Breakthrough at ElbX Elbe Crossing Project
On 22 June, the breakthrough took place in the construction of the ElbX tunnel across the Elbe, carried out on behalf of TenneT Germany and in collaboration with the project partners. The tunnel construction work carried out by Porr as part of the large-scale SuedLink project connects Schleswig-Holstein and Lower Saxony over a distance of around 5.2 kilometres. The Elbe crossing is one of the key sections of the power line, which will in future transport renewable energy from the north to the south of Germany.
20 Metres Below the Riverbed of the Elbe
For the construction of the tunnel, the ARGE Tunnel ElbX consortium (Porr and Wayss & Freytag Ingenieurbau AG) ordered a tunnel boring machine (TBM) from Herrenknecht AG that was specifically tailored to the project’s requirements. The Mixshield has a diameter of 4900 mms, is 190 m long, and weighs a total of 700 metric tons.
On 22 June 2026, the TBM broke through during the construction of the ElbX tunnel across the Elbe on behalf of TenneT Germany
Credit/Quelle: Herrenknecht
The main challenges for tunnel advancement at ElbX were, in particular, the geology, the high water permeability of the ground, the water pressure beneath the Elbe River, and the relatively compact diameter for a Mixshield.
“The tunnelling route beneath the Elbe River features highly variable geology consisting of clay, silt, peat, sand, gravel, as well as stones and boulders. To cope with the extremely sticky Lauenburg clay on this geologically very heterogeneous drilling section, the TBM is equipped with a powerful center flushing system at the cutterhead with a capacity of 500 m³ per hour,” explains Herrenknecht project manager Johannes Faißt. A total of animpressive 1200 m³ of bentonite slurry flowed through the machine’s circulation system every hour. This prevented the cutterhead and the tools mounted on it from becoming clogged.
The Mixshield is sealed against water pressure of up to 3.8 bar – which prevails 20 m below the riverbed – using a multi-layer sealing system. The tunnel will have an inner diameter of 4 m and an outer diameter of 4.60 m. To navigate the ElbX route – which includes curves, descents, and ascents – the TBM was equipped with a navigation system from Herrenknecht’s subsidiary VMT.
Breakthrough Achieved Earlier Than Planned
Over the final 400 metres, the project team benefited in particular from favourable ground conditions, which enabled exceptional tunnelling progress. New records were set on site: the maximum daily advance was 32.6 m or 25 tunnel rings, whilst the weekly record stood at 158.7 m.
Throughout the entire construction period, tunnelling was characterised by variable and challenging ground conditions in the groundwater of the Elbe; nevertheless, the breakthrough was achieved earlier than forecast. Upon reaching the target shaft at the end of June 2026, the tunnel boring machine, christened ‘Elsa’, completed the driving work that had begun in February 2025.
With the successful completion of the mechanised tunnelling, work has now begun on the inner lining and the installation of technical equipment within the tunnel.
Once completed, the Elbe crossing between Wewelsfleth (Schleswig-Holstein) and Wischhafen (Lower Saxony) – as part of the SuedLink power line – will carry high-capacity 525-kilovolt direct-current cables beneath the river to transport wind power from northern Germany to the southern regions. The power line is designed for a transmission capacity of 4 gigawatts and is regarded as a key project in Germany’s energy transition.
