Study on Stress Mechanism and Countermeasure of Multi-Arch Tunnel without Middle Drift

The multi-arch tunnel without middle drift is the latest development type of the multi-arch tunnel, which can significantly improve the construction efficiency and reduce the project cost. However, there are some disadvantages such as close construction, multiple transformation of the stress system and difficult construction control. Therefore, the mechanical mechanism and failure characteristics of the lining structure of the multi-arch tunnel without middle drift are studied through model tests, combined with typical tunnel disease characteristics and the construction experiences of 65 tunnels, the safety construction countermeasures of the unguided arch tunnel are put forward. The model experiment results show that: The bending moment and axial force values of the right arch waist of the advance hole are both largest and the most unfavorable parts. Therefore, the structural design and construction quality control of the right arch waist and other parts of the advance hole need to be strengthened, and countermeasures of the thirty words principle of "pay attention to geology, strong advance, pre-reinforcement, stable middle wall, first support, short excavation, weak blasting, frequent measurement, tight secondary lining and detail injection" are proposed. The countermeasures in this paper have guiding significance for the design and safe construction of multi-arch tunnel without middle drift.