A first series of ORNI calculations was performed considering only the rutting of the UGM layer, and assuming different temperatures in the bituminous wearing course (between 15° and 35°, corresponding approximately to the range of temperatures measured in-situ). The results are presented on Fig. 11.18. It can be seen that the temperature in the bituminous wearing course has a large influence on the permanent deformations of the UGM (the temperature affects the modulus of the bituminous material and, therefore, the stresses transmitted to the granular base).
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Figure 11.19 presents the results of a second series of calculations where the rutting of the subgrade soil was also taken into account. The contribution of the subgrade to the total rutting is important, representing about 40% of the total rut depth. The final rut depths obtained after 1.5 million loads, with the contribution of the subgrade, are close to the experimental measurements, especially for the temperatures of 23° and 27°, which are close to the average in-situ temperatures. However, the model predicts a too rapid stabilisation of the permanent strains in comparison with the experimental measurements.
