A road tunnel in difficult geology with cross-sections up to 300 m2 / Straßentunnel in schwieriger Geologie mit Querschnitten bis zu 300 m²

The 4.2 km Eyholz tunnel is part of the autobahn A9 and is the essential element in the bypass of Visp in the canton Valais, Switzerland. The tunnel passes through geologically problematic and also tectonically highly stressed zones (Rhone-Simplon fault).
The excavation of the two two-lane bores is being performed conventionally, by blasting and also in loose material. The interesting structures include the underground junction caverns, where slip roads to join and leave the autobahn are included in the tunnel, resulting in cross-sections of up to 300m² having to be excavated.
The overburden areas near the portals were excavated with tunnel excavators under the protection of elaborate jetted canopies. The two tunnel bores are being excavated in parallel and are connected with crosscuts every 270 m. As is typical for recent Swiss autobahn tunnels, a service duct is constructed under the carriageway. The inner lining of the main bores is progressing at the same time as the excavation and also the lining of the cavern with in-situ concrete. The first bore should open for traffic in 2013.