The second of two tunnel boring machines has been launched from just inside the M25 to dig tunnels for HS2 under the Chilterns.

The second tunnel boring machine (TBM), called Cecilia after Cecilia Payne-Gaposchkin, an astronomer, started a month after the first, called Florence, named after Florence Nightingale. Despite starting second, Cecila will run slightly faster, aided by geological data fed back from Florence, meaning that both machines are due to breakthrough at the end of the tunnels at around the same time.

HS2 launch site just inside the M25 (c) HS2

Designed specifically for the mix of chalk and flints under the Chilterns, the two TBMs move at a speed of up to 15 metres a day. Each machine operates as a self-contained underground factory – digging the tunnel, lining it with concrete wall segments and grouting them into place. Each tunnel will require 56,000 fibre-reinforced segments – which will all be made on site.

A crew of 17 people will operate each TBM, working in shifts to keep the machines running 24/7. They will be supported by over 100 people on the surface, managing the logistics and maintaining the progress of the tunnelling operation.

Chalk excavated from the tunnels will be used for landscaping at the south portal site once construction is complete, creating wildlife-rich chalk grassland habitats across 127 hectares of the southern Chiltern hills.

In total there will be ten tunnel boring machines (TBMs) working to create 64 miles of tunnel between London and the West Midlands.


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  1. Derek Atkinson says:

    Surely they can go under the M42 at water Orton instead of going so high over the top.

  2. Brian Clark says:

    Is there a map published anywhere showing the route of the line.
    Am in Cambridgeshire so does not affect me at all. Just got an interest. Thanks

    • ianVisits says:

      It will affect you as the regional rail services will be able to run more trains to major cities thanks to the massive capacity increase on existing railways when the intercity services are moved over to the HS2 line. As for a map, there’s one on the HS2 website.

  3. David lea says:

    If crossrail is anything to go by having to wait another year, I could ask to when the first passengers will use the line. but as in crossrail add another 5 years which shpuld have been running long before 2012. Rant over. But seriously hoping for a realistic date as the wouldn’t be the problemsike crossrail. Btw when I travel into London to connect with HS2 as I would travel to Manchester where would I join hs2?

  4. Simon Haynes says:

    David there is a new International Hub Station being built at Old Oak Common which will be an interchange for trains from Europe connecting to Birmingham/Manchester etc. although the line will finish at Euston.
    Only Align have started on their 2 x 16kM tunnels and already 600m in with the 1st TBM. i don’t believe the 2nd TBM has started yet but is imminent – we are the main sun contractor for supply of TBM utilities supporting steelwork which includes bracketry to support all pipes and cables and walkway.
    BBV jv are starting on their 1.8kM tunnel at Long Itchington (Royal Leamington Spa) in October, again we are main sub-contractor for same on this tunnel too.
    SCS jv will be starting on their 48kM of tunnels in London (Northolt and Euston) next April 2022.
    Tunnel fit outs will start in 2025 so wouldn’t expect the first trains to run until 2030 but with a completion date of 2040 but with a long leadtime it’s difficult to guarantee at this stage.

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