Dynamic Uniaxial Compressive Behavior of Colorado Mason Sand Under High-Strain Rates

The compressive behavior under uniaxial strain of Colorado Mason sand, that contains primarily silica sand, at high strain rates was investigated on a 24.4-meter-long split Hopkinson pressure bar. A hardened carbon steel tube was used to provide passive confinement for the sand, along with two tungsten carbide rods capped at both ends for compression. To attain a desired bulk mass density for sand, the assembly was shaken in different directions randomly to consolidate the sand, and it was subsequently placed between the incident and transmission bars for dynamic compression. To determine the triaxial volumetric and deviatoric behavior, both unsorted dry sand and partially saturated sand specimens were compressed at high strain rates. The axial and circumferential responses of the cylindrical sand specimen were measured under stiff passive confinement. The effect of initial mass density was investigated, and the stress–strain relationships were also evaluated to determine whether a power-law relationship with mass density was followed. The effect of water content on the constitutive behavior was investigated, as well as the compressibility and energy absorption density as a function of the applied axial stress. For both intact and impacted sand, a Weibull distribution function was found appropriate to describe the sand size distribution. Further sand size distribution was analyzed for the three types of sand grains. The internal structures and fragments of sand were observed by X-ray micro-computed tomography, and the fracture/crushing mechanism was identified for the three types of sand grains. The experimentally-observed constitutive behavior of sand can be analyzed further in the future for constitutive modeling and mesoscale/macroscale simulations under high strain rate loading.