Gotthard Base Tunnel
The Gotthard Base Tunnel consists of two 57-kilometres-long single-track tubes. These are connected together every 325 metres by cross passages. Including all cross-passages, access tunnels and shafts, the total length of the tunnel system is over 152 km. It joins the north portal at Erstfeld to the south portal at Bodio. With a rock overburden of up to 2300 metres, the Gotthard Base Tunnel is also the world's deepest railway tunnel constructed to date.
Multifunction and emergency stop stations
Two multifunction stations at Faido and Sedrun divide the two tubes into three approximately equally long sections. The multifunction stations each contain emergency stop stations and two track crossovers. In case of an incident such as a fire in the train or a fault in the Gotthard Base Tunnel, whenever possible the affected train travels out of the tunnel into the open air. If this is not possible, the driver stops the train at an emergency stop.
Subdivision into sections
For construction purposes, the Gotthard Base Tunnel was subdivided into various sections. Access adits provided access to the underground construction sites for workers, materials and machines. To save time and costs, construction work proceeded on the various sections simultaneously. For construction of the Sedrun section, access from the surface was through a 1-kilometre-long horizontal access tunnel and two 800-metres-deep vertical shafts. From there, the two tubes were blast-driven to the north and south. Because the deep overburden and high stresses threatened to deform the tunnel, special supporting means were necessary in some places. The engineers developed an innovative new concept with flexible steel rings which partly closed under the rock pressure and thereby prevented deformations in the completed structure.
The historic moment
The first final breakthrough of the Gotthard took place on October 15, 2010, at 2.17 pm in the east tube at a distance of around 30 km from the south portal and 27 km from the north portal. The breakthrough took place with great accuracy: a deviation of only 8 cm horizontally and 1 cm vertically.
80% of the drive in the main tubes was cut by tunnel boring machines, 20 % by conventional drilling and blasting. A total of 28.2 million metric tons of excavated rock was transported out of the tunnel.
Work outside the tunnel
Besides the tunnel itself, numerous built structures such as underpasses and bridges are required for the tunnel approaches. The overground section in the Reuss valley in the canton of Uri crosses inhabited areas, roads, rivers and agricultural land. Protective measures against noise, dust, and floods, and for nature conservation, are therefore equally important challenges as the technical implementation of the new railway line.
Opening of the Gotthard Base Tunnel is scheduled for December 2016.