The HS2 tunneling team of Balfour Beatty/VINCI (BBV JV) celebrated the breakthrough of its tunnel boring machine (TBM) of the Long Itchington Wood Tunnel south portal in Warwickshire.
The TBM, named ‘Dorothy’ was launched in November 2022. The 2 kt (2,200 st) completed its one-mile second bore in four months, making this the first complete twin-bore tunnel on the HS2 project.
After completing the first bore of the tunnel in July 2022, the 125 m long TBM was dismantled and returned to the north portal where it was reassembled ready to start its second journey.
Members of the BBV JV tunneling team were on site to witness the dramatic moment when the 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.
“This is yet another ground-breaking moment in the delivery of HS2 and the transformation of journeys and communities across Britain,” Rail Minister, Huw Merriman said. “With the help of Tunnel Boring Machine Dorothy, these tunnels are paving the way for HS2 trains while preserving ancient woodland on the land above. These tunnels help ensure that we deliver this transformative project while protecting the natural environment.”
David Speight, HS2 Ltd’s Delivery Director for Main Works Civils on Phase One said in a statement, “I’d like to congratulate the 400-strong Balfour Beatty VINCI tunnelling team for achieving this fantastic milestone on the HS2 project. This is a key moment in HS2’s operation in the Midlands, which is now reaching peak momentum with over 400 businesses in the region already winning work, and 9,000 jobs supported.
“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, creating more opportunities for local businesses and people.”
Michael Dyke, Chief Executive Officer for Balfour Beatty HS2 Major Projects, added, “Successfully completing the first twin-bore tunnel on Britain’s new, highspeed railway is yet another demonstration of how works continue to progress at pace across the project. It’s a huge achievement, not only for Balfour Beatty VINCI, but for everyone connected with HS2.
“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 tunneling team have been working around the clock in shifts for four months to operate the TBM, which has put 791 concrete rings in place, with each ring made from eight, 2-m-wide segments that each weigh up to 8 t (8.8 st).
The tunnel, which preserves the ancient woodland above, forms a key element in how HS2 is managing environmental impacts through the design of the railway, protecting Britain’s precious wildlife habitats. Long Itchington Wood is classified as a Site of Special Scientific Interest (SSSI) with complex ecosystems that have taken hundreds of years to establish.
Excavation of the twin bore tunnel has produced around 500 kt (550,000 st) of mudstone, which is being processed at an on-site slurry treatment plant. From there, it is separated out before being transported by a 254 m conveyer to be used to build embankments along the route of the railway, removing the equivalent of around 30,000 HGVs from local roads, reducing impacts on the local community and cutting carbon.