Plant Equipment and Hire February 2020 | Page 16

ON SITE Koos Jordaan, executive director and technical director at Master Drilling (centre) with mining analyst Peter Major, director of Mining at Mergence corporate solutions (left) and Leon Louw, editor of Plant Equipment & Hire and African Mining (right). According to Jordaan there are a lot of similarities between the shaft boring, tunnel boring and raise boring – where the machine cuts rock in a circular path and then crushes it. The first question when excavating a blind shaft, is of course, how to remove and lift the material. “To solve the problem, we decided to drill the blind end at a small diameter and follow it with a larger diameter drill which means less material to get rid of. The bulk of waste material is fed via gravity into a kibble,” explains Jordaan. At the bottom of the shaft borer is the boring machine which includes the cutter head and a massive gearbox. The boring machine basically crushes the rock with brute force, moving up and down. The cutter head excavates the blind sink and the gearbox drive splits energy between the pilot and the reaming section, which consists of grippers similar to that found on Master Drilling’s Tunnel Boring Machine (the Tunnel Boring Machine excavates horizontal tunnels and can be used in a number of mining and construction applications). A worm down a shaft Master Drillings’ revolutionary shaft borer and vacuum system. Faster, safer and cheaper “We believe that if you can bore something it’s a lot better than blasting it,” says Jordaan, whose team has been at the forefront of developing technology with the aim of disrupting the shaft sinking and tunnel boring industries. “In a world where energy efficiency, pollution and global warming are becoming prominent issues, we need to do things more sustainably, smarter, better and more effectively, adds Izak Bredenkamp, group business development manager at Master Drilling. “An increasing global population will continue demanding resources like minerals, fuels and metals. This means that mining companies have to reach ore bodies quicker, safer and more cost effectively than what they have been able to do in the past, and that is a 14 JANUARY/FEBRUARY 2020 challenge. We want to make sure mining companies stay ahead of the pack, and our response is finding ways for them to get there safer, quicker and faster,” says Bredenkamp. Master Drilling hopes to bring the full system to the market within the next year. Intricate and unique system Jordaan explains that the borer will be able to cater for different diameter shafts from 7.5m to 11.5m wide. It can be used in either a blind sinking mode, or in conventional raise bore type applications, where the geology is not that competent at large diameters. It is possible for only three or four people per shift to man and operate the machine once it has pierced the top ten metres of soil and rock. An additional 20 plus people will be needed to perform on-surface general functions. The grippers and advance system pushes and pulls itself like a worm down the shaft, while the reamer head excavates the shaft and the material drops into a kibble, located inside the cutter head. Rock cuttings are fed into this kibble via gravity. The kibble with the crushed rock is lifted about 50m to the service stage from where the excavated material is conveyed to the surface. The distance between the pilot drill and the reamer is about 7m. The pilot drill advances about half a metre before pulling the reamer head down. Jordaan explains that the short distance between the drill and the reamer needs to be maintained to ensure proper shielding as the area is not supported yet and is vulnerable to instability. The initial pilot hole is about four metres in diameter, while the reamer cuts a shaft of anything from seven and a half to 11m in diameter. On the main stage Four metres behind the boring machine is the main stage that contains all the power packs and intelligence. Two to five people will work in this stage, providing primary support. A shield structure protects workers on the stage until they have installed the required support. While the machine is busy excavating, the crew on the stage carries out all the required support work on the excavated shaft. They drill nine to 12m long anchors into the wall, and 2.4m bolts will lend further primary www.equipmentandhire.co.za