Abstract: The jointed rock mass is the most common kind of rock in the practical engineering, therefore the jointed rock’s mechanical response and failure process under dynamic loading such as earthquake and explosion is crucial to the safety of the relevant engineering. Based on the finite element stress analysis and the microscopic damage mechanics, numerical code RFPA2D is developed to simulate the failure process of intermittent jointed rock mass subjected to dynamic loading. The failure characteristics of intermittent jointed rock mass with different numbers of joints, different joint discontinuity degrees and different joint dip angles under different amplitudes of stress wave are studied respectively. The numerical results show that the failure process and failure extent of intermittent jointed rock mass is closely related to the parameters of joints and amplitudes of stress wave. Under the same dynamic loading, with the increase of the number of joints, fragmentation degree of the rock mass and stress wave energy grows clearly at first, but to a certain number, the fragmentation degree and stress wave energy tends to be stable gradually. When the joint discontinuity degree is little, the fragmentation degree of rock mass is low and the failed units uniformly distributed from top to bottom relatively. With the increase of the length of joint, the fragmentation degree of rock mass becomes more and more serious, and the failed units mainly appear in the rock above the joint. When the joint dip angle is little, the upper rock is fractured more obviously and easy to form new cracks relatively. With the increase of the joint dip angle, the damage range expanded, and the rock mass is more difficult to form new cracks. Besides, the fracture effect of rock mass with a joint dip angle of 45°-60°,is the best. The more amplitude of stress wave is, the more serious the fragmentation degree of rock specimen is. When the amplitude of stress wave reaches a certain value, multiple cracks will be formed near the joint and extend upward and downward, which will cause the rock mass to fully fracture. Finally, the damage of rocks with different joint discontinuity degrees is compared with the damage of split Hopkinson pressure bar test. This method is proved to be reasonable and reliable by the similar conclusion.

Key words: dynamic loading, jointed rock mass, numerical experiment, joint property, accumulative amounts of AE