## 1 Introduction  
In recent years, the construction site requirements of mountain tunnels have become increasingly stringent due to route planning and topography. Due to the small footprint of the small clear-distance tunnel, it has been widely used in urban and mountain tunnels [1, 2]. During the construction process, it is necessary to ensure the stability of the intermediate rock mass. Another similar type is the double-arch tunnel. The two adjacent tunnels are connected by a middle partition wall [3, 4]. These two types of tunnels are different from ordinary tunnels in that they are affected by mutual disturbances between neighbors. Therefore, the safety of their construction cannot be ignored. Research on double-arch tunnels and small clear-distance tunnels has mainly focused on theoretical analysis, field tests, model tests, and numerical simulations. Regarding theoretical analysis, [PERSON] et al. [5] proposed an analytical solution, considering the interaction between tunnels for the stress and displacement problem of parallel double tunnels. [PERSON] et al. [6] studied the effect of different distances as well as the surface slope on the surrounding rock pressure of an asymmetrical load on a small clear-distance tunnel. [PERSON] et al. [7] proposed an analytical solution to determine the internal forces of a shallow-buried, double-continuous arch tunnel support structure under symmetric loading. Combining the force method with the unbalanced force transformation method, [PERSON] et al. [8] proposed an internal force calculation method for Double-O-tube lining. In terms of field measurement, [PERSON] et al. [9] conducted on-site monitoring of the double-arch tunnel at Zipupieping and identified the upper and lower step intersection areas and the middle partition wall as weak locations. [PERSON] et al. [10] derived from the site geology of a tunnel with a double-arch tunnel that the over-excavation problem occurs mainly in the connection area between the middle guide tunnel and the main tunnel. [PERSON] et al. [11] conducted on-site monitoring of a double-arch tunnel and showed that the tunnel deformation and forces are directly related to its location and geological and construction process. [PERSON] et al. [12] conducted an overall inspection of a double-arch tunnel and found that the tunnel lining cracks were mainly located in the middle partition wall, the side wall, and on the top of the arch. [PERSON] et al. [13] conducted a detailed monitoring and data analysis for a double-arch tunnel and then provided design and construction recommendations based on this. In terms of model tests, [PERSON] et al. [14] developed an experimental model of a tunnel with a small clear distance under asymmetric loading and used the model to analyze the damage mechanism of the surrounding rock under asymmetrical topography. [PERSON] et al. [15] carried out a large shaking table test to investigate the effects of the seismic wave type and acceleration excitation peak on the strain response pattern of shallowly buried asymmetrical loading small clearance tunnel lining. [PERSON] et al. [16] conducted physical model tests and numerical simulations of the Great Wall Ridge Tunnel to gain a comprehensive understanding of the deformation law of the shallow-buried, double-arch tunnel. [PERSON] et al. [17] used strain gauges to monitor the longitudinal deformation of the pipe roof at the entrance of a shallow-buried continuous arch tunnel and found that the double-layer pipe roof could play a good role in limiting the surface deformation. Based on indoor model tests and numerical simulation, [PERSON] et al. [18] studied the tunnel profile displacement and stress and pressure arch distribution law of the surrounding rock during the excavation of the loess continuous arch tunnel. On-site monitoring can only be performed for a particular project, and physical models are costly to produce. Numerical simulation was widely used because of its convenience and low cost in recent years. [PERSON] et al.