Energy Dissipation and Stress Equilibrium Behavior of Granite under Dynamic Impact

Abstract

Stress equilibrium time is an important index to judge the homogeneity of rocks. In order to study the relationship between stress equilibrium time and crushing energy consumption before rock destruction, Hopkinson tests were conducted on granite specimens with different length-to-diameter ratios. In this paper, by studying the size and strain rate effects of rocks, five different sizes of granite specimens with different aspect ratios were prepared and Hopkinson impact tests were conducted under four strain rate conditions. Data analysis and processing using the three-wave method to investigate the stress uniformity of granite specimens under impact loading. The energy balance factor was introduced to compare and analyze the stress equilibrium time of five kinds of long-diameter granite specimens, and it was found that the stress equilibrium time of rocks with the same length–diameter ratio decreased with the increase of loading strain rate, while the granite specimens with length–diameter ratio of 0.8 showed a better stress equilibrium time. In order to better find the aspect ratio and loading strain rate that can crush better and maintain a long equilibrium time, the energy consumption of rock crushing is further analyzed. The energy dissipation of granite specimens with loading strain rate of 156.8 s−1 and 253.2 s−1 was found to be more concentrated, and the energy dissipation rate was stable at about 48%. Subsequently, the relationship between stress equilibrium time and energy dissipation was established, and it was proved that the fastest growing time period of the energy dissipation curve was approximately equal to the rock stress equilibrium time, while the length-to-diameter ratio of the granite specimen that could better maintain the stress uniformity before rock crushing was 0.8 and the loading strain rate was 156.8 s−1.