Reducing Waste Handling by Optimizing Slope Angles in Compact Rocks: A Contribution to the Circular Economy

To extract ore from open pit mines, the associated waste material must also be removed. In most mining operations, the amount of waste rock is greater than the amount of ore. Waste from the pits is usually disposed of in piles, which results in environmental impacts, such as alterations in the natural landscape, possible contamination of soil and water, and the generation of dust and particulates. One way to reduce these environmental impacts and achieve a circular economy (CE) is to use waste rock to construct the pavement layers of mine roads. Another possibility would be to move only the amount of waste necessary to release the ore of interest; in addition to reducing costs, this approach would reduce the volume of waste disposed of in piles. In this study, to reduce the movement of this compact waste, a change in the planned slope is proposed, and the compact waste and surplus material in a long-term mining plan are evaluated. The new optimized geometries, which meet the requirements for road pavement material and remain stable, as indicated by 2D geotechnical finite element modeling, were incorporated into the mining plan of Pit A, an iron mining complex in northern Brazil. The new mining plan was further subjected to economic analysis, which revealed the variations in the tonnage of ore and waste rock (mostly fresh mafic), as well as the change in the net present value (NPV), compared with the original mining plan. The results indicated that the change in geometry led to a reduction of 4.42 Mt in fresh mafic movement. This reduction directly impacted the NPV of the mine plan, with an increase of US$6.88 million.