Waste rock dumping optimisation using mixed integer programming (MIP)

Abstract

Despite the fact that waste rock hauling and dumping comprises a large proportion of the cost of materials handling in an open pit mine, little detailed planning is devoted to optimising waste rock dumping. The lack of such planning could result in long-term exposure of potential acid forming (PAF) waste rock, causing acid mine drainage (AMD), which would incur ongoing collection and treatment costs. A waste rock dumping plan that not only minimises hauling costs, but also involves the encapsulation of PAF waste rock to minimise AMD, would benefit a mining operation economically and environmentally. In order to create such a plan, two new mixed integer programming (MIP) models are formulated and tested with a five-year mining schedule. Optimised dumping plans are automatically generated, which detail the dumping location for each mining block. A manual approach is also attempted, and comparison shows that the MIP models have obvious advantages in error prevention, faster solution time and cost saving, by up to 9.5%.