## 1 Introduction
In the actual construction process, considering the overall safety of the main tunnel, the support should be set inside the main tunnel. In a based 3D finite element analysis, [PERSON] et al. [9] proposed the 3D shell-spring approach. [PERSON] et al. [10] studied the displacement and mechanical response of the shield tunnel with a diameter of 10.5 m in the process of cross-passage construction. [PERSON] et al. [11] analyzed the force of the special segments under the structural state before and after construction. By using the finite element numerical simulation method, calculated that obvious stress concentration appeared in the opening area of the main tunnel during the opening of the cross passages. In terms of microtunnelling technology, [PERSON] et al. [12] and [PERSON] et al. [13] analyzed the effects of a support system and grouting materials. Some studies have tested and simulated the influence of mechanical construction on the segments. [PERSON] et al. [14] carried out numerical simulation analysis on the broken openings of different segments. It is found that with the reduction in the cutting hole strength, the maximum displacement of the normal tunnel and the segment displacement of the opening increased. Changing the strength value of the opening influences the overall deformation of the normal tunnel and the displacements of the opening segments, but the effect is not large. [PERSON] et al. [15] studied the mechanical behavior of the segment at the intersection of the tunnel and the cross passage. Curtain grouting is better than small pipe grouting. The results of the centrifugal model test show that the maximum tensile stress and the maximum compressive stress of the inner part of the arch are more than the design value of the tensile strength of C60 concrete, and there is a risk of rupture. Composite pipe segments should be used in construction. Recently, our research group put forward a cross-passage construction method of ring cutting and push-in. The machine is shown in Figure 1. With the innovative technology of ring cutting and segment assembly, the construction can not only complete the excavation of cross passages safely and efficiently, but also control the surface settlement of ground well, which will obtain better social and economic benefits. And it is suitable for the construction of the cross passage for the shield tunnel section in the water abundant area, especially for the projects of cross passage with poor soil stability, short construction period, and high environmental protection requirements. From the background above, most of previous research is based on steady-state analysis of different stages of construction by mechanical method. It is considered that more dynamic analysis of the construction process should be investigated. Meanwhile, different from the current research and analysis of cutting the main tunnel using arc cutter head, the study analyzes the main tunnel hole breaking using flat-face cutter head. Therefore, based on the engineering background of Jingrong Street station- Kunjia Road station of Suzhou Metro Line 11, the numerical simulation is conducted to study the mechanical response of the segments in the construction of the flat-face cutter head pushing method, which could provide some engineering application suggestions.