Construction News

Wed December 01 2021

Related Information

One down nine to go: Chiltern tunnelling hits first milestone

1 Oct The first tunnel boring machine digging under the Chilterns has hit the one-mile mark this week.

10% of one of the twin tunnels under the Chilterns is now constructed
10% of one of the twin tunnels under the Chilterns is now constructed

Launched in May, the 170-metre long tunnel boring machine (TBM) covered the first mile cutting through a mix of chalk and flint beneath the Chiltern hills just outside London.

Florence is one of two identical machines excavating the twin 10-mile tunnels. A second machine, Cecilia, is a short way behind, having set off at the start of July. Both TBMs are expected to break out in around three years’ time.

These TBMs are operated by Align, HS2 Ltd’s main works contractor for the central section of the new Birmingham-London line. Align is a joint venture of Bouygues Travaux Publics, Sir Robert McAlpine, and VolkerFitzpatrick.

Each TBM is operated by a crew of 17 people, working in shifts and supported by over 100 people on the surface.

 Align project director Daniel Altier said: “Florence reaching the one-mile point is a great achievement, however we still have a long way to go.”

Each of the separate northbound and southbound tunnels will require 56,000 fibre-reinforced concrete wall segments – which are cast at the south portal of the tunnel, next to the M25 near Maple Cross. During her first mile, Florence and her crew have installed more than 5,500 separate segments, each weighing around 8.5 tonnes.

Approximately 2.7 million cubic metres of spoil will be excavated during the construction of the tunnels and used for landscaping around the south portal site.

In total there will be 10 TBMs across the Birmingham-London first phase of the HS2 project, boring 64 miles of tunnel.

Got a story? Email


Click here to view more construction news »