Three-Dimensional Scaled Memory Model for Gravelly Soils Subject to Cyclic Loading

Abstract

A comprehensive constitutive model has been formulated to capture the complex behaviors of gravelly soils under irregular cyclic loading. The application of this model aims to analyze the nonlinear deformation behavior of earth structures involving gravelly soils, such as rockfill dams and retaining walls subjected to earthquake loading. The proposed model is based on the basic framework of a two-mechanisms model structure (the first mechanism due to the deviatoric stress ratio increment drij, the second to effective mean pressure increment dp′). The distinctive feature of this model is that the concept of scaled memory is extended and incorporated into the plastic modulus and dilatancy, which are defined in three-dimensional stress space by the relative configuration of past stress reversal memory surfaces. The sizes of these memory surfaces are assumed to expand with cyclic accumulated volumetric strain. Consequently, the influence of any loading and unloading history on stress-strain behaviors can be determined for complex loading paths, particularly for irregular cyclic loading. Subsequently, the key assumption of the plastic flow direction under the dp′ mechanism is modified to better reflect the shear characteristic under complex cyclic loadings. The model is formulated in a general three-dimensional stress space, and the modeling of cyclic hysteresis, cyclic hardening and densification, and cyclic residual deformation of gravelly soils is verified through comparisons of the predicted behaviors and the known experimental results with various one-way and two-way cyclic loading paths. Finally, the cyclic loading history is determined to have a considerable impact on the calculated strain that should not be ignored.