Study on the Cyclic Impact Mechanical Characteristics of Coal under Confining Pressure.

Coal damage accumulation and strength deterioration caused by mining-induced disturbances in deep mines are among the factors influencing the occurrence of dynamic disasters such as rock bursts. To study the mechanical deformation and failure characteristics of coal masses under both cyclic impact and confining pressure, SHPB experiments were performed to systematically analyze the behavior of coal samples under 1, 2, and 3 cycles at impact pressures of 0.25, 0.30, 0.35, 0.40, and 0.45 MPa. To study the influence of pressure and impact frequency on the dynamic mechanical failure of coal samples, a weakening effect model of coal samples under confining pressure was established, revealing the dynamic mechanical characteristics and failure mechanism of coal samples under different impact pressures and impact frequencies. The confining pressure SHPB results reveal that the number of cycles and impact pressure are inversely proportional to the peak stress and are proportional to the degree of weakening. The peak stress weakening coefficient of the coal samples under the different impact pressures ranged from 28.5 to 73.2%, and a linear weakening relationship with the number of cycles was obtained. The coal exhibited an end effect-controlled Y-shaped failure mode under both confining pressure and dynamic loading. This study provides an experimental reference for preventing the energy absorption and erosion of weak structures around rock bursts and improving the stability of supporting structures.