Experimental Study On Fire Risk Of Temporary Combustibles In Metro Station

With the acceleration of urbanization in our country,the problems in traffic congestion,road accidents and environmental pollution have brought unprecedented challenges to the existing road transportation.As a convenient mode of transport,metro systems around the world have been undertaking an increasing daily traffic volume.Although the metro brings us many benefits,it is also bearing a high risk of accidents,from the beginning of its construction to the operation stage,especially fire and stampede during peak hours,since there is a large number of passengers and a variety of combustible materials inside the station.It is likely to cause serious casualties in the case of fire or stampede.Therefore,consider the high fire risk of combustibles in metro stations,this paper studies the temporary combustibles such as luggage in metro station,quantifies the potential damage of combustibles in stations,and finally gives reasonable control measures to reduce the probability of fire accidents in metro station.This paper analyzed the characteristics of fire in metro station,established the metro fire safety evaluation index system according to the following aspects: people,machine,management and environment.Based on D-S evidence theory,this paper evaluated the potential risk factors in metro system with significant feature of randomness to metro fire which affect the level of safety.According to the field survey,we got the rule of number of temporary combustibles in the metro station and its distribution on platform.Took PMMA as the research object,numerical simulation was conducted to study the influence of environmental conditions on the ignition of typical combustibles.Depending on the combustion rule of typical flammable materials and field survey data,a simulation model was built to study the relationship between the luggage and fire risk on metro platform.Results indicated the following truths:1)A D-S evidence theory was introduced and a method based on evidence theory was proposed to evaluate the metro fire safety.The evaluation results of the metro fire safety showed that for the consistent evaluation results,the fusion theory of evidence theory effectively reduces the uncertainty range.The evaluation results showed that the lower bound of the evaluation of the unsafe evaluation caused by the environmental factor ?3 is 0.282 and the upper bound is 0.397.The environmental uncertainties have a great influence on the whole system.In the emergency management of metro fires,the environmental factors should be strengthened.2)According to metro station temporary combustibles survey,it was found that the number of temporary combustible into the station reach 5000 within 2 hours.The number of temporary combustibles is consistent with the number of arrival passengers and the number of potential dangerous sources rises sharply during the time interval between two successively arrived trains,which reduce the safety and reliability of metro fires.The distribution of temporary combustibles in the platform is related to the location of vertical transportation facility.The load of combustibles in the waiting areas which passengers preferred is extremely high,and it increases the fire risk in metro stations.3)As for the research of ignition of typical combustibles under the condition of different radiant heater,the ignition time decreases with the increase of temperature of radiant heater.There is a linear relationship between 0.5igt-and temperature of radiant heater.When the horizontal space x increases from 5cm to 10 cm,the critical radiation temperature increases from 981.74 C to 1177.91 C.With the reduction in the temperature of the radiation heater lower and the growth in horizontal space,the rate of the increasing surface temperature slows down,and it is harder to get fire.While the higher source temperature of the radiant heat and the greater the horizontal spaces are,the greater the convective heat flux before the ignition abrupt point is.4)At the beginning of the luggage fire at the metro platform,the heater ignites the combustibles nearby,the power of heat release increases;the smaller the horizontal space between the combustible is,faster the rate of heat release increases is,the greater power of the fire source,the higher peak value of the heat release is,and the decay rate gets slower in the later time.