Deutsche Bahn (DB) and the Elleringhauser Tunnel Consortium, comprising construction companies Max Bögl GmbH and Marti GmbH Deutschland together with Marti Technik AG of Switzerland, have been renovating the 1,4 km Elleringhauser Tunnel on the Upper Ruhr Valley Railway in North Rhine-Westphalia since 2022. Built in 1872, the tunnel requires significant renovation and widening to maintain the necessary clearance profile for modern train services. The project is expected to continue until 2029.
The project uses high-end drive technology from RUD Ketten. For a specialised cutting assembly designed to cut the tunnel wall into conical sections, Marti Technik AG uses several Tyrolit saw blades with a diameter of up to one metre, and for their curved movement, the saw blades are each driven by a Tecdos Omega Drive TEC 25 from RUD with a diameter of 50 mm. As the two-part cutting apparatus can also be moved 13 metres in the longitudinal direction, four Tecdos Omega Drive TEC 12, 40 mm, chain drives are used. For both the arc movement and longitudinal travel, the Tecdos Omega drives run along the corresponding RUD Premium chains, the TEC 25 and TEC 12 respectively.
Masonry over 150 years old
Due to its age, the Elleringhauser Tunnel is being both renovated and widened to maintain the required clearance profile for trains, including the new outer and inner linings. To ensure that train services on the Upper Ruhr Valley Railway between Aachen and Kassel can continue during the day while renovation work is underway, the tunnel-in-tunnel method is being used. A protective enclosure safeguards regional trains as they pass through while work continues on the tunnel wall.
A unique tunnelling portal
The cornerstone of the project is a tunnelling portal developed specifically for the Elleringhauser Tunnel. At 45 metres long, it incorporates two cutting units with multiple saw blades, mounted on the outer skin in such a way that they enable cuts up to 50 cm deep to be made into the tunnel wall while travelling along a conical arc. Marti Technik AG developed the tunnelling portal for the project, drawing on experience from previous tunnel-in-tunnel projects, with development and manufacturing costs exceeding two million Euros.
Protection for the trains
The tunnelling portal has been in use on the construction site since February 2025. “We carry out the cutting work during the day. The tunnel-in-tunnel method allows us to make the necessary cuts between 6:00 and 19:30, and thanks to the protective enclosure, regional trains can pass through without any risk,” says site manager Erich Merkle of the EET consortium. Up to 70 trains pass through the tunnel-in-tunnel each day. From around 19:30, the tunnelling unit makes way for a construction train equipped with excavators and other machinery. The excavators break up the old tunnel lining, cut into sections, piece by piece, and load the excavated material onto construction trains. The exposed section is then secured with steel mesh and shotcrete.
One year of development
It took a year to develop the cutting device, a project led by design engineer Thomas Hofer at Marti Technik AG. “We had already used RUD drive components in previous designs, so it was clear that Omega-Drive units could again provide the ideal solution,” says Hofer. The chain-driven RUD solution was preferred over alternatives for good reason. The Omega-Drive units are protected from dust, dirt and water ingress by their housing, and RUD’s TEC Premium chains are extremely robust. “That is a clear advantage over a rack and pinion system. We quickly ruled that out because it did not seem robust enough,” says Hofer. Another deciding factor was the ability to combine linear and radial motion. “This causes the distance between the sprocket and the round steel chain to change. With the RUD drives, we can always guide the chain so that the theoretical dimension is consistently maintained.”
Positive experience in practice
After each radial cut, the two cutting units move longitudinally to allow the next cut. This simplifies the subsequent demolition work carried out at night. “The combination of the enclosed deflection drive and the robust chain is outstanding. After all, we are cutting wet, so there is a corresponding amount of spray mist. We are very satisfied with the solution,” says Merkle.
Designed for extreme loads
“This example demonstrates that when it comes to demanding infrastructure projects under extreme operating conditions, you can rely on our high-performance drive solutions,” says Tobias Rathgeb, area sales manager at RUD Conveyor and Drive Technology. RUD’s Omega-Drive drives are developed for extreme loads and offers a long service life.
With its characteristic 180-degree wrap angle, the Tecdos Omega Drive is suitable for both linear and rotary movements. Depending on the application, the drive either attaches to the load and pulls it along the round steel chain, or is fixed in place and moves the chain along with the load. Particularly compact, the drive consists of three idler wheels arranged in a triangle. The drive wheel operates free of external forces, and the drive generates no reaction forces. The chain is guided through the drive via an integrated chain guide, resulting in the 180-degree wrap angle.
For more information contact RUD Ketten Rieger & Dietz,
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