Abstract: The jet grouting improved soil surrounding the caisson for a pipe jacking for a power transmission project in Shunde District, Foshan City, Guangdong Province, is numerically simulated by using the ABAQUS software. The internal force variation and displacement of the jet grouting improved caisson and surrounding soil before and after pipe jacking construction of small diameter pipe jacking shaft are evaluated by the finite element method. The wall deformation and soil three-dimensional failure modes of the small diameter electric caisson after passing through layered soil and applying jacking force are evaluated. The following conclusions are made during the excavation, the surrounding soil is easy to cave into the excavated area due to the soil unloading effect, and the pile tends to be extruded by soil. Under different jacking forces, the locations where the maximum displacement in the active zone are consistent; the performance of both soil and pile are similar and no separation is observed. In the passive area, larger differences between soil and pile are observed. With the push force reaches the limit state, the displacements of the soil and pile are large, and the pile is likely to be damaged. When the pile passes through two different soil layers, the stress at the interface changes, and the stress in the loading region forms an open gourd shape. The shape of this gourd becomes obvious with the increase of the jacking force. The internal force distribution is uniform at the low jacking force, but the main bearing part becomes passive pile with increasing jacking force. When the thrust force reaches a certain limit, the passive settlement area develops stably, while the upward displacement area expands rapidly, resulting in serious uplift of surface soil. Due to the pile support in the active zone, the tensile cracking degree of soil under the jacking force is small, indicating that the installation of jet grouting pile can greatly improve the performance of soil and effectively prevent the cracking development in the active zone soil.

Key words: Caisson for Pipe Jacking, Pushing Force, Numerical Simulation, Jet Grouting Column Reinforcement, Soil Mass Deformation