# Synchronous Grouting Analysis of Shield Tunneling through High Water Pressure Fault Fracture Zone
## 4 Analysis of Synchronous Grouting Parameters
### Grouting Pressure  
During the shield tunneling process, the grouting pressure at the shield tail acts on the surface of the rock and soil, causing settlement disturbance to the fault fracture zone. As the shield tunneling advances, the grouting pressure gradually dissipates and the grouting layer hardens, causing settlement to occur again in the rock and soil. Therefore, different grouting pressures are selected for parameter analysis in the model.  
As shown in Figure 19, the vertical settlement curve of the rock mass at 0.2 R along the top of the tunnel axis under different grouting pressures after shield tunneling is shown. Overall, there is a significant difference in soil and rock settlement between the original rock and the fault fracture zone, with the maximum settlement in the fracture zone area being three times that of the original rock. At the same time, there are certain differences in the settlement deformation between the upper and lower wall fracture zones within the fault fracture zone structure, and the settlement of the rock and soil in the lower wall fracture zone is relatively large.  
The maximum settlement variation of monitoring points under different grouting pressures is shown in Figure 20. When the grouting pressure increases from 300 kPa to 400 kPa, the maximum settlement decreases from 1.976 mm to 1.923 mm; when the grouting pressure increases from 400 kPa to 500 kPa, the ability to control settlement deformation decreases to a certain extent. This is due to insufficient grouting pressure and the release of stress in the rock and soil, resulting in a larger settlement amount; however, excessive  
Figure 19: The tunnel top settlement curve.  
growting pressure causes plastic deformation of the rock and soil mass. When the grouting pressure disappears, the slurry does not form strength, and further deformation occurs with the release of stress in the rock and soil mass. Therefore, in practical engineering, it is necessary to ensure that the grouting pressure is controlled within a reasonable range. If the grouting pressure is too small or too large, it will affect the settlement and deformation of the formation.  
As shown in Figures 21-23, the variation curves of pore water pressure at three monitoring points in ordinary surrounding rock, upper wall induced crack zone, and fracture zone under five different grouting pressure conditions during shield tunneling are shown. The results show that synchronous grouting pressure has a strong impact on the pore water pressure of surrounding rock and soil. When the grouting pressure is low (such as 300 kPa, 350 kPa), the change in pore water pressure is close, and as the grouting pressure increases (400 kPa-500 kPa), The pore pressure of the surrounding rock also increases correspondingly, and at this time, the pore pressure is proportional to the grouting pressure.  
Figure 21: The variation curve of pore pressure at ordinary surrounding rock monitoring points.  
Figure 20: Maximum settlement variation under different grouting pressures.  
vertical settlement deformation. And the maximum settlement variation under different grouting quantities is shown in Figure 25.