Key milestone for HS2 as half of tunnels completed

Construction of the giant network of tunnels for HS2 has now passed the halfway point, marking a significant milestone for Britain’s new high-speed line. HS2, which is at peak construction, supporting more than 31,000 jobs, has now completed excavation of two of its five twin-bore tunnels, with a further two well underway. It underlines the scale of the progress being made on the line which is being constructed at 350 separate worksites between London and the West Midlands.

In total, high-speed trains will travel through 44 km of twin-bore tunnels – or almost a fifth of the 225 km route. This means that HS2’s fleet of tunnel boring machines are excavating and building a total of 88 km of tunnel. New analysis published on 9 May 2024 shows that 46 km - 53% - has been excavated and built so far, eclipsing the length of tunnels bored for the Crossrail line beneath London. Each TBM operates like an underground factory, excavating the tunnels, lining them with pre-cast concrete tunnel segments, grouting them into place and moving forward at an average speed of between 12 and 16 m per day.

Once the drives are finished, HS2 moves to the next stage of the tunnelling project when other vital features such as the cross-passages, vent shafts and portals will be completed. This comes before the internal fit-out of railway systems including power, track and signalling which allows high-speed trains to operate.

Completed tunnels:

In March 2023, TBM ‘Dorothy’ completed its second drive of the one-mile Long Itchington Wood Tunnel in Warwickshire – the first tunnel to be completed on the project.
Earlier this year, ‘Florence’ and ‘Cecilia’ completed both drives of the 16 km Chiltern Tunnel – the longest tunnel on the route – with the second breakthrough witnessed in March.

On-track tunnels:

In London, four TBMs are digging the 13.5 km Northolt Tunnel. ‘Sushila’ and ‘Caroline’ have excavated around three miles of their five-mile route, travelling from West Ruislip on the outskirts of the capital to Green Park Way in Greenford, north-west London. Two more are building a 5.5 km section of this tunnel in the opposite direction from Victoria Road in Ealing to Green Park Way. ‘Emily’ has completed 0.2 miles and ‘Anne’ has just set off.

In the Midlands, ‘Mary Ann’ is 2 km into the 5.6 km drive of the first bore of the Bromford Tunnel between Water Orton in North Warwickshire and Washwood Heath in Birmingham. ‘Elizabeth’ has just started to build the second bore.

Tunnel yet to start:

Significant preparatory works have already been completed ahead of the formal start of the 7.2 km Euston Tunnel between Old Oak Common and Euston stations in London. The two TBMs are currently being manufactured and tested. The government is now exploring different funding mechanisms for delivery of the tunnel.

The figures came as separate quarterly analysis was published showing that a record number of jobs are now supported by HS2. Figures show 31,160 are now employed directly or through the supply chain in the first three months of 2024, an increase of 2,674 full-time equivalent roles over the previous quarter. Some 1,533 new apprenticeships have been created and 4,258 formerly unemployed people have now found work on HS2 since 2017.