Study on disturbance bearing characteristics of anchorage structure under different pre-static load levels

Dynamic load disturbance is an important factor affecting the stability of surrounding rock in the mining process of deep coal resources. It is of great significance to analyze the bearing capacity response of anchorage structure under disturbance load for roadway support. In this paper, the numerical simulation method of FLAC-PFC coupling is used to study the pull-out numerical test of anchorage specimens, and the influence of dynamic load disturbance on the mechanical characteristics, energy evolution law, failure characteristics and damage law of anchorage structure under different pre-static load levels is analyzed. The results show that : ( 1 ) After the dynamic load disturbance, the peak pull-out strength and corresponding displacement of the anchorage specimen are lower than those of the static load anchorage specimen, and with the increase of the pre-static load level, the peak pull-out strength and bearing capacity are gradually reduced. It is suggested that the upper limit stress of the disturbance load should be controlled below 80 % of the static load peak stress to avoid the disturbance damage caused by the accumulation of disturbance damage. ( 2 ) The acoustic emission ringing count and cumulative ringing count of the anchorage specimens show the evolution law of the quiet period, the stable growth period and the accelerated growth period as a whole. The cumulative ringing count increases with the increase of the pre-static load level. ( 3 ) The increase of pre-static load level leads to the decrease of elastic energy and the increase of dissipation energy in the anchorage specimen, and the elastic energy is always greater than the dissipation energy. The proportion of dissipated energy is positively correlated with the pre-static load level. Based on the energy evolution law, the slope of the curve of elastic energy consumption ratio can be changed from stable to accelerated growth after disturbance, which can be used as a precursory feature of the instability and failure of anchorage structure. ( 4 ) With the increase of pre-static load level, the number of internal force chains of the anchorage specimen gradually decreases, and the crack gradually extends from the upper part of the specimen to the deep part. ( 5 ) With the increase of the pre-static load level, the initial damage and disturbance damage of the anchorage specimen increase during the loading process, and the anchorage structure is more likely to fail. The research results can provide a theoretical reference for the design of bolt support under dynamic load disturbance.