SHAFT SINKING four packages of work : ( i ) design , engineering and procurement services for the new shaft ; ( ii ) shaft pre-sink construction and change over ; ( iii ) main sink construction ; and ( iv ) shaft equipping and commissioning .
In its June quarter results , Ero Copper said main shaft sinking at the Pilar Mine ’ s new external shaft was progressing on schedule , with a projected depth of approximately 600 m expected to be reached by year-end .
Murray Macnab , Group Executive Technical Director for UMS , says on top of these existing projects , the company is also pursuing work in South America , Africa and Europe .
“ In South America , there are prospects coming up in Chile and Peru ,” he said . “ In fact , we have opened a business unit in Chile on the back of these strong prospects . We have also acquired some assets – hoists and the like – to ensure that when the work comes our way , we are ready to go .”
Turnkey mechanised rock excavation aims
Master Drilling has long been associated with raiseboring , with the company having achieved a number of records in this space – including the successful completion of a 1,382-m-long pilot hole at the Zondereinde Number 3 Shaft , in South Africa .
The company continues to maximise its raiseboring potential in the shaft space , having built out a number of RD7 and RD8 rigs – part of its high capacity raiseboring equipment offering for bigger diameter and deeper shafts – to be put to work at projects .
It has also been furthering mechanised blind sinking efforts in projects where there is no shaft bottom access with its Shaft Boring System ( SBS ).
The SBS was developed as a 45-m long , 450-t machine to progress through rocks with a UCS of 200-400 MPa , carrying out cutting , mucking and shaft reinforcement concurrently .
The front end of the machine ( as it descends the shaft ) is made up of a pilot cutting head – in a W-shape configuration – and gearbox . The pilot cutter head accounts for some 15 % of the entire rock cutting volume , with the wider diameter reamer section that follows accounting for the remaining 85 %. This first section can independently progress by 1.5 m when cutting is taking place in three separate strokes .
The rest of the 45-m long machine catches up following this initial cutting , which is automated by a series of lasers that ensure the machine is
on the correct course and using optimal force . This cutting station is followed by two shaft gripping stations for machine support within the shaft . Following this is an enlargement station – also equipped with cutters – that widens the pilot hole carried out by the pilot cutter head to the desired diameter , with Master Drilling saying this will range from 7.5 – 11.5 m .
Behind this is a main stage made up of eight separate levels for concurrent services such as rock bolting , lining and other reinforcement measures . A series of kibbles lowered by winders and transported on a conveyance on one of the levels of this stage bring the required shotcrete and materials to allow these concurrent tasks to take place .
The headgear to support these operations from surface will likely be around 35 m tall , while the total power requirement comes in at around 10 MW .
The company ’ s SBS development approach , which started in 2019 , led to the definition of high-risk features in the concept of the machine , which included the ability to remove rock chippings from underneath the cutter heads .
“ We invested in a significant amount of intellectual property and development where the one configuration included the W-shaped cutterhead as well as a gearbox ,” Master Drilling told IM . “ We experimented with the cutterhead and gearbox in 10 m of 320 Mpa UCS rock to set our key KPIs . After the successful completion of the test work in 2019 , with the challenges and setbacks from the COVID-19 pandemic , we decided to take the concept forward and build a smaller diameter configuration to control cash costs and finally implement non-critical infrastructure such as ventilation shafts .”
This has since led to the development of a 4.3- m diameter rig that has been successfully launched at a test site in Fochville , South Africa , owned by Master Drilling .
“ We want to ensure that the SBS ’ s technology maturity is developed through an independent experimental site before allowing the SBS to be commercially available ,” the company said . “ Through the learnings from the experimental
A 4.3-m diameter version of Master Drilling ’ s Shaft Boring System was recently successfully launched at a test site in Fochville , South Africa
site , we are able to develop the SBS further .”
Master Drilling expects to sink between 50-100 m at the site with this new rig , testing all features and configurations that the machine would usually be operating on a 1,000-m-deep shaft , and starting the SBS with its starter frame and headgear to prove a pre-sink is not needed while using the machine .
For larger diameter shafts – 7-11.5 m – Master Drilling expects to use a smaller head to create a pilot hole for sinking and then simultaneously ream the shaft to a bigger diameter – lowering the complexity of the machine and facilitating the collection of cuttings in the kibble with gravity .
“ Safety is paramount for the SBS , with less people being involved inside of the shaft ,” Master Drilling said .
The ability to mobilise all resources to the site – and carry out permanent site construction concurrently with sinking – reduces the financial cash flow impact , as well as reduces the time to reach the orebody .
The company added : “ The current SBS being trialled is not the only machine that will be commercially available after modifications . More machines of varying sizes will be developed and manufactured in the future .”
For instance , the company is already working towards a scope of more than 3,000 m sinking depth for the SBS . Master Drilling is also busy with the development of the Mobile Tunnel Borer – an adaptation of a traditional TBM – and the Reef Borer – a system able to significantly reduce the amount of waste in gold reef operations .
The company concluded : “ We are open to working with other contractors and OEMs to create joint ventures in developing new technologies .”
IM
SEPTEMBER 2024 | International Mining 111