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Table of Content

    28 February 2022, Volume 32 Issue 2
    Safety science theory and safety system science
    Mission and path of emergency management discipline construction from a perspective of knowledge production
    TAN Shuang, XU Mingxin, WANG Zewei
    2022, 32(2):  1-9.  doi:10.16265/j.cnki.issn1003-3033.2022.02.001
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    In order to clarify construction mechanism of emergency management discipline and promote sound development of the discipline, its construction difficulties and missions were analyzed by reviewing the development history, and corresponding construction path was put forward. The research shows that from the perspective of knowledge production mode transformation, the discipline's construction is faced with three dilemmas, including discrete knowledge producers, insufficient knowledge innovation and limited knowledge conversion, and has to complete three missions concerning emergency management knowledge, namely its direct reproduction aiming at talent cultivation, expanded reproduction for scientific research, and transformation reproduction oriented to social service. Moreover, the construction can be improved by strengthening top-level planning, optimizing training system of emergency management personnel, promoting collaborative innovation of related research, and improving its social service ability.

    Exploration of practical teaching in major of safety engineering under background of first-class undergraduate specialty construction
    TAN Zhaoyang, FANG Jing, XUE Wei, WU Changcheng, BAI Wenshuai
    2022, 32(2):  10-15.  doi:10.16265/j.cnki.issn1003-3033.2022.02.002
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    In order to explore a new practical teaching mode of safety engineering specialty under the background of first-class undergraduate specialty construction and to enhance innovative spirit and practical ability of the students, practical teaching data of this major in Hebei University of technology were analyzed. The problems it had in professional experiment, curriculum design and practice were pointed out and some reform measures were proposed and implemented, such as increasing proportion of comprehensive experiments, organizing curriculum design and planning, compiling teaching materials, adopting win-win mode between schools and enterprises to jointly build an internship base, and building a process control mode of "two practical operations and one visit". The results show that after reform of practical teaching, students' participation, enthusiasm and comprehensive innovation ability in various practical links have been significantly improved.

    Safety social science and safety management
    Bibliometric analysis of university teachers' occupational mental health based on CiteSpace
    ZHANG Hongying, SUN Ninghao, WANG Hui, TONG Ruipeng
    2022, 32(2):  16-21.  doi:10.16265/j.cnki.issn1003-3033.2022.02.003
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    In order to study main research content and direction in the field of university teachers' occupational mental health in recent 10 years, with CNKI as database, papers published from 2011 to 2020 were obtained after two searches, and statistical analysis on the number of papers was done. Then, CiteSpace was used for visualization processing to obtain keyword co-occurrence map. The results show that related researches on university teachers' occupational mental health mainly focus on job burnout and occupational stress. The hot topics are causes and countermeasures, and key objects are PE teachers, young teachers, English teachers and female teachers. Through analysis on research content, it is found that both occupational stress and job burnout exert negative effects on the teachers' occupational mental health. Effective intervention can be taken from society, school and individuals to improve it, and then enhance teachers' mental health.

    Research on and application of PDCS safety management mode
    LI Hao, HAO Junwei, LI Wenchang
    2022, 32(2):  22-27.  doi:10.16265/j.cnki.issn1003-3033.2022.02.004
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    In order to improve safety management level and hidden danger treatment ability of coal mines, firstly, a PDCS safety management mode was proposed, and then "8341 +" safety management system of Jizhong Energy Groups was established according to this theoretical mode. Secondly, big data and cloud computing technology were adopted to develop a cloud + edge information platform of safety management system, which realized information sharing and rapid processing as well as intelligent judgment and control. Finally, with practical application of Jizhong Energy Group as an example, effectiveness of the management model was verified and analyzed. The results show that PDCS mode can effectively quantify safety management in coal mines, timely reflect safety implementation, change, development trend and key issues, and provide digital support for decision making.

    Simulation of pedestrian flow at bottleneck of stairs considering group behavior
    CAO Shuchao, XI Xin, NI Jingyu, YAO Ming
    2022, 32(2):  28-33.  doi:10.16265/j.cnki.issn1003-3033.2022.02.005
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    In order to investigate impacts of group behavior on pedestrian flow efficiency at the bottleneck of stairs, a movement model considering group behavior was established by using Anylogic platform based on movement data of field observation experiments in campus. Then, numerical simulation was conducted to study influence of the group's movement parameters, the stairs' geometric parameters and layout of barriers on passing time and density distribution of pedestrian flow. The results show that a large proportion of groups and group size prolong the passage time and increase duration of congestion. Chain configuration features the greatest traffic efficiency while side by side configuration has the most negative impact on passage process. Moreover, opposite impacts on passing efficiency are exerted when stair position changes for the cases with or without groups. Parallel placement of barriers can effectively reduce crowd density and improve passing efficiency of groups.

    Review on affecting factors and intervention methods of drivers' hazard perception ability
    QIAO Jie, XU Xin, LIU Chuanpan, ZHAO Junwei, LIU Yongtao
    2022, 32(2):  34-41.  doi:10.16265/j.cnki.issn1003-3033.2022.02.006
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    In order to investigate effects of external intervention on drivers' hazard perception ability. Firstly, description of hazard perception process by different theories were sorted out and perception behavior mechanism was analyzed. Secondly, influence of affecting factors on hazard perception was analyzed, including driving style, driving experience, traffic environment and driving state. Then, research results of five different intervention methods with their features were introduced. Finally, limitations of existing researches were analyzed from the aspects of duration of intervention effect, evaluation index and transfer effect, and future development direction was discussed. The results show that it is significant to build a database of typical traffic hazard scenes in China and design a standard perception test system as well as formulate relevant regulations so as to improve Chinese drivers' general hazard perception ability.

    Analysis on passengers' agglomeration behavior at highway passenger stations considering group difference
    ZUO Wei, JI Xiaofeng, CHEN Fang, QIN Wenwen
    2022, 32(2):  42-50.  doi:10.16265/j.cnki.issn1003-3033.2022.02.007
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    In order to reduce potential safety hazards caused by passenger agglomeration at passenger stations during peak periods, based on full sample ticket purchasing data of highway passenger transport, a quantitative model of agglomeration behavior was established from three aspects, which were agglomeration probability, duration and intensity, and gathering characteristics of passenger flows at different levels of stations during weekdays, holidays and Spring Festival were obtained. Then, considering passengers' individual attributes and travel characteristics, agglomeration behavior characteristics of different groups were analyzed. Finally, a difference test was conducted to analyze influencing factors of such behavior, and countermeasures to reduce security risks were put forward. The results show that probability of passenger agglomeration in highway stations follows distribution of six polynomials, and its cumulative probability follows that of quadratic function, with highest probability of it occurring [10,20]min before departure. Regardless of travel distance, most travelers have a short waiting time, but in different periods, their flow concentration intensity and speed for different levels of passenger stations are significantly different. The spatial and temporal clustering characteristics of the first level stations are significant, while randomness of second level ones is stronger.

    A cross-level study on influence of team relationship conflict on safety performance of miners
    SANG Libin, LI Jizu
    2022, 32(2):  51-58.  doi:10.16265/j.cnki.issn1003-3033.2022.02.008
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    In order to effectively upgrade safety management efficiency of coal mining enterprises and improve safety performance of miners, based on conservation of resources theory, social cognitive theory, and self-determination theory, cross-level influence mechanism of TRC on miners' safety performance was explored with team efficacy from the perspective of a team and safety motivation from that of individuals as mediating variables. Questionnaire surveys and empirical studies were conducted on 347 miners from 40 teams. The results show that TRC can not only negatively influence safety performance of miners in a direct way, but also indirectly influence it through independent mediating effect and chain mediating effect of team efficacy and safety motivation of miners. Among them, autonomous safety motivation plays a key role in its influence path.

    Safety engineering technology
    Determination and kinetics analysis of coal ignition point based on thermal explosion method
    CHEN Xiaokun, WANG Chenxi, ZHAI Xiaowei
    2022, 32(2):  59-65.  doi:10.16265/j.cnki.issn1003-3033.2022.02.009
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    In order to accurately decide ignition point of coal and improve prevention and control ability of spontaneous combustion disasters, according to TET and with consideration to heat release curve of spontaneous combustion process, the first minimum point on differential heat flow curve in the process was taken as ignition point, and dynamic parameters during heat release before and after ignition were calculated. The results show that along with increase in heating rate, exothermic process of coal spontaneous combustion gradually moves to high temperature regions, and ignition point also increases gradually, while activation energy of reaction decreases in the same manner. At the same heating rate, activation energy of coal increases after ignition, with the level of coal oxygen reaction being decreased to 1 after ignition point from 1.5 before it. It is also found that oxygen combustion of coal after ignition is more sufficient, and spontaneous combustion is more difficult to control.

    Experimental study on soil surface CO2 fluxes in goaf area of Haizhou open-pit mines
    ZHANG Xiaoming, LIU Xiaoying, DONG Wei, ZHANG Hemeng, WANG Yongjun, SASAKI Kyuro
    2022, 32(2):  66-73.  doi:10.16265/j.cnki.issn1003-3033.2022.02.010
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    In order to study status of spontaneous combustion in Dongbang abandoned goaf in Haizhou open-pit mine, based on characteristics of spontaneous combustion and gas diffusion theory of residual coal in goaf, Intelligent Soil Gas Flux Monitoring System was used to continuously (monthly) monitor soil surface CO2 fluxes at measuring points in Dongbang goaf. According to distribution characteristics of surface CO2 fluxes and soil temperature in the experimental region, emission range and variation of CO2 released from underground fire area were explored. At the same time, CO2 emission in the area was calculated and its variation with time was analyzed. The results show that soil surface CO2 fluxes are positively correlated with soil temperature. The area of high CO2 fluxes in the experimental region shows a trend of monthly expansion and increase. Moreover, CO2 emission gradually increases every month, and the annual emission in the experimental region is about 3.6×106 m3.

    Evaluation on sealing performance of mudstone caprocks of gas reservoir-type gas storage in high temperature environment
    LUO Zhengshan, DUAN Yuanzhe, WANG Xiaowan, ZHANG Xinsheng
    2022, 32(2):  74-82.  doi:10.16265/j.cnki.issn1003-3033.2022.02.011
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    In order to explore influence of high temperature on sealing performance of mudstone caprocks, three forms of thermal stress generated by gas storage caprocks were theoretically analyzed. Then, based on laboratory tests, mechanical damage degree of mudstone and changes of caprock sealing assessment indicators in high temperature environment were analyzed. The results show that the overall structural performance of mudstone is reduced under high temperature, with 400 ℃ being generally the threshold temperature for its damage under action of periodic thermal stress. High temperature will significantly change the physical sealing characteristics of mudstone caprocks, and when it is around 400 ℃, which is the threshold, sealing ability will be lost. According to empirical research and analysis results of caprocks in a gas reservoir type gas storage, temperature range of target caprock has not exceeded the threshold. It is believed that the mudstone caprock has good sealing performance, and evaluation result can reflect the true situation of mudstone capping.

    Analysis on thermal characteristics of naturally aging wood during combustion
    DENG Jun, SONG Jiajia, ZHAO Jingyu, LIU Tongshuang, LU Shiping, ZHAO Yanli
    2022, 32(2):  83-89.  doi:10.16265/j.cnki.issn1003-3033.2022.02.012
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    In order to provide the basic theory for numerical simulation and risk assessment of historic building fire, with naturally aging wood as research object, their appearance and thermal conduction characteristics and those of reference wood were analyzed by scanning electron microscopy (SEM) and thermal property test from the perspective of natural aging. Then, their thermal release features at different stages during combustion were studied by using differential scanning calorimetry (DSC), and effects of different heating rates on thermal behavior of aging wood were analyzed. Finally, their apparent activation energy distribution during thermal reaction was calculated and analyzed based on heat flow. The results show that the thermal diffusion ability of naturally aging wood is enhanced. Natural aging reduces the energy required in the ignition and combustion process of wood, and has a great influence on energy demand before ignition, thus greatly reducing peak energy barrier needed during ignition.

    Evaluation and engineering application of an improved finite cloud model for rockburst proneness
    HU Jianhua, HUANG Pengli, ZHOU Tan, WEN Guanping, YANG Dongjie
    2022, 32(2):  90-98.  doi:10.16265/j.cnki.issn1003-3033.2022.02.013
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    In order to evaluate rockburst in deep mining, with Tiaoshui river Phosphorite Mine being taken as an example, a comprehensive evaluation system of 3 rockburst proneness indexes e0/ece1/ecec/et were put forward, and comprehensive weight method which was able to eliminate cloud atomization was adopted to develop an improved finite cloud evaluation model for roof multi-index rockburst proneness. Then, stress value of the stope was calculated by FLAC3D, and parameter values of e0/ece1/ecec/et were obtained. Finally, evaluation experiment on Tiaoshui river Phosphate Mine was carried out, and rockburst proneness of its top slab was determined according to the principle of maximum membership. The results show that the roof of its deep stope has a weak rockburst proneness, which is consistent with actual situation. Compared with the results of other methods, this model features good accuracy. Moreover, control measures, like identification, supporting and monitoring of rockburst hazard areas, are proposed.

    Prediction of external corrosion rate of offshore oil and gas pipelines based on FA-BAS-ELM
    ZHANG Xinsheng, CHANG Yingge
    2022, 32(2):  99-106.  doi:10.16265/j.cnki.issn1003-3033.2022.02.014
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    In order to improve prediction accuracy and efficiency of external corrosion rate of submarine oil and gas pipelines, a ELM prediction model based on FA and BAS was established. FA method was used to reduce dimension of influencing factors' data set and determine input variables of ELM network. Then, an ELM prediction model was established, and its parameters were optimized by BAS to avoid influence of randomness of parameter values on its predictive performance. Finally, with the real sea hanging film experiment as an example, predictive performance of the model was evaluated through modeling and simulation, and it was compared with other models. The results show that the mean absolute percentage error (MAPE) of FA-BAS-ELM prediction model is only 1.92, and its determination coefficient R2 reaches as high as 0.994 9, indicating that the model has better prediction accuracy and performance.

    Pressure compensation algorithm of fire gas sensors based on IPSO-BP model
    HE Yongbo, CAO Zhubing
    2022, 32(2):  107-114.  doi:10.16265/j.cnki.issn1003-3033.2022.02.015
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    In order to improve fire detection system of aircraft, volume fraction values of CO and CO2 gas sensors under different air pressure were simulated and compared with the theoretical value by designing a set of experimental scheme, and a particle swarm optimization algorithm was proposed to dynamically adjust learning factor according to particle fitness value. Then, IPSO algorithm was used to find optimal initial weight and threshold of BP neural network which, after optimization, was employed to modify detection results of CO and CO2 gas sensors to eliminate influence of air pressure on sensor data acquisition. The results show that after compensation by IPSO-BP algorithm, gas volume fraction values at the selected 27 pressure points are close to the fitted true value. Among them, the maximum measurement error of CO2 gas sensor drops from 542×10-4% to 0.1×10-4% after pressure compensation, and that of CO gas sensor decreases from 15.7×10-4% to 0.01×10-4%. Compared with BP neural network pressure compensation model, the accuracy of IPSO-BP neural network model is significantly improved.

    Research on optimization of disaster triplet information extraction based on BERT
    SONG Dunjiang, YANG Lin, ZHONG Shaobo
    2022, 32(2):  115-120.  doi:10.16265/j.cnki.issn1003-3033.2022.02.016
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    In order to quickly and precisely extract triplet information from text on online social media, NLP technology was utilized to study the application and algorithm optimization of the information extraction. Then, BERT pre-trained language model was applied in a case of triplet information extraction of geological disasters. Considering the model's problems of "low-rank bottlenecks" caused by its own MHA mechanism, the key-size was increased to optimize the model. The results show that the proposed method can significantly improve fault tolerance and accuracy of disaster information extraction, including disaster type, occurrence location, occurrence time, from news reports. And it can be used to analyze spatial distribution and trend of disasters, and then provide scientific analysis and decision-making support for disaster emergency management, such as preparation of emergency plan, optimal allocation of emergency resources, regional monitoring and early warning, etc.

    Study on fire-thermal-structural coupling of ship engine rooms considering fire location
    WANG Jinhui, CAI Wei, ZHANG Xianda, CHENG Yanquan, BA Guangzhong
    2022, 32(2):  121-129.  doi:10.16265/j.cnki.issn1003-3033.2022.02.017
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    In order to accurately analyze mechanical behavior of ship engine room structures under real fire conditions and address insufficiency of traditional standard fire temperature-time curve technique, a coupling analysis method of fire, heat and structural mechanics by combing FDS with ANSYS was proposed. FDS was employed to simulate real fire, and time-varying temperature field information near inner walls of ship engine rooms was obtained, which was used as the inputting variable and transmitted to structural mechanical behavior simulator ANSYS. Then, temperature load of cabin structure was loaded and transient thermal analysis was carried out, thermal mechanical coupling calculation was performed. Finally, by changing fire source position, mechanical response characteristics of cabin structures under different fire source positions were investigated. The results show that stress distribution of the structures is uneven under different fire location scenarios, and the maximum temperature stress is 76 MPa when fire height is 2 m. Fire safety design should focus on cases of non-uniform heating of structures in real fire.

    Experimental study on sieving phenomenon and particle size distribution characteristics of coal particles
    LIU Qingquan, LIU Yuanyuan, DU Kai, ZHENG Siwen, ZHU Zibin
    2022, 32(2):  130-138.  doi:10.16265/j.cnki.issn1003-3033.2022.02.018
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    In order to investigate influence of mean particle sizes on the calculation of coal's physical property parameters, screening phenomenon and particle size distribution of coal particles at five fractions were studied. Then, with solution of coal gas diffusion coefficient as an example, effects of arithmetic mean and volume-weighted mean volume particle size on calculation results were analyzed. The results show that special separation phenomenon occurs during screening process of coal particles, and distribution of target fractions only accounts for 33.37%—49.32% of real size distribution. And arithmetic mean makes all sieved particle sizes within the target fraction, which causes a large error in calculating the diffusion coefficient. Compared it with the volume-weighted average volume size which considers characteristics of particle size distribution, the difference of diffusion coefficient between the two solutions is up to 43.42%.

    Preparation technology of HMX-based insensitive booster explosives
    GUO Haijun, WU Yuchen, TANG Hanlu, WANG Kai, WANG Liang, XU Chao
    2022, 32(2):  139-144.  doi:10.16265/j.cnki.issn1003-3033.2022.02.019
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    In order to obtain insensitive booster explosives with better performance, based on HMX raw materials, fine-grained HMX was prepared by using solvent-non-solvent recrystallization technology and ultrasonic spray technology. Meanwhile, coated HMX with acrylate rubber (ACM), F2602 and Viton A as binders was prepared by using the experiment method, and its safety was tested and analyzed. The results indicate that after refinement, the thermal stability and thermal sensitivity of HMX are reduced, while its impact stability are greatly improved. When coated HMX is prepared, its apparent activation energy and pre-exponential factors are greater than that of refined samples under the condition of the same ratio of binder and raw material, and moreover, HMX coated with ACM will result in better thermal stability. According to the critical temperature of thermal explosion, it can be concluded that explosives coated with ACM at the ratio of 95∶5 has the best performance, and impact sensitivity test also shows that ACM has the most obvious desensitization effect.

    Research on thermal runaway characteristics of lithium-ion batteries along with cell number changes under standard and low atmospheric pressures
    SUN Qiang, JIA Jingyun, WANG Haibin, LI Dan, HE Yuanhua, CHEN Xiantao
    2022, 32(2):  145-151.  doi:10.16265/j.cnki.issn1003-3033.2022.02.020
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    In order to reveal the variation of thermal runaway fire risk characteristics of lithium-ion batteries for different cell numbers under ambient pressure of land surface and cruise altitude, thermal runaway experiments with different cell numbers were carried out at pressure of 95 kPa and 20 kPa. Heat release rate, total heat release, smoke temperature and concentrations of CO, CO2 and hydrocarbons were measured. The results show that the peak heat release rate and total heat release grow with cell number in a power function and the index reduces along with the decease of pressure. As the increases of cell number, combustion explosion and jet flame become frequent and thermal hazards increase greatly, but peak concentrations of flammable gases are comparatively lower with no significant growth under pressure of 95 kPa. However, the hazards of potentially explosive gases increase greatly under 20 kPa, such as CO and hydrocarbons.

    Safety analysis on HWP in aerial refueling based on STPA
    LYU Xufei, YAO Shanghong, QUAN Jiale
    2022, 32(2):  152-157.  doi:10.16265/j.cnki.issn1003-3033.2022.02.021
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    In order to quantitatively evaluate safety of HWP in aerial refueling, a total of 46 items which included relevant system-level hazards, unsafe control behaviors and causative factors were found by using STPA method, and 44 corresponding safety constraints were determined. Then, quantifiable safety checkpoints were defined based on air refueling flight data, safety constraints were divided into 17 categories, and safety intervals and weight of each checkpoint were determined. Finally, quantification interval of HWP was decided according to flight data, and together with its weight, was used to score safety of instances of heavy whip, moderate whip, and safe docking. The results show that using STPA method to identify and quantify safety risks could characterize safety level of aerial refueling docking, and it exhibits lowest safety level under heavy whip of the hoses.

    Study on failure mechanism of withdrawal channel's surrounding rock during last mining period
    HE Yanjun, SONG Yaxin, SHI Zhanshan, LI Junqi, CHEN Kai, LI Zhiping
    2022, 32(2):  158-166.  doi:10.16265/j.cnki.issn1003-3033.2022.02.022
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    In order to make the working face withdrawal safe and efficient, the stress distribution and failure characteristics of withdrawal channel's surrounding rock in fully-mechanized area during last mining period were studies through theoretical analysis and field observation. Then, failure mechanism and method for roof surrounding rock control by supporting force of cog timbering were proposed, and calculation method of minimum initial support force of cog timbering was obtained. The results show that concentrated stress of the withdrawal channel's surrounding rock is gradually superimposed with the bearing pressure in front of working face, which leads to the gradual failure of remaining coal pillar from both sides to the middle. When the failure areas on both sides are connected, the direct top span above coal pillar is increased by 2 times, and the load is large. When the stress and span meet the instability conditions of direct roof, the latter is damaged before working face is cut through, thus leading to roof fall before penetration. Adjusting the initial support force of cog timbering can reduce superimposed stress value of coal pillar at the side of withdrawal channel, corresponding coal pillar width when remaining coal pillar loses stability and the span of direct roof, thus avoiding shear failure and ensuring smooth withdrawal.

    Public safety
    Resilience of urban public health system in cases of epidemic crisis
    ZHUANG Yue, LIANG Xiaoxiao
    2022, 32(2):  167-175.  doi:10.16265/j.cnki.issn1003-3033.2022.02.023
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    To effectively cope with urban public health crisis, the resilience of public health system is critical. With the successful prevention experience of COVID-19 epidemic in Wuhan as an example, grounded theoretical method was used to analyze concepts and behaviors of the government, communities, hospitals, media and Non-Governmental Organizations in the prevention and control of the epidemic. 10 main categories and 52 corresponding sub-categories, which reflected system resilience, were identified, including disease surveillance system, epidemic prevention resource management, and collaborative governance capabilities. It is found that public health system resilience can be divided into functional resilience, process resilience and integral resilience. A hierarchical structure model can be constructed to improve its resilience by means of interpretation structure modeling (ISM). And by integrating factors of multiple social subjects, including social epidemic prevention foundation, epidemic prevention technology and culture, and comprehensive governance of epidemic risks for gradual emergency preparedness, the resilience of the urban public health system can be upgraded.

    Normal traffic risk assessment of second-class highways in mountainous areas during operation period
    CHEN Shengdi, GE Xiaowan, ZHAO Xiaochen, LU Jian, XING Yingying
    2022, 32(2):  176-183.  doi:10.16265/j.cnki.issn1003-3033.2022.02.024
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    In order to objectively and accurately evaluate normal traffic risks of second-class highways in mountainous areas, the risk resources were divided into two types, namely dynamic risk and static risk sources. Firstly, to assess static risks, an accident consequence model was established by comprehensive evaluation method based on whitening weight function, while an accident probability model was developed based on historical accident data. Then, for dynamic risk assessment, an accident consequence model was built by combining whitening weight function and analytic hierarchy process (AHP), and an accident probability model was built by using ordered Logit model. Finally, the normal traffic risk of second-class highways in mountainous areas was evaluated by integrating dynamic risk and static risk. The results show that the assessment model can evaluate normal traffic risks of these highways during operation period by combining dynamic and static data such as road alignment, traffic environment and natural environment. Based on this, highly risk sections can be identified, and thus responding countermeasures can be put in place to improve traffic safety level.

    Identification and analysis of serious conflicts in expressway transition areas
    QIU Ji, WANG Hong, JIANG Ruoxi, XIAO Wenbin, CHANG Hongguang, ZHU Shunying
    2022, 32(2):  184-191.  doi:10.16265/j.cnki.issn1003-3033.2022.02.025
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    In order to further explore causes of serious conflicts in transition areas of expressway reconstruction and expansion, a high-precision radar was used to collect real-time status data of vehicles, and k-means clustering was carried out on initial velocity and acceleration of a single vehicle. Then, based on conflict rate and road accident rate in cluster combination, Pearson coefficient method was adopted to determine serious conflicts threshold, and a binomial Logistic model was established integrating factors of vehicles, traffic flow and roads in transition areas to analyze influence degree of serious conflict factors. The results show that there are serious conflicts when velocity ranges from 45.50 to 85.68 km/h, and acceleration ranges from -3.53 to -1.31 m/s2 or velocity ranges from 27.65 and 34.96 km/h, and acceleration from 1.77 and 3.04 m/s2. The vehicle type, traffic volume, average speed, acceleration and driving angle per unit length have significant influence on probability of conflicts, and by diverting large vehicles through traffic organization, increasing radius of circle curves in transition areas and setting reasonable speed limit signs, the probability can be effectively reduced.

    Risk assessment of regional violent terrorist attacks in southern Xinjiang
    HUANG Jie, ZHANG Xianfeng
    2022, 32(2):  192-199.  doi:10.16265/j.cnki.issn1003-3033.2022.02.026
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    In order to examine high-risk areas of violent terrorist attacks and promote refined public security management, with southern Xinjiang, China as an example, gridded socio-economic data, remote sensing data, POI data, and other multi-source geospatial data were used to build a risk assessment indicator system of violent terrorist attacks from three aspects, namely occurrence probability of terrorists, preference of their target, and potential consequences of the attacks. Then, weights of geospatial indicators were determined according to AHP-Entropy method and cluster analysis method, and spatial distribution of attack risks on 30″ × 30″ (approximately 1 km×1 km) fine-granulated grids in southern Xinjiang was obtained. The results show that the high-risk grids of violent terrorist attacks in the area are mainly located in some cities and towns in Kashgar, Hotan and Aksu, which are consistent with distribution of historical attack events, therefore indicating the rationality and feasibility of proposed evaluation indicator model.

    Occupational health
    Pneumoconiosis risk assessment method based on cumulative dust exposure
    ZHANG Ge
    2022, 32(2):  200-206.  doi:10.16265/j.cnki.issn1003-3033.2022.02.027
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    In order to reduce the risk of pneumoconiosis for workers with different dust exposure experiences, a risk assessment method was proposed. Firstly, dust types were identified, and dust exposure in workplace and cumulative dust exposure of workers were evaluated, and dose-response relationship between dust and pneumoconiosis risk were determined. Then, current pneumoconiosis risk, risk after a period of continued exposure to dust, increase of such risk, and its growth rate were assessed by using current values and increment values of cumulative prevalence as risk assessment indexes. Finally, with 15 coal miners as examples, pneumoconiosis risk assessment was carried out by utilizing the assessment method. The results show that the proposed method is intuitive and effective. And pneumoconiosis risk monotonously increases along with the cumulative dust exposure. The smaller the exposure is, the more obvious effect of dust prevention intervention measures will have in reducing relative risk.