Cyclic Hysteretic Behavior and Development of the Secant Shear Modulus of Sand under Drained and Undrained Conditions

Abstract

The secant shear modulus is an important parameter in several geotechnical engineering models and calculation approaches. The characteristics of this parameter are very complex due to the hysteretic behavior of cyclically loaded soils. Its characteristics primarily depend on the mean effective confining stress and the void ratio. In this paper, the characteristics of the secant shear modulus of sand under large shear strain amplitude are investigated in detail based on the results of several cyclic triaxial and simple shear tests under drained and undrained conditions. The evaluation of the secant shear modulus based on the shape of the open stress–strain hysteresis loop is then discussed. Under certain loading conditions, the secant shear modulus defined from the reloading and unloading branches of the loop obviously differ. The evolution of the stiffness index, which measures the change in the secant shear modulus due to cyclic loading, shows that the drainage conditions play an essential role in the behavior of the secant shear modulus.