Research on discrete element parameter calibration of coal based on similarity theory

To obtain the optimal combination of discrete element simulation parameters for unscreened bituminous coal, a combination of physical and simulation experiments was used for parameter calibration. A typical particle model with different particle size ranges was established, and the particle size was enlarged by 5 times based on the similarity theory. Three significance variables were determined by Plackett-Burman test, steepest ascent test, and Box-Behnken test. Then the minimum relative error of the experimental and simulation repose angle was taken as the optimization objective to obtain the optimal parameter combination. The physical experiment measured a density of 1.326 t/m3 and static friction coefficients of 0.72 and 0.41 for coal-coal and coal-steel, respectively. The simulation was calibrated to give a Poisson's ratio of 0.4, a shear modulus of 0.67 GPa, rolling friction coefficients of 0.107 and 0.095 for coal-coal and coal-steel respectively, restitution coefficients of 0.5 and 0.15 for coal-coal and coal-steel respectively, and the Johnson Kendall Roberts (JKR) surface energy of 14 J/m2. It is only a 0.58% difference that separates the simulated repose angle of 37.59° from the experimental repose angle of 37.81°, providing the basic parameters for discrete element simulation of bituminous coal with similar characteristics.