Novel erosion law based on CFD–DEM simulations and its application in hydromechanical modeling of gap-graded soils

This paper develops a novel erosion law that incorporates the influence of stress state into the mass exchange between the liquid and solid phases for suffusion, using the coupled computational fluid dynamics and the discrete element method (CFD–DEM) simulations. To achieve this, a series of CFD–DEM simulation tests are conducted on gap-graded soil samples, followed by the derivation of a new erosion law that considers the influence of seepage velocity and mechanical conditions. The proposed erosion law is then integrated into a four-constituent framework to enable hydromechanical modeling. Furthermore, a fines-dependent constitutive model based on the critical state concept is implemented to account for the influence of suffusion on the mechanical behavior of the soil. The new model is assessed through a series of laboratory hydromechanical tests, yielding satisfactory estimation results. Subsequently, the model is utilized to investigate the influence of soil initial state, including void ratio, friction angle, fine content, and size ratio, on the evolution of erosion. Finally, the mechanical behavior of soils before and after suffusion is modeled using the proposed framework. The results demonstrate that the CFD–DEM-based erosion law, as well as the hydromechanical model, effectively capture the main characteristics of soils subjected to suffusion.