AbstractThe resilient modulus of unstabilized granular base or subbase material is the fundamental and primary mechanical property adopted by empirical-mechanistic pavement design, and has been the focus of much research. However, the mechanical properties of unstabilized open-graded drainage layers, which also work structurally as a base or subbase, are not always considered in pavement design. Moreover, the specific gradations and high porosities even increase the difficulties in characterizing the unstabilized drainage layer materials. In this study, the typically used open-graded aggregates for Wisconsin’s drainage layer were tested in a laboratory for mechanical properties including resilient modulus and shear strength at 15 and 20% air void content. The resilient modulus parameters are modified from the literature and the mechanistic-empirical pavement design guide (MEPDG) model and were also obtained through nonlinear regression for level 1 inputs in MEPDG. The resilient modulus laboratory data, to...