Thermal Strain-Induced Concrete Cracking in Immersed Tunnels: Implications for Fire Resistance Design

In the event of a fire in an immersed tunnel, the heating stage induces thermal expansion of the inner surface, leading to the pulling and cracking of concrete on the outer surface. These cracks propagate rapidly, potentially reaching significant depths. Through-cracks in the concrete pose a direct threat to the safety of the immersed tunnel by allowing seawater leakage. Additionally, even in the absence of through-cracks, concrete cracking exposes rebars to the marine chloride environment, accelerating their corrosion and reducing the service life of the tunnel. Therefore, it is crucial to consider the potential for concrete cracking due to thermal strain in the fire resistance design of immersed tunnels.