Influence of particle breakage on the fabric evolution of granular materials

The macroscopic behavior of granular materials emerges from micromechanical interactions within particle assemblies, where fabric anisotropy serves as a key descriptor of particle rearrangements and microstructural evolution. Although the evolution of fabric anisotropy has been extensively investigated through X-ray tomography and Discrete Element Method (DEM) simulations, the influence of particle breakage under high stress remains insufficiently explored. In this study, DEM simulations with crushable particles are conducted to quantify how particle breakage modifies key fabric metrics, including coordination number and fabric anisotropy, under undrained triaxial compression across various confining pressures. A mass- and volume-conserving fragment replacement scheme is implemented to isolate the causal role of particle breakage. The evolving particle size distribution is tracked through a scalar breakage index. The results show that particle breakage suppresses strength and dilatancy, while the critical-state stress ratio remains largely unchanged within the investigated material and stress range. The all-contact coordination number decreases markedly with increasing breakage, whereas the mechanical coordination number is only slightly affected. Fabric anisotropy diminishes with increasing breakage severity, whereas its normalized form exhibits a slight increase. Based on these observations, a rate-form evolution law for fabric anisotropy that explicitly accounts for particle breakage is proposed, providing new insight into the coupling between microstructural degradation and macroscopic behavior of crushable granular materials.