On 18th February 2025 the TBM being used to construct the pressure tunnel on the VERBUND project ‘Kaprun 2029’ started its 5.6km journey from the Limberg valve chamber to the surge tank deep below the Maiskogel.
Some 200 guests were present when VERBUND’s hydropower management, Michael Amerer and Karl Heinz Gruber, together with tunnel patron Kathrin Aberger-Dick and the contractor ARGE representatives Jürgen Raschendorfer, COO Porr AG, and Bernd Raderbauer of Marti Tunnel AG, pressed the button to start the cutterhead turning.
By the end of 2027, a new headrace will be built as part of the modernisation of the VERBUND Kaprun-Hauptstufe power plant. This will ensure that water continues to flow safely and efficiently from the Wasserfallboden reservoir to the power plant in the valley floor for decades to come.
The machine used in Kaprun has already been successfully used in the Limberg II and Limberg III projects, with essential components and the cutterhead being replaced and adapted for the current project.
The 100-tonne cutterhead, which has a diameter of 6.9m, is equipped with 42 cutters, each of which has a diameter of 43cm and weighing 130kg. The TBM has a length of around 190m and weighs 1,200 tonnes. The individual components were transported to the assembly cavern in 90 challenging journeys and assembled on site in around eight weeks.
VERBUND Hydro Power Managing Director Michael Amerer: “We are continuing on the path taken by the heroes of Kaprun after the Second World War for the reconstruction of Austria. Today, we have driven the first metres of the new pressure tunnel – an important moment for VERBUND. This pressure tunnel is the centrepiece of our project, which will upgrade the entire power plant to the latest state of the art by 2029, so that we can continue to supply all of Austria with green electricity and efficient flexibility from hydropower in the future.’
VERBUND project manager Maria Leo: ‘A launch celebration is always something very special. We are pleased that the preparatory work has gone so well and that it is now starting. The geological conditions for the advance are well known and the tunnel boring machine and the team are already familiar with our mountains from previous projects. Almost all of the work will be carried out underground. This means that the impact of the construction work is reduced to a minimum.’
Over the next few months, the TBM will bore through the rock at an average rate of about 15m per day until it reaches its destination at the new surge tank in about a year. The new pressure tunnel is around 5,600m long, with an average incline of 0.50% and an excavation diameter of 6.9m.
VERBUND is investing around €370M in the ‘Kaprun 2029’ project.
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