A small-strain overlay model

The paper begins with a discussion of the phenomenon of small-strain stiffness and presents the small-strain overlay model, it simple model that takes into account the non-linear stiffness of soils at small strains. The new model call enhance already established elastoplastic formulations for non-linear stiffness variation at small strains in a similar way that intergranular strain enhances the hypoplastic model. The overlay model is driven by the material's strain history and only two additional material constants, both with clear physical meaning. Therefore, the proposed model is a step towards the incorporation of small-strain stiffness into routine design. In this paper, the new small-strain overlay model is formulated. Its ability to take into account the influence of various strain histories on soil stiffness is illustrated in several examples. Copyright (C) 2008 John Wiley & Sons, Ltd.