## 1 Introduction
Additionally, [PERSON] conducted substantial research on the dilation behavior in the shear process [31; 32; 33]. The non-linear strength criterion of the structural plane was proposed and developed, and is a relatively complete method. As mentioned above, the strength criteria for rock mass discontinuities also have certain applicability to interfaces. Currently, however, research on the strength criteria for a packed structural plane or soil-rock interface  
Figure 1: Tunnel and interface. This tunnel is named Goudong tunnel, which is located at Shanxi Province, China. It is a shallow-buried tunnel. An interface with dip angle of 34\({}^{\circ}\) between sandstone and mudstone cuts the tunnel, which causes numerous cracks in tunnel structure. is lacking. [PERSON] proposed an anisotropic shear strength criterion for the soil-rock interface based on energy conservation [34]. Additionally, in tunnel engineering, the interface strength is an inevitable element to the analysis of the stability of the surrounding rock, which is related to the stability analysis of the surrounding rock [35; 36; 37]. Therefore, it is very important to combine the strength criterion of the interface with the stability analysis of the surrounding rock. In terms of the shear behavior of rock mass discontinuity, [PERSON] et al. [38] studied the creep shear mechanical behavior of regular jugged discontinuity. [PERSON] et al. [39] studied the shear mechanics characteristics under different normal loads with regular jugged discontinuity as the object. In addition, many scholars have studied the effects of structural plane morphology, roughness, and filling on shear strength. However, anisotropy is a very important property of a rock mass, and the geometric relationship between the structural plane and the rock mass is the key factor to determine the anisotropy of the rock mass. Therefore, studying the geometric relationship between the structural plane and the rock mass is of great significance for an in-depth understanding of anisotropy. [PERSON] et al. [40] carried out the block shear test of a 45\({}^{\circ}\) dip plane, which provided the basic idea for this study. [PERSON] et al. [41] studied the shear behavior of the packed structural plane by using PFC2D software, and the structural plane inclination was also 45\({}^{\circ}\). The object of these studies was a single structural plane with the shear test as the main test method. However, the anisotropy of a rock mass cannot isolate the discontinuity, so it is necessary to analyze the rock mass with the discontinuity through compression test. The bedding development of sedimentary rocks contains natural structural planes, which are typical transverse isotropic materials. The analysis of rock anisotropy can be realized by controlling the compression direction of different angles [42]. However, in practical engineering, the rock mass structural plane is often distributed in two or more pieces, and it is difficult to carry out further research by laboratory test and simple calculation. Discrete element numerical simulation software can effectively solve this problem. Therefore, numerical simulation becomes an effective means in multi-joint analysis [43]. Tunnel engineering is buried in an underground rock mass, and its stability is closely related to the property of the rock mass. A physical model test is an effective research method, through which many meaningful results can be obtained [44]. However, few of these studies focused on the impact of the structure on the tunnel structure, so it is necessary to conduct in-depth research and analysis. Based on the above-mentioned research background, this study investigated the mechanical behavior of a tunnel-interface system under the influence of the dip angle. By constructing a simplified physical model, uniaxial compression tests were carried out and the deformation of the model during the test was monitored in real time using the particle capture method [45; 46; 47; 48].