Storage space allocation problem at inland bulk material stockyard

We consider the storage space allocation problem at an inland bulk stockyard, which aims to find an effective way to store the shapeless materials. Due to the specific storage and handling means in the stockyard, unloading, stacking and reclaiming operations need to be scheduled in an integrated manner. Viewing the space of each stock pad in the yard as a series of unit slots, we first develop a novel MIP formulation which can avoid generating scattered small fields. We then decompose the model by exploiting the relationships among the above operations, and develop a logic-based Benders approach to solve it optimally.