The impact of moisture on the permanent deformation (PD) behavior of unbound granular materials (UGMs) was investigated based on multistage (MS) repeated load triaxial (RLT) tests. Two UGMs with different particle size distributions were tested for a range of moisture contents and the accumulation of permanent strains for the different moisture contents were modelled using a simple predictive model.

Moisture was found to increase the accumulation of PD in the materials. Analyses of the variation of the parameters of the model with respect to moisture showed that it is possible to capture the moisture dependent PD behavior of the materials assuming a simple linear relationship between one of the parameters of the model and the moisture content.