Technical information

6-4
Thereafter, the loading and environment at NCAT were simulated and the advanced
models applied to forecast measured resilient responses. Referring first to the
anisotropic model, it was found that only mild improvements over the isotropic elastic
case were offered and hence concluded that the added complexity involved in the
anisotropic analysis did not prove worthy. As for the viscoelastic model, it was found
that although computationally more demanding, a relatively simple calibration
procedure could be followed, involving laboratory test results and one additional free
parameter over the isotropic elastic case. The resulting calculations generated superior
forecastability compared to the other two theories suggesting that this model should be
preferred in the future. It is important to note that the related mathematical derivation
was based on the elastic-viscoelastic correspondence principle, considerably
simplifying the computational implementation, allowing readily available elastic
programs to be utilized.
6.2 RECCOMENDATIONS AND IMPLEMENTATION
As previously stated, the main objective of this study was to try and link INDOT’s APT
results with those obtained at NCAT for nominally similar pavement systems. In the
present work this objective was pursued by means of a mechanistic approach given that
establishing a direct comparison was deemed unachievable. However, since both
experiments were not a priori designed and carried out with a pure mechanistic
interpretation in mind, the collected results limited the analysis efforts to dealing with
resilient responses only, disregarding performance, i.e., permanent deformations
(rutting) and load induced cracking. Henceforth, as a general recommendation, it is
suggested that the traditional (empirical) approach of using APT studies as ‘rut testers’
or ‘pavement comparators’ be completely abandoned for future APT studies in favor of
more modern (advanced) uses. The benefits gained from employing
empirical/oversimplified approaches in the past are mostly exhausted, and if meaningful
improvements are to be made in the pavement design field, future efforts should be
placed on developing a more rational framework.
Subsequently, it is proposed that future APT research studies should aim at
developing a mechanistic scheme for applying APT results to field conditions for