Irkutsk National Resarch Technical University, Irkutsk, Russia:

F. V. Dudinsky, Professor, Doctor of Engineering Sciences
K. B. Nechaev, Associate Professor, Candidate of Engineering Sciences, istuproekt@mail.ru

The analysis of the known methods for the development of placers by dredging has been carried out, taking into account the improvement of technology and equipment in our country and abroad. A number of features have been identified that distinguish the dredging method of developing deep placers from others. The possible options for setting the limits for extraction of pillars between the dredge passes, which determine values of sand loss and dilution, are presented. The features of deep dredging and the formation of pillar between the counter passes of dredges are considered. The process flow charts for placer dredging with overburden removal to external and internal dumps have been developed. The effect of dredge pass width on the minng efficiency is estimated in cases of loss and dilution. The permissible values of mineral loss in pillars between dredge passes and dilution of sands by overburden are determined taking into account the indicators and parameters of mining, using the net present value of the project as a rating criterion. The results of the implemented methodological approach to substantiating parameters of deep placer mining by contiguous counter dredging with regard to the time effect are described. This approach makes it possible to find rational parameters of process flow charts and to determine (normalize) the permissible level of loss or dilution of sands by overburden. The study into development of placers by contiguous counter dredging yields that selection of a deep placer mining scenario, determoination of technical and economic indicators as well as justification of process flow chart parameters should be based on the aggregate analysis of all possible variants of stripping and productive mining with the first and second passes across the whole width of an open pit. Efficiency of mining can be adjusted by variying the width of the counter dredge passes.

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