HS2 passes halfway in excavation of 88km of bored tunnels for high-speed line

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In total, high-speed trains will travel through 44km of twin-bore tunnels, nearly 20% of the full 225km route.

HS2’s fleet of tunnel boring machines (TBMs) is currently excavating and building a total of 88km of tunnels and new analysis has revealed that 47km (53%) has now been completed. This is longer than the total length of tunnels bored for the Crossrail line beneath London.

Tunnelling progress

In March 2023, TBM Dorothy completed its second drive of the 1.6km Long Itchington Wood Tunnel in Warwickshire, the first tunnel to be completed on the project. The TBM – named after Nobel Prize winning chemist Dorothy Hodgkin – was launched in November 2022 by main works contractor BBV (Balfour Beatty Vinci).

Earlier this year, TBMs Florence and Cecilia completed both drives of the 16km Chiltern Tunnel, the longest tunnel on the route, with the second breakthrough witnessed in March. Align JV – comprising Bouygues Travaux Publics, Sir Robert McAlpine and VolkerFitzpatrick – has the contract to build this tunnel. NCE heard that difficulties getting Florence through the final stretch influenced the final approach for Cecilia.

In London, four TBMs are currently digging the 13.5km Northolt Tunnel. Sushila and Caroline have excavated around 4.8km of their 8km route, travelling from West Ruislip to Green Park Way in Greenford, north-west London. Two more TBMs are building a 5.5km section of this tunnel in the opposite direction from Victoria Road in Ealing to Green Park Way. Emily has completed under 1km and Anne has just set off. The Skanska Costain Strabag Joint Venture (SCS JV) is responsible for the construction of the tunnels in London from Euston to West Ruislip.

Significant preparatory works have already been completed ahead of the formal start of the 7.2km 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. Earlier this week, it was announced the government is expected to confirm over £1bn of public funding to construct the tunnels between Old Oak Common and Euston.

The completion of an 853m logistics tunnel at the HS2 Old Oak Common station construction site sent a “big message” to government to give the go ahead for tunnelling to Euston, according to HS2 project managers.

SCS tunnels for HS2 Phase One

In the Midlands, TBM Mary Ann is 2km into the 5.6km 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.

Cut and cover tunnels

The rest of the HS2 route includes six cut and cover “green” tunnels totalling over 8km, and 70 cuttings totalling 70km, which means over half of the track 122km is below ground level in tunnels or cuttings, reducing visibility of the railway.

Construction of the first pre-cast tunnel at Chipping Warden commenced in June 2022. Assembly of the 2.5km long tunnel was paused in August of that year due to “quality issues” but then resumed the following month.

The longest cut and cover tunnel on the route is the 2.7km Greatworth tunnel, where work started in September 2023.

HS2 Jobs

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.

TBMs are operated by crews of around 17, working in shifts to keep the 24/7 operation running. They are supported by teams on the surface managing logistics and maintaining the smooth progress of the tunnelling operation. In addition, many more people are involved in producing the concrete tunnel wall segments, along with dedicated teams processing the material from the tunnels so it can be re-used elsewhere on the project.

Last year, NCE spoke to the contractors involved with tunnelling for the massive HS2 project.

Rail minister Huw Merriman said: “Reaching this impressive milestone on a project of HS2’s scale shows just how much momentum is behind construction of the line, which, once complete, will have a transformative impact on rail travel for generations to come.

“It’s a significant achievement for the team helping deliver this railway and I’m delighted the project has now supported record numbers of new jobs, demonstrating the vital role it is playing in creating opportunities up and down the country.”

HS2 civils delivery director Jackie Roe said: “The halfway point for our tunnelling programme is a fantastic milestone, but we’ve still got a lot of work to do on the tunnels, including all cross passages, vent shafts and then fitting them out with the critical rail and power systems that will eventually allow trains to safely operate.

“This is a significant step towards delivering the country’s new high speed railway, which will provide faster and far more reliable journeys, while almost doubling capacity on the most congested part of the West Coast Main Line.”

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