High Speed 2 (HS2) Chiltern Tunnel, Portals and Shafts

High Speed 2 (HS2) is a 140-mile-long (225km) high-speed railway between London and Birmingham currently under construction. Align (a joint venture of Bouygues Travaux Publics, Sir Robert McAlpine, and Volkerfitzpatrick) was awarded the Central 1 (C1) Main Works Contract, which consists of 23.9km of high-speed rail infrastructure. This section features a 3.4km viaduct, a 16km twin-bored tunnel with 5 ventilation/access shafts, 5km of engineering earthworks, two highway overbridges, one footbridge and a green overbridge.

As part of the Align-D JV working with Jacobs and Align, Rendel and Ingerop provided tender, scheme, detailed design, construction phase and handover support for contract C1 to the Design-and-Build Contractor, Align JV. The Chiltern Tunnel comprises twin bored tunnels under the Chiltern Hills an area considered a ‘National Landscape’ with each tunnel 16km long. It includes five intervention shafts (four also are vent shafts) along the line of route – Chalfont St Peter, Chalfont St Giles, Amersham, Little Missenden and Chesham Road. The south portal is located next to the M25 near Maple Cross and the north portal in Great Missenden, Buckinghamshire.

The services provided included:

• Design of tunnel shafts (containing intervention and ventilation facilities) including caisson shafts sunk from the surface, collars for TBM intersection of shafts, diaphragm walls and shafts (up to 80m deep)
• Design of portal structures including diaphragm walls and soil nail retaining structures for portal headwalls including TBM launch/retrieval considerations
• Design of tunnel services buildings, including internal shaft structures, basements and foundations
• Design of cuttings, embankments, ground stabilisation, soil nailing and earth retaining structures
• Civil, highways, geotechnical, structural, mechanical, electrical, communications, hydraulics, drainage, piping (fire and water), environmental and sustainability, project management, design/engineering management, programming, cost estimating, procurement contract management, BIM including federated 3D BIM models and data management.
• Geotechnical modelling and ground risk assessments; soil-structure interaction analysis