Fire Safety in Immersed Tunnels: A Critical Review and Potential Solutions

As the popularity and development of tunnel technology continue to grow rapidly, fire has become a critical issue in tunnel safety. With the increasing number and speed of automobiles, tunnel fires resulting from automobile accidents have become a significant risk factor. In China, statistics indicate that the probability of tunnel fires is between 10-17 times per 100 million km of a car. Immersed tunnels, which are deeply buried in the seabed, are particularly vulnerable to the impact of fires in seawater environments. For hydraulic structures, water seepage can cause severe disasters, affecting both the structural bearing capacity and safety. Concrete with high moisture content is susceptible to spalling and cracking under high temperatures of fire, which is especially concerning for immersed tunnels due to their high concrete moisture content. The thermal expansion of concrete inside the tunnel during a fire can also lead to the tensile cracking of the concrete outside the tunnel, further compromising structural integrity. To better understand the impact of fire on the structure of immersed tunnels, Wang and Li (2015) conducted a simulation using ANSYS. This paper aims to explore the effects of fire on tunnel structures and highlight potential solutions for improving tunnel safety.