HS2 TBMs delivered to Chiltern Tunnel site

Each 170m-long and weighing 2,000t, the TBMs will be the largest ever to be used on a UK rail project and were safely delivered in parts to the Align Chiltern Tunnel site, west of London and just inside the M25 motorway.

Named Florence and Cecilia, the 10.26m-diameter variable density TBMs arrived in parts over multiple separate shipments from the Herrenknecht factory in Schwanau, Germany. The machines will be reassembled, tested and commissioned to start work on the project’s 16km (10 mile) twin-bore Chiltern Tunnel.

As the longest and deepest tunnel on the Phase 1 route from London to Birmingham, the Chiltern will be the first to be excavated, with the TBMs set to be working 24/7 for more than three years.

Florence will launch in early 2021, followed by Cecilia a few weeks later. They will excavate identical twin tunnels under the Chiltern Hills through a geological mix of chalk and flint. Working at depths of up to 80m, the machines will advance at an expected average of 15m/day, erecting a 9.1m ID segmental lining as they progress. To complete the total 32km of tunnels will require 112,000 segments, all made on site, each weighing an average of 8.5t and each around 2m wide.

The TBMs will be operated by Align JV – a joint venture comprising Bouygues Travaux Publics, Sir Robert McAlpine, and VolkerFitzpatrick. Each machine will be driven by a crew of 17 who will work in shifts to ensure 24/7 operation; they will be supported by 100 people on the surface who will manage logistics and maintain the smooth progress of the tunnelling operation.

Welcoming the arrival of the TBMs, HS2 Ltd CEO Mark Thurston said: “The arrival of Florence and Cecilia is a major step forward and our expert team will now work to assemble, test and commission them before their launch next year. The launch…will be a defining moment in the history of HS2 – and our work to deliver a high-speed railway that will offer a low-carbon alternative for journeys across the UK.”