CAPE TOWN (miningweekly.com) – JSE-listed drilling services provider Master Drilling announced at the Investing in African Mining Indaba on Tuesday that its horizontal raiseboring (HRB) technology is ready for international roll-out after a successful pilot test at the Cullinan diamond mine, in Gauteng.

Master Drilling CEO Danie Pretorius told conference delegates that HRB could replace conventional drill-and-blast mining and that it held great potential to increase mining productivity owing to its continuous process of rock boring, while also offering significant safety benefits.

He further said the HRB technology would enable more mining construction projects to meet the feasibility rates required to become producing mines.

“Projects with less safe access, such as deeper mining operations and higher stress zones are also more likely to pass feasibility tests owing to the safety improvements that HRB offers,” Pretorius asserted.

Moreover, he stated that the HRB system was locally developed, “world-first” technology that promised to change the very fundamentals of the global mining industry.

“The feedback from our multinational business partners from Southern Africa and Latin America on visits to the actual technology has been highly encouraging.”

Pretorius remarked that HRB would provide the mining industry with an excavation and construction tunnelling tool for the mechanical excavation of a tunnel between two existing access points, very similar to the standard form of raiseboring. He added that the steady progress of the reamer meant it was able to excavate an average of 6 m a day, compared to 2 m a day in conventional drill-and-blast cycles.

“This technology offers the much-needed mechanisation to reduce the number of workers who are exposed to dangerous underground conditions,” Pretorius highlighted.

ADDITIONAL BENEFITS
The benefits extend across the project-chain and include the elimination of explosives, which meant that there would be no blast effected damage inflicted to the tunnel sidewalls.

Pretorius noted that, through the use of HRB, the structure of the tunnel was stronger owing to the circular profile of the tunnel; and the technology reduced rock support costs, improved tunnel construction accuracy and lowered excavation costs.

He added that the new system ensured that continuous operations would not be affected by blast re-entry and that there were greater remote operated possibilities.

Further, Pretorius noted that, in certain locations, it would be impossible to assemble a tunnel boring machine (TBM) owing to its length and size. In these locations, the plant for raiseboring was smaller and easier to transport.

TRIAL PROJECT RESULTS
Meanwhile, he said the pilot project at Petra Diamonds' Cullinan mine involved boring and excavating a 180 m horizontal tunnel with a 4.5 m diameter through the kimberlite ore.

“The construction method entailed first drilling a smaller pilot hole through the kimberlite, which was challenging as no water can be used for flushing. The pilot hole also needed to be near perfectly straight.

“For these reasons, Master Drilling pioneered the use of vacuum air suction and laser assisted directional steering in collaboration with a US-based company, which is typically used in civil construction,” Pretorius elaborated.

Additionally, Petra Diamonds mining projects GM Ben Swarts stated that tunnel cutting technology seemed to be the “next logical step” in underground mining.

“This technology brings with it additional benefits, such as improved excavation integrity and safety, better advance rates and possible downstream financial benefits.

“The HRB is one of the very few options currently in operation. We are optimistic about the technology and in progress to finalise a commercial agreement to continue the use of the HRB within Petra Diamonds,” Swarts concluded.