Name:AKATWIJUKA RONALD

Stack Pipe Model Based Numerical Analysis for Pipe Behavior in Pipe Jacking Tunneling

Supervisor: Mitsutaka SUGIMOTO

With increasing urbanization, tunneling by pipe jacking has grown into a very important practice. In the pipe jacking method, accurate evaluation of the jacking force is important in choosing pipe materials, and the jacking equipment. To this end, a thorough understanding of the pipe's behavior as well as soil-pipe interaction during the excavation process is vital. The jacking force in pipe jacking tunneling is a product of the frictional force around the pipe peripheral by the surrounding ground and the face resistance. The excavating machine being of a larger radius than the pipes, results in a space opening up between the outer surface of the pipe and the excavated surface of the ground called overcut. In conventional practice in pipe jacking, static earth pressure is considered to act on the pipe and a thrust resistance coefficient applied accordingly with the ground structure to account for loosening. This method does not account for overcut and can not therefore sufficiently express the pipe-ground interaction.
In this study in situ data from a pump station drainpipe construction in Shirone, Niigata is studied and compared to the results of analysis by a recently developed stack pipe model for pipe jacking. This analysis expresses the ground's action on the pipe through a ground spring model. A ground reaction curve is used to express the stress of the ground on the pipe. This curve shows the variation of the ground spring with the displacement of the ground around the pipe peripheral. Overcutting is accounted for by adjusting the ground displacement on the ground reaction curve. 
Analysis results were compared for the joint properties, the pipe's as well as the surrounding grounds' horizontal and vertical displacement and the ground reaction on the pipe's surface. The trends obtained in the analysis were found to match the site measurements and the expected pipe behavior.
Therefore the stack pipe model for pipe behavior was found out to sufficiently represent the behavior of the pipe in pipe jacking. Recommendations regarding further study in this area are also listed.
Please use "previous botton" to return the previous page