Production of HS2 tunnel segments begins

The first of 112,000 fibre-reinforced segments bound for the 16km (10 mile) Chiltern twin-tube tunnels have been produced at a purpose-built factory next to the TBM launch pads, which is also the site of the future south portal.

Didier Jacques, Align JV 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.”

He added: “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.”

The fabrication site is also the project’s HQ near the M25 motorway and its location will mean segments can not only be supplied more quickly to the project but will also result in fewer trucks on local roads.

Early summer 2021 will see the launch of the first two TBMs (Florence and Cecilia) that will spend more than three years boring and lining the tunnels.

HS2 Ltd main works contractor for the Chiltern tunnels is the Align JV comprising Bouygues Travaux Publics, Sir Robert McAlpine, and VolkerFitzpatrick; the JV will also lead on the construction of the nearby Colne Valley viaduct.

Welcoming the start of segment production, HS2 Ltd C1 Project Director Rohan Perin said: “The start of production … is a major milestone as we count down 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 tunnel construction is completed, the precast factory and the rest of the south portal site will be cleared. The chalk excavated from the tunnels will be used to landscape the site and create high-quality chalk grassland and other wildlife habitats.