## 4 Results and Discussion
### Displacement Response of Approximate Real Tunnel Model and Tunnel Model with Smooth Walls  
The final deformation of the approximate real tunnel model and the smooth wall tunnel model is shown in Figure 14.  
For the approximate real tunnel, the deformation degree of the tunnel on the right is lower than that of the tunnel on the left. When the left straight tunnel is considered the center, the deformation degree of the tunnel gradually decreases toward both sides. The top and bottom of the left straight tunnel have the most severe deformation, with a maximum deflection of 0.08 m. The bend tunnel and the branch of the T-shaped structure have the smallest deformation. The displacement distribution of the smooth wall tunnel is uniform, and the deformation degrees of the left and right tunnels are similar. The part with the highest degree of deformation is located at the bottom of the center of the tunnel, with a maximum deflection of 0.187 m, which is more than twice that of an approximate real tunnel. The minimum total displacement on the surface of the light-green deformation zone exceeds 0.07 m. The plastic deformation areas in the two types of tunnel models are mostly distributed in the middle and corner of the bottom of the straight tunnel, and small plastic damage areas are found in the top of the middle of the straight tunnel and the corner of the T-shaped tunnel. The plastic deformation area in the approximate real tunnel  
Figure 14: Final deformation situation in approximate real tunnel and smooth wall tunnel.  
Figure 13: Stress distribution in tunnel cross-section.  
is smaller than that in the smooth wall tunnel, and no plastic deformation is found in its bend tunnel.  
Figure 15 shows the displacement curves of the S1-S9 measuring points at the sections A-C, B-D, G-I, H-J, and N in the approximate real tunnel model (left-hand side of Figure 13) and the smooth wall tunnel model (right-hand side of Figure 13). In each section of the two tunnel models, except for the N section of the bend, the points with higher displacement are always S1 and S2 at the bottom of the tunnel and S9 at the top of the tunnel whereas S3 and S4 at the corner of the tunnel have the lowest displacement.  
Figure 15: Displacement time curve of S1–S9 monitoring points in approximate real tunnel and smooth wall tunnel.  
The results of the previous analysis show that the duration of high load on the wall of the approximate real tunnel is lower than that of the tunnel with smooth walls, resulting in the lower displacement of each monitoring point on each section of the approximate real tunnel than in the tunnel with smooth walls in general. The maximum displacement values of monitoring points A-C S1 and G-I S1 are 26.9% and 20.7% lower than in the tunnel with smooth walls, respectively whereas the displacement values of most monitoring points on the right tunnel section are less than half of those in the tunnel with smooth walls. Overall, the maximum deformation displacement of the approximate real tunnel does not exceed 0.1m, and as the shock wave energy decays, most of the deformation of the tunnel gradually recovers. Therefore, the approximate real tunnel will not lose stability as a result of gas explosion.