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Video | Inside HS2 tunnel boring machine digging under Chilterns

HS2 has revealed the inner workings of its 170m-long tunnel boring machine (TBM) Cecilia, to show how the machine is excavating a 10-mile section of tunnel under the Chilterns.

The TBM features an innovative robotic arm which picks wooden wedges used to stack the individual precast concrete tunnel wall segments to avoid workers accessing a dangerous area to remove them manually.

A slurry pump fitted within the TBM removes up to 1,500 cu m of slurry and excavated material per hour. The TBM also contains a crane which picks up and places concrete tunnel wall segments onto a feeder before they are taken to the build area.

At the build area, the tunnel segments are installed, with seven segments, each weighing up to 8.5t, making up a ring.

Cecilia, named after astronomer and astrophysicist Cecilia Payne-Gaposchkin by public vote, is the second of two 2,000t TBMs to be launched to excavate twin tunnels under the Chilterns. The first machine, named Florence, was launched in May.

Cecilia will continue to head north, mining under the Chiltern hills for the next three years.

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