NEWS |
Tunneling completed on western part of HS2’s Northolt Tunnel
Contract signed for Imst- Haiming hydro plant AUSTRIA - Energy supplier TIWAG-Tiroler Wasserkraft has signed the contract for the main construction lot of the Imst-Haiming hydropower plant. A consortium of Swietelsky Tunnelbau,
Ing. Hans Bodner Ba and Implenia will build the project on the Inn River in western Austria. The contract is valued at €450 million
(US$500 million). The works include the construction of a
14km-long waterway with surge tank and tailrace, chambers with inlet and outlet pipes, and the tailwater reservoir. The contract was signed following an
Early Contractor Involvement (ECI) phase, during which planning was optimized and options investigated in collaboration with the potential partners. As well as strengthening relations
Above: The breakthrough marks the completion of the tunnel drives for the western section of the Northolt Tunnel TBM Caroline broke through into an underground reception can filled with foam concrete to mitigate the high water pressure in the ground PHOTO CREDIT: HS2
UK - HS2 has completed an 8km- long tunnel drive under London, with one of four TBMs building the Northolt Tunnel breaking through at Ealing.
TBM ‘Caroline’ is the second
machine to reach the Green Park Way vent shaft in Ealing. The 2,050-tonne TBM broke through into an underground reception can filled with foam concrete and installed the 4,217th concrete tunnel ring to complete the section of tunnel. HS2 is using the ‘reception can’
method for the breakthroughs at the shaft because of high groundwater pressure at the site. The method allows the TBM to maintain pressure while sealant can be applied from the tunnel lining, preventing water ingress. The ‘can’ in the shaft is then depressurize, opened and the TBM lifted out. Four Herrenknecht TBMs are being
used to build the Northolt Tunnel – a 13.5km-long twin-bore tunnel that will take the high-speed trains from West Ruislip into the new Old Oak Common super-hub station in west London. TBMs ‘Caroline’ and ‘Sushila’ have built the western section of the tunnel while two more are excavating the eastern leg,
12 | Summer 2025
from Victoria Road Crossover Box just outside the Old Oak Common station site. All are being lifted out at Green Park Way. TBM ‘Sushila’, the first machine to
be launched for this stretch of the HS2 route, completed her journey in December 2024. In total 93% of the Northolt
tunnel has been built, and the two other machines will complete their journeys later this year. HS2 Ltd client director Malcom
Codling said he was proud of the work done to complete the second breakthrough for the Northolt Tunnel. HS2’s London tunnels contractor,
Skanska Costain Strabag JV (SCS), is responsible for building the route through London. In total, this involves 20.7km of twin-bore tunnels, including the Northolt Tunnel and the Euston Tunnel, which will take the railway from Old Oak Common station into HS2’s terminus at Euston. Excavation of the Euston Tunnel
is expected to start in the next 12 months. SCS will also build eight vent shafts and headhouses – providing ventilation and emergency access to the tunnels.
between the partners early in the process, ECI aims to provide a detailed and robust project estimation.
Normet expands spraying equipment offering UK - Normet has launched two further concrete for works on underground construction projects. The Spraymec 4100 is a self-propelled,
rigid-frame concrete sprayer featuring a 4WD carrier with four-wheel steering and crab-steering for optimal manoeuvrability in confined underground spaces. Its boom has a vertical reach of 10.5m. The Spraymec 5100 has a highly
manoeuvrable spray manipulator with a maximum vertical reach of 14m. The closed-loop system automatically adjusts pump output and accelerator dosage in real time.
Porr breaks through on Romanian road tunnel ROMANIA - Porr has completed the first tunnel drive on Lot 4 of Romania’s Sibiu- Pitești motorway. The Daniela Tunnel, through Momaia Hill,
is 1.35km long. Crews have completed 665m (50%) of
the floor slab and 615m (46%) of the upper vault of the Daniela Tunnel. The company is also making progress
on the parallel Alina Tunnel, with 80% of excavation completed and 610m of the base plate built. The Sibiu-Pitești Motorway is an integral
part of the Trans-European Transport Network.
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