The energy evolution characteristics of coal under different dynamic strain rates and confining pressures

Coal specimens from baijiao coal mine were impacted by a split Hopkinson pressure bar to study its dynamic mechanical behavior under different confining pressures (0-12 MPa) and different strain rates (20-250 s-1). The performances and the energy evolution characteristics of the coal specimens were analyzed. The results show that the strengthening effect and toughening effect of rock are gradually enhanced with the increase of confining pressure. At the same time, the coal failure gradually transitions and develops from tensile failure to compression-shear failure under the action of confining pressure. The peak strength and peak strain of coal rock show significant strain rate correlation and strong confining pressure effect with the change of confining pressures and strain rates. The dynamic strength growth factor of coal is approximately linear with the increasing of strain rates. The energy density and energy absorption density increase linearly with the increase of strain rates, and the energy consumption ratio has a logarithmic growth relationship with the strain rates.