Enlargement of the Fachinger Tunnel Successfully Completed
Between Diez and Fachingen, Porr is upgrading the 426 m long, double-track Fachingen Tunnel, which dates back to the 19th century. On behalf of Deutsche Bahn, Porr is working in a consortium with Feldhaus Bergbau GmbH & Co. KG and Heinz Schnorpfeil Bau GmbH. The tunnel cross-section has to be widened in order to guarantee the prescribed clearance gauge. In addition, the track spacing will be increased to 4 m. The enlargement is being carried out using the tunnel-in-tunnel method. On November 21, 2024, the tunnel enlargement system (TES) “Nora” breached the breakthrough wall of the Fachinger Tunnel. This milestone marked the end of the 380-metre-long conventional widening of the 160-year-old tunnel during ongoing rail operations.
On November 21, 2024, the “Nora” tunnel enlargement system breached the breakthrough wall of the Fachinger Tunnel
Credit/Quelle: Porr
The prevailing rock properties presented the tunnelling team with particular challenges. In order to cope with the changing geology of clay shale and keratophyre throughout the entire excavated cross-section, occasional blasting to loosen the rock was necessary during the excavation work. The excavated material fell next to the TES and was then removed by conveyor equipment. During the entire construction work, rail traffic continued to run safely under the protection of an enclosure on a newly laid track in the middle of the tunnel.
The Enlargement Work Is Followed by Concreting
Demolition of the breakthrough wall
Credit/Quelle: Porr
The tunnelling team after the successful breakthrough
Credit/Quelle: Porr
After the breakthrough, “Nora” is pulled back to the site installation area. During this process, the sealing support is sprayed, the foundations are excavated, the blinding layer is concreted, drainage is installed and the foundations are concreted. As soon as the tunnel enlargement system has reached the installation area, it is dismantled. The concreting train is then lifted in to concrete the vault of the inner shell in cycles.
The narrow construction site in the local area and working while the railroad is in operation present particular challenges: “Due to the confined space in the tunnel, we can only use small machines that run on specially laid foundations and rails. In addition, great importance is attached to protecting the water in the catchment area of the 'Fachinger Brunnen' in Fachingen. That's why the monitoring is carried out precisely to the minute using state-of-the-art monitoring equipment,” says Folker Popp, Project Manager Tunnel Construction at Porr, explaining the special features of the construction site.
