Project Description

FP McCann Precast Concrete Segmental Shaft Installed on North Yorkshire Potash Mine Project

StatusIn Progress

Location: Chapel Riverside, Southampton

Division: Tunnels & Shafts

Main Contractor: Anglo American (Crop Nutrients)

Market Sector: Housing, Water

FP McCann’s precast concrete shaft segments are playing a major role in the record breaking construction of a brand new potash mine. The Woodsmith Mine near Whitby, North Yorkshire, is being developed by Anglo American (Crop Nutrients) and is set to be the world’s biggest and highest-grade polyhalite project with annual production targets of 30 million tonnes by 2030. When the mine is up and running, it will be the deepest in Europe and have the longest tunnel in the UK.

Polyhalite is a high grade naturally occurring mineral used as a fertiliser worldwide. The mined material will be transported along a 37km tunnel via a Material Transport System (MTS) to the material handling facility at Teesside. From here, it will be shipped to countries across the globe.Key to the project is the sinking of two 1,600m shafts. The twin shafts, the deepest ever constructed in the UK, once complete, will carry equipment and people to (service shaft) and transport material up from the mine (production shaft).Prior to deep shaft boring work commencing on the service shaft, tunnelling and shaft building specialist Joseph Gallagher was tasked by Anglo to construct an FP McCann 8.2m internal diameter precast concrete segmental access shaft. Comprising of 40 standard front bolted smoothbore precast concrete segmental rings and with solid ground conditions in place, it was installed by the underpinning method of construction. Boring of the main service shaft will shortly commence utilising a Herrenknecht Shaft Boring Roadheader machine (SBR).The SBR will be launched into the smoothbore lined precast concrete shaft and descend 1,600 metres to the mine. A number of shaft building and tunnelling techniques are being utilised on the project and Joseph Gallagher is currently engaged to deliver the MTS using the drill and blast technique.Commenting on the precast concrete shaft lining build Mark McGeady Contracts Director for Joseph Gallagher said, “The use of this method to build the reception shaft for launching the SBR is an extremely efficient and structurally sound process. Construction is simple and allows for ease of ground excavation. The smaller footprint over other options helps to reduce the volume of material to be removed thereby minimising the environmental impact. From the installation of the first ring, the shaft build continued uninterrupted”.

FP McCann’s smoothbore tunnel and shaft segments are all factory fitted with EPDM rubber gaskets which provide an immediate water-tight seal upon construction. Cross segment connections are made by passing a spear bolt through a pocket in one segment and screwing it into a threaded plastic socket in the adjacent segment. Circle joint connections are made using a ‘T’ bolt passing through a hole in one segment into a ‘T’ box in the adjacent segment. Bolts are designed to fully compress the gasket.