HS2 launches second giant tunnelling machine in the Chilterns

The machine has been named 'Celia'.

By James Lowson
Thursday, 8th July 2021, 2:58 pm
Updated Thursday, 8th July 2021, 3:00 pm

Last week HS2 launched its second giant tunnelling machine to continue excavation along the Chilterns.

The 2,000 tonne machine will excavate the ten mile stretch long tunnels beneath the Chiltern hills just outside London.

Another massive machine called 'Florence' was launched by HS2 last month.

HS2's 'Celia'

HS2 advise this new machine is faster than the current machine, due to geological data fed back from Florence.

In total HS2 will use ten machines during construction, the plan is to create 64 miles of tunnel between London and the West Midlands.

This move has been protested by both local authorities in Buckinghamshire and protest groups.

HS2 says that the construction has already created jobs. More than 16,000 jobs and over 500 apprenticeships are already being supported by HS2.


The new machine is named after a Wendover astronomer, Cecilia Payne-Gaposchkin, the name was chosen via a public vote, after being suggested by pupils at the nearby Chalfont Community College.

The two machines will work side-by-side, excavating separate northbound and southbound tunnels.

The machines are operated by HS2’s main works contractor, Align – a joint venture formed of Bouygues Travaux Publics, Sir Robert McAlpine, and VolkerFitzpatrick – and launched from a site by the M25 to the north west of London.

HS2 says that these massive machines have been built specifically for the mix of chalk and flints under the Chilterns and that they are powered by zero carbon electricity and move at a speed of up to 15 metres a day.


Each machine operates as a self-contained underground factory - digging the tunnel, lining it with concrete wall segments and grouting them into place. Each tunnel will require 56,000 precision engineered, fibre-reinforced segments – which will all be made on site.

A crew of 17 people will operate each machine working in shifts to keep them running 24/7. They will be supported by over 100 people on the surface, managing the logistics and maintaining the smooth progress of the tunnelling operation.

Chalk excavated from the tunnels will be used for landscaping at the south portal site once construction is complete, creating wildlife-rich chalk grassland habitats across 127 hectares of the southern Chiltern hills, HS2 says.

Align is recruiting 1,200 personnel in total, including 100 apprentices, to work on the Central 1 Area of HS2 Phase One that it is delivering.