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.