Modern Mining June 2016

TECHNOLOGY

developed by Herrenknecht

design and detailed engineering for it was completed in 2013. The SBM is capable of sinking shafts between 10 m and 12 m in diameter at three times the rate of conventional shaft-sinking methods. “We are talking about a machine that was designed to achieve a sinking rate of over 10 m a day – and for a performance such as this a massive machine with plenty of power is needed,” comments Roos. Most of the technology used in the develop- ment of Herrenknecht’s blind-shaft machines – such as drilling and rock support – was adapted from technology developed for the company’s internationally recognised tunnel- ling business. As a result, the SBM is similar to a conventional tunnel boring machine, except that it is suspended vertically in the shaft and employs conventional disc cutting in a unique setup. Herrenknecht engineers chose the disc-cut- ter option for the SBM when it was ascertained that roadheaders could not be used effectively when cutting rock with a compressive strength of more than 120 MPa. The massive cutting wheel employed in Herrenknecht’s Shaft Boring Machine has a diameter that equals the excavation diameter of the shaft (10-12 m). The 60-m long SBM is self-suspended by a set of grippers. Up to three systems brace against the shaft wall to stabilise the entire sys- tem during cutting. Herrenknecht’s Shaft Boring Roadheader (SBR) was developed for blind-shaft boring in soft-to-medium rock or frozen ground to depths of 1 000 m. Two of these machines are currently in operation on the Jansen project in Canada. “The two SBRs were manufactured and assembled at Herrenknecht’s premises in Germany, where cutting tests were performed to the customer’s satisfaction before being shipped to Canada where they have been in operation since 2013 at the project,” says Roos. This rapid rock excavating machine is equipped with a rotating cutting drum installed on a telescopic and slewable boom with the result that it is flexible and can be used to cut shafts of variable diameters. The telescopic boom also allows for the excavation of the entire shaft cross-section to a depth of 1 m in a single operation. While sinking a shaft, the unit is suspended by ropes connected to shaft winders on the

surface. As with the gigantic SBM, this smaller machine had to provide safe working con- ditions for operating personnel while again exceeding the sinking rates achieved by con- ventional shaft-sinking practices. The Shaft Boring Cutterhead (SBC) is the third machine in Herrenknecht’s stable of blind- boring equipment. One-third shorter (40 m) than the SBM and with a mass of 350 tons, it is well-suited for the excavation of deep blind shafts up to 9 m in diameter in hard rock con- ditions and is capable of delivering an advance rate of 6 m a day. The SBC utilises a conical-shaped, full- faced, cutter head equipped with disc cutters and the cutting sequence is highly automated. This mechanical shaft-sinking unit is sus- pended from and moved by shaft ropes. “For all machines across the range, the three basic functions – excavation, rock support and installation decks – are common,” notes Roos. “During normal operations the crews are not exposed to an unsupported shaft wall and hence falling rock, nor silica dust. No explosives are

The Shaft Boring Roadheader (SBR) was developed for blind-shaft boring in soft-to-medium rock or frozen ground to depths of 1 000 m.

June 2016  MODERN MINING  21