HS2 announces tunneling breakthrough in the Chiltern Hills as gigantic machines complete excavation

HS2 has announced a major breakthrough in its tunneling work being carried out in the Chiltern Hills.

Today (27 February), the rail project has confirmed its tunneling machine in the area has completed its 10-mile excavation.

HS2 Ltd has announced that the giant machine that was first used three years ago has completed its work. It has been described as the biggest tunneling machine used for a rail project in the UK and is the largest appliance of its kind that has been used by HS2.

It is an enormous 2,000 tonne Tunnel Boring Machine (TBM), named ‘Florence’, and one of 10 machines excavating the 32 miles of tunnel on the new railway linking London Euston with Birmingham and was the first to launch, in May 2021.

Two identical TBMs were used to create the twin-bore Chiltern tunnel, which stretches from the South Portal near the M25 to South Heath in Buckinghamshire. Parallel tunnels will carry north and south bound trains with a second TBM, named ‘Cecilia’, due to breakthrough in the coming weeks.

Rail minister Huw Merriman said: “Today’s breakthrough of HS2’s longest tunnel highlights the momentum behind the project and the achievement is testament to the hard work and dedication of the 450-strong team helping deliver the line that will transform rail travel for generations to come.”

HS2 says the machines were designed specifically for the geology under the Chilterns, and each one

is an underground factory – excavating the tunnel, lining it with 56,000 pre-cast concrete segments and grouting them into place as it moves forward at an average speed of 16m per day.

Four similar TBMs are being used for the London approach tunnels, while another two will work on Birmingham’s Bromford tunnel. Preparations are also underway for the launch of two more machines to excavate the Euston tunnels, HS2 Ltd adds.

HS2 Ltd Executive Chairman, Sir Jon Thompson, said: “Today is an incredible day of HS2 and I’d like to thank the hundreds of people who’ve worked so hard over many years to make it happen.”