A model for open-pit pushback design with operational constraints

Open-pit mines are surface excavations created to extract valuable material which, in most cases, is located near the surface. Pushbacks are connected regions of a mine with enough working area to support the mining operation over a defined period. Pushbacks designed without taking into consideration haulage ramps are defined here as semi-practical pushbacks. We introduce a new optimisation model for semi-practical pushbacks that accounts for operational conditions: minimum operational width and connectivity within the blocks that compose the pushbacks. Additionally, we propose an algorithm that uses a Sliding Window Heuristic, variable bounding, and other preprocessing routines to obtain solutions with less than 10% optimality gap for mining instances ranging between 30,000 to 50,000 blocks.