Construction of HS2’s Gateway to Birmingham has reached a significant milestone, as the first bore of the 5.6-kilometre tunnel reaches the halfway point.
Balfour Beatty VINCI JV (BBV) began gigging work on the Bromford Tunnel last year from a large underground box in Water Orton.
The 125-metre-long, 1,600 tonne tunnel boring machine (TBM), ‘Mary Ann’ completed excavation and building of 2.8 kilometres of the first bore.
This follows a series of HS2 milestones with the installation of 83 giant concrete beams for a 91-metre bridge for the West Coast Main Line by BBV, as well as the completion of eight-month work to slide the 3,700 tonne deck of the Wendover Dean Viaduct into position earlier this month.
The TMB has excavated under the Park Hall Nature Reserve and River Tame, next to pass under Castle Vale, having driven around 40 metres underground towards its final destination, Washwood Heath in Birmingham.
It is expected to travel under the M6 before reaching Washwood Heath early next year.
The tunnelling team worked across round the clock shifts to operate the boring machine, which builds the tunnel as it excavates.
In total, 20,797 concrete segments are to be put in place by the machine, making 2,971 concrete rings to form the tunnel.
The tunnel’s 47-metre-deep ventilation shaft at Castle Vale marks the halfway point of the TBM.
A ‘headhouse’ will be built on top of the shaft, and the whole structure will be complete in 2027.
In March this year, the second TBM building HS2’s longest tunnel under the Chiltern Hills, reached its final breakthrough at tunnel’s northern portal early, completing a journey that began in June 2021.
‘Elizabeth’, the second TBM for Bromford tunnel began work on the second bore in March this year and is due to finish late 2025.
The two TBMs will remove 1.87 million tonnes of excavated material, which is being sifted at the on-site slurry treatment plant and reused on nearby sites at the Delta Junction.
In preparation for the arrival of the TBMs at Washwood Heath, 130 people have completed an earthworks operation to build the tunnel’s west portal.
The portal is 22 metres below ground and is the deepest of the four tunnel portals on the Midlands section of the HS2 route.
It is at the start of a 750-metre-long cut and cover structure, which is currently being excavated and built, and where HS2 trains will emerge from the Bromford Tunnel, before raising up onto a series of viaducts through Birmingham’s industrial heartland and into Curzon Street Station.
The first HS2 trains are expected to roll off the production line around 2027 with the first passengers expected to be carried between 2029 and 2033.
Jules Arlaud, tunnelling for Balfour Beatty VINCI said: “Reaching the halfway point on this complex stretch of the HS2 route into Birmingham is a great milestone for our 180-strong tunnelling team.
“We’re looking ahead now to delivering the final stages of tunnelling, and celebrating the breakthrough of both TBMs at Washwood Heath next year.”
Steve Powell, HS2’s Head of Delivery said: “We’re now at peak construction in the West Midlands, and it’s great to celebrate the halfway point for the ‘Mary Ann’ tunnel drive into Birmingham.
“By the end of next year, both of these tunnels will be built, marking a significant step in HS2’s construction in the region.
“Around 31,000 people are working on HS2, with around a third of these in the West Midlands including 615 apprentices and over 1,650 people who were previously unemployed, providing a unique opportunity for local people to learn new skills while delivering the UK’s largest construction programme.”
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