Yielding function for coarse aggregates considering gradation evolution induced by particle breakage

Gradation, one of the most important physical characters of soils, has significant influence on the stress strain response of coarse aggregate. Accurate prediction of the gradation evolution during loading procedure is an essential part for efficient analysis of strength and deformation characteristics of soil structures. Following Einav's fractal breakage theory, the energy dissipated from particle breakage during loading is assumed to be in direct proportion to the increment of fractal breakage ratio. Method of measuring the gradation evolution during loading as well as a novel yielding model considering gradation evolution of coarse aggregate is then established by employing a well-known energy equation. Investigation of the gradation evolution of coarse aggregates is thus conducted by employing corresponding experimental data from relevant literatures. After that, preliminary discussion of the newly proposed yielding function is also conducted. It is observed that each yield surface during loading corresponds to a specific gradation of coarse aggregate. Moreover, the yield surface is suggested to be a shear strain-based isosurface, of which the shape is mostly determined by shear strain.