An Analysis Of The Rock’s Dynamic Properties And Its Failure Characteristics

By using Split Hopkinson Pressure Bar experiment device, the selection of the bullet was three series, which was all 50 mm in diameter and 500 mm, 400 mm and 300 mm in length respectively. The three series of bullet impact on 50 mm in diameter and 25 mm in thickness of Granite, Phyllite, Lean Ore and Magnetite Quartzite under incremental pressure respectively. Through experiment, it was obtained the analysis of the rock’s crushing process and fragmentation mechanism under dynamic loading, It was established the strain stress curve of four kinds of rock under the same dynamic loading on them, and fitted out the correlation between the peak stress and the strain rate.Through the analysis of the energy dissipation of rock specimens under different dynamic loading, it was probed into the relationship between Specific Energy Absorption (SEA) and incident energy with high linearity; SEAT (Energy Density) was defined as the ratio of SEA and the time of the reflected wave, the relationship between SEAT and bullet impulse, incident energy and Dynamic Increase Factor (DIF) was analysed and discussed; Trough statistics of the specimen broken blocks, the relationship between the fractal dimension of the fractured blocks and SEAT was fitted out, then it was concluded the optimum matching between SEAT and rock specimen with the quota of the best fractal dimension of the fractured blocks under the different impact of bullet.With the help of mesoscopic mechanics theory, the fractal theory and the analysis method of scanning electron microscope image, it was illustrated mesoscopic crushing process and fragmentation mechanism under dynamic loading, and discussed the relationship between SEAT and the fractal dimension of the typical debris on the surface, and probed into the correlation between DIF and the fractal dimension of the typical debris on the surface under the different impact of the bullet on rock specimen with different fractal dimension on the surface; It was fitted out of the experimental data with the relational expression SEAT∝ Df1EXP[-(n/Df)Df2], the study showed that it was a certain correlation between SEAT of four kinds of rock specimens and fractal dimension on the rock surface, the typical debris on the surface, the fractal dimension of the fractured blocks and the uniformity coefficient of the debris, then it could be obtained the minimum SEAT under the different impact of bullet on the different rock specimens.According to the maximum of SEA, the maximum of SEAT and the minimum of SEAT with the same broken state case under the different impact of bullet on the different rock specimens, it was concluded the optimum matching between the bullet and rock specimen in the experiment. Then the paper was also simply discussed the damage expression of the debris under dynamic loading on specimen.