A Study On Temperature Distribution Of Tunnel And Damage Of He Lining Structure Under High Temperature Of Fire

Tunnels will have an occurrence of accidents when it is providingservices, and sometimes even the fire disasters will be caused in thetunnels. The tunnel fire will bring about strong scent of smoke and hightemperature. The smoke, pervading the whole tunnel, has negativeinfluence on the activities of fleeing for people’s lives and rescuing thelives and property. The fire will develop further and also have an impacton people’s lives and safety of tunnel structure. The simulation of firescene and the damage assessment of tunnel lining concrete after hightemperature of fire can provide the references and basis for the fireproofing technology for tunnel.The paper has a systematic study on the tunnels fire by means oftheoretical analysis, numerical simulation and experimental investigations.The major content of the paper can be concluded as followed:(1) The experimental study on the compression strength of cube of tunnel lining concrete samples after high temperature of fire.(2) The change law of the smoke in the tunnel with differentventilation velocity and the regularities of distribution of temperature oftunnel vault are researched by simulating fire disaster with different fireheat release rate (HRR, HRR=30MW and50MW).(3) The damage extent of tunnel lining concrete after hightemperature is assessed after numerical simulation of temperaturedistribution of the tunnel lining.The conclusions can be made as followed:(1) The compression strength of the concrete samples withdifferent strength parameters after different high temperatures has a trendof reducing, and the compression strength of the concrete subjected to200℃and300℃is a little higher than those subjected to the normaltemperature. And the experiment shows that the higher temperatures theconcretes are subjected to, the rougher the texture of concrete is, andthere are much more cracks and fractures in concrete which also have alower compression strength. The compression strength reduction factorsof concretes which are subjected to high temperature of fire are obtained,which can be used as reference for design.(2) With the FDS, the tunnel fire with30MW and50MW underdifferent ventilation velocity are simulated. The former has a wind speed at0m/s,3m/s,4m/s and5m/s, and the latter0m/s,4m/s,5m/s and6m/s.The result shows that ventilation velocity has an effect on the smokeflowing and its thickness. If the wind speed is less than critical windvelocity, fire smoke in the tunnel will have a countercurrent phenomenon,and if it is greater than the critical wind velocity, the countercurrentphenomenon will disappear. As the wind velocity increases, the thicknessof smoke layer will grow in the backward position of tunnel. Meanwhile,the critical wind velocities of fire of30MW and50MW are gained, whichare4m/s and5m/s respectively.(3) The wind velocity also has an impact on the temperature ofinner tunnel. The temperature of the fire center is highest when there is nowind and if the wind velocity increases, the location of the highesttemperature will move towards the backward position of fire zone. Thevelocity has positive influence on controlling high temperature of firedisaster. From the study, it can be known that wind speed can reduce thetemperature and the bigger the wind velocity is, the range of the reductionof temperature is much more. The longitudinal temperature distribution oftunnel vault are obtained, which can be served as the reference to thenumerical simulation of temperature distribution of lining section.(4) The numerical simulation of temperature distribution oftunnel lining section can reveal the relationship between temperature andthe location in the tunnel lining. By fitting the temperature and the location in the tunnel lining, the curve can be gained, which can be usedto find each temperature in the tunnel lining after high temperature offire.