Photos | First of 112,000 pre-cast HS2 Chiltern tunnel wall segments produced

The casting factory, March 2021, David Hares (c) HS2 Ltd

The first of 112,000 pre-cast, steel fibre-reinforced concrete wall segments that will line the HS2 Chiltern tunnel have been produced.

The segments rolled off a purpose-built production line at the project’s tunnelling HQ close to the M25.

The project’s first two Tunnel Boring Machines (TBMs) — named Florence and Cecilia — are due to launch in early summer. Each of the 170m long, 2,000t machines will spend more than three years underground, digging and slotting the wall segments into place to create the 10-mile long tunnels.

Robots are used to polish the pre-cast concrete sections (Image: HS2/David Hares)

Construction of the Chiltern tunnel, and nearby Colne Valley Viaduct, is being led by HS2’s main works contractor, Align JV — a joint venture made up of Bouygues Travaux Publics, Sir Robert McAlpine, and VolkerFitzpatrick.

Didier Jacques, Align’s underground construction director said: “We are using Steel Fibre Reinforced Concrete (SFRC) in the segments due to the improved ductility and durability it offers. The SFRC segments are also easier to fabricate.

Inside the casting factory (Image: HS2/David Hares)

“Once in the moulds we are using robots to polish the concrete, a task that was previously manual, to improve the quality and consistency of the final product. With seven segments in each ring, we will be producing a total of 160 rings ahead of launch of the first TBM later this year.” 

Exterior view of the casting factory at the south portal Chalfont Lane site (Image: HS2/David Hares)

HS2 Ltd’s C1 project director, Rohan Perin said: “The start of production at the tunnel wall precast plant is a major milestone as we countdown to the launch of our first TBMs later this year. By casting all 112,000 segments on site we can significantly reduce the number of HGVs on local roads and reduce the amount of disruption for local residents.

“Once complete, the 10-mile-long tunnels under the Chilterns will also significantly reduce the impact of the project on the local environment, with material from tunnels used to create new species rich chalk grassland.”

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