Theoretical Framework for Characterizing Strain-Dependent Dynamic Soil Properties

This paper proposes a theoretical framework for the characterization of the strain-dependent dynamic properties of soils. The analysis begins with an analytical constitutive model for soils under steady-state cyclic loading. The model describes the dominant soil characteristics, i.e., the hysteresis and nonlinearity with an intrinsic material property , which physically represents the degree of the hysteresis nonlinearity in a medium. Explicit formulas for the backbone curve, tangent shear modulus, secant shear modulus, and damping ratio as a function of shear strain are derived directly from the constitutive model. A procedure is then developed to determine the parameter in which the derived damping ratio equation is fitted to damping ratio data measured from the resonant column test (RCT). Clay and sand under three different levels of confinement stress are considered in the numerical evaluation. The capability of the proposed theoretical framework in predicting strain-dependent soil properties and responses is demonstrated.