Experimental Study on the Mechanical Behavior of Coal under Triaxial Dynamic Compression

The frequency and intensity of coal-rock dynamic incidents in underground coal mining, such as coal bumps and outbursts of coal and gas, tend to increase with mining depth. These dynamic incidents are closely related to the dynamic mechanical behavior of coal. In this experimental study, the dynamic mechanical behavior of coal was investigated with an active triaxial split Hopkinson pressure bar (SHPB) test system. In the test, the in-situ stress field for coal with an overburden depth of 100 m to 600 m was simulated and the dynamic loading tests of coal were undertaken under low, medium, and high loading rates. The results of the study show that the dynamic compression strength of coal increases with loading rate and axial and confining stress, and the effect of confining stress is more profound than that of axial stress. The results also reveal that the energy consumption and energy density per unit volume of coal are positively correlated with the depth and loading rate. This study may help gain insights into the occurrence mechanism of coal-rock dynamic incidents in underground coal mining.