High-Strain Rate Compressive Behavior of Glass Beads Under Confinement

Glass beads are often used to examine simulation models for granular materials. The dynamic behavior of glass beads, however, has not been characterized accurately. In this paper, the dynamic behavior is characterized at high strain rates. To describe the beads used in these experiments, the size distribution was measured, and the bead-level mechanical properties were determined by nanoindentation. The dynamic compressive behavior of glass beads under confinement was characterized at strain rates near 400 s⁻¹ using a long split Hopkinson pressure bar. The glass beads were confined inside a hollow cylinder of hardened steel and capped by cemented tungsten carbide cylindrical rods. The assembly was subjected to repeated shaking and tapping to consolidate the glass beads to attain a given bulk mass density. Experiments were conducted on dry unsorted beads at three initial mass densities (1.46, 1.54 and 1.61 g/cm³), sorted beads at three sizes (0.30, 0.212, and 0.106 mm), and partially saturated beads with average bead size of 0.212 mm at five water contents (0, 7, 14, 18 and 22 % by weight). Effect of initial mass density, bead size and water content on the dynamic volumetric and deviatoric response was investigated. The impacted beads were sorted for analysis of the particle size distribution. The compressibility was characterized in terms of the void ratio as a function of the axial pressure.