“The SuedLink project is crucial for securing the power supply in Germany and we are proud to be contributing to this project. Drawing on our many years’ experience in tunnelling, PORR will play its part in completing the Elbe crossing on schedule,” said Karl-Heinz Strauss, CEO of PORR AG.
Germany has set an ambitious goal of sourcing at least 80% of its power from renewable energy sources by 2050 – which presents a challenge for the electrical grid, which must be adapted to the modified generation structure in order to ensure a stable and secure power supply in the future. The SuedLink project aims to transport primarily wind-generated power from northern to southern Germany. Two underground high-voltage direct current (HVDC) transmission cables will be able to transmit up to 4 GW across Germany.
A challenge of renewable energy, however, lies not only in distributed generation but also in the fluctuations in feed-in levels. The direct current technology in the SuedLink project makes it possible to react to such fluctuations with greater flexibility and to control load flows more effectively. The cables’ transmission power is roughly equivalent to the output of four nuclear power stations and could supply power to around ten million households.
A tunnel 20 metres below the Elbe
Construction of the connecting tunnel crossing below the Elbe is scheduled to begin in the autumn of 2023, subject to planning permission. The work will commence with construction of a shaft in Wewelsfleth, Schleswig-Holstein. From there, the 5.2km tunnel will run approximately 20m below the Elbe until it reaches its destination: the target shaft at Wischhafen, Lower Saxony. As the two shafts are at groundwater level, the construction pits for the two shifts will have to be made waterproof with diaphragm walls of up to 50m deep prior to excavation – a challenging proposition.
The 25m-deep construction pit will then be excavated underwater, drained and secured with steel girders. At that point, the tunnel-boring machine manufactured specifically for this project will be assembled. It is designed to cope with the variable soil composition below the Elbe. The tunnel will be completed using segmental lining. The access infrastructure required for subsequent use will be constructed in Schleswig-Holstein and Lower Saxony during the tunnel boring phase.
Facts and figures at a glance
|Scope of services:||5.2km-long tunnel crossing below the Elbe River; construction pits with diaphragm walls, reinforcement piles, underwater excavation and underwater concrete; hydro-shield tunnelling with segmental lining; company buildings, open-cut tunnel and reinforced concrete cable pits; technical equipment in the tunnel and in company buildings and transmission infrastructure; conventional and BIM-based execution planning|
|Client:||TenneT TSO GmbH|
|Contractor:||PORR GmbH & Co. KGaA / PORR AG|
|Construction start:||Autumn 2023|