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不同預靜載水平下錨固結構擾動承載特性研究

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

  • 摘要: 動載擾動作用是影響深部煤炭資源開采過程中圍巖穩定性的重要因素,分析擾動荷載作用下錨固結構的承載力學響應對巷道支護具有重要意義,本文采用FLAC-PFC耦合的數值模擬方法對錨固試件進行了拉拔數值試驗研究,分析了不同預靜載水平下動載擾動對錨固結構力學特性、能量演化規律、破壞特征及損傷規律的影響。研究結果表明:(1)動載擾動作用后,錨固試件峰值拉拔強度及對應位移均低于靜載錨固試件,且隨著預靜載水平的增大,峰值拉拔強度和承載能力均逐漸降低。建議將擾動載荷的上限應力控制在80%的靜載峰值應力之下,以避免擾動損傷累積導致的擾動破壞。(2)錨固試件的聲發射振鈴計數和累計振鈴計數整體上呈平靜期、穩定增長期和加速增長期的演化規律。累計振鈴計數隨著預靜載水平的增大而增大。(3)預靜載水平的增大導致錨固試件內部彈性能逐漸減小,耗散能逐漸增大,且彈性能始終大于耗散能。耗散能占比與預靜載水平呈正相關。基于能量演化規律,可將彈性能耗比曲線在擾動后斜率由平穩轉變為加速增長這一變化,作為錨固結構失穩破壞的前兆特征。(4)隨著預靜載水平增大,錨固試件內部力鏈數逐漸減少,裂紋由試件中上部逐漸向深部延伸。(5)隨著預靜載水平增大,錨固試件加載過程中初始損傷和擾動損傷均增大,錨固結構更容易失穩破壞。研究成果可為動載擾動作用下錨桿支護設計提供理論參考。

     

    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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