大跨度公路隧道初期支护极限位移值的确定

Determination of Initial Displacement Limit of Large-span Highway Tunnel

为了判断隧道开挖过程中围岩的稳定性,选取隧道开挖支护过程中反映围岩应力状态变化的初期支护极限位移值作为判别的重要依据。随着大跨度公路隧道建设的日益增多,为保证其在开挖过程中围岩的稳定性,计算其初期支护极限位移,依据JTG D70—2014《公路隧道设计规范》,运用Hoek-Brown屈服准则,运用FLAC3D软件模拟单侧壁导坑法与双侧壁导坑法两种开挖方式,运用尖点突变理论计算特征值作为极限状态的判别依据,计算拱顶、拱腰、拱脚的极限位移值。通过统计分析得到:双侧壁导坑法可以有效限制拱顶沉降值,并限制拱腰处的收敛值;同时,明确两种开挖方法针对不同围岩级别、不同埋深的极限控制点及相应的取值范围。

In order to determine the stability of the surrounding rock during tunnel excavation,The initial support limit displacement value reflecting the stress state change of the surrounding rock during the tunnel excavation and support is selected as an important basis for the discrimination.With the increasing construction of large-span highway tunnels,to ensure the stability of surrounding rock during excavation,according to Desion Specification Traffic Engineering of Highway Tunnel(JTG D70—2014),using Hoek-Brown Yield Criterion,using FLAC3D software to simulate two excavation methods:singlesidewalk and double-sidewalk,using cusp catastrophe theory to calculate the eigenvalue as the criterion for judging the limit state,calculating the limit displacement value of dome,arch,and arch.Obtained by statistical analysis:Double sidewall guide pit method can effectively limit the value of dome settlement,and limit the convergence value at the arch;At the same time,it is clear that the two excavation methods are aimed at the limit control points of different surrounding rock levels and different buried depths and the corresponding range of values.