2019 Vol. 45, No. 12

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Control practice of thick and hard roof based on deep-hole pre-splitting blasting
LIU Xiao
2019, 45(12): 1-6. doi: 10.13272/j.issn.1671-251x.2019100029
<Abstract>(72) <HTML> (17) <PDF>(14)
Abstract:
In view of problem of strong mine pressure on working face with thick and hard roof, taking 11313 working face of Panbei Mine as engineering background, based on theoretical analysis of breakage characteristics of main roof, deep-hole pre-splitting blasting scheme of thick and hard main roof was formulated, and stress evolution law of surrounding rock under different thickness of deep-hole pre-splitting blasting and distribution of advancing abutment pressure under effective thickness of deep-hole pre-splitting blasting were studied by numerical simulation. The simulation results show that stress arch rotates to the side of transport roadway, stress arch height increases with the increase of blasting thickness and stress arch shape changed from spoon to ellipse. When thickness of main roof pre-splitting blasting is 12 m, influence range of advancing abutment pressure and distance between peak abutment pressure and coal wall of the working face increase by 8.5 m and 18.8 m respectively compared with that before the blasting, and advancing abutment pressure concentration coefficient decrease from 1.67 before blasting to 1.3 after blasting. The field monitoring results show that after the pre-splitting blasting of thick and hard main roof, the maximum load and average load of support in lower of working face decrease, dynamic load coefficient of support fluctuates significantly, and rib spalling of coal wall is effectively controlled.
Research on safe advancing speed of spontaneous combustion isolated working face
JIANG Xiyi
2019, 45(12): 7-11. doi: 10.13272/j.issn.1671-251x.2019050010
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Abstract:
The risk of rock burst is a natural property of isolated working face. The anti-shock decompression will affect normal advancing speed of isolated working face and increase risk of spontaneous combustion of coal seam.Therefore, when determining safe advancing speed of isolated working face, the requirement of anti-impact must be considered.In view of problem that rock burst risk is seldom considered in determination of safe advancing speed of isolated working face, 93down05 working face in Jining No.2 Coal Mine was taken as a research object to analyze oxygen-poor characteristics in upper and lower adjacent goaf at stopping line and distribution law of dangerous area of the goaf in working face, the following conclusions were obtained: when O2 volume fraction is 6%, the time for the coal sample to oxidize from initial condition to critical temperature is 253 d，and the working face mining should be completed within 253 d; considering fire prevention requirements, the minimum advancing speed of the working face is 3.7 m/d; considering rock burst prevention requirements, optimized safe advancing speed ranges of unprotected area and protected area are 3.7-5 m/d and 5.04-8 m/d, respectively. The advancing speed not only guarantees coal spontaneous combustion safety on three sides of goaf during mining of 93down05 working face, but also does not bring new rock burst risk to the working face, and ensures safe mining in the production cycle of the working face.
Comprehensive three-dimensional gas drainage mode based on directional drilling technology
HAN Bing
2019, 45(12): 12-16. doi: 10.13272/j.issn.1671-251x.2019040026
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Abstract:
Applications of directional drilling technology in extracting solid coal by bedding borehole, extracting goaf by high borehole, extracting pre-excavated area crossing fractured zone and so on were analyzed by taking Chengzhuang Coal Mine as an example. A comprehensive three-dimensional gas drainage mode based on directional drilling technology was researched. Bedding progressive modular drainage technology is applied to solid coal-seam, which can realize benign replacement of mining quantity and drainage quantity through long-time and large-scale drainage and cyclic progress among pre-drainage model, tunneling face and mining face. Roof high directional borehole drainage technology is applied to gas accumulation region at upper corner under U type ventilation. High directional boreholes and upper corner form a connection system through fractured zone, and gas in goaf is extracted by the borehole through fracture, so as to decrease gas concentration in goaf. Comb-like directional borehole technology in coal-rock-coal type roof is applied to fractured coal-seam. Main boreholes are arranged in roof. Comb-like branch boreholes are constructed and enter coal-seam after the main boreholes cross fractured coal body, so as to protect next roadway tunneling. Combined comb-like directional borehole technology of gas drainage on top and water drainage at bottom is applied to coal-seam watering. Water drainage boreholes in coal-seam and gas drainage boreholes in roof can realize connection of gas-water flow field in space, and water-drainage pressure-decrease by the boreholes in coal-seam is good for gas drainage by the boreholes in roof. Gas drainage rate of Chengzhuang Coal Mine achieves 60% by use of the gas drainage mode.
Quantitative evaluation of mine structure complexity and its coupling analysis with water bursting
LIU Wei, WU Jiwen, HU Ru, BI Yaoshan, ZHAI Xiaorong, XU Feng
2019, 45(12): 17-22. doi: 10.13272/j.issn.1671-251x.2019040102
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Abstract:
Most mine inrush accidents are closely related to mine geological structure, so accurate evaluation of mine structure complexity is of great significance for mine water disaster prevention and control. Taking Xuzhuang Coal Mine as a research object, fault fractal dimension value, fault intensity index and folding plane deformation coefficient were selected as evaluation indexes affecting mine structure complexity. The independent weight coefficient method was used to determine weight of each evaluation index. The quantitative evaluation model of mine structure complexity was established by ArcGIS to divide the study area into the most complex structure area, more complex structure area, middle complex structure area and simple complex structure area, and coupling relationship between mine structure complexity and mine water bursting was analyzed. The results showed that the study area is dominated by the most complex structure and mine structure complexity is mainly controlled by large faults and folds. The water bursting points are more densely distributed with increase of mine structure complexity when fault fractal dimension value, fault intensity index and folding plane deformation coefficient become greater. It indicates that mine structure has an obvious control effect on water bursting.
Coal mine safety risk assessment based on cloud model and combination weighting
GAO Tong, ZHANG Ruixin, GAO Saichao, HE Qian, LIU Yun
2019, 45(12): 23-28. doi: 10.13272/j.issn.1671-251x.2019060020
<Abstract>(69) <HTML> (15) <PDF>(13)
Abstract:
For problems of weak foundation, single means and weak objectivity of coal mine safety risk assessment in China, a coal mine safety risk assessment model was constructed based on cloud model theory and combination weighting method of subjective weighting by AHP and objective weighting by grey correlation analysis. Firstly, a coal mine safety risk assessment index system is established, which includes 5 first-level assessment indexes of personnel, equipment, environment, management and history，and 29 second-level assessment indexes. Then, cloud model scale of the coal mine safety risk assessment indexes is established. Finally, digital characteristics of index layer, criterion layer and target layer in the coal mine safety risk assessment index system are calculated by use of safety risk assessment cloud model to get coal mine safety risk assessment cloud. The model has been applied to safety risk assessment of Hongqingliang Coal Mine. The results show that safety risk level of the coal mine is medium at present, and the main factors affecting safety production are operation rate of operators against rules, stability of coal-seam roof and floor and other indexes, which provides a certain reference for safety management and risk prevention and control of coal mine.
Aging indexes analysis of explosion-proof lithium battery based on incremental capacity method
CHEN Jiyong, WU Zhaohong, LI Jinxi
2019, 45(12): 29-34. doi: 10.13272/j.issn.1671-251x.2019080003
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Abstract:
State of health(SOH) in existing battery management system(BMS) for mine-used locomotive powered by explosion-proof lithium battery is only used to predict remaining service life of the battery, but not for cause analysis of battery aging, which has no guiding significance for battery maintenance. In order to solve the problem, internal factors leading to lithium battery aging were analyzed firstly that were lithium ion loss, dissolution of active substances and increase of internal resistance. Then an aging indexes analysis method of explosion-proof lithium battery was proposed which was based on incremental capacity(IC) method. According to height and transverse position of IC curve of lithium battery, lithium battery aging caused by lithium ion loss, dissolution of active substances and increase of internal resistance were analyzed quantitatively to obtain corresponding aging indexes. Finally, methods of calculating lithium battery IC and determining peak and valley of IC curve in BMS were introduced. The influences of charge and discharge number and charge and discharge ratio on battery aging were analyzed by battery charge and discharge tests The test results show that with increase of charge and discharge number, explosion-proof lithium battery aging is mainly caused by loss of lithium ion and dissolution of active substances when it is operated with a small charge and discharge ratio. Increasing charge and discharge ratio of the battery has the greatest influence on battery aging caused by increase of internal resistance. The method is good for BMS of explosion-proof lithium battery to estimate SOH more correctly and can provide basis for battery maintenance and BMS parameters setting.
Load measurement method of vertical shaft construction hoisting system based on torque current
CAI Yusheng, DENG Shijian, XU Jingyu, GAO Xu
2019, 45(12): 35-39. doi: 10.13272/j.issn.1671-251x.2019050047
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At present, load measurement method of mine hoisting system is mainly to measure load by adding a weighing sensor at the bottom of the shaft, but this method cannot be applied to vertical shaft construction hoisting system.The method of measuring hoisting load by analyzing functional relationship between wire rope tension and load has realized dynamic measurement of load. However, it is difficult to solve measurement accuracy problem caused by sensor installation and plastic deformation of wire rope itself, which brings hidden danger of safety. To solve the above problems, in view of situation that electric drive system of hoisting system is AC/AC inverter vector control of asynchronous motor, a hoisting load measurement method based on torque current was proposed according to torque current can be directly output by inverter. By establishing mathematical model and dynamic analysis of hoisting system, correlation between torque current and hoisting load is determined; on the basis, particle swarm optimization-least squares support vector machine was introduced to establish relationship model between torque current and hoisting load at three running stages of acceleration, uniform speed and deceleration;different disturbances are applied to the load at each running stage, and the relationship between hoisting load and torque current is analyzed by Matlab simulation. The simulation results show that there is a correspondence between hoisting load and torque current at each running stage, the torque current can accurately restore the hoisting load and its fluctuation.
Experiment of amplitude and frequency feature of acoustic emission during Brazilian splitting testing of natural and saturated coal samples
CHEN Tongqing, SHEN Rongxi, LI Hongru, HOU Zhenhai, ZHANG Xin
2019, 45(12): 40-44. doi: 10.13272/j.issn.1671-251x.2019030045
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Abstract:
In order to study influence of water on mechanical and acoustic emission (AE) characteristics of coal samples during tensile and rupture, Brazilian splitting test was carried out on natural and saturated coal samples, and the AE waveform information was studied by spectrum analysis. The test results show that during the tensile and rupture process, distribution range of the saturated coal sample dominant frequency signal is lower than that of the natural coal sample. In destruction stage, the saturated coal sample releases less energy than the natural coal sample, and its maximum amplitude of dominant frequency is lower than the natural coal sample. The natural coal sample AE signal is mainly low-frequency low-amplitude, medium-frequency low-amplitude and high-frequency low-amplitude, and the low-frequency and high-frequency tend to shift to the middle-frequency band when the coal sample ruptures. The saturated coal sample AE signals is mainly low-frequency low-amplitude, and the low-frequency high-amplitude and medium-frequency low-amplitude increase when the coal sample ruptures. The low-frequency high-amplitude signals correspond to the large scale cracks generated during the coal sample rupture. When the saturated coal sample ruptures, the number of low-frequency high-amplitude signals is more than that of natural coal samples, which reflects that the large scale cracks generated during the rupture of the saturated coal sample are more than other cracks.
Accelerated test of working stability of mine-used laser methane sensor
WANG Xiaosong
2019, 45(12): 45-49. doi: 10.13272/j.issn.1671-251x.2018100034
<Abstract>(78) <HTML> (12) <PDF>(10)
Abstract:
In view of problem that existing sensor working stability test method requires continuous operation and testing of sensor for 180 days with low efficiency, feasibility of accelerated test of working stability of mine-used laser methane sensor is analyzed;it is found out by thorough test that temperature is the main factor affecting long-term measurement error stability of laser methane sensor; accelerated test temperature was determined to be 75 ℃ according to temperature limits of laser methane sensor components and the whole machine; the Arrhenius equation is used to establish an accelerated test model of work stability, and acceleration factor is calculated to be 8.718 34; combining verification test scheme of failure rate and the mean time between failures under the assumption of constant failure rate, an accelerated test method for working stability of laser methane sensor is obtained, which can shorten the test time from 180 d to 12 d. The feasibility of the accelerated test method is verified by experiments in combination with the test results of third-party testing agencies. The proposed accelerated test method can greatly improve the efficiency of inspection work and provide theoretical support for the development of industry standard test methods for laser methane sensor.
Research on mining stress distribution law of overburden under typical key strata structure
ZHANG Shaohua, ZHANG Yuchen, LIU Yiming
2019, 45(12): 50-53. doi: 10.13272/j.issn.1671-251x.2019060026
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Most researches on coal-seam abutment pressure are carried out based on homogenizing overburden structure of working face at present, while influence of internal structure of the overburden is not fully considered. For the above problems, based on key strata theory of ground control, mining stress distribution law of overburden under typical key strata structure was researched using numerical simulation through changing location and thickness of key strata. The research results show that with distance increase between key strata and coal-seam, advance abutment pressure peak value in working face decreases gradually, the peak value in soft rock under key strata decreases firstly then becomes stable, the peak value in soft rock over key strata increases firstly then becomes stable, and range of stress concentration area decreases. With increase of key strata thickness, the peak value in working face increases firstly then becomes stable, the peak value in overburden increases gradually, and range of stress concentration area increases.
Research on optimal operating point tracking of inductive coupled power transmission system
WANG Qiting, WEI Yewen, ZHOU Jianfei, LI Yingzhi
2019, 45(12): 54-59. doi: 10.13272/j.issn.1671-251x.2019050003
<Abstract>(45) <HTML> (7) <PDF>(8)
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In view of problem that working state of traditional inductive coupled power transmission (ICPT) system deviates from optimal operating point as the load changes, H-bridge converter is introduced to replace traditional compensation capacitor in ICPT system, and dynamic adjustment of compensation capacity and tracking of optimal operating points are achieved by changing its trigger angle. Compensation capacity-load matching mathematical model under optimal operating point of ICPT system is established according to circuit mutual inductance theory. The maximum power point is used as the optimization target, and ICPT topology and impedance matching control method based on dynamic compensation of H-bridge converter are given. Matlab simulation results show that the range of trigger angle α of H-bridge converter is α<40°; experimental results show that the ICPT topology based on dynamic compensation of H-bridge converter has good dynamic compensation characteristics, which can automatically track the optimal operating point of ICPT system as the load changes.
Converter design of underground high voltage direct current system
LI Shan, PAN Tao, NI Chunming, WANG Yingjie, WANG Yajuan
2019, 45(12): 60-67. doi: 10.13272/j.issn.1671-251x.17463
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For existing status of larger power supply load, power supply distance and active power loss of power supply system in coal mine underground and problems of low voltage and flicker at load side, modular multilevel converter-high voltage direct current(MMC-HVDC) system was applied to underground power supply system. Topology, mathematical model and parameters and controller design schemes of modular multilevel converter (MMC) in the system were mainly introduced. Underground MMC-HVDC system consists of two MMCs namely rectifier converter and inverter converter. Rectifier converter adopts double closed-loop control structure of fast current inner-loop control and constant DC voltage and constant reactive power outer-loop control, and inverter converter adopts constant AC voltage control. Both MMCs adopt carrier phase-shift PWM strategy and voltage equalizing strategy based on energy equipartition control and voltage balance control. Simulation experiments of the underground MMC-HVDC system were carried out in PSCAD/EMTDC software. The results show that the underground MMC-HVDC system has good dynamic response in steady-state operation, realizes independent control of active and reactive power, and improves DC transmission efficiency. When the system is disturbed by underground load variation, it can regulate active and reactive power rapidly and stabilize DC transmission voltage, and stabilize amplitude and phase of inverter converter output voltage at rated values.
Design of simulation software of mine safety monitoring substatio
XING Shaomei, LIU Haifeng
2019, 45(12): 68-74. doi: 10.13272/j.issn.1671-251x.2019050083
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The traditional testing method of coal mine safety monitoring central station monitoring system is to test function and performance of the system by hooking up multiple substation equipments, which not only requires a large amount of hardware cost and complex testing process, but also cannot effectively find potential defects of the system. In view of the above problems, a practical simulation software of coal mine safety monitoring substation was designed. The software adopts data simulation technology, IO multiplexing technology and WebSocket real-time communication technology, and can simulate working mode of substation equipment in real time, interact with the central station monitoring system in action state, and can trigger the abnormal scene dynamically, simulate the concurrent behavior of multiple substations. Meanwhile it can comprehensively test the communication transmission accuracy, timeliness, parallel processing ability and continuous reliability of the central station monitoring system. The test results show that the substation simulation software can take place of substation equipment and simulate vast majority of application scenarios, and can quickly and effectively diagnose flaws of the central station monitoring system from real-time data collection and monitoring, network transmission stability, memory consumption situation, abnormal alarm monitoring, can effectively improve repair cycle of central station monitoring system, which provides guarantee for the stable operation of the central station monitoring system in production environment.
Application of edge computing in control system of shearer
ZHANG Yang, DU Zhiwe
2019, 45(12): 75-80. doi: 10.13272/j.issn.1671-251x.2019090082
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In shearer control system based on remote cloud computing, most of the shearer original data calculation is performed in remote cloud platform, which has problems such as low reliability of data transmission and long time delay, and cannot meet requirements of real-time calculation in the unmanned control of shearer. To solve the above problems, a kind of shearer control system based on KubeEdge edge computing was proposed. Taking application of high precision location and machine vision detection of shearer as examples, the realization method and test of the edge computing architecture based on KubeEdge in the control system of shearer was introduced. The test results show that the application of the edge computing in the control system of the shearer realizes calculation and processing of relevant data of the shearer on the edge side and synchronization of calculation and processing results on remote cloud platform, implements data communication and synchronization of remote cloud platform of shearer, namely the edge node is responsible for the calculation data, remote cloud platform is responsible for the display results, which solves problems of low reliability of data transmission and long time delay existed in control system of shearer based on remote cloud computing. Edge computing and remote cloud computing jointly build a new shearer control system network application platform, which is the research direction of unmanned application of shearer control system.
Design of standardized information management system for coal mine safety productio
ZHANG Jianrang, HUANG Yuxin, YAN Zhenguo, ZHANG Lei, HUO Xiaoquan
2019, 45(12): 81-85. doi: ZHANG Jianrang1
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In view of problems of single information management method, information input and output delay, and lack of mining and analysis of business data in current coal mine safety production information management system,a standardized information management system for coal mine safety production was designed. The system builds a virtual private network to directly serves all personnel and special services for safety production management;through a variety of smart terminals and PC web terminals, various processes of predetermined process are coordinated to obtain accurate information support from the private network, and the private network is fully responsible for the follow-up processing requirements; key functions of the private network are extended to a variety of smart terminals to achieve "4A" information management mode which enables anyone uses any terminal at any time and any place. The system uses Miracast protocol and WiFi network to perform multimedia content transmission, analysis, display, control and other operations on different multimedia terminals, so as to achieve multi-screen linkage system control. At the same time, the system introduces Apriori algorithm for association analysis, improves and optimizes the algorithm based on multi-dimensional and multi-layer characteristics of the accident hazard data, and establishes an automatic mining and analysis subsystem at the background of the system to realize multi-dimensional and multi-level mining analysis of accident hazards. The actual application results show that the system improves timeliness of business processing, improves the level of coal mine safety production management, and the level of intelligent handling of coal mine emergency response.
Research on precise positioning system of coal mine underground
CHEN Wei
2019, 45(12): 86-90. doi: 10.13272/j.issn.1671-251x.17409
<Abstract>(191) <HTML> (9) <PDF>(20)
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For low position precision of existing personnel positioning system of coal mine underground based on RFID, ZigBee, WiFi and so on, a precise positioning system of coal mine underground was proposed which combined visible light communication with inertial navigation system. In the system, underground LED lighting lamp is taken as LED visible light positioning base-station. Visible light signal is received by CMOS camera in intelligent information mining-lamp for positioning. Data of acceleration sensor and gyro in intelligent information mining-lamp is timely integrated to get moving track and direction of underground personnel. Data of inertial navigation system could be corrected through intelligent information mining-lamp identifying ID coding information of LED visible light positioning base-station for anew positioning, so as to realize precise positioning. Eight LED visible light positioning base-stations are arranged in coal mine underground. Positioning precision of the system is tested through five intelligent information mining-lamps moving at normal speed. The results show that positioning error of the system is less than 1 m, which meets precision requirements of personnel positioning in coal mine underground.
Practice of gas drainage by high-level directional borehole in Qinglong Coal Mine
MENG Xiangjun, CHEN Gonghua, RUAN Guoqiang, ZHANG Binbin, GUO Ying
2019, 45(12): 91-96. doi: 10.13272/j.issn.1671-251x.2019060073
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Aiming at problems of gas drainage by high-level borehole such as too many boreholes, insufficient single borehole depth, uncontrollable borehole trajectory, low gas drainage concentration and discontinuous drainage, in order to effectively prevent and control gas concentration overrunning in upper corner of 21602 mining face in Qinglong Coal Mine, gas drainage was carried out by use of high-level directional borehole technology. Design and construction schemes of high-level directional borehole were introduced, and the best borehole layout parameters were determined through field practice. The results show that high-level directional borehole has the characteristics of high gas drainage concentration, large drainage volume and high drainage rate, and gas drainage effect of high-level directional borehole tends to stabilize first and then decreases with the increase of mining distance. When the final hole of high-level directional borehole is 39 m away from roof and 55 m away from right side of return airway, gas drainage effect is the best with gas drainage volume fraction reaching 30.5%, gas drainage flow reaching 18 m3/min and gas drainage pure volume reaching 2.374 m3/min. Gas volume fraction in upper corner is reduced to the range from 0.2% to 0.4%, which is up to 0.72% before extraction. It effectively solves problem of gas concentration overrunning in upper corner.
Design of output filter of mine-used high-voltage inverter for long-distance power supply
WANG Qian, CAO Na
2019, 45(12): 97-100. doi: 10.13272/j.issn.1671-251x.17487
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For problems of frequent IGBT faults of inverter and motor whistling when mine-used high-voltage inverter supplies power for a long distance, causes were analyzed which were high-voltage inverter's working characteristic causing output waveform to contain high order harmonics and long-distance power supply transmission. A design scheme of output filter of mine-used high-voltage inverter for long-distance power supply was proposed according to output waveform characteristics of inverter. Parameter calculation methods of electric reactor and capacitance in the filter were introduced. The simulation result show that voltage waveform at motor side is smooth without voltage spikes and peaks when the filter is installed at side of mine-used high-voltage inverter for long-distance power supply. Prototype test results show that higher harmonics at motor side are eliminated when the filter is installed, and total harmonics distortion is less than 5%.
Design of software test platform for SAP integrated pressure pumping system
GUO Zijian, LI Junshi
2019, 45(12): 101-105. doi: 10.13272/j.issn.1671-251x.2019080040
<Abstract>(121) <HTML> (17) <PDF>(11)
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In order to solve problems existed in software test of SAP integrated pressure pumping system such as low accuracy of input signal simulation and inconvenient operation, few detection channels of output signal, long check time of point table parameters and complex wiring, a software test platform for SAP integrated pressure pumping system was designed. The upper computer management software controls module groups to simulate input signal and transmit it to controller. After the input signal is collected by the controller, point table parameters are changed and transmitted to the upper computer management software. According to the input signal, the controller executes corresponding logic judgment and outputs control signal, which is collected by the module group and transmitted to the upper computer management software. The upper computer management software judges test result automatically according to whether the control signal matches the input signal. The application of the test platform improves efficiency and accuracy of test.

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