Study on Ground Deformation Induced by Square Pipe Group Jacking and Optimization of Key Jacking Sequences

This study investigates the ground settlement behavior induced by square pipe group jacking construction using the pipe-roof structure method. The research is based on the Yifeng Gate undercrossing project in the east extension of the Jiangnan connecting line of the Jianning West Road River Crossing Channel. Field monitoring data and numerical simulation were employed to analyze the settlement patterns. The key results are as follows: (1) In the horizontal direction, the “skip construction” sequence results in slightly less ground settlement compared to the “sequential construction” method. However, the difference is minimal. Considering construction efficiency rather than ground deformation control, the “sequential construction” method is recommended. (2) In the vertical direction, the “top-down” construction sequence generates significantly less ground settlement than the “bottom-up” approach. Provided that jacking equipment installation is feasible, the “top-down” sequence is recommended for settlement control. (3) Areas under high surcharge loads (e.g., beneath the city gate tower) and regions with densely arranged pipes are prone to larger settlements during jacking. Corresponding deformation control and compensation measures should be implemented in these zones. The findings of this study provide a valuable reference for similar pipe-jacking projects in urban sensitive areas under soft ground conditions.