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Table of Content

    30 December 2023, Volume 33 Issue S2
    Safety social science and safety management
    Study on coal mine risk hidden danger evaluation system
    LI Lin, ZHANG Jinpeng, FU Ensan, LIU Guangwei
    2023, 33(S2):  1-6.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0027
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    The untimely disposal of the hidden danger, the weak correlation among the various hidden dangers, and the insufficient quantification between the hidden danger and the accident risk in coal mines are major problems to be solved. First, by collecting the data of the ″trinity″ system of coal mines, semantic recognition was performed, and the disaster accident chain in coal mines and the risk evaluation model were established to quantify and analyze the risk in coal mines. Then, a risk evaluation system for coal mines was built, including comprehensive risk dynamic evaluation, professional risk dynamic evaluation, hidden danger time distribution, hidden danger location distribution, self-checking risk evaluation coincidence analysis, repeated hidden danger data analysis, hidden danger importance analysis, and hidden danger year and keyword analysis of coal mines. The results show that the quantitative expression, visual display, and pre-warning of all kinds of disasters and risks in coal mines can be realized by the semantic recognition of hidden risks in coal mines, providing technical support for reducing the accident risk and ensuring timely closed-loop disposal of hidden dangers.

    Safety engineering technology
    Wettability of dust from blast piles in Ha'erwusu open-pit coal mine and its influencing factors
    LI Quansheng, YAN Jie, WANG Bin, ZHANG Yu
    2023, 33(S2):  7-12.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0032
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    In order to enhance the dust suppression effectiveness of dust suppressants, the wettability of dust from blast piles in open-pit mines and their influencing factors were investigated. The coal dust and rock dust generated from different blasting stages at the Ha'erwusu open-pit coal mine were taken as research objects. Various methods, including indoor experiments and statistical data analysis, were employed to analyze the physicochemical characteristics of explosive dust particles from open-pit coal mines. Based on this analysis, the relationship between physicochemical characteristics and wettability was discussed. Regression analysis using SPSS software was conducted to establish a regression model. The final regression equation revealed the primary factors influencing the wettability of dust from blast piles in open-pit coal mines. The results indicate that the significant factors influencing the wettability of coal dust are fixed carbon content and D50. The significant factor affecting the wettability of rock dust is D50.

    Fault characteristic analysis of belt conveyor rollers based on sound signal
    LIU Yong
    2023, 33(S2):  13-17.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0036
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    To address the problems of massive and dispersedly distributed rollers in belt conveyors, low accuracy, susceptibility to environmental impact, and high monitoring costs of existing fault diagnosis methods, a diagnosis method based on sound signals was proposed. Firstly, the sound signals of 30 sets of rollers of the belt conveyor under working conditions were collected through a BOURNS omnidirectional microphone. Then, statistical methods were used to analyze TD features of the collected sound signals, achieving preliminary fault feature mining. Finally, FD and TFD features of the sound signal were analyzed to improve the ability to express fault features. The results show that TD features of the roller sound can detect rust faults. FD features can detect serious faults, and TFD features can detect various typical bearing damages, having application prospects in the monitoring of roller faults in industrial belt conveyors.

    Geo-mechanical testing of surrounding rocks in roadway of Maiduoshan coal mine
    ZHANG Weijun, ZHANG Zhijia, XU Haidong, WANG Shunxiang, ZHAO Whenju, LAN Tianwei
    2023, 33(S2):  18-22.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0012
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    In order to optimize the surrounding rock support scheme for the roadway of Maiduoshan coal mine, the in-situ test of ground stress and surrounding rock strength in the roadway of Maiduoshan coal mine was carried out. The structure of the surrounding rocks in the roadway was observed by the borehole peeping method, and its morphology was thus revealed. The appropriate measuring points were selected for the test of ground stress under hydraulic fracturing. The surrounding rock strength was tested by the borehole penetration method. The geomechanical distribution characteristics and mechanical parameters of surrounding rocks in the No. 6 coal seam of Maiduoshan coal mine were analyzed. The test results show that the average value of the maximum horizontal principal stress in Maiduoshan coal mine is 15.2 MPa, and that of the minimum horizontal principal stress is 8.17 MPa. The average value of the vertical principal stress is 13.94 MPa. The ground stress field in the test area is a medium stress value area. The average strength of surrounding rocks in the No. 6 coal seam in the region is 28.16 MPa, and the coal is relatively hard. In the range of 10 m of surrounding rocks in the roadway, there are siltstone, coarse sandstone, and siltstone in different depths. The strength of rock mass increases, and the strength of rock mass increases by 95.41 MPa at 4.9 m.

    A self-moving tail control method based on improved GWO algorithm
    JU Xingjun, WEI Dezhi
    2023, 33(S2):  23-27.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0013
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    In order to better control the attitude of a self-moving tail, the improved GWO algorithm was integrated into the PID controller, and a fuzzy controller was designed. An optimized fuzzy PID control system architecture based on improved GWO was proposed to realize the safety control actions of the tail including self-moving, synchronous lifting, and side-moving correction. The mathematical model of the hydraulic control system of the self-moving tail of the belt conveyor was established, and the simulation of the side-moving control of the self-moving tail and the synchronous lifting control of the multi-hydraulic cylinders of the self-moving tail was designed. The results of PID control without algorithm and fuzzy PID control optimized by GWO algorithm before and after improvement were compared by simulation analysis. The results show that the fuzzy PID controller and the improved GWO algorithm can make the safety control system of the self-moving tail more stable and more efficient.

    Research on reliability of advanced support equipment for step sliding of broken roof
    HU Zhiwei, LIU Shaojie, XIE Miao, SHI Zhongding, LIU Zhixiang
    2023, 33(S2):  28-33.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0030
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    In order to solve the problems of roof collapse and roof fall accidents caused by untimely support during the mining process of tunnel surrounding rock, a step sliding-type advanced support equipment was proposed, and its reliability was studied using simulation methods. Firstly, the composition and principle of the sliding-type advanced support structure were introduced, and the functional reliability of the support effect was clarified. Then, the overall structural strength of the advanced support equipment in both fully supported and stepping process states was simulated and analyzed to verify the rationality of the design of the advanced support equipment. Finally, modal analysis was conducted on the advanced support equipment using ANSYS Workbench to obtain different vibration mode patterns of the equipment. The results show that the maximum deformation of the advanced support equipment in the fully supported state occurs at the front end of the longitudinal beam (with a value of 22.139 mm); the maximum stress is located at the hinge of the front and rear supporting longitudinal beams (with a value of 205.45 MPa), and the location where the equivalent strain is concentrated is located in the intersection area of the arched crossbeam and the supporting longitudinal beam (with a value of 11.624×10-4). In the stepping process state, the maximum deformation of the advanced support occurs on the front longitudinal beam of the auxiliary support group (with a value of 13.411 mm); the maximum stress of the support occurs at the hinge of the supporting longitudinal beam and the arched crossbeam (with a value of 187.65 MPa); the maximum displacement of the pushing oil cylinder occurs at the hinge of the piston rod head and the auxiliary support group (with a value of 5.633 2 mm), and the maximum stress occurs at the hinge of the main support group (with a value of 187.65 MPa). The first, second, third, and fourth natural frequencies of the machine are 41.715 2, 44.591, 60.826, and 62.789 Hz, respectively. The deformed parts are located on the front support column and the rear support column of the auxiliary support group.

    Research on intelligent warehousing system of civilian explosive materials
    CAO Yong
    2023, 33(S2):  34-40.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0040
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    In order to improve the safety of warehousing management of civilian explosive materials, an intelligent warehousing system was developed to improve the storage and transportation efficiency of civilian explosive materials and reduce security risks, so as to realize the functions of real-time object monitoring, automatic inventory, and security early warning. Firstly, the concept of civilian explosive materials was defined. Secondly, the current safety management measures for civilian explosive materials were briefly explained. Then, the intelligent warehousing system was summarized and designed, mainly including demand analysis, overall design, and hardware and software design, and then it underwent hardware and software tests. The results show that the intelligent warehousing system of civilian explosive materials based on Internet of Things technology and big data processing has significant advantages in improving storage and transportation efficiency and reducing security risks. Through scientific and reasonable test design and execution, the reliability, stability, and ease of use of the system can be ensured, so as to provide users with high-quality intelligent warehousing services.

    Research on fault detection method for middle section idler of belt conveyor
    JING Qinghe, ZHANG Qiliang, WANG Zengren, LIU Dongxing, XIE Miao, MENG Qingshuang
    2023, 33(S2):  41-48.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0009
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    In order to timely and accurately determine the safe operation status of the idlers and reduce their fault operation, the vibration signal characteristics of the idlers under normal working conditions, bearing damage, and fracture in the middle section of a mining belt conveyor were studied based on the actual operating conditions. The vibration signals collected were denoised using DWT and decomposed into the sum of several product function (PF) components through LMD. The components with high correlation coefficients were selected for further analysis, and the extracted best features were used as inputs to the BPNN. A BPNN was constructed to classify the operation status of the idlers, and a diagnostic test of the operation status of the idlers was conducted on a mining belt conveyor. The experimental results show that the DWT-LMD-BPNN algorithm can accurately identify the types of idler faults and locate idler faults, achieving advanced warning of idler faults in the middle section of the belt conveyor. The accuracy of detecting idler faults by integrating the DWT-LMD-BPNN method can reach 93%, which can provide a research basis for building an intelligent monitoring platform for belt conveyors in the future.

    Rock breaking model of downhole drilling rig used in open-pit mine
    YU Haixu
    2023, 33(S2):  49-54.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0038
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    In response to the problems of deformation and rupture of the main structure caused by excessive impact force and the unstable vibration of equipment in the process of rock breaking by impact force during the operation of the downhole drilling rig, the downhole drilling rig for open-pit mines was taken as the research object to analyze the rock breaking characteristics under drilling conditions. Firstly, the rock breaking mechanism of the downhole drilling rig by impact force was analyzed to obtain the main modes of rock breaking under impact load. Secondly, by comparing the yield and breaking criteria of the model, the Drucker-Prager model was used to analyze the rock fragmentation effect under the impact of the drill bit. Finally, ABAQUS software was used to analyze the rock breaking characteristics by impact force under different drilling parameters. The results show that when the impact force is too small, and the rotation speed is too high, the force of the drill bit on the rock is not enough, leading to low drilling efficiency. When the rotation speed is too small, and the impact force is too large, the rock is not completely destroyed, and it is difficult to discharge debris, resulting in a poor crushing effect. As the rotation speed increases, the drilling speed first increases and then decreases. As the impact force increases, the energy of the drill bit invading the rock increases, resulting in an increase in drilling speed. However, excessive pushing force can cause unstable drilling of the drill rod, leading to an unsatisfactory rock breaking effect and affecting the drilling efficiency.

    Neural network-based fault diagnosis algorithm for vibration feeder
    ZHANG Bin, ZHANG Xinxin, YANG Haitao
    2023, 33(S2):  55-59.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0019
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    To address the lack of adaptability in traditional signal processing methods for vibration feeder fault diagnosis, an adaptive 1D CNN-based fault diagnosis algorithm was introduced. Through an in-depth analysis of the fault characteristics of the vibration feeder, the original vibration signals of fault states were preprocessed to construct training and testing samples. Each training sample was partitioned over time and served as the input for the 1D CNN, enabling adaptive hierarchical extraction of vibration signal features at different time intervals. The results show that by introducing adaptability, the algorithm can adapt more flexibly to complex dynamic patterns in vibration signals. This adaptability results in higher diagnostic accuracy, especially when facing frequent changes in vibration characteristics or the presence of noise interference. After selecting appropriate neural network dimensions, the algorithm outputs diagnostic results for fault states in the vibration feeder. With an overlap ratio of 49%, the accuracy reaches 90.2%.

    Gas control technology by static pressure water injection in borehole of Weijiadi coal mine
    WEN Jiandong, LIU Xuan, LI Zuoquan, MIAO Zaiquan, WANG Beibei
    2023, 33(S2):  60-64.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0014
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    In order to reduce the concentration of gas and dust during the mining of the mining face, the 1st coal seam of the east 1100 mining face in the east 1 mining area of the Weijiadi coal mine was taken as the research object, and the gas and dust control test of coal seam by water injection was carried out. Static pressure water injection was adopted to inject water into the coal seam of the mining face, and the single-hole water injection volume was calculated to be 6.9 m3. The water injection time was 1.7 h, and the water injection position was set at about 16 m in front of the mining face. By measuring the moisture change of coal samples at different positions from the water injection borehole in the mining face, it was concluded that the infiltration radius of the water injection hole was about 10 m. The results show that water injection in the coal seam can not only reduce the average gas volume fraction in the return air flow but also control the gas desorption index and the maximum amount of drilling cuttings in the coal seam, and it can ensure a reasonable change of the gas volume fraction in the upper corner.

    Research on deviation coupling control of safety retractor of high bench cables for open pit mines
    LIU Lijie, ZHOU Yongli, TIAN Feng
    2023, 33(S2):  65-70.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0023
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    In order to optimize the cooperation and working accuracy of the internal motor assembly of the safety retractor of high bench cables used in open pit mines under a disturbed environment, a three-motor deviation coupling control method was proposed for the retractor. Firstly, a PI controller parameter setting model based on the SOA was constructed, with the ITEA as the objective function. Subsequently, the proposed method was compared with various algorithms by using three test functions, including Schaffer. Finally, three simulation models of permanent magnet synchronous motors (PMSMs) were built using MATLAB/Simulink, and the parameters were optimized through algorithms. The results show that the three-motor deviation coupling control method optimized by the SOA enables the motor assembly's speed to rapidly reach the set value with excellent stability. Moreover, even when disturbances are introduced, the motor assembly still exhibits good tracking and anti-interference capabilities. Additionally, this approach boasts advantages such as rapid convergence and lower error rates, providing robust support for the design and optimization of the safety retractor of high bench cables used in open pit mines.

    Design of noise management diagnosis system for coal preparation plants based on pickup array
    LIAN Kai
    2023, 33(S2):  71-76.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0006
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    Coal preparation plants fail to monitor noise in the work area and provide early warning for equipment failure based on noise in real time. To address this issue, a noise management diagnosis system based on BS architecture was designed, which consisted of a noise acquisition subsystem and a noise time-frequency analysis processing module. The noise acquisition subsystem utilized a pickup array to collect noise, while the noise time-frequency analysis processing module employed array technology and time-frequency analysis algorithms to reduce and locate noise. To facilitate the management and analysis of noise data, a user management and analysis interface based on BS architecture was developed. The results show that the noise management diagnosis system is capable of analyzing and processing noise data from various types of equipment, locating the noise, and displaying noise levels in real time. It can also generate detailed comparative analysis reports and identify noise pollution that exceeds standard thresholds, thus facilitating the diagnosis or repair of equipment.

    Research on influencing factors of air pollution in open-pit mines based on environmental safety improvement
    WANG Guilin, ZHAO Changhai, SONG Delin
    2023, 33(S2):  77-84.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0021
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    In order to understand the air pollution situation in the mining pit and develop effective control measures, the three-dimensional monitoring system of air quality in open-pit mines was established based on the bucket shovel. The meteorological elements, dust concentration, CO concentration, and other parameters in the mining pit were continuously monitored. By comparing the frequency and concentration of pollutants, the main pollutants were determined. By analyzing the changes in dust concentration with meteorological factors, the impact of each factor on mining pit pollution was determined. The research shows that the frequency of CO generation is much lower than that of PM10 and PM2.5, and dust particles are the main atmospheric pollutants in the mining pit. Temperature, humidity, and wind speed are the main influencing factors of pollutants. As temperature increases, and humidity decreases, dust concentration increases. As wind speed increases, wind erosion and dust generation have a significant effect, resulting in an increase in dust concentration. Measures to increase humidity can be taken to reduce dust pollution in the mining pit, while exposed surfaces should be managed to reduce the impact of wind erosion and dust generation.

    Research on intelligent application of gas pumping stations
    LI Shengya, GAO Kun, ZHANG Binfeng, WANG Yongjian, JIA Nan, GAO Hongye
    2023, 33(S2):  85-90.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0029
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    In order to improve the automation and information level of gas pumping stations in coal mines and reduce the energy consumption of gas pumping stations, the intelligent control method of gas pumping stations was put forward. Based on the objective analysis of the causes of high energy consumption of gas pumping stations, the intelligent pumping system of gas pumping stations was put forward. The method of intelligent transformation of the pumping system of gas pumping stations was adopted. By adding a frequency converter control motor to the water ring vacuum pump, the energy consumption of gas pumping and power generation data of gas power plants were further analyzed. The results show that the intelligent gas pumping station can reduce the energy consumption of gas extraction by more than 50% under the condition of safe production. The work intensity of the labor force was reduced by 80%.

    In-situ stress measurement and characteristics analysis of mine field stress field in Maiduoshan coal mine
    LIU Xiangyang, LIU Yonghao, ZHANG Shunfeng, LAN Tianwei, ZHAO Wenju
    2023, 33(S2):  91-95.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0016
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    In order to study the impact of different tectonic stress zones of Maiduoshan coal mine on the mining engineering and mine dynamic disasters, the ground stress of the No. 6 coal seam of Maiduoshan coal mine was measured by the hydraulic fracturing method. A database of the lithology of the roof of the No. 6 coal seam of Maiduoshan coal mine and a model of the geological structure of the coal rock were constructed, and the stress distribution and zoning characteristics of the mine field of Maiduoshan coal mine were determined by the rock stress state analysis system. The results show that Maiduoshan coal mine belongs to a typical slip-type stress field, namely a tectonic stress field dominated by horizontal stress, with a maximum principal stress of 15.02 MPa and a direction of N15.6°E. The mine field is divided into four stress zones, namely, high stress zone, stress gradient zone, stress normal zone, and low stress zone, accounting for 7.5%, 8%, 57.5%, and 27% of the area of the mine field, respectively. In the high stress zone and stress gradient zone, the superimposed influence of mining disturbance can easily lead to the occurrence of roof falls and heaving floor in the roadway, in the stress normal zone and low stress zone, the roadway is less influenced by the stress of the original rock, which is not easy to produce the energy accumulation, and the danger of roadway damage is reduced. For the roadway that is being dug and not put into use, the monitoring and support of the roadway surrounding rock should be strengthened according to the characteristics of the stress zones, so as to realize the hierarchical and zonal management of coal mining engineering and disaster prevention and control and guarantee the safety of coal mine production.

    Correlation analysis of mining stress and working face outburst index
    XIE Yadong, WU Qixuan, LI Zuoquan, ZHANG Jianjiang, QUAN Jiye
    2023, 33(S2):  96-99.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0015
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    In order to accurately predict the risk of coal and gas outbursts in the mining face, the east 1100 working face of Weijiadi coal mine in Gansu Province was taken as the research object, and the influence factors of mining stress on the outburst index were studied. By using the method of mathematical statistics and combining with the situation of the mine field, the quantitative relationship between the gas pressure of the coal seam and the desorption index of the drilling cuttings was studied, and the relationship between the mining stress and the gas outburst index was deduced. Through the observation of the mine pressure of the mining face, the gas outburst index of the coal body in a certain range could be quantitatively analyzed, and the distribution of the mining stress of the coal body could be judged by measuring the gas outburst index. The results show that mining stress has a certain influence on the gas outburst index. The mining stress and the desorption index of the drilling cuttings can be derived from each other. The fitting function between the two is quadratic. With the increase in mining stress, the desorption index of drilling cuttings and the maximum amount of drilling cuttings increase first, gradually stabilize, and then increase rapidly, indicating a positive correlation.

    Thoughts and suggestions on construction of technological support capacity for work safety of hazardous chemicals
    JI Guofeng, ZHANG Jialiang, GUO Shuai
    2023, 33(S2):  100-104.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0043
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    In order to effectively prevent systemic safety risks in the hazardous chemical industry, the current situation and technological support needs of work safety for hazardous chemicals in China were sorted out. The shortcomings in the construction of technological support capacity for hazardous chemical safety in China were analyzed from the aspects of rapid detection of hazardous chemicals, safety and intelligence, and safety improvement of chemical industrial parks. Suggestions were proposed to strengthen the technological support capacity for work safety of hazardous chemicals. Research has shown that technological support capacity for safety is an important means of preventing and resolving systemic safety risks in the industry. Continuously strengthening the construction of technological support capacity for safety can effectively improve the level of safe management of hazardous chemicals and promote the continuous and stable improvement of work safety of hazardous chemicals. It is also necessary to continuously strengthen the construction of technological support capacity for safety in terms of scientific research platforms, institutional mechanisms, and support services. By building a national-level science and technology platform, the research and development capabilities of key technologies and equipment for the safe management of hazardous chemicals can be strengthened. By establishing a cooperation and sharing mechanism among institutions with technological support capacity for the safety of hazardous chemicals in China, an ″ecosphere″ of technological support capacity for safety can be built. By strengthening the team of experts and talents, technological support service capacity for safety can be enhanced.

    Inversion and zoning characteristics of in-situ stress field in Limin Coal Mine
    DONG Haiqing, LAN Tianwei, YUAN Yongnian, LING Xiangdong, LI Yabin, LI Yang
    2023, 33(S2):  105-110.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0011
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    In order to prevent the deformation and failure of roadway surrounding rock and support caused by stress concentration in the process of mining, it is necessary to clarify the distribution characteristics of in-situ stress in the mine field. According to the regional tectonic analysis and plate tectonic movement situation, the dynamic source and evolution characteristics of the stress field formation in Limin coal mine were revealed. Through the in-situ stress test in the mine field, the principal stress direction and value of the in-situ stress field were determined, and the horizontal tectonic stress field of Limin coal mine was identified with the main advantage. The maximum horizontal principal stress direction was S85.78°W-S89.93°W, and the direction was nearly EW. The roof lithology database and rock stress calculation model of the No.9 coal seam were constructed to invert the distribution characteristics of the maximum principal stress in the mine field, and the tectonic stress zoning of the mine field was carried out according to the stress concentration coefficient. The differences in the stability of roadway surrounding rock in different tectonic stress zones were analyzed. The results show that the surrounding rock in the high stress zone changes the most, and the energy accumulation is the most concentrated. The critical scale of stress concentration in roadway surrounding rock is smaller, and strong mine pressure is more likely to occur.

    Analysis of influencing factors of safe passing capacity of large materials in crushing station
    DU Zhiyong
    2023, 33(S2):  111-115.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0017
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    In order to improve the efficiency of material crushing and solve large material jamming in open-pit mine crushing stations, the bulk material model and the mathematical model of material particle size were established. Firstly, the factors affecting the crushing force of the material were analyzed, and the mathematical models of crushing force under the action of different factors were established. Then, the CR610/14-35 double-toothed roller crusher was taken as an example, and the force of different materials under different center distances and tooth heights of the toothed roller was numerically simulated. The results show that the particle size, the center distance, and the tooth height of the toothed roller are the main factors affecting the passing capacity of large materials in the crushing station, and the tangential force of the material decreases with the increase in the center distance of the toothed roller and increases with the increase in the tooth height of the toothed roller.

    Roller fault diagnosis based on MFCC sound feature signal extraction
    GUO Jie, JING Qinghe, YAN Shouqing, WANG Xin, XIE Miao, WU Yibing
    2023, 33(S2):  116-121.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0008
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    In order to monitor the healthy operation state of the roller, the normal audio signal and the abnormal audio signal of the roller were extracted through the field test. Since the extracted audio signal contains a lot of noise, an improved wavelet threshold denoising method was proposed in this paper. This method effectively filtered out the noise in the audio signal and laid a foundation for the later feature extraction of the signal. In order to further study the characteristic difference between normal audio signal and abnormal audio signal, the MFCC feature extraction method was used to obtain an MFCC feature characterization map which could obviously show the difference between normal state and abnormal state of the roller. The results show that the time domain diagram and spectrum diagram of the abnormal audio signal fluctuate more violently than the normal audio signal; the MFCC feature characterization map of the normal audio signal of the roller is higher than the initial amplitude of the abnormal audio signal, and the amplitude decreases more slowly.

    Research on characteristics analysis and intelligent monitoring system of hydraulic system of open-pit mine excavators
    ZHANG Zhouai, HAI Sufeng, XUE Guoqing, ZHANG Yuhua
    2023, 33(S2):  122-127.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0039
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    To prevent equipment failures caused by damage to hydraulic system components during the operation of hydraulic excavators in large open-pit mines, research on performance analysis and intelligent monitoring systems of hydraulic excavators during the operation process was carried out. A 350 t hydraulic excavator was taken as the research object. The main pump model and the whole system model of the excavator system were established based on AMESim simulation software. The independent motion characteristics of the working arm, vibration rod, and working bucket of the hydraulic excavator were simulated. The intelligent monitoring platform architecture of the hydraulic system of open-pit mine excavators including a data monitoring system, data transmission system, and intelligent analysis system was established and successfully applied in the Shenhua Baorixile open-pit mine. The results show that compared with the change law of the displacement and pressure of the hydraulic cylinder during the independent working process, the pressure during the composite motion process is higher and fluctuates due to the vibration and load effects that occur in various stages of the actual working process. The designed intelligent monitoring platform of the hydraulic system can realize the real-time and effective monitoring of the hydraulic system state of the mine excavator and can greatly improve the stability of the hydraulic system of the mine excavator.

    Prediction of motion stability of large shovel hydraulic excavators based on ADAMS
    JIA Feng, SU Honggang, RONG Bao, WEI Zhidan, WEI Lidong
    2023, 33(S2):  128-134.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0033
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    In order to improve the controllability and stability of the working device of a large shovel hydraulic excavator, the working device of a 350 t shovel hydraulic excavator was studied. Firstly, the basic structure of the shovel hydraulic excavator was introduced. Based on the D-H method, the forward and inverse kinematics solutions of the working device were solved, and the coordinates of each hinge point of the excavator working device and the displacement and angle change functions of the boom, bucket rod, and bucket cylinders were obtained. Then, the software Matlab was used to verify the displacement and angle function model, and the function change curve was obtained. Finally, SolidWorks and ADAMS were used to establish a virtual prototype of a 350 t large shovel hydraulic excavator. The kinematics simulation of the boom cylinder, bucket rod cylinder, and bucket cylinder of the working device was carried out, and the displacement curve was drawn. The simulation curve obtained by comparative analysis was compared with the function model curve obtained by Matlab. The results show that the displacement function curves of the boom, bucket rod, and bucket cylinder obtained by the D-H method are basically consistent with the simulation curves obtained by ADAMS simulation. The accuracy of the theoretical value and the simulation value is proved.

    Reliability analysis and research on loading bracket at the entrance of gangue warehouse
    ZHANG Yuefei, WANG Qiang
    2023, 33(S2):  135-139.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0025
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    In order to study the structural strength of the loading bracket at the entrance of a gangue warehouse, the three-dimensional structural model of the main parts of the loading bracket of a gangue warehouse was constructed by using solidworks software. Then, according to the actual loading situation, in the process of gangue loading, the strength and deformation of the bracket at the entrance of the gangue warehouse were analyzed to verify the reliability of the bracket. Finally, the created 3D model was imported into Ansys workbench for static analysis. The stress and strain analysis diagrams of the main parts were obtained under the correct constraints. The results show that when there are six support pulleys, the maximum load of the support pulley is 83.921 MPa; the load of the quantitative warehouse is 21.104 MPa, and the maximum deformation is 1.588 6 mm, which meets the requirements of the loading bracket of gangue.

    Research on dynamic characteristics of spraying system of mine sprinklers based on AEMsim
    WANG Han, TANG Yadong, YANG Guoji, YANG Baocheng, ZOU Qi, XIE Miao
    2023, 33(S2):  140-144.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0003
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    The open-pit mine sprinkler is unable to autonomously adjust the spraying volume based on road dust concentration. To solve this problem, a variable spraying system powered by an engine and a swash plate plunger pump was designed. The mathematical model of the spraying system was designed, and the nozzle diameter of the spraying system was calculated to obtain the dynamic characteristics of the spraying system. The AMESim simulation model of the spraying system was established, the affects of the key parameters such as engine speed, plunger pump opening, and nozzle diameter on the spraying volume of the spraying system were analyzed by parametric simulation. The results show that increasing the tilt angle of the plunger pump and enhancing the engine speed can improve the stability of the system. The nozzle diameter of the variable spraying system is 2 mm. The nozzle enters an oscillation state and gradually stabilizes after 1.1 s. When the tilt angle opening of the swash plate is 0.95, it first enters an oscillation state and tends to stabilize. When the engine speed is 3 000 r/min, the oscillation time is short, which can reduce the system response time.

    Research progress on types and properties of mine dust suppressants
    TANG Xiaoqian, WANG Tao, ZHU Junpeng
    2023, 33(S2):  145-151.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0031
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    In order to clarify the design principles, proportions, mechanism, and dust suppression effects of various types of mine dust suppressants, the research status of dust suppressants for underground and open-pit mines was summarized. The types of raw materials and dust suppression effect of the wetting dust suppressants and environmentally friendly adhesive dust suppressants were studied. The results show that the research on wetting dust suppressants is the key for dust suppressants for underground mines, including the physical and chemical essence of coal dust wettability, as well as the dust suppression effect and micro mechanism of different wetting dust suppressants. The consolidation performance of adhesive dust suppressants used in open-pit mines is the most important. The action principle of the new environmentally friendly dust suppressants mainly involves the dust suppression effect under natural polymer aggregation, microbial adhesion, and biomass material bonding. In view of the significant differences in the effectiveness and poor universality of various dust suppressants, future research needs to focus on refined dust suppressant research and development, standard dust suppressant performance tests, and theoretically guided research and development methods of dust suppressants.

    Research of dust reduction and spraying system for mining sprinklers
    LU Lixin, DU Zhiyong, SUN Guosi, TANG Yadong, DU Yongzhi, XIE Miao
    2023, 33(S2):  152-157.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0004
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    The spraying system for mining sprinklers failed to autonomously adjust the amount of water sprayed based on the concentration of road dust. In view of this, a variable spraying system for mining sprinklers was designed. A simulation model of the variable spraying system was established using AMEsim software, and the pressure, flow, and system power changes of the variable spraying system experienced by the sprinkler on horizontal, uphill, and downhill sections were analyzed and compared with those of the quantitative spraying system. A parameterized analysis of the influence characteristics of pipeline diameter on nozzle pressure in the variable spraying system was conducted. Fluent parametric simulation software was used to analyze the impact of vehicle speed on the spraying system, and the influence characteristics of vehicle speed on the mist spraying process were obtained. The results show that engine speed above 1 700 r/min in the spraying system for the sprinkler can effectively maintain system stability. When the system pipeline diameter is 50 mm, the maximum pressure of the system is 0.508 8 MPa, and the average pressure is 0.456 MPa, which maintains the pressure of the spraying system.

    Research on motion characteristics of manipulator for intelligent water filling stations in mines
    HAI Sufeng, YU Jingbin, LI Jinhui, TENG Chunyang, XIE Miao, MIAO Chong
    2023, 33(S2):  158-163.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0007
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    In order to solve the operation vibration of the manipulator for the existing intelligent water filling station in the open-pit coal mine and avoid the safety problem caused by the vibration, the four-degree-of-freedom manipulator was taken as the research object to study the motion characteristics of the manipulator. The improved D-H parameter method was used to establish the coordinate system, and the forward and reverse kinematics simulation was carried out through the kinematic equation. The manipulator model of the water filling mechanism of the water filling station was established, and the position of the end effector of the manipulator model was sampled by the Monte Carlo method of Matlab. The working space cloud map of the manipulator was obtained, and the working position that the manipulator could reach was determined, so as to plan the stop position of the water equipment for water filling. The five-order polynomial interpolation algorithm was used to plan the joint motion space of the manipulator, and the path points in the Cartesian space were converted into the corresponding joint angles to realize the motion control of the manipulator and obtain the position, velocity, and acceleration curves of each joint. The results show that the velocity and acceleration of the manipulator rise and then decrease stably, and each joint moves stably. There is no impact and vibration. The trajectory planning observes stable velocity and no impact and vibration, which ensures the high working efficiency and stability of the manipulator and improves its safety performance.

    Characteristicanalysis of spraying system of intelligent mine sprinklers based on Fluent
    YU Jingbin, RONG Bao, ZHAO Ziwei, BAO Weiwei, SHI Yinfang
    2023, 33(S2):  164-169.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0034
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    In view of the ″blind spot″ of underground automatic dust prevention and the low intelligence of the mine sprinklers, a variable spraying system of intelligent mine sprinklers was developed. Firstly, the spraying model was established by using SolidWorks software and ANSYS Fluent simulation software. Secondly, the influence of wind velocity on the spraying range of the sprinkler under different working conditions was analyzed. Finally, the spraying range of the sprinkler under four wind velocity conditions of 0.9, 3.45, 4.4 m/s, and 6.7 m/s was simulated and verified. The results show that when the nozzle diameter is constant, the output of water mist particles of the nozzle is affected by the water velocity of the nozzle, and with the increase in water flow, the output of dust particles increases, and the spraying amount of the spraying system increases. At the same water velocity, with the increase in wind velocity, the fog droplet particles are affected by the wind, and the captured particles falling to the ground decrease, or in other words, the spraying range decreases. Therefore, when the dust reduction area is fixed, with the strengthening of the environmental wind field, the water flow should be appropriately increased to improve the spraying uniformity and effective dust reduction effect.

    Study on safety monitoring technology for chain fracture in crushing station of open-pit mine
    WEI Dezhi, DU Zhiyong, TENG Chunyang, XIN Wutian, LI Zekun
    2023, 33(S2):  170-175.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0035
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    The detection efficiency of the chain fracture of the conveying mechanism in the crushing station of the open-pit mine is low, and the processing efficiency of the traditional image recognition method is low, with poor real-time detection performance. To address these issues, a chain fracture detection technology of the crushing station based on deep learning technology was put forward. Firstly, the overall design scheme of the chain fracture detection system was proposed in terms of the hardware platform construction and software architecture. Then, the YOLOv4 model was used to build the chain detection model architecture, and the chain fracture detection algorithm was developed according to the operating conditions of the crushing station. The image preprocessing method was proposed according to the actual environmental characteristics. Then, image samples were collected for iterative training of the model, and the chain target detection and recognition model was obtained. Finally, the chain fracture loss was detected. The results show that the chain target detection of the crushing station based on deep learning can accurately identify the number of chains in the image during the operation of the conveying mechanism, and when the chain is occluded for simulated loss, the model can send a warning in time.

    Open-pit truck scheduling optimization method based on SA-CSA
    TIAN Feng, TANG Xiaoqian, QIAO Dongqing
    2023, 33(S2):  176-181.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0022
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    In order to improve the transportation efficiency of open-pit trucks and reduce mining costs for mine enterprises, minimizing the comprehensive cost of open-pit truck transportation scheduling was set as the objective function, and constraints such as ore production, grade balance, and transportation time were considered. The SA method and the CSA were combined, and the SA-CSA algorithm was employed to optimize the scheduling of open-pit trucks. A large-scale open-pit mine was studied, and the optimization results of the SA-CSA with those of the SA algorithm and CSA were compared. The results indicate that the SA-CSA exhibits superior solution accuracy and convergence speed compared with the SA algorithm and CSA.

    Novel optimization algorithm for cable RFID positioning technology
    JIAO Xiaoliang, GUO Anbin, ZHANG Jianyu, SU Hongjun
    2023, 33(S2):  182-187.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0024
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    To solve the RFID positioning problem in the intelligent management of cables in the open-pit coal mine, a method to optimize the RFID positioning accuracy based on the IWOA was proposed. RFID technology was used to locate the electronic tag and read the information, and RSSI value was utilized to calculate the measurement distance between the reader and the tag. Then the distance error was optimized through the improved whale algorithm, and the positioning accuracy of the system was reflected by the position coordinate error value selected by iterative search. The results show that the average positioning error of the system optimized by the IWOA is 0.024 1 m. Compared with the traditional LANDMARC, differential evolution (DE)-RFID, and whale optimization algorithm (WOA)-RFID positioning methods, the average error is smaller, and the positioning accuracy is increased to 97.8%, which can more accurately locate the electronic tag.

    Research on dust diffusion characteristics of dragline stacking process in open-pit coal mine
    WANG Yu, JIAO Xiaoliang, ZHAO Changhai, SONG Delin
    2023, 33(S2):  188-194.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0005
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    The Heidaigou open-pit coal mine adopts a throwing blasting-dragline stacking process to remove the overlying rock of the coal seam, and the production process has a significant impact on the air quality of the mining pit. In order to effectively control dust, understand the properties and diffusion characteristics of the main atmospheric pollutants in mining pits, and develop effective air quality control measures for mining pits, the method of on-site sampling and testing was used to study the concentration and dispersion of dust generated by loading. On this basis, the numerical simulation method was used to study the dust diffusion process in mining pits. The results show that at a radius of 100 m in the dragline workplace, the highest dust concentration is 12.5 mg/m3, and the respiratory dust concentration is 1.8 mg/m3. The proportion of dust of < 5 μ with the greatest harm to people is 77.2%. Dust first accumulates in the dumping pit and then overflows to the platform where the dragline stands. As the wind speed increases, the maximum diffusion distance of the dust cluster gradually increases, and the position of the maximum dust concentration gradually moves away from the dust production point, moving towards the position where the dragline stands and showing other diffusion characteristics.

    Research on fault detection algorithm of rollers of coal conveyer belts
    JIRI Gele, LIU Yao, SHANG Shuhong
    2023, 33(S2):  195-201.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0002
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    The fault detection of rollers of coal conveyor belts currently relies on manual inspection, which lacks clear standards and has low efficiency. Data statistical analysis, artificial intelligence localization algorithms, and image matching technology were used to investigate the fault detection of rollers of coal conveyor belts. Through statistical analysis of roller abnormalities, it was found that shaking was the primary form of roller abnormality, resulting in a certain angular deviation between the roller and the fixed frame and thus affecting operational safety. Therefore, a detection algorithm for roller position deviation was proposed. The rotary object detection based on the YOLOv7 model was used to detect the position and angle of the rollers. Historical images were collected and matched with captured images in real time to compare the roller loss status and deviation angles and identify visual anomalies of the rollers. The results show that the roller detection accuracy is 99.7%. Under low-light shooting conditions, the detection rate of roller loss faults is 99.8%, and the detection rate of faults where the roller angle changes by more than 5° is 94.5%.

    Analysis of influencing factors of TBM penetration under ″full and half sections″
    XU Bingnan, ZHAO Xinhe, CHEN Liangwu, LI Kun, ZHANG Wenyan, XU Ruipeng
    2023, 33(S2):  202-208.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0028
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    In order to explore the variation characteristics of hard rock tunnel boring machine (TBM) penetration under different working conditions, taking the TBM excavation drainage corridor project of Jinyun Pumped Storage Power Station as an example, the construction technology of tunnel line intersection is analyzed. The force of TBM cutter is analyzed, the rock breaking model of single cutter is established, and the rock breaking process of cutter is explored by finite element analysis software. According to the actual excavation data, this paper analyzes the relationship between TBM excavation parameters and rock parameters under half-section-full-section conditions. The results show that under the condition of half-section tunneling, the penetration of TBM increases logarithmically with the increase of cutterhead thrust, and also increases logarithmically with the increase of cutterhead torque. Under the full section condition, the penetration of TBM shows an exponential function and a linear function growth trend with the increase of cutterhead thrust and cutterhead torque, respectively, and the growth rate is related to rock parameters.

    Research on mechanism of high-quality conformal grinding of carbon brushes based on a new device
    LI Qingjian, BAI Tong, ZHANG Jinpeng, WANG Da, XIE Miao, TIAN Bo
    2023, 33(S2):  209-215.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0026
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    To solve the problem of poor conformal grinding effect of carbon brushes used in phase-shifting cameras and improve the grinding quality of carbon brushes, a new type of carbon brush grinding device was first adopted to analyze the process of conformal grinding of carbon brushes and the friction mechanism of the friction contact surface. Secondly, a kinematic model of the structure was established, and Adams simulation was used to analyze errors. Then, under the influence of system bias, the friction mechanism was analyzed from both macro and micro perspectives. Finally, through theoretical relationship calculation, the influence of roughness on friction under this system bias was analyzed, and the relationship between roughness and friction was explored. The results show that the device has high reliability, but there are still trace system deviations, with deviation values ranging from 0.002 to 0.017. Through formula deduction and analysis, it is found that the wear rate at the macro level decreases exponentially, while at the micro level, a three-body friction is formed. There is a positive correlation between the friction force between the carbon brush and the grinding wheel block and the standard deviation of the contour height of the contact surface between them.

    Research on automatic identification and location technology of water filling nozzle used in open-pit mines
    ZHAO Zhongqi, YU Haicheng, BAI Baoshan, XIE Miao
    2023, 33(S2):  216-221.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0010
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    To solve the problems of slow speed and resource waste caused by manual centering of the water filling nozzle during water filling operation of an emergency sprinkler in open-pit mines, a laser radar point cloud-based automatic identification and location method for water filling nozzle of the sprinkler was proposed, so as to achieve automatic centering of the water filling nozzle and improve the efficiency and accuracy of water filling. According to the position parameters of the water filling structure, sprinkler, and laser radar, the mutual conversion formula of the coordinates of the water filling system was derived. Then, a laser radar was used to scan the on-site environment, and a three-dimensional (3D) point cloud model of the sprinkler was constructed. The point cloud data was processed using the through filtering method and the density-based clustering algorithm, respectively. The region of interest (ROI) was delineated, and the feature information of the target was extracted. Finally, the least squares method in Matlab was used to perform the optimal circle fitting on the processed point cloud model, and a fitting circle model for the water filling nozzle was established to obtain the center coordinates of the circle and compare them with the measured results. The research results show that the circle center coordinates of the water filling nozzle of the sprinkler calculated by this method are similar to the measured data, with a location error of less than 2 cm, which is within the allowable range. This proves that it can be applied to the identification and location of the water filling nozzle of the sprinkler used in open-pit mines.

    Temperature detection algorithm of roller based on improved YOLOv7
    ZHANG Lei, JIRI Gele, SHANG Shuhong
    2023, 33(S2):  222-227.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0001
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    In order to ensure the steady operation of the coal transportation line and realize the intelligent monitoring and fault early warning of the roller, the intelligent inspection robot equipped with an infrared camera was used to perform fault inspection. The inspection robot adopted fixed-point shooting to collect infrared images in real time and used the target recognition algorithm to determine the characteristics of the roller and locate the roller. The inspection robot collected the temperature measurement information during roller operation, and the AI target detection algorithm was used to judge the abnormally high temperature of the roller bearing and detect abnormal roller temperature. Based on the detection results of the roller, the extracted temperature value, and the actual mileage value, an alarm signal was issued to the operator to achieve fault early warning. The detection of abnormal roller drew on the idea of the Transformer network and introduced recursive gated convolution (gnConv) to improve the YOLOv7 algorithm. The results show that the average precision of the improved YOLOv7 algorithm is up to 0.98 and meets the requirements of real-time processing. The accuracy of the improved YOLOv7 algorithm is increased by 3.1%; the recall rate is increased by 0.4%; the average precision is increased by 0.03%, and the improved YOLOv7 algorithm has a better detection effect.

    Dynamics model and characteristic analysis of drilling process
    YU Haicheng
    2023, 33(S2):  228-232.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0037
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    In view of the coupling vibration of key components in the drilling process of the downhole drilling rig, the downhole drilling rig was simplified into a multi-degree-of-freedom and multi-elastic system. The dynamic model of the drilling process of the downhole drilling rig was constructed based on the Lagrange equation. The displacement and vibration acceleration of the drilling rig during the drilling process were analyzed, and the rigid-flexible coupling dynamics of the drilling process were solved by the dynamic analysis software ADAMS. The post-processing program PostProcessor was used to perform the Fourier transform on the acceleration curve of the drill pipe under vertical and inclined conditions, so as to obtain the corresponding power spectral density distribution and analyze the dynamic response characteristics of the drill pipe under vertical and inclined conditions. The research shows that due to the influence of coal rock mutation and other factors, there is an instantaneous peak response of drill pipe acceleration in vertical drilling, but it does not affect the overall vibration law. The vibration acceleration of the inclined drilling process is stronger than that of the vertical drilling process, and the maximum vibration accelerations of the drill pipe in three directions are 4, 100, and 80 m/s2, respectively.

    Fault diagnosis algorithm for medium draining screen based on wavelet transform feature extraction
    SHANG Shuhong, CAO Liang, LU Wei
    2023, 33(S2):  233-237.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0020
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    The medium draining is considered a crucial link in the coal selection process. In order to mitigate faults triggered by prolonged operation of the medium draining screen under full load conditions, an algorithm based on wavelet transform and energy feature extraction was employed for monitoring and diagnosing the medium draining screen in real time. By employing methods such as adaptive threshold correction and improving the threshold function, the wavelet threshold denoising algorithm was optimized. The sound signals of the medium draining screen in normal and faulty operating states underwent wavelet decomposition. After threshold denoising, the energy features of the reconstructed signals were extracted. The low-frequency sub-band section was analyzed, and the energy ratio of primary frequency to secondary frequency under different states was calculated, enabling the diagnosis of faults in the medium draining screen. Results indicate that the algorithm of improved wavelet threshold denoising increases the correction accuracy by approximately 10%. The energy of the low-frequency sub-band part of the wavelet decomposed reconstructed signal is higher than that of other sub-bands, making its analysis representative. The energy ratio of primary frequency to secondary frequency of the low-frequency sub-band in faulty operating states is significantly higher than that in normal operating states, enabling the diagnosis of faults in the medium draining screen. Compared with traditional fault diagnosis methods, the diagnostic accuracy of the proposed method increases by about 5%.

    Technology and engineering of disaster prevention and mitigation
    Characteristics of hill fire hazards in transmission lines based on relay-patrol cooperative operation of UAVs
    LI Cong, XU Wenbo, JIN Yanke, WANG Chenhui, CHENG Haitao
    2023, 33(S2):  238-244.  doi:10.16265/j.cnki.issn1003-3033.2023.S2.0041
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    In order to reveal the characteristics of hill fire hazards in transmission lines in China's real environments, a technical scheme of UAV patrol based on relay-patrol cooperative operation was proposed. The transmission line patrol based on the relay-patrol operation of UAVs was carried out in many provinces and cities in China, and then the characteristics of hill fire hazards in transmission lines were analyzed. The results show that the hazards in transmission lines mainly include hill fire hazards, on-site construction hazards, and line hazards. The proportion of hill fire hazards is 77.2%, which is the most important factor affecting the safety of transmission lines. The causes of hill fire hazards can be divided into weed burning, straw burning, forest land/shelter forest burning, and paper burning for worshiping. Hill fire hazards have obvious spatial and temporal distribution characteristics. Hill fire hazards in April are mainly caused by paper burning for worshiping on the Qingming Festival, and 78.7% of the hill fire hazards occur in areas 50 m away from the transmission line. There are 122 hill fire hazards caused by a single fire source and 61 hill fire hazards induced by multiple fire sources. Among the hazards induced by multiple fire sources, those caused by double fire sources account for 45.9%, and 78.6% of the multiple fire source points are located in the spacing of 0-30 m. The fire source area of hill fire hazards is widely distributed. The maximum fire source area is 26.4 m2, and the minimum fire source area is only 0.12 m2. Overall, 84.4% of the fire source area is less than 4 m2.