Determination of permanent deformation of flexible pavements using finite element model

Theunbound granular material used in flexible road pavementsexhibits an elastoplastic behaviour under repetitive traffic loads. Permanent deformation occurring on pavement surface under traffic load is one of the main road pavement problems affecting road performance. Therefore, many permanent deformation models for calculating road pavement rutting have recently been developed by researchers. Most of these studies involve performance of dynamic triaxial tests. In this study, deformation characteristics of unbound granular materials are determined using the resonant column test. Then, instead of determining the total permanent deformation by summing up the calculated permanent deformations obtained in each pavement layer, dynamic 2D axisymmetric finite element analyses are performed for four different pavement cross sections to predict the total permanent deformationoccurring on pavement surface under certain load cycles. The first modelled cross section of unbound granular material consists of natural aggregate. The base and/or subbase of remaining three cross sections consists of steel slag waste material. The permanent deformation versus load cycle is presented for four multi-layer road cross sections using semi logarithmic graphs. Finally, the permanent deformation model equation is developed for each pavement cross section using their fitting curves.