Influence of construction condition on thrust force and acting earth pressure on pipe by pipe stack model.

Supervisor Mitsutaka SUGIMOTO

Pipe jacking method is a technique for installing underground pipelines. Powerful hydraulic jacks are used to push pipes into the ground behind a TBM, at the same time excavation is taking place within the TBM. The main factor influencing on jack force is the friction resistance between pipes and ground, then the excavation radius by the TBM is larger than the outer radius of pipes. The over-cutting area between pipes and the ground exists, which is a significant factor giving influence to jack force. So far, most of the models estimating jack force do not consider the over-cutting area, and then the pipe behavior is not still clarified well.
To overcome the above problems, the new analysis model has been developed by using the full ground spring model that can take over-cutting into consideration. This analysis model has been validated using ideal data and site measured data in the previous research.
This study aims to make parameter studies to find out the main factors which give influence to jack thrust and earth pressure acting on pipe. The design conditions, the optimal size of cushion material, and the optimal construction conditions are examined, too.
As a result of parameter studies, it was confirmed that the proposed analysis model can express the displacement and earth pressure on the pipe surface, the jack force, the friction resistance around pipe surface and the moment at the joint part reasonably. In addition, the effects of each setting parameter to pipe and cushion material are also confirmed

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