基于有限元的三台阶仰拱初支技术

Initial Support Technology of Three-step Inverted Arch Based on Finite Element Method

为了解决大断面软岩隧道的软弱破碎围岩径向位移增速快,开挖后初期支护结构不能尽早发挥作用,极大可能导致围岩失稳、发生安全事故等问题,以新建蒙西—华中煤运通道马湾隧道为依托工程,以优化改进后的三台阶仰拱初支开挖法进行施工,并借助有限元软件建立隧道模型,对三台阶仰拱初支开挖法进行数值模拟分析。最终结果表明:按优化改进后的三台阶仰拱初支开挖法能实现仰拱初支紧跟、隧道初期支护整体尽早封闭成环,做到了开挖、支护工序衔接紧凑;隧道最大竖向变形为33.2mm,拱顶沉降及周边收敛随开挖步的变化均处于施工安全范围内;拱腰初支最大拉应力为1.08MPa,拱顶最大压应力为13.8MPa,均符合施工要求,为大断面软岩隧道施工提供一种更安全的新方案。

In order to solve the problem that the radial displacement of soft broken surrounding rock in large cross-section soft rock tunnel increases rapidly,and the initial support structure cannot play a role as soon as possible after excavation,which may greatly lead to instability of surrounding rock and safety accidents.Based on the newly built Mawan tunnel of Mengxi-Huazhong coal transportation corridor,the construction is carried out by optimizing and improving the three-step inverted arch initial support excavation method.The tunnel model is established by finite element software,and the numerical simulation analysis of the three-step inverted arch initial support excavation method is carried out.The final results show that:according to the optimized and improved three-step inverted arch initial support excavation method,the initial support of the inverted arch can be closely followed,and the initial support of the tunnel can be closed as soon as possible,so that the excavation and support process are compact.The maximum vertical deformation of the tunnel is 33.2 mm,and the changes of vault settlement and surrounding convergence with excavation steps are within the scope of construction safety.The maximum tensile stress of the initial support of the arch waist is 1.08 MPa,and the maximum compressive stress of the vault is 13.8 MPa,which are in line with the construction requirements,and provide a safer new scheme for the construction of large-section soft rock tunnel.