The third of four TBMs excavating the 13.5km-long Northolt Tunnel beneath London has broken through.
TBM Emily, operated by HS2’s London Tunnels contractor, Skanska Costain Strabag JV (SCS JV), completed a 5.5km drive to arrive at Green Park Way in Greenford, west London on June 6.
The EPBM was launched in February 2024 and has completed one bore of the eastern section of the tunnel – removing 775,000 tonnes of London clay and installing 17,514 tunnel segments.
It is one of four TBMs deployed on the Northolt Tunnel – two building the western section from West Ruislip and two building the eastern section from Victoria Road in North Acton.
The machines all finish at Green Park Way where they will be lifted out from the shaft. The final machine is expected to complete its drive later this year.
The high water pressure in the ground at Green Park Way requires the TBMs to finish in a reception can in the shaft. This allows the TBM to maintain pressure while sealant can be applied from the tunnel lining, preventing water ingress. It is then depressurised before it is opened and the TBM is lifted out.
Manufactured by Herrenknecht, TBM Emily weighs 1,700 tonnes and has a 9.11m diameter cutterhead. At peak production, the TBM advanced at around 38m per day.
The London clay extracted was taken away from Victoria Road Crossover Box, near Old Oak Common station, by conveyor to the London Logistics Hub at Willesden Euro Terminal. From there, it was transported by rail and reused at sites in Cambridgeshire, Kent and Warwickshire.
Two other TBMs, Sushila and Caroline, bored the western section of the tunnel from West Ruislip, breaking through in December 2024 and April 2025, respectively.
In Birmingham, the first of two TBMs excavating the Bromford Tunnel broke through in May.
Dave Hannon, SCS JV’s project director, tunnels & routeway, said TBM Emily’s arrival at Green Park Way was a significant milestone in the HS2 programme.
“We are now approaching completion of the Northolt Tunnel – an exciting achievement and a testament to the collaboration, dedication, and technical capabilities of our teams,” he said.
“With our continued focus we are pressing ahead at pace to complete the remaining works, including cross-passages, tunnel walkways, ventilation shafts, headhouses, and portals, as we deliver on part of the HS2 project.”
Once the whole structure of the tunnel is complete, the SCS JV team will finish building the 34 cross-passages between the two tunnel bores. Track will be laid on the tunnel invert and the shafts that provide ventilation and emergency access will be completed.
TBM Emily was named after Emily Sophia Taylor who helped establish the Perivale Maternity Hospital in 1937 before becoming Ealing’s first female mayor in 1938.
