A technology for non-mining flanks formation at deep kimberlite open pits

Abstract

Research objective is to develop a technology for non-mining flanks formation at deep open pits to reduce the amount of stripping operations and increase the scope of diamond fields mining by the open-pit method. Research relevance. The non-mining flanks formation and reduction of their additional excavation from the main openings is one of the most pressing problems in the development of deep kimberlite open pits. In the deep zone of kimberlite open pits, the stable slope of the flanks can reach 75°–80°, while according to the condition of ramps placement it is 48°–60°. This results in increased overburden volumes and limits the maximum depth of open pits. Methods of research. A technology has been developed for forming non-mining flanks and giving them a convex (cissoidal) profile with a gradual increase in slope angles. The technology consists in phased transition starting from a certain depth from the traditional overburden removal method to one with steeply inclined ramps and a spiral marginal tunnel passing behind the shear zone. A method for calculating the design angles of non-mining flanks when opening deep quarries with spiral ramps is substantiated. The main regularities of opening parameters effect on the slope angle of non-mining flanks are established. The results of experimental studies of rock physical and mechanical properties are used, as well as the methods of economic and mathematical modeling and technical and economic analysis. Results. By the example of Nyurba mine of Alrosa PJSC, it was found that the proposed technology allows increasing the resulting angle of non-mining flanks from 45°–48° to 54°–63°, reducing the amount of overburden removal operations by 3–8 times and effectively mining the open pit to a depth of 750 m corresponding to the depth of explored reserves. Scope of results. The proposed technology and method for calculating the design slope angles of non-mining flanks can be used not only in kimberlite open pit development, but also in the development of non-ferrous and precious metal deposits, represented by steeply dipping rounded deposits, by the open-pit method.