UTILITIES | ELECTRICAL GRID TUNNELS


STRENGTHENING GRID NETWORKS


Capital investment is underway in many countries to update, improve and strengthen electricity grids, including construction of carrier tunnels for power cables. We spotlight two under major rivers and one in a city


More and new high voltage power cables are being added to existing electricity networks to strengthen and expand the grids. Many projects are underway, at strategic sections of the grids in numerous countries, including Germany, Sweden and UK, and more. While the choice of using surface or elevated (pylon)


grid links over underground placement continues on, in varying settings with different economics, a number of those capital investment projects already involve construction of carrier tunnels, such as in the countries mentioned.


GERMANY - SUEDLINK Tunnel boring at the River Elbe for Germany’s SuedLink grid project involves a 4.9m-diameter Herrenknecht Mixshield constructing a 5.2km-long power cable carrier tunnel. The Factory Acceptance Test (FAT) of the TBM was in


mid-2024 for site assembly to be underway later in the year, at the launch site in in Schleswig-Holstein. The diameter of the TBM gave the advantage of the


cutterhead being able to be transported, delivered to site and assembled as a complete component. The TBM was launched in March 2025. The TBM’s long launch pit near the River Elbe called


for diaphragm wall construction and then excavation through the previous autumn, winter and spring. The D-Walls are up to 50m-60m deep, the launch pit 25m deep. Severe weather presented challenges for construction, including high wind limiting crane operation, and sodden ground making spoil removal, transport and site logsitcs more difficult. Geology along the alignment comprises of clay, peat,


sand, and gravel as well as stones and boulders. It runs below the river from Wewelsfleth, in Schleswig- Holstein, to Wischhafen, in Lower Saxony. Construction is by ARGE Tunnel Elbx, a JV of Porr and


Wayss & Freytag. The Suedlink project will enable the electricity


Above: Preparing the TBM to bore the grid tunnel under the River Elbe for the SuedLink project, Germany, in late 2024 PHOTO CREDIT: PORR


32 | September 2025


generated by wind farms in northern Germany to reach the south of the country, some 700km away. The river crossing is a key part of the Suedlink grid expansion project, which stretches from Brunsbüttel, in Schleswig- Holstein, in northern Germany to Großgartach in Baden- Württemberg. The operators of the transmission system are TeneeT and TransnetBW


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