Study On The Deformation Influence & Control Of Pipe Jacking Construction On The Subgrade Of Existed Urban Rail Transit

With the formation of the urban rail transit network, there are more and more municipal pipelines that traverse the subgrade of existed urban rail transit. Although the technique of pipe jacking construction as a technology of no need of excavation, that has the advantages of low cost, short construction period, small environmental impact and high security in construction, has wide application in traversing projects, it inevitably disturbs the surrounding soil and brings about the ground and stratum movement, and then affect the security of existed lines. In order to ensure the normal and safe operation of urban rail transit, it's necessary to deeply study this question.Based on fully understanding the technology of pipe jacking, the ground movement mechanism and cause are discussed in this paper, and it is recognized that the disturbance of stratum and stratum loss are the root causes resulting in the ground movement. Different burial depth, pipe diameter, head pressure and other factors are discussed by using finite element method, and the results show that it's important to choose reasonable burial depth and pipe diameter, and control head pressure. Considering main construction parameters in simulating model, the rule of ground movement and range of influence are analyzed in this paper. Besides, a model with stratum and subgrade of existed urban rail transit is simulated for analyzing the deformation rule of rail causing by pipe jacking construction and main construction factors' influence and the effects of protecting methods. Based on the studies mentioned above, it is suggested that the best way to controlling the deformation resulting from constructing is to control the process of the whole of the construction. The way to formulate the controlling variable and its suggested values are given. It's necessary to take control of the deformation of existed lines from pipe jacking construction, stratum and subgrade of existed urban rail transit. These research achievements mentioned above have reference value in future similar construction.