Analysis of pavement deflection sensitivity to variations in layer properties

Pavement surface deflections reflect the overall structural performance of the system. Deflection measurement data are often used in backcalculation procedures to estimate the properties of the layers, i.e., layer elastic moduli. In order to interpret the results of a backcalculation exercise properly, it is important to evaluate the sensitivity of the surface deflections to the property of each layer. The sensitivity of pavement surface deflections to the layer elastic moduli of an idealized pavement-subgrade system is investigated in this study via a perturbation analysis based on the Taylor's expansion. It is observed that the sensitivity to the subgrade modulus increases as one moves away from the point of load application, but decreases rapidly for the case of the pavement and base layer moduli. For the configurations under study, the deflection sensitivity to the pavement modulus becomes insignificant after a distance equal to 1.3 times the equivalent pavement thickness. The results of the sensitivity analysis are utilized to comment on the accuracy of the backcalculated parameters. Finally, the effect of uncertainty in the estimated parameters on the predicted performance of pavement systems is discussed.