A Study on the Evacuation of an Extra-Long Highway Tunnel Fire—A Case Study of Chengkai Tunnel

Abstract

The smoke from tunnel fires spreads over long distances and is difficult to vent. Smoke accumulation leads to high temperatures, low visibility, and high concentrations of toxic gases, which greatly hinders the evacuation of people inside the tunnel. In this paper, a representative extra-long highway tunnel—Chengkai Tunnel—is selected as the engineering background, and a tunnel model is built using FDS and Pathfinder software to simulate the fire scenario and evacuation scenario under different longitudinal wind speeds. The concept of safe evacuation reliability is proposed to describe the relationship between the ASET (available safe egress time) and the RSET (required safe egress time). The simulation results show that with the increase in longitudinal wind speed, the ASET upstream of fire source increases first and then remains unchanged, while ASET downstream of fire source increases first and then decreases. The ASET upstream of the fire source is affected by visibility, while the ASET downstream of the fire source is affected by visibility when the wind speed is low, and is affected by temperature as the wind speed increases. The bottleneck effect is an important reason for the long evacuation time of people. The blockage time is a power function of the evacuation movement time, and increasing the width of the cross passage can improve the evacuation efficiency of the tunnel. The increase in the number of evacuees will reduce the reliability of the safe evacuation of personnel. Among all simulated scenarios, a longitudinal wind speed of 2.5 m/s has the highest safe evacuation reliability, with 0.79, 0.92, and 0.99 for scenarios R1, R2, and R3, respectively. Excessive wind speed reduces the safe evacuation reliability downstream of the fire source.

Simulation of Fire Evacuation in a Naturally Ventilated Bifurcated Tunnel

“…However, due to the small rate of heat release from the fire source, the time of its formation is after the formation of the hazardous area According to the analysis method of scenario A0, the ASET of each scenario is shown in Table 6. From the table, it can be seen that the ASET influencing factor for all scenarios in this paper is visibility, and it is worth mentioning that for the same fire source, as the wind speed increases, it will also form a hazardous area with stable existence and penetration with a temperature exceeding 60 • C. However, due to the small rate of heat release from the fire source, the time of its formation is after the formation of the hazardous area of visibility, and therefore it can be inferred that when the heat release rate becomes larger, the factor that determines the ASET will be shifted to temperature, which was also concluded in the study of Wang [27].…”

“…tration with a temperature exceeding 60 °C. However, due to the small rate of heat release from the fire source, the time of its formation is after the formation of the hazardous area of visibility, and therefore it can be inferred that when the heat release rate becomes larger, the factor that determines the ASET will be shifted to temperature, which was also concluded in the study of Wang [27]. According to the analysis method of scenario A0, the ASET of each scenario is shown in Table 6.…”

“…Numerical simulation of evacuation is mainly realized by models such as FDS + EVAC, STEPS, Pathfinder, etc., and Ronchi [26] compared their differences in 2012. Evacuation safety is analyzed mainly by comparing the Available Safe Egress Time (ASET) and the Required Safe Egress time (RSET), and if ASET ≥ RSET, then it is considered that the evacuees can be safely evacuated, based on which Wang [27] introduced the concept of evacuation reliability. Yamaroto [28] combined real-coded cellular automata to simulate personnel evacuation and analyzed the safety of personnel by visualizing the location of the last evacuee relative to the evacuation hazardous area.…”

Study on Smoke Spreading Characteristics of Highway Tunnel Fire

“…In earlier literature, the authors have done extensive research on the tunnel fires [1]. Using FDS software to build a tunnel model to simulate fire scenarios at different wind speeds, which increases the reliability of personnel arriving at safe locations.…”

Cluster Analysis of Freeway Tunnel Length Based on Naturalistic Driving Safety and Comfort

“…The tunnel is relatively closed, with significant changes in road and environmental conditions, and the driving behavior is different from standard freeway sections, which can easily lead to traffic congestion and can increase traffic safety risks [1,2]. Once an accident occurs in a tunnel, it easily results in a secondary accident, and the severity of the accident and property damage are higher in tunnels than in standard freeway sections [3][4][5]; thus, the traffic danger situation can be more severe.…”