Particle breakage is one of the major factors to affect the strength and deformation characteristics of rockfill materials. Particle breakage of rockfill materials is more obvious at low stress level in comparison with sands, Thus, the effects of particle breakage on mechanical characteristics and constitutive model of rockfill materials need to be considered. Since the void ratio of rockfill materials is not constant during the loading process, the traditional constitutive model, which cannot use a set of parameters to simulate the same rockfill with different void ratios, is not suitable. Therefore, it is necessary to develop a hypoplastic constitutive model of rockfill materials, which incorporates the representative void ratio expressions and particle breakage. Meanwhile, this model is based on Gudehus-Bauer hypoplastic constitutive model, which can consider the different characteristics of the void ratio between rockfill and sand. Particularly, the hypoplastic constitutive theory has the least assumption. Under different representative stress paths, the strain increments of granular materials are various. However, under different representative stress paths even with the same level of stress, the representative void ratio of rockfill is difficult to satisfy the equal proportion rule that is successfully used in the Gudehus-Bauer hypoplastic constitutive model for sand. Therefore, a series of the representative void ratio expressions incorporating particle breakage is proposed based on both the particle breakage critical state theory and experimental results. Subsequently, these expressions are introduced into Gudehus-Bauer hypoplastic constitutive model to establish a hypoplastic constitutive model of rockfill materials incorporating particle breakage. In addition, the method to determine the parameters of model is provided. Finally, the constitutive model is applied to simulate the test results of rockfill materials in the literature, which indicates that the proposed constitutive model can well simulate the stress-strain behaviuors of rockfill materials.
