Feldkirch tunnel reaches breakthrough at underground roundabout

Excavation has broken through in the underground roundabout of the Feldkirch city tunnel, a milestone in what is set to be Austria’s first underground roundabout, ORF Vorarlberg reported.

The breakthrough took place on 31 October, about one kilometre inside the mountain from the Felsenau portal. The roundabout is planned to connect to the road network through four tunnel branches.

Because of the main tunnel’s large cross-section, excavation is being carried out in stages: first the upper section, or crown, then the middle section and finally the floor. The breakthrough was achieved in the crown; work on the other sections will come later.

The roundabout is 182 metres long and has an outer diameter of about 70 metres. Around 160 blasts, using nearly 33,000 kilograms of explosives, were needed to excavate the ring tunnel. Project construction manager Klaus Eder said favourable geological conditions helped the team make good progress.

Excavation of the main tunnel began on 6 March 2026 and is expected to continue until autumn 2028. The 893-metre Felsenau branch and its parallel escape and rescue tunnel were fully excavated in early September.

The current construction stage includes the roundabout and its connection to the Tisis branch, a machinery cavern for ventilation and electromechanical equipment, an inclined shaft and the Altstadt branch. About 150 metres have been excavated in the Tisis branch. Next, crews will widen the Altstadt branch and then excavate the ventilation cavern. The stage is due to be completed by September 2027.