HS2 prepares for 21km tunnels under London (TunnelTalk)

Of the 45km of twin tube bored tunnels to be constructed as part of the 225km High Speed 2 (HS2) rail project in the UK to link Birmingham and London, just under half is located under west London, between the HS2 southern terminus at Euston Station and a portal at West Ruislip, just inside the orbital M25 highway. The 21km route presents a complex engineering and logistical challenge for main contractor Skanska-Costain-Strabag JV (SCS). Jonathan Rowland spoke with Dave Terry, Tunnel Engineering Lead for SCS, Michael Greiner, Tunnel Manager for SCS, and Eddie Woods, Head of Tunnelling and Underground Structures for project delivery partner HS2 Ltd, to report the details of the TBM drives and the station cavern excavations that form the major part of the £3.3 billion design-build contract awarded to SCS in 2017.

Six TBMs of different diameters and through varying geological conditions in three sections will be used to excavate the 21km route of the London running tunnels of the HS2 rail project in the UK (Fig 1).

• 8km x 8.8m inner diametre (id) Northolt West tunnel between West Ruislip portal and Greenpark Way ventilation shaft.
• 5.5km x 8.1m id Northolt East tunnel between Greenpark Way and Old Oak Common Station.
• 7.2km x 7.5m id Euston tunnel between Old Oak Common Station and Euston Station.

Fig 1. HS2 London tunnels from Euston to West Ruislip

A seventh TBM will excavate a 1km x 6.1m id logistics tunnel that will provide access from the main Atlas Road construction compound to Old Oak Common Station, the launch site for the Northolt East and Euston TBMs. It will be used to bring construction materials into the tunnels, including the precast concrete lining segments, and to remove muck.

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