Unbound materials resilient modulus testing for Truckee Meadows area

The recent development of Mechanistic-Empirical Pavement Design Guide (MEPDG) requires the resilient modulus (MR) characterization of subgrade materials. Currently Nevada Department of Transportation (NDOT) uses an empirical chart that provides a correlation between resilient modulus and R-value to estimate MR. The Regional Transportation Commission (RTC) of Washoe County also uses a similar procedure. As NDOT attempts to implement the new MEPDG guidelines to design pavements, procedures to evaluate MR of unbound material, which is expressed as a function of stresses, need to be established. This requires the laboratory testing of unbound materials for the resilient modulus under variety of stress conditions.;This research evaluated the testing facility of unbound material at the Western Regional Superpave Center (WRSC) at the University of Nevada, Reno (UNR). Unbound materials were sampled at four different locations from a local project in Reno, Nevada. The subgrade samples were characterized in the laboratory in terms of resilient modulus. The soil classification tests and compaction tests were conducted as the initial steps towards the characterization of subgrade materials. The Resilient modulus tests for the unbound materials were conducted in the repeated load triaxial test according to AASHTO T307-99 (2003) testing procedure. The test results were analyzed using statistical techniques to develop an optimum constitutive model and it was found that the model recommended in MEPDG showed the best fit and regression coefficient.;Additionally, mechanistic analyses results were used to evaluate the resilient modulus values of each type of subgrade. These values were later compared with values from different simplified approaches. Also the load induced stress distributions in the pavement layers with different resilient modulus values have also been compared.