不等跨双向10车道四连拱隧道设计及施工方法

针对软弱围岩条件下大跨度多连拱隧道施工过程中荷载转换和施工工序复杂，施工风险高等问题，介绍观音岩四连拱隧道设计施工方法，提出“先主后辅”的施工工序，并应用数值模拟及现场监测手段，分析四连拱隧道多洞施工、主辅洞开挖相互扰动下，围岩与结构的反应、现场施工工序的可行性以及支护结构的安全性。结果表明： 1）采用先开挖主洞后开挖辅洞的施工工序是安全可行的； 2）多连拱隧道施工，洞室受到的开挖扰动次数越多，结构受力越复杂，建设过程需重点关注先行洞室受到后行洞室施工扰动带来的安全风险； 3）相邻洞室间的施工扰动影响要远大于不相邻洞室。现场实施效果表明，隧道施工过程中围岩变形稳定、支护结构安全，不等跨双向10车道四连拱隧道设计及施工方法可行。

Design and Construction Method of Two Way Ten Lane Four Arch Tunnels with Different Spans

Many issues arise when constructing multi arch tunnels in weak surrounding rock conditions, including difficult load conversion and construction techniques as well as high construction risks. Therefore, the design and construction methods of Guanyinyan tunnels in Changsha are discussed, and the construction procedures of the main tunnel and the auxiliary tunnels are proposed. The interaction response of the surrounding rock and structure, feasibility of the construction process, and safety of the support structure under the conditions of the multitunnel construction of a four arch tunnel and interaction between main and auxiliary tunnels are analyzed using numerical simulation and onsite monitoring methods. The results show the following. (1) The construction process of the main tunnel and then the auxiliary tunnels is safe and feasible. (2) The construction of a multi arch tunnel will increase the cavern′s excavation disturbances and complicate the structural stress, and attention should be paid to the tunnel risk posed by later excavated tunnels. (3) The construction disturbance between adjacent caverns has a more significant impact than that between separated caverns. The onsite implementation results show that the surrounding rock deformation is stable and the supporting structure is safe during the tunnel construction process, confirming the feasibility of the design and construction method of two way ten lane four arch tunnels with different spans.