Production Rate Estimation Using System Dynamics (Case Study: Clamshell Excavation at Top Down Construction)

Construction projects usually face delays and do not finish on time due to many factors, including inaccurate estimation of production rates. Production rate for an activity depends on many factors that are interdependent and stochastic in nature. However, most of the available models for production rate estimation assume deterministic factors and seldomly account for the interdependencies between the various factors. This research aims to provide accurate estimation of production rates through accounting for stochastic and interdependent factors. To this effect, this paper presents the modeling and testing of a System Dynamics (SD) model for excavation activities using clamshell in top-down construction projects. SD allows for representing the interdependencies between the various elements and sub-processes of the construction process. In addition, the SD simulation process allows for depicting the stochastic nature of the various parameters that other estimation techniques fail to achieve. To achieve the desired outcome, the authors: (1) carried out a thorough literature review to study the factors affecting the excavation process; (2) collected data through questionnaires and site reports to quantify the impact of each factor on production rate and its occurrence likelihood; (3) modeled the excavation process through SD toolkit on AnyLogic simulation platform; and (4) tested and validated the model through the case study. The model was able to provide results within a mean square error of 4.14% throughout the testing phase. Although the excavation process of top-down construction activities has a lot of complexity, the presented SD model has proved able to simulate the process and provide desired realistic production rates. The model can be improved to account for more factors, in order to capture the full nature of the excavation activity, nevertheless, the modeling approach can be replicated to estimate the production rates for other complex construction activities.