Balfour Beatty VINCI's (BBV) tunnel boring machine (TBM) Mary Ann has completed carving out the first bore of the 5.8km Bromford Tunnel, marking a milestone in the construction of the High Speed Two (HS2) railway project in the UK.
The 125m-long tunnelling machine, named Mary Ann by the local community, started work on the project in July 2023.
In August 2024, the excavation project of the first bore of the Bromford Tunnel reached the halfway point.
The Bromford Tunnel stretches from the Warwickshire village of Water Orton to the north-east Birmingham suburb of Washwood Heath.
Upon completion, this tunnel is set to become the longest railway tunnel in the West Midlands and will alleviate congestion on the existing West Coast Main Line.
A team of 450 people from Balfour Beatty VINCI have worked to complete this section of the tunnel in less than two years, the company stated.
The second bore of the tunnel is anticipated to be completed later this year by TBM Elizabeth.
After the excavation, the focus will shift to fitting out the tunnel with the necessary infrastructure, including cross passages, concrete finishing works, base slabs, and emergency and maintenance walkways.
The team is stated to have operated the 1,600-tonne (t) TBM at depths of up to 40m, navigating under natural reserves, motorways, and the River Tame.
The Washwood Heath site, where Mary Ann broke through, is poised to become the 'nerve centre' for HS2's operations.
The Depot and Network Integrated Control Centre will be constructed adjacent to the tunnel portal. Here, trains will be serviced, stored, and the railway's real-time operations managed.
Throughout the tunnel drive, approximately one million tonnes of spoil were excavated and are being repurposed for the construction of the nearby Delta Junction, in accordance with HS2's sustainability policy.
The TBM advanced by around 30m every day. The crew is said to have worked in unison, with the cutterhead slicing through the earth while reinforcing the tunnel with precast concrete segments, each weighing up to 7t.
These segments were produced at Balfour Beatty VINCI's factory near Bristol, resulting in 2,971 concrete rings formed from 20,797 individual segments.
The project has also supported local employment and skills development.
Washwood Heath is one of the three key HS2 sites in the West Midlands, which also includes the construction of two new stations in Birmingham and Solihull.
BBV tunnelling director Jules Arlaud said: "Today’s breakthrough is a significant moment for Balfour Beatty VINCI, as we celebrate the arrival of our first tunnel boring machine into Birmingham. It’s been a challenging drive beneath critical live infrastructure and through complex ground conditions. I’m incredibly proud of our entire team, whose expertise, dedication and resilience has made this possible.
“This achievement follows years of design, planning and preparation from BBV, in close collaboration with HS2 and our partners. The team will now move onto the next phase of work inside and outside of the tunnel, while our second TBM, Elizabeth, continues to make great progress on the second drive.”
