The first contracts for two new giant tunnel boring machines have been signed to dig HS2 tunnels under North-West London.

The tunnel boring machines (TBMs) are being built in Germany by Herrenknecht, who also built the Crossrail TBMs, and will be delivered to the site in the UK by the end of 2021. They are being designed and manufactured specifically for the London clay and chalk ground conditions they will bore through.

The HS2 tunnels, at 13 miles in length are coincidentally the same length as the Crossrail tunnels – but with a diameter of 8.8 metres, they are much larger than Crossrail’s 6.2 metre diameter tunnels.

Once the first new TBMs have been built, they will be transported by sea before being delivered to the site at the end of 2021. Once assembled, they will begin the tunnel drive from mid 2022, until completion at the beginning of 2024.

The London tunnels will begin just outside of Euston station and will be below ground until they emerge in West London at Old Oak Common station. The route will continue underground from Old Oak Common to the outskirts of West London.

These first two London TBMs will be launched from a portal at West Ruislip and will travel 5 miles east, creating the western section of the Northolt Tunnel. Once they arrive in Greenford the machines will be extracted from the ground and the site will then be used as a vent shaft. The 8.4 mile tunnel will be completed with a 3.4 mile tunnel drive from Old Oak Common using two further TBMs which are yet to be ordered.

A second tunnel between Euston and Old Oak Common will complete the remaining 4.5 miles of London tunnel between the two HS2 stations.

Overall there will be 10 TBMs purchased to construct the 64 miles of tunnelling along the HS2 route between the West Midlands and London.


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  1. Nick says:

    Are these all single use?

    • Jimbo says:

      The cutting head of a TBM is essentially disposal as they wear out, and often these are left in situ in side tunnels. The rest of the TBM, which can be hundreds of metres long, is usually sold back to the manufacturer who breaks it down and re-uses it.

  2. Andrew Gwilt says:

    What is happening to the New North Main Line. Will it reopen so that Chiltern Railways can use it and to bring back the “Parliamentary service” between London Paddington and West Ruislip. Or is that to be unused because of HS2. Whilst HS2 will be built underground from London Euston to rural Buckinghamshire.

    • Ryan says:

      It’ll remain unused because it would conflict with the intensive Crossrail service along that stretch of the GWML.

    • Julian says:

      There is a possibility that it might be reinstated to allow trains to feed into a new Old Oak Common interchange. However the chance of seeing through trains to Paddington again is infinitesimal.

    • Paul says:

      I believe Chiltern’s biggest constraint is the capacity at Marylebone, so it’s conceivable that one day additional services could be provided to/from Old Oak Common in the High Wycombe direction, though by no means certain.

  3. J, Elson. says:

    The quote on the HS2 map “lowest depth is 50m below ground” is, I am afraid, another product of the HS2 fiction department.

    I live in Primrose Hill & the line goes right under my house. My underground rights have been compulsorily purchased for £100, which I have not received. My ground heat pump system which goes down to 6 metres will probably be destroyed as, after 5 attempts to find out, HS2 eventually admitted the tunnel crown will be 5 metres from the floor of my basement.
    My cellar is 3 metres below ground. 5 metres plus 3 metres is 8 metres, not the absurd 50 metres invented by an HS2 PR man.

    I am a rail fan which is why I live near to the WCML, so the loss of my £22,000 heat system is a price I will begrudgingly pay for HS2. However I do wish they told the truth.

    • ianvisits says:

      50 metres below ground is the deepest it will be, not the shallowest — the shallowest being the millimetre just before it emerges to daylight.

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