BTS | HS2
Typical Green Tunnel
Amersham, Little Missenden and Chesham Road. A single design used for these shafts comprised a circular diaphragm wall shaft with connection adits; they have headhouses designed to look like agricultural buildings and successfully blend into the surrounding countryside. There are 37 SCL CPs in the Chiltern Tunnels. All of the CP zones were grouted prior to excavation with some requiring a significant grouting campaign due to the 2bar water pressure. The twin-tube tunnel is complete and has been handed over to HS2 with the shafts not far behind.
THE GREEN TUNNELS EKFB are building three Green Tunnels at Wendover, Chipping Warden and Greatworth varying in length between 1.4km and 2.5km. Predominantly for environmental reasons these three
tunnels are all constructed using the same precast ‘Matiere Arch’ methodology, with a dedicated precast factory being established at the Stanton precast facility in Derbyshire for casting all 10,000 elements. The structure consists of a 5-piece arch – 2x outer
walls, a central wall, and 2x arch roofs with a cast-in- place invert tied to the walls with double hoop bars. Maximum overburden is around 10m, and two of the tunnels carry permanent road diversions over the top. Following precast arch installation, a sheet
waterproofing membrane is rolled out over the top and welded to a sheet installed beneath the blinding and then backfill commences in carefully controlled layers.
12 | March 2026
BBV TUNNELS
Long Itchington Wood Tunnel Long Itchington Wood Tunnel is an 8.8m diameter 1.5km-long tunnel, bored using a VD slurry machine through mudstone with 3 SCL CPs. Upon completion of the first drive, the machine was transported back to the start and used for the second drive before being repurposed as the second TBM for the smaller diameter Bromford tunnel.
Bromford Tunnel The Bromford Tunnel is a 7.55m-diameter tunnel bored using a VD slurry machine up to 35m below ground level on the approaches to the HS2 terminus station at Birmingham Curzon Street. The tunnel is 5.8km-long and has a single
intermediate shaft, consisting of a D-Wall circular shaft with sprayed concrete adit connections for ventilation, services and personnel access. One of the key interfaces for this tunnel is the Bromford Viaduct carrying the M6 Motorway above, which sits within the 1mm settlement contour for 700m of the drive. Following five years of negotiations with the asset owner, National Highways, both drives passed this asset with no impact.
INVERTS AND WALKWAYS Within the tunnelling contractor scope is the first stage invert concrete and the walkways. Align and SCS, respectively, elected to pour their invert concrete
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