Granular breakage is a common phenomenon among rockfill dams, mineral engineering, and geological phenomenon. In this work, we perform one-dimensional compression tests using the discrete element method to study the influences of fragmentation patterns during comminution. Our results show that small fragments increase the coordination number of larger particles and create "hydrostatic" confinement. The combined effect of size hardening law of particle strength (i.e., smaller is stronger) and increasing hydrostatic confinement result in the stagnation of particle size reduction. When more and more small fragments participate in the force transmission, particle contact force evolves from exponential distribution to fractal distribution. With the increasing applied stress, breakage events become more spatially localized. Our findings indicate that particle breakage and size hardening law of particle strength would be reasons for the robust fractal structure in granular materials, i.e., both particle size and particle contact force are distributed in a fractal manner. (C) 2019 Elsevier B.V. All rights reserved.