Experimental investigation on effect of loading rate on fracture behavior of coal-seam roof rock

• Published in: Energy exploration & exploitation Vol. 41; no. 5; pp. 1746 - 1761
• Main Authors: Chen, Lichao, Lyu, Shuaifeng, Guo, Zhang, Xiao, Yuhang
• Format: Journal Article
• Language: English
• Published: London, England SAGE Publications 01.09.2023; Sage Publications Ltd; SAGE Publishing
• Subjects: Coal mining; Ductile fracture; Ductile-brittle transition; Energy absorption; Energy dissipation; Fracture mechanics; Fracture toughness; Gravel; Load distribution; Loading rate; Optimization; Rocks; Sandstone; Seams; Split Hopkinson pressure bars; hydraulic fracturing; fracture behavior; Coal-seam hard roof; loading rate; Jungar mining area
• ISSN: 0144-5987; 2048-4054
• DOI: 10.1177/01445987231173098

The fracture behavior of coal-seam roof rock in coal mining is a key and controlling factor for the mode optimization of the artificial roof caving. However, the fracture mechanism of roof rock under loading is not clear. In the work, the split Hopkinson pressure bar (SHPB) experiment was carried out using semicircular bending samples from the sandstone of coal-seam roof rock in the Junger mining area of Inner Mongolia at the loading rate of 0.35–3.78 GPa·m0.5·s−1, and the dynamic fracture behavior and energy dissipation mechanism of samples under different loading rates were investigated. The result shows that the dynamic stress–strain process of the hard roof rock includes four stages: linear instantaneous compaction, linear elastic compression, failure, and fracture extension, in which the failure forms changes from brittle fracture to ductile fracture with the increase of loading rate. The mode I fracture toughness increases linearly under confining pressure. In addition, the propagation orientation of induced fractures is parallel to the loading direction, and the gravel in the samples can inhibit fracture extension, resulting in changing the fracture extension path. Further, the energy absorption efficiency of the samples during the fracture process decreases with the increase in the loading rate.