Developing Seasonal Pavement Design Models Using Falling Weight Deflectometer Testing: Fid-Bau Portal

Developing Seasonal Pavement Design Models Using Falling Weight Deflectometer Testing

Orr, D. P. / Irwin, L. H.

Development of seasonal pavement design models requires understanding of the various factors that can affect the models as well as a practical understanding of model development and pavement design. The New York State Department of Transportation (NYSDOT) desired a statewide seasonal model of pavement moduli to augment their current pavement design methods and to use with the new mechanistic-empirical pavement design approach being developed by NCHRP. Due to a limited project budget, development of a seasonal model for the entire state was unfeasible. Instead, the primary project goals were to develop a seasonal pavement design model for the limited inference space defined by the testing sites and to determine an efficient approach for development and expansion of such seasonal models. In working with NYSDOT, the development of the experimental design was influenced by economic considerations and practical time constraints. Rather than spend project funds on expensive laboratory testing with a low probability of use in the future, it was decided to perform more falling weight deflectometer (FWD) testing to define the spatial and temporal variations in pavement response. The results of this initial phase provided a series of lessons learned that resulted in a final approach for seasonal model building. In order for a seasonal pavement model to be developed using FWD testing, climatic analysis of the possible inference space must be completed to define climatic regions based upon expected pavement response. This analysis must define seasons in reference to how they will affect pavement design. In New York State, with its large variation in pavement response due to freezing and thawing of the unbound layers, five or six seasons are needed. In addition, the climatic analysis must determine the minimum number of FWD tests to determine the variations in the response of the pavement. The geotechnical and site investigation plan should use existing protocols as much as practicable without adversely compromising data needs. Prior to the FWD testing, a comprehensive, but flexible, testing and data analysis plan is critical. The FWD data must be analyzed as they are collected. Finally, the assumptions of the pavement model in backcalculation of the data and the forward calculation in the pavement design must be synchronized to allow proper comparisons. Model development must include spatial and stochastic variations in the real world and needs to be validated with real world data.