Abstract: Due to its unique structure, the non-central guide tunnel has a wide applicability in the highway tunnel construction. Based on the construction of the double arch tunnels in Yunnan, this paper uses the three-dimensional numerical simulation to study the impact response of the rear tunnel construction on the surrounding rock mass and the lining of the first tunnel. The stress, displacement, and the plastic zone distribution of several monitoring points are selected as the research objects, including the displacement of the top, double arch position, and arch bottom of the first tunnel, the horizontal convergence of the cross-section, stress of the support structure of the first tunnel, and stress and plastic zone distribution of the surrounding rock mass of the tunnel. The focus is on analyzing the settlement of the arch crown, horizontal convergence of the arch waist, and stress state of the surrounding rock mass and lining during the excavation process of the rear tunnel under the different excavation depths. By comparing the mechanical state of the surrounding rock mass and lining before and after the excavation of the front tunnel, the impact of the rear tunnel excavation on the existing front tunnel is explained and analyzed. The results shown that: (1) the overall vertical displacement distribution of the tunnel is asymmetric, and the excavation of the rear tunnel increases the settlement of the arch top of the front tunnel. The settlement of the arch top of the front tunnel caused by the excavation of the rear tunnel accounts for about 15% of the overall settlement of the front tunnel; (2) The excavation of the rear tunnel has a significant impact on the stress distribution of the support structure of the front tunnel: (3) After the construction of the rear tunnel is completed, the maximum principal stress of the monitoring section support structure of the front tunnel is increased by about 1.4 times compared to the construction of the front tunnel. After the tunnel excavation is completed, the tensile stress zone is mainly concentrated at the arch corner of the leading tunnel near the following tunnel.

Key words: Continuous Arch Tunnel, No Central Guide Tunnel, 3D Analysis, Construction Process