Permanent deformation behaviour of a granular material used in low-traffic pavements

Abstract

Granular materials are usually used in low-traffic pavement structure as base layer or sub-base layer. The influence of fine content on permanent axial deformation behaviour is significant as well as the water content. This study aims to investigate the permanent axial deformation behaviour of the granular material under cyclic loading at various water contents and various fine contents. A triaxial apparatus is used to obtain permanent axial deformation on the samples prepared with the same dry density at different water contents between 7% and 11% and at different fine contents of 4%, 7.5% and 15.3%. The results show the significant influence of water content and fine content on permanent axial deformation behaviour. The permanent axial deformation increases with the increase of water content while the influence of fine content depends on the water sensitivity of fine particles and their initial water contents. The modified empirical–analytical models are proposed for describing the evolution of permanent axial deformation based on the results in the single-stage test and the multi-stage tests. It takes into account the number of cycles, the stress level, the water content and the fine content of the granular material. Two approaches are used: one based on the water contents and fine contents and the other based on suction values. The approach based on suction values needs less number of parameters to describe permanent axial deformation compared with the approach based on the water contents and fine contents while the two approaches present more or less the same accuracy. The simulation results show a very good capacity of the proposed approaches. These findings reduce the number of tests required to predict permanent axial deformation.