Stress Ratio Effects on Shear Modulus of Dry Sands

TLDR

Resonant column tests were conducted to evaluate how stress ratio affects the low‑amplitude dynamic shear modulus, G0, of three clean, dry sands under anisotropic confining conditions. The study used six static stress paths (triaxial compression and extension) to generate a range of stress ratios and histories, and derived two empirical equations relating G0 to the two significant principal stresses. G0 decreases by 20–30 % with higher stress ratios, but this effect is negligible below a ratio of ~2.0; stress history also reduces G0, yet the path to reach the maximum ratio has little influence; G0 depends equally on the principal stresses aligned with wave propagation and particle motion, while the third principal stress is insignificant.

Abstract

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, G0, 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 G0, up to 20%–30%, but the reduction was not significant for stress ratios below about 2.0. Stress history caused a reduction in G0, 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 G0, 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 G0, in term of the two significant principal stresses.