不同预静载水平下锚固结构扰动承载特性研究

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

  • 摘要: 动载扰动作用是影响深部煤炭资源开采过程中围岩稳定性的重要因素,分析扰动荷载作用下锚固结构的承载力学响应对巷道支护具有重要意义,本文采用FLAC-PFC耦合的数值模拟方法对锚固试件进行了拉拔数值试验研究,分析了不同预静载水平下动载扰动对锚固结构力学特性、能量演化规律、破坏特征及损伤规律的影响。研究结果表明:(1)动载扰动作用后,锚固试件峰值拉拔强度及对应位移均低于静载锚固试件,且随着预静载水平的增大,峰值拉拔强度和承载能力均逐渐降低。建议将扰动载荷的上限应力控制在80%的静载峰值应力之下,以避免扰动损伤累积导致的扰动破坏。(2)锚固试件的声发射振铃计数和累计振铃计数整体上呈平静期、稳定增长期和加速增长期的演化规律。累计振铃计数随着预静载水平的增大而增大。(3)预静载水平的增大导致锚固试件内部弹性能逐渐减小,耗散能逐渐增大,且弹性能始终大于耗散能。耗散能占比与预静载水平呈正相关。基于能量演化规律,可将弹性能耗比曲线在扰动后斜率由平稳转变为加速增长这一变化,作为锚固结构失稳破坏的前兆特征。(4)随着预静载水平增大,锚固试件内部力链数逐渐减少,裂纹由试件中上部逐渐向深部延伸。(5)随着预静载水平增大,锚固试件加载过程中初始损伤和扰动损伤均增大,锚固结构更容易失稳破坏。研究成果可为动载扰动作用下锚杆支护设计提供理论参考。

     

    Abstract: 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.

     

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