Characterization of Permanent Deformation Behavior of Silty Sand Subgrade Soil Under Repeated Load Triaxial Tests

The performance of pavement structures is highly dependent on the performance of the subgrade layer, because it is the last layer underlying all the other pavement layers. The development of permanent deformation in subgrade material under traffic loads can cause pavement distresses such as fatigue cracking and rutting. This paper presents an evaluation of permanent deformation behavior of a silty sand subgrade material in the laboratory at various stress ratios and stress levels. It was found that the shakedown behavior of the material fell within plastic shakedown and plastic creep for stress ratios below 1.0 and a stress ratio of 1.5, respectively. A statistical prediction model for permanent deformation based on the test results is suggested.