Queues, Construction Operations and Optimization

Abstract

Certain construction operations lend themselves very neatly to be modelled as queueing processes. In particular earthmoving type operations are shown to be naturally modelled as finite source queueing processes or cyclic queueing processes. Such models take account of the variabilities in the operations as well as the interaction of equipment. Using two-stage cyclic queueing processes under various probability assumptions as a basis, the paper develops optimization in the planning and management of earthmoving operations. Specific problems formulated and solved include the choice of the optimal hauling unit fleet size, optimal loading policies, optimal heterogeneity (mix of equipment), optimal operation layout, optimal choice of equipment characteristics and optimal preemptive and non-preemptive priority treatment of equipment. The objective functions are typically cost, production, cost per production or equipment utilization. Constraints may include time, production or other considerations. The use of optimal planning and management strategies is shown to provide a more rational framework than conventional earthmoving procedures. In the process of developing the optimal strategies, new queueing models are put forward to handle the idiosyncrasies of the civil engineering problems considered.