Tunnel boring Florence set to dig the Chiltern Hills

HS2 Ltd today launched Florence, the first of 10 tunnel boring machines that will dig 64 miles of tunnels between London and the West Midlands.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.“The work has truly begun on taking HS2 northwards,” transport secretary Grant Shapps said in a statement. “The tunnels these machines dig will ensure the benefits of our new high-capacity, high-speed railway run to the great cities of the North and Midlands, forging stronger connections in our country, boosting connectivity and skills opportunities and transforming our transport links.”

The first two TBMs will be operated by HS2’s main works contractor, Align, a joint venture formed of Bouygues Travaux Publics, Sir Robert McAlpine, and VolkerFitzpatrick.

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.Chalk excavated from the tunnels will be used to create grassland habitats across 127 hectares of the southern Chiltern hills.

“Align is very proud to be launching the first two TBMs on the HS2 project,” said Align project director, Daniel Altier. “The TBMs include a number of innovations to improve efficiency and the safety of the environment in which the crew will be working, that have never before been introduced on any previous TBMs, worldwide.”Built by Herrenknecht in Germany, the two 2,000 tonne machines were transported to the UK in over 300 separate shipments last year, before being reassembled, tested and commissioned by tunnelling engineers at the Chiltern tunnel south portal site.

The names of the two TBMs were suggested by students at Meadow High School in Hillingdon and The Chalfonts Community College, Buckinghamshire, which are close to the tunnel launch site.