Dynamic characterization of pressurized coal under cyclic weak impact loading

Deep mining coal body fissure development, and affected by high geostress and weak impact disturbance, deep mine dynamic disasters are frequent. To investigate the dynamic response behavior of pressurized coal under weak impacts under impact load, Separate Hopkinson Pressure Bar (SHPB) was used to analyze the dynamic mechanical parameters changes and damage evolution of pressurized coal under different number of weak impacts (0.2 Mpa) and crushing impacts (0.8, 1.0, 1.2, and 1.4 Mpa), and to construct visco-elastic damage constitutive model to describe the dynamic strain-strain curve. The study shows that: (1) Under the weak impact load and the same crushing impact load, the dynamic compressive strength and modulus of elasticity of the pressurized coal show a tendency to increase and then decrease with the increase of the number of weak impacts, and the dissipation rate changes in the opposite trend, and the specimens are first compacted and then damaged; (2) The degree of crushing is intensified with the increase of the crushing impact pressure, and the degree of crushing decreases due to the first three weak impacts; (3) The Z-W-T model is improved to construct a viscoelastic constitutive model to describe the dynamic mechanical behavior of pressurized coal under cyclic weak impact loading (R² > 0.92).