Effects of seismic vibration on small strain shear modulus of saturated silt

The small strain shear modulus is one of the most important parameters reflecting soil structure.It is primarily a function of the effective confining stress and void ratio(density),while the dynamic loading history is another important factor.Many experiments have been conducted to investigate the small strain shear modulus of dry sands due to prestraining with prestrain amplitude below 10-3,though the results for the effects on those of saturated soils subjected to a higher amplitude dynamic loading are limited and somewhat contradictory.An attempt is made to study the influence of seismic vibration on the small strain shear modulus of the saturated silt specimens with different relative densities.The shear wave velocity of the specimens are monitored with bender elements equipped on the dynamic triaxial apparatus as soon as the undrained cyclic triaxial testing is interrupted.To ensure the credibility,the reach points of shear wave velocity are examined through the comparison of resonant column tests.The effects of interrupting time at different pore pressure developing stages are also evaluated.It can be observed in the tests that under large amplitude cyclic loading cycles,the small strain shear modulus has a dissimilar degradation or increament changes compared with that under the same static stress without cyclic loading history.This is attributed to the changes in soil microstructure during cyclic loading.The variation modes for the small strain shear modulus are initial specimen condition and cyclic amplitude dependant,decided by the soil particle contact behaviour.