Sensitivity analysis of rock dynamic response based on a multi-scale parameter model

The micro-stiffness ratio plays a significant role in the dynamic response characteristics of rock materials when analyzed using particle flow code. In this study, a macro–micro parameter model is developed to relate the micro-stiffness ratio to the macro-Poisson's ratio, revealing the relationships between multi-scale parameters. Large-scale split Hopkinson pressure bar numerical simulations are conducted to investigate the sensitivity of the dynamic mechanical characteristics of limestone to variations in the micro-stiffness ratio. The results indicate that, under impact loading, the force chain gradually concentrates toward the center of the specimen, forming a symmetrical saddle-shaped boundary. As the micro-stiffness ratio increases, both the normal peak stress and elastic modulus decrease, while the normal strain rate and strain acceleration increase. Axial and radial stresses exhibit similar sensitivity to the micro-stiffness ratio. The proportion of axial dissipated energy increases with the micro-stiffness ratio, whereas the proportion of radial dissipated energy decreases. The initiation time of damage evolution is significantly correlated with the micro-stiffness ratio: higher ratios lead to earlier initiation of damage evolution but slower damage accumulation. Consequently, the failure mode transitions from sudden brittle failure to slow and gradual failure.