Study on dynamic mechanical behavior of single-jointed rock mass under cyclic impact loading

In practical engineering, rock masses frequently suffer from recurrent dynamic disturbances, posing serious threats to engineering safety. To investigate the dynamic mechanical behavior of jointed rock masses under cyclic dynamic disturbances, cyclic impact tests were conducted on single-jointed gabbro (SJG) using a split Hopkinson pressure bar test system. The stress equilibrium during the tests was verified using the three-wave method and the force balance coefficient method. The dynamic mechanical behavior of the specimens was comprehensively analyzed in terms of impact resistance, stress-strain relationships, energy and damage evolution, as well as dynamic failure mechanisms. The results show that single-jointed rock specimens can achieve stress equilibrium under cyclic impact conditions. The failure mode of the specimens under cyclic impacts is splitting, and the joint inclination angle significantly influences the impact resistance of the specimens. As the joint inclination angle increases, the impact resistance of the specimens also increases. During the cyclic impact process, strain rebound occurs in all specimens, and their mechanical properties do not monotonically degrade with an increasing number of impacts. The peak stress of the specimens generally exhibits a decreasing trend with the number of impacts. The cumulative damage coefficient, represented by dissipated energy, increases approximately linearly with the number of impacts, while the rate of increase decreases with larger joint inclination angles. Under low-stress impacts, the compressive-shear stress inside the specimens is insufficient to produce shear cracks, and tensile stress causes tensile cracks at the initiation points, which propagate along the loading direction and ultimately lead to splitting failure of the specimens.