Effect of Grain Size on the Dynamic Flexural Tensile Strength of Granite: Insight from GBM3D-PFC Simulations

For reproducing the heterogeneous structure of granites, a novel three-dimensional grain-based model based on particle flow code (GBM3D-PFC) was proposed in this paper. Then, dynamic semicircular bending tests under different impact velocities were conducted on the numerical samples with different grain sizes by the coupled split Hopkinson pressure bar system. On the one hand, with increasing grain size, the dynamic flexural tensile strength and proportion of transgranular cracks increase, while the total crack number decreases. On the other hand, as the loading rate increases, the dynamic flexural tensile strength and transgranular crack proportion increase. Based on the GBM3D-PFC, the evolution of the load applied to the sample can be reasonably described. The relationship between the contact force network and the sample's strength can be established. The microcracking behavior obtained by numerical simulations can be used to explain the variation of the macroscopic mechanical parameters.