APPLICATION OF QUEUING THEORY FOR OPTIMUM UTILIZATION OF EQUIPMENT IN EMBANKMENT DAM CONSTRUCTION PROJECT

Abstract

The construction of embankment dam is part of earthmoving operations and requires the use of different heavy and costly construction equipment and methods of construction, which affects the overall cost and time of the project. Therefore, optimum utilization of equipment is a critical task for the project management team resulting in considerable savings in both time and cost of the project. As earthmoving related activities have a stochastic nature, optimum utilization of equipment is a complex task and cannot be described accurately by ordinary mathematic model. In common practice, the equipment required for a project is selected using average operating cycles, neglecting the stochastic nature of operations and equipment. Ultimately this can lead to rough estimates and poor results in meeting the projects’ objectives. This research concentrates on formulation of a queuing model for optimum utilization of equipment in the construction operations of embankment dam in order to maximize the profit or minimize costs and decreased a project duration by utilizing the actual project data. The entire construction operation is separated in to two queuing systems: the haulage and Placement Queuing system. By assuming single and multiple servers, Poisson arrivals originated from finite population and exponentially distributed service times, first-come, first served service discipline and infinite queuing area, M/M/1/∞/N/FCFS and M/M/S/∞/N/FCFS queuing models have been developed for single server and multiple servers respectively. The representative queue behaviors (such as server utilization, the idle probability of servers, queue length and waiting time) and important output parameters (such as production, project duration, cost/h and cost/unit) for each possible fleet arrangements are performed. An actual case study, Ajima chacha embankment dam construction project, are presented in order to illustrate the effectiveness of the proposed model. The validity of the proposed model is tested with a comparison of the results of conventional (deterministic) methods.