Time Effects on Dynamic Shear Modulus of Clays

A Hardin oscillator was used to apply a steady-state, torsional vibratory load to remolded specimens of kaolinite and calcium bentonite inside a triaxial chamber and under an isotropic consolidation pressure. The principles of the resonant column test were used to determine the dynamic shear modulus. After completion of primary consolidation, the response was studied as a function of time for both drained and undrained conditions. Regression analyses were performed on these data and relationships are presented which show the effects that void ratio, effective stress, and time have on the dynamic response of these two clays. The shear modulus was shown to increase with increasing pressure, decreasing void ratio and time for both materials. This increase was approximately 10% of kaolinite and 40% for bentonite per logarithmic cycle of time after completion of primary consolidation for constant effective stress.