滇中红层软弱围岩局部失稳及变形控制实践

研究目的:隧道穿越滇中红层这一特殊地质条件下的变形主要为局部塌方、支护结构开裂破坏,为确保类似工程的顺利实施和人员设备的安全,本文针对南华一号隧道穿越全风化、强风化泥岩地层出现的局部失稳、大变形问题,在现场调研和监控量测的基础上,分析其失稳断面的变形及应力特征,并结合数值模拟结果,提出控制围岩变形的有效措施。研究结论:(1)三台阶工法施工过程中,中、下台阶施工对围岩的扰动程度相对较大;(2)隧道开挖后,拱顶和拱肩处围岩压力随时间的变化趋势是先减小再趋于稳定,而拱腰处围岩压力随时间的变化趋势是先增大然后趋于稳定;(3)采取局部布置锚杆、局部围岩注浆加固、施作锁脚锚杆等控制措施,可有效控制局部围岩失稳及围岩变形,相关措施可为今后类似工程提供借鉴和指导作用。

Local Instability and Deformation Control Practice of the Weak Surrounding Rock in Red Beds in Central Yunnan Province

Research purposes:The deformation of the tunnel through the central Yunnan red layer is mainly caused by local collapse and the cracking and failure of the support structure.Based on the field investigation and monitoring measurements,the characteristics of local instability and large deformation during the construction of Nanhua No.1 Tunnel crossing the fully weathered and strongly weathered mudstone stratum were studied,and the deformation and stress characteristics of the unstable section were analyzed.Combined with numerical simulation,effective measures to control deformation of surrounding rock were subsequently proposed.Research conclusions:(1)During the process of tunnel excavation with the three-step construction method,the construction of the middle and lower steps has relatively large disturbance to the surrounding rock.(2)After tunnel excavation,the radial pressure of surrounding rock at the tunnel vault and shoulder decreases firstly and then stabilizes gradually,while the pressure at the tunnel waist increases firstly with time and then stabilizes.(3)The counter-measures such as local arrangement of anchor bolts,local grouting to strengthen surrounding rock and application of locking anchor bolts can effectively control instability and deformation of the surrounding rock.The related measures can be used as reference and guidance for other similar projects in the future.