Optimization of Open Pit Mining under Surpac and Whittle - Application to the Ruashi II and III Deposits

This study focuses on the optimization of pits, the search for a single project, the optimal long-term pit of the two mega-fragments of the Ruashi II and III deposit. The objective is to carry out several technical-economic analyses taking into account the changes in copper prices on the international market, in order to choose a pit that will be technically feasible and which will allow the company, to make the maximum of for the duration of the operation. To achieve this objective, the survey data on the study site allowed constructing the mineralized body and the model block, then an estimate of the total resources could be established. To obtain the optimum pit of the project, a first optimization from the technical point of view was carried out with the software Surpac, starting from the current costs on the market and while placing itself in unfavourable conditions, in order to give a scenario the most profitable as possible. The results showed that there are several possible technically optimal pits that can be carried out on the ground. These have been classified into three families. These families have been the subject of three different projects. The first pit family comprises all the pits for which the average copper price varies around $2 800/ton on the market. The second family comprises all the pits for which the average copper price varies between $3500 and $4200. The price that was chosen for this category is $3800; this is the average of the values. The third family includes all the pits, the price of which varies between $5 200 and $9 100. Here also, the average of the values worth $7000 was retained. With the whittle software, a second optimization procedure was carried out on an economic level, taking into account separately these three projects constituted. After several techno-economic analyses, the optimum pit of the second project realized at $3 800 was retained as an optimal pit in the long term. Thus, the starting cost to obtain the best pit of this deposit was set at $3 800/ton of copper. Then an analysis of the operating sequences could be carried out to have to orient the production to the most promising places. The best case is the fact of undermining all successive benches into three push-backs. And finally the mining reserves contained within the limits of the optimum long-term pit have been determined. At a cut-off content exceeding 0.3 %, the pit retained contains a volume of 22 517 500 m3 and 48 549 986 tons of ore. The average copper content is estimated at 2.56 % and an average cobalt content of 0.41 %.