Gotthard Tunnel Opens
In June this year Switzerland celebrated the opening of the Gotthard Base Tunnel and inaugurated it solemnly. But why are the Swiss so proud of a dark hole in a huge mountain? Let’s say this much: it’s a lot more than just our trains arriving earlier when we go on a shopping trip to Milan.
We all know that Switzerland is a small, but very mountainous country and even though the Alps are nice to look at and ski on, they are also an obstacle when it comes to traveling across the country to visit and do business with our neighboring countries. The opening of the Gotthard Base Tunnel therefore not only marks the inauguration of the world’s longest railway tunnel, but also a feat of engineering on a global scale that brings Europe closer together.
For a long time, experts on Alpine road construction considered the Gotthard terrain to be impassable. But since the region is strategically located as the ideal pathway to link north and south — in the middle of Switzerland, where four cantons meet (Graubünden, Ticino, Valais, and Uri) and four of the big Alpine rivers arise in all four directions (the Rhine, the Reuss, the Rhône, and the Ticino) — there had to be a way to pass through the mountain made of diverse rock strata, ranging from hard granite to partly crushed sediment.
After first attempting to pass over the Gotthard on roads and bridges, which was too risky and unstable in the end, the Swiss decided to drill a tunnel instead. Work on the first tunnel through the Gotthard began as early as 1872. As many as 5,000 workers, mainly from Italy, worked at the northern and southern portals — slowly digging their way deep into the heart of the massif, which got its very own name because of its special rocks: the Gotthard Massif.
The conditions for building a tunnel back then were extremely tough; no less than 199 workers lost their lives. Although not nearly as many workers died as for the first tunnel, the building of the Gotthard Base Tunnel still resulted in the deaths of nine workers.
The new Gotthard Base Tunnel is the centerpiece of the New Railway Link Through the Alps (NRLA). When the work for the new high-speed link started in 1999, new techniques had been developed and improved. To be able to build the Gotthard Base Tunnel, a high degree of precision in construction was required. Reliable and highly accurate surveying techniques make it possible for the route to be defined down to the exact millimeter. The exact geological conditions inside a mountain range are difficult to predict. The tunneling comprised the latest exploration techniques and test bores supported by forecasts from experienced geologists to keep risks to a minimum.
Ecology-Minded Tunneling
- The low-level Gotthard rail link will help to protect the ecosystem of the Alps. But even the construction itself was designed to be as environmentally friendly as possible to minimize the impact on people, animals, the air and water.
- Materials were primarily transported via conveyor belts, rail and ship, which kept air pollution low during the entire construction process
- Residents were protected from dust and noise by temporary topsoil embankments, noise barriers, and restricted operating hours on the construction sites
- To prevent the release of dust into the air, non-asphalted construction areas were irrigated and streets and vehicles were cleaned on a regular basis
- Mountain and tunnel water was processed and cooled before being reintroduced into rivers
- Cleared trees were replaced with habitat, streams were rehabilitated and riverbank areas were renaturalized
The Breakthrough
The final breakthrough of the Gotthard Base Tunnel took place in 2010, approximately 18.6 miles (30 km) from the south portal and 16.7 miles (27 km) from the north portal. The breakthrough was extremely accurate with a horizontal deviation of just 3.15 inches (8 cm) and a vertical deviation of 0.39 inch (1 cm), making it one of the most precise breakthroughs in the history of tunnel construction. Four tunnel-boring machines excavated almost 75% of the Gotthard Base Tunnel, with blasting used for the remaining 25%. The choice of tunneling method depended not only on the expected rock conditions, but also on development opportunities, environmental conditions and economic realities.
After excavating the rock, the tunnel bore was reinforced to prevent rock falls and to protect workers. Reinforcing elements of varying degrees of strength were used depending on the geological conditions. Anchors, shotcrete and steel arches were combined modularly. That was followed by the application of a sealing foil, which protects the tunnel bores from water ingress.
For the Gotthard Base Tunnel, appropriate systems were developed to meet the specific requirements and conditions. The interior lining of the tunnel, which serves as the supporting structure, must last for 100 years without significant maintenance work. Therefore the high quality and service life of the construction materials were of paramount importance.
Mechanical and electromechanical equipment such as an operational ventilation system was installed in the base tunnel before installation of the rail infrastructure. It supplies fresh air and smoke extraction in the event of fire. And a drainage system takes mountain water and contaminated water caused by accidents out of the tunnel through separate pipes.
Precise as a Swiss clock — on time and within budget — the Swiss pioneered their way through a massif once called impassable by applying the newest techniques and innovations in tunnel drilling and engineering not just to gain time and efficiency, but to protect the natural beauty of the Alps.
