Accumulated damage failure mechanism of anchoring structures under cyclic impact disturbance

Cyclic impact induces ongoing fatigue damage and performance degradation in anchoring structures, serving as a critical factor leading to the instability of deep roadways. This paper takes the intrinsic spatiotemporal relationship of macro-microscopic cumulative damage in anchoring structures as the main thread, revealing the mechanism of bearing capacity degradation and progressive instability of anchoring structure under cyclic impact. Firstly, a set of impact test devices and methods for the prestressed solid anchor bolt anchoring structure were developed, effectively replicating the cyclic impact stress paths in situ. Secondly, cyclic impact anchoring structure tests and simulations were conducted, which clarifies the damage evolution mechanism of the anchoring structure. Prestress loss follows a cubic decay function as the number of impacts increases. Under the same impact energy and pretension force, the impact resistance cycles of extended anchoring and full-length anchoring were increased by 186.7% and 280%, respectively, compared to end anchoring. The rate of internal damage accumulation is positively correlated with impact energy and negatively correlated with anchorage length. Internal tensile cracks account for approximately 85%. Stress transmission follows a fluctuating pattern. Compared to the extended anchoring, the maximum vibration velocity of the exposed end particles in the full-length anchoring was reduced by 59.31%. Damage evolution exhibits a pronounced cumulative mutation effect. Then, a three-media, two-interface mechanical model of the anchoring structure was constructed. It has been clarified that the compressive stress, tensile stress, and oscillation effect arising from rapid transitions between compression and tension are the primary internal factors responsible for the degradation of the anchoring structure’s bearing capacity. Finally, the progressive instability mechanism of the anchoring structure under cyclic impact was elucidated. The mutual feedback and superposition of media rupture, interface debonding, and bearing capacity degradation result in overall failure. The failure process involves stages dominated by oscillation-compression, tensile stress, and compression failure. A targeted control strategy was further proposed. This provides a reference for maintaining the long-term stability of deep roadways under dynamic impact loads.