玉磨铁路软岩浅埋隧道冒顶机理分析及防治措施

Analysis of Roof Fall Mechanism and Prevention Measures for Shallow Tunnels in Soft Rock on Yumo Railway

以国家一带一路重点项目云南玉磨铁路曼勒1号隧道浅埋段为依托,结合现场施工中遇邻近断层破碎带隧道塌方冒顶事故,研究了西南地区软岩浅埋隧道冒顶防治措施.采用MIDAS GTS NX有限元软件建立邻近断层破碎带的浅埋隧道模型,依据隧道冒顶机理分析及有限元模型模拟分析结果,提出浅埋隧道支护方案.研究结果表明:在强化支护措施后浅埋隧道拱顶沉降及拱腰收敛均在允许变形量范围内;围岩塑性区主要集中在拱顶两侧及拱腰处,右侧塑性区范围较大,产生塑性破坏的风险较大.围岩最大主应力及初支最大主应力显示,隧道右侧拱腰处初支出现应力集中的风险较大,围岩出现应力集中后会导致受压破坏区和受剪破坏区逐渐增加,当两种破坏区域逐渐重合后围岩会产生塑性破坏,最终导致塌方冒顶.根据模拟计算及现场实际工况,本文提出在隧道塌方冒顶段采用“大管棚+小导管”超前支护组合、洞内全环I18型钢钢架附加临时横撑的支护防治方案,为了提高围岩稳定性对断层破碎带进行注浆加固,经现场施作后防治效果良好,为今后类似工程提供指导.

Relying on the shallow buried section of the Manle No.1 tunnel of Yunnan Yumo Railway,as a key project of The One Belt One Road,combined with the collapse and roof caving of adjacent fault fracture zone tunnels during on-site construction,the roof caving prevention measures for shallow tunnels in soft rock in the southwest were studied.The MIDAS GTS NX finite element analysis software was used to establish a shallow tunnel model adjacent to the fault fracture zone.Based on the tunnel roof fall mechanism analysis and the finite element model simulation analysis results,the shallow tunnel support scheme was proposed.Research indicates:After strengthening the support measures,the settlement of the shallow tunnel vault and the convergence of the arch waist are within the allowable deformation range.The plastic zone of the surrounding rock is mainly concentrated on both sides of the vault and the arch waist.The plastic zone on the right side is larger,and the risk of plastic failure is higher.The maximum principal stress of the surrounding rock and the maximum principal stress of the initial support,there is a greater risk of stress concentration in the initial support at the arch waist of the tunnel on the right side.The stress concentration in the surrounding rock will cause the compression failure zone and shear failure zone to gradually increase.When the two failure areas gradually overlap,the surrounding rock will produce plastic failure and eventually lead to the collapse of the roof.According to the simulation calculation and the actual working conditions of the site,this paper proposed a prevention and treatment plan of adopting the"large pipe shed+small pipe"advanced support combination in the tunnel collapse section and the full loop I18 steel frame with temporary transverse bracing in order to improve.The stability of the surrounding rock was used to reinforce the fractured zone by grouting.After on-site construction,the prevention and control effect is good,providing guidance for similar projects in the future.