Second HS2 TBM begins journey under London

The 9.84m diameter TBM Caroline was launched yesterday to begin the five-mile (8km) journey from West Ruislip to Greenford. Sushila, the first of the six TBMs that will bore under London, has advanced more than 70m since it was launched earlier this month. A total of 10 TBMs will be used for HS2.

TBM Caroline, named after 18^th century astronomer Caroline Herschel, will take 22 months to complete excavation of the twin-bore Northolt Tunnel. It will advance at an average of 14m per day and install 4,207 tunnel segment rings. Each ring comprises seven concrete segments, which were manufactured by Pacadar in Kent.

Once the two TBMs reach their destination at Greenpark Way they will be dismantled and extracted from a 40m deep shaft.

Next year two more TBMs will set off towards Greenpark Way from HS2’s Victoria Road site to build a further 3.4-mile (5.5km) twin-bore tunnel. Combined, the four TBMs will build 8.4 miles (13.5km) of twin bored tunnels between West Ruislip and the new high-speed rail super hub station at Old Oak Common.

Another tunnel 4.5-mile (7.2km) twin-bore tunnel extending from Old Oak Common to Euston will complete HS2’s journey to its London terminus.

SCS JV managing director James Richardson said reaching the TBM launch had been “a huge team effort and the scale of this programme has enabled many new people to join the industry and work on this crucial national infrastructure project”.