Gotthard Base Tunnel, LOT 252 Amsteg - LOT 151 Erstfeld

The Gotthard Base Tunnel, located in the Alps, serves as a crucial transit route connecting Austria and Switzerland. This tunnel holds the distinction of being the world's longest railway tunnel, spanning an impressive 57 kilometers in length. STRABAG, as a contractor, was awarded the responsibility for constructing two significant sections within the tunnel: the Amsteg and Erstfeld tunnels.

Scope of work

Lot 151 Erstfeld

• 600 m of cut & cover
• TBM excavation of 2 single track tubes; L = 7.2 km / D= 9.55 m
• D&B excavation of 24 cross passages
• D&B excavation of the 2 underground tunnel branching caverns and tunnels
• Waterproofing membrane installation
• Tunnel and cross passage concrete inner lining

Lot 252 Amsteg

• TBM excavation of 2 single track tubes; L = 10.7 km / D = 9.55 m
• D&B excavation of 37 cross passages
• 650 m D&B excavation of 2 single track tubes, tunnel branching caverns and logistic galleries
• TBM excavation of the 1,884 m cable tunnel, D = 3.7 m
• D&B excavation of the assembly caverns
• Waterproofing membrane installation
• Tunnel and cross passage concrete inner lining

Project Description

The initial phase involved using the drill and blast method to excavate each tunnel tube, allowing for the subsequent assembly and installation of tunnel boring machines (TBMs). These TBMs played a pivotal role in excavating the primary segments of the tunnels, with Amsteg measuring 2 x 7.8 kilometers and Erstfeld spanning 2 x 11.3 kilometers. Notably, STRABAG served as the sole contractor for this project, successfully completing one-third of the extensive 57-kilometer tunnel, demonstrating its capabilities in handling complex infrastructure projects.

The project's magnitude is underscored by the excavation of 2,765,000 cubic meters of material and the utilization of 880,000 cubic meters of concrete. These tunnels reached depths of up to 2,100 meters and faced challenging conditions, including temperatures of up to 46°C during TBM operations in the Amsteg section. STRABAG's successful execution of these tunnel contracts demonstrates its expertise in handling intricate and demanding infrastructure projects on a global scale.

Project Highlights:

• Excavated rock treatment and reused as a shotcrete and concrete aggregate
• Building of artificial islands in Vierwaldstätter Lake from not usable excavated rock (not carried out by STRABAG)
• 2,765,000 m3 of excavated material
• 880,000 m3 of concrete used to line the tunnels
• 900,000 m2 of water-proofing membrane installation
• 600 people employed during project peak
• Best TBM performance values: 56 m/day – 688 m/month
• Construction of 61 cross passages (Erstfeld and Amsteg) between the tunnels
• Construction of two branching underground caverns and tunnels for the future “Berg lang geschlossen” at Lot Erstfeld
• 2,100 m of maximum overburden
• 46 °C of maximum temperature in the tunnel on the TBM in Lot Amsteg
• Up to 120 m exploration drilling from the TBM ahead of tunnel face and continuous seismic exploration ahead of the tunnel face
• Deployment of Rowa suspended working platform for the cross passages excavation to enable undisturbed TBM heading
• Use of “Monorail Train” suspended on the tunnel roof for the material logistic on the TBM – considerable innovative solution