HS2 Chiltern Tunnel - TBM Launch on BBC News

The largest tunnelling machine ever used on a UK rail project is officially starting work.
Named after Florence Nightingale, the 170m long TBM will dig the first of a pair of 10-mile long tunnels under the Chiltern Hills. A second machine - ‘Cecilia’ - will launch in June 2021 to excavate the second tunnel at the South Portal site in Hertfordshire.
Designed for the mix of chalk and flints under the Chilterns, the identical TBMs will dig separate tunnels for north and southbound trains. The cutter head will rotate at up to 3.2rpm with the machine expected to cover 15.6m per day.
Operating 24/7, Florence will line the tunnel with concrete wall segments and grout them into place as it makes its way beneath the Chiltern Hills. Her crew of 17 will be supported by over 100 people on the surface, managing the logistics and maintaining the progress of the tunnelling operation.