花椒箐软岩隧道变形规律与支护对策研究

Deformation Law and Supporting Countermeasures of Huajiaoqing Soft Rock Tunnel

软岩隧道施工过程中经常出现围岩挤出变形、衬砌变形侵限、支护结构断裂失稳等情况。以花椒箐软岩隧道为背景,运用数值分析软件模拟隧道环状开挖双台阶预留核心土法施工过程,分析变形机理并改进支护措施,采用“关键部位强化支护+高强锁脚锚杆支护+断面锚杆整体强化”新支护对策;模拟分析改进后支护效果,达到要求后予以采用,并进行现场变形监测。研究结果表明:花椒箐隧道变形是由两帮和拱脚的围岩在高应力影响下发生剪切破坏,导致了拱部整体下沉变形;模拟变形结果超出预警值,支护效果不佳;通过增加锚杆长度,增设锁脚锚杆等措施进行针对性优化;改进后模拟的拱顶、拱底、水平方向变形量较优化前分别减少了20.3%、15.2%、20%,均未超出预警值,优化效果显著;经现场监控量测验证表明,改进支护措施后,拱顶、拱肩和拱腰最大变形量分别为17、 3.67、3.02 cm,优化效果符合预期。

During the construction of soft rock tunnel,there are often extrusion deformation of surrounding rock,deformation limit of lining,fracture and instability of support structure and so on.Taking Huajiaoqing soft rock tunnel as the background,the numerical analysis software was used to simulate the construction process of double step reserved core soil method for circular excavation of tunnel,analyze the deformation mechanism and improve the support measures.Moreover,the new support countermeasures of“strengthened support at key parts+high-strength locking anchor bolt support+overall reinforcement of section anchor bolt”was adopted.The support effect after improvement was simulated and analyzed,which would be adopted after meeting the requirements,and the on-site deformation monitoring was also carried out.The research results show that the deformation of Huajiaoqing tunnel is the overall subsidence deformation of the arch caused by the shear failure of the surrounding rock of two sides and arch foot under the influence of high stress.The simulated deformation results exceed the early warning value and the support effect is poor.Targeted optimization was carried out by increasing the length of anchor rods and adding foot locking anchor rods.The deformation of arch crown,arch bottom and horizontal direction after improvement is reduced by 20.3%,15.2%and 20%respectively compared with that before optimization,which all doesn’t exceed the early warning value,and the optimization effect is remarkable.The field monitoring measurement shows that after improving the support measures,the maximum deformation of the arch crown,arch shoulder,and arch waist is 17 cm,3.67 cm and 3.02 cm respectively,and the optimization effect meets expectations.