The construction method: We build with minimal interference using the tunnel excavator

Introducing: our ‘Debohra’ tunnel excavator

Our Debohra tunnelling machine started work at the end of September 2024. It is digging its way from Matzleinsdorfer Platz along a route of around four kilometres to Augustinplatz in the seventh district and constructing the new line tunnels for the U2 underground line. This work is taking place underground. Debohra has reached its first milestone, the Reinprechtsdorfer Straße emergency exit, at the end of 2024. At the beginning of 2025, it has arrived at the future U2xU4 Pilgramgasse station. On its way from Matzleinsdorfer Platz to Pilgramgasse, it has already dug 935 metres of new U2 tunnel and installed 4,200 tubbings (the concrete ring segments that make up the outer shell of the tunnel tube).

All of the earth excavated by Debohra is being removed via a central shaft at Matzleinsdorfer Platz. This avoids dust and noise and a whole 20,000 lorry journeys through the city - which in turn saves up to 75 tonnes of harmful CO₂.

The construction methods: tunnelling with the tunnel excavator

This construction method can be used for longer sections with an even tunnel course, whereby the ground must also be relatively even. The 127 metre long tunnel excavation machine completes all work steps in one: digging the tunnel, sealing and lining the tunnel tube and removing the demolition material.

Open construction method ("lid construction")

Where there will be staircases or emergency exits on the surface in future, open construction will be used. The so-called cover construction method is used: First, bored piles or diaphragm walls made of reinforced concrete are constructed, between which the excavation pit is dug. As soon as the excavator and wheel loader have reached a depth at which they can work, the pit is sealed with a concrete cover. Construction materials are then transported in and out via smaller conveyor shafts that remain in place.

Our explanatory video shows how drilled piles work:

New Austrian tunnelling method

This construction method, which has been tried and tested over many years, is used, for example, when angled building sections have to be built. This also applies to the station tunnels, i.e. those sections of track where the platforms will later be. First, the ground is secured with steel spikes. Then the soil is excavated metre by metre and the resulting tunnel is reinforced with shotcrete on a steel grid.