Energy Dissipation Characteristics and Failure Patterns of Freeze-Thawed Granite in Dynamic Flexural Tension

Deformation and failure of freeze-thawed rocks under dynamic loads are of practical meaning in studying the stability of slopes and tunnels in cold regions. The rock failure process is essentially actuated by the transfer and transformation of energy. In this paper, the energy dissipation characteristics and failure patterns of freeze-thawed granite under dynamic loads were investigated. A split Hopkinson pressure bar (SHPB) system was used to conduct the experiments on semicircular bend (SCB) specimens subjected to 30, 60, 90, and 120 freeze-thaw (F-T) cycles. The results found that the incident energy, reflected energy, and dissipation energy were loading rate-dependent, while the transmitted energy was not correlated with the loading rate. The reflected energy accounted for the largest proportion (greater than 60%) of the incident energy. In addition, the energy reflection rate (ERR) decreased when the loading rate or porosity increased, whereas the energy dissipation rate increased when the loading rate or porosity increased. A model was established to predict the ERR and EDR evolution. Finally, the failure patterns of freeze-thawed granite under dynamic loads demonstrated that a higher loading rate caused a change in failure patterns, whereas a larger porosity led to greater fragmentation in the specimens.