The stress environment of deep coal-rock mass is complex, to further reveal the mechanism of rock burst induced by dynamic load. Based on th
The stress environment of deep coal-rock mass is complex, to further reveal the mechanism of rock burst induced by dynamic load. Based on the Split Hopkinson Pressure Bar test system, the dynamic tests under different stress states (non-axial and confining loads, one-dimensional coupled static-dynamic loads, three-dimensional coupled static-dynamic loads) and strain rates (49.3～137.9 s−1) were carried by using the rock-coal-rock structure samples. The characteristics of strength, deformation, failure and energy evolution of rock-coal-rock structure samples were studied. The results show that there were two types of stress rebound and strain softening after the peak of the stress-strain curve of the composite specimen under non-axial and confining loads and under one-dimensional coupled static-dynamic loads, and there was stress rebound phenomena under three-dimensional coupled static-dynamic loads. Under three stress states, the peak strength of the samples increases roughly with the increase of strain rate, showing an obvious rate correlation. Under three stress states, the proportion of reflected energy to incident energy was the highest, and the proportion of transmitted energy to incident energy was the lowest. The proportion of reflection energy to incident energy under three-dimensional coupled static-dynamic loads was lower than the other two stress states. When the strain rate is lower than 123 s−1, the energy utilization rate and dissipated energy increase gradually with the increase of the strain rate, and the dissipated energy density increases with the increase of the incident energy. The failure modes of the samples show an obvious rate correlation, and the size of coal and sandstone fragments decreased gradually with the increase of strain rate. Under non- axial or confining loads and one-dimensional coupled static-dynamic loads, the samples firstly failed at the coal-rock interface. Many small size fragments of coal and sandstone are secondary cracks caused by the effect of loads. The fracture of coal and rock mass is not obvious under three-dimensional coupled static-dynamic loads.
