隧道穿越大型充填溶洞超前支护方案研究

岩溶隧道在穿越高压富水溶腔时频发突水涌泥灾害,给施工安全和周围环境造成严重威胁。根据渝怀铁路某隧道穿越溶洞实际情况,分别对“超前小导管+帷幕注浆支护”和“管棚+帷幕注浆”2种超前支护方案进行数值模拟分析,对围岩变形特征和塑性区进行对比分析,结果表明:(1)管棚超前支护对控制拱顶围岩沉降、拱底围岩隆起以及周边收敛变形更有利;采用管棚超前支护比超前小导管支护围岩变形明显降低。(2)采用管棚超前支护比超前小导管支护的塑性区发展深度有效降低,更能保护围岩的稳定性。采用管棚超前支护成功通过了该隧道大型充填溶洞的高风险段,可为类似工程提供借鉴。

Research on Advance Support Scheme of Tunnels Crossing Large Filling Karst Cave

The frequent occurrence of gushing water and mud burst in the Karst tunnel crossing a high-pressure water-rich cavity poses a serious threat to construction safety and the surrounding environment.According to the actual conditions of a tunnel crossing a karst cave in Chongqing-Huaihua Railway,numerical simulation analyses are carried out on two advance support schemes,i.e.the"advance small duct+curtain grouting support"and"pipe shed+curtain grouting",and a contrastive analysis is carried out on the deformation characteristics of surrounding rock and plastic zones.The results show that:(1)The advance support of pipe shed is more advantageous to control settlement of the surrounding rock at the arch crown,the uplift of surrounding rock at arch bottom and peripheral convergence deformation;The deformation of surrounding rock with advance support of pipe shed is significantly lower than that with support of advanced small duct.(2)The development depth of plastic zones with advance support of pipe shed is effectively reduced in comparison with that with support of advance small duct,which can protect the stability of surrounding rock better.The tunnel was cut through the high-risk section of the large-scale filling karst cave successfully with advance support of pipe shed,which provides a reference for similar projects.