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Dynamic Soil Properties
Published in Swami Saran, Dynamics of Soils and Their Engineering Applications, 2021
The resonant column test is used to obtain the elastic modulus E, shear modulus G and damping characteristics of soils at low strain amplitudes. This test is based on the theory of wave propagation in prismatic rods (Richart, Hall and Woods, 1970). Either a cyclically varying axial load or torsional load is applied to one end of the prismatic or cylindrical specimen of soil. This in turn will propagate either a compression wave or a shear wave in the specimen. In this technique the excitation frequency generating the wave is adjusted until the specimen experiences resonance. The value of the resonant frequency is used in getting the value of E and G depending on the type of the excitation (axial or torsional).
Ground characterisation
Published in Harry G. Poulos, Tall Building Foundation Design, 2017
The resonant column test is commonly used for laboratory measurement of the low-strain properties of soils. It subjects solid or hollow cylindrical specimens to torsional or axial loading by an electromagnetic loading system, usually harmonic loads for which frequency and amplitude can be controlled. It can be used to measure the small-strain shear modulus and damping ratio of a soil or rock sample, and the variation of modulus and damping ratio with increasing shear strain level. Such data are valuable for carrying out dynamic response analyses of the foundation system.
Seismic response evaluation of structures on improved liquefiable soil
Published in European Journal of Environmental and Civil Engineering, 2021
Ayman Abd-Elhamed, Sayed Mahmoud
Soils’ characteristics subjected to dynamic and cyclic loadings are highly nonlinear and strongly controlled by the mechanical properties of the soil. This is clearly observed in the shear modulus and damping ratio that vary significantly with the shear strain amplitude. Both shear modulus and damping characteristics are key parameters in evaluating the dynamic responses of soil at different sites under earthquake loading (see Figure 2). With respect to the case where the soil behaviour lies within the region with a very low small strain, the estimation of maximum shear modulus, Gmax, is extensively investigated in the areas of soil dynamics. Values of Gmax are measured from seismic tests in the field. Alternatively, laboratory tests including resonant column tests also provide values of Gmax. The resonant column test is a useful tool for evaluating the laboratory values of soil stiffness and damping ratio at very low strains ranging from 0.00001 to 1%. The test measures the response of a cylindrical soil specimen confined between ends subjected to forced harmonic torsional or longitudinal vibrations (Viggiani & Atkinson, 1995). The density ρ and shear velocity Vs is used to estimate the shear modulus Gmax at very low strain employing the correlation (Richart & Whitman, 1967):
Dynamic properties of soils at low strains in Roorkee region using resonant column tests
Published in International Journal of Geotechnical Engineering, 2019
The resonant column test is the most commonly used laboratory test for measuring the low-strain dynamic properties of soils. The basic principle of the resonant column test is to vibrate a cylindrical soil specimen in a fundamental mode of vibration, in torsion or flexure. Once the fundamental mode is established, measurements of resonant frequency and amplitude of vibration are made. In the present research, a computerised resonant column apparatus was used. The complete RCA system used in tests is shown in Figure 1. Determination of shear modulus (G) and damping ratio (ξ) are discussed in following sections.