Influence of post compaction on the moisture sensitive resilient modulus of unbound granular materials

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The impact of moisture on the resilient modulus (MR) 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 MR 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 k1 of the k-θ model decreased with increased moisture while the parameter k2 was unaffected. On the other hand, when significant amount of PC took place, k2 increased with increased moisture.

The mechanistic-empirical pavement design guide (MEPDG) model worked well to capture the influence of moisture on the stiffness when MR decreased with increased moisture. However, it did not work when MR increased with increased moisture due to the PC effect. On the other hand, an alternative approach expressing k1 and k2 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 MR for better accuracy.

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