The second giant boring machine (TBM) building HS2 under the Chiltern Hills broke through at the tunnel’s northern portal early evening yesterday, completing a journey that began in June 2021.
Named Cecilia, the TBM has driven for 10 miles underground to join twin sister machine – Florence. She arrived at the site near the Buckinghamshire town of Wendover on 27 February, after completing her adjacent tunnel drive.
Between them, the two 2,000 tonne machines have built the twin bore tunnel at depths of up to 80 metres and excavated three million cubic metres of chalk.
Each machine operates like an underground factory, able to excavate the tunnels and line them with 56,000 pre-cast concrete tunnel segments, grouting them into place and moving forward at an average speed of 16 metres per day.
When HS2 is operational trains will travel through the Chiltern tunnel – the line’s longest – at speeds of up to 200mph, helping to almost halve journey times between Britain’s two largest cities.
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