China Safety Science Journal

Research on DEMATEL-BN model of construction risk transmission for prefabricated building

CHEN Wei, YANG Zhuzhang, XIONG Wei, XIONG Fugang, YANG Daohe, NIU Li

2020, 30(7): 1-6. doi:10.16265/j.cnki.issn1003-3033.2020.07.001

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In order to effectively reduce construction accidents for prefabricated building, a safety concept model was established by using WSR (Wuli-Shili-Renli) approach, and prefabricated components were identified as a key carrier of construction risks. Then, based on their characteristics of risk transmission, interaction between component factors in different working areas were analyzed with DEMATEL method. Finally, DEMATEL-BN model of construction risk transmission was developed, and conduction paths of risk factors in different areas were calculated. The results show that accidents can be effectively prevented based on risk causal chain by increasing systematic management of multidimensional work spaces of prefabricated construction projects, and searching for key risk factors that affect construction safety according to risk transmission path.

Research on causes of work safety accidents based on complex network theory: a case study of a district in Beijing

CHEN Wenying, LI Yongtun, SONG Zhiguang

2020, 30(7): 7-12. doi:10.16265/j.cnki.issn1003-3033.2020.07.002

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In order to reveal occurrence mechanism of work safety accidents, coupling and risk transmission features of accident causation factors were analyzed from a perspective of complex system. Then, a causation network model in a district of Beijing was constructed by complex network theory. Distribution characteristics of nodes were studied by calculating statistical indexes such as node degree and modularity, and key factors and community structure with close connections among factors in the network were identified. The results show that a few key factors play an important role in network structure, including lack of safety education and training, illegal operation and unsound construction plan, etc, and there exists obvious community structures. Safety management can be improved effectively and accident rate reduced by taking targeted control measures for key factors and high-density sub-networks to obstruct transmission of risks in the network.

Eye movement characteristics of drivers while crossing urban highways

QIAO Jian'gang, GUO Rui, LI Weidong

2020, 30(7): 13-18. doi:10.16265/j.cnki.issn1003-3033.2020.07.003

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In order to ensure safety while crossing urban highways, experiments were conducted on Highway 110 using eye tracking glasses (ETG). The road was divided into highway section, adaptation section and urban section, and drivers' 17 concerns were classified into 7 categories. Then, their fixation and saccade characteristics on different sections were studied. The results show that drivers' fixation time on points of interest range from 134.29 to 449.07 ms, and it is longer in intersections and highway openings on highway section, which accounts for 7.54% of total time. Urban section features largest number of fixations, resulting in 14.42% of total fixation time, and points of regards like guidance and vehicle driving status category fail to attract drivers' attention. Landscape has the longest average time of attention on highway section, and total frequency of saccade in urban, adaptive, and highway sections gradually decrease with an average saccade angles of 11.44, 10.72 and 10.16° respectively.

DBN-based monitoring method of vaccine transportation quality and safety risk

XIE Xiaoliang, CHU Qi, ZHANG Shujun, WEI Guo, CHENG Jiaqi

2020, 30(7): 19-26. doi:10.16265/j.cnki.issn1003-3033.2020.07.004

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In order to identify, measure and respond to two major risks of cold chain control and flow tracing, vaccine transportation process was modeled as a complex dynamic system, and by analyzing influencing factors of vaccine quality and safety risks during transportation, an evaluation index system was constructed in which vaccine procurement, storage, distribution, and loading were determined as key elements in risk chain. Secondly, a vaccine TQSRA model was developed based on DBN. 328 cases of vaccine safety incidents since 2009 were selected from OpenLaw website for statistical data learning by using GeNIe 2.0 visualization software, and an empirical study was conducted to examine validity and sensitivity of proposed TQSRA model. Finally, critical sensitive linkages of quality and safety risks during transportation were explored, and focuses of prevention and control were clarified. The results show that quality of cold chain transport vehicles and storage facilities, comprehensive quality of vaccine practitioners, and entire record and inspection of transport information are main factors affecting vaccine transportation quality and safety supervision. And TQSRA model is proved to be a stable, practical and effective assessment method.

A bibliometric analysis of research on safety climate based on CNKI database

QIU Dongyang, YANG Fuqiang, DUAN Zaipeng

2020, 30(7): 27-34. doi:10.16265/j.cnki.issn1003-3033.2020.07.005

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In order to grasp development status and frontier trends of safety climate research in China systematically, digital characteristics of 445 publications related to safety climate chosen from CNKI database from 1996 to 2019 were analyzed by bibliometric approach. The knowledge graph was drawn by using VOSviewer, and hot research areas and frontier in this field were explored. The results show that number of publications associated with safety climate research in China is increasing steadily whose development process can be divided into three stages. China University of Mining and Technology (Beijing), with a qualified research team, is the core research institution in this field. Electricity, coal mine, architecture, healthcare are main research domain of safety climate with popular topics concerning safety culture, safety behavior relationship, influence of safety performance, medical occupational climate perception, measurement method of safety climate and so on. The trend is that it is shifting from earlier topic of organizational safety culture construction to intervention mechanism which emphasizes internal factors of individuals.

Study on influence factors of formation and development of jet fire in confined space

CHEN Qing, WEI Xu, CHEN Guang, XU Liang, CHEN Peng, LIU Yang

2020, 30(7): 35-40. doi:10.16265/j.cnki.issn1003-3033.2020.07.006

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In order to prevent and control transformer oil fire and ensure normal operation of power grid, influence of transformer oil volume, core and winding volume on formation and development of jet fire was studied. Firstly, a small transformer oil combustion test platform was built, and fire forms in confined space were analyzed at generation, development and extinction stages. Secondly, changes of fire forms in each stage were analyzed after changing quantity of transformer oil. Finally, same analysis was carried out for changes of ball filling quantity. The results show that BLEVE is a key point for the biggest jet height. As quantity of transformer oil reduces, overall energy in the tank is lowered, causing a drop of flame height and delay of fire appearance at each stage. After adding 2.4 dm³ steel balls to tank, thermal resistance at bottom increases. Moreover, their protrusions or depressions provide a gasification core for bubbles in boiling process, thus decreasing liquid superheat and enhancing heat transfer. As a result, flame height is lowered significantly and time of jet fire is delayed by 52.91%

Effect of clam shell bio-filler on flame retardancy and smoke suppression properties of intumescent fire retardant coatings

LI Yaozhuang, FENG Yuwei, XU Zhisheng, YAN Long, JIA Hongyu

2020, 30(7): 41-47. doi:10.16265/j.cnki.issn1003-3033.2020.07.007

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In order to improve its flame retardancy and smoke suppression properties, an intumescent fireproof coating was prepared by using ammonium polyphosphate-pentaerythritol-melamine as an intumescent flame retardant and a clam shell bio-filler as a synergist. Then, effects of clam shell filler on flame retardancy and smoke suppression properties were analyzed by cabinet method test, big panel method, smoke density test, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and elemental analysis. The results show that addition of such filler can synergistically improve flame retardancy and smoke suppression of intumescent coatings, which will be best when added fillerg content is 2%, but will diminish for an excessive addition. Presence of clam shell filler can promote formation of more cross-linking structures during burning process and therefore enhance compactness and thermal insulation of intumescent char, thus exhibiting superior thermal stability and char-forming ability. And char residue of coatings will reach as high as 33.7% at 800 ℃ while adding 2% of filler.

Evaluation method for safety state of highway bridge structure under operation load

WANG Jianmin

2020, 30(7): 48-54. doi:10.16265/j.cnki.issn1003-3033.2020.07.008

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In order to solve difficulty in quantifying safety state evaluation of highway bridge structure under random operation load, an evaluation method of its performance status based on actual influence line was proposed. Firstly, by clarifying mathematical model of bridge structure under multi axial force and uniaxial force, an optimization analysis model for identifying actual influence line was established using LM, and it was verified theoretically with examples. Then bridge safety state and specific evaluation index were determined according to technical standards of the industry. Finally, with highway prestressed continuous beam bridge as object, actual influence line identification and safety state evaluation were carried out with proposed method. The results show that the deviation between calculated result based on identified influence line and measured one is less than 5%, and safety state can be quickly assessed by action effect amplitude of operation load.

Experimental study on synergistic gas explosion suppression by argon and ultra-fine water mist

YANG Ke, WANG Zhuang, XING Zhixiang, ZHOU Yue, JIANG Juncheng

2020, 30(7): 55-61. doi:10.16265/j.cnki.issn1003-3033.2020.07.009

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In order to improve inhibition effect of ultra-fine water mist on methane explosion, a small-scale and semi-closed methane explosion test platform was built, and experiments on methane explosion inhibition by argon and ultra-fine water mist were carried out. Through tests of single factor test surface optimization, their inhibition separately and collaboratively was tested, and their superiority in synergistic explosion suppression were analyzed from three aspects, flame characteristics, maximum explosive overpressure and average boost rate. The results show that synergistic inhibition effect of argon gas and ultra-fine water mist on methane explosion is remarkable. With increase of theformer's volume fraction and the latter's amount, time taken for flame to rush out of pipes gradually lengthens, and maximum explosion overpressure and average boost rate gradually decrease. Best inhibition effect is achieved when argon is at 10% and ultra-fine water mist spray at 4.2 mL. And maximum explosion overpressure of methane decrease by 6.15 and 2.68 kPa respectively compared with the cases of argon gas and ultra-fine water mist alone, indicating that they have a synergistic effect in inhibiting methane explosion.

Influence of electrostatic field on coal gas diffusion characteristics in coal

LEI Dongji, MA Tao, MENG Hui, XUE Qunshan

2020, 30(7): 62-68. doi:10.16265/j.cnki.issn1003-3033.2020.07.010

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In order to explore influence of electrostatic field on gas diffusion characteristics in coal, a gas desorption and diffusion test system was independently designed, and desorption and diffusion volume of coals were measured under electric field intensity of 0, 40, 120 and 240 kV/m respectively with samples of different metamorphism selected from Guhanshan Mine, Hebi No. 6 Mine, Pingdingshan No. 8 Mine and Yimagengcun Mine. Then, their diffusion coefficient was calculated by using classical single hole diffusion model. The results show that diffusion coefficient of coal samples increases first and then decreases in a parabolic form along with increase of applied electric field strength. It reaches the maximum when characteristic dominant electric field strength is 40 kV/m, but will decrease while under other electric field intensities. Based on comparison of diffusion characteristics of these samples under electric field strength, it is found that coefficient of fat coal in Pingdingshan Mine is the largest while lignite in Yima Mine is the smallest. Reasons for diffusion characteristics variance under electrostatic field are that induced polarization of coal and gas molecules changes adsorption potential well depth on coal surface, and also electric field can cause volume percentage and specific surface area of micro pores in coal to increase (decrease).

Analysis on damage characteristics and energy dissipation of rock with a single hole under cyclic impact loads

DAI Bing, LUO Xinyao, SHAN Qiwei, CHEN Ying, LIU Yong

2020, 30(7): 69-77. doi:10.16265/j.cnki.issn1003-3033.2020.07.011

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In order to explore influence of external load on multiple perturbations of surrounding rock during tunnel excavation, cyclic impact load tests of rock with a single hole were carried out by using Split Hopkinson Pressure Bar (SHPB) device under different impact loads (0.6, 0.7, 0.8 MPa) and impact methods (impact pressure of Equal-amplitude and Unequal-amplitude). Then, dynamic characteristics, damage characteristics, energy dissipation and failure modes of these rock specimens under impact loads were analyzed. The results show that based on one-dimensional stress wave theory and interface continuity conditions, an improved damage calculation formula is obtained suitable for rock specimen with a vertical hole which affects changing trend of rock stress-strain curves, especially after several shocks. Damage accumulation of granite increases in a power function along with increase of average strain rate, and shows a good regularity with increase of impact loads. Moreover, cumulative specific energy absorption value increases gradually with cyclic impact, and failure mode has undergone transformation from transverse tensile failure to transverse tensile failure -axial splitting failure and axial splitting failure.

Evaluation method of defect in pipe girth considering specific material

WANG Xu, SHUAI Jian, WANG Yu, LUO Yufei, SHAN Ke

2020, 30(7): 78-84. doi:10.16265/j.cnki.issn1003-3033.2020.07.012

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In order to evaluate the applicability of the evaluation method of pipeline girth weld defects, the Ramberg-Osgood model parameters were obtained by processing the data of tensile test for different grades of pipeline steel. The failure assessment curves of pipeline steels with different grades based on material properties was established. The stress-strain curves of the girth welds were drawn by the digital image correlation(DIC)technique applying.The failure assessment curves evaluating the girth weld defected pipelines was formed. The research shows that, when the load ratio is less than 0.7, the failure assessment curves of pipeline steels of different grades are basically the same with load ratio increasing.When load ratio is between 0.7 and 1.0, the acceptable zone of failure assessment curve of high grade pipeline steel is larger. In other words, the improvement of pipeline steel grade can promote the safety margin of defected pipelines. The failure assessment curves based on test data can better reflect the performance difference of the material, which should be prior used in the assessment of low matched welded joint of pipeline.

Research on safety assessment of building structure for regeneration project

LI Wenlong, LI Huimin, WANG Sunmeng, LIU Yijun, PEI Xingwang

2020, 30(7): 85-92. doi:10.16265/j.cnki.issn1003-3033.2020.07.013

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In order to fully grasp safety status of building structure for regeneration projects and ensure its safe and reliable use, a safety assessment index system was constructed according to characteristics of regeneration projects. Then, a safety assessment model was established by adopting matter-element extension method, correlation function was calculated, and index weight was determined by combination weighting method. Finally, safety level of building structure was obtained, and a real engineering project was employed to verify this model. The results show that this model can determine structure safety level which is basically consistent with actual situation, thus verifying its effectiveness in reflecting safety status of building structure for regeneration projects.

Thermal decomposition characteristics and impact sensitivity of anhydrous and wet benzoyl peroxide

LI Shiran, WU Wenqian, CHEN Liping, ZHAO Xiaoqiao, CHEN Wanghua

2020, 30(7): 93-100. doi:10.16265/j.cnki.issn1003-3033.2020.07.014

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In order to study thermal decomposition characteristics, impact sensitivity of anhydrous and wet BPO, and discuss their relationship. Firstly, DSC tests and impact sensitivity tests at different ambient temperatures were carried. Then, based on the results of a series of dynamic and isothermal DSC tests, "autocatalytic + n order" model and "autocatalytic + autocatalytic + n order" model were established for decomposition under solid phase and melting process, and the hot spot temperatures of the above two conditions were predicted to be 244.7 and 277.9 ℃, respectively. Finally, the relationship between the characteristic drop height H₅₀ and the ambient temperature θ₀ was obtained according to the results of impact sensitivity tests. The results show that impact sensitivity of wet BPO is significantly lower than anhydrous BPO at 40 and 50 ℃, but the wet BPO is more sensitive to temperature at 40-70 ℃. Therefore, it is necessary to control temperature during transportation of wet BPO to reduce risk of explosion accidents caused by impaction.

Research on safety range of risers with volume defects

FANG Yong, XIA Chengyu, HE Yuhang, WANG Xudong, CHEN Kun, HUANG Zhuang

2020, 30(7): 101-106. doi:10.16265/j.cnki.issn1003-3033.2020.07.015

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In order to ensure safe operation of risers at sea, it is necessary to evaluate safety of those with defects so as to avoid crushing, leakage and fracture accidents. Based on elastic-plastic linear hardening model and Von Mises yield criterion, a three dimensional finite element calculation model of risers with volume defects was constructed considering influence of internal pressure load from stretch bending and geometric defect size. Then, mechanical characteristics of safety working range of these defected risers were analyzed under combined load, and their safety was assessed. The results show that the greater defect depth, the more likely these risers will yield, and along with increase of defect depth, its safety range decreases. Heavier internal pressure load would cause an obvious decrease in safety range which, however, will be slightly impacted by defect depth in case of lighter load. Moreover, when bending load is too heavy, limit axial load in riser safety zone decreases remarkably while limit internal load does not change much.

Preparation of modified β-CD and flame retardancy of EP

HAN Ji, SHAN Xueying, SHAO Hui, GUO Hui, LI Jinchun

2020, 30(7): 107-113. doi:10.16265/j.cnki.issn1003-3033.2020.07.016

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In order to develop single molecule flame retardant to improve flame retardancy of EP, phosphate diacid chloride (SPDPC) was prepared by using pentaerythritol (PER) and phosphorus oxychloride (POCl₃). Then different amounts of SPDPC was applied to modify β-CD. Finally, EP/mβ-CD composite was made by adding modified β-CD (mβ-CD) into EP (amount of addition was 25% based on EP quality). The results show that the mβ-CD prepared with 1∶8 molar ratio of β-CD to SPDPC has good compatibility in EP matrix, and it increases amount of char residue of EP in nitrogen atmosphere to 26.7% from 15.3%. EP oxygen index also rises from 19.5% to 28.2%. Vertical combustion of EP/mβ-CD composite reaches V-0 level, and its total heat release (THR) and peak of heat release rate (PHRR) are reduced by 50.4% and 47.9% respectively comparing to pure EP while peak of smoke production rate (PSPR) and total smoke production (TSP) reduced by 12.5% and 52.8%. Moreover, such composite with above mβ-CD could form a stronger char layer.

Research on stacking angle of coal particles and parameter calibration on EDEM

WEN Xiaojiang, FANG Feifei, LIU Yingke, LI Jian

2020, 30(7): 114-119. doi:10.16265/j.cnki.issn1003-3033.2020.07.017

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In order to make numerical simulation results on EDEM in better agreement with flow characteristics of coal particles, orthogonal experiments of particle-particle contact parameters calibration were designed and a calibration method was proposed based on stacking angle of particles. Then, optimal level of parameters and significance of their impact on stacking angle were analyzed by utilizing range analysis and variance analysis methods. The results show that stacking angle of 550-600 μm coal particles is 33.33°, and rolling friction coefficient induces most significant influence on it, followed by coefficient of static friction and that of restitution. Moreover, when coefficient of restitution, static friction and rolling frction is 0.3, 0.5 and 0.1 respectively on EDEM, stacking angle of coal particles will be 30.13° with a relative error of merely 0.66%, indicating that is an optimal contact parameter combination.

Research on pneumatic water mist flow field based on PIV

LIU Chenghui, CHEN Xianfeng, ZHANG Wei, XU Lexian, ZHAO Qi, HUANG Chuyuan

2020, 30(7): 120-126. doi:10.16265/j.cnki.issn1003-3033.2020.07.018

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In order to explore morphological changes of pneumatic water mist flow field under different gas pressures, GLR of pneumatic two-fluid water mist nozzles were measured by using mass flow controllers and PIV technology. Then, features of flow field were analyzed under gas driving pressure between 0.1-0.3 MPa. The results show that under nitrogen pressure of 0.1-0.4 MPa, dimensionless GLR value of water mist nozzles presents a linear growth relationship with nitrogen pressure, and GLR exerts impacts on characteristics of two-phase flow inside the nozzle, liquid breakdown mechanism, droplet dynamics and final droplet size distribution. When gas pressure increases from 0.1 MPa to 0.3 MPa, average atomization cone angle shrinks from 55.02° to 27°, and main velocity range of water mist particles rises from 0-5 m/s to 0-12 m/s. Average vorticity at vortex increases from 166.502 81 s^-1 to 671.191 26 s^-1, and vortex structure of particle air mass shows counterclockwise rotation.

Simulation and optimization of road network evacuation in communities for elderly people in Northeast China

HUANG Lidi, XU Xinxin, LIU Ying, ZHANG Qi, LUO Kaizhou, DONG Zhilong

2020, 30(7): 127-132. doi:10.16265/j.cnki.issn1003-3033.2020.07.019

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In order to address vulnerability of communities for the elderly and improve their evacuation efficiency, typical road space patterns were statistically analyzed with 814 communities in Northeast China extracted by random sampling as research object, and concept of effective evacuation road network density was proposed. Secondly, an evacuation simulation model was constructed, and road network shapes of the elderly communities were simulated by adopting pathfinder software. Finally, a community road network optimization strategy that adapted to evacuation behaviors of elderly people was put forward and verified. The results show that there is a negative correlation between evacuation efficiency and population aging. Square road network has higher efficiency, and as network density increases, impact of aging on evacuation time decreases by 37.3%. It is also found that point-shaped congestion is prone to occur at entrances and exits of blocks and turning points of roads while range of band-shaped congestion is positively correlated with block scale.

Static identification experiments and safety assessment on colour vision of visually impaired population

WANG Qingzhou, LUO Te, FAN Xin, LU Xinzhen

2020, 30(7): 133-138. doi:10.16265/j.cnki.issn1003-3033.2020.07.020

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In order to assess influencing factors on people with color weakness to correctly recognize signal lights, static recognition tests of red, yellow and green semaphore color vision were conducted on patients with weakness on these three colors. Relationship between light intensity, visual recognition distance and recognition error rate was established. Then, proportion of hazard orientation in false recognition results was proposed as an evaluation criterion for severity of signal lamp misjudgment. The results show that illumination intensity and visual distance have a significant impact on visual recognition of color-impaired people whose recognition error rate reaches its maximum at 12 noon and is always higher in the morning than afternoon. And the rate increases continuously along with increase of visual recognition distance and that for people with red and green color weakness at 90-meter distance can reach as high as 60%. Visual results of green weak patients is the best but has highest proportion of hazard orientation with potential risks that can not be ignored. Visual correctness of color-weak group is very sensitive to influence of illumination intensity and visual distance, so attention should be paid to safety of color-weak group driving motor vehicles.

An improved crowd evacuation model for a multi-exit environment

WEI Juan, GUO Yangyong, YOU Lei, LI Zhongyu, TANG Zhihai, HU Zhouyi

2020, 30(7): 139-145. doi:10.16265/j.cnki.issn1003-3033.2020.07.021

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In order to effectively improve simulation accuracy of crowd evacuation in a multi-exit environment, a novel crowd evacuation model was established based on social force model and particle pigeons algorithm. Self-driving direction that affected pedestrian movement in traditional social force model was improved by obtaining moving direction of pedestrian through field model. Then, an evacuation optimization model for a multi-exit environment was established with consideration to field values, average velocity and congestion degree, and it was solved quickly by employing particle pigeons algorithm. The results show that as crowd density increases, average evacuation velocity decreases first and then increases slowly. When density is small, the larger field weight value is, the less time evacuation takes.

Correlation and risk factors analysis of traffic crash at intersections on rural highways

ZHAO Dan, MA Sheqiang, ZHANG Yumeng, HAN Fengchun

2020, 30(7): 146-151. doi:10.16265/j.cnki.issn1003-3033.2020.07.022

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In order to reduce crash risks at intersections on rural highways, with environment, highway, facilities, vehicle types and illegal behaviors extracted as independent variables, pattern and severity of crashes taken as dependent variables, a bivariate Probit model was established. Then, intrinsic correlation of these two variables was analyzed and significant influencing factors were identified. The results show that there is a negative correlation between crash pattern and severity, and death rate of single-vehicle accidents is higher. The better road alignment is and the more well-equipped isolation and control facilities are, the lower crash severity is, while the bigger vehicles are, the more serious crash becomes. Besides, traffic offence increases probability of fatal single-vehicle accidents. Safety of intersections on rural highway can by improved by measures such as installing safety facilities, implementing speed-limit management at intersections of highways with significant grade difference, strengthening security control of oversize vehicles and motorcycles, and increasing penalties for driving without license.

Relevance study between unsafe behaviors of passengers and metro accidents based on fsQCA

WANG Rubing, WAN Xin, MAO Peng, LI Dezhi, WANG Xiang

2020, 30(7): 152-158. doi:10.16265/j.cnki.issn1003-3033.2020.07.023

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In order to effectively prevent passenger-caused metro operation accidents, with 40 typical metro operation accidents as research object, their inner mechanism and formation path were explored by employing fsQCA approach. Then, these paths, according to twelve condition configurations obtained,were classified into three types, that is weak safety awareness, lack of supervision and influence by others. The results show that avoiding passengers' intrusion into metro gauges emotionally is vital to prevent weak safety awarenss kind of accidents. Strengthening supervision of non-gauge areas, such as carriages and platforms, can effectively block path of lack of supervision accidents. Moreover, to cut off that of influence by others accidents, measures like advanced control and participatory control of passengers should be adopted to effectively expand positive influence from others.

Stability analysis of tunnel surrounding rock considering influence of damage and dilatancy

GAO Zhaoning, CHEN Dengguo, SUN Zhenchuan, YANG Yandong, LI Shunshun

2020, 30(7): 159-165. doi:10.16265/j.cnki.issn1003-3033.2020.07.024

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In order to solve supporting problems of surrounding rock after tunnel excavation under complex geological structure, surrounding rock was divided into elastic zone and plastic zone according to characteristics of its stress distribution curves. Then, an elastoplastic damage constitutive model was developed following Drucker Prager yield criterion, and its mechanical performance degradation caused from damages and dilatancy under unloading were analyzed. Finally, an analytical solution of elastic-plastic zone was deduced. The results show that support resistance and plastic areas' shift increase obviously as injury and dilatancy degree intensifies. The bigger radius of plastic zone is, influence on surrounding rock stability is deeper within a certain range since tangential stress peak is far away from tunnel wall. And along with increase of intermediate principal stress coefficient, support resistance decreases, which is more favorable to optimization of support parameters with an consideration to the former.

Prediction model of rockburst intensity classification based on RF-AHP-Cloud model

TIAN Rui, MENG Haidong, CHEN Shijiang, WANG Chuangye, SHI Lei

2020, 30(7): 166-172. doi:10.16265/j.cnki.issn1003-3033.2020.07.025

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In order to accurately and reliably predict rockburst disasters, AHP was optimized based on importance of analysis index of RF, and an RF-AHP weight calculation method was constructed. Then, a prediction model of rockburst intensity classification based on RF-AHP-Cloud model was established. Finally, through literature survey, a database containing 301 groups of engineering instances was established as sample data for rockburst prediction, and prediction results of 25 sets of samples were analyzed. The results show that the proposed model has an prediction accuracy of more than 88%, and it can determine rockburst intensity grade of samples. And rationality of RF-AHP index weight calculation method as core of prediction model is also verified.

Emergency supplies distribution model considering psychological impact of supplies damage

SONG Yinghua, SONG Yinghui, LI Chaoxin, WANG Zhe

2020, 30(7): 173-179. doi:10.16265/j.cnki.issn1003-3033.2020.07.026

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In order to improve efficiency of emergency rescue and benefit of supplies distribution, according to damage situation of relief items after natural disasters, a tolerance function of impacted populations to supplies damage was proposed to quantify people‘s psychology based on damage rate's top and bottom psychological influence limits and its impact on supplies distribution. Then, an optimization model of dynamic emergency logistics distribution, which considered multiple period, items and scenarios of disaster evolution, was established to minimize total operational costs and maximize effective emergency supplies satisfaction rate weighted by expected intolerable damage degree of victims. Finally, a numerical example based on data of Sichuan earthquake zone was solved by Matlab, and effectiveness of the model was demonstrated by comparing proposed schemes. The results indicate that introduction of tolerance function to supplies damage can optimize total costs while securing supplies for affected areas where victims have higher levels of urgent relief demand.

Mechanical properties of elastic aerogel spherules for fire-fighting clothes filling

YANG Fan, LU Yi, LIU Yilun, SHI Shiliang, WANG Jinpeng, LI Songhui

2020, 30(7): 180-185. doi:10.16265/j.cnki.issn1003-3033.2020.07.027

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In order to protect firemen from injuries in rescue activities, elastic aerogel spherules for thermal insulation lining filling of fire-fighting clothes were prepared with SiO₂aerogel powder, ammonia free latex and water as raw materials. Firstly, their mechanical conduction mechanism was investigated. Then, macro morphology, microstructure characterization and specific surface area were measured. Finally, their mechanical properties were tested at different pressures. The results show that microstructure of elastic aerogel spherules was more compact than that of aerogel powder. When pressure of a single spherule reaches 2 kN, samples will be cracked partially, and forces transmitted decrease from circle 1 to 5, especially evident at 4^th cycle. But spherules will not crack if they take pressure of 15 kN as a whole. It is found that insulation lining of fire-fighting clothes should be made up of a center spherule with regular hexagon and 1-3 circles of elastic aerogel spherules.

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