HS2 dismantles giant TBM Mary Ann for refurbishment

The HS2 project has marked another major milestone in its Midlands tunnelling programme, with the dismantling of tunnel boring machine (TBM) Mary Ann following the completion of the first 5.6-kilometre bore of the Bromford Tunnel between North Warwickshire and Birmingham.

On 30 May 2025, the 120-tonne, 8.62-metre diameter cutterhead was lifted from a 22-metre-deep portal at Washwood Heath using a 700-tonne crawler crane. The operation – executed in just 90 minutes – signalled the beginning of a three-month dismantling process managed by a 15-strong engineering team from Balfour Beatty VINCI, HS2’s construction partner.

The 125-metre-long TBM, manufactured by Herrenknecht, had spent 652 days boring the northbound tunnel beneath urban Birmingham. Once fully stripped down, the machine will return to Germany to be refurbished and adapted for future use.

Its sister machine, TBM Elizabeth, continues work on the parallel southbound tunnel and is expected to break through later this year.

The use of large tunnel boring machines – and the efficient disassembly and reuse of such equipment – is of growing interest across the concrete sector, especially for projects involving sprayed concrete lining (SCL), segmental ring installation, and deep geotechnical foundations.