STP1026

    Using NDT Aided by an Expert System to Evaluate Airport and Highway Systems

    Published: Jan 1989


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    Abstract

    The paper presents the methodology currently used by the authors for the evaluation of flexible and rigid airport and highway pavements. Using this methodology, one can determine economically and accurately the elastic modulus of: (a) the subgrade; (b) the subbase and base materials, and (c) the asphalt layer of a flexible pavement. To improve the accuracy and to reduce the sensitivity of the calculated moduli of old pavements with nonuniform characteristics, the subgrade modulus is calculated, and then the combined modulus of the pavement structure is completed. In the third step the moduli of the asphalt and granular materials are determined. The alternative way of calculating the three moduli exactly and simultaneously is sensitive to minor changes in pavement performance in terms of either deflection basin or layer thicknesses. The Hogg model of a thin plate on an elastic foundation, the Burmister two-layer model, the Odemark-Ullidtz method of “equivalent thicknesses,” and the theory of strength of materials are all used to calculate the elastic moduli of the subgrade and pavement layers. Comparison of the elastic moduli determined by the simplified methods and such “exact” computer programs as CRANLAY showed very good agreement. The Hertz-Westergaard models are used in the evaluation of rigid pavement. An expert system in airport and highway pavement evaluation projects is used to minimize the testing errors and to better calibrate the nondestructive testing (NDT) results with standard test pits. The NDT methodology presented in this paper is independent of equipment type and has been successfully used with the Pavement Profiler, the falling weight deflectometer, the 16-kip vibrator, and the Benkelman beam. This NDT methodology has been used worldwide as: (a) a design tool of pavement strengthening and rehabilitation, and (b) a quality control tool to analyze and predict the performance of adequate and marginal materials that do not meet standard specifications.

    Keywords:

    elastic moduli, pavement evaluation, nondestructive testing (NDT), expert system, Pavement Profiler, falling weight deflectometer, 16-kip vibrator, Benkelman beam, flexible pavement, rigid pavement


    Author Information:

    Greenstein, J
    Assistant vice-president and chairman of the board, Louis Berger International, Inc., East Orange, NJ

    Berger, L
    Assistant vice-president and chairman of the board, Louis Berger International, Inc., East Orange, NJ


    Paper ID: STP19827S

    Committee/Subcommittee: D04.39

    DOI: 10.1520/STP19827S


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