Abstract:
Dynamic load disturbance is an important factor affecting the stability of surrounding rock during deep coal mining. It is crucial to analyze the bearing capacity response of anchorage structures under varying disturbance loads to ensure effective roadway support. In this study, the FLAC–PFC (Fast lagrangian analysis of continua–Particle flow code) coupled numerical simulation method was used for the pull-out numerical test of anchorage specimens, and the influence of dynamic load disturbance on their mechanical characteristics, energy evolution law, failure characteristics and damage law were analyzed under varying pre-static load levels. The results showed that the pre-static load level had a significant effect on the disturbance-bearing capacity of the anchorage structure. When the pre-static load did not exceed the yield strength of the static load anchorage specimen, the peak pull-out strength and displacement were reduced by 4% and 7%, respectively, compared with the static load anchorage specimen (the pre-static load of anchorage specimen is 0), and the mechanical properties did not change significantly. When the pre-static load exceeded the yield strength, the accumulation of pre-static load damage led to a linear deterioration in the mechanical performance under dynamic load disturbance, and the peak strength and displacement decreased by 25% and 20%, respectively. In practical engineering, it is suggested that the upper limit stress of the disturbance load should be maintained at below 80% of the static load peak stress to avoid disturbance damage caused by the accumulation thereof. Overall, the evolution law of the acoustic emission and cumulative ringing counts of the anchorage specimens entailed the quiet, stable growth, and accelerated growth periods. The cumulative ringing count increased from
3309 to
4178 with increasing pre-static load levels. The increase in the pre-static load level led to a decrease in elastic energy and an increase in dissipation energy, and the former was invariably greater than the latter. The proportion of dissipated energy was positively correlated with the pre-static load level. Based on the law of energy evolution, the slope of the elastic energy consumption ratio curve can change from stable to accelerated growth after disturbance, which can be used as a precursory feature of instability and failure of anchorage structures. As the pre-static load level increased, the number of internal force chains decreased from
1098 to
1009, and the crack distribution range gradually extended from the upper part of the specimen to the inner part. The damage variable of the entire loading process of the anchorage specimen was defined, and the degree of damage under pre-static load was quantitatively analyzed. With increasing pre-static load levels, the initial damage and disturbance damage of the anchorage specimen increased during the loading process, and the anchorage structure became more prone to instability and failure.