Multilayer Subway Station Ventilation Exhaust Control And Safety Assessment

With the rapid development of subway construction, many new problems and challenges to fire safety are presented.In recent years, several disastrous subway fires occurred continuously, with a large number of casualties and the insufficiency of fire control measures is fully uncovered.Therefore, it is of much significance to study the smoke movement charaeteristics and system security in subway station fires. In order to discuss the flowing rule and the control of the smoke, the physical model of one four-floor subway station is established, The three-dimensional field simulation about the spread of smoke when fire occurs in the subway platform is carried out by computational fluid dynamics.The study of this paper includes four parts as follows:(1) The flow process, characteristics and the main driving force of the smoke in the subway station fire are analyzed, meanwhile the common way to control smoke and its main effect factors are introduced, providing a theoretical basis for the next numerical simulation on ventilation control modes of subway station.(2) Aim at the fire on the third underground floor of the station, the influence of the operation mode of air supply system in the lower floor on mechanical smoke exhaust effect in the fire floor is analyzed using field simulation software FDS5.3. A ventilation control mode that the air supply systems in both lower and upper floors should be operated is proposed.(3) Through theoretical analysis of the critical velocity and numerical simulation results, the critical velocity stated in "Metro Design Criterion" is amended. In addition, the numerical simulation is carried out about the effects of screen door and height of the smoke blocking screen on the critical velocity. With a series of numerical simulations on subway fires,the influence of different relative locations of exhaust opening to fire source on mechanical smoke exhaust effieiency is studied,and the reasonable exhaust opening modes are proposed.(4) In allusion to the development of the subway, the importance of safety assessment on multilayer subway station is proposed. Taking the subway station above as an example, the security assessment on it is carried out by AHP-fuzzy comprehensive assessment.This assessment method also provides reference for other large-scale subway stations or passenger terminals on safety evaluation.In this paper, a series of numerical simulations on ventilation control modes of multilayer subway station are carried out and analyzed, and the security assessment on a typical multilayer subway station is carried out by AHP-fuzzy comprehensive assessment.The study results are also valuable for researching and operating of other stations.