Mechanical property and damage evolution mechanism of granite under uniaxial cyclic impact

Abstract:

To study the dynamic mechanical properties of biotite granite under cyclic impact loading, four different stress amplitudes of incident wave were selected to cyclically strike the rock samples on a modified split Hopkinson pressure bar (SHPB). The related mechanism and experimental phenomenon were analyzed. Results showed that when the stress amplitudes of incident wave were 110.57 and 90.48 MPa, the peak stresses of the rock samples decreased gradually with an increase in the number of impacts, while the maximum strain, average strain rate, and damage value all increased. When the stress amplitude of incident wave was 70.82 MPa, the peak stress of the sample first increased and then decreased as the number of impacts increased, while the opposite law occurred for the maximum strain, average strain rate, and damage value. As the stress amplitude of incident wave dropped to 50.69 MPa, the mechanical properties of the rock sample were basically unchanged, and no obvious damage was detected inside the rock sample. Besides, it was found that the static crack initiation stress determined based on the static compressive stress-strain curve could be extended to the dynamic loading state by multiplying a strength increase factor, which could well explain the phenomenon observed in the cyclic impact test.