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Pictures of the Future
The Magazine for Research and Innovation

The new Gotthard Base Tunnel

The Ultimate Tunnel

When all of its shafts, cross-passages and access tunnels are added together, along with its two tunnel tubes, the Gotthard Base Tunnel has a total length of 57 kilometers.

The Gotthard Base Tunnel is the centerpiece of the new transalpine route for rail transport into and through Switzerland. The Base Tunnel’s length of 57 kilometers makes it not only the world’s longest rail tunnel but also a prestige project that showcases the prowess of engineering. In the future, about 200 trains are expected to race through the tunnel every day at speeds of over 250 km/h. Siemens is ensuring a high level of safety inside the tunnel through measures such as sophisticated fire protection solutions.

Getting from Zurich to Milan in three hours — until now that has been an unattainable dream. For years, rail travelers have had to cope with a tunnel under the Gotthard massif that is known as a time-consuming bottleneck. But in early June 2016, all of that will change with the opening of the new Gotthard Base Tunnel. This mammoth construction project, which took 17 years to complete, is not just any tunnel. It’s a showpiece of state-of-the-art tunnel engineering, the longest and deepest railroad tunnel in the world, and the centerpiece of Switzerland’s mammoth New Railway Link through the Alps (NRLA) project.

The gigantic tunnel has been dug through 57 kilometers of solid rock from its north portal in the town of Erstfeld in the canton of Uri to its south portal in Bodio in the canton of Ticino. Since the first controlled detonation in 1999, more than 28 million metric tons of rock have been removed in order to make room for the project’s two single-track main tubes as well as the safety, ventilation, and transverse tunnels. It’s a prodigious achievement.

Travel time from Zurich to Lugano will be shortened by 45 minutes to about two hours. The trip to Milan will be shortened to three hours.

Even the bare figures illustrate the huge difference between the new Gotthard tunnel and the old one. Today, passengers traveling through the old tunnel toward the southern Alps are frustrated by the train’s slow ascent as it reaches an altitude of 900 meters above sea level. During the ride, the passengers have “only” 1,100 meters of rock above them.

Saint Barbara, the patron of miners, keeps watch over the tunnel.

Compared to the new base tunnel, that’s a relatively modest statistic. The new tunnel lies no more than 550 meters above sea level and has very gentle gradients and no tight curves. However, travelers will have 2,300 meters of solid rock above their heads. That might make some people uneasy, but taking this route will be worthwhile because it will reduce the travel time from Zurich to Lugano by 45 minutes to about two hours and shorten the trip to Milan to three hours.

Coolest Construction Site in Switzerland

Travelers and technicians alike are enthusiastic about these figures, not only in rail-focused Switzerland but also abroad. In fact, according to Marco Pradera from Siemens Building Technologies (BT), the overall project manager who supervised the construction of the tunnel’s fire protection measures, the new tunnel is the “coolest construction site” in Switzerland.

Tunnel travelers will have 2,300 meters of solid rock above their heads.

As he tells it, “It has not been an easy project, not only with respect to the technology but also because many companies are conducting many subprojects in parallel as part of the construction process. There were already some surprises as early as the detailed calculation phase, and quite a few more cropped up during the on-site implementation phase.” However, Pradera enjoys a challenge. “I like projects like this one, where you need to work closely with the customer to find the best solution,” he says. “That always works. Standard projects are not really my thing.”

Safety at 250 km/h

It’s obvious that safety in the tunnel is of paramount importance. After all, in the future more than 200 trains per day will race through the tubes at speeds of up to 250 kilometers per hour. The two tubes are connected with cross-cuts at 300-meter intervals so that in case of fire passengers can escape to the other tube. “The real danger would not be from the fire itself but rather from suffocation,” Pradera explains. In the case of an emergency, it would be possible to evacuate up to 1,000 people at the two 600-meter-long emergency stop stations in each tube. However, to prevent such an emergency from ever taking place, Siemens has equipped the tunnel with countless sensors as well as surveillance and control devices that are connected with two control centers at the tunnel’s north and south portals by thousands of kilometers of fiber-optic cables. Thanks to this system, even the slightest danger signal will trigger an alarm so that precautionary measures can be taken.

Fire Detectors in Cages

Sophisticated Siemens technology for identifying fire sources has also been installed at the four emergency stop stations. It operates with three different detection systems, and in case of a pending evacuation it directly activates the ventilation flaps. Surveillance data is checked and recorded every few milliseconds by the control system. In this way, an entire event can be tracked and activation parameters can be optimized.

One special feature of the system was the installation of FibroLaser heat detection technology from Siemens. “This foolproof technology can identify and localize fires quickly,” says Pradera. “In addition, it automatically activates the tunnel reflex processes, such as its exhaust ventilation. The technology opens the right exhaust ventilation flaps so that the smoke above a fire source can be vacuumed off in a concentrated way while the other flaps are closed. This prevents the smoke from spreading into the 600-meter-long emergency stop station and the tunnel tubes and ensures a smoke-free environment for fire fighters and the evacuation of the passengers.” Pradera’s team installed the FibroLaser cables in the ceiling and the floor of the Gotthard Base Tunnel. In both locations, the technology can detect the first signs of danger. “For example, a stuck train wheel or a leaking liquid could catch fire,” Pradera explains.

The FibroLaser system is supplemented by thermal imaging cameras and smoke detectors, which continuously monitor the temperature and check for the presence of smoke particles. To protect them from the harsh conditions inside the tunnel, the cameras and smoke detectors are located in cages. This too is a feature specially designed for the Gotthard Base Tunnel. All of these features are geared to the requirements of trains that can travel as fast as 270 km/h. This means the system can handle trains that are even somewhat faster than today’s.

FibroLaser not only quickly identifies and precisely localizes fires but also independently activates the exhaust ventilation system.

Lifesaving Backpacks

Work on the Gotthard project was by no means easy. Workers first had to take the hot-weather test and the stress ECG that are required by SUVA (the Swiss accident insurance fund). After that, every worker had to complete a safety training course. Only graduates of the course can enter the gigantic construction site, always wearing safety clothing with reflecting strips, a helmet, chunky mountain boots, and a 15-kilogram backpack. The backpack contains a “lifesaver” consisting of a facemask, a balloon, and an oxygen tank that will enable the wearer to survive for 50 minutes in a smoke-filled environment. It also contains a radio unit, a notebook computer, a lamp, ear protectors, a wind deflector, a folder with writing materials, and enough food and beverages for an entire day spent working at 40 degrees Celsius, because for many workers the nearest supply station might be many kilometers away. In the morning a train brings the workers to their underground workstations. Only in the evening does the train take them back above ground.

Home Stretch

In October 2015 the overhead lines were switched on and the extensive train testing phase began. The dates for further work, such as cleaning the cameras and optimizing the parameterization, must be applied for 28 days in advance, and the work has to be done at night. “In such cases, long-term planning is an advantage. Fortunately, we now also have a remote access system, so in many cases we can optimize our systems from a distance,” Pradera says.

He emphasizes that he is proud to be part of this project, even though he admits that “I was always glad to get out of the noise and dust in the evenings. It was hard to get to the workstations, and the air was bad. It’s very exhausting to work underground.” During the summer, it helped to be able to cool off with a swim in the cold waters of Lake Urnersee and have a glass of cool “Stiär Biär”, the local beer brewed in the canton of Uri.

When regular rail transport through the Gotthard Base Tunnel begins in December 2016 after thousands of test runs, Pradera, the construction technology expert, will be able to slow down a bit. Will he ever take a train ride through the tunnel himself? “I can’t rule it out, but whenever possible I prefer to cross the mountains above ground,” he says. “But I don’t do that for safety reasons. It’s just because that way you can see more.”

Catharina Bujnoch / Sebastian Webel
Picture credits: from top: 2. picture AlpTransit Gotthard AG, 5. picture AlpTransit Gotthard AG