ABSTRACT
The double bore tunnel for under passing Bologna has connecting tunnels (bypass) at most every 250 m. In order to consider one tunnel a safe place compared to the other, safety system has been studied to prevent in fire scenarios the smoke passing from one tunnel to the other. The system has the following subsystems: bidirectional, auto-closing, fire and pressure resistant doors, system for door position detection, pressurization system (fans), real time supervision/control. The main design issue described in the paper are the design of bidirectional fire and pressure resistant doors, the pressurization system in order to guarantee an adequate overpressure or air flow in the bypass depending on the position of the doors (closed or open) by setting the operating rotation speed of fans. The system has been developed and built for the first time in the Bologna twin tunnels (2012) and nowadays is the basis for new application.
