The groundbreaking ceremony for the Elbe tunnel between Wewelsfleth and Wischhafen in September 2023 marked the start of one of the most important infrastructure projects for the SuedLink electricity highway – a joint project between the two transmission system operators TenneT and TransnetBW. On behalf of TenneT, PORR is realising the SuedLink Elbe crossing as part of the ARGE Tunnel ElbX consortium, contributing its entire expertise in tunnelling, structural engineering and special civil engineering.
Diaphragm walls up to 60 metres deep are a technical challenge
The target construction pit consists of a main construction pit for the shaft building and a smaller construction pit for the sleeve building. As the target shaft is located in groundwater, the construction pits must be watertight. With a thickness of 100 to 120 centimetres and a depth of up to 60 metres, the diaphragm walls for the main excavation pit were installed in the dense, load-bearing micaceous clay. The shoring is additionally reinforced with a steel structure to transfer the earth pressure loads. Slotting down to these depths requires maximum dimensional accuracy, as the joints must be absolutely tight and the construction pit completely closed. The smaller construction pit, which is only 5 metres deep, requires an underwater concrete base, which is additionally secured against buoyancy with micro piles.
The next construction phases are now underway with the production of the head beams, the well construction and the preliminary excavation. Completion of the construction pit is scheduled for summer 2025.
