Diss. Esbo : VTT Technical Research Centre of Finland, 2008

An analytical-mechanistic method for the calculation of permanent deformations in pavements has been developed at VTT. The calculation method is needed in the analytical design procedure of pavements. The research concentrated on the calculation method for permanent deformations in unbound pavement materials. The calculation method was generated based on the test results of accelerated pavement and laboratory tests. The stress state of the pavement was modelled with finite element methods to be able to use non-linear elasto-plastic models. The deformations were calculated from the number of passes and the material parameters were defined from the saturation and compaction degrees along with loading rate, temperature and so on. The deformations in each layer were calculated and then summed to obtain the total rutting. The method was tested against two Finnish accelerated pavement tests. The results indicated that the material model gave only tolerable results for the extremely high load levels as the relative error was around ± 30%. For the thicker bound layers and lower stresses, the method gave better results. The method is also useful for the comparison of the sensitivity of different structures against rutting. The material parameters have so far been defined only for the most common materials.