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Table of Content

    28 March 2024, Volume 34 Issue 3
    Safety social science and safety management
    Research on early warning for prefabricated building workers' unsafe behaviors of working at height based on RF-SFLA-SVM
    WANG Junwu, HE Juanjuan, SONG Yinghui, LIU Yipeng, CHEN Zhao, GUO Jingyi
    2024, 34(3):  1-8.  doi:10.16265/j.cnki.issn1003-3033.2024.03.1288
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    In order to effectively provide early warning of the occurrence trend or state of prefabricated building workers' unsafe behaviors (PBWUBs) of working at height, and to enhance the control of PBWUBs, RF-SFLA-SVM model was proposed to conduct an early warning study on workers' unsafe behaviors. Firstly, the SHEL (Software-Hardware-Environment-Liveware) model was used to analyze the factors influencing the unsafe behaviors of prefabricated building workers in danger of working at height. RF was used to determine the key warning indicators. Then SFLA was used to find the best parameters for SVM. Finally, the RF-SFLA-SVM model was used to predict and warn about the unsafe behavioral state of the prefabricated building workers working at height, and its performance was compared with other warning models. The results show that the RF-SFLA-SVM-based warning accuracy of PBWUBs of working at height was the highest, 91.67%, which was a maximum improvement of 14% compared with the warning performance of other models. The research results can give a reference for the control and prevention of PBWUBs working at height.

    Research on configurational causes of employee work safety violations: from a complexity theoretical perspective
    LIU Lin, WU Jinnan, MEI Qiang
    2024, 34(3):  9-19.  doi:10.16265/j.cnki.issn1003-3033.2024.03.0451
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    In order to reveal the complex causality between EWSV and their multiple antecedent conditions, and to improve the efficiency of safety governance, a comprehensive model integrating contemporary deterrence theory, protection motivation theory, and social learning theory was constructed from a perspective of complexity theory. Based on this, six antecedent conditions affecting EWSV were identified from three perspectives: leader, coworker, and employee. Then, the fsQCA was used to reveal what configuration of antecedent conditions would lead to high level of EWSV. The results show that a single antecedent condition is insufficient to explain high level of EWSV but safety-specific leader punishment omission and coworker work safety violations(CWSV) play universal roles in forming high level of EWSV. Three types of driving modes composed of five condition configurations can lead to high level of EWSV. Three types of condition configurations lead to non-high level of EWSV. Reducing CWSV and improving employees' perception for formal sanctions are crucial for achieving non-high level of EWSV. Different combinations of multiple antecedent conditions can lead to high level of EWSV, and there is a complex causality (concurrency, equivalence, and asymmetry) between high level of EWSV and their antecedent conditions.

    Identification of critical factors in chemical accidents based on text mining and improved DEMATEL method
    WANG Liang, LAI Jiayan, ZHANG Zixin, WANG Yingming
    2024, 34(3):  20-28.  doi:10.16265/j.cnki.issn1003-3033.2024.03.0230
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    To draw lessons from historical chemical accidents and guide the practice of chemical safety production management, a method for identifying critical factors in chemical accidents based on text mining and improved DEMATEL method was proposed. Firstly, text mining technology was used to fully mine the text information of 1 627 chemical accident investigation reports, based on which 14 chemical accident influencing factors were extracted according to related literature, laws and regulations. Then, the fuzzy DEMATEL method based on alpha-level sets was used to calculate the performance levels of the factors affecting chemical accidents. Finally, the correlations between critical factors and other factors were analyzed and the mechanism of chemical accidents was revealed. The results show that 8 chemical accident influencing factors are identified as the critical factors, i.e., extreme weather, regulations, technical procedures, hidden danger investigation, risk control, education and training, supervision and management, and operation management. These 8 critical factors have direct impact on the influence factors such as facilities and equipment, material reactions, occupational quality, job responsibilities, emergency management, and safety investment, which eventually lead to chemical accidents.

    Feature mining and causative analysis of fire accidents in ship repair and building enterprises
    LI Xian, JIAO Yu, CHEN Wentao, SHI Danda, KANG Yutao
    2024, 34(3):  29-38.  doi:10.16265/j.cnki.issn1003-3033.2024.03.0368
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    To investigate the features and causation factors of fire accidents in SRBE, 118 fire accidents were studied using method of mathematical statistics. Firstly, accident features were mined in terms of the temporal and spatial attributes of accidents, the three elements of fire and the severity of injuries. Then, based on the improved HFACS-SRBE accident causation model, methods such as Chi-square test, OR and Cramer's V were used to analyze the correlations and their strength between the causal factors. The results show that 14:00-16:00 is the most prone to fire accidents and casualties. The main location of fire accidents is in the ship area, accounting for 33.90%. 59.19% of the ignition source comes from the ignition operation. Ratio of no injuries, slight and minor injuries, serious injuries and deaths is 61:54:3. Through the test of correlations and their strength, it is determined that 15 groups of adjacent level causal factors are correlated, and 26 complete accident causation chains are obtained. Covers communication and coordination→inappropriate operation plans→bad psychological state→decision-making errors is the accident causation chain with the greatest strength of correlation leading to the occurrence of fire accidents in ship repair and building enterprises.

    Safety engineering technology
    Analysis of thermal runaway explosion overpressure and liquid nitrogen inerting effect of lithium battery
    ZHANG Shaoyu, WANG Yue, DONG Haibin, CHEN Ye
    2024, 34(3):  39-44.  doi:10.16265/j.cnki.issn1003-3033.2024.03.0878
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    In order to clarify inerting effect of liquid nitrogen on the thermal runaway explosion of a 280Ah energy storage lithium battery, based on experiment analysis of composition and explosion limit of battery thermal runaway gas, FLACS was used to simulate explosion overpressure of battery thermal runaway gas in a storage container. Standard experiments and real experiments were carried out to analyze inerting effect of liquid nitrogen on battery thermal runaway gas. Results show that thermal runaway gas explosion overpressure increases gradually with an increase of its volume. Ignition of more than 1.1 m3 of thermal runaway gas can cause serious consequences. A single 280 Ah lithium iron phosphate battery in 100% charged state, heating in a vacuum state,heating in a vacuum state can trigger thermal runaway of the battery and produce 134.6 L of thermal runaway gas with CO2, H2, CO, CH4 and C2H4 as the main components. Thermal runaway gas is a flammable gas, and explosion limit range is between 8.5% and 45.5%. N2 can effectively inert thermal runaway gas and significantly reduce the explosion limit range of thermal runaway gas. Limiting N2 volume fraction is 84.7%. Spray 69 kg liquid nitrogen into a 35 m3 energy storage container to inert battery thermal runaway gas. When volume fraction of N2 is higher than limiting nitrogen volume fraction, battery thermal runaway gas can be effectively inerted, and effective protection time is 2 200 s.

    Operational safety resilience measure for public transportation equipment and facility systems based on CN-FRAM
    SHEN Ling, TANG Lingyi, LIAO Jie
    2024, 34(3):  45-54.  doi:10.16265/j.cnki.issn1003-3033.2024.03.0658
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    Equipment and facility failures were the primary cause of safety accidents in public transportation systems. In order to better quantify and enhance the safety resilience of systems, CN-FRAM operational safety resilience measurement model, integrating CN and FRAM, were proposed. System resilience was defined as the ratio of system performance loss to performance baseline under perturbations. Firstly, based on the composition and functional nodes of the equipment and facility system, a CN was established. Secondly, the FRAM model was embedded into the CN to expand nodes and connections, constructing the CN-FRAM model. Then, based on the CN-FRAM resilience measurement model, the aggregation of functional changes between system components was analyzed, and when quantifying system resilience, the overall efficiency of the network and the degree of coupling between components were considered comprehensively. Finally, using the metro signal system in Nanjing as an example, the feasibility and effectiveness of the method were validated. The results show that the model can quantify the resilience of the system throughout the disruption-recovery process, calculate the impact of failures on the system, and maximize resilience values as the objective, demonstrating resilience performance under different repair strategies, thereby providing a basis for determining the optimal recovery sequence. Compared with existing methods, the optimal recovery strategies identified by this method can significantly reduce the overall performance loss caused by failures, thus enhancing system resilience.

    Study on evolution process of deflagration wave system of premixed gas in long straight pipeline
    HU Yang, TAO Hong, SONG Minhang, LYU Shuo, ZHANG Haixia
    2024, 34(3):  55-62.  doi:10.16265/j.cnki.issn1003-3033.2024.03.1326
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    In order to reduce gas explosion accidents during the production, transportation and storage of combustible gases in industrial sites, square pipes of 200 mm×200 mm×35 m and round pipes of 90 mm diameter and 10 m length were independently constructed. Under the same initial conditions, the explosion test of methane/air premixed gas with volume fraction of 9.5% was carried out, and it was studied with pressure and flame sensors. The results show that the evolution process of the wave system in two kinds of pipes with different scales and cross sections is the same. After ignition, the flame changes from layer to turbulent flow, and the acceleration of flame leads to the compression wave chasing each other, finally forming a strong shock wave. The changing trend of flame speed in the two long straight pipes is the same, and they both experience the process of acceleration-deceleration-re-acceleration-re-deceleration, with the maximum flame speed in the square tube and round tube reaching 69 and 35.7 m/s respectively. After the first compression wave reflects off the wall, the pressure rises to 117% and 114%. When the reflected wave is coupled with the flame front, the flame speed in the large-scale pipeline is reduced to 73%, and that in the small pipeline is reduced to 93%. Under the same volume fraction, the maximum overpressure values of the first compression wave in the two long straight spaces are similar, which are about 65.45 and 67.09 kPa.

    Numerical simulation of leakage and diffusion in buried hydrogen-blended natural gas pipeline
    PENG Shanbi, LUO Xue
    2024, 34(3):  63-69.  doi:10.16265/j.cnki.issn1003-3033.2024.03.1904
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    In order to reduce the safety problems caused by leakage of hydrogen-blended natural gas during the distribution, based on fluid mechanics and porous media theory, a three-dimensional numerical model of leakage and diffusion of urban buried hydrogen-blended natural gas pipeline was established by Fluent software. The effects of hydrogen blending ratio, leakage aperture, pipeline pressure, pipeline buried depth and soil type on the leakage of hydrogen-blended natural gas and the vertical diffusion distance of the lower explosion limit of methane and hydrogen were analyzed. The results show that the larger the proportion of hydrogen blending, the smaller the leakage of hydrogen-blended natural gas, and the longer the time it takes for the methane explosion lower limit contour to diffuse to the surface, while the opposite is true for hydrogen. Secondly, the leakage amount is about twice as much as 5 mm when the leakage aperture is 10 mm. The leakage amount is about twice as much as 10 mm when the leakage aperture is 20 mm. The larger the leakage aperture, the shorter the time required for the lower explosion limit of methane and hydrogen to reach the surface. Thirdly, the greater the pipeline pressure, the greater the leakage of hydrogen-blended natural gas and the faster the diffusion speed, and the higher the risk coefficient. Besides, when the buried depth of the pipeline is 1.1m, the leakage is largest, followed by 1.4 m and 0.8 m. The shallower the buried depth, the shorter the time required for the lower explosion limit of methane and hydrogen to reach the surface. Finally, the soil type has an important influence on the leakage and diffusion of hydrogen-blended natural gas. When the soil type is silty sand, the leakage and diffusion rate of hydrogen-blended natural gas are the largest, followed by loam and finally clay.

    Modular system design of new track fire rescue vehicle
    MA Qinglu, DING Xueqin, HUANG Xiaoxiao, LI Jun
    2024, 34(3):  70-75.  doi:10.16265/j.cnki.issn1003-3033.2024.03.1209
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    In order to realize the effective rescue of various complex rail transit accidents, the present situation and development trend of the existing rail fire rescue systems at home and abroad were analyzed through a literature search first. Then, the applicability of road and rail dual-purpose vehicles in mountain urban rail transit systems and the feasibility of modular transformation were summarized and analyzed. Finally, a new fire and rescue rail transit system was proposed, which was suitable for mountain urban rail characteristics. The results show that the designed road and rail dual-purpose fire rescue vehicle meets the requirements of track fire rescue. The system is adopted with a high-intensity modular and prefabricated design concept. It is equipped with a fire extinguishing and smoke exhaust system for controlling various fire conditions, a traction winch, emergency power generation, medical supplies, and other emergency rescue equipment, which can deal with the rescue work of track accidents in a closed and heavy smoke environment. The loss caused by accidents is significantly reduced.

    Instability analysis and safe thickness calculation of waterproof rock mass based on mutation theory
    FANG Lin, GONG Sheng, WANG Guilin, YU Hao
    2024, 34(3):  76-83.  doi:10.16265/j.cnki.issn1003-3033.2024.03.0344
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    In order to ensure the safety of the construction and operation of the karst water inrush tunnel, based on the elastic beam model, double cusp mutation model of the instability of the karst water inrush roof under dynamic disturbance was established by using the catastrophe theory. Considering the surrounding rock properties, hydrostatic pressure, dynamic disturbance and other factors, the instability mechanism and failure conditions of the roof of karst water inrush tunnel were analyzed, the discriminant equation of its instability mutation was established, and the minimum safe thickness of the roof was solved by Matlab software programming. At the same time, in order to avoid the irrationality of the theoretical formula of the mutation when the hydrostatic pressure was too large, the minimum safe thickness of the hydrostatic pressure was calculated separately, and the greater value of two calculated values was taken. The results show that whether the waterproof rock mass remains stable is determined by the factors the internal and external factors of rock mass. The minimum safe thickness of the rock mass increases with the increase of the span of the rock mass, and decreases with the increase of the elastic modulus of the rock mass. When the vibration frequency is constant, the greater the blasting load, the greater the minimum safe thickness of rock mass. When the blasting load is constant, the greater the frequency of blasting vibration, the smaller the minimum safe thickness of rock mass. The greater the hydrostatic pressure, the greater the minimum safe thickness of rock mass. The engineering example shows that this method of calculating the safety thickness of the roof of karst tunnel is feasible and highly accurate.

    Causes and correlation network analysis of civil aviation accidents for whole flight phases
    LIU Dan, LUO Yansheng, LI Shixuan, XU Gangyan, LI Moxiao
    2024, 34(3):  84-92.  doi:10.16265/j.cnki.issn1003-3033.2024.03.0679
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    In order to improve the safety level of China Civil Aviation, a cause analysis method, which focused on the whole process of 'taxiing-takeoff-climbing-cruising-falling-approaching and landing', was proposed based on association rules and SNA. Firstly, a total of 1 051 civil aviation accident cases from 2010 to 2022 were collected from Aviation Safety Information System. Then, a civil aviation accident causation index system based on 'human-machine-environment-management' was established in combination with 'control navigation service procedure-training'. Secondly, the EasyData data service platform was used for annotation, followed by constructing the data-set of the cause of civil aviation accidents facing the whole process of flight. Furthermore, the FP-Growth algorithm was employed to mine the association rules with the flight phase as the subsequent term of rules. Finally, this study emphasized the co-occurrence frequency of association rules, and developed the correlation network of civil aviation accident causes by applying the centrality analysis of flight phase and accident causes. The results show that the most dangerous phases of flight are the approach and landing. Operation failures, runway safe accidents and cabin safe accidents are the main types. Among the 10 identified causes of civil aviation accidents, there are 4 human factors, 2 facilities and equipment factors, 3 environmental factors and 1 management factor.

    Representation and reuse of ontology knowledge for safe operation of cable crane
    CHEN Shu, LU Shili, WANG Jianping, LI Zhi, ZHANG Guangfei
    2024, 34(3):  93-100.  doi:10.16265/j.cnki.issn1003-3033.2024.03.1321
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    In order to solve the problem that a large amount of multi-source heterogeneous structured and unstructured knowledge in the operation and management of cable crane is difficult to reuse, a large number of technical specifications, expert experience and other safety knowledge accumulated in the installation and operation and maintenance of cable crane were analyzed, and related entity classes of cable crane operation were extracted. A quintuple model was used to structurally express the safe operation of the ontology knowledge of the cable crane, and the binary relationship between classes was established. Then, the ontology expression language in Protégé was used to represent it programmatically. The ontology knowledge base of the cable crane entity, safety early warning and an emergency plan was constructed. 3D scene model of the cable crane was constructed using 3Dmax software, and then the model was imported into Unity3D engine. Knowledge retrieval of the ontology knowledge base was realized through user interface design and interaction functions in the engine. At the same time, based on the existing examples of faults and accidents, the corresponding emergency plans were associated with the hidden dangers existing in each entity of the cable crane. Finally, a complete 3D visualization platform for safe operation knowledge retrieval of cable cranes was constructed. The results show that all kinds of safe operation knowledge of cable-winch can be centrally and effectively managed by constructing an ontology knowledge base, and a knowledge retrieval platform combined with an ontology knowledge base can effectively realize efficient query and reuse of knowledge.

    Analysis of gas-liquid two-phase coordinated explosion and flame retardant effect based on fundamental reaction
    ZHANG Licong, LI Siman
    2024, 34(3):  101-108.  doi:10.16265/j.cnki.issn1003-3033.2024.03.1169
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    To improve the synergistic explosion suppression and flame retardant efficiency of inert gas-water mist, based on spectral experiments, theoretical analysis and numerical simulation methods such as Fluent and CHEMKIN-PRO were used to study the changes in elementary reactions and typical free radical (H· and ·OH) molar fractions during the explosion suppression and flame retardant process of N2 water mist at different injection positions and pressures. The results showed that staggered injection of N2 and fine water mist had better synergistic explosion suppression and flame retardant effect than convection and parallel injections. For case of simulated pipeline, good explosion suppression and flame retardant effect were found only when the spray pressure of N2 and water mist was 4.5 and 2 MPa, respectively. Furthermore, the maximum value of mole fraction for H· and ·OH was 0.006 4 and 0.006 9, respectively. The spray pressure can be applied to the actual methane explosion fire area based on scale effect. Moreover, the H· and ·OH mole fractions can be used as monitoring parameters during the operation of the current automatic fire extinguishing system in the fire protection area, and their changes can be used as a reference for fire extinguishing process.

    Virtual simulation experimental system for mine fire monitoring and prevention based on Unity3D
    PEI Xiaodong, YAO Zhiyuan, WANG Liang, SHAO Hao, WANG Kai, WU Zhengyan
    2024, 34(3):  109-116.  doi:10.16265/j.cnki.issn1003-3033.2024.03.0800
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    To better perform the experimental practical teaching and training of mining safety majors and cultivate first-class comprehensive top-notch talents in safety emergencies, a virtual simulation experimental teaching system for mine fire monitoring and prevention based on Unity3D was designed. Firstly, the simulation models were developed by 3ds Max, and then the overall framework of the experimental system for mine fire monitoring and prevention was constructed. Secondly, practical experimental trainings for human-machine interaction were conducted such as external fire monitoring and remote automatic control of disaster relief ventilation door emergency response, internal fire monitoring, and temperature-controlled cell coating chemical agent fire extinguishing emergency control. Finally, a comprehensive evaluation experimental evaluation system was proposed for assessment and evaluation. The results showed that the experimental system had the technical characteristics of immersion, interactivity, and conception of virtual reality, which created an underground three-dimensional virtual simulation scene and realistically displayed the evolution process of mine fires. For the experiments and practical training, the experimental system broke through the limitations of traditional models in terms of time, space, safety, and resources, providing self-directed learning and diverse evaluation methods.

    Review of fire smoke flow characteristics and early warning prevention and control of mine belt conveyor
    XU Yongliang, SUN Meng, WANG Lanyun, WANG Yungang
    2024, 34(3):  117-128.  doi:10.16265/j.cnki.issn1003-3033.2024.03.0393
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    To effectively prevent and control coal mine underground belt conveyor fire accidents and ensure the safety of lives and property of coal mine workers, the fire causes, combustion characteristics, smoke flow characteristics, monitoring and early warning technologies, and prevention measures of mine belt conveyor fires were systematically analyzed. Then, further prospects were proposed based on the current research status. The results showed that the main causes of belt conveyor fire were friction temperature rise, electrical equipment failure, and open flame. There were some limitations for the tunnel fire model and corresponding numerical simulation parameters used to study the fire combustion and smoke flow characteristics of belt conveyors, the actual working conditions and environmental parameters of the transportation tunnel should be comprehensively considered. Although there were monitoring and early warning systems for belt conveyor fires in China, they had some limitations. It was necessary to introduce emerging technologies such as 5G, big data, and artificial intelligence, and combine them with hardware detection and personnel management to improve the coal mine belt conveyor fire prevention and control system, and then comprehensively promote the construction of safety and intelligent in coal mine.

    Research on spatial distribution pattern of coal spontaneous combustion hazardous zone under condition of regenerated roof
    LI Min, LUO Ouwen, LU Yi, SHI Shiliang, LI He, LIN Zhijun
    2024, 34(3):  129-136.  doi:10.16265/j.cnki.issn1003-3033.2024.03.0890
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    In order to avoid the spontaneous combustion of residual coal from the regenerated roof during coal mining, the characteristics of interior fluid field were clarified, and the dynamic law of coal spontaneous combustion hazardous zone was explored. Taking the spontaneous combustion features of residual coal from the regenerated roof of a mine in Shandong province as an example, the numerical simulation method was used to simulate and compare the air leakage characteristics of goaf and regenerated roof under different air volume. Subsequently, based on the structural characteristics of the regenerated roof, the scope of coal spontaneous combustion hazardous zone was determined by adopting a new method of projection superposition judgment with oxygen concentration and air leakage speed as comprehensive indexes. The results of the study show that the oxygen mass fraction of goaf decreases gradually when the depth is smaller than 60 m, while it's no longer affected by the air volume when the depth exceeds 60 m. The oxidation zone is asymmetrically distributed, forming a "triangle" hollow area at the end of the return airway. The air leakage and backflow occurs in the range of 20-40 m in dip direction of goaf, whereas the air leakage velocity of regenerated roof presents a U-shaped symmetrical distribution. The change features of coal spontaneous combustion hazardous zone in the goaf resemble those of the oxidation zone. In contrast, the coal spontaneous combustion hazardous zone in the regenerated roof is mainly distributed near the middle of the intake airway and the inner part of the front middle of the return airway, and the area of coal spontaneous combustion hazardous zone gradually expands and extends towards the tail with the increase in air volume.

    Effects of inorganic salt and polysaccharide mixtures on physicochemical properties of foam extinguishing agents
    KANG Wendong, LU Yi, ZHANG Zuobin, LI He, XING Yuting, ZHOU Qinyun
    2024, 34(3):  137-147.  doi:10.16265/j.cnki.issn1003-3033.2024.03.1027
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    To further improve the fire extinguishing efficiency of environmentally friendly foam extinguishing agents, surfactants of the sodium alpha-olefin sulfonate (AOS) and phosphate betaine silicone surfactant (PBSS) and foam stabilizers of inorganic salts and polysaccharides were used to propose environmentally friendly foam extinguishing agents. The effects of inorganic salt and polysaccharide mixtures on surface tension, foaming capability, and foam stability were analyzed. Then the foam stabilization mechanism of the foam stabilizer mixtures was investigated. The results indicated that the inorganic salt and polysaccharide mixtures greatly improved the physicochemical properties of the foam extinguishing agents. The foam fire extinguishing agent mixture by 0.025% xanthan gum, 0.125% gelatin, and 0.1% MgCl2 showed the best overall performance with a surface tension of 24.34 mN/m, an initial foam height of 118.81 mm, and a 25% liquid drainage time of 132.1 s. The foam stabilizing mechanism of the foam stabilizer was attributed to the formation of hydrogen bonds between xanthan gum and gelatin, which greatly enhanced the surface strength of the foam liquid film, thereby effectively slowing down the drainage rate and bubbles coarsening of foam. Moreover, the Mg2+ was adsorbed around the AOS/PBSS head group due to electrostatic interaction, which impaired the electrostatic repulsion between the head groups and increased the concentration of surfactant, further improving foam stability.

    Fire prevention and extinguishing performance of phosphogypsum based self-produced gas expansion slurry
    WU Fanghua, SHI Shiliang, LU Yi, GU Wangxin, TAN Jiale, LIU Weiting
    2024, 34(3):  148-154.  doi:10.16265/j.cnki.issn1003-3033.2024.03.0099
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    In order to prevent high-level fire hazards such as spontaneous combustion of top coal and upper layer residual coal, a self-produced gas expansion slurry was prepared by taking industrial solid waste phosphogypsum as the base material, adding components such as sodium bicarbonate and polyacrylamide. Firstly, a thermogravimetry(TG) analyzer was used to study the thermal stability of the slurry at different heating rates. Then, a self-built insulation performance testing system was used to test the thermal insulation performance of the slurry. Finally, the fire extinguishing and cooling performance of the slurry was studied through fire extinguishing experiments. The results show that when the temperature of phosphogypsum based self-produced gas expansion slurry is below 160 ℃, there is a mass loss of 35% to 46% in the slurry. When the temperature is above 160 ℃, the mass fraction of the slurry no longer changes. The thickness of the slurry accumulation reaches 30 mm, and the effective insulation time exceeds 139 min, which can achieve good coverage of coal spontaneous combustion hazardous areas. The slurry expands and diffuses in the cracks of the coal pile, completely enveloping the broken coal from bottom to top, isolating oxygen, and having good cooling and fire extinguishing performance. After 36 min of grouting, the temperature at all points has been decreased to below 50 ℃, and no reignition phenomenon has occurred.

    Study on deviation characteristic of gas extraction borehole drilling in underground coal mine
    DU Dongdong, LEI Wenjie, LI Donghui, LI Zhe
    2024, 34(3):  155-161.  doi:10.16265/j.cnki.issn1003-3033.2024.03.0742
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    During the construction of underground extraction boreholes, trajectory deviation is common, prone to blind gas extraction areas and produces gas extraction blank zones. In order to ensure that gas extraction achieves the expected results, the 15121 bottom pumping lane, 15124 low level lane and 15124 return air lane of Xinjing mine in Shanxi province were taken as the background of the project. We tested the deviation of borehole drilling through the seam and along the seam respectively, calculated the three-dimensional trajectory of the drill holes by using the mean angle full distance method, established the three-dimensional trajectory of the drill holes and the three-dimensional layer relationship of coal rock based on the geological information of coal seam assignment, realized the visualization of the trajectories of the drill holes, analyzed the factors affecting the deviation of the drill holes and the experimental fitting data, and came up with a characteristic of the deviation of the boreholes. The research findings suggest that cross-layer boreholes initially exhibit deviation within fine sandstone layers, with the deviation intensifying notably within the coal seam segment, reaching a maximum deviation of up to 0.52 meters within this section. In the case of in-seam drilling, greater drilling depth results in larger vertical deviations, with an average vertical offset of 1.37 meters at a depth of 40 meters when the opening angles of boreholes are similar. Overall, low-angle boreholes are more susceptible to gravity-induced deviations, leading to a higher likelihood of trajectory deflection, while high-angle boreholes tend to exhibit vertical deviations, albeit with a smaller overall deviation compared to low-angle boreholes. In the horizontal direction, borehole spacing is reduced by 0.68 meters for bottom drainage galleries, 0.28 meters for lower position galleries, and 0.54 meters for return airways. The research results effectively guide the design of subsequent gas extraction drilling trajectories under the same geological conditions, provide theoretical support for controlling and eliminating the blind zone of gas extraction, and improve the efficiency and effectiveness of gas extraction.

    Multi-level disaster chain deduction analysis and case application of hazardous chemical accidents
    HE Qinglun, JIANG Wenyu, WANG Fei, LI Xin, WANG Zhi
    2024, 34(3):  162-170.  doi:10.16265/j.cnki.issn1003-3033.2024.03.1155
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    To enhance the risk prevention and control capabilities of hazardous chemical factories and support emergency decision-making in case of accidents, a multi-level deduction model for the disaster chain was proposed. Furthermore, three categories of key factors (such as thermal radiation, toxic gases, and overpressure) affecting hazardous chemical accidents were considered in the model. Based on the fluid diffusion model and Probit model, the fire probability and sequence simulation algorithm of hazardous chemicals container and the ignition time estimation algorithm of hazardous chemicals explosion were proposed, respectively. Then, the quantitative analysis of the combustion and explosion evolution process in hazardous chemical accidents was performed. For the case of a resin chemical production company in Guangdong province, a disaster chain caused by hazardous chemical leakage accidents was developed to analyze the evolution time and probability of each node. The results indicated that the proposed deduction model can effectively analyze the evolution process of the actual hazardous chemical disaster chain, predict the probability and time of accident nodes, and provide fundamental knowledge for the safety layout of hazardous chemical plants.

    Study on influencing factors and dust suppression effect of coal seam injection gum-forming dust suppressant
    LI Yi, LU Wei, LI Jinliang, CHEN Yunlong, ZHAO Shujie
    2024, 34(3):  171-178.  doi:10.16265/j.cnki.issn1003-3033.2024.03.1751
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    In order to solve the problems of easy water loss and poor dust suppression effect in coal seam water injection technology, a dust suppression method which can not only increase the water retention rate of coal seam but also improve the brittleness of coal seam was proposed. A gum-forming dust suppressant based on sodium alginate (SA) was developed. The effects of surfactant, viscosity and injection pressure on the gum-forming dust suppressant were tested by means of specific surface area test, nitrogen adsorption test, scanning electron microscope test and dust production rate test. The test results show that the surfactant is beneficial to the wetting of the coal seam, but has little effect on the dust suppression. The increase of the viscosity of the dust suppressant is conducive to water retention, which can increase the water retention time from 10 h to 30 h, but it will make it difficult for the material to enter the coal seam. The injection pressure has a great influence on the dust suppression effect of the dust suppressant. When the coal seam injection pressure is small, the dust suppressant is difficult to quickly penetrate into the internal pores of the coal. With the increase of pressure, the dust suppressant gradually penetrates into the coal pores. When the injection pressure rises to 3 MPa, the dust suppression effect no longer increases with the increase of pressure, and the dust production rate is reduced from 4% to 2.3%, which is relatively decreased by 50%, effectively reducing the dust production.

    Public safety
    Fire safety assessment of urban buildings
    ZHOU Enyi, TAN Lu, HU Jinrong
    2024, 34(3):  179-185.  doi:10.16265/j.cnki.issn1003-3033.2024.03.0201
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    In order to reduce the fire safety risk of urban buildings and improve the ability of building units to resist fire accidents, the influencing factors of fire safety were identified from three aspects: building fire protection design, building fire protection facilities and fire safety management, and the assessment index system of fire safety of urban buildings was constructed. A combined weighting-TOPSIS model of structural entropy and information entropy was applied to assess the fire safety risk of each district and each type of building in the cities. The model was validated with 262 buildings in 5 major areas of X city in western China. Finally, fire safety index and comprehensive ranking were obtained, and then the existing weak points of urban buildings fire protection were clarified. The results indicate that comprehensive evaluation order of fire safety is commercial complexes > primary and secondary schools > heritage buildings > high-rise buildings, city center > north of the city > east of the city > west of the city > south of the city. The fire safety risk of urban fringe counties and high-rises need to be paid attention to. The assessment results calculated with this model are consistent with the current situation.

    Study on evacuation of passengers from train compartment fires in low-vacuum tunnels
    CHEN Dawei, PANG Shijun, XI Yanhong
    2024, 34(3):  186-191.  doi:10.16265/j.cnki.issn1003-3033.2024.03.1785
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    In order to study the evacuation of passengers in a train fire in a vacuum tube transportation system and the smoke spreading law, The fire numerical simulation software FDS and the personnel simulation evacuation software Pathfinder were used to study the evacuation of passengers in case of fire in a high-speed train compartment consisting of 5 cars in a low-vacuum tunnel. Comprehensively comparing the evacuation time, the degree of smoke spread and the CO concentration in 10 evacuation schemes, the best evacuation method for passengers was obtained, and a rescue vehicle was designed to assist evacuation by docking the door of the high-speed train. The results show that: when the passengers in the fire compartment are evacuated to the neighboring compartments, the best evacuation method for the passengers is to leave the two rows of passengers close to the doorway and the rows of passengers close to the fire source at the same time, and then evacuate the passengers row by row by the distance from the fire source from near to far. If the rescue vehicle is used to assist the rescue, when the fire occurs in compartment 1, compartment 2, or compartment 3, the total time to complete the evacuation of all passengers after the arrival of the rescue vehicle is 533, 586, and 376 s, respectively. When a fire occurs in compartment 1, the utilization time of door 1 is 200 s; when a fire occurs in compartment 2, the utilization time of door 1 is 145 s; when a fire occurs in compartment 3, the utilization rate of the two doors is more balanced. Therefore, during the actual evacuation, passengers can be guided to fully utilize the two doors in the form of voice announcements to save the evacuation time. The research results can provide a reliable reference basis for the emergency rescue of passengers in future low vacuum tunnel train fires.

    Risk evolution analysis of eVTOL operation in UAM ecosystem based on complex networks
    YUAN Leping, GU Zekun, LI Dongqi
    2024, 34(3):  192-199.  doi:10.16265/j.cnki.issn1003-3033.2024.03.0266
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    In order to clarify the correlation of eVTOL risk factors, and explore their impact on risk prevention and control in the UAM ecosystem, complex network theory was used to establish a risk evolution model. Based on the UAV accident database at home and abroad and the statistics of general aviation accidents, combined with the operation characteristics of eVTOL in urban low-altitude scenes, 35 types of risk factors and 10 types of dangerous events were identified from the perspective of human-machine-environment. Gephi software was used to construct the network model, and the key nodes were evaluated comprehensively by the node degree, proximity centrality, internode centrality and PageRank(PR) algorithm. The key edges were evaluated by the internode number, so as to determine the key risk propagation path. In order to reduce the system risk, the measures to reduce the chain breaking disaster were proposed, and the system safety after chain breaking control was measured by network efficiency index. The results show that there are strong correlations among the eVTOL risk factors in the UAM ecosystem, and there are eight key risk transmission chains. The system safety is improved by 4.74%, 16.21% and 18.10% by blocking key human factors, key system technical failure factors and key intermediate dangerous events, respectively.

    Jet trajectory model of fire water cannon based on Euler method
    BAI Yangyang, LIU Changchun, LI Cunying, AI Guodong, LIU Siqi, SONG Fangzhi
    2024, 34(3):  200-205.  doi:10.16265/j.cnki.issn1003-3033.2024.03.1161
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    In order to improve the accuracy of fire water cannon jet trajectory prediction and overcome the difficulty of traditional parabolic theory to describe the phenomenon that "when the initial velocity is constant, the range increases with the increase of jet flow", first of all, the Euler method was used to establish a one-dimensional mass conservation equation along the trajectory of the water jet in the air, axial momentum conservation equations and the radial momentum conservation equations. Then, assuming that the axial velocity distribution of the water column and air column was in the shape of "bowler hat", the established conservation equations were derived and analyzed, and the fire water cannon water jet trajectory calculation model was established. Finally, based on three conservation equations, the numerical computation process of the jet trajectory model was given and verified with the collected experimental data. The results show that the error of this model is less than 10%.

    Technology and engineering of disaster prevention and mitigation
    Temporal and spatial dynamics and influencing factors analysis of environmental risk factors in Yellow River basin
    XU Xiaomin, LI Wei, HUANG Shengzhong
    2024, 34(3):  206-215.  doi:10.16265/j.cnki.issn1003-3033.2024.03.1420
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    To advance environmental risk prevention and control in the Yellow River basin and achieve high-quality development, this study utilized air pollution, water pollution and carbon emissions to characterize environmental risk factors in this region. Firstly, the kernel density estimation method was employed to construct a kernel function, perform density smoothing, and analyze the spatial agglomeration patterns and evolutionary characteristics of environmental risk factors. Secondly, a spatial autoregressive model that accounts for spatial dependence was adopted to dissect the influences of multidimensional factors on environmental risk factors. The results indicate that air pollution, water pollution, and carbon emissions are primarily concentrated in the middle and downstream cities of Yellow River basin, delineating distinct regions for environmental risk prevention and control. Optimizing industrial structures and promoting green technological innovation in enterprises can reduce environmental risk factors. However, unreasonable energy conservation and environmental protection expenditures may lead to an increase in environmental risk factors. Furthermore, an inverted U-shaped relationship was observed between economic levels and population density and risk factors. From a long-term strategic perspective, regional collaborative governance and synergistic pollution reduction and carbon mitigation should be the strategic priorities. Strengthening cooperation among middle and downstream cities, optimizing industrial structures and increasing investment in industrial technological innovation are crucial steps towards achieving an economic development model transformation.

    Emergency technology and management
    Networks robustness evaluation of urban flood emergency organizations from perspective of emergency plans
    LIU Xinnan, XUE Tingting, JI Yingbo
    2024, 34(3):  216-221.  doi:10.16265/j.cnki.issn1003-3033.2024.03.1267
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    In order to address the difficulty to quantifying the emergency coordination ability of related organizations during the formation of urban flood emergency plans, a method to evaluate the robustness of inter-organizational networks for urban flood emergency response considering cascading failure was proposed. First, the inter-organizational networks for flood control emergency plans in Beijing, Shanghai and Shenzhen were established, and attack strategies and evaluation indexes of network robustness were proposed. Secondly, network characteristic statistical parameters are computed, and the network topology properties were analyzed. Then, the natural connectivity was selected as the robustness indicator to evaluate the network robustness under node single-attack strategy and continuous attack strategy. Finally, the robustness of networks under different attacks was compared, and the key organizations that have a great influence on robustness were found. The results indicate that inter-organizational networks of urban flood control emergency plans in Beijing, Shanghai, and Shenzhen have small-world and scale-free characteristics. Under single attacks of nodes, compared with the case of non-cascading failures, the robustness of inter-organizational networks is weaker considering cascading failures. Organizations with a large number of failure nodes are key to making the networks robust. Under continuous attacks, networks are strongly robust to random attacks, but weakly robust to deliberate attacks, where organizations with high degree values are key to making networks robust.

    Emergency rescue allocation decision-making based on three-sided matching theory
    GUO Qian, ZHOU Yike, WU Gang
    2024, 34(3):  222-229.  doi:10.16265/j.cnki.issn1003-3033.2024.03.0625
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    To address the issues of allocation of emergency rescuers, emergency rescue equipment, and disaster locations in the early stage of emergency rescue under the background of large-scale geological disasters, as well as improve the efficiency and quality of emergency rescue, an emergency rescue allocation decision-making method was proposed based on the three-sided matching theory. Firstly, the selection process among the three parties of emergency rescue was presented as a three-sided matching issue. Then, the multi-attribute preference evaluation information of the matching three parties was standardized, and a multi-attribute comprehensive preference score matrix was proposed. Furthermore, a three-sided matching stable and satisfactory model in the early stage of emergency rescue was developed to maximize system stability and total preference utility. Finally, the performance and accuracy of the proposed model were validated against cases. The results indicated that the proposed model reached reasonable matching between rescuers, emergency rescue equipment, and disaster locations in emergency rescue scenarios due to considering the effects of various parties' preferences on resource allocation. Furthermore, it can contribute to reducing the deployment time of emergency rescue operations and improve emergency efficiency and quality.

    Occupational health
    Knowledge graph analysis of research progress in occupational health of coal miners
    YU Haimiao, XU Zepeng, ZHANG Shuo, QI Hui
    2024, 34(3):  230-236.  doi:10.16265/j.cnki.issn1003-3033.2024.03.1619
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    To investigate the development trend of occupational health of coal miners and promote the implementation of occupational health protection in coal mines. Based on the knowledge graph analysis method, CiteSpace software was used to conduct the keyword clustering and emergence of coal miners' occupational health literature included in the core databases of China National Knowledge Infrastructure(CNKI) and Web of Science(WoS) in the past 20 years. The results indicated that coal miners' occupational health research topics were divided into occupational health, occupational hazard factors, and career-related diseases. Occupational-related diseases focused on behavioral and physical diseases, cardiovascular and cerebrovascular diseases metabolic diseases, and chronic non-specific respiratory diseases. Compared with occupational diseases, occupational-related diseases had the characteristics of 'multiple causes and one effect', causing much more difficulty in diagnosis. Pneumoconiosis, hearing loss, psychological stress, and hypertension were the main factors threatening coal miners' health. Moreover, such health issues were associated with occupational exposure, and risk analysis and control were important strategies to deal with hazard factors. The emerging research hotspots were the cause and prevention of occupational-related diseases, and the multi-discipline research of occupational health, brain science, and intelligence.

    Helmet-wearing recognition algorithm for coal mine underground operation scenarios
    ZUO Mingcheng, JIAO Wenhua
    2024, 34(3):  237-246.  doi:10.16265/j.cnki.issn1003-3033.2024.03.1985
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    To improve the accuracy of miners' helmet-wearing recognition in coal mine underground operations, a helmet-wearing recognition algorithm was proposed based on human posture analysis and machine vision system optimization methods. First, Single Shot MultiBox Detector (SSD) was used as the basic model of multi-target identification. The squeezed neural network (SqueezeNet) was used to reduce the model parameters to develop an efficient recognition model, which improved the recognition accuracy of the miners' helmet and maintained the balance between the recognition accuracy and the calculation speed. Then, a multi-person posture estimation algorithm was used to locate the joint points of each miner and determine the miners' complex behavioral status. Finally, the upper limb nodes of the target were extracted based on fusion model of multi-target recognition and multi-person posture estimation, and then the helmet-wearing condition was determined by the spatial topological relationship between the upper limb nodes and the helmet frame. Moreover, 3 000 pieces of image data were selected to validate the proposed method's performance. The results indicated that the machine vision system can optimize the hardware and software configuration to improve the system's performance. Furthermore, the identification accuracy reached up to 91.1%, which was much better than that of the latest helmet-wearing recognition algorithm. Therefore, the proposed system in this study can meet the requirements of helmet-wearing recognition accuracy for underground coal miners.