Home » HS2’s second TBM ‘Caroline’ sets off under the capital

HS2’s second TBM ‘Caroline’ sets off under the capital

by Sion Geschwindt
HS2's second TBM 'Caroline' sets off under the capital

A tunnel boring machine (TBM) named ‘Caroline’ – after the world’s first professional female astronomer – has begun its five-mile journey carving a tunnel under London for HS2.

The second TBM launched in the capital, Caroline joins ‘Sushila’, that was switched on earlier this month on the same West London site.

The giant machine, which is longer than a football pitch, will now dig for 22 months, non-stop except for Christmas Day, towards Greenpark way in Greenford – boring five miles of the twin-bore Northolt Tunnel.

‘Caroline’ will be operated by a crew of 15 people, working in shifts. An additional 25 people will directly support each tunnel drive on the surface.

Caroline is longer than a football pitch, weighs over 2000 tonnes and has a cutter head (pictured) that is 9.84m in diameter (credit: HS2)

Travelling at an average of 14m per day, Caroline will dig the five-mile tunnel and install 4,207 tunnel segment rings to create the tunnel.

Each ring of the tunnel is made up of seven concrete segments which have been manufactured in the UK by Pacadar based in Kent.

The machine was switched on by HS2’s Civils Delivery Director, Mike Lyons, who said: “HS2’s construction continues to gather pace, and the launch of the fifth Tunnel Boring Machine on HS2 is another significant moment for Britain’s number one levelling-up project.

“Creating jobs and contracts for businesses today, HS2 is an investment in Britain’s economic growth now and for generations of rail passengers to come.”

Caroline will be operated by Skanska Costain STRABAG JV (SCS JV), HS2’s Main Works Civils Contractor constructing the HS2 tunnels in London.  

Further reading:

James Richardson, Managing Director of Skanska Costain STRABAG JV said: “We’re delighted to have begun our tunnelling journey towards Euston, travelling under one of the busiest cities in the world.

“Getting to this point has 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.”

Once Caroline and Sushila reach their destination at Greenpark Way, they will be dismantled and extracted from a 40m deep shaft.

Separately, two other equally massive tunnel boring machines will set off towards Greenpark Way from HS2’s Victoria Road site in 2023 to build a further 3.4 mile twin-bore tunnel.

Combined, the quartet of TBMs will build 8.4 miles of twin bored tunnels between West Ruislip and the new high speed rail super hub station at Old Oak Common.   

Image credit: Mike Lyons, HS2 civils delivery director (left) with Michael Greiner, head of tunnelling at SCS JV (credit: HS2)

Read next: HS2 unveils modular design for Thame Valley Viaduct

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