Abstract
Research on the dynamic mechanical properties of coal rock has gradually become an active area of investigation; however, most dynamic loading experiments are completed instantaneously, precluding detailed study of failure and damage mechanisms. Therefore, this study employs LS-DYNA software to conduct numerical simulation of Split Hopkinson Pressure Bar (SHPB) experiments on coal rock specimens under low-velocity impact loading, based on the Holmquist-Johnson-Cook (HJC) constitutive model for rock. The entire experimental process is reproduced using the LS-PrePost post-processor, thereby recreating the damage evolution and failure details of coal rock under impact loading. The research demonstrates that: (1) The stress-strain curve obtained from the HJC-based simulation of the coal rock impact loading experiment shows good agreement with the measured curve, with a simulated stress peak of 7.03 MPa and a relative error of 18.1% compared to the experimental value. (2) Under an impact load of 3.693 m/s, failure initiates at both ends of the coal rock, forming small fragments, followed by tensile failure along the axial direction, creating axial cracks that propagate through the specimen, and finally resulting in radial cracks. Under low-velocity impact conditions, the coal rock fractures into fragments of varying sizes without discernible patterns, with large and small fragments each comprising approximately half of the total. (3) The energy consumption of coal rock under impact loading can be divided into three primary stages: the energy consumption rate initially increases slowly, then rises sharply, and finally stabilizes.
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Preamble
NUMERICAL SIMULATION STUDY ON DYNAMIC IMPACT MECHANICAL PROPERTIES OF COAL AND ROCK MASS BASED ON LS-DYNA
JIANG Shichao (China Railway 16th Bureau Group Co. Ltd., Beijing 100018, China)
Abstract
Research on the dynamic mechanical properties of coal-rock masses has emerged as a prominent area of investigation. However, most dynamic loading experiments are completed instantaneously, which precludes detailed examination of damage and failure mechanisms. This study addresses this limitation by employing the Holmquist-Johnson-Cook (HJC) constitutive model for rock and utilizing LS-DYNA software to conduct numerical simulations of Split Hopkinson Pressure Bar (SHPB) experiments on coal-rock specimens under low-velocity impact loading. The LS-PrePost post-processor is further utilized to reproduce the entire experimental process, thereby revealing the detailed damage evolution and failure characteristics during impact. The research findings demonstrate that: (1) The stress-strain curve obtained from the HJC-based simulation of the coal-rock impact loading experiment shows good agreement with the measured curve, with a simulated peak stress of 7.03 MPa and a relative error of 18.1% compared to the experimental value. (2) Under an impact load of 3.693 m/s, failure initiates at both ends of the coal-rock specimen, forming small fragments, followed by tensile failure along the axial direction that creates through-going axial cracks, and culminating in radial cracking. In the low-velocity impact regime, the coal-rock fractures into fragments of varying sizes without a distinct pattern, with large and small fragments each comprising approximately half of the total. (3) Energy dissipation in coal-rock under impact occurs in three primary stages: the energy dissipation rate initially increases slowly, then rises sharply, and finally stabilizes.
Keywords: coal-rock; Split Hopkinson Pressure Bar; LS-DYNA; HJC model; impact loading