Study On The Impact Of Blockage And Slope On Semi-horizontal Extraction Effect In Subway Tunnel Fire

Subway traffic system is developing quickly in recent years.Usually the subway carriage is crowded,the space of subway tunnel is confined.Subway security has been the focus of attention.Fire accident has been one of the higher probability of occurrence of disaster accidents and smoke is an major factor leading to casualties in fire accidents.then,It is very important to exhaust smoke in tunnel timely and control the spread speed of smoke in carriage effectively after the fire.When the train compartment is on fire,through comprehensive consideration the ideal smoke exhaust way is to adopt semi-transverse ventilation which can exhaust the smoke near the burner to protect most of the passengers from being trapped by smoke.In the actual situation,there are many different height subway tunnels,then,the train in different height of subway tunnels will form different blocking ratios.Along with the blockage ratio changing,the smoke exhaust effect will be changed.As a result of the influence of geographical conditions,the slope often exists in the tunnel,and the influence of the gradient on the smoke flow can not be ignored.This study considered three possible circumstance of fire in subway tunnel.Fire occurs in the middle of the train in non-slope tunnel.Fire occurs in a certain slope of subway tunnel without train.A train is on fire in the slope of the subway tunnel.The paper adopted FDS which is a fire dynamics simulation software to establish subway tunnel model and simulated and analyzed in each case.In the first case,the paper established models of the same train on fire in three different height subway tunnels,when three different blockage ratios are formed,studied impact of smoke exhaust speed and the number of smoke vents on semi-horizontal extraction effect.compared the effect of smoke exhaust speed and the number of smoke vents on smoke extraction efficiency under different blockage ratios.In the second case,the paper seted three slopes 1%,2%,3%,established models of tunnel fire without train,studied the impact of slope on effect of natural smoke extraction and semi-horizontal extraction,analyzed the effect of the position and number of the exhaust vents on semi-horizontal extraction in the slope subway tunnel.In the third case,the paper combined to the results of previous two cases to establish the model of fire occurs in the middle of a train in slope subway tunnel,studied the effect of slope on semi-horizontal extraction under different blockage ratios.