PERFORMANCE PREDICTION OF ACCELERATED LOADING FACILITY (ALF) TRIALS USING ELASTIC, VISCO-ELASTIC AND ELASTO-PLASTIC ANALYSIS

Most current methods of flexible pavement design take only the stiffness of materials into account in terms of the resilient modulus, and the theory of linearized elasticity is utilized to determine the principal criteria of rutting and fatigue life. The need to incorporate elastic and visco-elastic or plastic models into practical flexible pavement design procedure is now well founded. The main purpose of this research is to demonstrate the importance of plastic parameters and their attendant residual stresses and strains on pavement life. The elastic and plastic behaviour of materials from three Accelerated Loading Facility (ALF) sections were characterized using a repeated load triaxial apparatus. The Mechano-Lattice (ML) elasto-plastic, Visco-elastic (VESYS) and linear elastic (adapted CIRCLY) analysis were used to predict the performance of three ALF trials. It was found that the predicted rutting by Mechano-Lattice in all cases was close to the field and was superior to VESYS and adapted CIRCLY methods. VESYS and Mechano-Lattice analysis have shown that in Somersby section no cracking should occur before 7.3 x 10 to the 5th power repetitions of 80 kN load. This is supported by ALF test results. The CIRCLY analysis has shown that cracks will happen before the above repetitions. By ML analysis it is observed that if residual stress accumulation were ignored, bottom lateral cracks would commence according to CIRCLY predictions, but residual compression stress causes the transient stresses to reduce as passes continue.