Using FWD deflection basin parameters for network-level assessment of flexible pavements

ABSTRACT

Decisions regarding the selection and implementation of appropriate pavement rehabilitation methods is usually based on pavement functional and structural condition data. Visual distress surveys and Falling Weight Deflectometer (FWD) testing are often carried out by agencies as parts of their pavement preservation programmes. Although backcalculation of individual layer moduli from FWD data is a common approach to assess a pavement’s structural condition, the accuracy of this approach is largely dependent on exact estimates of individual layer thicknesses. Coring operations to determine pavement layer thicknesses require significant time and resource commitments, and hence cannot always be accommodated within an agencies’ operational constraints. Accordingly, alternative analysis methods to assess the pavement’s structural condition from FWD data are often desired. An ongoing research study at Boise State University is focusing on combined usage of pavement structural and functional evaluation data for making pavement rehabilitation decisions. Considering the lack of pavement layer thickness information for all locations, this study is using Deflection Basin Parameters (DBPs) calculated from FWD test data to make inferences regarding the structural condition of individual pavement layers. This manuscript presents findings from this study, and establishes DBPs as reasonable alternatives to be used in network-level pavement condition evaluation practices. The adequacy of DBPs to assess the structural condition of individual pavement layers was first assessed through Finite-Element Modelling. A series of analyses were performed by assigning typical modulus values to individual pavement layers, and the corresponding DBPs were calculated. The calculated DBP values mostly fell within typical ranges specified in the literature for different layer conditions. Once the DBPs were established as adequate alternatives for making network-level pavement assessment decisions, four selected pavement sections in the state of Idaho were analyzed based on this method, and the results were compared against those obtained from visual distress assessment routines.

KEYWORDS:

• Pavement rehabilitation
• Falling Weight Deflectometer
• deflection basin parameter
• visual distress survey
• finite element modeling

Acknowledgments

Research findings described in this paper were made possible through funds provided by the Idaho Transportation Department (ITD). Special thanks to Jesse Barrus (ITD), Dave Richards (ITD), and Mart Earl (previously at ITD) for their help in the data collection, analysis, and interpretation. The authors would like to thank Dr. Mandar Khanal, Associate Professor in the Civil Engineering Department at Boise State University for his contributions in organising and managing the different project tasks. The contents of this paper reflect the views of the authors who are responsible for the facts and the accuracy of the data presented herein. This paper does not constitute a standard, specification, or regulation.

Disclosure Statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Idaho Transportation Department: [grant number Key 13103].