Stiffness and Damping of Clean Quartz Sand with Various Grain-Size Distribution Curves

Approximately 240 resonant column (RC) tests have been performed on 26 clean quartz sands with piecewise linear, gap-graded, S-shaped, and other smoothly shaped grain-size distribution curves. For each material, the small-strain shear modulus, $G_{\text{max}}$, the shear modulus degradation curves, $G\left(\gamma \right)/G_{\max }$, and the damping ratio curves, $D\left(\gamma \right)$, were measured at different pressures and densities. The applicability of the extended empirical equations proposed by the authors in two previous publications, considering the influence of the uniformity coefficient, $C_u=d_{60}/d_{10}$, of the grain-size distribution curve, has been inspected for the various tested materials. These equations were developed originally based on RC test data for linear gradations. It is demonstrated that the extended empirical equations work well also for most of the more complicated grain-size distribution curves tested in the current study.