Study On The Stratum Movement And Deformation Control Induced By Pipe Jacking Construction

Pipe jacking construction method is being paid more and more attention in engineering field when pipe constructed. The dominating reason is that it can avoid interfering with railway, traffic and crowd, it also can decrease earthwork and avoid destroying structures and scenic spots. However, pipe jacking construction inevitably results in stratum movement, especially surface subsidence, which will menace the security of underground pipeline and adjacent buildings if the settlement is very large.This paper is based on the pipe-jacking project in the north of Nanjing city for sewage disposal factory capacity of 300000 m3 per day. By in-situ measure, mechanics analysis, FEA numerical simulation, a systematic research is made on the deformation mechanism and regularity of soil, the influence factors of ground movement, the different control measures to decrease stratum movement and influence on surroundings during pipe-jacking construction, all these will offer reference to design and construction of other similar projects. The main content of the thesis is as follows:1. Combined with the practical construction characters of large pipe jacking project of sewage collecting pipe nets, the mechanics mechanism and the variation of soil stress state due to being disturbed during pipe-jacking construction are discussed. The soil can be divided into different zones based on the variation of stress state compared with initial stress state. The variation of stress state and characters of soil, the reason of stratum movement and the regularity of surface movement are studied.2. Based on the basic arithmetic of Mindlin solution and Matlab6.1 procedure, a utility program (PPJKING) is compiled. Combined with the pipe-jacking project in w14-w16, soil "arch" effect ahead of shield during jacking construction is analyzed, and stress state of the soil and area of "arch" effect are discussed. Combined with numeric simulation and graphical technology, stress graph and stratum movement plot during pipe jacking construction are provided.3. ANSYS, 3D FEM software is adopted to analyze stratum movement and soil influence during pipe jacking construction and 3D movement of buried depth soil mass is simulated due to the normal jacking force, stratum loss, friction between pipe and soil, and interaction. The simulation results are compared with the measured value.4. Based on the results of calculation and analysis, influence degree and range of surroundings are thoroughly analyzed. And the effective control measures during pipejacking construction to decrease influence on surroundings are put forward, which will realize the jacking construction of the protection environment type and offer reference to design and construction of other similarity projects.