Stress Ratio Effects on Shear Modulus of Dry Sands

Resonant column tests involving anisotropic confining conditions were conducted to evaluate static stress condition, especially stress ratio effects on the low‐amplitude dynamic shear modulus, $G_0\text{,}$ of three clean, dry sands. Six static stress paths, involving both triaxial compression and triaxial extension, developed the desired ranges of stress ratios and stress histories. The results of these tests determined that increasing the stress ratio decreased $G_0\text{,}$ up to 20%–30%, but the reduction was not significant for stress ratios below about 2.0. Stress history caused a reduction in $G_0\text{,}$ but when the final stress ratio was the maximum value attained, the loading, unloading, and reloading path followed to develop this maximum value had little influence. The results also indicated that $G_0\text{,}$ depends about equally on the static principal stresses in the direction of wave propagation and in the direction of particle motion. The effect of the third principal stress appears to be unimportant. Two empirical equations were given for $G_0\text{,}$ in term of the two significant principal stresses.