HS2’s Northolt Tunnel Reaches Major Milestone
HS2 engineers have achieved a significant feat by completing a five-mile tunnelling drive under the capital. The giant Tunnel Boring Machine, known as Sushila, successfully reached the Green Park Way vent shaft in Ealing, marking a crucial milestone in the project. This week, Sushila broke through into a reception can filled with foam concrete, showcasing an innovative method implemented due to high water pressure in the ground on the site.
Meet the Tunnel Boring Machines
The 8.4-mile twin-bored Northolt Tunnel is currently under construction by a quartet of machines named Sushila, Caroline, Emily, and Anne. These machines will play a pivotal role in connecting high-speed trains between HS2’s super-hub station at Old Oak Common and West Ruislip. Sushila, the first to start its journey, has also become the first to complete it, reaching the Green Park Way where all four machines will conclude their missions.
Construction and Operation
The impressive feat of constructing the Northolt Tunnel is carried out by a joint venture comprising the companies Skanska, Costain, and STRABAG (SCS). Operating like underground factories, each machine excavates the tunnels, lines them with pre-cast concrete tunnel segments, and grouts them into place, advancing at an average speed of 16 meters per day. The teams involved in this operation work tirelessly around the clock, both below ground on the borers and on the surface to support them.
Environmental Impact and Future Plans
The construction of the Northolt Tunnel not only signifies a major infrastructure development but also highlights HS2’s commitment to environmental sustainability. The earth excavated during the tunnelling process has been strategically placed in designated areas west of the tunnel, eliminating the need for public road transportation. These areas will be transformed into wildlife meadows and wooded spaces as part of HS2’s Green Corridor initiative.
Malcolm Codling, HS2 Client Director for the London Tunnels, expressed his pride in achieving this breakthrough, attributing it to years of hard work by the tunnelling contractor. With the project on track to complete the first tunnel for HS2 trains under the capital by the end of 2025, anticipation grows as preparations are made to extend HS2 tunnels into Euston, marking a significant leap in the UK’s high-speed rail infrastructure.
