Damping Response of Cohesive Soils from Thermo-Controlled Resonant Column Testing

Most geotechnical engineering problems involving cyclic loading require measurement of dynamic soil properties, that is, shear modulus and damping ratio. Measuring the damping ratio is a quantitative approach to incorporating energy dissipation or attenuation of waves propagating through a soil mass by induced cyclic excitation. The importance of the damping ratio is primarily appreciated in ground response analysis in earthquake engineering and soil-structure interaction analysis under seismic or cyclic loading in structural and geotechnical engineering. The damping ratio, attributed to the energy loss in a soil mass under cyclic loadings, such as that generated by earthquake activity, can be calculated based on laboratory tests such as resonant columns and cyclic simple shear devices. Measuring damping ratios in the laboratory allows the investigation of the effect of boundary conditions, such as temperature, on the damping ratio of the soil. The impact of various parameters, such as the plasticity index, stress history, confining pressure, strain amplitude, device effect, and soil sampling, on the dynamic parameters of soil has been addressed in the literature. However, the impact of rising temperature, a growing concern in geotechnical and structural engineering, requires far more investigation and constitutes the main motivation for the present work. Thermo-controlled resonant column (RC) tests were performed on three cohesive soil samples with different moisture contents. The damping ratios were calculated using the half-power bandwidth (HPBW) and the free-vibration logarithmic decay curve (LDC) methods. Regardless of the measurement method, the damping ratio values are expected to be identical; however, obtaining a unique damping ratio for the test soils is challenging experimentally. The results showed how changes in the water content could affect the attenuation of the energy in the cohesive materials under thermo-cyclic loadings.