Launched in November 2022, it has taken just four months for the 2,000-tonne TBM to complete its second bore, making this the first complete twin-bore tunnel on the HS2 project.
The 1.6km (1 mile) twin-bore tunnel runs under Long Itchington Wood in Warwickshire, a designated Site of Special Scientific Interest (SSSI).
After completing the first bore of the tunnel in July 2022, the 125-metre long machine was dismantled and returned to the north portal where she was reassembled ready to start her second journey.
Dorothy, as the TBM is called, can now have a rest for a bit. Her next job is a 3.5-mile tunnel bore in early 2024, between Water Orton in Warwickshire and Washwood Heath in Birmingham.
Members of the Balfour Beatty Vinci (BBV) tunnelling team were on site at the southern portal to witness the return of Dorothy as her huge cutterhead broke through the reception box headwall. This marks the culmination of a three-year operation, from site set-up and TBM assembly, the first TBM drive and breakthrough, and now completing the second breakthrough.
Michael Dyke, chief executive of Balfour Beatty HS2 Major Projects, said: “Watching Dorothy break through her second one-mile journey today was only possible thanks to months of hard work and dedication from our 400-strong project team, who deserve a special mention for safely delivering this incredible feat of engineering.”
The tunnelling team has been working around the clock in shifts for four months to operate the TBM, which has placed 791 concrete rings, with each ring made from eight two-metre-wide segments that each weigh up to eight tonnes.
Over the next few weeks, work will begin to dismantle the shield from the TBM, while the rest of the machine will be pulled back to the start of the tunnel and disassembled, ready for transportation to east Birmingham. There, the TBM will be fitted with a new shield so that she can begin a 3.5 mile tunnel bore in early 2024, between Water Orton in Warwickshire and Washwood Heath in Birmingham.
David Speight, HS2 Ltd’s delivery director for main works civils on phase one, said: “This is a key moment in HS2’s operation in the Midlands, which is now reaching peak momentum... We’re looking forward to celebrating more milestones as work gathers pace on key structures such as the Delta Junction viaducts, Birmingham Curzon Street station, Interchange station and Washwood Heath Depot.”
There was an irony, however. On the very day that the tunnel under Long Itchington Wood was completed, HS2 Ltd was slapped with a tree preservation order to stop it doing any more damage to Sheephouse Wood [see Tree preservation order slapped on HS2].
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