Effect of Shield Tunneling on Existent Piles in Soft Soil Area

In urban environment, short-distance crossing of shield tunneling to existent piles is an unloading process and can cause adverse effect on the piles. This kind of effect should be controlled. To analysis and control this effect, numerical simulation, field monitoring and optimization of construction parameter were used in this study. To get reasonable calculation parameters for numerical models, field monitoring was conducted. The numerical simulation was utilized to study the process of short-distance crossing and the effect of ground improvement with rotary jet grout pile. The simulation result revealed that the ground improvement is not necessary in soft soil if the pile is long enough. In the later practical tunneling process, the ground improvement in the initial design was canceled. Construction parameters were adjusted in time, such as the strict controlling of synchronized grouting, secondary grouting, rotation speed of cutter head and driving speed. As a result, the displacement of the existent piles was controlled in the tolerable ranges.