Influence of grain contents on the dynamic strength of rock-like materials

This study performed a series of uniaxial compressive tests and SHPB tests to investigate the influence of grain content and loading rate on strength and failure mode of rock-like materials. Two grain packing arrangements with 40% and 60% grain contents by volume were used to reflect the compositions of rock. According to the test results, the simulation of discrete element method (DEM) was further performed. The proposed simulation could reflect the breakable characteristics of grains so it provided a reasonable prediction on the dynamic strength of rock-like materials. The results indicate a lower grain content and, correspondingly, a higher matrix volume, yields a higher quasi-static strength (at strain rates from 10⁻⁴ to 1 s⁻¹). The dynamic strength (at strain rates from 1 × 10² to 5.98 × 10² s⁻¹) is related to not only the grain content but also the degree of grain breakage, denoted as the TG in this study. Increasing the strain rate increased the TG, increasing the strength in turn. This study clarified the effect of grain breakage on the dynamic strength. On account of the failure patterns, inter-granular fractures mainly occur under quasi-static compressive conditions, and the failure mode becomes transgranular when the strain rate is high. Specimens with lower grain content exhibited fewer fractures and larger fragments than those with higher grain content.