Modern Mining February 2016

TECHNOLOGY

company will be not be selling the machine. It will operate it itself and – depending on the reception of the market – could ultimately have several machines in its fleet. In operation, the BSBS will involve two phases of boring. The first phase will be through applying slurry drilling techniques to create a pilot shaft with a diameter of 4,8 m. The slurry will be pumped to a separation unit where the water and solids will be separated with the water returning to the slurry head and the solids being hoisted to surface. State-of-the- art technology is located within the slurry head to ensure verticality of the shaft. The second phase of boring will be when this pilot shaft is reamed to the actual shaft diameter which can be varied, as mentioned, between 10 m and 14 m. Rock cuttings created during this process will be hoisted to surface by means of kibbles and two single-drum winders. The shaft lining will be done by lowering pre- cast concrete segments which are then placed into position by means of a manipulator located on the boring machine. This technique is com- mon practice in tunnel boring operations and enables the system to minimise the length of the unlined shaft sidewall to a maximum 1,5 m. Hoisting of the cuttings will be carried out by single drum winders with kibbles – this is also a tried and trusted method of removing rock vertically. A working platform is part of the system and is lowered and raised by means of stage winders. This enables shaft inspections and maintenance operations to be done in the shaft barrel and also provides the guide ropes for the kibbles running in the shaft. The BSBS is just the latest of a series of innovations by Master Drilling, a company established in 1986 by Danie Pretorius, who is the current CEO. Last year it commissioned its RD8, one of the largest raise bore rigs in the world, and the unit is now working on the Palabora Lift II project where it is boring two 6,1 m diameter, 1,2 km deep ventilation shafts. The directional pilot drilling of the first shaft has been completed and was achieved to a high level of accuracy with the deflection from the theoretical shaft centre line being a mere 0,5 m over the 1 200 m depth in steep dipping/vary- ing rock formations. Master Drilling has also recently developed a Remotely Operated Shotcrete System (ROSS) and a Remotely Operated Shaft Inspection (ROSI) unit. The company has a gripper tun- nelling machine and on reef drilling on trial at Sibanye’s operations while a Horizontal Raisebore Machine (HRB) is on trial at Petra’s Cullinan diamond mine.

In another development, Master Drilling has established an office in St Louis, Missouri in the US. The company has been awarded a contract to establish a 350 m x 3,1 m vertical shaft for a mining client in the US. The ground condi- tions require the shaft to be lined by means of steel casings and boring of the shaft will be carried out using the reverse circulation drill- ing method. The company believes there is an attractive market for this technology, not only in the USA but in other parts of the world as well. Based in Fochville on the West Rand, Master Drilling has a fleet of 145 machines, comprising 97 raise bore rigs (more than twice the number of its nearest competitors) and 48 slim drilling rigs. It operates not only in South Africa but also in several other African countries (nota- bly Zambia) and also has a strong presence in South and Central America, a region which accounts for roughly half of its revenues. The company designs and manufactures its own machines, cutters and drill pipes. Its international arm, Master Drilling Inter­ national Limited (MDI), recently announced the acquisition of a 40 % stake in a major raisebore drilling operator in Scandinavia, Bergteamet Raiseboring Europe AB, effective 1 December 2015. The deal provides a platform to diversify into the Scandinavian region and brings an additional 18 raise bore machines into Master Drilling’s fleet. 

Master Drilling’s RD8 on site at Palabora where it is boring two 6,1 m diameter, 1,2 km deep ventilation shafts (photo: Master Drilling).

February 2016  MODERN MINING  29