锚杆尾部断裂机制和防破断方法应用

 基于岩体弹性能释放对锚杆的冲击作用,采用冲击动力学中刚性块对杆轴向碰撞的应力解,推导出了锚杆断裂的4种围岩应力条件。在此基础上分析了岩石弹性模量、锚杆弹性模量、锚杆直径与岩石泊松比等因素对锚杆断裂的影响。分析结果显示:在这4种围岩应力条件中,杆头被一次冲断基本上是不可能的,由于其他几种锚杆断裂时的围岩应力条件很接近,所以在实际中锚杆尾部被一次冲断的可能性最高,这也印证了锚杆尾部容易断裂的观点;另外,锚杆断裂的围岩应力条件受岩石弹性模量、岩石泊松比、岩石密度、锚杆弹性模量、锚杆密度、锚杆直径等因素的影响,其中影响较大的是岩石弹性模量与锚杆弹性模量的比值、锚杆直径和岩石泊松比;锚杆尾部断裂的围岩应力条件对于改进锚杆形式、优化锚杆力学性质有理论指导意义。最后,以马路坪矿的巷道工程为例,说明了锚杆防破断方法的具体应用,收到了良好的效果,可以在实际工程中推广应用。

Fracture Mechanism of the Bolt Tail and Applications of Anti-breaking Methods

Based on the bolt impacted by the elastic energy of rock mass and the stress solution that a rigid block collides with rod along axially in impact dynamics is adopted; four stress conditions of rock mass are derived before the bolt is fractured. And on the basis, several factors, including elastic modulus of rock, elastic modulus of bolt, diameter of bolt, and Poisson's ratio of rock, are discussed. The analytical results show as follows: In four stress conditions of rock mass, it is impossible that bolt head is directly fractured, but the rest parts have high possibility. In addition, the rest bolts have the similar stress conditions of rock mass, therefore it has a high possibility that the bolt tail is directly fractured, it also confirms with the view that bolt tail is easily broken; Besides, before the bolt is fractured, the stress condition of rock mass is affected by several factors, including elastic modulus of rock, Poisson's ratio of rock, density of rock, elastic modulus of bolt, density of bolt, and diameter of bolt, among them elastic modulus of rock, elastic modulus of bolt, diameter of bolt, and Poisson's ratio of rock exert the greatest impact; the stress condition of rock mass before the bolt is fractured has the theoretical significance for improving the anchor form and optimizing mechanical properties of bolt. Finally, a tunnel engineering in the mine of Ma Luping is given to explain how to use the anti-breaking methods for bolt in practice and the ideal results are obtained; therefore these methods are able to be applied to the actual engineering.