High-Strain Rate Compressive Behavior of a “Natural Soil” Under Uniaxial Strain State

Abstract

Dynamic compressive behavior of a synthetic “natural soil” was investigated on an 85-ft split Hopkinson pressure bar. The “natural soil” was prepared by mixing a sorted dry clay and assorted dry Mason sand. The as-received moist clay (obtained from Boulder, Colorado) was first pulverized into powders, which were subsequently dried in oven at 105 °C for 2 days. The as-received Colorado Mason sand was dried under the same conditions. Then the clay was sieved to powers with dimensions smaller than #50 (0.3 mm) using ASTM E-11 standard sieves. The “natural soil” was obtained by mixing at different ratios of clay and sand at 5:100, 10:100, 20:100, 100:100 weight ratios. The mixed soil was capped inside a hardened steel tube, by two tungsten carbide rods at both ends in contact with the bars. This assembly was subjected to repetitive shaking to consolidate the soil to attain a desired bulk mass density; it was then placed between the incident steel bar and the transmission bar for dynamic compression. Through measurements of both axial and transverse responses of the cylindrical soil sample under confinement, both volumetric and deviatoric responses were determined. Both dry and water-saturated soil samples were characterized at high strain rates. The effects of different mixed ratio of clay/sand, and the water-saturation on the compressive behavior were investigated. The compressibility as a function of axial stress was determined. These results are compared with pure clay and sand samples.