西南地区岩溶富水隧道坍塌力学机理及处治措施

以云南玉溪至磨憨铁路曼勒一号隧道为依托，对西南地区岩溶富水隧道坍塌进行处治并预防，建立基于隧道坍塌机理的隧道坍塌力学计算模型，采用理论分析结合有限元计算软件MIDAS GTS NX模拟的方法分析了隧道坍塌段围岩及初支稳定性，并提出有效的处治措施。结果表明：坍塌段隧道模型拱顶沉降量为48.5 mm，拱腰水平收敛量为111.53 mm，围岩变形量较大，发生坍塌事故的风险较大；围岩塑性区出现在上中台阶掌子面，应变最大值为7.85×10-2，发生塑性破坏可能性较大；隧道坍塌段初支所受拉应力和压应力分别达到了19.68 MPa和17.89 MPa，根据铁路隧道设计规范抗拉极限强度为2.0 MPa，抗压设计强度为12.5 MPa，支护结构承受荷载过大易发生破坏。隧道施工现场地下水渗漏对砂泥岩地层围岩稳定性有重大影响，小范围溜塌最终导致大范围围岩失稳坍塌、初支破坏。根据现场实际工况，采用双层超前小导管补强支护对坍塌段进行加固，隧道坍塌段处治效果良好，为后续类似工程提供指导借鉴。

Collapse mechanism and treatment measures of karst water-rich tunnel in Southwest China

Relying on the Manle No. 1 Tunnel of Yunnan Yuxi-Mohan Railway, the collapse of the karst water-rich tunnel in the southwest was treated and prevented, a mechanical calculation model of tunnel based on the mechanism of tunnel collapse is established. Using theoretical analysis combined with finite element calculation software MIDAS GTS NX simulation method, the stability of surrounding rock and primary support of the tunnel collapse section is analyzed, and effective treatment measures are proposed. The results show that the vault settlement of collapsed section of tunnel model is 48.5 mm, the horizontal convergence of the arch waist is 111.53 mm, the surrounding rock deformation is large, and the risk of a collapse accident is greater. The plastic zone of surrounding rock appears in the middle step arch waist and tunnel face, and the maximum strain is 7.85×10-2, which means that plastic failure is more likely to occur. The initial tensile stress and compressive stress of the collapsed section of the tunnel reach 19.68 MPa and 17.89 MPa, respectively. The tensile stress is far greater than the specification requirement, and the compressive stress is close to the ultimate strength of bending and compression. The supporting structure is prone to damage when subjected to excessive loads. Groundwater leakage at the tunnel construction site has a significant impact on the stability of the surrounding rock of the sand and mudstone formation. A small-scale collapse will eventually lead to a large-scale collapse of the surrounding rock and The primary support will be destroyed. According to the actual situation, the collapse section is reinforced by the double-layer advance small pipe reinforcement support, and the treatment effect of the tunnel collapse section is good, which provides guidance for similar projects.