HS2’s first two Tunnel Boring Machines in London have completed the first mile of twin-bored tunnel in the capital.
Sushila and Caroline were launched in November 2022 to bore the western part of the 8.4-mile-long Northolt Tunnel. Sushila is constructed the ‘downline’, which will be used by trains travelling towards London, and Caroline the ‘upline’ for trains travelling to the Midlands and the North. Construction of the tunnel is due to be complete by 2025.
The machines were named after local teacher Sushila Hirani and astronomer Caroline Herschell by pupils at two local schools. Construction of this section of route is by the Skanska Costain Strabag (SCS) joint venture, using tunnel segments manufactured by Pacadar on the Isle of Grain and delivered by rail to sidings at West Ruislip. Construction of cross passages between the two tunnel bores will begin shortly.
In early 2024 two further TBMs will be launched from the Victoria Road crossover box, just west of Old Oak Common station – these will excavate the tunnel heading west to Greenpark Way in Greenford, where they will meet Sushila and Caroline, together completing construction of Northolt Tunnel.