Mathematical modelling of waste rock management through incorporating open-pit waste rocks in underground stope filling: An environmental approach

Reducing the footprint of waste rock dumping would result in cost savings and mitigate the environmental impacts of mining. This study develops a mixed integer programming model for waste rock management, aimed at identifying the optimal dump location among surface waste dumps and underground stopes. The model generates an optimal waste rock dumping schedule and proposes the best destination, with the objectives of minimizing the total cost of waste rock hauling and maximizing the supply of filling materials for backfilling underground stopes from the waste rocks. By applying the model to a real metal mine, a total cost reduction of approximately 14% was accomplished by utilizing open-pit waste rocks as underground filling materials, replacing alternative sources. Sensitivity analysis approved that supplying the filling materials from waste rocks was a priority, which resulted in a reduction of 3,750,000 tonnes of dumping waste rocks on the surface and a significant reduction of the waste dump environmental footprint. The model not only improves the economics of mining operations but also mitigates the environmental impacts of open-pit waste rock dumping by using waste rocks for backfilling underground stopes instead of supplying materials from outside the mine.