Effect of interlayer inclination angle and confining pressure on the energy-dissipation property of sandstone under dynamic triaxial-impact loading

Natural and artificially formed rock-composite structures containing consecutive interlayers at varying angles are frequently affected by coupled dynamic and static loads. To investigate the effects of confining pressure and interlayer inclination angle on the energy-conversion characteristics of interlayered rock masses, triaxial-impact loading tests were conducted using a split Hopkinson bar apparatus. The test results indicated that the stress-time curves were divided into two types as the interlayer inclination angles changed, namely, with or without plastic platform segments. The strain-rebound proportion was hypersensitive to larger interlayer inclination angles and had secondary sensitivity to confining pressures, but was insensitive to smaller interlayer inclination angles. Moreover, the trend of the reflected-energy proportion was opposite to that of the transmitted-energy proportion. The energy-absorption density was proportional to the confining pressure, but inversely correlated with the interlayer inclination angle. As the interlayer inclination angle increased, the absorption energy gradually decreased, whereas the peak stress exhibited a V-shaped tendency. As the confining pressure increased, the absorption energy and peak stress decreased and increased, respectively. In engineering construction, a drill bit at suitable angles with the interlayer was conducive to rock breaking. However, the rock mass with larger interlayer inclination angles in the unloading phase still stored considerable elastic energy, which may trigger secondary rock bursts.