| Summary: | Coal samples having the same diameter (50 mm) and different length-diameter ratios (<i>l</i>/<i>d</i>), i.e., 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1.0 were tested under dynamic uniaxial impact compression using the Split Hopkinson Pressure Bar (SHPB) experimental system. This study evaluates: (a) The effects of <i>l</i>/<i>d</i> on the energy consumption law and fractal characteristics of coal crushing; (b) The effects of <i>l</i>/<i>d</i> and stress balance on energy dissipation; (c) The effects of <i>l</i>/<i>d</i> and energy consumption density on the fractal characteristics of coal crushing. The findings under different <i>l</i>/<i>d</i> are as follows: (1) The coal samples show similar stress–strain curve shapes in stages including elastic, plastic, and failure stage, which is an “open” shape, the proportion of plastic stage increases, and strain-softening occurs; (2) The dynamic compression dissipation energy and energy consumption ratio of coal shows the same trend, showing two stages with the increase of length-diameter ratio, which increases linearly in the first stage and overall decreases step-by-step; (3) The average particle size increases while fractal dimension of fragmentation decreases linearly, which endorses the decreasing trend of fragmentation degree; (4) It is determined that there is a power relationship between fractal dimension and energy dissipation density; (5) A new index <i>Crushing Density Energy Efficiency</i> (<i>CDEE</i>) is proposed, which can be used to characterize the rock-breaking efficiency of crushing energy consumption under different conditions. This index is inversely proportional to <i>l</i>/<i>d</i>. The research results can provide a basis for the design of top coal caving mining, and the determination of blasting parameters.
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