防冲吸能锚杆(索)的静动态力学特性与现场试验研究

针对冲击危险巷道锚杆支护结构破坏特征及冲击载荷对锚杆–围岩支护系统的特殊要求,设计研发了新型防冲吸能锚杆(索)。基于塑性弯曲理论分析了吸能锚杆(索)的吸能原理,利用自主设计的静–动加载试验系统,进行吸能锚杆(索)的静力拉伸试验与冲击拉伸试验。结果表明:吸能锚杆(索)在拉伸过程中六角管衬里被挤压变形,同时给摩擦圆柱提供滑移阻力,六角管的管壁厚度、套筒内径及摩擦圆柱直径三者的装配参数对吸能阻力具有重要影响;无论是静力拉伸还是冲击拉伸,吸能锚杆(索)的轴力–位移曲线均存在轴力初始增长、轴力平稳和轴力突增—平稳3个阶段;在轴力平稳阶段内锚杆杆体基本处于弹性状态,摩擦滑移结束后,锚杆杆体开始受力屈服;吸能结构在吸收能量的同时很好的延迟或减缓了锚杆杆体受力屈服。与普通锚杆相比,吸能锚杆(索)具有良好的"自保护性"与"冲击适应性"。现场试验表明,吸能锚杆(索)能够有效削弱冲击能对巷道围岩的作用。

Static and dynamic mechanical properties of energy absorption bolts (cable) and field tests

In view of the failure characteristics and the special requirements of bolts used in bump-prone roadways, the energy-absorption anchor (cable) is invented. The energy absorption principle of the energy-absorption anchor (cable) is analyzed based on the plastic bending theory, and the static tension and impact tension tests are carried out by use of the independently designed static and dynamic loading test system. The test results show that the hex pipe of energy absorption anchor (cable) is squeezed and deformed, and then slip resistance for friction cylinder is produced during the whole tension process. The geometric parameters and the assembly forms of hex pipe and friction roller have important influences on the working resistance. Under whether static tension or impact tension, the load-displacement curves both consist of three stages, initial axial force growth stage, axial force stationary stage and axial force spurt-stationary stage. The rod body of anchor is basically in the elastic state at the axial force stationary stage, and the bolt begins to yield when the action of friction and sliding is completed. The energy absorption action of energy-absorbing structure delays or slows down the yielding of bolt effectively. Compared with the ordinary bolt, the energy absorption anchor (cable) possesses better self-protection and self-adaptability. The field tests show that the energy-absorption anchor (cable) can effectively weaken the effect of the impact energy acting on the surrounding rock of roadways.