HS2 Ltd has launched the 2,000 tonne tunnel boring machine (TBM) ‘Florence’ from it’s South Portal site next to the M25 in Hertfordshire, the first of 10 giant tunnelling machines that will dig 64 miles of tunnels between London and the West Midlands.
Named after nursing pioneer Florence Nightingale – a name suggested by local children due to her residence at nearby Claydon House in Bucks, and chosen in a public vote – the TBM will dig the first of a pair of 10 mile long tunnels under the Chiltern Hills and help to safeguard the woodland and wildlife habitats above ground. A second machine ‘Cecilia’ will launch next month to excavate the second tunnel at the South Portal site.
The first two TBMs will be operated by HS2’s main works contractor, and HSRG member Align – a joint venture formed of three international infrastructure companies: Bouygues Travaux Publics, Sir Robert McAlpine, and VolkerFitzpatrick. Designed specifically for the mix of chalk and flints under the Chilterns, the two identical TBMs will dig separate tunnels for north and southbound trains.
Each machine operates as a self-contained underground factory – digging the tunnel, lining it with concrete wall segments and grouting them into place at a speed of around 15 metres a day. 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 TBM, working in shifts to keep the machines 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.