Influence of grain-to-particle size ratio on the tensile mechanical response of granite based on a novel three-dimensional grain-based model

In this paper, we developed a novel three-dimensional grain-based model based on the discrete element method (DEM) and reproduced the heterogeneous structure of crystalline granite. We carried out static Brazilian splitting tests to analyze the mechanical properties and micro-cracking behavior of granite samples. Furthermore, we investigated the effect of grain-to-particle size ratio on the tensile strength and discussed the difference in mechanical response of granite samples with different grain sizes and particle sizes under static loading. Our results show that the load-displacement curve of the sample can be divided into initial compaction stage, linear elasticity stage, damage stage, and post-peak stage. Tensile failure is the main failure mode leading to the macroscopic fracture of the sample, and intergranular failure is dominant. As the grain-to-particle size ratio increases, the proportion of the number of transgranular contacts to the number of total contacts increases and stabilizes. Compared with intergranular contact, transgranular contact has a higher bonding strength, and its fracture requires a larger stress concentration magnitude, which leads to an increase in the external load required for the macroscopic fracture of the sample.