1. School of Civil and Architectural Engineering, Wuhan University, Wuhan 430072, China;
2. School of Sciences, Xi’an University of Science and Technology, Xi’an 710054, China;
3. School of Architecture and Civil Engineering, Xi’an University of Science and Technology, Xi’an 710054, China
Abstract：In order to study the dynamic failure law of coal, the impact failure experiment of coal was carried out by using the Φ 50mm split Hopkinson pressure bar (SHPB) device. A finite discrete element (FDEM) model of coal was established based on zero-thickness cohesive element and the relative model parameters were calibrated. Finally, the SHPB impact test is simulated on the LS-DYNA software platform, and the applicability of FDEM in dynamic failure simulating is discussed, and the failure process of coal is analyzed. The results show that: (1) the dynamic compressive strength and strain rate of coal and rock meet the empirical relationship. When the strain rate is 98.05s-1, 119.22s-1 and 135.85s-1, its dynamic strength factor (DIF) is 1.92, 2.08 and 2.23, respectively. (2) Under impact loading, the elastic deformation stage of coal is short, the plastic deformation ability is strong, and the strain rate dependence of dynamic elastic modulus is not significant. (3) FDEM model can simulate brittle failure of rock materials by failure of zero thickness cohesive force element. When the grid size is reasonable, the model parameters calibrated by quasi-static test are also suitable for impact failure simulation due to inertia effect. (4) The fracture degree of coal under impact is positively related to the impact velocity, and its failure forms are the local shear failure caused by compression wave loading and the entire tension failure caused by Poisson effect.
Key words: impact failure; strain rate dependence; split Hopkinson pressure bar (SHPB); hybrid finite-discrete element method (FDEM); cohesive model
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