National Highways has placed an order for Europe’s largest tunnel boring machine (TBM) for the £10bn Lower Thames Crossing, with tunnelling work remaining on schedule to begin in 2028.
German manufacturer Herrenknecht will design and build the 16.4m diameter machine, which will be the third largest tunnel boring machine ever constructed worldwide. The TBM will be purchased and operated by the Bouygues Travaux Publics Murphy joint venture, which is responsible for delivering the project’s twin-bore tunnel beneath the River Thames.
Measuring 120m in length and weighing more than 5,000 tonnes, the machine will be manufactured in sections before being transported to the Port of Tilbury for assembly at the construction site.
The variable density TBM will excavate both of the project’s 2.6-mile tunnel bores. After completing the first drive, the machine will be turned around and reused to excavate the second tunnel, reducing both project costs and carbon emissions.
Once complete, the twin three-lane tunnels will form the UK’s longest road tunnel, extending to more than twice the length of the existing Dartford Crossing tunnels. The bores will pass through chalk and clay strata at depths of up to 60m beneath the River Thames.
National Highways said construction remains on programme following the start of the main works earlier this year, with the new crossing expected to open during the early to mid-2030s.
The electrically powered TBM will operate using renewable energy, while low-carbon concrete tunnel linings will be used throughout the project, supporting the Lower Thames Crossing’s ambition to become the UK’s first carbon-neutral major infrastructure project during construction.
Herrenknecht has previously supplied tunnel boring machines for major UK infrastructure schemes including the Elizabeth line, HS2, Thames Tideway and the Silvertown Tunnel. The Lower Thames Crossing machine will also be the largest variable density TBM the company has ever built, incorporating the biggest accessible cutting wheel in Herrenknecht’s history.
