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.