Dorothy the TBM, via HS2

HS2’s historic date with Dorothy

Today marks the celebration of HS2’s tunnelling breakthrough within the infrastructure project, coming in the form of a 2,000-tonne, 125m long tunnel boring machine (TBM) named ‘Dorothy’ – after Dorothy Hodgkin, who in 1964 became the first British woman to win the Nobel Prize in Chemistry. This machine has officially completed a one-mile dig under Long Itchington Wood in Warwickshire.

The TBM began its tunnelling process at the tunnel’s North Portal in December 2021, finally breaking through the wall of the reception box at the South Portal site on Friday 22 July. This monumental milestone for the HS2 project has been delivered by the main works civils contractor Balfour Beatty VINCI (BBV JV), with a team of almost 400 people.

This tunnelling team have worked tirelessly for a course of seven months to operate the TBM, which has put 790 concrete rings in place, with each ring made from eight two-metre-long segments in this time span. This process has been a delicate operation as above the tunnel is a historic woodland that has been classified as a Site of Special Scientific Interest (SSSI) with a complex ecosystem. As has been a constant throughout HS2’s expansion, local habitats have been protected and incorporated into designs wherever possible to ensure environmental stability.

HS2 Ltd.’s CEO Mark Thurston said:

“This is a historic moment for the HS2 project, and I’d like to congratulate 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.

“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.”

Dorothy operates via the removal of around 250,000 cubic metres of mudstone and soil through the bored tunnels, which is then transported through the on-site slurry treatment plant. This wastage is then separated out and reused for the work on the embankments and landscaping along the route, creating sustainability within the project.

The excavated materials are transported over the Grand union canal via a 254-metre-long conveyor at the north site, whilst also removing the equivalent of around 30,000 HGVs from local roads. This significantly cuts the carbon impact of the project, aiding to achieve the Governments ambition for net-zero by 2050.

HS2 Minister Trudy Harrison said: 

"This is, quite literally, a ground-breaking moment - demonstrating that we are getting on with delivering on our promises and progressing our transformative plans to boost transport, bring communities together and level up the North and Midlands.

“As Dorothy paves the way for journeys between Birmingham and London, we continue to strive towards delivering a greener, faster, and more direct transport network. And as we deliver alongside our record-breaking Integrated Rail Plan, we’re boosting the economy, delivering over 25,000 jobs.”

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 brought back through the tunnel. It will be reassembled, ready to launch for the second bore of the tunnel.

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