Stability of surrounding soil by using underpinning pipe jacking method

In this paper, ground movement around shallow underground structures when a new structure is constructed crossing beneath an existing structure was studied using a finite different method (FDM) by means of FLAC3D. The induced stress generated by the excavation work is controlled by underpinning pipe jacking method to protect the existing structure failure. Six underpinning pipe jackings are jacked around the projection area of new structure; 3 at right side and 3 at left side. This study also considers the pipe shape, distance between pipe to new structure, and distance between pipe to the existing structure. The cross-section of the pipe was considered in circular and square. While distance between pipe and new structure and the existing structure was considered 1 to 3 m. The results showed that the underpinning pipe jacking method was a powerful tool for controlling the induced stress when the projection area is excavated; accordingly, the settlement can be minimized. Pipe shape influenced the stress pattern surrounding the existing structure and new structure, in which rectangular-shaped pipe shows a better ability to restrain ground movement. The ability to restrain ground movement increases with decreasing distance between pipe and the existing structure and decreases with increasing distance between pipe and new structure. The achievements can be practically used in excavating a new structure for stability of shallow underground structure.