Phase LAG Effects on Analysis of FWD Data

    Published: Jan 1994

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    The research documented in this paper examines the effect the phase lag has on the analysis of FWD data. The research examined the use of a deflection basin generated from the peak sensors' deflections, a deflection basin generated from instantaneous deflections based on peak load, and a deflection basin generated from instantaneous deflections based on the peak deflection at sensor #1. The influence of the various analyses is evaluated by comparing the material properties produced by each individual analysis and their relative impact on the recommended overlay thickness.

    The analysis of the data indicated that almost all of FWD field data have instantaneous deflection basins which greatly differ from the deflection basin generated by the peak response. The backcalculation data indicated that the type of analysis may have a significant effect on the magnitudes of the moduli of the layers. Finally, the overlay analysis showed that there are significant differences among the recommended overlay thicknesses based on the different analyses. The differences were as high as 1.5 inches in some cases.


    backcalculation, falling weight deflectometer, phase lag, deflection basin, overlay thickness

    Author Information:

    Sebaaly, PE
    Assocaite Professor, University of Nevada, Reno, NV

    Holikatti, S
    Research Assistant, University of Nevada, Reno, NV

    Paper ID: STP18155S

    Committee/Subcommittee: D04.39

    DOI: 10.1520/STP18155S

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