考虑开挖面效应的黏结式锚杆锚固效应分析

Anchoring effect of fully-grouted bolt considering tunnel face effect

【目的】为简化计算,在针对全长黏结式锚杆-围岩支护相互作用方面的理论研究中,通常将围岩视为弹性体、将杆体视为刚性、或将锚杆与砂浆界面接触视为刚性,与实际不相符。【方法】针对于此,根据力学假定提出锚杆-围岩分层简化力学模型,基于岩体屈服准则与流动法则,采用应力平衡与位移协调方程,给出改进的考虑隧道开挖面效应下的锚杆-围岩作用弹塑性解,该解法可用于预测隧道锚杆的受力状态与支护效果。之后,依托隧道工程实例对该解法进行验证,探讨了界面剪切刚度、岩体峰后应变软化特性、锚杆托盘刚度对锚杆支护效应的影响。【结果】在分析中发现,围岩应变软化行为对锚杆支护效应影响较为显著,在锚杆支护设计中应考虑到围岩的应变软化行为。在高应力条件下,锚杆托盘刚度在一定程度上影响了锚杆的失效形式,当远端处于塑性区域内部时,增大锚杆界面剪切刚度可有效加强锚杆控制效果。【结论】研究提供的计算程序可对系统锚杆支护的整体支护效果进行有效预测,为支护结构设计提供理论支撑。

[Objective]Among the current theoretical analysis of the interaction between rock and fully-grouted rock bolt,for simplicity,the rock mass is usually regarded as the elastic material,or the bolt is regarded as rigid,the connection between the rock bolt and the grout is assumed as rigid,which is not consistent with the reality.[Methods]In order to overcome the deficiencies,in this paper,based on the dividing method for the rock mass and rock bolt,and the failure criterion and the flow rule,by adopting the equations for stress balance equation and the compatibility of displacement,an improved numerical solution for the interaction between the rock and bolt is proposed,which can be used to predict the stress state and supporting effect of bolts.[Results]Then the analytical method is verified by examples of actual tunnel engineering.The bolt effect affected by the shearing stiffness at the interface,the post-peak strain-softening characteristics of rock mass,and the stiffness of the end plate is investigated.[Conclusion]The result indicate:under squeezing conditions,the failure mode of the bolt is influenced by the stiffness of the end plate,if the far end of the rock bolt is in the plastic zone,the increase of the shearing stiffness can greatly improve the controlling effect of the bolt.