Escape doors in the endurance test
The new Gotthard Base Tunnel must meet the highest safety requirements. This starts with the large doors that divide the rail tunnel into fire sections and the 350 doors in the "cross passages" that ensure evacuation in the event of a fire. These doors must withstand over 7 tons of wind pressure and also withstand a 90-minute fire. This cannot be done without safety testing of the material.
What happens when a train speeds past a door by just a few centimeters at almost 250 km/h? The doors have to withstand a change in air pressure and air suction every two seconds. This occurs due to the narrow gaps between the carriages and puts over 7 tons of pressure on the 1.6 wide and 2.2 meter high doors. In order to ensure that the 350 doors in the 175 cross passages of the tunnel can be opened at all times despite these extreme loads, new designs and test methods had to be developed, according to ift Rosenheim. For this reason, engineers from AlpTransit Gotthard AG, door manufacturer Elkuch Bator and experts from ift Rosenheim came together back in the summer of 2008 to develop appropriate testing and monitoring procedures that could simulate these extreme conditions in the tunnel.
Continuous load test
The doors were put through their paces, according to the testing, monitoring and certification body. Similar tasks had already been solved in the testing of ICE glazing or various roof glazing of freeway enclosures and various tunnels.
The continuous load test with a total of 500,000 pressure and suction surges at a frequency of two seconds had to be carried out at an ambient temperature of 40 degrees, which also prevails in the Gotthard tunnel. During the test, the enormous loads could be easily observed. Although the 110 mm thick stainless steel door leaves visibly sagged, they were still sufficiently tight after the 14-day continuous load test and could be opened with the required maximum force of 10 kg. The 8.5 m wide and 4 m high tunnel doors also had to meet special requirements because they divide the tunnel into several fire compartments. Therefore, despite a high air pressure, they were only allowed to have a minimum leakage rate for the passage of air in order to prevent the passage of smoke.
Resist 90 minutes tunnel fire
This major testing effort was necessary because the tunnel doors are a central component of the safety concept: the cross passages serve as escape routes in the event of train disruptions and for evacuation in the event of accidents - in extreme cases also in the event of fire disasters. In normal operation, the doors not only ensure compartmentalization, but must also withstand a tunnel fire for 90 minutes to prevent the fire from spreading into the cross passage and thus into the parallel tube. Despite this extreme load, it must be possible to open the door manually and intuitively from both sides with a maximum of 10 kg of force within five seconds at any time if necessary.
The approach to this project execution is costly and time-consuming, but ensures that in extreme cases and with proper maintenance, the doors will still fulfill their security purpose after 25 years, emphasizes ift Rosenheim.
