Effects of particle size and moisture on the compressive behavior of dense Eglin sand under confinement at high strain rates

The dynamic compressive behavior of sorted and unsorted Eglin sand (Quikrete #1961 sand quarried in Pensacola, FL) under confinement was characterized under dry or moisture conditions at strain rates near 600 s−1 using a long split Hopkinson pressure bar, respectively. The as-received unsorted sand was sorted into grain sizes of 0.60 mm, 0.50 mm, 0.42 mm, 0.30 mm, 0.212 mm, 0.15 mm, 0.106 mm and 0.053 mm. For preparation of a partially saturated sand specimen sealed in a sand specimen assembly, water was introduced to reach moisture contents of 0%, 4.2%, 8.2%, 12.4%, 14.4% and 16.5%. A sand specimen assembly was used, and sand grains were confined inside a hollow cylinder of hardened steel and capped by cemented tungsten carbide rods. The assembly was subjected to repeat manual shaking and tapping to consolidate the sand to attain a given mass density; it was then sandwiched between incident and transmission bars for compression under a high strain rate. The volumetric and deviatoric behavior of dense Eglin sand was investigated on eight sorted sand specimens and at six moisture contents. After impact, the sand was analyzed to determine the particle size distribution, which was found to follow Weibull distribution rather than Gaussian distribution. The breakage factor was found to follow a linear relationship with moisture content. The effect of initial particle size and moisture on the volumetric and deviatoric behavior of sand was discussed. The compressibility was characterized in terms of void ratio as a function of axial pressure. The specific energy absorption and shear stress–hydrostatic pressure ationships were determined for different grain sizes and moisture contents.