The giant 125 tonne cutterhead being moved into place

Second TBM Takes Shape for HS2's Bromford Tunnel

A pivotal moment has been achieved in the construction of HS2's Bromford Tunnel, as the second tunnel boring machine (TBM) has been successfully assembled, ready to commence its subterranean journey through the Midlands.

Over the past few months, a team of 90 engineers has meticulously pieced together the machine, employing two 600-tonne cranes to lift the 125-tonne cutterhead into place at the front of the 125-metre long TBM.

This advancement marks a significant step forward in the realisation of HS2's vision with the Bromford Tunnel, spanning 3.5 miles, will serve as a vital link in this infrastructure project. The programme includes designers from Balfour Beatty VINCI’s Design Joint Venture, made up of Mott MacDonald and SYSTRA (MMSDJV).

The first TBM, dubbed 'Mary Ann' in honour of Victorian novelist George Eliot, commenced its excavation work in August 2023, already laying over 500 tunnel rings, amounting to approximately 0.6 miles of the tunnel's total length.

The second TBM, yet to be named, is scheduled to embark on its mission in the spring of 2024, joining its fellow machine in carving out the twin bore tunnel. 'Mary Ann' is expected to break through at the end of 2024, while the second TBM is projected to complete its journey by mid-2025.

Both TBMs will play a crucial role in excavating a staggering 1.87 million tonnes of material, which will be processed at an on-site slurry treatment plant before being repurposed on nearby HS2 sites, including Delta Junction.

In a statement, HS2 senior project manager Catherine Loveridge said:  With the first TBM ‘Mary Ann’ well on her way building the tunnel to take high speed trains into central Birmingham’s Curzon Street Station, it’s fantastic to see the second TBM assembled and being prepared to start digging.

“We’re now at peak construction, with over 9,750 people working on HS2 in the West Midlands and around 450 people working on this site, including many from the local area. Launching the second TBM next year means there will be more exciting jobs up for grabs for local people.”

A noteworthy aspect of the second TBM's design lies in its re-use of components from HS2's recently completed Long Itchington Wood Tunnel. The gantries, centre part of the cutterhead, and other essential elements have been carefully dismantled, transported to the Bromford Tunnel site, and reassembled within the underground launch area.

The Bromford Tunnel project is being spearheaded by a team of approximately 450 people, with a specialised tunnelling team, supplemented by apprentices working for BBV's sub-contractor Tunnelcraft, who will operate the TBMs around the clock.  Each bore will take an estimated 16 months to complete.

Jules Arlaud, tunnelling director for Balfour Beatty VINCI said: “Completing the assembly of the second tunnel boring machine is another major achievement for the team working on HS2’s Bromford Tunnel - a complex section of the new high-speed railway.

“Getting to this stage has required a huge amount of planning and preparation, including the disassembly and transportation of ‘Dorothy’ parts from Warwickshire, which forms the majority of the second TBM.

“Over the next few months, the team will be busy testing, checking and carrying out the final preparations, to make sure the machine is ready to start digging in spring next year.”

Photo Credit: HS2


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