Study On Structural Fire Safety Of Long And Large Subsea Railway Shield Tunnel

The Jintang Subsea Tunnel on the Ningbo-Zhoushan Railway is currently the longest high-speed railway subsea tunnel in the world.After completion,it will end the history of the Zhoushan Islands without trains,greatly facilitating people’s travel.However,with the increase of tunnel length and design speed,its operation safety requirements are also constantly improving,which needs to be paid enough attention.Due to the narrow and long structure of the tunnel itself,once a fire occurs in the tunnel,the temperature will rise sharply,and the high temperature smoke will pose a serious threat to the lining.The segment joint is the weak part of the shield tunnel.Local damage will endanger the safety of the entire tunnel,and even serious water leakage accidents may occur,resulting in the entire tunnel being scrapped.Therefore,the fire safety problem of the subsea railway shield tunnel needs to be solved urgently.Based on the above reasons,this paper adopts research methods such as literature research,theoretical analysis,and numerical simulation to study the fire scene of the long and large subsea railway shield tunnel,the high-temperature spalling of the segment concrete,the high-temperature damage of the joints and the overall safety based on the shield tunnel section of the Jintang Subsea Tunnel on the Ningbo-Zhoushan Railway.The main results obtained are as follows:1.Through literature research and numerical simulation,the uniform fire scene and the non-uniform fire scene of the tunnel were given.The influence of ventilation velocity on the fire temperature distribution was proved.And,the approximated calculation method of fire temperature distribution of the single-hole double-track shield railway tunnel was proposed.2.Through literature investigation,theoretical analysis and numerical simulation,the control mechanism of high-temperature spalling of high-strength concrete was revealed.The discriminant conditions of high-temperature spalling of high-strength concrete were given.The simulation algorithm of high-temperature spalling of high-strength concrete was established.And the relationship between the spalling depth of high-strength concrete and the fire temperature and the fire duration was obtained.3.Through literature investigation and numerical simulation,the high-temperature damage law of segment joint bolt and rubber gasket was proved.A simplified thermo-mechanical coupling model of shield tunnel lining was established.And the change law of waterproof performance of the segment joint under high water pressure and fire was obtained.4.Through numerical simulation,theoretical analysis and literature research,the temperature distribution law of the segment structure exposed to fire was proved.The deformation law of the lining and the internal force change under high temperature were obtained.And the fire protection methods for the long and large subsea railway shield tunnel were given.The above results can provide significant references for the structural fire-resistant design of the long and large subsea railway shield tunnel.