## 2 Project Overview
### Construction Safety Control Technology
#### 3.6.1 Setting up Isolation Piles and Sleeve Valve Pipes  
1. To ensure the safety of the Beijing-Shanghai high-speed railway during the construction and operation of shield tunnels, a pile foundation is installed between the bridge foundation of the Beijing-Shanghai high-speed railway and the shield tunnel (\(\Phi\) 800@1000). Isolation and protection of drilled cast-in-place piles. The minimum distance between the isolation pile and the pile foundation of the existing Beijing-Shanghai high-speed railway bridge is 8.7 m, as shown in Figure 7. Considering the operational safety of the Beijing-Shanghai high-speed railway and the actual construction clearance on site, the drilling and grouting piles are selected to be drilled using a positive circulation drilling rig. The positive circulation drilling rig is 6 m high, with the most unfavorable position located under the bridge on the north side of the high-speed railway as an example. The drilling rig is 3.4 m away from the bottom of the beam, which does not pose a safety hazard to the crane. The pile foundation is drilled using manual lifting of steel cages, which are made in eight sections with a single section length of 5 m. The concrete pouring is carried out using the conduit method, which does not pose any safety hazards to the driver.
2. Sleeve valve pipe construction. Sleeve valve pipes are used for grouting reinforcement in areas where drilling and grouting piles cannot be constructed due to pipelines. A  
\begin{table}
\begin{tabular}{p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt} p{42.7 pt}} \hline \hline \multirow{3}{*}{**Monitoring Projects**} & **Yellow Alert** & \multicolumn{3}{c}{**Orange Alert**} & \multicolumn{3}{c}{**Red Alert**} & \multicolumn{3}{c}{**Limit**} \\ \cline{2-9}  & **Change Rate (mm/Day)** & **Accumulated Sentiment (mm)** & **Change Rate (mm/Day)** & **Accumulated Sentiment (mm)** & **Change Rate (mm/Day)** & **Accumulated Sentiment (mm)** & **Change Rate (mm/Day)** & **Accumulated Sentiment (mm)** \\ \hline Bridge jet settlement & \(\pm\)0.36 & \(\pm\)0.5 & \(\pm\)0.45 & \(\pm\)0.75 & \(\pm\)0.54 & \(\pm\)0.9 & \(\pm\)0.9 & \(\pm\)1.0 \\ \hline Surface subsidence & \(\pm\)5 & \(\pm\)10 & \(\pm\)8 & \(\pm\)15 & \(\pm\)10 & \(\pm\)18 & \(\pm\)15 & \(\pm\)20.0 \\ \rigid sleeve valve pipe with a diameter of 40 mm and a backward segmented grouting method were adopted. The grouting spacing between sleeve valve pipes is 1.2 m, and the grouting material within the reinforcement range is cement and water glass double liquid slurry. The sleeve valve pipe is drilled using a drilling rig, with two on the south side and a height of 5 m. The construction location is on the outside of the bridge and the west side of the high-voltage line, which does not pose a safety hazard to the driver.  
To reduce the difficulty of shield tunneling construction and consider the impact of shield tunneling on bridge pile foundations. Reserve grouting pipes on both sides of the isolation pile to achieve water sealing between the piles. The isolation piles on the outer side of the bridge that cannot be implemented due to pipeline relocation have been adjusted to sleeve valve pipe grouting to block the transmission of groundwater in the middle, fine sand layer, and pebble layer.