Abstract: An elastoplastic constitutive model considering the particle breakage is proposed for rockfill materials within the framework of generalized plasticity. In the model, both the peak friction angle and the characteristic friction angle decrease with the increase of the mean stress so that the nonlinear dependence of the peak stress ratio and the dilatancy stress ratio on the mean stress is captured. The plastic flow direction and the loading direction are then formulated using the above characteristic stress ratios. Another feature of the model is the adoption of the exponential compression equation, based on which the representation of a volumetric strain-dependent and pressure-dependent compression index λ is established so as to formulate the plastic modulus, which is a function of the mean stress and the shear stress level. There are totally 8 parameters in the model, all of which can be determined by isotropic, oedometric and triaxial compression tests. To check the validity of the model, the parameters of three rockfill materials are calibrated based on the experimental data, and the typical triaxial compression tests are modelled. Satisfactory agreement between the numerical and experimental results confirms the capability of the proposed model in capturing the influences of the particle breakage on the strength and deformation behaviour of rockfill materials.