Resonant Column Test is a laboratory test used to determine the shear elastic modulus and damping properties of soils. In this method, a cylindrical soil specimen is confined between ends. The bottom end is often fixed and the top end is capable of exciting the specimen by torsional or longitudinal vibration ans also of measuring the soil response. The vibration is applied using an electromagnetic drive system with variable frequency.

The test starts by vibrating the cylindrical soil specimen at the top end while the sample is restrained at the bottom. The frequency of vibration is gradually increased until reaching the first-mode fundamental  frequency of the sample. At this frequency, measurements are made of the resonance frequency, amplitude of vibration. knowing the geometry and the end constraints of the sample, the measured resonance frequency is then used to calculate the wave propagation velocity using the wave propagation equation and the theory of elasticity. The shear modulus is then obtained directly from the derived velocity and the density of the
sample:

G=ρ(v_s)^2

The resonant column test provides a useful tool for evaluating the strain-dependent modulus and damping properties of soils at small strains. The method is based on an indirect measurement of soil properties; therefore, additional calibrations might be necessary in order to account for the testing condition and to achieve reliable results. The resonant column test is commonly used in geotechnical engineering practice and the testing equipments are commercially available.