Fire Thermal Stress and its Damage to Subsea Immersed Tunnel

Relying on subsea immersed tunnel of the Hong Kong-Zhuhai-Macau Bridge (HZMB) project, this paper studies thermal stress redistribution and fire damage of twin-tube structure for achieving a quantitative assessment to thermal stress damage of tunnel linings in fired condition. Being different from classical static analysis method used for tunnel structure, a modified calculation method is proposed for building thermal-mechanical coupled model of twin-tube structure with basic temperature rise curve of fire as thermal boundary input. In this coupled model, thermal and mechanical parameters used to reinforced concrete structure could change over time. By means of the analysis of transient heat conduction, temperature gradient inside tube structure is obtained. On this basis, heat and outer loads' combined effect on twin-tube is carried out to solve the stress redistribution in the direction of tube depth. At last, this paper focus on the effect of having or note fireproof board on tube damage depth. The results show that the temperature inside tube would rise and bring down rapidly, and that tube surface stress induced by heat would exceed concrete compressive strength and lead to disruption. Having or not thermal insulation is a key to tube structure. The depth of heat stress damage would reduce 58.3 percent under the condition of laying fireproof board.