PARAMETER ESTIMATES OF PAVEMENT STRUCTURE LAYERS AND UNIQUENESS OF THE SOLUTION

The question of uniqueness of backcalculated moduli of a pavement structure subjected to axisymmetric loading is addressed. Two simple examples are presented to demonstrate common difficulties associated with backcalculation, in particular problem conditioning. The sensitivity of the backcalculated solution to layer thickness, assumed Poissons ratios, and seed moduli is examined for a two-layered problem. It is shown that it may be possible to use adjusted measured falling weight deflectometer (FWD) data together with static analysis to effect backcalculated moduli for the subgrade. However, it is concluded that the calculation of the pavement moduli from surface displacement data may not yield representative in situ pseudoelastic moduli because of the nature of multilayered stress analysis and problem conditioning.