Broken energy dissipation and fragmentation characteristics of layered rock under impact loading

By using split Hopkinson pressure bar ( SHPB) test apparatus,the dynamic compression tests of layered rocks with different bedding dips of 0°,22. 5°,45°,67. 5° and 90° under different impact velocities were carried out in this study. The fragmentation distribution characteristics of layered rocks were compared and analyzed according to sie- ving the crushed sample debris. The reflection energy,transmission energy,dissipated energy density and fragmentation under different incident energies were discussed. Results show that for the sample with same bedding dip angle,the av- erage particle size gradually decreases as the impact velocity increases. At the same impact velocity,the fracture degree of the specimen with a dip angle of 67. 5° is the largest,and the 0° sample is the smallest. Fractal dimension can quantitatively characterize the fragmentation distribution characteristics. The fractal dimension is larger when the frag- mentation is smaller. At the same incident energy,the dissipation energy density of the 90° sample is the largest,while the dissipation energy density of specimens with 0° or 22. 5° dip angle is smaller,which reveal that a high dip angle has a higher energy utilization rate,and 0° or 22. 5° is lower. At the same incident energy,the 90° samples have higher reflective energy,and the layered rocks with 0° and 22. 5° dip angles have higher transmission energy,which indicates that the reactive power dissipates mostly in the form of reflection waveform at high dip angle and mostly in the form of transmission waveform at low dip angle. The reflection energy,transmission energy and dissipation energy density in- crease with the increase of incident energy. The fractal dimension increases with the increase of dissipation energy den- sity. With the increase of energy consumption at high dip angle,the sample breaks more severely. With the increase of dissipated energy density at low dip angle,the trend of sample fragmentation changes little,and the energy required to produce new cracks and fracture surfaces is high. In engineering practices,if the dynamic loading angle of 45． 0° -67． 5° is selected,not only the strength of rock is low,and the rock sample breaks more severely,but also the energy u- tilization rate is high.