Geotechnical behaviour of spent ore - impacts of metallurgical factors

Operational aspects and case histories of mine waste storage


Rigo Rimmelin


BHP

Heap leach pads are composed of mined ore, usually crushed, disposed on liners to be processed with leach solutions, and the tail of the process is called “spent ore” which are then transported by conveyor belts to be disposed into dumps. It is often to observe stability problems in these dumps, that could affect the equipments working on it and the continuity of the whole mine process. These problems are related to an excess of humidity of the spent ore, therefore the operational efforts are focused onto control this parameter.

This work present the results of different geotechnical laboratory testing, using samples of spent ore of a mining operation in the north of Chile. Since 10 years, it has been made 3 campaigns to get samples, in which it was obtained valuable information to identify how specific operational/metallurgical factors could affect the geotechnical behavior of the spent ore. Special attention is given to the decision to change the metallurgical process adding salt to the heap leach process and its impact to its hydraulic conductivity.

Historically, the process had been based on the leaching of oxides and sulfides materials, in separate campaigns, in which it is possible to observe different geotechnical response in the spent ore generated. Recently, it was implemented a new process in which the materials are blended and salt is added, to improve metallurgical performance in terms of recovery. This change generate impacts in the dump, since the geotechnical parameters are affected  decreasing hydraulic conductivity in about one order of magnitude (explained by the salt added).

It is shown changes in the geotechnical parameters of the spent ore, considering that the mining source is the same, and how the operational process and dump design are affected.

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