Parameter Determination and Numerical Simulation of the Sandstone HJC Constitutive Model

The surrounding rock of the bottom drainage roadway at the Guhanshan Coal Mine is composed of hard sandstone, characterized by structural integrity and high strength. However, due to an inadequate basis for parameter selection during presplitting blasting to aid rock breaking, the overall excavation efficiency is low. To address this issue, this study calculates the equation-of-state parameters for the Holmquist-Johnson-Cook (HJC) constitutive model. These parameters are derived using the basic physical and mechanical parameters of the hard sandstone samples from the bottom drainage roadway at the Guhanshan Coal Mine, combined with the theoretical approach for determining HJC model parameters. Using the obtained parameters, LS-DYNA software is used to conduct numerical simulation research on the dynamic impact of sandstone. The simulation captures the physical and mechanical responses of intact sandstone samples under varying impact velocities. The results demonstrate that the stress-strain curves from indoor experiments closely align with simulation outcomes. During the loading process, specimen cracks initiate at the center and propagate toward the edges. Tensile cracks initiate and gradually expand until specimen failure, addressing the deficiency of the physical experiment observations. The HJC constitutive model effectively represents the mechanical behavior of sandstone samples under different impact velocities. The particle size, crack width, and penetration of the fractured specimen effectively characterize the rate effect of the impact dynamic load. These parameters show a positive correlation with the loading speed. Numerical simulations of presplitting blasting were conducted on rock models with varying borehole layout configurations using the calibrated constitutive model parameters. The results demonstrate that under identical charge parameters, the equilateral triangular borehole layout configuration achieves the most extensive damage propagation. Therefore, the equilateral triangular borehole arrangement is recommended as the optimal configuration for presplitting blasting in the bottom drainage roadway of Guhanshan Coal Mine.