This is the fourth twin-bore railway tunnel to start construction on the rail project. The 3.5-mile tunnel will take high-speed trains into Birmingham as they approach Curzon Street Station in the heart of the city.
The name of the TBM was revealed as ‘Mary Ann' after Mary Ann Evans, better known by her pen name George Eliot, who was an English novelist, poet, journalist, translator and one of the leading writers of the Victorian era. She was born in Nuneaton and her name was suggested by the Warwickshire community.
Attending the event, West Midlands Mayor Andy Street said: "This is a milestone moment for HS2 in our region. Now that work is underway on this tunnel, in a few years' time it will carry high-speed trains into Birmingham.
"It's a remarkable feat of engineering - testament to our skills base, industry expertise and workforce talent.
"I look forward to seeing the project progress over the coming months and years - continuing to generate jobs, training and economic opportunities for local people and businesses right across the West Midlands."
HS2 CEO Mark Thurston said: "It was fantastic to celebrate this big construction milestone on the HS2 project as the Bromford Tunnel TBM gets ready for its journey to build the tunnel into Birmingham. There are nearly 9,000 people in the West Midlands working on HS2, with a 450-strong team working on this particular operation.
"This is one of 350 sites well underway on HS2, helping to support over 400 firms in the region, with over £1.7bn of contract awards for local businesses so far. Work is still ramping up, with two stations in the West Midlands still to be built, so there are many more contracts up for grabs."
After final testing, the TBM will launch from a large underground box structure (160m x 30m wide x 15m deep), which forms the east portal of the tunnel. Over the last few months, sections of the machine - including the 8.62m diameter cutterhead - were lowered into the box where it was assembled.
A total of 20,797 segments will be put in place by the TBM, making 2971 concrete rings to form the tunnel. Each segment is two metres wide and 35cm thick, with each completed ring weighing around 49t.
The TBM will remove 1.87 million tonnes of excavated material, which will be sifted at the on-site slurry treatment plant and reused on nearby sites at the Delta Junction.
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