Research on Mechanical Response and Damage Thickness of Immersed Tube Tunnel Structure Exposed to High Fire Temperature

ABSTRACT Fire accidents directly threaten the tunnel operation target that are safe, comfortable, efficient. As a new type of tunnel, the pipes and joints of immersed tube tunnel are difficult to repair and replace, which makes post‐fire damage assessment particularly important. In order to efficiently evaluate the damage range of concrete in immersed tube tunnel after fire, this paper establishes the stress calculation model of immersed tube tunnel structure under fire by theoretical analysis and numerical simulation. The stress variation rule of immersed tube structure under fire action is studied. This study found that the fire influence range on the structure can be considered as 60 cm, while the thickness was 25 cm subjected to high fire temperature, and there was a large increase in compressive stress which is in the thickness range of 0–10 cm, and the compressive stress was the largest in deep buried section. The relationship between the damage thickness and the ignition time was applied . The study bridges the gap of fire damage assessment of immersed tube tunnel in China and provides powerful scientific and technological support for fire damage assessment and damage maintenance. At the same time, it provides a comparative study for the fire prevention of tunnel structure.