Optimized characterization of the permanent deformation of unbound soils and granular materials considering the master curve concept

Abstract

This paper presents a new method to evaluate the permanent deformation (PD) of soils and granular materials. Based on the concepts of shakedown and shift model, the PD analysis was proposed by means of master curves considering the initial 10,000 loading cycles of each applied stress state. Analogous to the superposition principle adopted in the construction of master curves for viscoelastic properties, the superposition loading cycle-magnitude of stress pair is proposed for the PD characterization of soils and granular materials. Thus, shift factors are used that provide the construction of master curves for each stress pair in an extended space of cycles. The master curves were used to predict the permanent deformation of soils and granular materials by increasing the number of cycles analyzed for each stress pair. For this, 24 different soils and granular materials were tested and analyzed to identify the influence of the loading cycles and stress state on the material behavior. The predictions provided by the proposed model were compared with those of another model currently used for flexible pavement design in Brazil. The results demonstrated the accuracy of the proposed methodology and indicated that it is possible to significantly reduce testing time than required for the PD characterization of soils and granular materials.