The tunnel is now 93% complete as the tunnel boring machine (TBM) – named Caroline – has reached Green Park Way
Caroline is one of four TBM’s deployed to construct the HS2 Northolt tunnel.
The TBM’s journey saw five miles underneath London to a vent shaft in Green Park Way, Ealing.
The HS2 Northolt tunnel will be 8.4 miles long
The tunnel will be a twin bore tunnel leading from West Ruislip to the new Old Oak Common station.
Caroline, weighing 2,050 tonnes, broke through into an underground reception area which can be filled with foam concrete, allowed the installation of the 4,217th concrete tunnel ring and completed the 5-mile stretch.
The tunnel is being constructed via the ‘reception can’ method due to high water pressure in the ground. This method allows the TBM’s to maintain pressure and uses sealant on the tunnel lining to prevent water from bursting through. Before the tunnel is opened and once all sealant is in place, the can is depressurised, the tunnel is opened, and the TBM is lifted out.
The tunnel will be 8.4 miles long upon completion, and two machines, including Caroline, have been used for this western section, and two more are currently excavating the eastern section. All the machines will meet and be extracted at the Green Park Way vent.
The previous TBM used for this stretch was named Sushila, which completed its journey in January and has since been lifted out at Green Park Way.
The other two machines are boring the tunnel from Victoria Road Crossover Box, just outside of Old Oak Common, and they will complete their journeys this year.
This tunnel is one of five
Five deep twin-bore tunnels will comprise HS2 between London and the West Midlands. Two of these tunnels have already been completed, the Chiltern Tunnel and the Long Itchington Wood Tunnel, 10-miles and 1-mile long, respectively.
Malcolm Codling, client director for HS2 Ltd, said: “We’re immensely proud of the work we have done to complete the second breakthrough for the Northolt Tunnel underneath the capital. As we focus on delivering Britain’s new high speed railway between London and the West Midlands, we are gearing up for our most productive year to date on this stretch of the line.”
Richard Adams, managing director for Skanska Costain STRABAG joint venture, said: “The arrival of TBM Caroline at Green Park Way marks a significant milestone – the completion of the western section of the Northolt Tunnel – and is a testament to the dedication and skill of all our teams. Later this year two more TBMs, Emily and Anne, will finish their journeys, which will complete the 8.4-mile Northolt tunnel between Old Oak Common and West Ruislip.
“Work on the cross passages, tunnel walkways, ventilation shafts, headhouses and portals continues at pace as our team works at peak productivity to deliver our part of HS2, that will bring better journeys and boost economic growth.”
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