Failure characteristics and anti-impact mechanism of prestressed anchoring coal under impact load

With the aim of elucidating the dynamic response of anchorage support structure in deep roadway, in the study, we examined the dynamic response of anchored coal under different pre-tightening forces by using the split Hopkinson test system. The stress-strain relationship and energy dissipation characteristics of anchored coal were elucidated, and the dynamic anti-impact mechanism of anchored coal was revealed. According to the analysis results, with the rising of the pre-tightening force, the peak strength of the sample is up to 40.9 MPa. In the case that the incident energy is basically the same, the reflection energy decreases significantly at rising preload, and the increase of transmission energy is greater than that of dissipation energy. The plastic strain is gradually generated on the impact side of the anchorage sample, and the crack gradually expands to the side of the transmission rod. Under the small preload, the “X” symmetrical crack is generated in the anchorage attachment of the anchoring coal body. When the preload is applied to 2.3 kN, the tensile crack gradually dominates. The larger the preload is, the more the tensile crack position deviates from the center of the bolt axis. Under the continuous compression of the wave front, the prestressed zone in the middle of the coal body is greatly compressed, and the stress rising zone is formed far away from the impact side. The stress redistribution eventually leads to the damage of the anchorage interface. When the pre-tightening force of the bolt is large, the central anchorage zone can still maintain a certain anchorage performance and impact toughness, showing obvious ductile failure characteristics and higher energy dissipation capacity. The research results provide a certain experimental basis for elucidating the regulation of stress wave energy distribution and crack propagation path.