冲击地压煤矿巷道锚杆动力响应特征与破坏规律研究

    Study on dynamic response characteristics and damage law of anchor bolts in coal mine roadway under rock burst

    • 摘要: 针对深部煤矿巷道冲击地压灾害频发、锚杆支护动力响应机制不明确的问题,采用数值模拟与现场试验相结合的方法,系统分析了不同冲击韧性锚杆在动载荷下的力学响应特征及破坏规律;基于LS−DYNA软件建立锚杆冲击模型,模拟屈服强度500 MPa、冲击吸收功15~94 J的锚杆在20 ms等腰三角形载荷作用下的动态响应,通过分析锚杆的Mises应力分布、断口特征、位移变化及能量吸收规律,揭示冲击韧性对锚杆破坏模式的影响机制,并应用于唐口煤矿7307轨道巷锚杆支护设计中。研究结果表明:随着冲击韧性的增加,锚杆断裂时的Mises应力也会随之增加,断口颈缩现象显著增强;相同冲击载荷作用下,锚杆的冲击吸收功越高,断裂时的位移越大,要使冲击韧性高的锚杆在固定的冲击时间内断裂,需要施加高的冲击载荷;冲击载荷越高,锚杆在塑性变形阶段的变形率越大,导致锚杆在没有充分发挥变形能力的情况下断裂,就会出现锚杆的冲击韧性高而延伸率低的情况;锚杆的变形量随着距冲击载荷施加处距离的减少而增加,但是在距固定端1.5 m的范围内变化不大,进一步揭示了锚杆变形的局部效应,在距冲击点1.5~2.0 m范围内,变形量较1.0~1.5 m段增加50%,且塑性应变首先出现在固定端并向冲击点扩展,最终在螺纹段集中破坏。

       

      Abstract: Aiming at the problem of frequent occurrence of rock burst disaster in deep coal mine roadway and unclear dynamic response mechanism of anchor bolt support, we adopt numerical simulation and field test to systematically analyze the mechanical response characteristics and damage law of anchor bolts with different impact toughness under dynamic load; based on LS-DYNA software, the impact model of anchor bolts was established, and the dynamic response of anchor bolts with yield strength of 500 MPa and impact absorbed work of 15-94 J under 20 ms isosceles triangle load was simulated. By analyzing the Mises stress distribution, fracture characteristics, displacement change and energy absorption law of the anchor bolts, the mechanism of impact toughness on the damage mode of the anchor bolts was revealed, and applied to the design of anchor bolt support in Tangkou Coal Mine 7307 track roadway. The results show that with the increase of impact toughness, the Mises stress at anchor bolt fracture increases, and the fracture necking phenomenon is significantly enhanced; the higher the impact absorption work of the anchor bolt under the same impact load, the higher the displacement at fracture, to cause an anchor bolt with high impact toughness to break within a fixed impact time, high impact loads need to be applied. The higher the impact load the greater the deformation rate of the anchor bolt in the plastic deformation stage, resulting in the anchor bolt breaking without giving full play to the deformation capacity, there will be a high impact toughness and low elongation of the anchor bolt. The deformation of the anchor bolt increases with the decrease of distance from the impact load application, but it does not change much in the range of 1.5 m from the fixed end, the study further reveals the local effect of anchor bolt deformation, in the range of 1.5-2.0 m from the impact point, the deformation increases 50% compared with the section of 1.0-1.5 m, and the plastic strain firstly occurs in the fixed end and extends to the impact point, and finally destroys centrally in the threaded section.

       

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