Evaluation of Agent-Based and Discrete-Event Simulation for Modeling Construction Earthmoving Operations E. Zankoul, H. Khoury and R. Awwad.
One of the most common operations to any construction project is earthwork. In fact, most, if not all, construction projects begin with earthwork activities. These activities require heavy equipment, are generally quite costly and consume a considerable amount of time. On another hand, the construction industry is becoming increasingly competitive over the years, whereby the need to continuously find ways to improve construction performance. In order to address the aforementioned adversities, this paper takes the initial steps and presents work targeted at efficiently managing logistics of earthwork operations in the construction field, namely cut and fill processes, and hauling activities. This dynamic and complex problem, which entails a lot of parameters and variables, is addressed in detail through creating two simulation models, a Discrete-Event Simulation (DES) model and an Agent-Based Simulation (ABS) one, using the multi-method simulation software AnyLogic 7.1. The purpose behind this study is twofold: (1) capturing and visualizing the interaction among the different resources or entities in an earthmoving operation and defining the weak links in order to improve the efficiency of such activities onsite, and (2) comparing DES and ABS approaches and evaluating the advantages and drawbacks of each when modeling earthmoving operations. Results of both approaches are presented and analyzed with regard to improving performance of earthmoving operations, followed by a discussion of the application and effectiveness of using each of the presented simulation approaches in modeling construction activities.
Information Computer Technology (ICT) tools have been increasingly developing which is enhancing their use in the field of construction. For instance, simulation modeling and visualization are often used at the stage of planning to improve construction performance and efficiency. Different types of simulation approaches have been used to mimic construction operations among which Discrete Event Simulation (DES) ranks as the most widely used one. A newer simulation approach, Agent Based Modeling (ABM), emerged later in the 1990s. In construction, one of the most common and expensive activities to any project is earthwork operations, which explains the necessity of simulating and analyzing such processes which provides insight to achieve cost savings and higher operation efficiency.
Previous research efforts aimed at comparing DES and ABM in different fields such as Operations Research and the implementation of new management policies. These studies conclude that each simulation modeling type has its advantages and its disadvantages and selecting a type should depend on the problem and scenario modeled   . Other studies have focused on modeling earthwork operations using DES approach  . As for ABM, although it is still not widely used in construction, some papers used it to study construction labor productivity on site , to estimate the productivity of bored piles , or even to model earthmoving operations . However, in the case of the latter, the model focused mainly on managing logistics, spatial time clashes and safety.
In this paper, two models are created to simulate earthwork operations, one following the discrete-event method and the other using ABM approach. The two models are accompanied with a 3D animation for validation purposes and are tested on a case study to compare the results. Then, the advantages and disadvantages of each simulation approach are highlighted with respect to earthwork operations. Finally, the potential of combining both approaches into a multi-method model is discussed.
Figure 1: Case Study Road Network Layout