HS2

Designs for final Chiltern tunnel headhouse revealed by HS2

The first images of the latest ‘barn design’ rural headhouse set to be built along the Chiltern tunnel have been released by HS2.

Headhouses will provide emergency access to the 10-mile-long tunnel and the latest reveal completes the set of five headhouses.

Work has already kickstarted on all sites and excavation is underway for what will be the longest tunnel on the HS2 project.

The plans were drawn up by HS2 Ltd.’s main works contractor Align JV – a team made up of Bouygues Travaux Publics, Sir Robert McAlpine, and VolkerFitzpatrick - working with its design partners Jacobs and Ingerop-Rendel, and the architect Grimshaw and landscape designers, LDA.

The Chesham Road headhouse has been designed to blend into the surrounding landscape, taking inspiration from the style of nearby barns and other agricultural infrastructures in the area.

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The whole structure will sit on a dark blue, brick base, and the building will be covered in a pre-weathered grey zinc roof which will age over time, without any loss of sturdiness or quality.

Daniel Altier, Align Project Director, said “I am delighted with the progress we have made so far at all five shaft sites."

He continued, "we are working to a detailed schedule to ensure that each shaft is ready for the arrival of our two TBMs, currently tunnelling north from the South Portal”

“As is the case with all the shafts, it is important that the headhouse design at Chesham Road fits into the surrounding landscape, therefore we look forward receiving comments on the design from the local community.”

Below ground level, a 45m shaft will reach down to the twin tunnels, providing access for the emergency services.

Contrasting to the other 4 shafts, ventilation equipment is not required at Chesham Road due to its close proximity to the North Portal of the tunnel.

In 2015, the Chesham Road shaft became a new addition to the Chiltern tunnel, allowing the tunnel to be safely extended by 2.6km.

Consequently, the decision saved 12 hectares of woodland at the nearby Mantle’s Wood, Sibley’s Coppice and Farthings Wood.

Earlier this year, two giant tunnel boring machines (TBMs) were launched to dig the parallel northbound and southbound tunnels, both of which have now passed under the M25 and are heading towards the first shaft site near Chalfont St Peter.

A team of expert engineers have already excavated the shaft to a depth of 68m and are currently working towards completing it ahead of the arrival of the first TBM next year.

HS2

The HS2 team have also completed the concrete ‘diaphragm walls’ for the 46m deep shaft at the next site, near Chalfont St Giles.

Specialist drilling equipment was used and the excavation of material from within the concrete walls will soon begin so as to create the shaft.

Additionally, work is well underway at the next site, located next to the A413 road junction outside Amersham, with engineers working on the concrete ‘D-walls’ for the 51m deep shaft.

Engineers are now preparing for the start of wall construction, further north at the Little Missenden site, alongside the A413, while at Chesham Road site – the last shaft the TBMs will reach - set up is now in progress.

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