Study On Critical Velocity And Temperature Characteristics In Non-sloped And Sloped Tunnel Fire Under Blockage Effect

Along with the large-scale construction of subway in China, Its potential harmfulness is also given enough attention. Especially when the subway tunnel fire comes, it extremely easy to cause the casualty accident and significant economic loss.At present, the research on tunnel fire critical velocity and temperature characteristic is mainly concentrated in the no blockage and no slope case. But in practical situation, the influence of the slope and blockage effect can not be ignored. In this paper, based on surveying a large amount of literature at home and abroad, discovering the previous research on the study of the slope and blockage effect on the tunnel fire is relatively little.In this paper, Taking a subway tunnel as the prototype, designing the 1:10 scaled model experiment, experimental study on the tunnel fire critical velocity and temperature characteristic in the case with blockage and no blockage is taken.Firstly, In this paper, the dimensionless critical velocity formula is obtained based on the experimental data of critical velocity in the no blockage case.Investigating the influence of blockage effect and obtaining the calculation formula of critical velocity on this basis of it. Then the calculation formula of critical velocity under the slope effect is corrected using the numerical simulation data and the change rules of critical velocity under the influence of the slope and blockage effect is discussed. At last the widely used Kennedy formula under the blockage effect and no blockage effect is also investigated and corrected.For the study of tunnel fire temperature characteristic, we firstly verify the computational model of maximum temperature of tunnel ceiling according the experimental data without blockage. Then the influence of vault maximum temperature under blockage effect is discussed and the calculation formula of vault maximum temperature under blockage effect is obtained. The formula is agreed well with the other small size experimental data in this paper. The computational model of maximum temperature of vault is corrected according the numerical simulation data. Next the theoretical model of tunnel fire temperature decay is verified according the experimental data of temperature of tunnel ceiling. Afterwards it is corrected under blockage effect according the experimental data. The slope correction of the theoretical model of tunnel fire temperature decay constructed using the numerical simulation data. Finding that the above correction insculates with numerical simulation data and experimental data. At last the maximum temperature position of vault is discussed comparing the model experimental data with the existing model. The influence of maximum temperature position of tunnel fire under blockage effect is analyzed according the temperature experimental data under blockage effect and the idea using the local hydraulic diameter as characteristic dimension of model is proposed. The experimental data under blockage effect corrected in this idea is intensive and fits well.