The resonant column device in the Graduate Soils Laboratory is known as a Drnevich Long-Tor Resonant Column Apparatus. The term Long-Tor denotes the capability of the apparatus to vibrate specimens in either a longitudinal or torsional mode of vibration.
   The basic principle of the resonant column device is to excite one end of a confined cylindrical soil specimen in a fundamental mode of vibration by means of torsional or longitudinal excitation. Once the fundamental mode of resonance frequency is established, measurements are made of the resonance frequency and amplitude of vibration from which wave propagation velocities and strain amplitudes are calculated using the theory of elasticity.
   The Resonant Column Test provides laboratory values of dynamic moduli and damping ratio.