Viscoelastic Response of a Cohesive Soil in the Frequency Domain

Energy storage and energy dissipation characteristics of a cohesive soil are studied in the frequency domain using strain-controlled vibratory uniaxial compression tests. Such characteristics are important considerations in earthquake phenomena, machine foundation design, and soil-structure interaction under dynamic loading. The soil response is expressed in terms of the storage, loss, and complex moduli as well as the loss tangent. Dynamic stress-strain amplitude response is nonlinear even at small values of dynamic strain. Storage, loss, and complex moduli decrease with increased dynamic strain amplitude. The energy dissipation expressed in terms of the loss tangent decreases with increases in moisture content, frequency, and dynamic strain amplitude. Loss tangent values determined by the direct method are compared with those obtained by transformation of stress relaxation test data. Effects of concentration (moisture content) are presented in terms of a non-dimensional dynamic stress-strength parameter using the ultimate compressive strength in uniaxial compression as a consistency index. Static stress level about which the dynamic perturbations take place has no apparent effect on the dynamic stress-strain response for the range studied.