A Three-Dimensional Multishear Bounding Surface Model of Granular Soil–Structure Interfaces under Monotonic and Cyclic Loading

This study develops a three-dimensional multishear bounding surface model for simulating the constitutive response of interfaces between the granular soil and structure. Based on the plasticity slip theory, the model is established by splitting the overall response of interfaces into a macronormal response and a series of orientated microshear responses in microshear structures. This discrete approach provides a simple and effective means to predict the macroshear response of interfaces by superposition of individual responses from all microshear structures. The microshear structure consists of a microshear response and a micronormal response due to dilatancy, which are described by a microstress–strain relation and a microstress–dilatancy relation, respectively. By introducing a state parameter related to the critical state of granular soils, the model is suitable for predicting the constitutive response of interfaces for various soil densities and normal stresses. The effectiveness of the model is confirmed by simulating the granular soil–structure interface tests with different boundary and load conditions.