吸能防冲锚杆索-围岩耦合振动特征与防冲机理

为提高冲击危险巷道防冲支护的有效性,研发了由内置六角管衬里的吸能套筒、端部设有摩擦圆柱的螺纹钢锚杆、钢绞线锚索与锚杆尾部吸能装置组成的吸能锚杆索。将吸能锚杆索中吸能套筒的作用简化为设置在锚杆底部并联的弹簧与阻尼器,建立了吸能锚杆索-围岩在冲击载荷作用下的三维轴对称力学模型。对黏性阻尼围岩中吸能锚杆索与围岩耦合振动时锚杆顶部动力响应进行了解析研究,获得了锚杆顶部的位移阻抗函数的解析表达。结果表明:在相同频率的冲击载荷作用下,锚杆顶部位移振荡幅值随着围岩黏性阻尼、围岩强度、锚固长度以及锚杆底部阻尼的增加而衰减。采用吸能锚杆索支护时,吸能套筒能够吸收一部分作用在锚杆锚固岩体上的冲击能;后注浆全长锚固增强了支护系统抵抗纵向变形的能力;尾部吸能装置能够削减冲击波的发射拉伸作用;支护系统在冲击载荷作用下的稳定性得到显著提高。在此基础上,初步阐述了吸能锚杆索支护系统的缓冲-抗震-消波吸能防冲机理。

Coupling vibration characteristics of rock mass and energy-absorption bolt and its anti-impact mechanism

In order to improve supporting effectiveness of bump-prone roadways,the energy-absorption bolt was invented,which consists of energy absorption sleeve with built-in hex pipe,whorl-steel bolt with friction roller on the head,pre-stressed strand and energy absorption devices at bolt tail.Then the three-dimensional axis-symmetry model of energy-absorption bolt and surrounding rock affected by impact loads was established by simplifying the energy-absorption sleeve as spring and damper situated on the end of bolt parallelly.An analytical solution of displacement impedance function was obtained by analyzing the dynamic response of the bolt top under the coupling vibration of energy absorption bolt and surrounding rock with viscous damping.Then the parameter sensitivity analysis of three-dimensional axis-symmetric mechanical model was carried out.The results show that with the greater parameters such as viscous damping and strength of surrounding rock,anchored length and damping of energy-absorption bolt,the greater complex stiffness and resistance ability for deformation of supporting system can be achieved.Energy-absorption sleeve can absorb part of impact energy acting on bolted rock mass,the full length anchorage of post-grouting enhances the ability of supporting system to resist longitudinal deformation,absorption device at bolt tail can subduct the reflected tension effect of shock wave.The stability of the system under the action of impact load are improved significantly.And the cushioning,vibrations resistance and wave-absorbing mechanism of support system was revealed preliminary.