HS2 Casts First of 112,000 Chiltern Tunnel Wall Segments

HS2 has cast the first of 112,000 tunnel wall segments that will be used to build the Chiltern tunnel outside of London.

This milestone was reached ahead of the launch of the tunnel boring machines Florence and Cecilia. The wall segment was manufactured at a purpose-built production line at the high-speed railway’s tunnelling headquarters near the M25. The location is next to the TBM launch pads at the south portals of the tunnels. This removes the need for lorries carrying the segments to the TBMs.

HS2 tunnel segments for the Chiltern tunnel
HS2 tunnel segments for the Chiltern tunnel

The TBMs, Florence and Cecilia, manufactured by German specialist Herrenknecht, are scheduled to start work in early summer. Each one is 170m long and weighs 2,000 tons. In order for them to excavate and build the 10-mile twin bores, they will spend more than three years in the ground.

The wall segments are made of fibre-reinforced concrete.

The south portal of the Chiltern tunnel
The south portal of the Chiltern tunnel

Align JV is the main works contractor responsible for constructing the Chiltern tunnel as well as the nearby Colne Valley Viaduct. After the construction works are complete, the pre-cast factory and the rest of the site at the south portal will be cleared. The chalk excavated from the tunnel will go towards landscaping the site.

Rohan Perin, C1 Project Director, HS2 Ltd, 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.”

Each tunnel ring will consist of seven segments. A total of 160 rings or 1,120 segments will be manufactured prior to the TBMs launching. Robots are being used to polish the concrete. This used to be a manual job but by using robots the finished product will be more consistent.

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