Abstract: 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.

Key words:  fourarch tunnel, unequalspan structure, partition wall; construction process, structural safety