Study On The Influence Of Subway Train On Smoke Movement In Inclined Tunnel Fire

With the continuous growth of China's population and the accelerated development of small and medium-sized cities,lots of issues like traffic congestion happen nowadays,subway system has played a more and more critical important role in transportation.However,once the subway tunnel fire happened,it will lead to huge property damage and casualties.At the same time,there may be a huge risk to the transformation of the large group of death and wound.In the subway tunnel fire,it is the toxic smoke produced by the combustion which causes casualties.So the study on smoke movement is an important issue.Currently,studies on smoke movement in subway tunnel almost focus on the back-layering length and critical velocity,which only take the tunnel blockage or the slope into consideration.A majority of prediction models have been put forward through experiments and simulations.According to previous studies,the combined situation for slopping tunnel under blockage which are more consistent with the practice was not studied yet.Therefore,theoretical analysis,experimental comparisons and FDS numerical simulations are conducted on the back-layering length and the critical velocity in slopping tunnel with blockage.The main work and conclusions in this study are as follows:(1)the back-layering length in slopping tunnel with blockage is studied.First of all,the back-layering length in horizontal tunnel was investigated based on reduced-scale experiments,we found that the model in this paper fitted Weng's and Li's prediction models well.Then,the tunnel blockage was discussed both experimentally and numerically in this paper,it was obtained that the tunnel blockage reduced the back-layering length because the longitudinal ventilation was changed with the existance of subway train;also it was also known that the trend of back-layering length can be divided into two parts with two regression slopes because of the length of train model.Finally,conbined with the model in horizontal tunnel,the coupling influence between the blockage and the slope on back-layering length was analyzed,it can be seen that the back-layering length will increase with the slope,and a new empirical model was developed based on the numerical and experimental investigation.(2)the critical velocity in slopping tunnel with blockage is studied.Above all,the critical velocity was calculated according to the empirical model of back-layering in horizontal tunnel,some typical models was also compared with it in this paper,the model in this paper can agree well with others' typical models.Secondly,the tunnel blockage was also discussed,results show that the reduced ratio of critical velocity was equal to the ratio that the train model occupies 57%of the tunnel cross-section.In the end,the critical velocity model in slopping tunnel with blockage was put forward.