Modeling uncertainty in operations with nonstationary cycle times

This paper describes an approach for probabilistic analysis of construction operations in which nonstationary cycle times have a major impact on production. A nonstationary cycle time is defined as a cycle time that varies with the passage of time and project progress. Examples of projects in which nonstationary cycle times affect production include linear operations such as highway construction and tunneling operations. As the project progresses the haul time of the earth-moving equipment increases. Although the proposed approach is sufficiently general to be used with various types of construction operations, the specific model presented was developed for tunneling operations. The model predicts the muck-handling requirements of the tunneling operation at the desired level of confidence. Application of the model is shown through a numerical example, and the results are compared with the results of a conventional deterministic analysis.