Effects of Vibration Cycles on Shear Modulus and Damping of Sand Using Resonant Column Tests

Resonant column tests, corresponding to a given input voltage of the drive mechanism, were conducted in torsional mode to examine the effect of vibration cycles on shear modulus (G) and damping (D) of dry sand with shear strain amplitude in a range of 0.0005-0.05%. Two different relative densities, approximately 61 and 85%, and effective confining pressures, 300 and 500kPa, were used. The specimens were subjected to a number of vibration cycles ranging from 1,000 to 50,000. The shear modulus and damping ratio, before and after the application of vibration cycles, were determined for several input voltages. An induction of the vibration cycles leads to a continuous increase in shear strain, which causes (1)a decrease in the shear modulus and (2)an increase in the damping ratio. This effect becomes especially more prominent for lower values of relative densities and confining pressures. The modulus reduction and damping curves remained the same after applying vibration cycles.