VISCOELASTIC APPROACH TO RUTTING IN FLEXIBLE PAVEMENTS

Permanent deformation (rutting) in bituminous pavements is treated as a linear viscoelastic flow phenomenon and is calculated using the linear elastic layered pavement model VESYS, reported by Kenis in 1978, supplied with equivalent viscous material properties. After an initial compaction period, the model predicts that the permanent deformation per wheel pass is proportional to the static axle load and inversely proportional to the vehicle speed. The predicted permanent deformation field is realistic and independent of the material elasticity. To determine the viscosity of asphalt mixtures operating under a wide range of environmental conditions, a simple new theoretical method is introduced which is based on routine test data and requires only one parameter to be fitted to experimental data. Published wheel-tracking tests were used to determine this parameter. Rut depth predictions are compared with experimental data from a recent full-scale test in France. Agreement is generally good, indicating the applicability of this linear rutting model.