轴向冲击下锚固锚杆变形与应力特征分析

Deformation and stress characteristics of anchor bolt under axial impact

  • 摘要: 冲击地压因其特有的易发、多发、难防治特征,成为影响煤矿生产最为突出的动力灾害之 一,其中以回采巷道冲击地压发生最为显著。 冲击地压巷道动力显现过程中,锚杆支护系统往往伴 随着一定的动载冲击作用,关于锚杆支护系统在动载冲击作用下的力学响应研究对冲击地压防治 具有重要意义。 为研究锚杆支护系统中杆体不同位置对冲击载荷的响应规律,选择煤矿常用的 500 号左旋无纵肋螺纹钢锚杆,沿锚杆轴向不同位置粘贴应变片,利用锚杆力学性能综合试验台对 支护单元施加轴向冲击载荷,分别采用激光位移传感器和动态应变仪采集锚杆杆体及不同位置变 形数据,分析杆体变形规律及时序特征;利用 LS-DYNA 数值分析软件再现轴向冲击载荷下锚杆受 载变形过程,分析锚杆不同位置的应力和变形特征。 结果表明:1 在 171 kN 初始拉伸载荷状态 下,10 kJ 轴向冲击能量使锚杆端部载荷瞬时增加至 438 kN,此后处于振荡衰减状态,衰减速度逐 渐增大。 2 10 kJ 轴向冲击能量导致锚杆在 30 ms 内振荡拉伸和收缩,并最终产生 28.39 mm 的拉 伸塑性变形。 3 锚杆杆体不同位置的变形受应力波的界面反射效应影响较大,塑性变形大部分产 生在锚杆自由段,且距离锚固段与自由段分界面越近杆体塑性变形量越大。 4 锚杆不同位置对冲 击载荷响应具有时序性,拉伸和收缩变形均由杆尾向锚固端头依次响应。 5 锚固作用可有效约束 锚杆变形,吸收冲击产生的应力波,随着锚固深度加大,锚杆应力和变形响应幅值显著减小。

     

    Abstract: Coal burst has become one of the most prominent dynamic disasters affecting coal mine production because of its unique characteristics of easy occurrence,frequent occurrence and difficult in prevention and control. During the dynamic appearance of coal burst in roadway,the bolt support system is often accompanied by a certain impact of dynamic load. The research on the mechanical response of the bolt support system under the impact of dynamic load is of great significance to the prevention and control of coal burst. In order to study the response of different positions of the rod body to the impact load in the bolt support system,the No.500 lefthand nonlongitudinal bolt threaded steel bolt commonly used in coal mines is selected,the strain gauge is pasted at different positions along the axial direction of the bolt,and the axial impact load is applied to the support unit by using the comprehensive testbed of bolt mechanical properties. Laser displacement sensor and dynamic strain gauge are used to collect the deformation data of bolt and different positions respectively,and the deformation and time sequence characteristics of bolt are analyzed. The LSDYNA is used to reproduce the loading deformation process of bolt under axial impact load,and the stress and deformation characteristics of bolt at different positions are analyzed. The results show that ① under the initial tensile load of 171 kN,the 10 kJ axial impact energy instantaneously increases the load of the bolt to 438 kN,and then it is in the state of oscillation attenuation,and the attenuation speed gradually increases. ② The 10 kJ axial impact energy causes the bolt to oscillate,stretch and shrink within 30 ms,and finally produces 28.39 mm tensile plastic deformation. ③ The deformation of different positions of the bolt is greatly affected by the interface reflection effect of stress wave. Most of the plastic deformation occurs in the free section of the bolt. The closer it is to the interface,the greater the plastic deformation of the bolt. ④ The response of different positions of bolt to impact load is sequential,and the tensile and shrinkage deformations respond successively from the bolt tail to the end. ⑤ The anchoring effect can effectively restrain the bolt deformation and absorb the stress wave generated by impact. With the increase of anchoring depth,the amplitude of bolt stress and deformation response decrease significantly.

     

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