On Friday 8 October 2020, the contract for the first two giant tunnelling machines for London’s HS2 tunnels was signed by HS2’s Main Works Civils Contractor, Skanska Costain STRABAG JV (SCS JV), marking significant process in the southern stretch of HS2.

The tunnel boring machines (TBMs) are being built by Herrenknecht and are to be delivered to the site by the end of 2021. They are being designed and manufactured specifically for the London clay and chalk ground conditions they will bore through.

The tunnels for HS2 are twin bored and will be 13 miles each way, making a combined total of 26 miles, meaning the HS2 London tunnels will be the same length as Crossrail. The programme of tunnelling between Central London and the M25 will be undertaken by SCS JV, and overall, there will be 10 TBMs purchased to construct the 64 miles of tunnelling along the HS2 route between the West Midlands and London.

The new London tunnels will begin just outside Euston station and will emerge at Old Oak Common station in West London. The route will then continue underground from Old Oak Common to the outskirts of West London.

Malcolm Codling, Client Director at HS2 Ltd, said: “HS2’s London tunnels will help ensure many homes and habitats in the capital remain undisturbed. This is a key part of our commitment to deliver Britain’s new high-speed railway in the most environmentally friendly way and minimising disruption to our neighbours.

“Building HS2 will showcase Britain’s world class capabilities in tunnelling. The procurement of these incredible machines is an exciting step towards the construction of the London tunnels, which will involve them working 24 hours a day, seven days a week.”

Once the new TBMs have been built they will be transported by sea before being delivered to site at the end of 2021. Once they have been assembled, they will begin the tunnel drive from mid-2022, until completion at the beginning of 2024.

James Richardson, Managing Director of Skanska Costain STRABAG joint venture (SCS JV), said: “As the construction partner responsible for the majority of tunnels on the HS2 project, our contract for the first two TBMs is a major milestone for us. This partnership with Herrenknecht has brought together leading expertise in both our organisations and together we are constructing some of the most advanced TBMs in the world to efficiently drive the tunnels under London.

“Work is already well underway to prepare for the first tunnel launch in 2022. Throughout these and all our activities we are committed to involving local communities and stakeholders and supporting social development and employment through the 4,500 jobs that will be created.”

David Salameh, Head of Project Management Traffic Tunneling at Herrenknecht, said: “We feel honoured to be part of the epoch-making HS2 project and especially to work with the SCS Joint Venture. Our two Herrenknecht machines will be specially and innovatively designed for this project, excavating the Northolt Tunnels West.”

Some key facts about these giant machines:

• They will run for 22 months non-stop except for Christmas Day and bank holidays
• Each machine will be 140 metres in length, one and a quarter times the length of a football pitch
• The cutter head will be 9.84m in diameter, slightly smaller than the machines boring through the Chilterns
• They each weigh approximately 2,050 tonnes, roughly the weight of 20 blue whales
• 1.2 million cubic metres of excavated material will be removed, weighing 2.46 million tonnes

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