HS2’s TBM ‘Mary Ann’ has broken through today, marking the end of her mission to excavate the first bore of what will soon become the longest railway tunnel in the West Midlands.
The 125m long, 8.62m diameter Herrenknecht machine began constructing the 5.8km Bromford Tunnel, which starts at the Warwickshire village of Water Orton and extends to the northeast Birmingham suburb of Washwood Heath, in July 2023.
The tunnel breakthrough – HS2’s first in Birmingham comes as construction work on the giant structures being built to carry HS2 hits a peak, with around 31,000 people now employed on the programme across the 224km route. Despite recent progress, HS2 is currently undergoing a fundamental reset to make sure the railway can be delivered efficiently and for the lowest feasible cost.
Beatty VINCI (BBV), worked around the clock, for just under two years, to complete the first section of the tunnel. The second bore is expected to be completed later this year by TBM Elizabeth. Following the excavation, teams will begin fitting out the tunnel with cross passages, concrete finishing works and base slabs, and emergency and maintenance walkways.
During the 22-month-long mission, the team worked at depths of up to 40m navigating Mary Ann under the Park Hall Nature Reserve, the M6 motorway, and the meandering River Tame – which they crossed four times, with a headspace as low as five metres.
The Washwood Heath site, where Mary Ann broke through, will soon become the nerve centre for HS2’s operations. Next to the tunnel portal, HS2’s Depot and Network Integrated Control Centre will be built. From this site, trains will be serviced and stored, and the real time operation of the railway will be controlled.
Mary Ann excavated around one million tonnes of spoil during the tunnel drive. In line with HS2’s sustainability policy, the excavated earth is being reused to support construction of the nearby Delta Junction, a complex network of 13 viaducts that will enable high speed trains to travel between London, Interchange Station in Solihull and Birmingham Curzon Street Station. The excavated material is transported via dedicated haul roads to minimise the number of construction vehicles on public roads.
At peak production, the TBM advanced at around 30m per day, lining the excavated tunnel with two metres wide and 35cm thick concrete segments – each weighing up to seven tonnes.
The precision-designed segments were manufactured at Balfour Beatty VINCI’s pre-cast factory at Avonmouth near Bristol. The TBM lined the tunnel walls with 20,797 individual segments, making 2,971 concrete rings to form the tunnel.
Jules Arlaud, Balfour Beatty VINCI’s Tunnelling Director 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.”
BBV’s tunnelling team includes eleven local apprentices who were recruited and upskilled for the job in partnership with Solihull-based Rorcon and national tunnelling experts Tunnelcraft. Tunnelling is a recognised skill-shortage in the UK and HS2’s drive to recruit and upskill local talent is helping to create the next generation of tunnellers.
In the West Midlands alone, around 10,000 people are currently supporting HS2’s vast construction programme. 710 people from the region have secured an apprenticeship on the project and 1,870 people who were out of work have started new careers. Local firms are also playing a major role in the construction programme, with over 400 local businesses now actively engaged in HS2’s supply chain.
Washwood Heath is one of three key HS2 sites in the West Midlands, alongside the two new stations that will be built in Birmingham and Solihull. Collectively, the three sites have become a magnet for property investors and developers, spearheading multibillion-pound redevelopment projects in the areas nearby, which is forecast to add £10bn to the region’s economy over the next 10 years.
Herrenknecht
Pioneering Underground Technologies - Herrenknecht AG is the technology and market leader in mechanized tunnelling. As the only company worldwide, Herrenknecht delivers cutting-edge tunnel boring machines for all ground conditions and in all diameters - ranging from 0.10 to 19 meters.
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