Engineers Australia

The dynamic behaviour of some fine-grained subgrade soils under traffic load

Bao Thach Nguyen and Abbas Mohajerani


The flexible pavement is a very important infrastructure asset which normally consists of asphalt or a sprayed seal surface layer and the underlying base and sub-base courses. The subgrade soil is the existing soils and is the foundation of the pavement. It can be said that the performance of the pavement significantly depends on the bearing capacity of the subgrade. Therefore, an understanding of the behaviour of the subgrade soils would increase the confidence of pavement engineers in the design. Under the moving traffic load the behaviour of the subgrade soils contains two parts: resilient and permanent deformation. In order to investigate this behaviour in the laboratory repeated load triaxial equipment is used. Due to the complicated, time-consuming and expensive procedure, it is a challenge to perform the repeated load triaxial test as a routine basic test. Previous studies have reported the significant influence of the subgrade soil properties and loading conditions on the resilient and permanent deformation. In the current paper, the resilient and permanent deformation behaviour of several fine-grained soils collected from various locations in Victoria, Australia were studied. The effect of subgrade soil physical properties and stress conditions on the resilient modulus and permanent deformation for the experimental soils are examined and discussed.