Effect of State of Stress on Velocity of Low-Amplitude Shear Waves Propagating along Principal Stress Directions in Dry Sand

摘要

The effect of state of stress on shear wave velocity was examined for shear waves propagated as body waves through a sand mass. Testing was performed in a triaxial device, which was designed to hold a cubic soil sample measuring 7 ft (2.1 m) on a side and which was used to apply an isotropic, biaxial or triaxial state of stress of the sample. The triaxial device is essentially a steel box, constructed of reinforced steel, which uses rubber membranes to apply a confining pressure along each of the principal axes of the cube. Dry sand was placed in the cube for this initial testing program. Shear waves were propagated along the principal axes of the cube over the pressure range from 10 to 40 psi (68.9 to 276 kPa). Shear wave particle motion was monitored by three-dimensional accelerometers embedded in the sand. Stress cells and strain sensors were also embedded in the sand mass to examine stress-strain properties of the sand for the applied loading. All wave testing was performed at low-amplitude strains and at wave frequencies less than 2400 Hz. Therefore, it was assumed that the shear modulus was rate independent in this study.