Energy Mechanism and Acoustic Emission Characteristics in Rock-Backfill Composite Structure Specimens under Multi-Level Cyclic Loads: Cement-Tailings Ratio Effect

• Published in: Minerals (Basel) Vol. 14; no. 7; p. 665
• Main Authors: Long, Dayu, Wang, Yu, Li, Changhong, Wu, Yunfeng, Hu, Yongyue
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.07.2024
• Subjects: Acoustic emission; Acoustic emission testing; Acoustic tracking; Acoustics; Backfill; Cement; Composite structures; Computed tomography; Concrete; Crack initiation; Crack propagation; Cracks; Curing; Cyclic loading; Cyclic loads; Deformation; Emission analysis; Energy absorption; Energy dissipation; Energy exchange; Fatigue cracking; Fatigue strength; Fatigue tests; Fracture mechanics; Load; Materials fatigue; Mechanical properties; Medical imaging; Mine tailings; Mines; Mining accidents & safety; Mining industry; Peak frequency; Pollution monitoring; Rock; Rocks; Shear; Shear strength; Shear tests; Stress-strain curves; Stress-strain relations; Tailings; United States > US
• ISSN: 2075-163X; 2075-163X
• DOI: 10.3390/min14070665

This study aimed to investigate the effects of the cement-tailings ratio (CTR) on the fatigue properties, acoustic emission (AE) activities, energy dissipation, and fracture patterns of rock-backfill composite structure (RBCS) samples. The investigation employed multi-level cyclic loading tests combined with acoustic emission monitoring and post-test CT scanning. The results indicated that the fatigue strength and fatigue lifetime of the RBCS samples initially increased and then decreased as the CTR was reduced from 1:4 to 1:12. The energy dissipation characteristics reflected the optimal energy absorption effect of the backfill at a CTR of 1:8. The AE ring counts/energy apparent skip phenomenon corresponded to the stress-strain curve from a dense to sparse pattern. The samples with CTRs of 1:4 and 1:8 showed a more significant increase in the peak frequency band at failure and released more energy. The fracture of the RBCS specimen was dominated by tensile cracking signals accompanied by some shear cracking signals. However, the proportion of shear signals was higher for samples with CTRs of 1:4 and 1:8. Similarly, the b value was smaller at failure. The 3D visualization images revealed that the fracture pattern of the RBCS was a mixed tensile-shear fracture, including shear fracture within the backfill, tensile cracking in the interface, and tensile-shear fracture within the rock. The volume and complexity of cracks increased and then decreased with decreasing CTR, i.e., from 1:4 to 1:12. The evolution of cracks probably involves internal backfill fracturing first, and then the fracture extends into the surrounding rock. A recommendation for the design of CTB was presented in this study to ensure the safety and stability of mine excavations.