Estimation of Resilient Modulus of Subgrade Soils for Design of Pavement Structures

Field and laboratory testing programs were conducted to develop an efficient methodology for estimating resilient modulus (M-r) values of subgrade soils for use in the design of pavement structures. The field testing program consisted of obtaining Shelby tube samples of subgrade soils from different pavement projects throughout Louisiana. The laboratory program included conducting repeated load triaxial M-r tests as well as physical property tests on the collected samples. The validity of the correlation equations developed by the long-term pavement performance (LTPP) to predict the M-r was examined. In general, the LTPP model underestimated the values of M-r coefficients obtained in this study. A comprehensive regression analysis was conducted to develop models that predict the M-r coefficients of different subgrade soils in Louisiana using different physical properties. A good agreement was observed between the measured and predicted M-r coefficient values. Furthermore, the developed models had a better prediction of measured M-r coefficient values than the LTTP models. Finally, a catalog of resilient modulus of subgrade soils at different moisture content levels was developed.