Effect of original pores on dynamic characteristics of granite under cyclic impact loading

Abstract

The existence of pores in granite can change its dynamic characteristics. In order to study the effect of pores on rock dynamic parameters during cyclic impact loading, a split Hopkinson pressure bar (SHPB) test system was used to conduct cyclic impact tests on granite samples with large porosity. The evolution of peak stress, average strain rate and other parameters under different impact intensities was analyzed. The results show that the pores in rock material have obvious influence on its dynamic properties, and the evolution trend of dynamic properties is obviously different under different impact loads. Low impact load will cause abnormal increase of peak stress. When the impact load intensity is increased, the peak stress evolution shows a trend of rising first and then decreasing. When the impact load strength continues to increase, the peak stress mainly presents a downward trend. Under cyclic impact of low strength and high strength loads, the average strain rate increases slowly. The average strain rate of rock shows an obvious trend of decreasing first and then increasing under moderate strength cyclic impact.