Gotthard Base Tunnel

FACTSFact sheet

01A mountain that had already charged a high price

The first Gotthard tunnel, between Göschenen, in the canton of Uri, and Airolo, in Ticino, was dug from 1872 to 1882. It cost a number of lives on which not even the sources agree: 171 on the list of victims cited by the Swiss National Museum, 177 or 199 in other counts. Dynamite, dust, malnutrition, typhoid and worm infections were all part of the toll. The engineer and contractor Louis Favre died of a heart attack inside the tunnel in 1879, before the two sides met.

That tunnel sits high up. To reach it, the line climbs on ramps and spirals, and freight trains need an extra locomotive. The idea of a base tunnel, dug at the root of the mountain and almost level, appears in drawings from 1947. It became a project when the Swiss approved the New Rail Link through the Alps, in 1992, and it became money in November 1998, with a fund paid mostly by a charge on heavy trucks. The road itself began paying for the train that would take freight off it.

02Five fronts at once

Digging 57 kilometers from the two ends alone would take far too long. AlpTransit Gotthard split the work into five sections and attacked them all at once: from the Erstfeld and Bodio portals, through access tunnels at Amsteg and Faido and, in the middle of the mountain, through two vertical shafts of about 800 meters at Sedrun, in the canton of Graubünden. Shaft 1 began to be sunk in August 1998.

Four Herrenknecht tunnel boring machines, machines more than 400 meters long with cutterheads of 9.4 to 9.6 meters, dug most of the tubes. In 2009, Gabi 2 advanced 56 meters in 24 hours, a record for a machine of that size in hard rock, according to the manufacturer. Where the rock was too soft for a machine that braces itself against the walls, the tunnel was opened by blasting.

03The water that might be there

For decades, geologists argued about the Piora syncline, a band of dolomite in the tunnel's path. Some experts were convinced that crossing it would be practically impossible. Between 1993 and 1996, the exploration cost about CHF 100 million, according to AlpTransit's own engineers.

In March 1996, a borehole drilled from a gallery some 350 meters above the future tunnel struck crumbling dolomite under high water pressure. The mixture flooded the gallery and, within a few hours, the road in front of it. Nineteen boreholes later, totaling 7,000 meters, the answer came: at tunnel level, the rock was solid and dry. The tunnel boring machines crossed the Piora without trouble, the one in the east tube in October 2008 and the one in the west tube in January 2009.

04Letting the mountain squeeze

The most feared stretch lay north of Sedrun, in the Tavetsch intermediate massif. There the tunnel had to cross just over a kilometer of rock crushed by geological faults, the so-called kakirites, under 800 meters or more of mountain. In laboratory tests, this rock proved highly ductile and took up much more volume as it fractured. It does not collapse like stone: it creeps slowly into the hole, like a paste under pressure. A similar problem had already appeared in the Gotthard road tunnel, in the 1970s.

A rigid support would have been crushed. The solution, developed by the design engineers together with AlpTransit, combined two practices that had never been used in those conditions: yielding steel rings, borrowed from mining, and full-face excavation with a heavily reinforced face, in the Italian manner. The tunnel was dug bigger than it needed to be, up to about 13 meters in diameter, and fitted with two concentric steel rings with sliding joints. The mountain squeezed, the rings gave way, and the hole closed on purpose, with a planned convergence of up to about 70 centimeters, before receiving its final concrete lining, up to 120 centimeters thick.

The principle, in the engineers' words, is that the more the ring yields, the less force is needed to hold back the mountain. Before applying it, the team tested the rings at full scale in a side gallery at Sedrun, simulating the rock pressure with water-filled cushions, and found that the behavior predicted in theory was not repeated in practice. Measured afterwards, the deformation averaged 25 centimeters and reached 85 at asymmetric points, according to a survey by the Swiss Geotechnical Society. The stretch was conquered between 2004 and 2007, more than half a year ahead of schedule.

05Eight centimeters

On October 15, 2010, the tunnel boring machine Sissi broke through the last wall of rock in the east tube, between Sedrun and Faido. The two sides, dug toward each other for years inside the mountain, met with a deviation of 8 centimeters horizontally and 1 centimeter vertically. The tolerance was 25 centimeters. In the west tube, the last breakthrough came on March 23, 2011.

Five years of track, overhead lines, ventilation and safety systems followed. On May 31, 2016, the day before the celebrations, about 50 people gathered at the north portal to unveil a bronze plaque bearing the names of the nine workers who died on the project, between 2002 and 2012. The next day, the tunnel was opened in front of heads of government from neighboring countries. Commercial trains began running on December 11.

06One car, one wheel, one year

On August 10, 2023, part of a wheel on the 11th car of a freight train running from Chiasso to Basel came loose just after the south entrance. Kilometers further on, the axle destroyed a switch at the Faido multifunction station, and 16 cars derailed. The tunnel was completely closed for two weeks; then one tube went back into service, and the other was only reopened on September 2, 2024. The final report of the Swiss accident investigation body, from June 2025, pointed to fatigue in the wheel disc after overheating, probably caused by a stuck brake.

In May 2026, an opinion from the Ticino prosecutor's office, reported by the Swiss press, argued that SBB's operations center could have prevented the worst; SBB rejected the accusation. Around the same time, the company switched on derailment detectors at about ten points before the tunnel entrances. On June 1, 2026, the tunnel turned ten: the number of passengers per day had almost doubled since 2015, and freight carried reached 24.2 million tonnes in 2025.

MYTHSWhat people say and what the record shows

• What people say

  It is the longest tunnel in the world.

  What the record shows

  It is the longest railway tunnel in the world, at 57 kilometers. The title applies to rail tunnels.

• What people say

  It cost twice what was planned.

  What the record shows

  The official CHF 9.7 billion is at 1998 prices, without the tax increase and without the interest on the project; the CHF 12.2 billion is the actual cost. The two figures do not measure the same thing.

• What people say

  The two sides met with an error of millimeters.

  What the record shows

  At the main breakthrough, in 2010, the deviation was 8 centimeters horizontally and 1 vertically. The millimeters (4 and 8) belong to the Amsteg breakthrough, in 2009, according to the maker of the tunnel boring machines.

• What people say

  A modern project like this killed no one.

  What the record shows

  Nine workers died, according to AlpTransit Gotthard itself, which dedicated a plaque to them at the north portal in 2016.

QUESTIONSFrequently asked questions

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SOURCESSources

1. Swiss Confederation (Bundesamt für Verkehr / gottardo2016.ch), "The Gotthard Base Tunnel", brochure, 2015 — newsd.admin.ch
2. Rupert Lieb and Heinz Ehrbar (AlpTransit Gotthard), "Gotthard Base Tunnel: Risk Management for the World's Longest Railway Tunnel", World Tunnel Congress, 2011 — heinzehrbarpartners.com
3. Swiss Geotechnical Society, "Gotthard Base Tunnel", ISSMGE Heritage Time Capsule, 2024 — htc.issmge.org
4. Herrenknecht AG, "Gotthard Base Tunnel" reference — herrenknecht.com
5. tunnel magazine, "Gotthard Base Tunnel: High-accuracy at final breakthrough", 2010 — tunnel-online.info
6. Tunnels & Tunnelling, "Sedrun – Gotthard's toughest challenge", 2004 — tunnelsandtunnelling.com
7. AlpTransit Gotthard AG, press release on the memorial ceremony for the workers who died, 31/05/2016 — alptransit.ch
8. SRF, "Gotthard – Die Schattenseite des Jahrhundertbauwerks", 2016 — srf.ch
9. Luigi Jorio, "Engineers meet challenge of Gotthard tunnel", swissinfo.ch, 2014 — swissinfo.ch
10. swissinfo.ch, "Broken wheel caused Gotthard Base Tunnel derailment, report confirms", 2023 — swissinfo.ch
11. Keystone-SDA, "SBB installiert Entgleisungsdetektoren vor dem Gotthard-Basistunnel", nau.ch, 12/05/2026 — nau.ch
12. Luigi Jorio, "The Gotthard Base Tunnel ten years on", swissinfo.ch, 2026 — swissinfo.ch
13. Swiss National Museum, "Vincenzo Vela's Victims of Labour memorial", 2023 — blog.nationalmuseum.ch

Images

• Fig. 01 — The cutterhead of tunnel boring machine S-210, Sissi, at Faido, days after arriving through the east tube, in September 2006. The same machine made the main breakthrough four years later: Cooper.ch · CC BY-SA 2.5
• Fig. 02 — The east tube at the Amsteg site, in August 2004, with the rock still exposed. The tunnel boring machine was already kilometers ahead: Daniel Schwen · CC BY-SA 2.5
• Fig. 03 — The Sedrun site, in October 2010, eleven days after the main breakthrough. From here, two shafts of about 800 meters went down to the tunnel: Markus Giger · CC BY-SA 4.0
• Fig. 04 — The Faido multifunction station under construction, in November 2014, with the two tubes and the temporary gates against the air draft. It was at this station that the train that derailed in 2023 destroyed a switch: Hannes Ortlieb · CC BY-SA 3.0 DE
• Fig. 05 — A EuroCity at the north portal, in Erstfeld, in November 2016, weeks before commercial trains began running: Zacharie Grossen · CC BY-SA 4.0
• Fig. 06 — Crowds during the opening days, in June 2016, by the south portal, when the first passenger trains went through the tunnel: Zacharie Grossen · CC BY-SA 4.0