Importance of strain level in evaluating resilient modulus of granular materials

This paper examines the importance of strain level, in addition to stresses, in evaluating the resilient modulus of unbound granular base/subbase materials used for pavement construction. A series of cyclic triaxial resilient modulus testing on selected granular materials were carried out following different loading schemes with both the applied stresses and resilient strain levels being adjusted. The experimental results clearly showed that the resilient modulus may not be uniquely determined from the bulk stress and the total deviator stress, particularly when the actual stress states were different from those in standard resilient modulus testing. Variation of resilient modulus with strain level can be described by a hyperbolic function, whereas the stress level dependence of resilient modulus can still be reasonably estimated by either Uzan's universal model or that recommended in NCHRP 1-37A.