SHAFT SINKING
Woodsmith SBRs re-start cutting process
One of the most-watched shaft sinking projects in the sector right now is located in the UK , with the Woodsmith project in north Yorkshire having been on the radar for a number of reasons . First off , it is a project that has changed hands recently . Originally guided by Sirius Minerals , the 10 Mt / y project was acquired by Anglo American in 2020 , a transaction that came with a fresh look at the whole project execution phase .
The change in ownership and re-assessment of plans drawn up by Sirius – a much smaller company guided by different investor pressures and operating procedures – led to Anglo American relieving the lead shaft sinking contractor of its duties .
Another reason for watching the project is the planned use of SBR technology from Herrenknecht .
After debuting at the Jansen potash project in Saskatchewan , Canada , where it excavated two 8-11 m diameter blind shafts down to circa-1,000- m-depth , SBR 2.0 – the second generation of the technology – was put to the test in Belarus at the Slavkaliy-owned Nezhinsky potash project . It ended up breaking shaft sinking records under the guidance of contractor Redpath Deilmann on a project to sink two 8-m diameter shafts ( one to 750-m depth and one to 697-m depth ).
Herrenknecht , with its experience in mechanised tunnelling , developed the SBR for the mechanised sinking of blind shafts in soft-to-medium rock . Based on the proven technology of the Herrenknecht Vertical Shaft Sinking Machine , the SBR offers improved safety performance compared with conventional shaft sinking methods while also achieving higher advance rates , according to the company .
The SBR is a 60-m tall , suspended shaft sinking machine , with 12 work decks and two service platforms . A telescopic , boom-mounted cutting head is used to precisely excavate rock via a partial-face cutting method . The cutting head works in a cycle , starting each cut from shaft centre to shaft wall , repeating until a layer of material is removed . Excavation proceeds in 1-m increments , followed by SBR lowering sequences .
The SBR was chosen for Woodsmith by Sirius over the conventional drill and blasting method due to its advantages in improving safety and schedule . This methodology , Sirius said , would allow the company to satisfy several operational objectives , moving away from the use of explosives and providing a safer , more predictable work method .
Instead of a linear process , the SBR allows work to be completed concurrently as the shaft is sunk , as well as minimising damage to exposed host rock , and further improving safety while minimising downtime . Work decks above the cutting head allow workers to install shaft lining and tubbing as excavation continues , while a pneumatic mucking system removes waste rock .
The third generation of technology – which builds on the first two deployments with , among other things , the addition of two retractable robotic probes to test and grout the ground ahead for safer excavation and an additional control cabin on surface for more remote operation – is due to sink production and service shafts at Woodsmith . The Sirius plan had these shafts pegged as being 6.75 m in diameter and going down to depths of 1,594 m ( production ) and 1,565 m ( service ).
The SBRs are being supported by four triple sheaved winches from SMS SIEMAG and conveyors from Herrenknecht-owned H + E Logistik GmbH , among other support equipment .
Work on the service shaft commenced in 2021 with former Anglo
Redpath Deilmann and Anglo American have now re-started cutting operations using Herrenknecht ’ s SBR at Woodsmith
American Chief Executive , Mark Cutifani , confirming in July of that year that the “ first cut ” with the SBR had taken place in the shaft .
This progress was made while the company was still completing a detailed technical review on Woodsmith to ensure the technical and commercial integrity of the full scope of its design . This review has a particular focus on the sinking of the two main shafts , the development of the underground mining area , and the changes required to accommodate both increased production capacity and the more efficient and scalable mining method of using only continuous miners , Anglo American said .
Since the first cut was made in July 2021 , however , Anglo American and Redpath Deilmann – which is now leading the sinking project as shaft sinking contractor – have been reviewing the existing plans for sinking with the SBRs , carrying out minor hardware changes on the machines and ensuring all staff have the appropriate training to facilitate the completion of the shaft sinking process . Redpath is also involved in the drill-andblast-based sinking for the materials transport system ( MTS ) shaft , which , under the Sirius plan , was due to reach a depth of around 350 m .
Various shaft sinking rates have been mooted in the past at Woodsmith , and Anglo American says it is currently working to develop the optimal solution for the facility based on technical standards .
The sinking at Woodsmith represents a different challenge to the two previous SBR projects conducted to this point .
For starters , there is no ground freezing expected to take place at Woodsmith – unlike what happened in Canada and Belarus . This process , while time consuming and only used to freeze unstable water-bearing strata around the shaft , can create more rock uniformity to aide consistent cutting rates .
There is also the MTS level to consider at Woodsmith , with plans to carry out lateral development work around the 360-m-level to join up the production shaft and the MTS level , where polyhalite ore will be transported along a 37-km tunnel to Wilton near the port . This means vertical cutting and loading may be halted while the MTS level connection is established .
All these factors , along with the performance of previous SBR work , will be incorporated into the engineering work Anglo American is carrying out at Woodsmith , but , in terms of the SBR , cutting at the service shaft has now recommenced , with plans to start sinking in the production shaft by the end of the year .
conventional configuration like that of Alamos ’ Young-Davidson . Once skipped to surface , ore will be trucked to the expanded mill circuit . The total construction capital for the shaft installation including all supporting infrastructure is expected to be C $ 229 million ($ 177 million ).
John Fitzgerald , VP , Projects , at Alamos , told
IM : “ Shaft sinking and concurrent concrete lining is scheduled to take 18 months , which includes development of three shaft stations and a loading pocket . The steady-state sinking rate ,
88 International Mining | SEPTEMBER 2022