JSE-listed raiseboring and drillingservices provider Master Drillingfeatured its horizontal raiseboring (HRB) technology and its advantagesfor mechanised mining at the latestSouth African National Committee on Tunnelling (SANCOT) breakfast, heldin Woodmead last month.
Master Drilling mechanical engineer Willem Roothman, who presented the technology for mining and civilengineering applications, highlightedthat there was a “big appetite” in theindustry for mechanised mining, which formed the backdrop for the HRB technology.
Advertisement“Master Drilling took conventional raiseboring and basically turned it tothe side to create a method for excavatingtunnels for underground miningapplications and possibly also in civil applications.”
Pilot Project
Among the key topics was the trial Master Drilling did at diamond mining group Petra Diamonds’ Cullinan mine, in Gauteng, with Roothman underscoringthe applications, advantages anddisadvantages of the HRB technology. Master Drilling was involved in theboring and excavation of a 180-m-long horizontal tunnel with a 4.5-m diameter through the diamond deposits.
Roothman explained that theconstruction method entails firstdrilling a smaller pilot hole through the kimberlite, which was challenging as no water could be used for flushing. The pilot hole also needed to be near perfectly straight. Subsequently, Master Drillingpioneered the use of vacuum air suction and laser-assisted directional steering, which aided the company to achievean accuracy of holing within 20 mm ofthe required target.
Any raiseboring exercise requiresaccess from both sides; for the Cullinan pilot project, Master Drilling decidedto place the HRB machine on thenorth-end side of the mine and startreaming from the south-end side of the mine. “There was adequate ventilationand services, with enhanced storagecapacity for all of the large components that we used . . .”
Although the same rig is usually usedto do the piloting and the reaming innormal raiseboring, Master Drilling useda different rig than the actual raiseboring rig for the pilot drilling.
“Due to ground formationcomplications, we couldn’t use the same machine, so we opted to use a different machine that is normally used in thecivil industry. The reason for this is that the kimberlite deteriorates drastically when in contact with water, thus normal pilot drilling equipment that uses waterto flush the cut material from the holecould not be used. We therefore had touse the vacuum drilling system forsafe and dry drilling purposes,” he explained.
“After we finished the pilot drilling,the pilot drilling machine was movedand the raiseboring machine wasinstalled onto the same frame, whichwas designed to allow for the reaming machine to be mounted in the sameposition to keep the centre of the hole in-line with the centre of the machine, saving time with alignment and machine setup.”
In terms of removing cut material, Master Drilling had to find a solutionto move the material from the facewhere it is cut to the back of the reamer. “We modified one of our standardreamers, adding scrapers, collectionbuckets and a muck-handling attachment.Initially, we used a vacuum system,” Roothman said.
However, because water was not usedfor dust suppression, the filters of thevacuum system clogged up, after which Master Drilling then used a load-haul-dump machine to collect the muck more efficiently.
Technology Features
There were zero injuries during thetrial, which is something that minesare “very interested in and it’s one of the advantages of mechanised mining, compared with conventional methods”, Roothman said.
The HRB technology has many other benefits, including improved safety and advance rates, as well as improvedstructural integrity of the tunnel itself. Master Drilling CEO Danie Pretorius said the technology holds great potentialto increase mining productivity, owing to its continuous process of rock boring.
The advance rate of the HRBtechnology had almost doubled,compared with conventional methods.The costs are also in line with the costsof conventional methods. Further, thetechnology can be used in otherdisciplines, such as civil engineeringand energy.
However, the advance rate dependson the type of geology. “One of thebiggest drawbacks is that you need to have access on both sides and you can only drill straight tunnels – you have to have a straight line of sight,” Roothman acknowledged.
Following the trial at the diamondmine, Master Drilling completed several proposals and submitted bids for tendersto various mining companies.
SANCOT Breakfast Talks
The Master Drilling breakfast talk took place on February 15 at South African multidisciplinary engineering firm GIBB’s offices in Woodmead, Johannesburg. The breakfast was also sponsored by GIBB.
SANCOT has been hosting breakfast talks every two months since last year. Three talks have been hosted to date, allat the GIBB offices.
The first talk, Tunnelling Trends in South Africa, considered the history oftunnelling in the country and waspresented by SANCOT chairperson and GIBB senior associate Ron Tluczek.
The second talk, presented by GIBB associate Monique Wainstein, highlighted the potential of using microtunnel boringmachines to augment the water supply for Mthatha from the Mthatha dam, in the Eastern Cape.
“The SANCOT Breakfast Talks aimto promote interaction and closercommunication among personnel andcompanies in the mining and civilindustries,” Tluczek said, adding thatit provided a platform where expertiseand experience gained in civil andmining underground excavation couldbe shared, he concluded.