Sandsloot open pit was commissioned in 1992 and over the past 7 years a number of slope and limit blasting designs have been developed. The paper discusses the evolution of these designs noting the safety, slope stability and cost saving benefits. From a slope design perspective there are numerous configurations which can be used to design the most stable yet economic final wall. Parameters that were varied to accommodate the geotechnical conditions include stack height vs. berm width and angled vs. vertical pre-splits. The evolution of the design has seen the open pit life extended and additional revenue accrued. There are a number of variables to consider when developing a limit blasting programme. Properties such as explosive type, quantity, hole diameter, as well as the number of buffers and their burden and spacing were adjusted in order to find the most effective design for the in situ rock mass conditions. The benefits were a result of the collection of detailed geological and geotechnical data, which is necessary to facilitate the evolution process. As the knowledge of the rock mass improved so the risks associated with the slopes were reduced and not only more stable but also more economic slopes were designed. The paper illustrates the benefits associated with implementing a detailed geotechnical programme.
Sandsloot open pit is situated on the northern limb of the Bushveld Complex, 250 km north east of Johannesburg, South Africa. The current open pit is roughly 1 500 m long, 800 m wide and strikes north. The open pit is situated at an average elevation of 1 100 m and has a projected depth of 325 m. Sandsloot is currently the largest open pit platinum mine in the world and is one of six potential open pits in the area.
