Effect of thermal treatment on energy dissipation of granite under cyclic impact loading

High temperature treatment causes thermal damage to rocks in deep mining. To study the thermal effect on the energy dissipation of rocks during the dynamic cyclic loading, cyclic impact loading experiments of heat-treated rocks were carried out using the splitting Hopkinson pressure bar (SHPB) experimental system. The correlations among the energy dissipation, energy dissipation rate, impact times, accumulated absorbed energy per volume, failure mode and temperature were analyzed. The results show that the reflected energy under the first impact increases and finally exceeds the absorbed energy when the temperature increases; however, the total reflected energy decreases above 200 °C. The absorbed energy under the first impact and the total absorbed energy all decrease as the temperature increases, the rates of which decrease accordingly. And the same phenomenon appears for the transmitted energy and the rate of the transmitted energy. On the contrary, the rate of the reflected energy increases with the rising temperature. When the temperature increases, the fewer impact times are needed to destroy the sample. In addition, the failure modes are different when the rock is treated at different temperatures; that is, when the temperature is high, even though the absorbed energy is low, the sample breaks into powder after several impacts.