HS2 Northolt Tunnel: Celebrating the Halfway Mark

HS2's Northolt Tunnel project has reached an impressive milestone, with half of the 8.4-mile twin-bore tunnel now complete. This achievement is the result of relentless efforts by four tunnel boring machines (TBMs) named Sushila, Caroline, Emily, and Anne. These machines are creating the tunnel that will facilitate high-speed rail travel between West Ruislip and Old Oak Common, enhancing the connectivity of HS2's network.

Engineering Excellence in Action

The four TBMs are working tirelessly to excavate a total of 16.8 miles of tunnel—8.4 miles for each bore. The first TBM, Sushila, began its journey from West Ruislip in October 2022, followed by Caroline. Together, they will complete the first half of the tunnel, reaching Greenford. TBM Emily and TBM Anne, which started from the Victoria Road Crossover Box site near Old Oak Common, are also making significant progress, each set to excavate 3.4 miles of the tunnel.

These machines operate like underground factories, excavating, lining, and grouting the tunnel with pre-cast concrete segments. They advance at an average speed of 16 meters per day, with teams working around the clock to support their operations.

Sustainable Construction and Future Plans

The excavation process is not just about digging; it’s also about sustainability. Nearly 2 million tonnes of earth have been excavated and put to beneficial reuse. Around West Ruislip, the material is used to remodel a nearby golf course and create new green spaces in Hillingdon. London Clay from the Victoria Road site is transported to various locations across the UK, where it supports housing developments and wildlife areas.

As the TBMs progress, other vital features of the tunnel, such as cross passages, vent shafts, and headhouses, are being put in place. These structures will provide ventilation and emergency access once the tunnel is operational. The Northolt Tunnel project, managed by the joint venture of Skanska, Costain, and STRABAG (SCS), is moving into the fit-out stage in preparation for track and rail system installation.

This milestone is a testament to the significant progress made by HS2’s workforce. The Northolt Tunnel, once completed, will be a crucial component of the HS2 network, improving connections between London and the West Midlands. This high-speed railway will offer faster, more reliable journeys and drive economic growth by freeing up capacity for local trains on the congested West Coast Main Line.

The following video explains and showcases the impressive progress done on the HS2’s Northolt Tunnel.