Rockfill materials have been widely used in the construction of rockfill dam, railway and highway subgrade due to its high filling density, good compaction performance, strong water permeability, small settlement deformation and high bearing capacity. A reasonable constitutive model for rockfill materials is very important for engineering computation and analysis, and has a great development space. Based on the crushing stress and spatial mobilized plane (SMP), a state parameter that can comprehensively reflect the anisotropy and grain crushing is proposed. This state parameter is used to improve the MPZ model (a modifed Zienkiewicz III model), so that a generalized plastic model is constructed to describe the stress and deformation characteristics of rockfill materials in engineering. The validity of the developed model is verified by a series of conventional triaxial tests with different inclination angles of the compaction plane. The variation trend of the constructed anisotropy index ω can reflect the non monotonic variation of the deformation and strength of rockfill with the direction angle of large principal stress, so the model can reflect the obvious difference caused by the initial anisotropy of rockfill on the mechanical properties.
