Modeling of load reversals at very small strains in anisotropic soil with multilaminate constitutive models

Although noticed very early in laboratory soil testing, anisotropic soil behavior at the small strain level is rarely taken into account in the analysis of geotechnical boundary value problems. While some recent studies (Schadlich and Schweiger 2010, Schweiger and Schadlich 2011) show that the impact of anisotropy in small strain stiffness is rather limited in typical geotechnical boundary value problems involving intermediate to large strains, the influence of anisotropy increases at smaller strains. This study focuses on modeling anisotropic small strain stiffness in multilaminate soil models and its dependency on strain history at load reversals. Evolution of strain history and load reversal is memorized in strain contours on multilaminate plane level, which enables the enforcement of all four Masing rules (Pyke 1979). Model predictions are compared with experimental data on cross-anisotropic Ham River sand at small load cycles.