Installation of three up to 120m deep diaphragm wall shafts with diameters between 8m and 35m at Woodsmith Mine in North Yorkshire (England)-Paper

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The Woodsmith Mine project near Whitby, North Yorkshire, is being developed by Anglo American to extract polyhalite, a multinutrient mineral used as fertilizer. The mine is planned to reach 1,500 m underground, with mined material transported through a 36 km tunnel to Teesside for processing and export. The design minimizes permanent effects on the North York Moors National Park.<br /><br />Between October 2017 and December 2018, BAUER constructed three diaphragm-wall shafts up to 120 m deep. These included deep main shafts and two 60 m-deep headgear chambers, with diameters reaching 35 m. The walls stabilized weathered, water-bearing rock so that subsequent excavation could proceed safely. Below 120 m, the stable, dry rock allows conventional shaft-mining methods.<br /><br />Construction involved highly variable sandstone and mudstone, groundwater pressure, and fissures that could cause slurry losses. Three BC 40 cutter systems excavated the panels, supported by a large bentonite-slurry circulation and de-sanding operation. Fine particles were removed using desilters and centrifuges. A specially developed, fast-swelling polymer sealed larger rock fissures, reducing slurry losses from about 250 m³ to 30 m³ per panel.<br /><br />A key requirement was limiting vertical deviation to 200 mm over 120 m. Inclinometers, regular cutter-inclination surveys, and ultrasonic measurements tracked panel position and dimensions. Their results were combined into a 3D as-built model to verify compliance. Other tailored measures included glass-fiber-reinforced plastic spacers, which helped position reinforcement cages without obstructing later panel cutting.<br /><br />The completed diaphragm walls enabled the mine operator to begin subsequent works. The project demonstrates how specialized equipment, materials, monitoring, and construction planning can address demanding deep-shaft conditions while meeting strict dimensional requirements.

Keywords

Woodsmith Mine

North Yorkshire

polyhalite

Anglo American

diaphragm-wall shafts

deep shaft mining

bentonite slurry

cutter systems

groundwater pressure

North York Moors National Park