Sirius Minerals’ Vertical Shaft Sinking Machine reaches over 115 m depth at Woodsmith polyhalite mine

To construct the initial 120 m of the 360 m deep MTS shaft at Woodsmith polyhalite mine as efficiently, expediently and safely as possible, the company and its contractors deployed specialised, innovative equipment for the first time ever in the UK.

The application of the Vertical Shaft Sinking Machine (VSM) technology – developed by leading mechanised tunnelling equipment manufacturer Herrenknecht – enabled the sinking of the shafts through near-surface water aquifers, due to the fact that the machine is designed to work underwater with a shaft lining being lowered behind.

Typically, shaft lining would be created from pre-cast concrete segments but, in conjunction with contractors Careys Civil Engineering and Joseph Gallagher Ltd, Sirius utilised a new ‘slip form’ technique to pour the concrete lining. Using this technique, by continuously pouring the shaft walls simultaneously with the VSM’s excavation activity, the team was able to line the shaft more safely, rapidly and cost-effectively. Cutting-edge 3D, 4D and virtual reality (VR) modelling technologies were also used to digitally construct the shaft, forecasting a range of possible outcomes for each aspect of the construction process.

The machine reached a depth of 115.2 m in May 2019, setting a new world record for this type of excavation in the process – the previous record was 84 m – Sirius said this is a “testament to the groundbreaking, innovative approach that we have taken to construct our project.”