Shaft construction rethink at Yorkshire polyhalite mine
25 August 2020In a letter to local residents, mining giant Anglo American has confirmed its intention to abandon the use of drill and blast for an intermediate shaft at its deep potash and polyhalite mine near Whitby, North Yorkshire. Instead it will use ‘blind boring’.
Located 32 miles from the main site at Woodsmith – hailed as one of the UK’s biggest mining projects in decades – the shaft at Lockwood Beck was to be the site of a TBM launch/reception cavern. But as TBM excavation will now be undertaken by a machine that is currently mining from Teeside and will be used to drive the second part of the tunnel toward the Woodsmith mine, the Lockwood shaft will function purely for ventilation. This has resulted in a diameter reduction from 9m to 3.2m and the need for a simpler shaft-sinking technique to achieve the 360m required depth.
The 25m drill rig that will be used for the blind boring will necessitate dismantling the 45m-high headframe that was installed for the drill and blast work. In its place a small building will be erected to minimise the impact on the landscape.
Blind boring is a technique often used for drilling ventilation shafts, particularly in mining applications. It uses a rotary drill working downwards from the surface and typically allows shaft completion to be completed before the underground development. It differs from raise boring in that no access is required to the bottom of the shaft for the removal of drill spoil; instead, drilling fluid is used to remove the cuttings.
Work on the shaft will start immediately and is expected to finish in 2021.
An article describing the contents of the Anglo American letter to residents was originally featured in the publication New Civil Engineer.
