Abstract: Based on a case study of a municipal river engineering project near pipe jacking launching well, a three-dimensional numerical model was established to study the influence of different reinforcement options at the back of the pipe jacking launching pit and the presence or absence of river conditions on the soil deformation behind the launching pit. The results show that the reinforcement concept of using single row piles and three-axis soil mixing columns for the improvement of the launching pit is feasible when there is no river channel. When there is a river channel, the lateral displacement value of the strata using this reinforcement scheme is 66.15mm, which does not meet the requirements of deformation control. When the back of the launching pit of the pipe jacking is close to the river channel, the depth range of the river channel cannot provide effective support at the back of the pipe jacking, and the passive soil pressure provided by the back of the back layer must be calculated from the bottom of the river channel; The soil improvement adopted a double row pile + three-axis soil mixing pile reinforcement concept, with a maximum deformation value of 29.22 mm in the soil, which meets the deformation requirements of the surrounding environment and is feasible; The embedded depth of the double row piles in the support should meet the requirements of the stability of the deep excavation and the ability of the passive soil pressure on the outer layer of the piles to balance the pushing force of the pipe jacking.

Key words: Pipe Jacking, River Course, Double-Row Piles, Solidification, Soil Displacement