After completing the three-and-a-half-mile mission to excavate the first section of the Bromford Tunnel linking North Warwickshire and Birmingham, a giant HS2 tunnel boring machine is getting ready for its next job.

The first stage in the process to disassemble the 1,600-tonne machine saw the TBM’s 8.62-metre diameter cutterhead being lifted into the Birmingham skyline by a giant 700-tonne crawler crane.

The cutterhead, which weighs 120 tonnes, was lifted out of the 22-metre-deep tunnel portal at Washwood Heath in north Birmingham in just 90 minutes.

The 125-metre-long machine is being dismantled by a team of specialist engineers working for HS2's construction partner, Balfour Beatty VINCI

A team of 15 engineers will spend the next three months dismantling the 125-metre-long machine, next to the portal in Washwood Heath, before it is returned to the German tunnel boring company Herrenknecht.

The giant machine named Mary Ann, which spent 652 days and nights working underground to excavate the first bore of the Bromford Tunnel, is expected to be refurbished and adapted ready to meet the technical requirements of its next tunnelling mission.

TBM Elizabeth is currently boring the second section of the Bromford Tunnel with breakthrough expected later this year.

Meanwhile, engineers working for the HS2 project have slid the first part of a major 320-metre-long viaduct into position that will carry high speed trains across the M6 near Birmingham Airport.

The first stage of the project – delivered this weekend – saw the ‘East Deck’ of the M6 South viaduct slid 119m out over a slip road adjacent to the motorway.

To reduce disruption for motorists, the viaduct deck is being assembled to one side and slid across the motorway over three weekends, with each part pushed out before later sections are added behind them.

This multi-stage process means that the weight of the deck will increase with each push from 1,3000 tonnes this weekend, to 3,290 for the final slide. These subsequent slides will take the deck out over the main M6 carriageway and then finally the M6-M42 link roads.

The weight includes pre-cast concrete deck slabs on top of the steel structure. Launching the viaduct with the deck units already in place further reduces the number of closures of the motorway.

The East Deck will carry two tracks taking trains towards London while an adjacent ‘West Deck’ will carry a further two tracks for services heading to Birmingham and further north. This will be assembled and slid out next year using the same technique.

Liam Kenney, HS2 senior project manager, said: “It’s great to see the first section of the East Deck in position over the weekend. Once complete, these twin viaducts will carry high speed trains over the M6 helping to improve journeys and free up space on the existing rail network for more freight and local services.”

The complex operation is being led by HS2’s main works contractor, BBV – a team made up of Balfour Beatty and VINCI, supported by specialist steelwork company Victor Buyck Steel Construction (VBSC). The team are working closely with National Highways and other key local stakeholders including the NEC and Birmingham Airport.