United States Department of Transportation
i
A Mechanistic Approach to Utilize Traffic Speed Deflectometer (TSD) Measurements into Backcalculation Analysis
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2019-05-01
[PDF-3.80 MB]
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Edition:Final report
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Abstract:Backcalculation analysis of pavement layer moduli is typically conducted based on the Falling Weight Deflectometer (FWD) measurements; however, the stationary nature of FWD requires lane closure and traffic control. To overcome these limitations, a number of continuous deflection devices were introduced in recent years including the Traffic Speed Deflectometer (TSD). In this study, a mechanistic-based approach was developed to utilize TSD deflection measurements in the backcalculation analysis. The proposed approach is based on the 3D-Move software to calculate the theoretical deflection bowls corresponding to FWD and TSD loading configurations. Since 3D-Move requires the definition of the constitutive behavior of the pavement layers, cores were extracted from 13 sections in Louisiana and were tested in the laboratory to estimate the dynamic complex modulus of Asphalt Concrete (AC). Afterwards, 3D-Move generated deflection bowls were field-validated with an acceptable accuracy. The 3D-Move models were then used in a parametric study consisting of pavement designs of varying thicknesses and material properties and their corresponding FWD and TSD surface deflections were calculated. The results obtained from the parametric study were incorporated into a Windows-based software application, which uses Artificial Neural Network (ANN) as the regression algorithm to convert TSD deflections to the corresponding FWD deflections. This conversion would allow backcalculation of layer moduli using TSD measured deflections, as equivalent FWD deflections can be used with readily available tools to backcalculate the layer moduli.
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