Macro-Meso Fracture and Instability Behaviors of Hollow-Cylinder Granite Containing Fissures Subjected to Freeze-Thaw-Fatigue Loads

Rock structural deterioration induced by coupled freeze-thaw and stress disturbance are a great concern for jointed rock mass during rock constructions in cold regions. Previous studies focused on fracture evolution of intact rock or flawed rock under freeze-thaw-static loads, but the coupling effect of freeze-thaw and cyclic loads on the pre-flawed hollow-cylinder rock is not well understood. This work investigated the influence of freeze-thaw on rock microstructure change and fatigue mechanical behaviors. Testing results show that rock strength, volumetric strain, and lifetime decrease with increasing F-T number. The stiffness degradation caused by cyclic loads is also impacted by the previous freeze-thaw damage. Additionally, the AE ring count and energy count decrease with the increase of F-T treatment. Large fracture signals are captured for rock that has smaller F-T cycles and at the stress-increasing moment. The AE b-value increases with F-T cycles, and it decreases rapidly near rock failure. Spectral analysis indicates that large-scaled cracking is prone to form for a sample having high F-T cycles. Moreover, 2D CT images reveal the differential crack network pattern at rock bridge segments and how it is affected by the previous freeze-thaw damage. The crack coalescence and hole collapse patterns and the associated structural deterioration of the rock bridge segment are obviously influenced by the F-T treatment.

Automated summary

This study investigates the influence of freeze-thaw on rock microstructure change and fatigue mechanical behaviors. The results show that rock strength, volumetric strain, and lifetime decrease with increasing freeze-thaw cycles. The stiffness degradation caused by cyclic loads is also impacted by previous freeze-thaw damage. Additionally, the AE ring count and energy count decrease with the increase of freeze-thaw treatment, and large fracture signals are captured for rock that has smaller freeze-thaw cycles.