## 6 Conclusions  
The simulation in this study was conducted using MIDAS to model the tunnel dimensions based on the construction site. The model was then imported into FLAC software to simulate the stability of the tunnel surrounding rock and the initial support when crossing different goaf conditions. Based on the simulation results, the deformation patterns and stress conditions of the surrounding rock and the initial support under various goaf scenarios were analyzed. The results are as follows:  
Figure 18: Guidance for engineering: (**a**) The resistivity profile image of the Huaying Mountain High-Speed Railway Tunnel site; (**b**) The drilling process of the CASAGADNE-C6 xp-2; (**c**) Changes in vertical displacement; (**d**) Changes in horizontal displacement; (**e**) Changes in maximum axial force of initial support; (**f**) Design of corresponding support schemes for different working conditions; (**g**) Design the best solution based on the above content. 1. Since the goat cavity is close to the left hande of the tunnel, the left arch waist of the tunnel is significantly affected by the goat. As the distance increases, the horizontal displacement of the left arch waist continuously decreases. When the distance reaches 20 m, the horizontal displacement of the left arch waist decreases by 16% compared to when the distance is 5 m, and the vertical displacement of the vault decreases by 18%. As the distance continues to increase, both the horizontal and vertical displacements of the tunnel show a decreasing trend. The degree of collapse and subsidence of the surrounding rock at the tunnel vault becomes less severe, and the maximum axial force of the initial support shows a significant change when the distance to the goat increases from 5 m to 10 m, decreasing by 124 KN. However, when the distance to the goat increases from 15 m to 20 m, the change is relatively minor, with a reduction of only 70 KN. Compared to the change between 5 m and 10 m, this variation is only 56%. This indicates that once the distance increases beyond a certain point, the maximum axial force in the initial support will no longer experience significant changes. 2. As the scale of the goat gradually increases, the deformation values at key positions of the surrounding rock continuously rise. When the diameter reaches 12.5 m, the horizontal displacement of the arch waist increases by 27.6% compared to the 5 m case, and the vertical displacement of the vault increases by 20.3%. As the scale of the goat increases, the degree of local subsidence at the tunnel vault becomes more pronounced; the phenomenon of longitudinal arch bottom uplift becomes more evident; and the range of subsidence along the longitudinal direction is significantly enlarged. As the goat cavity diameter changes from 5 m to 20 m, the variation in the maximum axial force of the initial support is relatively uniform and gradual, differing from the impact caused by distance. 3. As the angle gradually increases, the horizontal displacement distribution of the walls on both sides of the tunnel ceases to be symmetrical. When the angle reaches 60\({}^{\circ}\), the horizontal displacement of the right arch waist increases by 18.3% compared to when the angle is 15\({}^{\circ}\), while the vertical displacement decreases by 24.2%. It can be observed that with the increasing angle, the degree and extent of subsidence of the right arch waist continually increase, while the collapse degree and range of the vault decrease. As the goat angle varies from 15\({}^{\circ}\) to 60\({}^{\circ}\), the change in the maximum axial force of the initial support is relatively uniform. This phenomenon is similar to the effect of different goat diameters and differs from the impact caused by distance. 4.