Influence of Degree of Saturation on the Small Strain Shear Modulus of a Silty Clay

This paper presents an experimental study of the influence of degree of saturation on the maximum shear modulus G(max) for silty clay. A series of resonant column tests has been performed on undisturbed samples with different saturations, void ratios, and confining pressures. It is demonstrated that G(max) decreases with increasing void ratio and increases almost linearly with increasing confining pressure in semi-logarithmic coordinate. On the other hand, with decreasing degree of saturation S-r, G(max) increases slightly at high saturation level (S-r>70%), and increases significantly at low saturation level (S-r<70%). Based on the resonant column tests, correlations of the constants of Hardin's equation with degree of saturation S-r have been developed. The predictions by the proposed equation showed good agreements with the experimental data in the literature. An application of this equation to the in-situ conditions was also provided and compared with G(max)-data from in-situ wave velocity test. The results show that the disparity between the in-situ and laboratory test could be significantly reduced when moisture condition is considered using the proposed equation.