Unified Modeling of Interface between Structured Clay or Crushable Sand and Structure

The purpose of this paper is to develop a unified elastoplastic model for describing both monotonic and cyclic behaviors of natural structured clay-structure and crushable sand-structure interfaces based on the bounding surface plasticity and the critical state concept with three features: (1) a more general yield surface with two shape parameters is adopted to improve the prediction of the shear yield and the critical state of the soil-structure interface, (2) the degradation of bounding surface size and the adhesive normal stress is introduced into the model to consider the shear strength reduction of natural structured clay-structure interface, and (3) the grain breakage effect on the behavior of crushable sand-structure interface is considered by incorporating the location of the critical-state line with the broadening of grain-size distribution induced by grain breakage. Then, explicit simulation schemes with substepping and error control are established for simulating interface shear tests under constant volume, constant normal load, and constant normal stiffness conditions. Finally, comparisons between experimental and numerical results indicate that the unified soil-structure interface model is able to not only predict the state-dependent monotonic stress-strain behavior of structured clay-structure or crushable sand-structure interfaces, but also reproduce the cyclic accumulative contraction and stabilization, as well as the stress degradation observed in both structured clay-structure and crushable sand-structure interfaces.