The two giant 2,000-tonne HS2 machines currently digging underneath the Chilterns have completed the first stage of the 10-mile twin tunnels.
The tunnel boring machines (TBMs) - named Florence and Cecilia - have dug a combined total of 3.6 miles since they launched last summer from the tunnel's south portal, to the first ventilation shaft at Chalfont St Peter.
The 78-metre deep shaft at Chalfont St Peter is the first of five that will provide ventilation and emergency access to the 10-mile-long twin tunnels – which are the longest on the project.
Once complete, the shaft will be covered by a headhouse which HS2 say will resemble "local farm buildings".
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Each TBM is a 170-metre long self-contained underground factory - digging the tunnel, lining it with concrete wall segments and grouting them into place as it moves forward.
They are expected to break out at the north portal in around two and a half years.
A crew of 17 people on board each machine keep them running, working in shifts and supported by over 100 people on the surface, managing the logistics and maintaining the progress of the tunnelling operation.
Approximately 2.7 million cubic metres of material will be excavated during the construction of the tunnels and used for landscaping on the south portal site.
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In total there will be ten TBMs on the HS2 project - working to create 64 miles of tunnel between London and the West Midlands including major tunnels on the approach to London and Birmingham. Three machines have been launched so far.
These first two TBMs on the HS2 project in the Chilterns are operated by, Align – a joint venture formed of Bouygues Travaux Publics, Sir Robert McAlpine, and VolkerFitzpatrick.
Align Project Director Daniel Altier said: Florence and Cecilia reaching our first shaft at Chalfont St Peter is a great achievement for not only the tunnelling team but also the construction team involved in excavating and preparing the shaft.
"In particular I would like to pay credit to KVJV and Keltbray our supply chain partners, who have been working tirelessly over the last few months to ensure the shaft is ready for the arrival of Florence and Cecilia.”
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