Main works civils contractor Skanska Costain Strabag (SCS JV) has signed the order with Herrenknecht for two TBMs to bore the Northolt tunnels, twin 13-mile tunnels between central London and the M25 motorway.
These tunnels will begin just outside of Euston station and will be below ground until they emerge in west London at Old Oak Common station. The route will continue underground from Old Oak Common to the outskirts of west London.
Overall there will be 10 TBMs purchased to construct the 64 miles of tunnelling along the HS2 route between the West Midlands and London.
These first two London TBMs will be launched from a portal at West Ruislip and will travel five miles east, creating the western section of the Northolt Tunnel. Each machine will be 140 metres long with a 9.84-metre diameter cutter head, making them slightly smaller than the machines boring through the Chilterns. They will weigh 2,050 tonnes.
After they arrive at Green Park Way in Greenford the machines will be lifted out of the ground and the site will then be used as a vent shaft. The 8.4 mile tunnel will be completed with a 3.4-mile drive from Old Oak Common using two further TBMs that are yet to be procured. A second tunnel between Euston and Old Oak Common will complete the remaining 4.5 miles of London tunnel between the two HS2 stations.
Once the first new TBMs have been built, they will be transported by sea and delivered to site at the end of 2021. Once assembled, they are expected to begin the tunnel drive in mid-2022, with completion at the beginning of 2024.
SCS JV managing director James Richardson said: “As the construction partner responsible for the majority of tunnels on the HS2 project, our contract for the first two TBMs is a major milestone for us. This partnership with Herrenknecht has brought together leading expertise in both our organisations and together we are constructing some of the most advanced TBMs in the world to efficiently drive the tunnels under London.”
As previously report, Herrenknecht has also built the TBMs that Align JV, a joint venture of Bouygues Travaux Publics, Sir Robert McAlpine and VolkerFitzpatrick, will use to dig the Chiltern tunnels. Those machines are 170 metres long and the cutterheads are 10.26 metres in diameter.