Description
Densely populated cities offer unique challenges in planning an underground train station. There are various challenges in building a compact, economical, and sustainable underground station. In most scenarios space is a key concern and necessitates designers to reduce the footprints of service area (electro-mechanical rooms) located in back of house area without affecting the key functions and without compromising the public experience, comfort and safety.
Tunnel ventilation fans (TVFs) and trackway exhaust fans (TEFs) usually require a significant underground space but their presence is necessary being essential fire life safety element. In a typical underground station, two TVFs are required at each station end (total four TVFs per station) and two to four TEFs are required in the mechanical room in back of house area.
This study explores the possible tunnel ventilation system arrangements to optimize the underground space and their associated cost by reducing the required number of fans without compromising the design criteria and functional requirements of the system.
This study also covers the global perspective of tunnel ventilation system design and evaluates the need of TVFs at each end of the station and suggest optimization techniques for the overall ventilation system. The need of dedicated TEFs is also investigated in this study and a possible way of using TVFs for trackway exhaust is discussed.
This paper demonstrates that it is feasible to provide TVFs at only one end of station (only two TVFs per station) without compromising the basic functional and fire-life safety requirements. The design of the tunnel ventilation system shall be fully compliant with the NFPA 130 regulation. Further, TVFs (which is generally idle and used in emergency situations) were utilized in normal mode trackway exhaust operations by functional sharing and therefore dedicated trackway exhaust fans were removed. Finally, it was possible to reduce the number of fans from eight fans (4 TVFs and 4 TEFs) as in conventional system to only two fans which led to significant savings in space and associated cost. Finally, redundancy analysis is also undertaken to demonstrate that loss of one fan doesn’t lead to loss of performance of ventilation during fire scenarios.
This study also provides a cost analysis to show the savings achieved in Chennai Metro Phase 2, project India. These savings are achieved by optimising the civil space, number of fans, connected electrical load and cables of this project.
