Study On Smoke Zoning Control And Evacuation In Metro

Metro disaster, especially, the fire, as well as the research on controlling fire hazards which is related to the prevention of major casualties, plays an increasing important role in the safety of subway operation. This thesis relies on "Study on Fire Sub-controlling of Changsha Subway Station"-one of the Science and Technology Projects of Hunan Province, together with the Central South University Graduate Innovation Grant project, "Research on Fire Disaster and Smoke Zoning Control in Underground Space" and so on. A profound study has been conducted on how to effectively control the fire and smoke, how to escape from fire area for the staffs and passengers, and how to create a safer environment. After reviewing the existing methods of fire and smoke controlling, some drawbacks of them are pointed out, in order to overcome these deficiencies, a new method for smoke control is presented, and specific smoke zoning control models are also conducted for tunnel sections and stations respectively. Then, a systematic study is carried out through theoretical calculations, numerical simulation and experimental tests. The main content of this article as follows:(1) Reviewing the architectural forms of Metro and the existing methods of smoke control. A numerical simulation is conducted by using the existing fire and smoke control laws for tunnel and station, the results show that it fails to separate smoke from passengers completely, there exists risks. Assuming that the longitudinal ventilation measure is adopted for smoke controlling and the train will stop if fire occurs, under the condition that fire happens in the middle of train which runs in a tunnel section, it will be risky for passengers of the side through which the smoke goes. In underground station, the existing method can suppress the spread of smoke (spread to ticket hall floor) within a certain period. However, the smoke in the station spreads broadly at the platform. Moreover, it is difficult to deal with complex fire conditions. Therefore, it is really risky without any improvement in the existing methods.(2) By introducing the disaster sub-controlling method and fire control methods to the design of Metro fire disaster control, the smoke zoning control and smoke-free evacuation principle are proposed. Specifically, the protection space is divided into two or more relatively independent zones (smoke partition zones), the spread of smoke and fire will be constrained in a specific area, in which the mechanical ventilation will be adopted. Passengers in the fire zone can evacuate out to non-smoke zones quickly, and then they will easily get access to a safe place; people within the non-smoke zones can avoid the effects of smoke while fleeing away, which highly enhances the rescuing factor.(3) Longitudinal smoke zoning control model for tunnel is proposed according the features of tunnel. Both of numerical simulation and fire experimental tests are conducted to analyze the characteristics of smoke control for different ventilations, different smoke extraction rates, and various fire power conditions. The results indicate that this model can prevent the smoke spreading into evacuation channel, even though the efficiency of different types of ventilation may be a little different. Specifically, the best method is to combine the unilateral smoke-control in the railway district and the evacuation routes with fresh air supplement. Because, no matter wherever catch fire, Metro controllers can supply fresh air in evacuation channel, and then the unilateral ventilation of smoke can be carried out after the evacuation of passengers, which can effectively ensure the safety of evacuation as well as lower high-temperature in a fire hazard.(4) The smoke zoning control with curtains is proposed. Both the numerical simulation and fire experiments are conducted to study the characteristics of this model under different situations in stations, such as different height of curtain from its bottom to ground, different places of fire sources, different high-power of fire. The study reveals that, a negative pressure environment will be formed in the fire district, which will cause air flow orderly. It also can constrain fire, smoke, and high temperature within the local area in a long time. Therefore, this model can be applicable to complex fire conditions. The research proves that evacuation will be enhanced if the distance between the bottom of curtains and the ground is the value of 2m; if this distance reaches to 0.5m, the effect of fire and smoke control is more stable, and therefore the process of shutting down curtain should be carried out step by step.(5) Theoretical analysis, numerical simulation and experimental tests has been conducted for the model of smoke zoning control with curtains, the results of them have proved that the critical volume of smoke-exhaust of this mode is identical to the additional volume of gas, which is less than the volume of smoke produced by a fire. Critical volume of smoke-exhaust is proportional to the power of fire source. As for the same power of fire resource, when the distance between the bottom of curtains and ground are equal to 2m, the critical volume of smoke-exhaust is more than that of the distance with the value of 0.5m.A preliminary study is conducted to apply smoke zoning control method to other buildings and tunnels, such as the railway tunnels, highway tunnels, underground garages, underground shopping malls, theaters, supermarkets, flammable materials storage and so on.