The excavation of the TBMs launch site and the construction of the concrete precast plant for the Chiltern tunnels on the London to Birmingham high speed rail line, HS2 First Phase project has now begun. The first TBM will be launched from a site next to the M25 early next year.

The two 170 m and 2,000 t machines – currently being manufactured in Germany – will dig at 80m below the ground the 10-mile-long Chiltern tunnels from the site next to the M25, to near South Heath in Buckinghamshire The tunnels will be lined with 118,000 concrete segments that will be 2m x 4m and weigh on average 8.5 t each.

At 136 acres the South Portal Chalfont Lane site will be the biggest construction site on the project. From here, specialist teams will deliver the tunnelling and the construction of the adjacent Colne Valley Viaduct.

Dedicated motorway slip-roads have been built to link the new site with the M25 and take construction traffic off local roads, while material excavated from the tunnels will be reused as landscaping on site.

The HS2’s main works contractor is Align JV, made up of Bouygues Travaux Publics, Sir Robert McAlpine and VolkerFitzpatrick, and its subcontractors.

The twin tube Chiltern tunnels will be the longest and deepest tunnel bores on route, with separate northbound and southbound tunnels and five ventilation shafts. The tunnels will carry the state-of-the-art HS2 trains under the Chiltern hills on their way to Birmingham, Scotland and the north of England. This new route will free up more space for local and freight services on the current mainline out of Euston and offer an environmentally friendly form of transport for long distance passengers.

Click uk/65 for the tunnelbuilder archive and visit https://www.hs2.org.uk/ and https://alignjv.com/. 24/20.