Abstract
The subgrade layer, upon which the pavement is constructed, will have a large impact on structural design. The study aims at characterizing permanent deformation properties of cohesive subgrade materials including. A new testing procedure, stage loading, was used to test the permanent deformation of subgrade materials at different stress levels and load repetitions; this technique allows researchers to explore the effect of stress history on the accumulation of plastic deformation besides saving time, effort, and test specimens. The permanent deformation results showed a constant increasing rate of plastic strain at higher stress levels. The results obtained could be used to help engineers in characterizing the cohesive subgrade materials. Statistically, soil type and water content were found to be statistically significant at the 0.05 significance level, whereas, at the 0.1 significance level stress level, soil type and water content were found to be significant factors in affecting permanent stain.