# Analysis of Shield Tunnels Undercrossing an Existing Building and Tunnel Reinforcement Measures
## 7 Deep Hole Grouting Reinforcement Technology for Shield Tunnel
### Effect of Radius of Radial Reinforcement on Reinforcement Effect of Deep Hole Grouting in Tunnel  
The radius of radial reinforcement refers to the length of the grouting pipe entering the soil layer and extending out of the shield segments. As the pressure of deep hole grouting was usually large, if the grouting was done too early, the slurry would break the shield tail brush and cause damage to the shield machine, making the synchronous grouting slurry leak and inadequate grouting, so the deep hole grouting reinforcement was generally carried out after the segments were released from the five rings of the shield tail. Therefore, in this section, the surrounding soil would be grouted for reinforcement after the segments were separated from the five rings at the tail of the shield. According to the above analysis, the grouting pressure was set to 250 kPa, the excavation pressure was still set to 200 kPa, and the jack pressure was still set to 150 kPa. The slurry solidified and hardened after five rings of grouting. There was a small clear distance for the double shield tunnels, and the distance was only 6.1 m between the outer walls of the two tunnels, so the radius of radial reinforcement was selected as 1 m, 2 m, and 3 m, respectively. The grouting range in front and behind the building was taken as eight rings. The maximum lateral displacement of the pile and the maximum subsidence of the building with the excavation of the shield tunnels under different radii of radial reinforcement were shown in Figures 30 and 31, respectively. Figure 32 shows the histogram of the maximum subsidence of the building and the maximum lateral displacement of the pile with the excavation of the shield tunnels under different radii of radial reinforcement where the grouting reinforcement radius of 0 m meant no grouting reinforcement measures. From Figure 30, it can be found that the variety rule of the maximum subsidence of building under different radii of grouting reinforcement was basically the same during the excavation of the tunnel. Compared with no grouting reinforcement measures, the use of grouting reinforcement measures for deep holes in the tunnel can effectively reduce the subsidence of the building. When the radius of grouting reinforcement was 2 m, the subsidence of the building can be reduced to the maximum extent. Figure 32 showed that the maximum subsidence of the building was 7.37 mm without grouting reinforcement, while the radius of grouting reinforcement was 2 m, the maximum subsidence of the building was 4.82 mm for the radius of grouting reinforcement of 2 m, with the reduction of 34.60%. From Figure 31, it can be found that the lateral displacement of the pile with \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Soil** & **Elastic** & **Poisson’s Ratio** & **Severe/(kN m\({}^{-3}\))** & **Cohesion/kPa** & **Internal Friction** \\  & **Modulus/MPa** & & & **Angle/(\({}^{\circ}\))** \\ \hline Strongly & & & & & \\ weathered slate & 120 & 0.2 & 23.3 & 50 & 29 \\ Reinforce soil & 500 & 0.2 & 21 & 30 & 43 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparison of parameters of reinforced soil and undisturbed soil. different radii of grouting reinforcement during shield tunneling was basically the same. Compared with no grouting reinforcement measures, the use of grouting reinforcement measures for deep holes in the tunnels can evidently abate the lateral displacement of piles, and as the radius of grouting reinforcement increases, the lateral displacement of piles is reduced. Figure 32 shows that the maximum subsidence of the building was 3.83 mm without grouting reinforcement, while the maximum subsidence of the building was 2.69 mm for the radius of grouting reinforcement of 3 m, with a reduction of 29.77%.