Assessment of Cary and Zapata Suction Based Model for Prediction of Resilient Modulus in Fine Grained Subgrade Soils

Stiffness of pavement subgrade materials that is commonly determined by the resilient modulus parameter is an important component in the mechanistic design of flexible pavement structures. The universal model, which makes use of the bulk and octahedral stresses as predicting parameters, is used to predict the soil resilient modulus in the MEPDG design. Recent studies performed by Cary and Zapata (2011) lead to the development of a model that incorporates the soil matric suction as one of the fundamental stress state predictors. This model requires the measurement of change in suction during the loading process, which makes it difficult for implementation. In order to overcome the difficulties involved and aid in the implementation of the Cary and Zapata's (2011) resilient modulus model, a laboratory study using two fine grained materials was accomplished to assess changes in suction parameter of different unsaturated soil materials during cyclic loading. Based on the results obtained, recommendations for implementation of the model are presented.