First breakthough made on HS2

A 2,000-tonne TBM named Dorothy has completed its 1.6km (one mile) dig under Long Itchington Wood in Warwickshire.

The 125m-long TBM, which started its journey at the tunnel’s north portal in December 2021, broke through the wall of the reception box at the south portal site on July 22.

Dorothy, named after Dorothy Hodgkin, who in 1964 became the first British woman to win the Nobel Prize in Chemistry, has worked around the clock since being launched. During the tunnelling, 790 concrete rings have been put in place, with each ring made from eight 2m-long segments.

The tunnel preserves the woodland above, which is classified as a Site of Special Scientific Interest (SSSI.

HS2 Ltd CEO Mark Thurston said it was a historic moment for HS2 and he congratulated everyone involved in delivering it.

“The 400-strong team, including tunnelling engineers, TBM operators and the construction workers at both portal sites, have pulled out all the stops to achieve this fantastic milestone,” he said.

“This milestone demonstrates the significant momentum behind Britain’s new zero-carbon railway, creating thousands of jobs and apprenticeships, along with hundreds of opportunities for businesses right across the country, helping fuel our economic recovery.”

Michael Dyke, managing director of HS2’s main civils contractor, Balfour Beatty Vinci (BBV JV) said it was a momentous moment, not only for Balfour Beatty Vinci, but for everyone involved in delivering HS2.

“Thanks to the hard work and dedication of our team, Dorothy – our cutting-edge tunnel boring machine – has made history, becoming the first to safely and successfully breakthrough along the route,” he said.

“With Dorothy’s journey now concluded, I am looking forward to celebrating even more milestones throughout the rest of the year and beyond, as we continue to help build Europe’s largest infrastructure project.”

Creating both bores of the tunnel, the TBM is removing around 250,000 cubic metres of mudstone and soil, which is being transported to the on-site slurry treatment plant. There the material is separated out before being reused on embankments and landscaping along the route.

A 254m-long conveyor at the north portal site, which takes the excavated material over the Grand Union Canal, removes the equivalent of around 30,000 HGVs from local roads, reducing impacts on the local community and cutting carbon.

Over the next four months, the cutterhead and front section of the TBM will be dismantled and transferred back to the north portal, while the bulk of the machine will be taken back through the tunnel. It will be reassembled, ready to launch for the second bore of the tunnel.

HS2 will use 10 giant TBMs to create 103km of tunnels between London and the West, including major tunnels on the approach to London and Birmingham. Three machines have been launched so far.