Modulus and Damping Due to Uniform and Variable Cyclic Loading

Laboratory tests are run on five different cohesionless soils to determine their modulus and damping characteristics. Torsional simple shear and resonant column tests are performed by the same test apparatus in order to compare results. Results indicate that the tests are interchangeable as long as there isn't a significant cycles effect. Number of loading cycles generally increases modulus in sands and decreases modulus in silts. Damping decreases with number of loading cycles for both silts and sands. Threshold strain levels are also studied with agreement between predicted and measured results. Ramberg-Osgood parameters, taken with uniform cyclic tests, are applied to irregular loading tests along with the Masing criterion. Predictions compare very favorably with test results.