HS2’s tunnelling team has reached a major milestone in the construction of the Northolt Tunnel, which stretches 8.4 miles between West Ruislip and Old Oak Common. The team has successfully completed half of the tunnel, thanks to the hard work of four boring machines (TBMs).
These TBMs, including Sushila, Caroline, Emily, and Anne, are responsible for excavating a total of 16.8 miles of tunnel, with two bores covering the 8.4-mile length of the Northolt Tunnel. This tunnel is now the second longest on the new railway, following one recently built beneath the Chiltern Hills.
The first TBM, Sushila, was launched from West Ruislip in October 2022, followed by TBM Caroline a month later. Both machines will complete five miles of the route before reaching the Green Park Way vent shaft in Greenford, marking over half of their journey’s completion.
TBM Emily began its westward journey from Old Oak Common in February, while TBM Anne joined in May. Together, these machines will cover 3.4 miles of the tunnel, contributing to the overall progress of the project.
The TBMs operate like underground factories, excavating the tunnels, lining them with pre-cast concrete segments, and grouting them into place. They move forward at an average speed of 16 meters per day, with teams working tirelessly around the clock to support their progress.
In addition to tunnel excavation, other important features such as cross passages, vent shafts, and headhouses are being installed as the TBMs advance. The quartet of machines has already excavated nearly two million tons of earth, showcasing the scale and scope of the project.
Furthermore, the excavated material from the West Ruislip portal is being utilized to re-model a nearby golf course impacted by the tunneling activities. This sustainable approach demonstrates HS2’s commitment to minimizing environmental impacts and maximizing resource efficiency.
With two of HS2’s tunnels already completed and preparations underway for the final tunnel between Old Oak Common and Euston, the project is steadily progressing towards its completion. Two additional TBMs are expected to arrive in the UK this summer to continue the tunneling efforts, bringing HS2 one step closer to becoming a reality.
