Abstract: The submarine pipeline laid on the shallow foundation of the deep sea is prone to axial expansion and contraction under the action of high temperature and high pressure during operation, and this movement will intermittently shear the shallow soil around the pipe. Therefore, it is necessary to investigate the mechanism of tube-soil interaction during the axial movement of the pipeline. In this paper, a small strain finite element analysis of the axial motion of a shallowly buried pipeline during operation is established based on the modified Cambridge model. In the process of axial movement of pipelines with different initial depths, the development curve of axial resistance (S-shaped consolidation curve) in critical plastic shear consolidation stage is fitted. The variations of the excess pore water pressure, the friction coefficient of the pipe-soil interface, the wedging factor ζ and the axial resistance between pipes and soils are discussed. It is found that the peak excess pore pressure generated by axial shear is a function of velocity and time. As the axial velocity decreases, the value of the peak excess pore pressure decreases and the time point of the peak pore pressure is delayed. The internal mechanism of the transition from undrained condition to drained condition in the process of axial movement is expounded.

Key words: submarine pipe, deep sea soft clay, axial motion, consolidation response, axial resistance