World record for longest single TBM drive broken on North York Moors mine project

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Working on behalf of Anglo American, Strabag is constructing the tunnel for a planned polyhalite mine underneath the North York Moors National Park, near Whitby.

When completed, the tunnel will run for 37km and will be the world’s longest conveyor tunnel for a permanent mineral transport system. It will transport 13Mt of polyhalite annually out of the mine.

Polyhalite is a naturally occurring mineral which will then be crushed and granulated to create POLY4, a unique multi-nutrient fertiliser which is suitable for organic use. It will be used in worldwide fertiliser programmes to help boost crop yields, plant strength and improve soil structure.

Strabag started boring the tunnel, which has an internal diameter of nearly 5m, in June 2019 using a Herrenknecht TBM. The former record for the longest single TBM drive was held by a water conveyance tunnel project in the Middle East which was also built using a Herrenknecht tunnel boring machine.

The project is significant for a number of other reasons too.

With the rollback of mining in the UK over the past few decades, Anglo American tunnel area manager Mark Pooleman believes this is the first time deep shafts have been sunk on UK soil “in a generation”. The two shafts which will be used to extract the polyhalite will be sunk roughly 1.6km deep.

Speaking at NCE’s Tunnelling Conference 2023 on 7 December, Pooleman said: “In terms of numbers, the service shaft, which is the more advanced of the two deep shafts, that’s about 700m deep right now.

“The second deep shaft is [currently] about 400m and these are the first deep shafts to be sunk in the UK in a generation quite frankly. We do have the mine up the road in Boulby that has deep shafts but they were built in the 60s.

“This a real significant project for the UK mining community.”

When completed, the shafts will take the crown as the deepest mining shafts ever built in the UK.

In order to build the shafts, Anglo American and Strabag are using an innovative machine that has only been used in the world twice before. Called a shaft boring roadheader, the machine, also developed by Herrenknecht is designed for the mechanised sinking of blind shafts in soft to medium-hard rock. The shaft boring roadheader is equipped with a roadheader boom and a rotating cutting drum.

Anglo American is constructing the tunnel for the conveyor belt system so the transportation of the polyhalite doesn’t have to be done by trucks travelling through the national park.

Strabag managing director Simon Wild said: “We are extremely proud of the team at the Woodsmith project for reaching this incredible milestone and safely passing the current world record set for a single bored tunnel drive.

“This is another example of our growing presence in the north- east of England and the UK, demonstrating our industry leading expertise.”

Woodsmith project director Andrew Johnson said: “We are delighted to achieve such an incredible milestone in the UK as part of our pioneering project.

“It is a demonstration of the fruits of teamwork with our partners. We are now focused on looking forward and setting a new world record every day. The Woodsmith tunnel is a fundamental part of our commitment to create a sustainable mine with minimal environmental impact.”

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