At the beginning of 2009, INDOT adopted the Mechanistic-Empirical Pavement Design Guide (MEPDG) method to study the tong-term pavement performance. The implementation of this new design approach led to difficulties for the pavement to pass the INDOT performance criteria; in particular pavement roughness (IRI) when A-6 or A-7-6 soils were considered as subgrade. This study focuses on investigating the influence of the soil input parameters in the Enhanced Integrated Climatic Model (EICM) on the prediction of the soil resilient modulus (MR) in the MEPDG. A total of four sites located around the state of Indiana are used to propose/validate the observations and conclusions made in the research.

The study shows that (1) for the climatic conditions existing in Indiana, the location of the water table does not affect the value that the MEPDG uses for the subgrade MR; (2) the gravimetric water content is the most influential parameter on the EICM since it is directly related to the optimum degree of saturation of the subgrade; and (3) For A-7-6 soils, the overall deformation of the pavement structure is controlled by the subgrade (~80% of total deformation).

In order to properly model the pavement structure, the MR input into the MEPDG for the subgrade should represent the optimum condition. This value will then be reduced within the EICM to reflect actual site conditions; and the MR input into the MEPDG for the treated layer should be a constant (i.e. not affected by EICM) and with PI and P200 values that are representative of the soil after treatment, given that the fines content and plasticity of a chemically-treated soil tend to decrease with treatment.

Report Number



resilient modulus, subgrade, MEPDG, EICM, SWCC, fine-grained soil, long-term pavement performance

SPR Number


Performing Organization

Joint Transportation Research Program

Publisher Place

West Lafayette, Indiana

Date of this Version