Numerical Modeling of the Pipeline Uplift Mechanism in Clay

Buried pipelines are a vital infrastructure and are mainly used to transport energy carriers and other essential products. The pipes are generally buried in the upper layer of soil deposits and, therefore, are highly affected by different geo-environmental conditions. The various pathological cases recorded in the world are caused by the degradation of structures in contact with swelling soils, the fact that necessitates a full understanding and investigation of such a phenomenon. This paper presents a method for the pipeline behavior modeling based on the finite element analysis by using PLAXIS 3D software, aimed at the determination of the pipe bending moment, displacement over its length, and the evaluation of vertical stresses in soil under the pipe. A parametric study has been carried out to investigate the effect of the pipe burial depth and the soil cohesion. The finite-element results have been compared with experimental data from the literature. It was found that, unlike laboratory models, the numerical analysis can account for the internal pressure in the pipe and the depth of the pipe burial. The finite-element analysis showed that the presence of fluid pressure inside the pipe results in a decrease in the maximum swelling of the soil by about 95%. The displacement of the pipe is considerably affected by the burial depth. The vertical stress at one end of the pipe can be greater than that at the other end in the case of a pipe under internal pressure, while in the case of an empty pipe, the values are very close at both ends. The numerical analysis shows that an increase in the pipe internal pressure leads to a decrease in its vertical displacement.