The latest version of the Master Drilling HRB was officially unveiled at 2017 Mining Indaba, held in Cape Town, South Africa.

According to Master Drilling, the HRB technology can replace conventional drill-and-blast mining and increase mining productivity due to its continuous process of rock boring, as well as offering safety benefits.

HRB will 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 raise boring. The steady progress of the reamer is able to excavate an average 6m per day, compared to 2m in conventional drill-and-blast cycles, Master Drilling explained.

The pilot project at Petra Diamonds' Cullinan mine involved boring and excavating a 180m horizontal tunnel with 4.5m-diameter through the kimberlite ore, i.e. diamond deposits. The construction method entails 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 used vacuum air suction and laser-assisted directional steering, in collaboration with a US-based company, which is typically used in civil construction.

Ben Swarts, group manager of mining projects at Petra Diamonds, said: "Tunnel-cutting technology seems to be the next logical step in underground mine development.

"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."