Far left:
HS2’s Old Oak Common launch and support area for part of Euston Tunnel works
Left:
View down tunnel from front of TBM Karen in underground launch area
Midlands, the Heathrow Express, and the Elizabeth Line to Central London – this last with a journey time of just ten minutes. On the western side of the Old Oak Common box, a
short shotcrete-lined tunnel will connect the station to the Victoria Road Crossover Box nearby. From there the new high-speed line will run through the Northolt Tunnel – the excavation stage of which was completed in mid-2025 – and thence trains will travel on, towards Birmingham, with other tunnels along the way.
Running westward from the capital the tunnel
diameters increase in stages to allow for the higher speeds of the trains as they accelerate out of Euston or decelerate upon approach to the terminus: the piston effect of air passing between the train and the tunnel walls decreases with decreasing speed, so in Euston Tunnel – the slower, end stage of the southern portion of HS2 – less free space is necessary for air to pass between train and tunnel walls.
EUSTON TUNNEL The twin HS2 tunnels towards Euston lead out of the eastern side of the Old Oak Common cavern. he tunnels are being excavated by two TBMs. TBM Karen is the eleventh, and last, of the TBMs on the
high-speed rail project. The Herrenknecht earth pressure balance (EPB)
machine has a cutterhead diameter of 8.53m; with the segmental lining, both parallel tubes will have finished internal diameters of 7.55m. The TBM has 11 gantry sections, giving the entire
machine and backup a total length of 198m. Michael Wilson is the chief operator. “We shall be
rotating the cutterhead at around three revolutions per minute, and each pass makes a 15 centimetre cut; which means the TBM will excavate at a rate of around 45 centimetres a minute,” he says. There is an onboard control cabin but the TBM also can be entirely controlled remotely from a ground station. The TBMs will be working 24/7 and the engineers
expect progress rates of up to 150m per week as they drive towards the Euston station site. Then, they are to go farther, to reach the Euston cavern by late June 2027. The Euston cavern is about 1km north of where the proposed station will be and that final section is the responsibility of a new body, Euston Delivery Company, which was formed in November 2025 to oversee development of the whole Euston site.
May 2026 | 19 Left:
Backup of TBM Karen in the launch cavern
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