2-D and 3-D modeling of rutting in asphalt pavements

Permanent deformation or rutting along wheel paths is a major distress in asphalt pavement. Prediction of rutting using numerical models can serve as a useful design tool. Consequently, two-dimensional and three-dimensional finite element models were developed in this study using a commercial software, ABAQUS, to predict rutting in asphalt pavements. A visco-plastic (creep) model was used to represent the asphalt materials, while a plasticity model was used for subgrade soils. Simulation of moving loads (trucks) was considered in an approximate manner. The rutting response obtained from 2-D and 3-D models was compared for 100 passes of a single axle load. It was found that when an adequate length is considered in the 3-D idealization, the predictions from both 2-D and 3-D models are quite comparable. To analyze 100 passes in the 3-D model it took nine days on a super computer, while the equivalent 2-D model needed only two hours. A sensitivity study was conducted using a 2-D prototype pavement section including the following factors: truck speed, surface layer thickness, base layer thickness, and subgrade thickness. Results indicate that a pavement is more prone to rutting at low traffic speeds. Also, the extent of rutting is not necessarily controlled by increased pavement thickness. It is demonstrated that a FEM model with appropriate constitutive laws is capable of analyzing the rutting behavior of multi-layered asphalt pavements.