Engineering & Mining Journal

APR 2019

Engineering and Mining Journal - Whether the market is copper, gold, nickel, iron ore, lead/zinc, PGM, diamonds or other commodities, E&MJ takes the lead in projecting trends, following development and reporting on the most efficient operating pr

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SHAFT SINKING 42 E&MJ • APRIL 2019 www.e-mj.com Slavkaliy began the planning phase for the Nezhinskiy potash mine near Soligorsk, Belarus, eight years ago. In July 2017, the company began working with Deilmann- Haniel , a member of The Redpath Group, to construct two freeze shafts and approx- imately 9,000 meters (m) of horizontal excavations. The difference between this shaft-sinking project and previous ones in the region is that it will use Herren- knecht's Shaft Boring Roadheader (SBR). As the name implies, it's based on the rock-cutting priniples of a roadheader. A similar system was used to sink the Jan- sen shaft in Saskatchewan, Canada, and others are considering it for softer orebod- ies. The SBRs that will be used in Belar- us, however, have been improved based on the experience gained on the Jansen project. They were optimized specifically for clay and sandy material with a com- pressive strength of 100 megaPascals. The combination of the freeze shafts and the rock's low compressive strength al- lows the use of the SBR technique to sink these shafts. This technique has proved to be safe and efficient. Shaft boring es- sentially eliminates the use of explosives, which also greatly reduces the number of people at shaft bottom during develop- ment. The SBR on average is expected to advance 3 meters per day (m/d), which is a significantly higher rate than conventional shaft-sinking methods. How can this be? Boring, transporting the cuttings to the surface, and installing the concrete lining can be carried out simultaneously. Structure and Operation of the SBR The SBR technique combines different machine components with a convention- al shaft-sinking platform. As a result, the following functions are performed on a total of 11 work decks: • Cutting; • Extraction of the mined material from the bottom; • Transport of the mined material to the surface; • Transport of people; • Establishing support; and • Ensuring supplies (electrics, hydraulics, ventilation, data, cooling water, etc.) A 1.2-m telescopic boom, which can be rotated 360°, sits directly above the shaft floor. At the end of the boom, a cutter drum that measures 1.2 m in di- ameter and 1.5 m in width is driven by 600 kilowatts (kW) of hydraulic power. It can be equipped with round shaft chisels or scraper blades, with which the rock is loosened. The cutting on the shaft bottom is done automatically with star-shaped patterns in 200-mm increments. The cuttings are removed from the shaft floor using a pneumatic suction system (PNM system), which transports it through a 30-m-long pipe located in its center. An aero-cyclone places the cuttings in a bucket located on a rotary table. This table, which can be rotated by 180°, has the bucket on one side, which is loaded via the PNM system, and an empty bucket on the other side. When one bucket is full, the rotary ta- ble is moved, the full bucket is transported to the surface for tilting, and the other is connected to the PNM system. The air from the cyclone is scrubbed and discharged on the surface. Three 315-kW rotary blowers generate the negative pressure. The exhaust air is approximately 70°C. To prevent defrosting of the shaft wall, a cooling system was installed, which trans- fers the heat via cooling water pipes to a cooling system aboveground. Two branch- es run through the entire SBR for trans- Boring the Shafts at Slavkaliy's Nezhinskiy Project Shaft-sinking crews flatten the SBR learning curve with experience Headframes at the Nezhinskiy potash project support two 1,300-m shaft-sinking operations. A shaft-sinking platform is being assembled in the foreground. (Photo: The Redpath Group)

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