BTS | HS2
HS2 TUNNELLING: THE CLIENT’S PERSPECTIVE
On 16 October 2025, two speakers from the client team at High Speed Two Ltd (HS2) presented on tunnelling progress to a packed joint meeting of the British Tunnelling Society (BTS) and British Geotechnical Association (BGA). Martyn Noak, Head of Ground Engineering, provided a project overview and progress update on HS2 project Phase 1, including TBM data; Mark Lemmon, Lead Tunnel Engineer, described the geological setting and associated challenges. Here, they present the key points of their presentation.
HS2 route map ALL IMAGES COURTESY OF HS2 LTD
PROJECT DESCRIPTION AND UPDATE There are 44km of twin bore tunnel and 8km of cut-and-cover or Green Tunnel comprising some 19% of the 225km length of HS2 high-speed rail route, between Euston, in central London, and Birmingham. These are being constructed by four different Integrated Project Teams each comprising of HS2 Ltd, the Contractor and the Designer, as follows. ● SCS: Skanska/Costain/Strabag - the London Tunnels; ● Align: Bouygues, Sir Robert McAlpine and VolkerFitzpatrick – the Chiltern Tunnels;
● EKFB: Effage/Kier/Ferrovial/BAM –the Green Tunnels; and,
● BBV: Balfour Beatty/Vinci – Long Itchington Wood and Bromford Tunnels.
Typical bored tunnel cross sections vary between
7.55m and 9.1m internal diameter (ID), respectively; sprayed concrete lined (SCL) cross passages (CP) are
10 | March 2026
around 4m ID and between 12m and 30m in length. Large diameter SCL tunnels, up to 11.25m in diameter across the axis, have been constructed; and, cut- and-cover tunnels are generally double-cell precast concrete with each cell around 8.5m x 8.5m.
THE LONDON TUNNELS Starting at Old Oak Common station (OOC) and going west, all the tunnelling assets were described in turn, starting with the SCL stub tunnels constructed to the east of the OOC box. These are circa 100m-long and will be the launch tunnels for the tunnel boring machine (TBM) drives to Euston station. The tunnels are complete and the TBMs have been assembled ready for a launch in 2026. Access for the stub tunnel construction is via the Atlas Road Logistics Tunnel (ARLT), constructed by a 6.2m diameter, 850m long earth pressure balance machine (EPBM) - a refurbished Crossrail machine - and completed
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