IM 2021 September 21 | Page 116

SHAFT SINKING
the ability to accommodate a raisebore pilot and Underpinning much of slash and blind sink method in combination .” this success in safe
The Onaping Depth project for Glencore in working practices was the Sudbury is a good example of this where the increased investment in shaft project , led by Cementation Canada , is training strategies at the currently transitioning from a raisebore pilot and Murray & Roberts Training slash in the top portion of the shaft , to a blind Academy at Bentley Park sink method for the lower half . near Carletonville , South
Cementation Canada is continuing to work Africa . This facility uses and exchange ideas such as this within the the latest technologies wider Murray & Roberts Group to improve and methods – supported industry best practice . by realistic mock-ups of
Here , it has been able to leverage the mining environments – to ensure workers are learnings from Africa-based Murray & Roberts fully prepared for all working conditions , the Cementation , in notching up five million fatalityfree shifts earlier this year as part of a concerted Mike Wells , Managing Director of Murray &
company said . corporate journey towards Zero Harm .
Roberts Cementation , explained : “ Our mining
Lucara Diamond Corp ’ s Karowe Underground Expansion project ( UGP ) in Botswana has recently moved ahead with mobilisation of shaft sinking teams commencing late in June , and pre-sinking activities scheduled in the September quarter .
The Karowe UGP , which is expected to extend the operation ’ s mine life to 2040 , is in a fullyfinanced position , with the latest schedule expected to see underground production hit full production by the end of 2026 .
The 2019 feasibility study for the project envisaged life of mine production of 7.8 Mct , a payback period of 2.8 years and an after-tax NPV ( 5 % discount ) of $ 718 million ; all from $ 514 million in preproduction capital .
COVID-19 delays have pushed the project off the original schedule – both in terms of timeline and cost – but the company is now making headway towards a 2026 start to underground production .
Access to the underground mine will be via two vertical shafts , the production and ventilation shafts . The shafts will be concrete lined with the production shaft acting as the main air intake and the ventilation shaft as the exhaust .
The planned depth of the production shaft is around 767 m , while the final planned depth of the ventilation shaft is 733 m . The 767-m-deep production shaft will be equipped with two 21 t skips for production hoisting and a service cage for man and material movement through the mine . This shaft will also serve as the main fresh air intake to the mine .
The pre-sink construction contract and shaft sinking equipment procurement were awarded to UMS Botswana and UMS South Africa , respectively . METS International Ltd , a subsidiary of UMS , was awarded the shaft engineering contract .
Lucara explained : “ Detailed design and engineering work on the production and ventilation shafts is now 90 % complete , and has resulted in the following changes to the 2019 feasibility study : i ) production shaft diameter has increased from 8 m to 8.5 m , ii ) ventilation shaft permanent headframe , hoists and internal conveyances have been removed , iii ) parallel pre-sinking of both shafts , iv ) ventilation fans and coolers to be located on surface , v ) in-shaft grouting of water strikes changed from grout curtain installation from surface , vi ) planned development of an additional sublevel to assist in drilling of drawbells , and vii ) removal of 670L dewatering galleries .”
UMS is mobilising crews to Karowe to initiate presink works . Pre-sinking of the two shafts will run in parallel and start with mobile cranes and then transition to Scott Derrick cranes with the final depth of pre-sink at around 40 m below surface .
Construction of the Third Shaft at Turquoise Ridge will provide an increase in hoisting capacity to 5,500 t / d
customers today regard the commitment to fatality-free operations as a given – not only for themselves but for their service providers . We are proud to be able to demonstrate our success as part of the broader progress in this field by the whole mining sector .”
Over the years in which the five million fatality-free shifts have been achieved , Murray & Roberts Cementation has conducted a diverse range of projects across sub-Saharan Africa , including large shaft sinking contracts such as the Mufulira Deeps sinking project , in Zambia , which was triple raisebored down to 1,587 m depth .
The learnings go both ways , with other group companies learning from Cementation Canada ’ s use of real-time data acquisition technology for short interval control of the sinking process .
Meanwhile , a pre-sink gantry system developed in South Africa by Murray & Roberts Cementation is also gaining prominence across Australia , through RUC Cementation Mining , and elsewhere .
“ In general , each project is evaluated against group experience for what we consider the optimised approach for the particular scope , ground conditions and client success criteria ,” Kohtakangas said .
This process would have been carried out for the shaft work at Jansen , in Saskatchewan , Canada , where Cementation Canada has recently secured a contract with BHP to carry out the post-liner excavation , steel and equipping of the shafts for the first 4.35 Mt / y phase of the potash project .
Kohtakangas concluded on the subject : “ Shaft sinking has significantly changed over the last 20 years and is much safer today . As shaft sinkers , we continually look at new ways to improve all aspects of sinking , including safety and performance .
“ Each shaft sinking project is different and it requires optimising the best temporary sinking method and design with the permanent shaft design .” IM
112 International Mining | SEPTEMBER 2021