Flexible pavements under accelerated traffic loading: integration of surface response and internal stresses

Mechanistic–empirical pavement design depends on the consistency between calculated structural responses and observed field performance. However, most validation studies rely mainly on surface indicators, with limited experimental evidence linking surface deterioration to internal stress measurements under controlled full-scale loading. This study addresses this gap using a full-scale instrumented flexible pavement subjected to accelerated traffic loading with a Heavy Vehicle Simulator. The test section was monitored under approximately 2.47 × 106 equivalent load repetitions. Surface response was evaluated through deflection, deflection basin shape, and rutting, while vertical stresses were measured at different structural levels. The analysis combined field monitoring with multilayer elastic modeling and mechanistic–empirical prediction of permanent deformation. Results showed increasing deflection and rutting, together with a reduction in radius of curvature, indicating stiffness degradation and strain localization. In contrast, measured internal stresses did not show progressive amplification. These results suggest that structural deterioration was governed primarily by stiffness reduction and permanent deformation accumulation, rather than increased stress transmission to deeper layers. Model comparisons showed better agreement under the full-bond assumption, supporting this condition as a more realistic representation of the measured vertical stress distribution, although not as conclusive evidence of bonded behavior. Overall, the results highlight the importance of integrating internal and surface measurements for interpreting mechanistic–empirical pavement responses.