Evaluation of Rutting and Reflective Cracking in Pavement Overlay Design for Iranian Tropical Zones

Subgrade rutting model is one important criterion in pavement and overlay mechanistic design. Fatigue model for pavement mechanistic design methods is based on tensional strain under asphalt layer. But for overlay mechanistic design tensional strain may sometimes be under asphalt layer and sometimes under overlay layer as well as to be. Permanent deflection model is also based on the compressive strain under subgrade layer; on the other hand, the model is not correct for cracking pavement overlay design to assess fatigue or permanent deflection life, with regard to the progress of reflecting cracks and other destructions.In this study, subgrade Permanent deflection life of overlaid pavement is analyzed and compared with compressive strain above subgrade. The Kenlayer analytic software is used to analyze overlays with different thicknesses (thin, mid and thick) above pavement with different thicknesses (thin, mid and thick) in Iranian tropical zones and to determine the amount of the critical standards of permanent deflection compared to reflecting criteria.