Objective The bedding plane location significantly impacts the dynamic failure processes and mechanical properties of coal-rock composites, but the specific influence patterns remain unclear.
Methods Dynamic mechanical tests were conducted on coal-rock composite specimens with bedding planes located at the top, middle, and bottom using the split Hopkinson pressure bar (SHPB). The investigation focused on the dynamic stress-strain behavior, failure process, energy distribution, and fragmentation characteristics under impact loading conditions.
Results and Conclusions The findings indicate that: (1) The dynamic stress-strain behavior of coal-rock composites can be segmented into five distinct stages: near-linear stage, nonlinear dynamic stress-strain stage, elastic modulus reduction stage, macroscopic rupture stage, and stress wave unloading stage. (2) As the bedding plane location transitions from top to bottom, the extent of rock damage increases, the failure process becomes more pronounced, and the uniformity of post-failure fragments decreases. Conversely, the coal component exhibits a reduction in damage severity and an increase in fragment size after failure. (3) The presence of a bedding plane significantly reduces the dynamic compressive strength of coal-rock composites. Compared to composites without a bedding plane (average strength: 79.487 MPa), the dynamic compressive strength decreases by 7.25% (average strength: 73.724 MPa) when the bedding plane is at the top, by 22.26% (average strength: 61.798 MPa) when at the middle, and by 18.24% (average strength: 64.991 MPa) when at the bottom. (4) The energy distribution changes as the bedding plane location shifts from top to bottom, with a reduction in reflected energy, an increase in absorbed energy, and a decrease in transmitted energy. These results provide valuable insights for optimizing fracturing positions in large-scale hard roof treatment using ultra-long hole hydraulic fracturing or surface fracturing techniques.