To study the influence of axial pressure on the dynamic mechanical properties of granite under cyclic impact loading

a modified dynamic and static combined SHPB system was adopted to perform equal-amplitude cyclic impact on granite samples under five axial pressures (σA=0

0

0

0 and 120 MPa). Experimental results show that under the same cyclic impact loading

the total number of cyclic impacts of the samples first increased and then decreased with the increase in axial pressure

and it reached maximum when σA=60 MPa. The samples under five axial pressures all exhibited typical II-type stress-strain curves. The average strain rate and peak strain of the samples under σA=0

0

90 and 120 MPa increased with the increase in the impact number

while the peak stress and elastic modulus were opposite. The dynamic mechanical parameters of the samples deteriorated faster under σA=0 and 120 MPa. The average strain rate and peak strain of the samples under σA=60 MPa showed a trend of decreasing and then increasing with the increase in the impact number

while it was opposite for peak stress and elastic modulus

and the dynamic mechanical parameters deteriorated slowly. Combined with the acoustic emission energy count in static compression

it can be found that when the axial pressure exceeded the crack initiation stress

the influence of axial pressure on the rock dynamic characteristics converted from strengthening to deterioration under cyclic impact loading.