## 3 Results
### Deformation Characteristics  
The deformation of samples with different inclination angles is significantly different. Figure 6 shows the horizontal deformed cloud map. For the no interface sample, the horizontal displacement field forms an hourglass shape, and the deformation range at the upper and lower ends is small, while the deformation range in the middle is large. The final failure also has the shape of an hourglass (Figures 6-8), and the same deformation and failure characteristics as the intact concrete specimen. The main effect of the tunnel on the displacement field is embodied in the deformation of the rock surrounding the chamber. As can be seen in the figure, the deformation around the tunnel is different, particularly at the vault, foot, and bottom. The contact face with different dip angles has a significant effect on the tunnel. The main deformation of the tunnel occurs close to the interface and exhibits different deformation characteristics at different inclination angles. Figure 4: Load versus displacement. Figure 5: UCS with different dip angles. Figure 6: Displacement contour of x direction (unit: 0.01 mm). The black dash line is discontinuous plane. The results were calculated when the sample reached peak strength. The x and y label are the number of pixel points, which is useless for calculation. When the angle is \(0^{\circ}\), the specimen is mainly subjected to compressive stress, which results in lateral tensile stress and the specimen exhibits obvious deformation on both sides (Figure 7b). The deformed trace line is generally a straight longitudinal line. The interface divides the deformed area into two parts, and the maximum horizontal displacement reaches 19 mm. When the angle was \(15^{\circ}\), the sliding deformation and compression deformation of the specimen occurred along the interface (Figure 7c). On the one hand, this made the deformable track bend toward the slip direction; on the other hand, it changed the deformation characteristics of the tunnel, and the tunnel was subjected to deviatoric stress, which led to obvious deformation in the shoulder. Two distinct displacement boundaries appeared, with a maximum displacement of 28 mm. Under the influence of the interface with an angle of \(30^{\circ}\), three obvious curvilinear displacement boundaries appeared. The crack trace curve developed and bulged in the  
Figure 8: Three-dimensional cracks. The cracks along z direction were obtained by artificial measurement of the failure morphology. Figure 7: Crack development. Under the action of pressure, the paint on the surface is detached from the sample, resulting in uneven surface. opposite direction of motion, which indicates that the material was pulled by a static friction force near the interface, causing deformation hysteresis. The lateral wall and arch foot of the chamber were obviously deformed, and the maximum deformation was approximately 30 mm. When the inclination angle was 45\({}^{\circ}\), sliding mainly occurred along the interface, and an obvious displacement trace did not appear on either side. The deformation on both sides was uniform, and large deformation existed at the bottom of the tunnel arch. The overall maximum deformation was approximately 35 mm. Notably, owing to the absence of lateral constraints in the test, the tip of the 45\({}^{\circ}\) sample was compressed and broken (Figure 7e). When a certain degree was reached, the entire sample was destroyed. When the inclination exceeded 45\({}^{\circ}\), the specimen exhibited different deformation characteristics. When \(\alpha\) was smaller than 45\({}^{\circ}\), the main deformation was slippage and shear deformation; when \(\alpha\) was greater than 45\({}^{\circ}\), the main deformation was lateral tension. When the angle was 60\({}^{\circ}\), two obvious deformable lines existed and were distributed in a straight line, and the interface controlled the distribution of these deformable lines.