China Safety Science Journal

Stochastic fuzzy coupled risk measurement for production safety events

JIN Zhixin, LIU Qian, DENG Cunbao, WANG Yansheng

2021, 31(1): 1-7. doi:10.16265/j.cnki.issn 1003-3033.2021.01.001

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In order to address randomness of factor state change and fuzziness of state change range in risk measurement of production safety events, relationship between their instability domain and activity environment attribute space was analyzed based on safety structure theory. Three kinds of risk models were explained, including safety type, dangerous type and controllable type. Then, probability theory and fuzzy theory were used to mathematically describe random risk, fuzzy risk and stochastic fuzzy coupled risk of the events. Finally, with gas volume fraction taken as object, a calculation example of stochastic fuzzy coupled risk measurement analysis was obtained. The results show that the risk of gas volume fraction on the working face is 24.41%, and state probability density distribution of environmental factors and fuzzy membership degree of factor state have a dual impact on risk of safety events, which verifies feasibility of stochastic fuzzy coupled model to some extent.

Grassroots grid emergency governance: main challenges and improvement paths

XU Shuhua, CHAN Kinsun, QI Hui

2021, 31(1): 8-17. doi:10.16265/j.cnki.issn 1003-3033.2021.01.002

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In order to enhance grassroots′ capabilities in handling emergency, and improve their grid emergency management, with emergency prevention and control of COVID-19 as a reference, residents′ recognition on grassroots grid management ability was evaluated at three stages, namely before, in the middle and after crisis by adopting case study and web survey. Then, roles and effects of different entities in emergency management as well as problems of the system were identified before improvement path was found. The results show that there are some problems in preparedness, and it is high time to develop a co-governance body of grid emergency management among local government, corporate, community, and residents. Thus, a well structured emergency governance capability model with diversified governance entities and full governance methods can be established, which can effectively resolve the predicament of lack of grid emergency management capabilities at grassroots level

Research on influencing factors of social practice safety risk in colleges and universities

QIN Shuai

2021, 31(1): 18-23. doi:10.16265/j.cnki.issn 1003-3033.2021.01.003

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In order to improve capacity of colleges and universities to deal with social practice safety risks,firstly, through used method of literature review and risk classification induction,four kinds of influencing factors were confirmed, including school education, practical environment, family factors and personal factors. Secondly, questionnaire was set reasonably based on four kinds of factors, reliability test, validity test and correlation analysis were carried out by SPSS software. Finally, basic analysis and correlation analysis of variable data were conducted.The research results show that various factors have different influence on the safety risks, influence of school education and practical environment are obvious, influence of individual factors except gender isn't obvious. Students have a strong sense of personal safety prevention, but their ability to resolve safety risks is limited.Safety drill, prevention skills, follow-up education have an obviously negative correlation with safety risks.

Safety route planning of UAV based on improved ant colony algorithm

HAN Peng, ZHANG Bingyu

2021, 31(1): 24-29. doi:10.16265/j.cnki.issn 1003-3033.2021.01.004

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In order to reduce UAV crash accidents, firstly, air route safety cost function was established with casualty of ground personnel per flight hour as index to define risk factor of grids through UAV air space gridding Then, route planning method under double restraints of distance and safety was explored considering UAV route cost, and optimal route was planned based on improved ant colony algorithm. Finally, validity of the planning model was verified by urban UAV logistics distribution scenario before difference in planning results with safety factors being taken into account or not.was compared.The results indicate that the air route planning model considering such factors can improve flying distance and time by within 30%, but the casualty rate through the whole route can be reduced by as much as 60%.

Impact of subjective social support on psychological state and unsafe behavior of construction workers

CHEN Mei, QI Shenjun, NIU Dayu, ZHANG Yunbo, WU Guolai

2021, 31(1): 30-37. doi:10.16265/j.cnki.issn 1003-3033.2021.01.005

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In order to reduce UB of construction workers caused by SSS, structural relationship between their psychological state and unsafe behavior was explored from perspective of SSS. Basic relationship among variables were obtained through literature review analysis, including SSS, SW, PP, safety awareness and UB, and a hypothesis model of UB under SSS was established. Then, 371 valid questionnaires were obtained, and the model was fitted by AMOS software. The results show that family support is an important component of SSS for construction workers with load coefficients of family's concern and support respectively reaching 0.90 and 0.86. SSS has positive influence on SW and an inhibitory effect on PP. Good psychological state can help improve safety awareness and handing ability of emergencies in early stage, thus reducing UB and injury.

Comparative study of coal mine fire areas zoning methods based on isotopic radon measurement technique

ZHANG Junying, FANG Xiyang, WANG Haibin, WANG Haiyan, YAO Haifei, LI Kun

2021, 31(1): 38-44. doi:10.16265/j.cnki.issn 1003-3033.2021.01.006

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In order to determine optimal calculation method for identification of abnormal temperature areas, firstly, three commonly used regional data processing methods (traditional statistical method, trend surface analysis method and fractal method) were applied to process radon measurement data of actual mine surface. Then, differences of three methods were compared and analyzed from ability of strengthening weak anomalies and determination of outlier threshold. Finally, representative boreholes were selected to verify anomaly areas determined by the three methods. The results show that the lower limits of radon anomaly of traditional statistical method and fractal method are 5 982 Bq/m³ and 7 094 Bq/m³ respectively, and trend surface analysis method is used to determine anomaly area by positive residual component. In delineating abnormal areas according to its consistency with ability of strengthening weak anomalies, the three methods rank as trend surface analysis method > fractal method > traditional statistical method. By comparing results of drilling verification, it is determined that results delineated by fractal method can be used as basis for later fire-fighting activities.

Simulation study on gas explosion and discharge process in H-type ventilation roadway

MA Heng, CHEN Xiaojun, JING Deji

2021, 31(1): 45-51. doi:10.16265/j.cnki.issn1003-3033.2021.01.007

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In order to study changes of pressure and air flow pattern during gas explosion and its release in H-type roadway, Fluent was used to simulate process of explosive blast damaging stable ventilation of roadway. Then, CO₂ concentration, temperature and fluid movement in tunnel before and after explosion were compared and analyzed, and propagation features of explosion shock wave in tunnel were obtained. The results show that explosive shock wave is reflected by roadway wall and superimposed with positive one, which increases pressure value in superimposed area. Shock wave causes air flow state in connecting lane to change from a double vortex mode to a single vortex mode. Moreover, during venting process, roadway on the side of gas-filled area has a large venting capacity, and a large number of shock waves generated by explosion are discharged along this side. After explosion, the tunnel can resume normal ventilation.

Study on performance of F-ZrP@Co-MOF synergistic intumescent flame retardant polypropylene

OU Hongxiang, YE Qing, XU Jiacheng, LIU Ben, SHAN Xueying, JIANG Juncheng

2021, 31(1): 52-59. doi:10.16265/j.cnki.issn 1003-3033.2021.01.008

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In order to improve thermal stability of PP and reduce negative effects of IFR on PP's mechanical properties, hexachlorocyclotriphosphazene and melamine formaldehyde resin were used to modify zirconium phosphate-metal organic framework hybrid materials (ZrP@Co-MOF) and to prepare a novel nano flame retardant F-ZrP@Co-MOF which, combined with ammonium polyphosphate and dipentaery-thritol, synthesized IFR/F-ZrP@Co-MOF flame retardant. Then, effects of F-ZrP@Co-MOF on combustion and mechanical properties of PP composites were analyzed with 25% mass-ratio addition of IFR/F-ZrP@Co-MOF.The results show that without addition of F-ZrP@Co-MOF, limiting oxygen index (LOI) of PP/IFR is 29.6% while with 3.0% addition of it, LOI value will be improved by 6.08%. With 1.0% addition, residual carbon contents at 800 ℃ is increased by 180.1% compared with no addition at all, and with 2.0% addition, elastic modulus will be 57.21MPa, 8.3% higher. The Raman spectrum and smoke density tests further prove that addition of F-ZrP@Co-MOF makes carbon layer more compact and stable, which is beneficial to restraining heat and smoke transfer.

Size effect of methane-air mixture explosion in closed vessel

WANG Zhirong, SUN Peipei, TANG Zhenhua, ZHANG Kai

2021, 31(1): 60-66. doi:10.16265/j.cnki.issn 1003-3033.2021.01.009

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In order to explore size effect and change laws of methane explosions in closed vessel, and to better prevent and control such accidents, explosion pressure characteristics of methane-air mixture in a closed vessel were studied by changing length and diameter of cylindrical container and pipes. Then, a multiple linear regression model was used to analyze relationship between maximum explosion pressure and its rise rate with pipe diameter and length. The results show that in a cylindrical vessel, maximum explosion pressure rise rate decreases along with increase of vessel volume, and both it and its rise rate at end of pipes will decrease as inner diameter of pipes increases, but will increase as pipe length increases. A dimensionless predictive model of maximum explosion pressure and maximum pressure rise rate is obtained through experiment.

Pull-out test study on interface characteristics of traixial geogrid and fine tailings

YI Fu, YU Ben, YU Huize, DU Changbo, JIN Hongsong

2021, 31(1): 67-74. doi:10.16265/j.cnki.issn 1003-3033.2021.01.010

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In order to improve safety and stability of fine tailings dam, a method of strengthening its mechanical properties by traixial geogrid reinforcement was put forward, and pull-out tests of biaxial and traixial geogrid under different conditions were carried out with fine tailings as fillers. Then, difference in reinforcement effects of these two geogrids were analyzed, and influence of relative density, water content and normal stress on interface characteristics of traixial geogrid were emphatically studied. The results show that traixial geogrid has better reinforcement effect than biaxial one, and interface strength parameters show difference of pseudo-friction angle. Moreover, the higher normal stress is, the better reinforcement effect of traixial geogrid will be. It is also found that increase of relative density significantly improves interfacial friction strength, and pseudo-cohesion and friction coefficient ratio monotonically increase along with relative density while apparent friction angle changes little. Interfacial friction strength at natural water content is greater than that at saturated water content. The former has 1.28 times of the latter's pseudo-cohesion, while pseudo-friction angle are approximately equal.

Application of MI and SVM in coal and gas outburst prediction

ZHENG Xiaoliang, LAI Wenhao, XUE Sheng

2021, 31(1): 75-80. doi:10.16265/j.cnki.issn 1003-3033.2021.01.011

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In order to address problems of small quantity of accidents training data and lack of data set that can be used in coal and gas outburst prediction model, MI data mining algorithm was presented to fill up missing parameters in accident data and increase available data sets. Then, imputed data were employed in SVM prediction model's training and testing, and K-Nearest Neighbors (KNN) algorithm was selected and compared with SVM. The results show that the average recognition rate of SVM algorithm is 88.37% and 88.87% before and after data inputting respectively, and recognition rate of accident data is 79.71% and 91.27% respectively. That of KNN algorithm before and after data inputting is 87.59% and 88.37% respectively while accident recognition rate being 70.4% and 84.23%, respectively. Therefore, MI has little effect on improving average recognition rate, but has a greater one on improving accident recognition rate, which can improve prediction rate of coal and gas outburst accidents. The incident recognition rate of SVM algorithm is higher than that of KNN algorithm after data inputting.

Nuclear magnetic resonance experimental study on pore structure and fluid characteristics of coal at different ranks

YANG Ming, LIU Lei, ZHANG Xuebo, MAO Junrui, CHAI Pei

2021, 31(1): 81-88. doi:10.16265/j.cnki.issn 1003-3033.2020.01.012

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In order to explore characteristics of coal reservoir structure and internal fluid distribution, with 10 sets of coal samples from different regions as research objects, low-field nuclear magnetic resonance tests of coal under different conditions were carried out by using saturated, centrifugal and low-field nuclear magnetic resonance system. Based on conventional single T₂ cutoff value, double T₂ cutoff value was proposed to be used to distinguish non-recoverable fluid, capillary bound fluid and movable fluid in coal. Then, a fluid saturation model was established, and pore structure and fluid characteristics of coal at different ranks were studied. The results show that with increase of coal rank, proportion of micro pores gradually increases, and that of adsorption pore throat increases from 51.77% to 90.19%, while that of medium and large ones gradually decrease with seepage pore throat dropping from 48.23% to 9.81%. However, as coal rank decreases, connectivity between pores becomes better, and permeability increases from 0.03 mD to 1.88 mD. Moreover, porosity of coal samples ranges from 0.73% to 11.50%, main distributions of T_2CI and T_2CII are 0.17～2.31 ms and 0.97-15.70 ms, and corresponding saturation distribution is 4.21%-53.33%, 34.67%-66.60%, and 6.19%-37.84%.

Research on MS regional detection technology for coal and gas outburst hazard

SONG Dazhao, HE Xueqiu, DOU Linming, ZU Ziyin, WANG Anhu, LI Zhenlei

2021, 31(1): 89-94. doi:10.16265/j.cnki.issn 1003-3033.2021.01.013

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In order to address lack of regional on-line detection and early warning technology in coal and gas outburst coal mines, MS technology, which could correctly reflect dynamic and static loads, was applied in outburst-prone mines, and spatial and temporal evolution characteristics of driving-induced MS signals were studied. Then, distribution characteristics of regional stress field in heading face were calculated based on seismic wave CT before relationship between abnormal stress area and accident locations was compared and analyzed. At last, prospect of MS technology's application in outburst-prone mines was explored. The results show that MS events in soft coal seam are mainly distributed in stress concentration area, excavation disturbance area and tectonic influence area. When heading face gradually approaches geological structures, MS energy and events will tend to increase. The results of regional stress field based on seismic wave velocity inversion are consistent with stress concentration caused by main roadway uphill, stopping line and heading face. The location of outburst event in Jinjia coal mine corresponds well to abnormal stress area detected by CT technology, and outburst are more likely to occur where velocity gradient changes greatly.

Electrochemical corrosion mechanism of titanium alloy in chemical equipment under influence of high temperature

WANG Jinghong, MENG Qinglong, WANG Cangtian, ZHI Youran

2021, 31(1): 95-101. doi:10.16265/j.cnki.issn 1003-3033.2021.01.014

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In order to prevent corrosion accidents of equipment due to decrease in corrosion resistance of titanium materials after suffering from high temperature of a fire in chemical industry, corrosion behavior characteristics of titanium alloy TC4 after being treated by high temperature and different cooling methods, i.e., air cooling and water cooling, were studied through polarization curve and electrochemical impedance spectroscopy (EIS) by using electrochemical test technology. Then, a corresponding electrochemical corrosion model was constructed to explore relationship between characteristics of EIS and pore depth. The results show that TC4 sample can obtain the lowest corrosion current density after air cooling and water cooling treatment respectively at 1 050 and 910 ℃ with that of water cooling lower than air cooling. This means that when heating temperature is close to phase transition point temperature (about 1 000 ℃) of TC4, water cooling can make samples more resistant to corrosion than the other. Therefore, it proves to be a better cooling measure after titanium equipment is exposed to fire. In addition, based on results of scanning electron microscope, it is found that relationship between EIS characteristics and hole depth could reflect corrosion of TC4 more accurately. So the proposed model provides a theoretical basis for corrosion severity evaluation of titanium alloy equipment.

Research on comprehensive performance evaluation system of large multi-functional rescue attachments

JIANG Tao, ZHANG Yulong, LI Shibo, LI Zheng, QIU Hailiang

2021, 31(1): 102-108. doi:10.16265/j.cnki.issn 1003-3033.2021.01.015

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In order to improve rescue efficiency of construction machinery, firstly, existing problems and difficulties were analyzed, including multiple indicators and conflicts in evaluation of multi-functional rescue attachments' performance. Then, a comprehensive evaluation system of their performance based on principle of “safety and efficiency” was established from three levels, objective, standard and indicator levels and five aspects including production, basic function, transportation capacity, safety and operational ability. Finally, the improved AHP-fuzzy comprehensive evaluation method was used to evaluate performance of three kinds of multi-functional rescue attachments. The results show that their comprehensive performance ranks from high to low asbreaking-opening rescue attachment, shearing-expanding rescue attachment, and grabbing-lifting rescue attachment.Moreover, evaluation results based on the above system are basically consistent with judgment results based on experience.

Fast estimation method of UDMH diffusion concentration in long storage warehouse

CUI Cunyan, LIU Ningyuan, DUAN Yongsheng, TONG Jiang

2021, 31(1): 109-115. doi:10.16265/j.cnki.issn 1003-3033.2021.01.016

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In order to quickly obtain key information which is necessary to determine location of leakage source in long storage wareroom of UDMH, influence of storage tank, wall surface and ventilation state on diffusion law of UDMH vapor in wareroom was studied based on numerical simulation method. Furthermore, parameters in gas diffusion formula were revised to make it suitable for fast estimation of UDMH diffusion concentration distribution under special layout and state conditions in long storage warerooms. Finally, errors of calculation formula under different leak locations were analyzed. The results show that the relative position between leak location and storage tank has a greater impact on local diffusion parameters, which makes error of fast estimation result nearby storage tanks larger, but average error between storage tanks is less than 10%.

Research on safety and stability of UHV transmission line foundations under rainfall

DONG Jianjun, YANG Di, ZHENG Gaoyang, XIE Zhengquan

2021, 31(1): 116-124. doi:10.16265/j.cnki.issn 1003-3033.2021.01.017

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In order to address impacts of rainfall on uplift bearing capacity and safety and stability of UHV transmission line pole and tower foundations, based on load-displacement data obtained from in-situ test and soil parameters obtained from laboratory test, a theoretical model was established according to seepage equation and unified shear strength equation for saturated and unsaturated soils. Then, numerical simulations and analysis were carried out by using the model, and simulation results were found to be in agreement with those of in-situ uplift tests. Finally, based on verified theoretical model, evolution characteristics of seepage field in both unsaturated and saturated soils, development of plasticity zone of soils, and changes in bearing capacity of foundations under different rainfall conditions were studied. The results show that ultimate bearing capacity is related to depth-to-diameter ratio of foundations when infiltration ratio remains the same, and it will be significantly reduced as depth-to-diameter ratio becomes smaller, causing safety and stability of foundations to decline.

Study on safety optimization of embedding ratio of sand gravel deep foundation pit

FENG Zhentu, LI Da

2021, 31(1): 125-131. doi:10.16265/j.cnki.issn 1003-3033.2021.01.018

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In order to guide economic design and safe construction of deep foundation pit support structure in sandy gravel stratum, an optimization method of embedded depth (ratio of embedment) for supporting structure was put forward based on multiple safety evaluation indexes.with Luoyang Metro as an example Considering special properties of sandy cobble stratum which required construction of deep foundation pit to meet certain requirements of deformation and safety factor, surface settlement, stability of supporting structure, safety against uplift and safety against underground water gushing were analyzed, and selection range of embedding ratio was optimized based on limited displacement and safety factor. The results show that due to difference of groundwater level and exposed depth of pebble layer, Luoyang sandy cobble stratum can be divided into two types, and optimal embedding ratio ranges of type I (medium groundwater level and shallow exposed sand gravel) and type II (low groundwater level and deep exposed sand gravel) of deep foundation pit are 0.28 ～ 0.52 and 0.2 ～ 0.44, respectively.

Damage assessment of mine seal under blast impact load

CHENG Jianwei, ZHANG Xixi

2021, 31(1): 132-137. doi:10.16265/j.cnki.issn1003-3033.2021.01.019

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In order to study anti-explosion performance of typical brick seals in coal mines, ANSYS software was used to establish a numerical model to study damage of seals under explosion impact. Firstly, characteristics of gas explosion and propagation characteristics of shock wave pressure caused by it in roadway were analyzed, and pressure intensity amplitude of shock waves was predicted. Then, a numerical model of seals was established and simulation experiments of impacts under various impulse and pressure loading modes were designed and conducted. Finally, by using self-defined damage variables and simulation results, P-I curve damage diagram of brick seals was made. The results show that damage state of seals under different combinations of impacts varies significantly. As explosion in reality may be more complex, damage threshold equation and P-I curve damage diagram of brick seals obtained in this paper can be used to determine damage state of seals under other explosion impacts.

Comparative study on vehicle-to-vehicle collision speed based on inverse algorithm and trial algorithm

LIU Yongtao, FANG Tengyuan, ZHAO Junwei, CAI Pengliang, ZHAO Chen

2021, 31(1): 138-144. doi:10.16265/j.cnki.issn 1003-3033.2021.01.02

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In order to improve accuracy and practicality of road traffic accident speed calculation simulation, with actual vehicle-to-vehicle collision accidents as subject, road traffic accident analysis, reproduction system (Crash View) inverse algorithm and Pc-Crash test algorithm were utilized to compare and analyze its and analyze its calculation system, model algorithm, input parameters, output error and other core calculation parts. Then and other core calculation parts. Then, speed calculation method was optimized and actual accident scene speed was obtained. Relative error of Crash View system was about 4%, and input parameters of vehicle position, body structure, body posture were comparatively less and easy to obtain. That of Pc-Crash system was around 9%, and manually repeated trial adjustment of speed, position, attitude and other parameters was required. The results show that the simulation reproduction system with inverse algorithm on Crash View is more suitable for the calculation of actual traffic accident speed while trial algorithm on Pc-Crash is greatly affected by empirical formula with a small scope of application.

Feature extraction of QAR data based on QAR2Vec model

DUAN Zhaobin, DU Hailong, ZHANG Peng

2021, 31(1): 145-152. doi:10.16265/j.cnki.issn 1003-3033.2021.01.021

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In order to address difficulties that traditional extraction methods have in extracting effective features from massive and high-dimensional QAR data which lack sufficient labeled data, a QAR2Vec model was proposed with Transformer as its core. Firstly, QAR data were co-encoded with location and flight phase information as input of the model. Secondly, pre-training task of autoregressive prediction was constructed to learn deep features of massive QAR data in a way of self-supervision. Finally, scale of pre-trained QAR2Vec model was recorded and slightly adjusted on flight state prediction and landing abnormal weather recognition tasks, and performance of QAR2Vec model was evaluated by comparing it with two deep learning algorithms—CNN-LSTM and MTL-LSTM without pre-training steps. The results show that QAR2Vec can extract features from QAR data more effectively, with lower errors and higher accuracy on flight status prediction and landing abnormal weather recognition tasks

Development of urban lifeline monitoring standard system

FU Ming, TAN Qiong, YUAN Hongyong, LIANG Guanghua, CHEN Tao, LING Junjie

2021, 31(1): 153-158. doi:10.16265/j.cnki.issn1003-3033.2021.01.022

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In order to improve monitoring on urban lifeline operation in China, extensive research was conducted, and methods to compile a standard system for city lifeline operation & monitoring were studied based on status of the standard system for this in China and characteristics of urban lifeline monitoring industry. Then, framework and content for building such a standard system were constructed with five subsystems including basic standards, construction standards, technical standards, service standards and management standards. The results show that China's urban lifeline monitoring standard system still needs further improvement. It requires collaborative innovation between engineering technology and management in its development, and the standard system should be updated in time.

Risk evolution and evaluation for oil and gas leakage of pipeline in shallow sea

REN Yuefeng, MENG Xiangkun, CHEN Guoming

2021, 31(1): 159-164. doi:10.16265/j.cnki.issn 1003-3033.2021.01.023

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In order to prevent oil and gas pipeline leakage in shallow sea, a novel evaluation method integrating complex network and FMECA was proposed. Considering pipeline structure, leakage development process and logic relation between risk factors, a complex network model, which consisted of risk factors such as natural environment, internal and external corrosion, third party damage, and organizational management, was constructed. Then, risk entropy and FMECA were introduced to characterize probability and criticality of risks. Finally, the shortest path was applied with Dijkstra algorithm to identify the most potential failure modes of pipeline leakage. The results show that effect of initial events on leakage varies a lot. Inappropriate operational organization, as initial event with a probability of 5.20×10^-3 to cause accidents, has the greatest influence on leakage.

Fire probability analysis method of cable cabin in urban utility tunnel

MI Hongfu, ZHANG Xiaomei, YANG Wenjing, WANG Wenhe, LIU Yaling, JIAO Yifei

2021, 31(1): 165-172. doi:10.16265/j.cnki.issn 1003-3033.2021.01.024

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In order to improve evaluation accuracy of fire risk in cable cabin, a BN-based model for fire probability prediction and analysis was proposed. Firstly, BTA method was used to analyze causes of fire in cable cabin, and potential fire accident scene was established. Then, with influence of uncertain factors in accident scene taken into consideration, BN was applied to fire probability prediction and analysis, and the model was optimized based on actual development of cabin fire. Finally, with a utility tunnel as an example, the model's logic was verified on the ground of literature and statistical data. The results show that this model and method can predict and analyze occurrence and development probability of fire in cable cabin, and explore cause chain of these accidents, which provides a reference for fire risk analysis and accident prevention and control in utility tunnel.

Research on transmission of infectious diseases in motor vehicles based on SIR model

GUO Yunlong

2021, 31(1): 173-178. doi:10.16265/j.cnki.issn 1003-3033.2021.01.025

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In order to control spread of infectious diseases in motor vehicles, their transmission mechanism and influencing factors were studied by using infectious disease transmission model. Based on theory of infectious disease dynamics and by introducing concept of virus transmission density, SIR model of infectious diseases in buses and small private cars was established considering transmission mode of COVID-19 and driving characteristics and transmission environment of motor vehicles. Then, the model under different driving conditions were studied through numerical simulation analysis and comparison. The results show that virus transmission in cars can be suppressed during outbreak of epidemic by adopting strategies, like reducing driving time and people exchange frequency, enforcing ventilation and disinfection, and making appropriate choices for bus and private car travel according to preventative and control environment.

Research on optimization for utilization of arrival and departure tracks at high-speed railway station under condition of safety constraints

REN Yumou, ZHANG Qi, YUAN Zhiming, SUN Yanhao

2021, 31(1): 179-185. doi:10.16265/j.cnki.issn 1003-3033.2021.01.026

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In order to ensure high-density safe and stable operation of high-speed trains, and to improve stations' intelligent operation planning, with balanced use of arrival and departure tracks as a goal, optimal plans of their distribution was made to reserve space for dynamic adjustment when the train is late. Then, an overall optimized model was established with relationship between throat area and arrival and departure tracks were being considered, and a genetic tabu hybrid algorithm was designed. Finally, driving data of a high-speed railway station for a certain period of time was taken as an example to verify the model. The results show that the optimized model can effectively improve balance of arrival and departure tracks' utilization, and avoid collision of trains in throat area, thus enhancing anti-interference ability of the plan. At the same time, the genetic tabu hybrid algorithm converges when it evolves to about 70 generations.

Experimental study on fire self-extinction phenomenon in tunnel with different slopes

WANG Zhongkuan, SU Mengmeng, HUANG Xin, ZHENG Jingru, LI Zihao, WANG Guoyuan

2021, 31(1): 186-191. doi:10.16265/j.cnki.issn 1003-3033.2021.01.027

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In order to explore self-extinction phenomenon of fire in tunnels with different slopes, with America′s Memorial Tunnel as a prototype, a 1/20 reduced-scale model tunnel was constructed based on Froude scaling law and a series of experiments were conducted by using methanol to investigate fire in tunnels under natural ventilation. Then, information of velocity, temperature and oxygen concentration were obtained through data acquisition system. The results show that there is no self-extinction phenomenon in experiments with a slope of 3% and 5%, while it occurs in cases of zero and 1% slope except when heat release rate(HRR) is at 2.8 kW, and the greater HRR is, the shorter self-extinction takes. Existence of tunnel slopes causes hot smoke to form stack effect due to buoyancy, and the larger slope is, the stronger stack effect will be. As tunnels with a slope of 3% and 5% form larger longitudinal wind speed, they restrain self-extinction while in tunnels with a smaller slope, the phenomenon occurs because oxygen concentration near the fire source has fallen to the limit.

Deduction of leakage accident scenarios of oil pipelines based on Bayesian network

QU Jing, ZHANG Jianbin, LI Xufang, LU Bao, HUA Ning, ZHU Xiaoman

2021, 31(1): 192-198. doi:10.16265/j.cnki.issn1003-3033.2021.01.028

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In order to improve emergency management of oil pipeline enterprises, a method combining scenario analysis and dynamic Bayesian network was used to study evolution process of oil pipeline leakage accident scenarios. Based on analysis of typical leakage cases, accident scenario state, emergency measures, driving factors, and emergency targets were selected as key elements, a scenario deduction model was established building on dynamic BN, and evolution law and path of leakage accident scenarios were analyzed. Finally, this model was applied to a leakage accident that occurred in an oil and gas pipeline company in China to calculate probability of scenario state and derive its development trend. The results show that scenario states that have a high probability to cause accidents are "pipeline damage and crude oil leakage caused by third-party construction excavations", "open flames on the ground", "ground residual fire", and "hidden danger of road surface residual oil burning".

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