Research on Dynamic Mechanical Properties and Numerical Simulation of Broken Coal-Rock Grouting Consolidation Bodies

Dynamic hazards during coal mining pose significant risks to the stability of surrounding rock and engineering structures, making grouting reinforcement technology widely applicable in such projects. Using grout-consolidated specimens with varying grouting pressures (1, 2, 3, 4 MPa) as research objects, the split Hopkinson pressure bar (SHPB) impact test was carried out, the interface microstructure was analyzed by scanning electron microscopy (SEM), and the finite element simulation was conducted using LS-DYNA software for multi-angle analysis. This systematic investigation elucidated the coupled effects of grouting pressure and effective confining pressure (0, 2, 4, 6 MPa) on the dynamic mechanical behavior of polymer-modified cementitious grouted coal-rock composites. The results reveal that increasing grouting pressure enhances the peak stress, transmitted energy, dissipated energy, and toughness of the samples. At optimal grouting pressure (4 MPa), specimens exhibited peak dynamic compressive strength of 24.703 MPa, representing an 18.13% enhancement compared to 1 MPa grouting pressure. Concurrently, fragmentation energy consumption reached 13.431 J with energy utilization efficiency of 40.183%; SEM microstructure analysis confirmed that the polymer chain segments interacted with the hydration products of cement during the hydration process, forming a denser and stronger network structure, strengthening the interface transition zone, and the toughness index reached 26.323 MJ/m³, significantly improving the crack resistance, toughness and dynamic bearing capacity of the specimens; Numerical simulations quantified distinct energy absorption mechanisms, with the cement matrix absorbing 61.08% of impact energy versus 38.92% by the coal matrix. During the failure process, the crack propagates along the cement-to-coal interface or penetrates the coal particles, leading to bond failure and particle breakage, consistent with experimental observations. These findings provide quantitative technical guidance for optimizing grouting material selection and reinforcement strategies in coal-rock engineering applications.