Abstract: Based on mesoscopic damage mechanics, numerical code RFPA2D is developed to simulate the failure process of rock specimen subjected to dynamic loading; and the failure characteristics of rock specimen under different continued times and different amplitudes of stress wave and different confining pressures are studied; in the meantime the failure properties of rock specimen under static and dynamic loadings are compared. Numerical results indicate that the shorter continued time of stress wave, the narrower high stress area after wave front, the faster stress wave attenuates; On the contrary the longer the continued time of stress wave, the larger high stress area after wave front, the longer time is lasted for rock failure, the more cracks initiates and propagates. Furthermore, appropriate continued time is necessary for cracks of rock specimen to initiate and propagate, and on the contrary excessively long continued time goes against cracks growth. The more amplitude of stress wave, the more the fragmentation degree of rock specimen, and to certain amplitude, comminution mode appears at the top of rock specimen; and the breakage degree wears off from top to bottom of rock specimen. Rock is more difficult to break up when confining pressure increases under high speed impact loading, and rock failure occurs suddenly when confining pressure increases to certain value; By contrast to static loading condition, more cracks initiate and propagate under dynamic loading, which cause the damage and fracture of whole rock specimen.

Key words: numerical simulation, dynamic loading, failure process, continued time of stress wave, amplitude of stress wave, confining pressure