Characteristics of small-strain shear modulus of Zhanjiang clay under influence of inherent anisotropy

In order to investigate the influence of inherent anisotropy on the small-strain shear modulus of Zhanjiang clay, a series of resonance column tests are carried out on the specimens with α=0°, 22.5°, 45°, 67.5°, and 90° under different confining pressures. The tests results indicate that the ratio of the maximum dynamic shear modulus normalized by the void ratio function G_max/F(e) of the specimens with different α to G_max/F(e) of the specimen with 90° (i.e., K_α) decreases with the increasing α under the same confining pressure. When the confining pressure is lower than or higher than the yield stress σ_k, K_α keeps basically constant or obviously decreases with the increasing confining pressure for the specimen with the same α. When the confining pressure is lower than σ_k, the increase of the confining pressure hardly affects the influence of the inherent anisotropy on G_max. When the confining pressure is higher than σ_k, the increase of the confining pressure weakens the influence of inherent anisotropy on G_max. As the confining pressure increases, G_max/F(e) of specimens in different directions shows the law of first increasing and then decreasing, and a turning point occurs when the confining pressure is around σ_k. Based on the variation law of G_max/F(e) of specimens in different directions with confining pressure, a characterization method of evolution law of G_max considering the inherent anisotropy is proposed.