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 line ar elastic layered pavement model VESYS, reported by Kenis in 1978, su pplied with equivalent viscous material properties. After an initial c ompaction period, the model predicts that the permanent deformation pe r wheel pass is proportional to the static axle load and inversely pro portional to the vehicle speed. The predicted permanent deformation fi eld is realistic and independent of the material elasticity. To determ ine the viscosity of asphalt mixtures operating under a wide range of environmental conditions, a simple new theoretical method is introduce d 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. Agreem ent is generally good, indicating the applicability of this linear rut ting model.