A RHEOLOGIC INVESTIGATION OF THE DYNAMIC RESPONSE SPECTRA OF SOILS. REPORT 3. ENERGY DISSIPATION RESPONSE OF A COHESIVE SOIL,
NORTHWESTERN UNIV EVANSTON ILL TECHNOLOGICAL INST
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The results of an investigation of the energy storage and energy dissipation properties of a cohesive soil are presented. Major emphasis is directed at energy dissipation as well as phenomena associated with energy dissipation. Soil response is represented in terms of viscoelastic parameters. Both direct and indirect methods of determining energy dissipations are considered. Damping capacity as a function of frequency is determined directly by measuring the phase angle, delta, between applied and resulting waveforms in uniaxial unconfined compression with controlled sinusoidal vibration. The results are given in terms of the loss tangent, tan, delta. The loss tangent is dependent on moisture content, frequency, and amplitude of dynamic stress-strain but specimen geometry and static stress level, within the range considered seem to have no definite effect on the results. The experimental response is definitely nonlinear. Energy dissipation is also obtained by indirect methods through the application of Fourier transformation techniques to experimental data obtained from creep and stress relaxation tests. The loss tangent relations obtained using the Fourier Transforms are comparable to those obtained by the direct stress-strain-phase angle method.