Cohesionless Soil Behavior Under Random Excitation Conditions

Abstract

Little is known about the behavior of soil when subjected to random loading. A testing program was undertaken in which dry sand at different confining pressures was tested in a resonant column device using random torsional excitation in addition to conventional sinusoidal loading. The concept of the root‐mean‐square (rms) strain, as well as the use of the extreme value theory to determine the peak shearing strain under random excitation, is presented. The damping and shear modulus from random loading were determined by the autocorrelation function and the power spectral density function. By measuring and analyzing both the input excitation and the output response, the transfer function method was used for the first time in soil testing. Evaluation of the dynamic soil properties for sinusoidal vibration followed conventional procedures. The results indicate that during random loading, the damping values are higher and the shear moduli lower than the values obtained from sinusoidal loading at the same rms strain. Formulas were developed to correct the damping and shear moduli obtained from routine sinusoidal testing so that the values are more representative of actual field conditions.