Packing theory-based framework to evaluate permanent deformation of unbound granular materials

Abstract

Permanent deformation of unbound granular materials plays an essential role in the long-term performance of a pavement structure. Stability of unbound granular materials is defined by the particle-to-particle contact of the system, the particle size distribution and the packing arrangement. This paper presents a gradation model based on packing theory to evaluate permanent deformation of unbound granular materials. The framework was evaluated by using 10 unbound granular materials from different countries. The disruption potential, which determines the ability of secondary structure (SS) to disrupt the primary structure (PS), is introduced. This study also identified the amount of PS and SS that may eventually be used as a design parameter for permanent deformation of unbound road layers. The evaluation of the model regarding permanent deformation behaviour of granular materials is found to compare favourably with experimental results.

Keywords:

• unbound materials
• gradation
• packing theory
• primary and secondary structure
• disruption potential
• permanent deformation

Acknowledgement

The authors would like to extend their sincere gratitude to the Swedish Road Administration (Trafikverket) for providing the financial support for the project.