Where to Make the Transition from Open-pit to Underground?: Using Integer Programming

Abstract

The transition from open pit (OP) to underground (UG) is one of the challenging mining engineering issues. The mines which have the potential to make transition from OP mining to UG mining will eventually come to a point introduced as a ‘Transition Point’ where it needs to determine whether to extend the pit or switch to UG mining. This research proposes a new integer programming (IP) formulation to obtain the optimal transition point from OP to UG mining. The proposed model has been implemented on a three-dimensional (3-D) gold deposit and a two-dimensional (2-D) case study has been used to demonstrate the validity of the model. Due to the large number of variables, strategies have been proposed to shorten the solution time. The proposed model has successfully determined the optimal transition point and generated significantly better undiscounted profit than that of the traditional approach.