf, and the remaining coal pillar of overlying goaf were areas prone to spontaneous combustion; comprehensive prevention and control measures such as ground drilling for grouting in coal pillar area of the No.12 coal seam, fixed grouting station for grouting in goaf of the No.22 coal seam, nitrogen injection in goaf of upper and lower coal seams and nitrogen inerting and advance arrangement of working face pressure equalization emergency system are adopted to ensure safe mining of working face and further improve the mine fire warning and comprehensive prevention and control system.

The research on coal breaking mechanism by high-pressure water jet can provide theoretical basis for water jet equipment manufacturing and construction technology research. In this paper, based on the investigation of a large number of related literatures at home and abroad, we summarized the relevant theories of coal breaking mechanism by high pressure water jet. From the perspective of the structure of water jet and mechanical properties of coal, this paper introduces the stress wave theory of crushing, quasi-static elastic fracture theory, the theory of cavitation and broken and crack propagation mechanism of broken coal at all stages about crushing theory researches. In view of the applicability and limitations of various current coal breaking theories, it is suggested that further research can be carried out from three directions: improving the coal breaking mechanism of water jet, two-phase jet and new jet mode.

Aiming at the problem that high power consumption of designed identification card with imported chip leads to frequent battery charging, frequent replacement and difficult maintenance, which is not suitable for the long-term position tracking of various vehicles in the coal mine, a precise positioning identification card based on the domestic chip for mine vehicles is designed. This paper introduces the design of hardware and software to reduce the power consumption of the identification card. The hardware adopts the domestic chip design; the software optimizes the positioning network algorithm and adaptively adjusts the RF transmission power. The test results show that the combination of hardware and software ensures constant positioning accuracy, improves communication distance, reduces product costs, extends the service life of the identification card, and improves the efficiency and turnover rate of underground auxiliary transportation of the vehicles.

With the continuous exploitation of coal resources, the economic losses and casualties caused by coal spontaneous combustion have become increasingly prominent. It is of great significance to study the mechanism of coal spontaneous combustion, coping strategies and utilization of coal fire resources to promote the green prevention and control of coal spontaneous combustion. This paper summarizes and combs the research status of coal spontaneous combustion, mainly reviews the mechanism and prevention technology of coal spontaneous combustion, the thermal dynamic evolution of coal fire disaster and the extraction and utilization of coal fire thermal energy. The purpose is to provide reference for the research and practice in the field of coal spontaneous combustion, and to promote the effective control of coal fire disasters and the rational use of resources.

In this paper, CaCl2 solution was used as an inhibitor. Raw coal was soaked in CaCl2 solution with a mass concentration of 20%, and inhibited coal samples were prepared at different temperature conditions (30 ℃, 50 ℃, 70 ℃ and 90 ℃) for different periods of time. The inhibition effect of CaCl2 solution on coal spontaneous combustion was studied through temperature programmed tests and infrared spectrum experiments. It was found that the content of surface active groups (−CH3, −CH2, −COOH, −C=O) and coal oxygen consumption rate decreased significantly with the increase of pre-inhibition temperature and pre-inhibition time. The inhibition rate and cross point temperature also increase significantly. The results show that increasing the pre-inhibition temperature and the pre-inhibition time can obviously improve the inhibitory effects on the spontaneous combustion characteristics of coal.

Hydraulic cavitation in coal seam can increase the permeability of coal seam and improve the efficiency of gas extraction. However, the analysis and calculation method of throttling control mechanism of hydraulic cavitation bit is still not perfect. In this paper, firstly, the composition of hydraulic cavitation device, the detailed process of hydraulic cavitation, the structure and principle of hydraulic cavitation bit and the mechanism of throttling tube are introduced. Then, the flow inside the throttling tube is simplified into one-dimensional fluid for analysis. According to the continuity equation, momentum equation and Bernoulli equation, the mathematical expression of the pressure distribution inside the throttling tube is deduced, and the pressure distribution curve inside the throttling tube is drawn. Secondly, the simulation model of the throttling tube is established according to the turbulence model, and the pressure distribution and velocity distribution inside the throttling tube are analyzed. Finally, the opening and closing experiment of the hydraulic cavitation bit is carried out, and the relationship between the opening and closing flow and pressure of the hydraulic cavitation bit, the reduction diameter of different throttling tubes and the pressure drop value is studied. This study provides the drilling tool support for gas extraction and permeability enhancement in low-permeability coal seam, and provides the theoretical support for the design of throttling pipe of hydraulic cavitation drill.

According to the characteristics of massive data, system integration and management visualization of coal mine gas efficient control, this paper proposes the research idea of establishing coal mine gas big data management and analysis system based on GIS. On the basis of expounding the characteristics of gas data safety management, this paper designs the overall framework of the system composed of infrastructure layer, business data layer, service platform layer and application platform layer, and studies the technologies such as spatio-temporal data management, gas risk prediction and early warning, and one-map of gas safety management, and develops and realizes the corresponding functions, which provides an important support for coal mine gas safety management.

This paper aims to study the influence of the goaf in the upper coal seam on the overlying ultra-thick coal seam and determine the dislocation distance in the roadway layout of the lower coal seam. Based on finite difference method, this research, takig Tashan Coal Mine as the engineering background, established Mohr-Coulomb and double yield constitutive models to invert the rock strata and the rock mass in the caving zone. The failure law of the ultra-thick coal seam under the influence of the overlying close goaf was studied on the basis of goaf and the residual coal pillar. In addition, the distribution law of stress field and the failure range in the coal seam under the goaf were clarified. With the theoretical analysis and the field borehole peep results, the reliability of the numerical method in this paper was verified, and the inner interlocked distance in the roadway layout of the lower coal seam was determined. The results show that the residual coal pillar has the greatest influence on the mining of the lower coal seam. The stress field under the residual coal pillar forms an approximate “normal trapezoid” influence range in the lower coal seam, with the width of the upper and lower being 32 m and 56 m respectively. The plastic zone under the residual coal pillar is distributed in an “inverted trapezoid” in the lower coal seam, and the width of the upper and lower is 81.36 m and 61.47 m, respectively. The inner interlocked distance of the roadways of the lower seam should be 13.5 m.

In order to effectively control the frequency and probability of the unsafe state of miners, this paper used qualitative research method of grounded theory to analyze 46 related documents and establishes 32 open codes, 11 axial codes, 3 selective codes. We use part of the open codes to establish an index system, and a questionnaire is issued, and safety experts are invited to score the three-level indicators. We use Matlab R2019a to process the data, determine the weight of factors affecting the unsafe state of miners through factor analysis, and determine the weight of factors affecting the unsafe state of miners. The results show that the unsafe state of miners is affected by three factors: individual factors, organizational management factors and environmental factors, of which individual factors account for the largest weight, and the changes in mental fatigue and muscle fatigue can greatly affect the unsafe state of miners. From this, this paper puts forward the countermeasures of shaping intrinsically safe employees, optimizing corporate organization and management, and creating a good working environment.

In this paper, a gas roadway with multiple coal seams in southwest China is taken as the test site, and the separate-layer hydraulic fracturing and multilayers comprehensive hydraulic fracturing are carried out. This paper analyzes the whole process of coal seam fracturing development, discusses the influence of water injection volume in coal seam on subsequent drilling construction, and obtains the distribution law of gas content and water content of coal seam after fracturing, and the gas drainage effect. And the fracturing influence ranges of the two fracturing methods are obtained. The results show that the hydraulic fracturing in coal seam composes of five stages: stress accumulation, fracture initiation, fracture propagation, multiple fracture initiation and propagation, and fracture propagation completion. Compared with the multilayers comprehensive hydraulic fracturing, the average pressure of separate-layer hydraulic fracturing is slightly higher, but the total water injection volume is significantly less. The gas content and water content of coal seam after separate-layer hydraulic fracturing are lower and higher than those of comprehensive fracturing technology, respectively; and the initial gas drainage concentration of coal seam is also higher. In addition, the average gas drainage concentration of single hole and drilling field are 54.1% and 43%, increased by 14.9% and 9% compared with comprehensive fracturing technology. And the effective fracturing influence radius of separate-layer fracturing and multilayers comprehensive fracturing reaches about 50 m and 40 m, respectively. This indicates that the separate-layer hydraulic fracturing technology can significantly improve the effective influence range and effect of seam permeability improvement in coal seam group. Moreover, the separate-layer hydraulic fracturing technology can reduce the water injection volume in coal seam, decreasing the bad phenomena in the subsequent drilling construction of gas drainage borehole, such as sticking drilling.

Underground mining induces the movement, deformation and failure of bedding rock slope in mountainous areas, which develops into geological disasters such as landslides and collapses. In this paper, based on UDEC discrete element method, this paper studies the influence of repeated mining of underground coal seam on the location of bedding rock slope. The results showed that: the subsidence affected by mining decreases with the decrease of buried depth, and the deformation of strata after mining is discontinuous. Compared with single-layer mining, repeated mining will lead to a significant increase in the horizontal deformation of slope. Repeated mining leads to the development of new fractures and fracture groups in the slope, which is more likely to lead to the destruction of the weak structural layer and further reduce the stability of the slope. The dynamic development process of “deformation accumulation-generation-expansion-closure” during single-layer mining will evolve into a dynamic development process of “deformation accumulation-development and expansion-development and stability” during repeated mining.

Aiming at the problems of information chimney, subsystem and data fragmentation in the process of coal mine construction, combined with the acceptance requirements of the comprehensive management and control platform in the Acceptance Management Measures for Intelligent Demonstration Coal Mines(Trial) issued by National Energy Administration, this paper proposes forward the overall architecture design of the intelligent mine integrated management and control platform based on industrial Internet; this paper discusses and studies the key technologies involved in the construction of intelligent mine integrated management and control platform, such as unified data center, centralized monitoring based on three-dimensional and one map, visual configuration centralized control, multi-system and multi-data fusion and linkage. Finally, on the basis of summarizing the architecture design and key technical contents of intelligent mine integrated management and control platform, this paper points out some key problems and research directions to be solved in the construction of intelligent mine integrated management and control platform in the future.

In order to solve the problems of ecological environment caused by the shortage of filling materials and solid wastes in the goaf of coal mine, the paper puts forward some suggestions to solve these problems, in the paper, influencing factors of paste filling body strength were analyzed, and sample strength of filling body was determined by orthogonal test, the correlation between the influence factors and the strength of the filling body was determined with grey relational analysis method, and an improved BP strength prediction model was built, in which the factors affecting the strength of solid waste paste filling are input layer and the strength of the filling body is output layer. The strength test data obtained from orthogonal test were used as training samples and test samples of the network, the fitting ability and generalization ability of network data were tested by analog simulation. Test results show that the established prediction model has fast convergence speed and high accuracy, and its prediction accuracy reaches 93.75%, which indicates accurate prediction of the filling body strength can be realized.

In this paper, the TAW-1000 triaxial test system is used to carry out the triaxial compression test of the complete and single fractured coals under different confining pressures, and the acoustic emission monitoring system is used. This paper analyzes the failure mechanism of fractured coal and rock based on the fracture diagram of fractured coal and the relationship between stress and strain. The results show that: the stress of single fracture coal is more complex than that of intact coal. The stress concentration at the tip of the fracture leads to the formation of micro cracks and the development of connectivity, which makes the coal enter the plastic stage earlier and leads to the significant deterioration of the strength and elastic modulus of coal. The results show that the lateral deformation of fractured coal and rock is more significant than that of intact coal and rock under higher confining pressure; with the increase of confining pressure, the fracture mode of 45° fractured coal and rock presents an excessive failure mode from direct shear failure to oblique shear failure; the stress-strain curve of 60° fractured coal and rock presents a plateform softening, and the change of elastic modulus is not obvious with the increase of confining pressure; under the same confining pressure, with the increase of fracture angle, the mechanical parameters of fractured coal and rock deteriorate significantly with the increase of fracture degree. The fracture dip angle is positively correlated with the ringing number.

In order to promote the safety access system of mining equipment in China to adapt to the development of mine safety management, through combing the current operation mode and existing shortcomings of MA/KA management, the paper studies the safety access system of mining equipment in major mining areas of the world and common analysis with MA/KA. The paper researches production license system and certification system of industrial products in China, and focuses on comparative analysis and learns from special equipment, fire products, railway products, environmental sign products safety access management, key points for safety access system reform of mine equipment. On this basis, this paper explores the reform ideas of the transition to administrative licensing management, national certification and system owners.

Aiming at the problems of short distance, slow speed, large loss and weak anti-electromagnetic interference ability of traditional cable in data transmission of coal mine monitoring system, this paper studies the optical fiber transmission technology and the principle of optical transceiver module, and puts forward a single-mode single fiber optical fiber module transmission scheme between the monitoring equipment terminal such as underground sensors and the monitoring substation. The paper introduces the overall structure of the optical fiber transmission module, the sending and receiving principle of the optical module, and the application of the optical module in the sensor. Combined with the practical application, the signal transmission performance of the optical fiber transmission between the sensor and the monitoring substation is tested, which meets the actual application requirements.

This paper analyzes the development status of wireless positioning technology. On this basis, this paper introduces the current situation of wireless positioning technology in coal mine, and the application of underground positioning system, and focuses on the analysis of the development status of ultra wideband positioning technology, and believes that ultra wideband technology will be a reliable guarantee for the future mine accurate positioning system. Finally, this paper analyzes the safety evaluation method of coal mine personnel positioning system, and gives the specific safety technical requirements of coal mine personnel positioning system.

In view of the problems of the continuous extension of coal seam and the complicated geological conditions in most areas, by referring to the relevant technical data, this paper summarizes the disadvantages gradually appearing in the pressure appearance, ventilation system, hidden trouble management and other aspects in the sequential mining and production layout of the traditional panel area. This paper discusses the characteristics of the production layout of jump mining in various systems, analyzes the advantages of the production layout of jump mining, and puts forward the relevant technical management measures of the production layout of jump mining, which provides a reference basis for the use of the production layout of jump mining in deep complex areas.

In order to effectively detect and identify the dangerous behaviors of underground workers in coal mines and prevent the occurrence of safety accidents, a detection algorithm for dangerous actions of miners based on attention mechanism and deep learning is proposed for the problems of complex background and large scale changes in coal mines. On the basis of the YOLOv3 model, a lightweight feature extraction network with stronger feature extraction capability and smaller volume is designed; in view of the poor detection performance of the original YOLOv3 algorithm on small targets, an attention-based approach is proposed. The feature fusion module of the mechanism optimizes the missed detection and false detection of small targets. In order to evaluate the performance of the model, 10 000 underground coal mine pictures were collected for training and testing. The mAP of the algorithm proposed in this paper is 83.1%, which is 6.6 times higher than the current commonly used target detection algorithms. In addition, the algorithm test speed is 769 fps, which is faster than other light weight object detection algorithms. The experimental results prove that the dangerous behavior detection algorithm proposed in this paper can be applied to the actual production environment.

In this paper, the self-diffusion coefficients (SDC) of CH4/CO2/H2O in coal molecules under different ensemble conditions and the effects of temperature and pressure are calculated by grand canonical Monte Carlo and molecular dynamics (MD) methods. Results indicated that the self-diffusion coefficients of CH4 and CO2 gradually increase with the increasing temperature under the NPT ensemble. The SDC of H2O increases undulatory and it is higher than that of CH4 and CO2 at each temperature, where the diffusion activation energy followed the order of \begin{document}$E({{\mathrm{H}}_2{\mathrm{O}}})

Aiming at the problem of stopping production for communication failure in the belt conveyor protection system, this paper analyzes the characteristics of the query bus and control bus of the protection system, and proposes a grouping communication and bus redundancy mechanism based on the causes and mechanisms of communication failures. The bus redundancy mechanism does not change any hardware and utilizes communication detours to ensure normal communication of the system, at the same time to alert the location and type of failures. By conducting communication tests on 10 devices along the single belt protection system, including multiple failures on the query bus, single failure on the control bus, and composite faults on the query/control bus, the problem of single failure stopping production was solved, and the communication robustness of the system was improved.

In order to study the characteristics of smoke flow when fire occurs in underground coal mines, and then accurately analyze the state of smoke flow, the flow state of the flue gas in the natural state at 10 s is simulated in this paper to determine the approximate stage of the ignition and smoke production, which is used as a reference for the subsequent experiments; the 3-dimensional particle image velocimetry (3DPIV) was utilized to photograph the open, closed and sealed conditions of the tunnel, and the start/stop control of the fan with a fixed wind speed of 1 m/s was combined to study the motion of the smoke flow under different conditions. The results show that: the open smoke flow of the roadway is relatively simple, and once the roadway is closed, the smoke cannot be diffused, and complex flow changes will occur in high concentration of smoke, such as laminar flow, excessive flow, turbulence, countercurrent and bifurcation of the smoke flow, etc. When the roadway is closed and sealed, the smoke flow "gushing" will occur. At this moment, the flow state of the smoke flow is complex and changeable, but the smoke flow will be stable after a certain period of time.

In order to solve the problem of hydraulic fracturing presure relief and permeability improvement technology applied in underground field due to the substandard sealing and control quality, in this paper, on the basis of summarizing the existing hole sealing materials and sealing methods at home and abroad, through a large number of basic experiments, the influence of auxiliary materials such as ordinary cement added with special composite cement, swelling agent and water reducing agent on the basic properties of anti-high pressure sealing materials such as setting time, fluidity, compressive strength and swelling multiplication rate was studied. The best water-cement ratio of 0.5, 20%-25% of special composite cement, 4% of compound expander and 1.6% of naphthalene water reducer were determined to ensure the early strength and high strength of the anti-high-pressure sealing material with the premise of flowability and expansion rate. It also conducted on-site industrial experiments in Pinggang Coal Mine of Longmei Coal Group, and its parameters such as solidification time and compressive strength met the performance requirements.

Coal mine underground reservoir water storage technology has become one of the important ways for the coordinated development of coal resource mining and water resource protection in western mining areas of China, and the stability of coal pillar dam body is one of the key factors for coal mine underground reservoir to be able to be used safely and for a long time. To investigate the destabilization characteristics of coal pillar dams in underground coal mine reservoirs under complex conditions, this paper is based on FLAC3D numerical simulation and secondary development to investigate the influence on the stress evolution characteristics and stability of coal pillar dams under the sequential action of adjacent workings mining and water flooding in the mining area in a mine in northern Shaanxi Province. The results show that the stress distribution of the coal pillar dam body shows a bimodal shape after the mining of the working face is completed. The peak value gradually decreases with the increase of the width of the coal pillar. At the same time, the elastic core area accounts for less than 40% of the critical instability index when the width of the coal pillar is 20 m, and instability will occur. After water storage in the mining area, the increment of the plastic zone of the coal pillar dam body under flooding shows the change law of “stable-increasing-decreasing-stable”, which can well simulate the progressive damage characteristics of “seepage-weakening-damage-seepage” of the coal pillar dam body under flooding. The stress distribution of the coal pillar dam body gradually evolves into an arch-shaped distribution. It tends to average out, and the peak stress is greatly reduced, while the internal plastic zone is further expanded and the percentage of its elastic core zone is reduced. The smaller the width of the coal pillar is, the greater the reduction is.

To gain a profound understanding of the current status and future trends in the comprehensive prevention and control of coal spontaneous combustion, this paper comprehensively reviews stages and research progress in the aspects of “monitoring and early warning, prevention technology, and emergency rescue”. The following future research aspects are proposed: utilizing advanced technologies such as comprehensive multivariate statistical analysis, the Internet of Things (IoT), machine learning, and artificial intelligence to enhance the accuracy of coal spontaneous combustion prediction and forecasting. This involves constructing an intelligent, proactive warning, and situational judgment mechanism to achieve intelligent prediction, forecasting, and proactive warning systems. Through the comprehensive application of interdisciplinary research methods, gaining in-depth insights into the spontaneous combustion mechanism, innovative fire-resistant materials, and the development of new microbial technologies, theses make the technology of spontaneous combustion prevention and control of coal present a trend of in-depth research and multiple innovation. Under the framework of an efficient, collaborative, and intelligent rescue mechanism, the emergency rescue for coal spontaneous combustion is advancing towards a more intelligent and information-oriented direction. The goal is to promote the intelligent advancement of the coal spontaneous combustion prevention and control level.

In view of the complex transportation route of coal mine, there are many forks and corners in the roadway, which is easy to bring hidden dangers to the safety of underground transportation. In this paper, a method for identifying the intersection and curve of trackless rubber-tyred vehicle in coal mine is designed. Firstly, the method structured the midline points to form a roadway map. Secondly, the direction of travel is determined by using the vehicle position relationship at adjacent moments. Thirdly, combined with the structural attributes of the roadway map, it is determined whether there is a fork or curve in front of the vehicle. Then, the Dijkstra algorithm is used to solve the shortest path from the current position of the vehicle to the suspected target, and then determine whether it is the opposite target. Finally, with the help of the vehicle terminal, the driver is provided with a safe voice prompt. The method is tested in a mine. The results show that the functions are running normally, and the logical response time is about 32 ms.

Aiming at the problem that it is difficult to accurately locate the borehole for gas drainage in coal mine, this paper analyzes the common borehole location methods currently used in coal mines, discusses the main problems existing in these methods, and proposes the spatial visualization borehole projection location technology. In this paper, the technical principle, algorithm research, technical characteristics and technical innovation of spatial visualization drilling projection positioning technology are described in detail, and the technical feasibility is analyzed, this technology can solve the problem of quickly demarcating the hole position, dip angle and azimuth angle of the gas drainage boreholes in different areas of outburst prevention measures, the method can realize the projection and calibration of multiple boreholes at one time, avoid the error caused by manual calculation and setting-out, and save the positioning time of boreholes in drilling field. The research results show that the time of demarcating a drilling site by the technology of visual borehole projection location in underground space of coal mine is not more than 30 minutes, which is 80% higher than the traditional method in time effect.

This paper analyzes the problems of the main fan in Zhaogu No.1 mine, such as the long operation time of the fan reversing, the equipment fault information is not found in time, and the electrical protection settings are not reasonable. The paper puts forward the automation, information and intelligent transformation and upgrading of the main fan, and formulates the automatic online monitoring, system early warning alarm, reasonable electrical protection settings and other solutions.

This paper introduces the intelligent supervision system of vehicles and drivers in large-scale open-pit operation site. The intelligent supervision system is divided into two types: one is the standard intelligent supervision system which adopts the scheme of deploying intelligent inspection post on the job site to supervise the staff, that is the regional supervision system; the other is the enhanced intelligent supervision system which adopts the supervision scheme of distributing intelligent terminals to all vehicles and personnel, that is the dynamic supervision system of the whole range. This paper discusses the composition, function and work flow of the standard intelligent supervision system, and the composition, function and work flow of the vehicle management subsystem and personnel management subsystem of the enhanced intelligent supervision system.

This paper puts forward the definition of intelligent ventilation system, analyzes the key technology of intelligent ventilation in coal mines, and studies the accurate acquisition algorithm based on the parameters of mine detection and monitoring system. An adaptive optimization method of mine ventilation network based on minimum regulated power consumption is established to realize the on-demand air distribution in coal mines. The simulation and real-time calculation system of mine ventilation is established. The intelligent optimization algorithm is applied in the optimization of mine ventilation system and the decision measures of the intelligent adjustment of wind resistance fan. Taking the No.8272 working face of Yangdong Coal Mine of Jizhong Energy Fengfeng Group as the experimental object, the reliability of the key technology of intelligent ventilation proposed in this paper is verified.

To ensure the safety of the workers in the fire danger of the blind coal roadway and reduce the economic losses caused by fire, the combination method of theoretical analysis and practical experience is used to analyze the cause of blind coal roadway fire and summarize the fire characteristics. This paper expounds the technical measures for emergency firefighting and the safety protection measures for combat personnel on site under three different fire conditions of the blind coal roadway. From the four aspects of living space, air duct protection, real-time monitoring and rescue environment, this paper focuses on the rescue technical measures for the trapped people in the blind coal roadway fire, which provides the reference for fire prevention and control of coal enterprises in China, so as to achieve the maximum control of human casualties and economic losses caused by the fire accident in the blind coal roadway.