Research on the design and mechanical properties of extended constant resistance energy-absorbing anchor bolts

To address the premature fracture of anchor bolts caused by the mismatched yielding distance between anchor bolts and hydraulic supports in the advanced support section of rock burst-prone roadways, an elongated constant-resistance energy-absorbing anchor bolt was designed—with its yielding distance specifically coordinated to match that of hydraulic supports. ABAQUS numerical simulation was utilized to investigate the mechanical characteristics of this novel anchor bolt under static loading, as well as under varying impact energies and impact velocities. A comparative analysis was further performed against the mechanical performance of conventional anchor bolts. The results reveal the following: Under static loading, the elongated constant-resistance energy-absorbing anchor bolt exhibits a fracture load of 160.6 kN, a fracture displacement of 523.2 mm, an elongation rate of 20.93%, and an energy absorption capacity of 69.7 kJ. Under impact velocities within 9 m/s, the impact velocity has little effect on the fracture load, elongation, and energy absorption of constant-resistance energy-absorbing bolts, while the impact resistance time exhibits a nonlinear decreasing trend with increasing impact velocity. Under both static and dynamic loading conditions, the extended constant-resistance energy-absorbing bolt exhibits superior impact resistance and can effectively address the problem of premature bolt fracture caused by the mismatch between the bolt yielding distance and that of the hydraulic support in the three-level energy-absorbing support system. The findings provide a new perspective for bolt design.