# Analysis and Application of Lining Resistance to Water Pressure in Tunnel through Karst Cave
## 2 Failure Mode of Grouting in Tunnels Crossing High-Pressure Karst Caves
### Influence of Grouting Range on the Effect of Grouting
#### 2.3.2 Results of Numerical Calculations  
The effect of different grouting reinforcement zones on the hydraulic resistance of the grouted stone body during the tunnel side penetration of the cavern was calculated as shown in Figure 9. From the figure, it can be seen that the damage to the stone body at different grouting angles was dominated by tensile-shear damage, the main cracks of the grouted stone body were sprouted from both ends of the reinforcement circle, and the cracks penetrated the structure. With the increase in the grouting angle range, the location of the cracked stone body expanded to the outer side, and, when the grouting range reached 120\({}^{\circ}\), the crack no longer penetrated, which can be considered as a significant weakening of the effect of cavern water pressure on tunnel safety after this time. From the calculation results of typical acoustic emission of different ranges shown in Figure 10, it can be seen that, as the grouting range increased, the energy generated when the stone body was destroyed under critical water pressure gradually increased, and there were more tensile and shear damage units. The damage of the grouting circle at this time tended to have a greater disturbance toward the stable surrounding rock, which indicated that the effect on the tunnel stability after the destruction of the grouted stone body with stronger resistance to water pressure is often greater and needs to be focused on during construction. Figure 8: Schematic diagram of the numerical calculation model for different grouting ranges: (**a**) grouting range of 30\({}^{\circ}\); (**b**) grouting range of 60\({}^{\circ}\); (**c**) grouting range of 90\({}^{\circ}\); (**d**) grouting range of 120\({}^{\circ}\); (**e**) grouting range of 180\({}^{\circ}\); (**f**) grouting range of 360\({}^{\circ}\). According to the calculation results, the water pressure resistance of different grouting reinforced areas was analyzed, and the water pressure resistance and damage characteristics of the stone body under various grouting reinforced areas were compared, as shown in Figure 11. It can be found that a larger extent of the grouting reinforcement zone led to a better the effect of grouting stone reinforcement. When the grouting range was enlarged to the extent that the tunnel was separated from the karst, while continuing to increase the range of the grouting reinforcement zone, the effect on improving the water pressure resistance of the grouted stone body was weak. Compared with the calculation results of the 180\({}^{\circ}\) grouting reinforcement area and 360\({}^{\circ}\) grouting reinforcement area, it can be seen that, for the case of the adopted side cavity calculation, the 180\({}^{\circ}\) grouting range and 360\({}^{\circ}\) grouting range had no significant effect on the improvement of the karst body's  
Figure 10: Acoustic emission diagram of grout damage for different grouting ranges: (**a**) grouting range of 30\({}^{\circ}\); (**b**) grouting range of 60\({}^{\circ}\); (**c**) grouting range of 90\({}^{\circ}\); (**d**) grouting range of 120\({}^{\circ}\); (**e**) grouting range of 180\({}^{\circ}\); (**f**) grouting range of 360\({}^{\circ}\). Figure 9: Numerical calculation results of damage characteristics of grouting for different grouting ranges: (**a**) grouting range of 30\({}^{\circ}\); (**b**) grouting range of 60\({}^{\circ}\); (**c**) grouting range of 90\({}^{\circ}\); (**d**) grouting range of 120\({}^{\circ}\); (**e**) grouting range of 180\({}^{\circ}\); (**f**) grouting range of 360\({}^{\circ}\). hydraulic resistance. Therefore, in the actual project, there is no need to grout the side cavities of the tunnel without cavity distribution, and single-side grouting can meet the safety requirements.