Tunnel milestone marks major HS2 progress in West Midlands
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The UK’s high-speed rail project, HS2, has achieved a significant construction milestone with the breakthrough of its final tunnel boring machine (TBM) in Birmingham. The machine, named Elizabeth, emerged at Washwood Heath after completing the 3.5-mile Bromford Tunnel, signalling the end of major tunnelling between London and the West Midlands.
Launched in March 2024 from Water Orton in Warwickshire, Elizabeth is the last of eight TBMs deployed to excavate the 23-mile twin-bore tunnel system between Old Oak Common in west London and Curzon Street in central Birmingham. Working alongside its sister machine, Mary Ann, which completed its journey earlier this year, Elizabeth helped remove more than 1.8 million tonnes of earth and installed over 5,800 concrete rings to form the eastbound and westbound tunnels.
The breakthrough at Washwood Heath marks a turning point in the project. With excavation complete, HS2 Ltd and its contractors can now shift focus to fitting out the tunnels with infrastructure necessary for high-speed rail operations.
Engineering feat beneath Birmingham
The Bromford Tunnel is one of the most technically complex sections of HS2. Crews operated at depths reaching 40 metres to navigate live infrastructure and challenging ground conditions, including Mercia Mudstone and multiple crossings of the River Tame. In some areas, headroom between the tunnel and surface was less than five metres.
The 125-metre-long TBMs functioned as underground factories, excavating and lining the tunnel simultaneously while advancing at an average rate of 10 metres per day. The works were carried out by main contractor Balfour Beatty VINCI (BBV), which mobilised a team of more than 450 specialists to manage tunnelling operations, spoil removal, and segment supply logistics.
The spoil excavated by Elizabeth and Mary Ann is being reused for landscaping works along the Birmingham approach, supporting HS2’s wider environmental goals. Sustainability measures also include the use of ground granulated blast-furnace slag in concrete mixes to reduce carbon emissions from the tunnel lining segments.
Preparing the tunnel for operation
With tunnelling concluded, construction now shifts towards internal works. These include the installation of walkways, ventilation shafts, cross passages and base slabs. Once complete, the tunnels will support 360 km/h (225 mph) train operations, forming part of the new backbone for rail travel between London and Birmingham.
Washwood Heath, the site of the breakthrough, will play a critical role in future HS2 operations. It will host the Network Integrated Control Centre and the main rolling stock depot, serving as the operational and maintenance hub for the line. The site’s proximity to Curzon Street and key transport links positions it as a strategic asset for long-term network performance.
Progress amid programme pressures
While the breakthrough represents a positive step forward, HS2 as a whole continues to face scrutiny over delays and rising costs. Chief Executive Mark Wild has initiated a comprehensive reset of the programme to ensure delivery in the most efficient and affordable way possible.
Other key civil engineering components remain under construction or in early stages of development, particularly the tunnel section connecting Old Oak Common to London Euston. Two additional TBMs are expected to launch next year to begin this final leg of excavation.
Despite programme challenges, the Birmingham breakthrough demonstrates tangible progress and engineering excellence. For the West Midlands, the project is more than a railway. It is central to regeneration efforts, with sites at Curzon Street, Solihull Interchange and Washwood Heath forecast to contribute £10 billion to the regional economy over the next decade.
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