High intensity compressive stress wave propagation through unsaturated sands

Abstract

High amplitude split-Hopkinson pressure bar laboratory tests were performed on confined specimens of 20-30 Ottawa and Eglin sands. Triaxial confining stresses of zero and 310 kPa were used, and the samples were subjected to a constant incident stress. Samples were compacted dry, then saturated, then desaturated by use of the pressure plate method. For saturation levels increasing from zero to 80 percent, the compressive wave velocity and stress transmission ratio values decreased slightly for both confining stresses. Quasi-static constrained modulus was found to vary in a similar manner. Previous researchers have shown that for specimens compacted moist, the values of wave velocity, stress transmission ratio and quasi-static constrained modulus increase as the saturation level increases from zero to approximately 30 percent, and then decreases with any further increase in saturation. Several specimens were compacted moist in this research and the results show similar trends. The difference in trends is directly related to the moisture content of the sand during compaction.