July 2025 marked the halfway point. The tunnel boring machine reached the end of the first tunnel tube for the first time with the tunnel breakthrough at the Augustinplatz emergency exit – a significant milestone for the U2 17-21 consortium.

Almost exactly one year later, the final tunnel breakthrough has taken place at the Augustinplatz emergency exit, this time on Track 1. Following the restart of “Debohra” in autumn 2025, the second tunnel tube between Matzleinsdorfer Platz and Augustinplatz has now also been completed. Across the six sections of the tunnelling work, 2,850 precast concrete rings (17,000 segments) were installed.

The two tunnel sections connect the four new U2 stations – Matzleinsdorfer Platz, Reinprechtsdorfer Straße, Pilgramgasse and Neubaugasse.

PORR CEO Karl-Heinz Strauss said: “The U2 extension will make a significant contribution to sustainable transport development and improve public transport services for hundreds of thousands of people. With the final breakthrough, an important milestone has been reached. It is particularly important to me that we were able to carry out this challenging phase of the project with a high level of safety. I would like to extend my warmest thanks to all our staff, our consortium partner, and Wiener Linien for this joint achievement.”

“With the successful completion of the tunnel boring for both tracks, we have reached an important milestone in the U2 extension. This success is down to technical excellence, precise planning, technically sophisticated solutions and the extraordinary commitment of everyone involved in the project. The close cooperation between the teams has played a key role in driving this complex infrastructure project forward safely and successfully. We can be proud of this joint achievement,” said Gerhard Urschitz, Member of the Executive Board of STRABAG AG.

Debohra’s journey beneath the city

“Debohra” was first assembled in Schwanau at the German site of the manufacturer Herrenknecht. The TBM, specially designed for Vienna, is 127 metres long, weighs around 1,300 tonnes and consists of around 27,000 individual parts.

In early 2024, “Debohra” was transported to Vienna in separate parts and reassembled at Matzleinsdorfer Platz. Since tunnelling began in autumn 2024, the TBM has worked its way almost entirely underground through the Vienna Tegel. The excavated material was removed via the central shaft at Matzleinsdorfer Platz – this saved around 20,000 truck journeys through the city and approximately 75 tonnes of CO₂.

For the tunnelling of the second tunnel tube, following the completion of Track 2, parts of the machine were also removed and returned to Matzleinsdorfer Platz, whilst the trailing sections were pulled back to the start via the already completed tube. Following the second tunnel breakthrough at Augustinplatz, dismantling work is now underway. “Debohra” will then return to Herrenknecht, where it will be overhauled and prepared for future assignments.