Abstract: This paper describes the dynamic properties and Poisson's ratio of silty clay, aiming at the nonlinear characteristics of Poisson's ratio under low amplitude strain. A series of resonant column tests was conducted in torsional mode and flexural mode to determine the shear modulus G, elastic modulus E and Poisson's ratio ν. The results show that both E and G decrease with increasing strain, but not synchronously. The reduction of G precedes that of E with increasing strain. And Poisson's ratio ν decreases with the increase of confining pressure, and increases with increasing shear strain. In addition, an empirical model is proposed to describe the linear relationship between ν and in the semi-logarithmic scale, and to predict Poisson’s ratio. Theoretical analysis proves the inevitability of this linear relationship between ν and in small strain level. And with the increase of shear strain (or decreasing ), the ν- curve develops from linear phase to nonlinear regime, and finally approaches to a constant value. Moreover, the relationship between the fitting parameters and the constants of Hardin-Drnevich model is established. The fitting parameters obtained from linear phase can be used for the estimation of the Poisson's ratio in nonlinear phase through this relationship. The case study demonstrates that this method provides good results and has practical value.

Key words: Poisson's ratio, elastic modulus, shear modulus, damping ratio, silty clay, resonant column test