Soil response analyses require that the soil strata involved be characterized in terms of their dynamic material properties. Two important material properties are the shear modulus and a measure of energy dissipation characteristics, usually expressed as the damping ratio. Both can be obtained from standard laboratory tests, most commonly resonant columns or cyclic triaxial devices which provide strain-dependent values. Alternative experimental procedures are now available to estimate shear moduli at very small strains from piezoelectric transducer tests (bender elements); procedures have also been put forth to obtain the energy dissipation properties from this test. In this paper, we present a modified version of the spectral-ratio method using the wavelet transform to measure the damping ratio at small strains from waveforms acquired from bender element tests. Synthetic bender element signals were first used to test the procedure and validate the approach. Then, we analyzed signals obtained from a large-size oedometer equipped with bender elements on very soft Texcoco Clays (near Mexico City), and the waveforms were propagated along different paths. Our results show that the range of values of Dmin obtained from bender element tests agrees well with those obtained from resonant column tests performed on very soft clayey soil specimens retrieved from the same area at different depths.

Alfonso Fernández-Lavín, Efraín Ovando-Shelley, Claudia Chamorro-Zurita,
Damping ratio on lacustrine soils using the wavelet transform,
Soil Dynamics and Earthquake Engineering,
Volume 180,
2024,