Woodsmith Mine, located near Whitby in North Yorkshire, is a deep potash and polyhalite mine.

The project involves Anglo American constructing the UK’s deepest mine, which will see the company extract large quantities of Polyhalite for global distribution. The mine is the biggest mining project in Britain for decades; its twin shafts will be the deepest commercial mineshafts in Britain. A sensitive project, having attracted many objections along the way, developing the mine to extract the material from 1.5 km below the moors with minimal impact, was always going to require complex ground engineering solutions.

To comply with planning, the mine had to be low impact, which restricted it to having only two 60 m deep chambers, to house the headgear for the production and service shafts and a 37 km long tunnel to take the material directly to port facilities at Wilton in Teeside. Three shafts were required from ground level for production, services and one for launching the 5 m diameter tunnel boring machines (TBM), that will drive the first section of the 37 km material transport system (MTS) tunnel at 360m depth to Teeside.

Geology:

Mudstone and Sandstone; classed as weak to medium-strong.

Scope of works:

• Service shaft headgear chamber to 60 m depth, 35 m dia; 48 no. 2.8 m wide and 1.2 m thick panels
• Production shaft headgear chamber to 60 m depth, 32 m dia; 44 no. 2.8 m wide and 1.2 m thick panels
• Production shaft main shaft to 120 m depth, 8 m dia; 14 no. 2.8 m wide and 1.2 m thick panels

Miscellaneous:

To guarantee the specified vertical tolerance of 200 mm, various survey methods had to be combine, which were documented in a 3D BIM model. In addition, a large quantity of bentonite slurry had to be reconditioned in a complex desanding plant and by use of specially designed polymer-based additives. Notwithstanding the often-extreme weather conditions, such as high winds and heavy snow, which were also challenging. 

The intermittent nature of the geological lamination made the cutting process technically challenging and required the deployment of a number of combinations of cutter wheel configurations to optimise performance.

INFO

Construction Method:            Diaphragm wall

Construction Materials:          Concrete, steel

Main Equipment:                    Three BAUER BC 40 cutters on MC 96 and MC 128 duty-cycle

cranes, and complex desanding plants.

Construction Period:              October 2017 - December 2018