The Study On The Tunnel Fire Behavior Characteristics And Thermal-mechanical Response Based On The Variation Of The Bending Angle And Fire Source Height

With the continuous development of economy and science and technology,various kinds of tunnels have been built continuously,thus shortening the distance between the two places and reducing the cost of time and economy.Despite the benefits and increasingly sophisticated technology,there are still a number of safety issues,such as fire.Due to the characteristics of tunnel-narrow and long,once the vehicle accident causes a fire,the heat and smoke generated by it is bound to bring great harm to the personnel and tunnel structure.In order to evaluate the fire resistance performance of the tunnel structure,it is necessary to make research about the tunnel fire.Double fire experiments,curved tunnel fire experiments and finite element analysis method are used in this thesis,to investigate the flame height of the coupling flame,the fuel mass loss rate,the temperature distribution of tunnel ceiling longitudinal center axis and thermal-mechanical response of the tunnel.The main contents are as follows:In this thesis,by changing the rectangular burner size,aspect ratio of the burner and the distance between the two burners in double fire experiments respectively,the change of the flame height of the coupling flame is studied.In the data analysis,the characteristic length D,which represents the distance between the burner and the burner size,is proposed.And the length of the coupling flame is dimensionless treated by the characteristic length.The model of the coupling flame height is obtained,finally.In order to study the fire characteristics in curved tunnels,a series of reduced-scale tunnel experiments are conducted,with different bending angles,different heights of the burner,different sizes of the burner,and different positions.The changes of the mass loss rate and the temperature distribution of tunnel ceiling longitudinal center axis are analyzed respectively.And the results show that the mass loss rate of fuel is negatively correlated with the bending angle and positively correlated with the height of the burner and the size of burner.As far as the maximum temperature of the tunnel ceiling is concerned,the change of the bending angle does not make a difference,that is,the maximum temperature obtained in the four curved tunnels satisfies the same model.On the side directly above the fire source,the temperature of the longitudinal central axis of the ceiling conforms to the law of exponential attenuation.In the same curved tunnel,the temperature distribution satisfies the same exponential model.However,in the tunnel with different bending angle,the temperature distribution model is different,which indicates that the change of bending angle will affect the temperature field of the ceiling.In this thesis,0° tunnel is selected as the representative.And the temperature distribution of the central axis is used to conduct mechanical analysis under the conditions of no temperature load and temperature load respectively.The results show that the deformation of tunnel lining will be restrained to some extent in the temperature field generated by 23 MW ignition source.