Most current methods of flexible pavement design take onlythe stiffness of materials into account in terms of the resilientmodulus and the theory of linearized elasticity is utilzed todeterminee the principal criieria of rutting and fatigue life.The need to incorporate elastic and vlsco-elastic or plastic modelsinto practical flexible pavement design procedure is now wellfounded. The main purpose of this research is to demonstrate theimportance of plastic parameters and their attendant residualstresses and strains on pavement life.

The elastic and plastic behaviour of materials from three AcceleratedLoading Facility (ALF) sections were characterized using a repeatedload triaxial apparatus. The Mechano-Lattice (ML) elasto-plastic,Visco-elastic (VESYS) and linear elastic (adapted CIRCLY) analysiswere used to predict the performance of three ALF trials. It wasfound that the predicted rutting by Mechano-Lattice in all caseswas close to the field and was superior to VESYS and adapted CIRCLYmethods. VESYS and Mechano-Lattice analysis have shown that inSomersby section no cracking should occur before 7.3 x 10^5 repetitionsof 80 kN load. This is supported by ALF test results. The CIRCLYanalysis has shown that cracks will happen before the above repetitions.By ML analysis it is observed that if residual stress accumulationwas ignored, bottom lateral cracks would commence according toCIRCLY predictions, but residual compression stress cause thetransient stresses to reduce as passes continued.