Development of Resilient Modulus Prediction Model for Granular and Noncohesive Soils of New Mexico

The resilient modulus (M_R) of unbound materials, i.e., base and subgrade, is an essential property for the Mechanistic-Empirical Pavement Design Guide (MEPDG). The M_R of the unbound materials is highly dependent upon several factors such as physical properties of the materials, soil type, stress state, and moisture content. The M_R values are usually determined by conducting repeated load triaxial compression tests in the laboratory. However, because of the complexity, difficulty, huge time, and effort associated with it, development of an M_R prediction model based on soil physical properties has increasingly become an imperative. In this study, a model is developed to estimate the M_R of base and noncohesive (A-2-4) subgrade soils that are commonly available in the state of New Mexico from a set of materials’ physical properties. First, subgrade and granular materials have been collected from different construction sites, and a laboratory M_R test is conducted in accordance with the test standard AASHTO T-307, Standard Method of Test for Determining the Resilient Modulus of Soils and Aggregate Materials. The pertinent material constants (k₁, k₂, and k₃) in the constitutive model have been evaluated from the laboratory test data using regression analysis. Materials coefficients are correlated to the selected physical properties. A new set of laboratory test results for another pavement site is used to verify the model. It is observed that the prediction model predicts M_R values that agree well with the laboratory results. Therefore, the proposed model can be applied to the base and noncohesive subgrade soils for implementation in MEPDG.