Effect of confining pressure and degree of saturation on damping ratios of sand

Dynamic properties of soil specimen usually refer to both stiffness and damping ratio. However, more attention has focused on stiffness rather than damping ratio. Damping ratio is normally determined in the laboratory using resonant column tests, cyclic triaxial or cyclic shear tests. Recently, laboratory determination of damping ratio for soil using bender using spectral ratio method elements has been reported. The objective of this study is to evaluate the effects of confining pressure and degree of saturation on the damping ratios of sand using bender/extender elements. Besides the spectral ratio method, the logarithmic decrement method, used in resonant column tests, was also employed for the determination of damping ratio. The scope of the study includes S wave damping ratios and the effect of confining pressure. The logarithmic decrement method can only be applied to soil specimens at high confining pressure. The damping ratio determined by the logarithmic decrement method was generally higher than that by the spectral ratio method. Damping ratio was shown not to vary significantly with confining pressure and saturation.