SYMPOSIA PAPER Published: 01 January 1989

Backcalculation of Layer Moduli from Nondestructive Pavement Deflection Data Using the Expert System Approach


None of the existing backcalculation procedures is guaranteed to give a reasonable, effective elastic layer modulus for every deflection basin measured. The differences of results among various backcalculation programs are magnified by the differences of distinct analysts using the same program but applying different input parameters. A more experienced analyst often may obtain better results. Some of the difficulties, such as the deviation of pavement material properties from the linear elastic, isotropic, and homogeneous assumptions, the uncertainty of input parameters (for example, the deflection measurement), and the limitation of basin matching techniques, may only be dealt with by informed engineering judgement. A knowledge-based expert system approach as described in this paper may be used to generate more consistent and better estimations of in situ pavement material properties by combining numerical computations with a pavement expert's knowledge and judgement. A knowledge base which serves as an intelligent pre- and postprocessor to the backcalculation program is developed. The knowledge base may be revised easily as better understanding emerges.

Author Information

Chou, YJ
Texas Transportation Institute, Texas A&M University, College Station, TX
Uzan, J
Texas Transportation Institute, Israel
Lytton, RL
Texas Transportation Institute, Texas A&M University, College Station, TX
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Developed by Committee: D04
Pages: 341–354
DOI: 10.1520/STP19816S
ISBN-EB: 978-0-8031-5087-4
ISBN-13: 978-0-8031-1260-5