The ElbX construction project, a tunnel around 5.2 kilometers long, is a central component of the SuedLink grid expansion project of the two transmission system operators TenneT and TransnetBW. SuedLink is a 700 km long high-voltage direct current transmission line from Wilster and Brunsbüttel in Schleswig-Holstein to Bergrheinfeld/West in Bavaria and Großgartach/Leingarten in Baden-Württemberg. The crossing of the Elbe is being realized by ARGE Tunnel ElbX, consisting of PORR and Wayss & Freytag, on behalf of TenneT.
The tunnel boring machine's journey from southern to northern Germany
After factory acceptance at the Herrenknecht plant in Schwanau, the tunnel boring machine set off for northern Germany in six parts on September 20. Due to the size of the TBM, a great deal of planning was required for the ideal delivery route. Due to the proximity of the manufacturer and the construction site to the water, delivery by ship was chosen. On September 30, the TBM arrived at the Peters shipyard in Wewelsfleth, Schleswig-Holstein, approx. 2 km from the construction site, and was transported to the construction site by heavy goods vehicle.
Cutting wheel: the heart of the tunnel boring machine
The Mixshield tunnel boring machine (also known as a slurry TBM), which was specially developed for the project, has a cutting wheel with a diameter of 4.94 meters. It is the heart of the TBM and is designed for a passage of approx. 5200 m in various geologies.
Cutting disks/rollers are used to drive through the diaphragm walls at the beginning of the start shaft in Schleswig-Holstein and at the end of the target shaft in Lower Saxony. They are also responsible for overcoming stony obstacles and boulders along the way. 36 peeling blades loosen the loose rock (sand, gravel, clay) between the tracks of the discs. Scrapers arranged on the outside of the cutting wheel transport the loosened material through cutting openings into the excavation chamber.
Precision in the assembly of the cutting wheel
Due to the diameter, the cutting wheel could be supplied as a complete component. The assembly of the cutting wheel is a complex process that requires maximum precision and expertise. In order to connect the cutting wheel to the front shot, the cutting wheel had to be lifted by crane and positioned precisely so that the bolts and screws could be set exactly. Once fully assembled, the TBM will be around 190 meters long, which is roughly the length of a seven-car ICE train.
Final spurt for the starting pit
For the assembly of the tunnel boring machine, the launch pit, which was completely flooded for the wet excavation, had to be drained and braced piece by piece. In the last few weeks, the fourth and final bracing layer was constructed and the excavation pit was drained. In the coming weeks, the shaft will be prepared for the installation of the TBM: A steel construction, the so-called shield cradle, will be used, which will enable precise assembly and alignment of the front part of the TBM (shield with cutting wheel) in the entry area.
