Subgrade resilient modulus prediction models for coarse and fine-grained soils based on long-term pavement performance data

Resilient modulus (M R) of subgrade soils is the elastic modulus based on the recoverable strain under repeated loads and depends on several factors such as soil properties, soil type and stress states. This paper presents the prediction equations to estimate M R from a set of soil physical properties for the unified soil classification system soil types namely coarse-grained and fine-grained subgrade soils. Data extracted from long-term pavement performance information management system database for 259 test specimens of reconstituted soil samples from 19 states in New England and nearby regions in the USA and two provinces in Canada were used in this study. Generalised constitutive model consisting bulk stress and octahedral shear stress was used to predict the M R of subgrade soils by developing equations for the regression coefficients (k-coefficients) in the constitutive model that relates them to various soil properties. Prediction models were developed by conducting multiple linear regression analysis using computer software SAS®. To verify the prediction models, a set of fresh laboratory M R tests were conducted on representative New England subgrade soils using AASHTO standards. The laboratory test results show that the developed models predict M R values fairly well for the soils with their properties values within the range used in developing the prediction models.