First tunnelling breakthrough for HS2

HS2 tunnelling breakthroughHS2 Ltd marks on July 26 the first HS2 tunnelling breakthrough in Warwickshire, the 2,000-tonne TBM named ‘Dorothy’ completing its 1.6 km 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 22 July.

“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,” HS2 Minister Trudy Harrison said.

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

A 254 metres 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 brought back through the tunnel. It will be reassembled, ready to launch for the second bore of the tunnel.

The HS2 tunnelling breakthrough was possible by involving 400 people working for HS2’s main works civils contractor Balfour Beatty Vinci joint venture (BBV JV). The tunnelling team has been working around the clock in shifts for seven months to operate the TBM, which has put 790 concrete rings in place, with each ring made from eight 2-metre-long segments. The tunnel preserves the ancient woodland above, which is classified as a Site of Special Scientific Interest (SSSI) and has complex ecosystems that have taken hundreds of years to establish.

“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,” the CEO of HS2 Mark Thurston said.

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