Broken Mechanism of the Bolt Tail and Applications of Anti-breaking Methods
LI Xibing, MA Shaowei, MA Chunde, LI Jinyue, GUO Yang
School of Resources and Safety Engineering, Central South University; Hunan Key Laboratory of Resources Exploitation and Hazard Control for Deep Metal Mines, Changsha 410083, China
Abstract: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.