| With the continuous development and expansion of the underground railway system,the crowded traffic situation in large and medium-sized cities has been alleviated.However,subway safety accidents occur from time to time,which seriously threaten the safety of passengers and property.Among them,safety accidents caused by subway tunnel fire are not rare.Subway tunnel is narrow in space,complex in structure and strong in closure.Once a fire breaks out,rescue operation can not be carried out efficiently and personnel evacuation is relatively difficult."Fire Standard for Metro Design"(GB51298-2018)clearly points out that between two single-line interval tunnels,when the continuous length of the tunnel is more than 600 m,contact channel should be set up,and a class a fire door with two-way opening should be set at both ends of the tunnel.At present,the length of tunnel in many subway sections is more than 1500 meters.According to the regulations,2-3 contact channels are required.Therefore,how to effectively use the contact channels to exhaust smoke and ensure the safe evacuation of personnel is a subject worthy of in-depth research.At the same time,China’s current existing regulations,such as the"Code for Fire Protection Design of Building"(GB50016-2014),have made detailed regulations on the smoke control methods in buildings.However,the layout form,size,spacing and other parameters of smoke vents are not clearly defined,which is of great autonomy in practical engineering design.Therefore,studying the influence of smoke vents on smoke exhaust effect has certain guiding significance for formulating smoke exhaust measures and determining relevant design parameters.In this paper,the following research was carried out by using numerical simulation software FDS:(1)In the semi-horizontal ventilation and smoke exhaust mode,when the middle part of the train is on fire and parked in the middle of the tunnel,the influence of smoke outlet layout,area,spacing,length-width ratio and other factors on temperature,CO concentration,visibility and ceiling temperature change of human eye characteristic height layer in the tunnel.(2)In the longitudinal ventilation and exhaust mode,when the middle of the train is on fire and parked in the middle of the tunnel,there is a contact channel and two contact channels,which is more conducive to the speed of smoke exhaust and air supply for evacuation.Research indicates:(1)Under 5 MW fire power,the area of exhaust outlet is 4 m~2,the distance of exhaust outlet is 20 m,the length-width ratio of exhaust outlet is 1:1,and the middle of exhaust outlet is arranged as the best smoke exhaust condition.The smoke exhaust effect under this condition is the best,which is most conducive to the safe evacuation of personnel.(2)The length of the section tunnel is short,only one contact channel.When the speed of air supply and smoke exhaust is determined within 2 m/s,the best smoke exhaust effect is 2 m/s,which is most conducive to the safe evacuation of personnel.(3)The length of the section tunnel is long,and there are two contact channels.When the speed of air supply and smoke exhaust is determined within 3 m/s,the best smoke exhaust effect is 3 m/s,which is most conducive to the safe evacuation of personnel.In this paper,the 1:10 shrinkage experimental model was used to verify the rationality of the numerical simulation results.The reliability of numerical simulation research was proved by comparing the temperature of the human eye feature height layer and the ceiling temperature under typical working conditions in the semi-horizontal ventilation and smoke exhaust mode.The results obtained by using FDS software simulation can reflect the real situation. |
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