Rockfill, a granular material with particle sizes usually in the range of 2 cm to 1 m, is a commonly used construction material in a range of civil engineering applications. Rockfill’s complex behaviour mainly stems from its inherently large particle size grading on one hand and its discrete and heterogeneous nature on the other hand. The investigation of mechanical behaviour of rockfill requires expensive and time-consuming laboratory testing in large and very scarce apparatuses. This highlights the importance of numerical investigation techniques
such as Discrete Element Method, in developing a better understanding of rockfill properties. In this paper, Modified Replacement Method; a combination of Replacement and Bonded-Particles (clusters) methods, is pro-posed so the effects of particle shape and breakage, which are among the most effective parameters, can be adequately investigated. The study of stress and volumetric strain-related parameters affected by particle breakage is presented in association with the particle’s characteristic strength, effective confining stress, and friction angle. The modelling results showed the critical broken particles are concentrated at the shear band zones, which are aligned with the mother particles’ translation gradient. Also, for the assemblies with significant particle breakage at high effective confining stresses, the over-compaction led to strength recovery.