Analysis of Energy Properties and Failure Modes of Heat-Treated Granite in Dynamic Splitting Test

Dynamic Brazilian disc (or splitting) tests were carried out to study the characteristics of energy dissipation and failure behavior of heat-treated granite under impact loading. Six groups of granite samples were treated at the temperatures of 25 degrees C, 100 degrees C, 300 degrees C, 500 degrees C, 700 degrees C, and 900 degrees C, respectively. Each group of heat-treated samples was tested with three impact velocities of 5.4, 7.7 and 13.7 m/s in a modified split Hopkinson pressure bar. An average change rate of incident energy (ACRIE) was proposed to characterize the loading rate effect. The effects of treatment temperature and ACRIE on the energy dissipation and the failure patterns of samples under impact loading were investigated. The results show that the energy dissipation of the granite decreases with the increase of treatment temperature but increases with the increase of the ACRIE. A rise in treatment temperature or ACRIE may lead to smaller size and greater number of sample fragments. The effect of treatment temperature becomes more obvious as the ACRIE increases. The energy utilization ratio of the granite is generally less than 30 % and has an opposite effect when compared to the loading rate. In addition, the dynamic tensile strength of the samples increases almost linearly with the transmitted wave energy. These studies also indicate that the resistance of rock against tensile failure can be well characterized from the perspective of energy dissipation.