HS2 launches third TBM under London building the Northolt Tunnel

A third tunnel boring machine (TBM) being used as part of the UK major rain infrastructure project, the HS2 project, has been launched under London.

 The front shield of HS2’s TBM Emily being lifted into place prior to launch at Victoria Road Crossover box site

The front shield of HS2’s TBM Emily being lifted into place prior to launch at Victoria Road Crossover box site

The TBM, named after Emily Sophia Taylor, who helped establish the Perivale Maternity Hospital in 1937 before becoming Ealing's first female mayor in 1938, will be used to dig almost half of the 8.4-mile Northolt Tunnel. She will bore 3.4 miles under Ealing from Victoria Road Crossover Box, near HS2's new Old Oak Common station, to Greenpark Way in Greenford.

HS2's London Tunnels contractor, Skanska Costain STRABAG joint venture (SCS JV), assembled the TBM underground at the Victoria Road site after being lifted in parts and lowered into a shaft.

Manufactured by Herrenknecht in Germany, TBM Emily weighs 1700t and has a 9.11m diameter cutterhead. The TBM is an earth pressure balance machine, which is designed specifically for the soft London clay that will be extracted from the ground.

Complex preparations

Speaking about the launch, Malcolm Codling, project Client Director, HS2 Ltd, said: "We are working at peak construction on HS2, delivering the tunnels which HS2 trains will travel through under London. The preparation to launch TBM Emily has been complex and we remain on schedule to complete the Northolt Tunnel in 2025."

The Northolt Tunnel will carry HS2 trains in and out of London - extending between the new Old Oak Common superhub and the outskirts of the capital at West Ruislip.

The twin-bore tunnel is being built in two sections. Two TBM, named Sushila and Caroline, are already constructing it eastward between West Ruislip and Greenford. Another two - Emily and Anne - are being used to dig the tunnel in the opposite direction from Victoria Road Crossover Box to Greenford.

Emily and Anne's tunnel drive will cover 3.4 miles of the tunnel in total - slightly less than those being used on the other section. Following the launch of Emily, Anne, the fourth and final Northolt TBM, will be launched in March.

A quartet of TBM

The quartet of TBM are all set to complete their journeys in 2025, when they will be extracted from the ground through shafts at Greenpark Way.

The London Clay that will be extracted to build the tunnel will be taken away from Victoria Road Crossover Box by conveyor and taken to the London Logistics Hub at Willesden Euro Terminal. From there, it will be taken by rail and reused at sites in Cambridgeshire, Kent and Rugby.

James Richardson, MD of SCS JV, said: "The HS2 London tunnels team are well on the way to delivering a new railway into the heart of London with the launch of TBM Emily. Next month, we will be launching TBM Anne, who, together with Emily, will form the tunnel from Old Oak Common to Greenpark Way Shaft, where they will meet with TBM Sushila and Caroline, who are already halfway to completing their journeys from West Ruislip."

HS2 is also making progress on preparations on the separate tunnel between Old Oak Common and Euston - the line's ultimate central London terminus.

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