Analysis of the Hsuehshan Tunnel Fire in Taiwan

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Abstract

This paper focused on analyzing the Hsuehshan Tunnel Fire in Taiwan, which occurred from a bus fire in the afternoon of May 7, 2012 and caused two death and 34 injuries. Major object damages were reviewed and CCTV records were investigated toward understanding the fire temperature, smoke layers and situations of people in the tunnel refuge area (Fire Scenarios Analysis & Egress/Rescue Strategies of the 2012 Hsuehshan Tunnel Fire in Taiwan, MOTC, Taiwan, Jan., 2016.). Data collected from the fire scene were fed into fire scene reconstruction using CFD method (i.e., Fire Dynamics Simulators - FDS). It reveals that the fire temperature reached 800–900 °C and HRR was around 25–30 MW, which are consistent with the reviews of the incident and experiment data. Moreover, the fire temperature obtained from the CFD method when compared with experiment data is more reasonable. It is considered lift-threatening in terms of visibility, temperature and radiant heat flux for both road users and self-defense fire/rescue team when the fire heat reaches 10 MW. It was also reasoned that the fire spread through exit holes on the bus roof and heat was carried by the ventilation flow, leading to serious damage of lighting objects and cable traps above the bus. This study also suggests that the best option for people encounter tunnel fire is to leave their vehicles immediately and evacuate toward upstream direction of the fire. For those who are in the downstream of the fire, they should use the exit doors on the connection tunnel to escape the incident.

Introduction

The Hsuehshan Tunnel is ranked as the ninth long tunnel in the world (12.9 km, completed in 2006), which is constructed with two primary tunnels (two tubes one way) and one pilot tunnel. It suffered the first time of serious fire incident damage of 2 dead and 34 injured in 2012. Fig. 1 is the diagram of the tunnel that can help us to realize the tunnel structure clearly.

At 13:24, May 7, 2012, at 26 K Southbound in the Hsuehshan Tunnel, a small truck (Vehicle-F) had a flat tire. Two automobiles (Vehicle-D,E) and one bus (Vehicle-C) after it slowed down and dodged successfully. However, another bus (Vehicle-A) after them was suspected not keeping distance, and collided with the front wagon (Vehicle-B) and the bus (Vehicle-C). Then, the bus (Vehicle-A) and the wagon (Vehicle-B) were on fire immediately. The locations of these cars were indicated in Fig. 2. After detail incident investigation and review of CCTV in the tunnel, the main cause of incident is owing to bus (Vehicle-A) did not notice the front car and made the wagon (Vehicle-B) on fire by collision. There were totally 6 vehicles involved in the incident and caused 2 dead (passengers on the wagon (Vehicle-B)) and 34 injured (Incident Report of Taiwan Area, 2012).

Section snippets

Rescue routes

The Hsuehshan Tunnel Broadcast Center announced for the road users in southbound tube to pull their cars over on the waysides for rescue team to access easily and closed the northbound slip road to avoid other vehicles approach the incident when the accident was identified, indicated as Fig. 3. Meanwhile, the authority asked the police from different cities on both sides of the tunnel to operate traffic control. The Tunnel Broadcast Center announced right after the incident occurred and asked

Temperature analysis

Many researches had completed full scale vehicle fire experiments related to highway tunnels, and estimated fire heat release rate (HRR) and temperature in different scenarios.

Smoke movement

Evacuation Stage: According to the design of Hsuehshan Tunnel ventilation system, it would be operated as the previous setting (2–4 m/s) after fire alarm system detects the fire and the situation would turn into the escaping model, indicated in Fig. 11, to keep the back-layer from the road users and to maintain a safety environment. 10 min after the fire ignition, CCTV monitored that smoke was controlled around the fire point and the visibility could be around 80 m at the upstream of fire point

FDS model description

FDS is a computational fluid dynamics (CFD) model that can be applied to describe the flow of smoke and hot gases from a fire. It has been aimed at solving practical fire problems in fire protection engineering as well as providing a tool to study fundamental fire dynamics and combustion. This study employed the FDS to reconstruct the fire scene (Shen et al., 2008) and measure the fire properties such as temperature, visibility, time of smoke layer descending, concentration of CO and CO2.

Design fire (Huang, 2010)

  • a.

    Tunnel

Concluding remarks

  • a.

    HRR and Temperature of bus and wagon collision should be modified as 25–30 MW, and as 800–900 °C, respectively, which are agreed with the reviews of the incident and experiment data. The fuel-rich fire in the bus (Vehicle-C) blew out from the roof exit hole resulting in entrainment air. It caused fire to spread forward downstream and burned the cable trays and lighting objects.

  • b.

    This study suggests that the best choice for people encountering a tunnel fire is to leave their vehicles as soon as

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