The resilient response of fine-grained Tennessee subgrade soils

The resilient modulus is a relatively new material property that characterizes subgrade soil performance in a pavement system. The resilient modulus test procedure allows the measurement of resilient subgrade deflection by simulating in-situ traffic loadings. The magnitude of resilient subgrade deflection has been found to be a good indicator of pavement performance and inclusion of the resilient modulus in pavement design procedures should contribute to extended pavement life and decrease instances of mandatory pavement rehabilitation. An investigation of the resilient modulus of seven fine-grained subgrade soils from across the state of Tennessee was conducted. Standard laboratory tests were performed to determine the index properties of each soil. Cyclic load triaxial tests were conducted at various water contents and dry densities in order to determine the effects of these parameters on the resilient response. The magnitude of applied confining pressure and deviator stress was also varied during testing to simulate variations in depth and lateral location from the applied wheel load. The specimen water content and the magnitude of applied deviator stress were found to significantly affect the resilient response of most of the soils tested. The effect of variations in the applied confining pressure on the resilient modulus was minimal. Variations in the specimen dry density affected only a few of the test specimens. The data collected from all the laboratory tests for each soil were compiled in the form of a "Design Handbook" to be used by the Tennessee Department of Transportation for estimation of the resilient characteristics of future highway project subgrade soils.