Mechanical properties and impact resistance mechanism of anchor bolts under dynamic-static coupling conditions

Anchor bolt support is a commonly used surrounding rock control technology in deep underground engineering. To control the large deformation of surrounding rock under complex conditions, high prestress needs to be applied to the anchor bolts. Meanwhile, affected by mining disturbances, strong impacts, etc., the anchor bolts are in a working state of dynamic-static coupling. Therefore, studying the impact resistance performance and safety reserve of anchor bolts under different working load conditions is crucial for the support design of deep underground engineering. Based on this, the multi-functional dynamic-static coupling test system is self-developed. The dynamic-static coupling mechanical performance tests on Common Bolts (CB) and High-strength Bolts (HB) are conducted under initial forces of 0-200 kN. The dynamic-static coupling mechanical properties and impact resistance mechanism of anchor bolts are clarified. The test results show that: In terms of impact energy, under dynamic-static coupling conditions, the impact energy resisted by different anchor bolts exhibits the same attenuation law with the increase of initial force. In terms of energy absorption, the energy absorption capacity of anchor bolts is an inherent property and does not change significantly with load variations. Meanwhile, the single energy absorption of anchor bolts increases with the increase of initial force, resulting in a significant decrease in impact energy and a reduction in safety margin. Under initial forces of 0-200 kN, the maximum impact energy attenuation rates of CB and HB are 58.8% and 50.0%, respectively; the average total energy absorbed by CB and HB is 13.0×10⁴ J and 14.4×10⁴ J, respectively. The energy absorption coefficient demonstrates a “phased growth” characteristic of slow increase followed by rapid increase as the strength utilization rate increases. By comprehensive analysis, the impact-resistant and energy-absorbing mechanism of anchor bolts is clarified under dynamic-static coupling conditions. On this basis, the strength-energy dynamic-static coupling design concept for anchor bolts is proposed, and the bilinear prestress design model of anchor bolts under dynamic-static coupling conditions is established, which can provide new ideas for the safety control of dynamic disasters in deep underground engineering.