Abstract: In order to study the instability and failure mechanism of roadway surrounding rock under dynamic load, the stress wave propagation law and spallation failure characteristics of pre-stressed end anchorage body under different impact pressures (0.2, 0.3, 0.4, 0.5, 0.6 MPa) are studied using SHPB test system. The spallation strength and strain rate of anchorage body specimen are calculated by graphical method, and a spallation damage model of anchorage body is established and verified by high-speed camera. The results show that the peak strain of stress wave decays exponentially under different impact pressures, and the spatial attenuation amplitude and attenuation index are positively correlated with the impact pressure. The spallation of the anchorage body specimen first occurs near the free end, and the spallation thickness increases gradually along the reflected wave propagation direction. When the impact pressure is above 0.3 MPa, a new spallation occurs in the middle of every two spallation surfaces of the test piece. In the range of 18−33 s⁻¹ strain rate, the effect of strain rate is dominant, and the spallation strength is up to 69 MPa. While the strain rate is 41 s⁻¹, the spallation strength decreases to 17 MPa. The free end of the anchorage body shows spallation closure after impacted by dynamic load, but spallation closure is not observed at the spallation position at the anchor end due to the residual cohesion at the anchorage interface.

Key words: dynamic load, anchorage body, stress wave attenuation, spallation, strain rate, damage mode