Since January, two Herrenknecht Tunnel Enlargement Systems (TES) have been working on Deutsche Bahn’s 426m-long Fachingen Tunnel and 732m-long Cramberg Tunnel – without affecting rail services.
The tunnels are part of the Lahn Valley Railway connecting the cities of Koblenz and Wetzlar. The enlargement is being carried out by a consortium of Porr GmbH & Co, Feldhaus Bergbau GmbH & Co, and Heinz Schnorpfeil Bau GmbH.
The TES developed by Herrenknecht makes it possible to carry out tunnel renewal during ongoing rail operation. First the existing tracks are dismantled, and a track is laid in the middle of the existing tube. Rail traffic continues to run on the track throughout the construction period as the TES serves as a protective enclosure and separates the construction work from rail traffic.
For the two double-track tunnels of the Lahn Valley Railway, the radius of the tunnel cross-section will be enlarged by 2m, bringing them in line with modern tunnels.
The approximately 46m-long, 270-tonne TESs for the Fachingen and Cramberg tunnels have a diameter of around 12m. They run on foundations and rails laid in the tunnel and are equipped for conventional excavation and support work. Depending on the hardness of the rock, excavation is done by chiselling or blasting.
First, the old tunnel walls are broken out and rock is excavated. The excavated material falls to the side of the machine into the tunnel invert and is removed by separate conveyor and loading equipment. After each drilling and blasting round, a shotcrete manipulator applies the temporary shotcrete support. The rock is also stabilised with anchors. Reinforcement mesh and steel arches, together with the shotcrete and anchors, form the initial support.
Once tunnelling with the TES has been completed, the final lining of the tunnel is applied using in situ concrete.
The TES comprises three parts. The front is used for pre-excavation protection. It prevents the existing tunnel from collapsing in the area ahead of the excavation work or rock falling onto the tracks. The middle section carries the equipment required for tunnelling: telescopic drill rigs on both sides, hydraulic impact hammer on a central boom with a large radius of action, shotcrete system on a ring guide. The machine has large, retractable working platforms that allow the workers to safely reach the tunnel face and the intrados. The rear holds the equipment for operating the TES. This includes a hydraulic station to supply the hydraulically driven equipment, a compressor for the supply of compressed air, the electrical system, and a material storage.
The TES design for the Lahn Valley Railway drew on experience from the first use of a TES in Spain. Renovation of the 558m-long Gaintxurizketa Tunnel between Astigarraga and Irun in the foothills of the Basque Pyrenees was completed in March this year. The renovated tunnel will improve the connection between the Spanish and French rail networks as part of the EU’s future Atlantic corridor.
