杆岩耦合作用下深埋隧洞围岩稳定性主控因素及支护优化研究

Study on Main Controlling Factors of Surrounding Rock Stability and Support Optimization of Deep-buried Tunnels under the Coupling Action of Anchor Bolts and Rocks

由于深埋隧洞围岩显著的流变特点,其变形范围及洞壁位移通常在施作初期支护一段时间后才趋于稳定,因此研究锚杆支护后隧洞围岩变形范围及其洞壁位移量将为支护参数优化及预留开挖量提供重要的理论依据。文章通过建立预应力锚杆与隧洞围岩的相互作用力学模型,分析了杆体与围岩相对位移为零的中性点位置及其最大轴力值。基于锚杆中性点理论,推导了工程扰动、锚杆预应力和孔隙水压耦合作用下隧洞围岩变形范围以及洞壁位移的计算公式。结果表明:多因素耦合作用下隧洞围岩变形范围及洞壁位移随工程扰动和孔隙水压的增大而逐步增加,随锚杆预应力的增大而减小。最后,以秦岭某引水隧洞为工程背景,利用所提出的理论公式计算了该隧洞极不稳定区段围岩变形范围及洞壁位移量,进而对原开挖及支护方案进行了优化。

Due to significant rheological characteristics of the surrounding rocks of deep-buried tunnels,the rock deformation range and the displacement of the tunnel wall usually become stable after installing the primary support for some time.Therefore,researching the deformation range of tunnel surrounding rocks and the displacement of tun⁃nel walls after supporting with the anchors will provide important theoretical basis for optimization of support param⁃eters and reserved excavation volumes.In the paper,a mechanical model of interaction between pre-stressed anchor bolt and surrounding rock is established to analyze the position of neutral point and the maximum axial force,where the relative displacement between the bolt rod and surrounding rock is zero.The calculation formulae of the tunnel rock deformation range and the tunnel wall displacement under the coupling action of excavation disturbance,bolt pre-stress and pore-water pressure are deduced based on the neutral point theory of the bolt.The results show that the deformation range of tunnel surrounding rocks as well as the displacement of tunnel walls gradually increase with increase of the excavation disturbance and pore-water pressure while reduce with increase of the bolt pre-stress.Fi⁃nally,the deformation range of the tunnel surrounding rocks and the displacement of tunnel walls in the extremely un⁃stable tunnel section are calculated according to the proposed theoretical formulae to optimize the original excavation and support schemes,by taking a water diversion tunnel in the Qinling Mountains as engineering background.