A bounding surface plasticity model for the hydro-mechanical behaviour of soils experiencing internal erosion

Internal soil erosion is a major cause of failure in embankment dams, slopes and sea walls. Although several constitutive models have been proposed to simulate soil erosion and its impacts on soil behaviour, they are not able to capture the accumulation of erosion under cyclic hydraulic loading and have significantly simplified the coupling effects between erosion and mechanical behaviour, such as the influence of stress state and void ratio on erosion. In this study, a novel bounding surface model was developed to address these problems. This model incorporates three interrelated bounding surfaces, allowing it to effectively capture soil behaviour under compression, shearing and erosion. A new erosion law was introduced to describe the erosion rate under both monotonic and cyclic hydraulic loading, taking into account the influence of soil density and stress state. To model the impacts of erosion on mechanical behaviour, the effect of the coarse fraction on the critical state void ratio and state parameters was considered. The model was validated using experimental results in the literature. The measured and computed results are consistent along different stress paths, validating the model’s capability to predict changes in coarse fraction, erosion-induced deformation at complex stress states and post-erosion stress–strain behaviour.