Abstract: In order to explore the failure characteristics and energy dissipation law of coal during the impact process, the impact compression test of coal under different strain rates has been carried out by using split-Hopkinson pressure bar (SHPB) of 75 mm in diameter．The influence of loading rate on the energy dissipation and fragment distribution has also been discussed．The experiment results have shown that, the strain rate and energy of stress wave are increasing linearly with the improvement of the bullet velocity．Meanwhile, the dissipation energy which leads to the coal broken is increasing exponentially with strain rate．According to the research on fractal dimension of coal fragment, it has been found that the greater the strain rate is, the larger the fractal dimension is, the smaller the fragment-size is, the more severe fragmentation is. The relationship between fractal dimension and strain rate and dissipated energy density is of logarithmic growth, which means the increasing trend of fractal dimension is getting slower.

Key words: coal, split-Hopkinson pressure bar, dynamic impact, energy dissipation, fractal dimension