A finite element based backcalculation program for flexible pavements

In recent years pavement maintenance planning has become a main task among highway agencies. In order to determine the structural capacity of a flexible pavement, non-destructive testing equipment is used. Many countries use the falling weight deflectometer (FWD). It is possible to obtain deflection data and backcalculate the pavements' mechanical properties. However, the method used affects the backcalculated values. A user-friendly finite element code has been developed in order to backcalculate pavement properties. The problem in using any finite element program is to prepare mesh data. In order to facilitate the mesh preparation, a mesh generator have been developed. The constitutive equations for the bituminous mixture are visco-elastic, linear elastic, visco-elasto-plastic; for granular layers non-linear elastic (K-theta Model, Boyce Model, Pappin Model, Elhannani Model) and linear elastic, while for the subgrade non-linear elastic and linear elastic are used. Considerable deflection data are analyzed during the study using different models, The results indicate that the back-calculated properties depend upon the model which has been used. Therefore, using simple models can cause either over-design or under-design problems. The program is then tested against other back-calculation programs. The results indicate that the proposed program is better than other existing programs.