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<p>The variability of the normal coefficient of restitution (NCOR) of crystalline rocks poses major challenges for accurately predicting rockfall trajectories and designing protective structures. This study investigates the micromechanical mechanisms governing NCOR in parameterized polycrystal rocks through a series of two-dimensional discrete element simulations (PFC2D) based on a grain texture model (GTM) that explicitly considers grain aspect ratio, inclination angle, and specimen size. The results show that NCOR discreteness originates from intrinsic grain structure heterogeneity rather than experimental uncertainty. The maximum NCOR difference reaches 49.3%, with the influence of inclination angle exceeding that of aspect ratio. Grain geometry and orientation regulate the partitioning of elastic and inelastic energy by controlling force-chain transmission and crack propagation. The grain structure effect exhibits strong velocity dependence: it dominates in the 3–12&#xa0;m/s range, but diminishes at higher velocities as macroscopic fracturing governs energy dissipation. Furthermore, the underlying mechanisms remain scale-robust across specimen sizes. These findings clarify the microscale origins of NCOR variability in parameterized polycrystal rocks under the calibrated 2D DEM framework and the investigated impact velocity range, and provide theoretical support for refined parameter selection in rockfall hazard analysis and impact-resistant design.</p>

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Grain-Scale Origins of Variability in the Normal Coefficient of Restitution of Polycrystal Rocks: Numerical Insights into Velocity-Dependent Microstructural Effects

  • 期刊论文

  • 发表日期：

    2026年3月13日

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  • Ning Hu,
  • Bei Zhang,
  • Quanzhong Lu,
  • Hengxing Lan,
  • Jianbing Peng

摘要

The variability of the normal coefficient of restitution (NCOR) of crystalline rocks poses major challenges for accurately predicting rockfall trajectories and designing protective structures. This study investigates the micromechanical mechanisms governing NCOR in parameterized polycrystal rocks through a series of two-dimensional discrete element simulations (PFC2D) based on a grain texture model (GTM) that explicitly considers grain aspect ratio, inclination angle, and specimen size. The results show that NCOR discreteness originates from intrinsic grain structure heterogeneity rather than experimental uncertainty. The maximum NCOR difference reaches 49.3%, with the influence of inclination angle exceeding that of aspect ratio. Grain geometry and orientation regulate the partitioning of elastic and inelastic energy by controlling force-chain transmission and crack propagation. The grain structure effect exhibits strong velocity dependence: it dominates in the 3–12 m/s range, but diminishes at higher velocities as macroscopic fracturing governs energy dissipation. Furthermore, the underlying mechanisms remain scale-robust across specimen sizes. These findings clarify the microscale origins of NCOR variability in parameterized polycrystal rocks under the calibrated 2D DEM framework and the investigated impact velocity range, and provide theoretical support for refined parameter selection in rockfall hazard analysis and impact-resistant design.