Stress Analysis of a Concrete Pipeline in a Semi-Infinite Seabed under the Action of Elliptical Cosine Waves Based on the Seepage Equation

This study aims to investigate the mechanical response of a submarine concrete pipeline under wave action in shallow waters, taking into account factors such as the compressibility of pores and the permeability of the seabed. The control equation of the elliptical cosine wave theory is adopted to simulate the action of waves. In order to simulate the interaction between the solid skeleton and pore fluid, the concept of a "porous medium" is used to establish the transient seepage control equation. Utilizing the stress and displacement conditions at the interface of the ideal fluid media, porous media, and concrete pipeline, the numerical solutions for the internal force and pore pressure of the concrete pipeline buried in a semi-infinite thickness seabed were obtained; meanwhile, the effects of changes in the gas content in pore water and changes in the seabed permeability coefficient on a concrete pipeline were analyzed. The numerical calculation results show that, with the increase in the gas content in the pore water, the amplitude of the pore pressure on the pipeline surface decreases, and both the horizontal and vertical forces acting on the pipeline decrease; the amplitude of the pore pressure on the pipeline surface increases with the increase in seabed permeability and decreases with the enhancement of seabed permeability anisotropy; the improvement of the seabed permeability or enhancement of the permeability anisotropy can increase the horizontal force acting on the pipeline. This study provides a reference for the stability evaluation of submarine concrete pipelines under wave action in shallow water areas.