Tunnels
UK Contractor Sets Tunnel Bore Record With 16-Mile Single Drive
A Herrenknecht TBM has been driving south from the River Tees in England since June 2019 for a tunnel connecting the Woodsmith mine to a processing plant.
Image courtesy of Anglo American
U.K. construction teams in England have recently broken two tunneling records—achieving one of the world's most sustained single tunnel-boring machine drives on a project in the north, says its contractor, and securing a design-build contract for the country's longest road tunnel in the south.
To break the single drive record, a 20-ft-dia Herrenknecht TBM has been burrowing southward from the River Tees since June 2019, most recently under the North York Moors.
It has completed about 70% of the full 23 miles to the new Woodsmith mine being developed by London-based mining firm Anglo American plc near Whitby, says a spokeswoman for tunnel contractor Strabag UK. By October, the machine had advanced 25.8 km (about 16 miles), which Strabag believes to be a world record, beating an undisclosed Middle East project.
The previously reported longest drive—of 25.4 km (15.8 miles)—took place in China 12 years ago at the Pinglu tunnel on the Yellow River water diversion project, a record claimed by The Robbins Co., Solon, Ohio, for its 15.7-ft-dia doubled shield TBM.
Due for completion in summer 2026, the Woodsmith tunnel is located nearly 1,000 ft below ground and will carry ore fed from a 5,200-ft-deep, 16-ft-dia production shaft. It now is being sunk by Germany-based Redpath Deilmann GmbH into an 82-ft-thick polyhalite seam.
Deilmann has completed about one-quarter of the production shaft and nearly 2,300 ft of a similarly deep service shaft nearby, says an Anglo American spokesperson. The contractor is excavating each shaft with a vertical roadheader at the bottom of a 216.5-ft-tall assembly, supplied by Herrenknecht.
Anglo America is not disclosing contract values, but Tom McCulley, head of the company's crop nutrients division, recently approximated the excavation cost at $1 billion each for the tunnel and for shafts.
Looking for quick answers on construction and engineering topics?
Try Ask ENR, our new smart AI search tool.
Ask ENR →
The tunnel will convey polyhalite ore from the mine to a plant on the south bank of the Tees for processing into fertilizer pellets.
Contract Awarded
Meanwhile, the government's National Highways company recently awarded the tunnel contract for the Lower Thames Crossing, 19 miles east of London. Extending for 2.7 miles and with diameters around 53 ft, the twin three-lane tunnels are the country's longest and widest, according to the owner.
A joint venture of Paris-based Bouygues Travaux Publics SAS with J Murphy & Sons Ltd secured the $1.7-billion design-build contract for the river crossing. Mott McDonald Group and Arup Group are the team's design firms.
The recent award completed the crossing’s main procurement, since National Highways had already named two preferred bidders for around 12 miles of approach roads together valued at over $2 billion.
The planned Lower Thames Crossing would be the U.K.'s longest road tunnel. Rendering courtesy of National Highways
Contracts are contingent on the crossing obtaining approval by the national Planning Inspectorate, which will complete its examination before this year's end.
With the tunnel contract awarded, “We will be working to further develop our design and engineering plans in line with [permitting requirements]," says a National Highways spokesperson. "The decision on whether we will use one or two TBMs will be guided by a range of factors including carbon [emissions], community and environmental impacts, construction schedule and cost."
Procedurally, the project could get the go-ahead by next summer, but the U.K. government this March delayed the start of work by two years.
Having already spent more than $1 billion developing the project, "it is important we get this right," said Secretary of State for Transport Mark Harper. The delay "will be an important opportunity to consult further to ensure there is an effective and deliverable plan."
