HS2 has celebrated a major tunnelling milestone with the final breakthrough of the gigantic tunnel boring machine (TBM) excavating the approach to Birmingham. The completion of this drive marks the end of all deep bore tunnel excavation work between London’s Old Oak Common and the West Midlands terminus at Curzon Street.
The 125-metre-long TBM, named Elizabeth after the 19th-century philanthropist Elizabeth Cadbury, emerged at Washwood Heath this morning, having been launched near the Warwickshire village of Water Orton in March 2024.
Bromford Tunnel Complete
Elizabeth was one of two identical TBMs used to dig the 3.5-mile long Bromford tunnel, which will carry high-speed trains beneath the M6 motorway and the eastern outskirts of the city. The first TBM, Mary Ann, broke through earlier this year.
Together, Elizabeth and Mary Ann excavated more than 1.8 million tonnes of material and installed 5,804 concrete ring segments for the twin, eastbound and westbound tunnels. The excavated spoil, consisting mainly of Mercia Mudstone, is being repurposed to landscape the railway on the approaches to the city.
Today’s breakthrough means that all excavation is now complete for the 23 miles of deep bore tunnel across the first phase of the line. Construction teams are now focused on internal fit-out, including internal walkways, ventilation shafts, and cross passages.
Alan Morris, HS2 Ltd’s Construction Delivery Director, said: “Today’s breakthrough is a major milestone for the tunnelling team here in Birmingham and for the HS2 project. All eight of the TBMs digging our tunnels between Old Oak Common and Curzon Street have now broken through, which means that the focus is now on the internal concrete work, ventilation shafts and cross passages. I’m immensely proud of the men and women who have worked round the clock to bring our TBMs and their crews home safely, and I look forward to seeing more progress inside the tunnels in the years ahead.”
Complex Engineering Feat
The Bromford tunnel was delivered by HS2’s main works contractor Balfour Beatty VINCI (BBV). The 1,600-tonne machines operated 24/7 at depths of up to 40 metres for over a year and a half, moving at an average speed of around 10 metres per day.
The team skilfully guided the TBMs under complex critical live infrastructure, including the M6 motorway, key National Grid infrastructure, and the meandering River Tame, which they crossed four times with a headspace as low as five metres.
Jules Arlaud, Balfour Beatty VINCI’s Tunnelling Director, said: “Today is a historic moment for Balfour Beatty VINCI, as TBM Elizabeth completes her three-and-a-half-mile journey in Washwood Heath. This is BBV’s fourth and final TBM breakthrough, delivered by our expert tunnelling team who’ve worked around the clock over 19 months to arrive at this point. A sense of achievement and pride is felt by everyone connected with the project and follows years of planning and preparation. This has allowed us to guide Elizabeth safely and successfully underneath complex ground conditions and critical live infrastructure, including energy networks, the M6 and the River Tame. A breakthrough is always a unique moment, and it marks the culmination of exceptional engineering, dedication, and collaboration.”
A Magnet for Regional Growth
Washwood Heath, the arrival point for the TBMs, is set to become the nerve centre for HS2’s operations. Adjacent to the tunnel portal, the Depot and Network Integrated Control Centre will be built, where trains will be serviced and the real-time operation of the railway controlled.
This site, along with the two new stations planned for Birmingham and Solihull, has become a magnet for property investors and developers. These three key HS2 sites in the West Midlands are forecast to add £10 billion to the region’s economy over the next 10 years.
The project has so far utilised eight TBMs, excavating an incredible 9.4 million tonnes of material across the longest tunnel under the Chilterns (10 miles) and the Northolt tunnels (8.4 miles). While the tunnelling milestone marks a significant achievement, other parts of the civil engineering are reported to be further behind, leading Mark Wild, HS2 Ltd’s chief executive, to lead a comprehensive reset of the programme to deliver the railway as efficiently as possible and for the lowest reasonable cost.
Two more TBMs are expected to launch next year to begin digging the tunnels from Old Oak Common towards the final destination, London Euston.
