Advance in Tunnel Fire Research

A special issue of Fire (ISSN 2571-6255). This special issue belongs to the section "Fire Risk Assessment and Safety Management in Buildings and Urban Spaces".

Deadline for manuscript submissions: closed (30 September 2024) | Viewed by 21851

Special Issue Editors

Faculty of Engineering, China University of Geosciences, Wuhan 430074, China
Interests: fire in underground spaces; pool fire; tunnel fire; compartment fire; cable fire and fire spread; oil fire; fire dynamics
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Guest Editor
Belfast School of Architecture and the Built Environment, Ulster University, Newtownabbey, Northern Ireland, BT37 0QB, UK
Interests: enclosure and façade fire dynamics; material flammability and fire testing; computational fluid dynamics (CFD) modelling of flames and fires; modelling of human behavior and evacuation; numerical analysis of heat transfer and pyrolysis of solids; quantitative risk analysis
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School of Resource and Environmental Engineering, Wuhan University of Science and Technology, Wuhan 430081, China
Interests: fire dynamics; tunnel/metro fire safety; smoke control for buildings

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Guest Editor
School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006, China
Interests: compartment fire dynamics, ceiling jet flow, fire and pollutant transportation under wind, combustion characteristics of jet flame; emergency rescue drill system based on virtual reality
Special Issues, Collections and Topics in MDPI journals
Pittsburgh Mining Research Division, National Institute for Occupational Safety and Health, Pittsburgh, PA 15236, USA
Interests: tunnel fire; smoke transport; flame shape; battery thermal safety

Special Issue Information

Dear Colleagues,

All kinds of tunnels are emerging all over the world due to the modern architectural trends. Although the development of tunnel brings convenience to people's life, tunnel fire often leads to tunnel structure damage and a large number of casualties. Currently in recent years, the diversity of tunnel fires have brought up advanced and unique challenges to tunnel fire safety, making the relevant research in general necessary.

This Special Issue aims to highlight the original findings regarding to the tunnel fire, and the potential perspectives for future investigations are also encouraged. In this Special Issue, original research articles and reviews are welcome. Research areas may include (but are not limited to) the following:

  • Fire and smoke transport mechanism
  • Thermal effect on structural safety
  • Smoke control strategy
  • Fire detection and suppression technology
  • Human evacuation procedures
  • The application of fire retardant materials in tunnels
  • The combination of tunnel fire with AI technology

We look forward to receiving your contributions.

Dr. Kaihua Lu
Dr. Jianping Zhang
Dr. Jie Wang
Dr. Xiaochun Zhang
Dr. Wei Tang
Guest Editors

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Keywords

  • tunnel fire dynamic
  • structural safety
  • smoke transport and control
  • fire detection and suppression
  • human evacuation
  • AI technology
  • tunnel materials

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Published Papers (12 papers)

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Research

19 pages, 7217 KiB  
Article
A Study on the Influence of Mobile Fans on the Smoke Spreading Characteristics of Tunnel Fires
by Weigeng Chen, Yuhang Liu, Zhiyuan Cao, Ping Zhou, Changman Chen, Zhonglun Wu, Ze Fang, Lei Yang and Xiaoping Liu
Fire 2024, 7(11), 397; https://doi.org/10.3390/fire7110397 - 31 Oct 2024
Viewed by 516
Abstract
Mobile fans, as flexible and convenient new longitudinal ventilation and smoke extraction equipment for tunnels, demonstrate more significant effectiveness in an emergency response to tunnel fires compared to traditional smoke extraction methods. This study employs computational fluid dynamics simulation methods, selecting two fire [...] Read more.
Mobile fans, as flexible and convenient new longitudinal ventilation and smoke extraction equipment for tunnels, demonstrate more significant effectiveness in an emergency response to tunnel fires compared to traditional smoke extraction methods. This study employs computational fluid dynamics simulation methods, selecting two fire scenarios to investigate the effects of fan inclined angles and fan airflow volumes on the longitudinal temperature distribution and smoke back-layering length in tunnels. The results indicate that when using mobile fans for longitudinal ventilation in tunnels, at a lower fan airflow volume, the temperature distribution along the longitudinal axis is nearly symmetrical. The fire source and the fan installed in the upstream are within a certain range, and it is more effective to use the horizontal angle for longitudinal ventilation. As the fan airflow volume increases, the back-layering length significantly decreases (210,000 m3/h < V < 270,000 m3/h). However, as the fan flow volume continues to increase (270,000 m3/h < V < 300,000 m3/h), the reduction in the back-layering length becomes less pronounced, the smoke spread distance of the latter is only 11% of that of the former. Therefore, selecting appropriate fan airflow volumes and fan inclined angles them can effectively enhance the performance of tunnel smoke extraction systems. Moreover, by comparing with traditional fans, we find that mobile fans provide an alternative effective strategy during firefighting by allowing adjustments in distance from the fire source and fan inclination angles, enhancing fire suppression effectiveness while reducing energy losses. The research findings can serve as a reference for tunnel fire prevention design. Full article
(This article belongs to the Special Issue Advance in Tunnel Fire Research)
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20 pages, 6607 KiB  
Article
Numerical Study on the Influence of the Slope Composition of the Asymmetric V-Shaped Tunnel on Smoke Spread in Tunnel Fire
by Dengkai Tu, Junmei Li, Yanfeng Li and Desheng Xu
Fire 2024, 7(10), 363; https://doi.org/10.3390/fire7100363 - 11 Oct 2024
Viewed by 641
Abstract
Asymmetrical V-shaped tunnels often appear in tunnels crossing the river or urban underground road tunnels. The smoke flow inside is affected by a lot of factors. A full understanding of the smoke flow in this kind of tunnel is the basis of the [...] Read more.
Asymmetrical V-shaped tunnels often appear in tunnels crossing the river or urban underground road tunnels. The smoke flow inside is affected by a lot of factors. A full understanding of the smoke flow in this kind of tunnel is the basis of the smoke control. In this study, the effects of slope composition and fire heat release rate (HRR) on the longitudinal induced airflow velocity, the smoke back-layering length at the small slope side, and the maximum ceiling temperature were studied by the numerical method. The results show that when the fire occurs at the slope change point of the V-shaped tunnel, the maximum ceiling temperature decreases with the increase in the slope of the large-slope side tunnel. The longitudinally induced velocity is primarily related to the slope of the large-slope side tunnel and the fire HRR. When the slope difference between the side tunnels or the slope of the large-slope side tunnel is large, the smoke in the small-slope side tunnel flows back toward the fire source after reaching its maximum dispersion distance and then reaches a quasi-steady state. The smoke back-layering length is mainly affected by the slope and length of the large-slope side tunnel. When the slope of the large-slope side tunnel is 9%, the induced airflow velocity from the small-slope side can prevent the spread of smoke. The empirical models of the smoke back-layering length and the longitudinal induced airflow velocity in the small-slope side tunnel are drawn, respectively, by the theoretical analysis and the numerical results. This study can provide technical support for the design and operation of smoke control systems in V-shaped tunnels. Full article
(This article belongs to the Special Issue Advance in Tunnel Fire Research)
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17 pages, 3388 KiB  
Article
Simulation of Fire Evacuation in a Naturally Ventilated Bifurcated Tunnel
by Jianhong Chen, Zekun Hu and Shan Yang
Fire 2024, 7(6), 202; https://doi.org/10.3390/fire7060202 - 16 Jun 2024
Cited by 1 | Viewed by 863
Abstract
The natural wind velocities in tunnels under different natural conditions are distinct, and the longitudinal ventilation velocity significantly impacts the evacuation environment. This paper examines the evacuation conditions and strategies under varying wind velocities in bifurcated tunnels. Using Fire Dynamics Simulator (FDS) and [...] Read more.
The natural wind velocities in tunnels under different natural conditions are distinct, and the longitudinal ventilation velocity significantly impacts the evacuation environment. This paper examines the evacuation conditions and strategies under varying wind velocities in bifurcated tunnels. Using Fire Dynamics Simulator (FDS) and Pathfinder software, the fire development and evacuation of three distinct longitudinal positions in a bifurcated tunnel are simulated. The simulation results demonstrate that the evacuation conditions for disparate fire sources at varying wind velocities are markedly disparate. In consideration of the construction cost and the maximization of evacuation capacity, the width of the evacuation doors at the three locations should be set to 2 m, 1.5 m, and 1.5 m, respectively. Furthermore, an analysis of the safety of individual personnel through Fractional Effective Dose (FED) revealed that directing evacuees towards the upstream of the fire after the fire is detected can significantly reduce individual personnel injuries while ensuring the overall success of the evacuation. Full article
(This article belongs to the Special Issue Advance in Tunnel Fire Research)
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34 pages, 12253 KiB  
Article
CFD Simulation to Assess the Effects of Asphalt Pavement Combustion on User Safety in the Event of a Fire in Road Tunnels
by Ciro Caliendo and Isidoro Russo
Fire 2024, 7(6), 195; https://doi.org/10.3390/fire7060195 - 12 Jun 2024
Cited by 2 | Viewed by 1015
Abstract
This paper presents a specific 3D computational fluid dynamics model to quantify the effects of the combustion of asphalt road pavement on user safety in the event of a fire in a bi-directional road tunnel. Since the consequences on tunnel users and/or rescue [...] Read more.
This paper presents a specific 3D computational fluid dynamics model to quantify the effects of the combustion of asphalt road pavement on user safety in the event of a fire in a bi-directional road tunnel. Since the consequences on tunnel users and/or rescue teams might be affected not only by the tunnel geometry but also by the type of ventilation and traffic flow, the environmental conditions caused by the fire in the tunnel under natural or longitudinal mechanical ventilation, as well as congested traffic conditions, were more especially investigated. The simulation results showed that the combustion of the asphalt pavement in the event of a 100 MW fire, compared to the case of a non-combustible road pavement, caused (i) an increase in smoke concentrations; (ii) a greater number of users exposed to the risk of incapacity to escape from the tunnel; (iii) a more difficult situation for the firefighters entering the tunnel upstream of the fire source in the case of natural ventilation; (iv) a higher probability of the domino effect for vehicles queued downstream of the fire when the tunnel is mechanically ventilated. Full article
(This article belongs to the Special Issue Advance in Tunnel Fire Research)
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21 pages, 5398 KiB  
Article
Evaluating the Ceiling Gas Temperature in a Branched Tunnel Fire with a Sloped Mainline Region under Natural Ventilation
by Ning Lu, Xiaolin Yao, Jinming Yang and Youbo Huang
Fire 2024, 7(5), 152; https://doi.org/10.3390/fire7050152 - 24 Apr 2024
Viewed by 1222
Abstract
The effect of the mainline slope on the ceiling temperature profile in a branched tunnel has not been clarified nor included in existing models. Thus, in this paper, the numerical code was employed to investigate the induced airflow velocity and gas temperature beneath [...] Read more.
The effect of the mainline slope on the ceiling temperature profile in a branched tunnel has not been clarified nor included in existing models. Thus, in this paper, the numerical code was employed to investigate the induced airflow velocity and gas temperature beneath the ceiling in a branch tunnel with a sloped upstream mainline. The mainline slope varied from 1% to 7%, with an interval of 1%. Five fire power of 3 MW, 5 MW, 10 MW, 15 MW, and 20 MW are employed on each slope. The airflow velocity and the longitudinal temperature in the mainline tunnel are measured and analyzed. Results show that the stack effect obviously occurred, which caused longitudinal velocity to prevent the smoke reverse flow in the mainline. The induced airflow velocity in the upstream inclined mainline is higher with increasing slope, and the dimensionless velocity is normalized well by the proposed expression. The maximum ceiling temperature is independent of the mainline slope and correlated well by Q*2/3, but the effect of the mainline slope on temperature longitudinal decay is worth considering. Finally, a normalized expression for longitudinal temperature decay in an inclined mainline is proposed by taking the fire power and mainline slope into account. Full article
(This article belongs to the Special Issue Advance in Tunnel Fire Research)
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13 pages, 2780 KiB  
Article
A Study on the Maximum Temperature of a Ceiling Jet of Asymmetric Dual Strong Plumes in a Naturally Ventilated Tunnel
by Shenghao Zhang and Na Meng
Fire 2024, 7(4), 110; https://doi.org/10.3390/fire7040110 - 26 Mar 2024
Cited by 1 | Viewed by 1236
Abstract
This paper explores the temperature distribution (TD) and maximum temperature (MT) below the ceiling induced by the ceiling jet of an asymmetric dual fire sources in a naturally ventilated tunnel. Considering strong plumes, this study investigates the effects of fire size and spacing [...] Read more.
This paper explores the temperature distribution (TD) and maximum temperature (MT) below the ceiling induced by the ceiling jet of an asymmetric dual fire sources in a naturally ventilated tunnel. Considering strong plumes, this study investigates the effects of fire size and spacing of asymmetric dual fire sources on TD and MT. With the same power of fire source, when the size of one of the fire sources increases, the corresponding maximum temperature beneath ceiling decreases. Additionally, the temperature peak below the ceiling shifts from one to two, and the peak temperature of the larger fire source is lower compared to that of smaller one. When the fire sources distance increases, the maximum temperature initially decreases and then increases. Beyond a certain distance, the maximum temperature no longer changes with increasing distance. In this study, we investigated the effect of fire source size and spacing on the MT of the tunnel ceiling for asymmetric dual fire sources. A new model for predicting the MT underneath the tunnel ceiling was developed, taking into account the factors as fire spacing and fire size. The model is able to make effective predictions of the simulation results. Full article
(This article belongs to the Special Issue Advance in Tunnel Fire Research)
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14 pages, 4732 KiB  
Article
Temperature Distribution Curve Analysis on Concrete through LS-DYNA
by Topendra Oli, Dongsoo Ha, Taejin Jang, Cheolwoo Park, Gihyun Kim and Seungwon Kim
Fire 2024, 7(1), 15; https://doi.org/10.3390/fire7010015 - 29 Dec 2023
Viewed by 2364
Abstract
The development and importance of tunnels are increasing worldwide, and countries like Korea, where about 70% of the total land is covered with mountain regions, need more tunnel constructions to connect different routes of roads for safe and efficient transport. This study applied [...] Read more.
The development and importance of tunnels are increasing worldwide, and countries like Korea, where about 70% of the total land is covered with mountain regions, need more tunnel constructions to connect different routes of roads for safe and efficient transport. This study applied fire to the 200 mm × 200 mm × 200 mm concrete specimens, similar to the Rijkswaterstaat (RWS) fire, through an electric furnace. Thermocouples were placed inside the specimens to analyze the temperature during the occurrence of fire. Experimental and simulation thermal analysis during the occurrence of fire was analyzed. The experimental temperature at different depths agreed with the simulation results. Different international fire curves were applied to study the temperature inside the concrete through simulation by LS-DYNA. Concrete with different thicknesses of fireproof board was analyzed through simulation, and using fireproof board reduces the inside temperature during fire occurrence. Among the studied international fire curves, modified hydrocarbon fire curves had a high-temperature effect on concrete. Full article
(This article belongs to the Special Issue Advance in Tunnel Fire Research)
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21 pages, 19615 KiB  
Article
Fire Hazard Analysis on Different Fire Source Locations in Multi-Segment Converging Tunnel with Structural Beams
by Lixin Wei, Honghui Tang, Jiaming Zhao, Shiyi Chen, Yiqiang Xie, Shilin Feng, Zhisheng Xu and Zihan Yu
Fire 2023, 6(11), 444; https://doi.org/10.3390/fire6110444 - 18 Nov 2023
Cited by 1 | Viewed by 1966
Abstract
To investigate the fire risk in a complex tunnel with varying cross-sections, sloped structures, and dense upper cover beams, this study considered four fire source positions: the immersed tube section, confluence section, highway auxiliary road section, and four-lane sections of the main line. [...] Read more.
To investigate the fire risk in a complex tunnel with varying cross-sections, sloped structures, and dense upper cover beams, this study considered four fire source positions: the immersed tube section, confluence section, highway auxiliary road section, and four-lane sections of the main line. It also considered four beam spacings: 1 m, 1.8 m, 3.6 m, and 7.2 m. The Fire Dynamics Simulation Software FDS was utilized to create a comprehensive tunnel model. The analysis focused on temperature and visibility changes at a 2 m height under a 20 MW fire condition for different fire source positions. These changes were then compared with critical danger values to assess the safety of evacuating personnel within the tunnel. Subsequently, this study proposed corresponding emergency rescue strategies. The findings indicated that when the beam grid spacing exceeded 3.6 m, the upper dense beam gap showed a robust smoke storage capacity, leading to a reduced distance of high-temperature smoke spread. However, this increased smoke storage disrupted the stability of the smoke layer, resulting in a heightened smoke thickness. The location of the ventilation vent at the entrance of the immersed tunnel section caused a non-uniform ventilation flow under the girder, deflecting the smoke front towards the unventilated side and decreasing visibility in the road auxiliary area. In comparison to scenarios without a beam lattice, the presence of a beam lattice in the tunnel amplified fire hazards. When the beam lattice spacing was 3.6 m or greater, the extent of the hazardous environment, which is unfavorable for personnel evacuation, expanded. With the exception of the scenario where the fire source was located in the highway auxiliary roadway, all other conditions surpassed 150 m, which is roughly one-third of the tunnel length. Consequently, more targeted strategies are necessary for effective evacuation and rescue efforts. Full article
(This article belongs to the Special Issue Advance in Tunnel Fire Research)
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22 pages, 5423 KiB  
Article
Assessment Method Integrating Visibility and Toxic Gas for Road Tunnel Fires Using 2D Maps for Identifying Risks in the Smoke Environment
by Huei-Ru Hsieh, Hung-Chieh Chung, Nobuyoshi Kawabata, Miho Seike, Masato Hasegawa, Shen-Wen Chien and Tzu-Sheng Shen
Fire 2023, 6(4), 173; https://doi.org/10.3390/fire6040173 - 21 Apr 2023
Cited by 1 | Viewed by 2059
Abstract
This study proposes an assessment method to quantify the risks of the smoke environment for road tunnel fire safety based on previous studies. The assessment method integrates visibility and toxic gases to address the hazards of smoke distribution more comprehensively. Considering that the [...] Read more.
This study proposes an assessment method to quantify the risks of the smoke environment for road tunnel fire safety based on previous studies. The assessment method integrates visibility and toxic gases to address the hazards of smoke distribution more comprehensively. Considering that the hazards of visibility reduction and toxic gases for tunnel users vary with exposure time and location in a fire event, the smoke environment (SE) levels are defined as a function of longitudinal location and time. The SE levels simplify smoke distribution as calculated from 3D computational fluid dynamics (CFDs). For easily identifying SE risks, SE levels are illustrated on a 2D map to analyze the potential hazard by quantifying specific areas and times of smoke exposure. To demonstrate the applicability of the assessment method of this study, cases are carried out using CFD simulation to investigate the risks associated with tunnel fires with various tunnel cross-section types, longitudinal velocities, and gradients. In the analysis of the SE level in different cross-section types and longitudinal velocities under the condition of no vehicle, a velocity of 0.9–1.1 m/s can maintain a less serious SE level both upstream and downstream in a horizontal rectangular tunnel, and 0.3–0.5 m/s in a horizontal horseshoe-shaped tunnel. Both rectangular and horseshoe-shaped tunnels reveal an obvious rise within 10–15 min. In the case of inclined tunnels, for both rectangular and horseshoe-shaped tunnels, the SE level near the fire source obviously deteriorates. Thus, the longitudinal velocity range for the purpose of maintaining a relatively less serious SE level should be slightly reduced for inclined tunnels compared with horizontal tunnels. Full article
(This article belongs to the Special Issue Advance in Tunnel Fire Research)
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18 pages, 4146 KiB  
Article
Experimental Study of Scale Effect in Tunnel Fires at Different Sealing Ratios
by Ling Chen, Xuan Wang, Baiyi Li and Peng Lin
Fire 2023, 6(3), 92; https://doi.org/10.3390/fire6030092 - 28 Feb 2023
Cited by 1 | Viewed by 1752
Abstract
Fully or partially sealing the openings of tunnels to accelerate the self-extinction of fires provides a promising firefighting tactic to beat large fires in a long tunnel. So far, most experimental studies on the characteristics of fire with different sealing ratios have been [...] Read more.
Fully or partially sealing the openings of tunnels to accelerate the self-extinction of fires provides a promising firefighting tactic to beat large fires in a long tunnel. So far, most experimental studies on the characteristics of fire with different sealing ratios have been conducted in reduced-scale tunnels. However, whether the findings in a reduced-scale tunnel can be converted to its full-scale prototype tunnel based on scaling laws has not yet been adequately studied. A series of experiments with heat-release rates of 15.8, 31.6 and 63.2 kW were conducted with sealing ratios ranging from 0% to 100% in a prototype tunnel measuring 20 m long, 0.9 m wide and 0.46 m high. The experimental results were compared with those from a 1/2 reduced-scale tunnel measuring 10 m long, 0.45 m wide and 0.23 m high. It showed that temperature rise along the tunnel in the 1/2 reduced-tunnel could be significantly underestimated. The differences in temperature rise increased monotonously with distance away from the fire seat, and they were as high as 70% at the tunnel portals, irrespective of the heat-release rates and sealing ratios. The study showed that the scale effect of fires was not sensitive to the Reynolds number of flows in tunnels. The minimal sealing ratio for the self-extinction of fires in the prototype tunnel was 85%, whilst it was 75% in the 1/2 reduced-scale tunnel, and the study revealed that the fires were much easier to extinguish in the 1/2 reduced-scale tunnel than those in the prototype tunnel, where the fires can sustain in a lower oxygen concentration. The study demonstrated that scaling laws could be invalid for tunnel fires with different sealing ratios and that results observed in reduced-scale tunnels should be further verified when applied to full-scale prototypes. Full article
(This article belongs to the Special Issue Advance in Tunnel Fire Research)
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16 pages, 5971 KiB  
Article
Simulation of Thermomechanical Coupling and Evaluation of the Fire Resistance for the Joints of Fabricated Frame Tunnel
by Zhen Huang, Jiawei Zhang, Zimao Peng, Hongbo Hu, Huiping An, Xulong Yang and Tianxiang Xiong
Fire 2023, 6(1), 3; https://doi.org/10.3390/fire6010003 - 21 Dec 2022
Cited by 3 | Viewed by 1842
Abstract
Fire in a tunnel will deteriorate the mechanical properties of the tunnel. For fabricated tunnels formed by splicing prefabricated components through joints, under the high temperature of a fire, the rapid degradation of the bearing capacity of the joints can easily lead to [...] Read more.
Fire in a tunnel will deteriorate the mechanical properties of the tunnel. For fabricated tunnels formed by splicing prefabricated components through joints, under the high temperature of a fire, the rapid degradation of the bearing capacity of the joints can easily lead to tunnel damage. In this study, a new type of joint (bolt-pin joints (BPJ)) for prefabricated frame tunnels is proposed. To investigate the fire resistance of the new joint and the other three fabricated frame tunnel joints (including mortise joints (MJ), bolt-mortise joints (BMJ), and pin joints (PJ)), a three-dimensional solid model of four types of fabricated frame tunnel joints is established using the finite element calculation software ABAQUS. According to the standard European HC curve, the heat transfer characteristics of the joint model are analyzed, the temperature distribution law of the joint under fire is studied, and the flexural bearing performance and deformation characteristics of the joint before and after the fire are discussed, as well as the influence of the initial axial force on the flexural bearing capacity and the opening of the joint under fire. The analysis result shows that the vertical peak load of the BPJ is higher than that of the other three joints at room temperature. Under the combined action of the pin and bolts and the tongue groove, the vertical peak load of the joints can be effectively increased and the midspan vertical displacement can be reduced. The decrease degree of the vertical peak load of the MJ and BMJ under fire exposure is greater than that of the other two joints, and the opening of the BPJ is 19 mm, which is much smaller than that of the other three joints. When the initial axial force is increased, the openings of the four joints under fire exposure are reduced, the vertical peak loads of the PJ and BPJ are increased, and the vertical peak loads of the MJ and BMJ are not significantly increased. Overall, the BPJ demonstrates better fire resistance. Full article
(This article belongs to the Special Issue Advance in Tunnel Fire Research)
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11 pages, 2426 KiB  
Article
A Simulation Study on the Smoke Control Effect with Different Smoke Exhaust Patterns and Longitudinal Air Supply for Ultra-Wide Tunnels
by Ying Li, Fang Huang, Chuyuan Ma and Kaixuan Tang
Fire 2022, 5(3), 72; https://doi.org/10.3390/fire5030072 - 30 May 2022
Cited by 8 | Viewed by 3242
Abstract
This study was motivated by the lack of understanding of the smoke control effect on an ultra-wide tunnel fire, with different smoke exhaust patterns (sidewall and top exhaust patterns) and longitudinal air supply volume (0, 30%, 50%, 70%, and 90%). A full-scale ultra-wide [...] Read more.
This study was motivated by the lack of understanding of the smoke control effect on an ultra-wide tunnel fire, with different smoke exhaust patterns (sidewall and top exhaust patterns) and longitudinal air supply volume (0, 30%, 50%, 70%, and 90%). A full-scale ultra-wide tunnel model was constructed based on the FDS and the fire parameters were analyzed, such as the longitudinal spread distance of smoke, the smoke layer height and the temperature at safe height. In addition, the smoke exhaust efficiency was calculated based on the mass flux of CO2, and the smoke control effect with different smoke exhaust patterns and air supply volumes was compared. Results show that the smoke exhaust patterns and air supply ratios have a great influence on smoke spread distance and exhaust efficiency. The smoke spread distance is shortened by increasing the longitudinal air supply volume, and when the ratio of air supply volume to smoke exhaust volume is less than 50%, the top exhaust pattern can control the spread of smoke better with a smaller smoke spread distance. In addition, the height of the smoke layer is controlled above the safe height of 2 m under the top smoke exhaust, and the temperature at both ends of the tunnel (25 °C) is lower than that under the sidewall exhaust pattern (35 °C). The smoke exhaust efficiency was calculated based on the mass flow rate of CO2, and the exhaust efficiency of the top exhaust pattern (~70%) is significantly higher than that of the sidewall exhaust pattern (~55%). However, as the air supply volume increases, there is a reduced increase in the exhaust efficiency. Therefore, taking the economic cost into account, the air supply ratios of 30% and 50% are the best for top and sidewall exhaust patterns, respectively. The results of this work provide important information about smoke distribution characteristics in an ultra-wide tunnel fire and may guide its design of smoke exhaust. Full article
(This article belongs to the Special Issue Advance in Tunnel Fire Research)
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