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In order to advance the digging process of the 1.6km (one mile) high-speed railway on the HS2 project, Balfour Beatty Vinci (BBV) has launched Dorothy TBM for the second time.

Excavation of the second tunnel beneath Long Itchington Wood in Warwickshire, will be up to this TBM which is 125m long, whereas its initial startup was in December 2021 and completed the first tunnel drive (the first on HS2) in July.

Also the determined date for completion of the second bore is summer 2023.

The TBM’s gantries, with more than 1,000 tons of weight, were taken back through the tunnel and reassembled at the north portal over the four months since the breakthrough. While the 10m-diameter cutterhead, weighing 160 tons, was moved by road in September, the TBM's 130-tonne tail skin and eight other large pieces from the TBM’s front shield and middle shield were also transported by specialist equipment.

Despite this being the sixth tunnel commission on the project, the first time a TBM has been reassembled and reused. The responsibilities of the other four other TBMs that are in the ground now are boring twin-bore tunnels under the Chilterns and London. By launching the TBM in the coming summer, Long Itchington Wood Tunnel is going to be the first twin tunnel to be completed on HS2.

According to BBV tunnels delivery director Neil Johnson: "It had been an intense four months for the 300-strong team, including an intricate logistical operation to safely transport the TBM’s giant cutterhead and tail skin back to the north portal."

The quantity of generated mudstone and soil due to the excavation of the twin-bore tunnel will be almost 500,000 tons. In order to be used to build embankments along the railway, the spoil is processed at an on-site slurry treatment plant and separated out before being transported by a 254m conveyor.