Modelling mechanical consequences of erosion

The process of internal erosion of fine particles from a soil progressively narrows the grading of the soil. Development of a continuum model for the mechanical consequences of erosion has taken inspiration from two-dimensional discrete element analyses of assemblies of circular discs of various gradings. The process of erosion has been described in these analyses by progressively removing the finer particles while maintaining the sample under constant stresses. The removal of particles produces an increase in specific volume because the volume of solid decreases and the volume of void increases, but the looser structure compresses under the external stresses. Parallel continuum modelling takes an existing distortional hardening model, in which the critical state line plays a central role, and adds a volumetric deformation mechanism to describe the observed compression. The discrete element modelling analyses and other results remind us that the first-order effect of narrowing grading is the raising of the critical state line in the compression plane. The model is closely similar to a model for soils with breakable particles, incorporating the same link between grading and critical states.