Study On The Method Of Improving Smoke Extraction Efficiency In Tunnels And Thermal-mechanical Response Analysis Of Tunnel Lining Structures With Different Bending Angles Under Fire

As higher demands for convenience in transportation are urged in modern society,tunnels,the traffic facility to cross terrain obstacles,have been widely used,and the operational safety of tunnels has attracted more and more attention.In the tunnel operating process,the biggest threat to tunnel safety is tunnel fire besides geological disasters.The safety issues of tunnel fire mainly include two aspects: the safety of personnel and the safety of tunnel structure.In this thesis,theoretical analysis,scientific experiments and software simulations are applied to study the fire safety of tunnels.The thesis mainly includes the following three parts:(1)To alleviate the harm of hot and toxic smoke to the people trapped in tunnel and the tunnel lining structure,a measure was proposed to promote the smoke extraction efficiency of tunnel shaft in this thesis,and its effectiveness was verified by FDS(Fire Dynamics Simulator)simulation and theoretical analysis.Moreover,by analyzing the temperature field and the velocity field,the action mechanism of the measure was clarified.(2)To investigate the influence of transverse fire location on the maximum ceiling excess temperature in tunnels with different bending angles,a scaled experimental model was established and nearly 100 cases of experiments were performed.The maximum temperatures were sorted and analyzed theoretically,and the correlation among the maximum ceiling excess temperature,the bending angle of the tunnel,the transverse location of the fire,the heat release rate of the fire and the effective height of the tunnel was derived.The temperature fields of tunnel ceilings were obtained by interpolation method,and the temperature distributions were studied.(3)Full-scale ANSYS models were established,the temperature fields mentioned above were introduced to analyze the stress,deformation,structural temperature distribution and damage degree of the tunnel lining structures.The results show that the change in transverse fire location has a significant impact on the tunnel lining structure.Therefore,taking appropriate ventilation and smoke extraction measures is not only conducive to the personal safety of trapped people,but also of great significance to the safety of tunnel structure.