The tunnel boring machine starting at the mine site requires a shaft to be constructed, down which the TBM components will be lowered and assembled in a cavern at the bottom. An access shaft is also required at Lockwood Beck to facilitate refurbishment of the Wilton TBM, before it continues south.
The majority of the mineral transport system shaft sinking operations will be undertaken by traditional drill and blast methods, using a multi-decked working platform (called a Galloway) suspended on winches from the surface. However, first the upper sections of the shafts must be sunk through near surface aquifers and sealed.
At Lockwood Beck, this is achieved by injecting grout into the ground around the shaft to create a grout curtain, then digging out and lining the shaft with concrete. When at around 50m depth, the Galloway can be launched.
At Woodsmith Mine, because of a deeper aquifer, a specialist Vertical Shaft Sinking Machine was chosen. The machine is designed to work underwater with a shaft lining being lowered behind.
The machine reached a depth of 115.2m in May 2019, setting a new world record for this type of excavation in the process - the previous record was 84m - testament to the groundbreaking, innovative approach that we have taken to construct our Project.
Once the shafts have reached the required depth, the shaft is excavated to -360m with the Galloway in the following process:
The first Galloway was lowered into the MTS shaft at Woodsmith Mine in July 2019: