Influence of Post Compaction on the Moisture Sensitive Resilient Modulus of Unbound Granular Materials

The impact of moisture on the resilient modulus (M-R) of unbound granular materials (UGMs) was investigated based on repeated load triaxial (RLT) tests and considering the effect of post compaction (PC) from cyclic loading. Results showed that although M-R decreases with increased moisture, it may appear to increase with increased moisture if the PC process is aided by moisture for a relatively large number of load applications. When limited PC was involved, the parameter k(1) of the k-theta model decreased with increased moisture while the parameter k(2) was unaffected. On the other hand, when significant amount of PC took place, k(2) increased with increased moisture. The mechanistic-empirical pavement design guide (MEPDG) model worked well to capture the influence of moisture on the stiffness when M-R decreased with increased moisture. However, it did not work when M-R increased with increased moisture due to the PC effect. On the other hand, an alternative approach expressing k(1) and k(2) as functions of moisture worked well for both situations. Generally, this study suggested that the effect of PC should be considered in modelling the impact of moisture on M-R for better accuracy.