V级围岩隧道不同施工阶段拱顶极限位移研究

Research on Vault Ultimate Displacement at Different Tunnel Construction Stages in Surrounding Rock of GradeⅤ

现有的极限位移及其管理基准主要是针对普速铁路隧道断面在支护封闭后的工况,大多没有考虑隧道施工的阶段性。文章以现有V级围岩高速铁路隧道采用三台阶法施工为例,采用FLAC3D软件模拟不同施工阶段拱顶位移,通过尖点突变理论得到不同施工阶段的拱顶极限位移。结果表明,V级围岩隧道采用三台阶法施工时,上台阶开挖对隧道最终拱顶极限位移贡献率最大,中台阶次之,下台阶及仰拱段开挖几乎无影响;在50~300 m计算埋深条件下,V级围岩隧道同一施工阶段的拱顶极限位移与埋深都呈线性关系。同时采用灰关联分析了不同围岩参数对极限位移的敏感性,得到对拱顶极限位移影响程度由大到小的顺序为:围岩密度ρ、弹性模量E、粘聚力c、泊松比μ、内摩擦角φ。

The existing ultimate displacement and its management reference are mainly determined after the clo⁃sure of supporting structure of the common railway tunnel section,without considering the tunnel construction stages.Taking the existing high-speed railway tunnel which locates in surrounding rock of gradeⅤand adopts three bench method for example,it simulates the vault displacements in different construction stages by FLAC3D software,ob⁃tains the ultimate vault displacements in different construction stages based on cusp catastrophe theory.The results show that the ultimate vault displacements are affected by excavation of upper bench,middle bench,lower bench and invert in decending order and there is almost no effect by lower bench and invert excavation in the case of threebench construction in the surrounding rock of gradeⅤ;under the calculated buried depth of 50-300 m,the ultimate displacement at vault in the same construction stage has a linear relationship with the buried depth.The sensitivities of surrounding rock parameters to the ultimate displacements are analyzed by grey correlation,and the influence de⁃grees on the ultimate vault displacement are rock mass densityρ,elasticity modulus E,cohesive force c,poisson rateμand internal friction angelφin descending order.