Inside the giant machine digging HS2's railway tunnels to Euston station

"It is the last of the 11 giant tunnel boring machines (TBMs) used to dig HS2's railway tunnels. Another machine launched in January, and the pair are expected to reach Euston around the middle of next year. The TBMs were assembled inside Old Oak Common station, then pushed down a wide tunnel hand-dug to create space for railway tracks to crossover."

"Unlike some tunnelling projects where machines are dismantled and removed, these TBMs will effectively be left underground. The huge underground cavern that trains will eventually enter at Euston has not yet been excavated. When the machines arrive at Euston, they will stop dead in the ground. Most of their long trailing structure will be dismantled and taken back to Old Oak Common."

"When the Euston cavern is later excavated, the cutting head will be removed, but the surrounding casing will remain permanently in place. In effect, future HS2 trains will pass through the middle of the machine that originally dug the tunnels."

HS2 launched its eleventh and final tunnel boring machine (TBM) in west London, named after Karen Harrison, the UK's first female train driver. This nearly 200-metre-long machine is excavating the second tunnel connecting Old Oak Common station to Euston, with a companion machine launched in January. Both machines are expected to reach Euston by mid-next year. Unlike typical tunnelling projects where machines are removed, these TBMs will remain largely underground. When arriving at Euston, the machines will stop and their trailing structures will be dismantled and returned to Old Oak Common. However, the front cylindrical cutting head section will remain embedded permanently in the ground, with future HS2 trains passing through the middle of the original boring machine.

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