Evaluation of Subgrade Resilient Modulus Predictive Model for Use in Mechanistic–Empirical Pavement Design Guide

The characterization of unbound materials in the mechanistic–empirical pavement design guide (MEPDG), also known as the 2002 design guide, is reviewed, and this characterization is applied to Minnesota subgrades. The main emphasis is on the collection of k₁-, k₂-, and k₃-parameters for Minnesota fine-grained soils and the procedure for the interpretation of the resilient modulus test to provide an input to the multilayer elastic theory (MLET) analysis (Level 2 input). This is an important aspect of adaptation of the MEPDG, because the guide recommends measurement of resilient moduli from laboratory testing, but the procedure does not specify how to interpret the test data to obtain an input for an MLET analysis. The resilient modulus test results from 23 samples collected from several Minnesota locations were used to provide information for the nonlinear finite element program and multilayer elastic theory program. The obtained elastic moduli were compared with the MEPDG recommended ranges for subgrade modulus of elasticity based on the soil classification (Level 3 inputs). The MEPDG Level 3 ranges were found to be reasonable.