## 6 Influence Analysis of Construction Parameters and Field Verification
### Impact Analysis of Synchronous Grouting Quantity  
The influence of the synchronous grouting quantity was investigated based on the (\(P_{s}^{*}=0.90,F_{f}^{*}=0.38,V_{g}^{*}=0.95\ \sim 1.47\)) calculation condition. The vertical settlement curve at point A for different \(V_{g}^{*}\) values is given in Figure 23. According to the results, the influence of the \(V_{g}^{*}\) increment was reflected as the significant reduction of the settlement value of A when the shield tail passed through. The main reason for this situation is that the slurry after injection compensates for the ground loss by compacting the soil around the shield, which mainly affects the settlement value of the monitoring point. The vertical displacement of the soil above the shield is depicted in Figure 24. Figures 25 and 26 show the horizontal displacement in the axial and transverse directions at the hance of the tunnel, respectively. The radial displacement of the segment is shown in Figure 27. The following results were obtained with the examination of Figures 24-27: the vertical displacement of the stratum above the shield significantly decreased as \(V_{g}^{*}\) increased; the horizontal displacement of the stratum along the axial direction on the side of the shield gradually decreased, while the horizontal displacement along the transverse direction significantly increased, the ovality of the segment reduced from 18.21 mm to 13.83 mm, and the change was noticeable.  
Figure 24: Vertical deformation of the stratum under different synchronous grouting ratios \(V_{g}^{*}\).  
Figure 23: Vertical settlement at point A under different synchronous grouting ratios \(V_{g}^{*}\).  
As a result, increasing the amount of synchronous grouting helps control deformation in water-rich soft soil stratum. To minimize ground loss, the synchronous grouting operation should be completed on time and effectively in actual engineering.  
Figure 27: Lining ovality under different synchronous grouting ratios \(V_{g}^{*}\).  
Figure 25: Horizontal deformation of the stratum along the axis direction under different synchronous grouting ratios \(V_{g}^{*}\).  
Figure 26: Horizontal deformation of the stratum along the transverse direction under different synchronous grouting ratios \(V_{g}^{*}\).  
To summarize, of the three contributing factors, the increase in friction between the shield skin and the soil was the most detrimental to the deformation control of the water-rich soft soil stratum. The friction between the shield skin and soil was related to the normal stress and interface friction coefficient acting on the periphery of the shield shell. Furthermore, the normal stress was related to the stress state of the stratum under shield tunneling disturbance, and the friction coefficient was influenced by the soil properties, shield shell surface roughness, and construction parameters. In actual engineering [29], timely injection of bentonite slurry can reduce the friction between shield skin and soil. Among the three influencing factors, the increase in synchronous grouting quantity was the most favorable to the deformation control of the water-rich soft soil stratum and segment. It exhibited a clear inhibitory influence on the segment's ovality and minimized the vertical and horizontal displacement of the stratum. In practice, timely and effective synchronous grouting can limit shield tunneling disruption to the stratum and segments.