Experimental Research on Flexible Pipelines in Soft Soil Foundations Under Uneven Settlement

Uneven settlement of soft soil foundations poses a potential threat to buried pipelines. Due to their low flexural stiffness， flexible pipelines are particularly prone to deformation and damage during such settlement. Through model tests of flexible pipelines in soft soil foundations under uneven settlement， this paper analyzed the variations in soil pressure and the mechanical characteristics of the pipelines. It further investigated the influence of pipe diameter and burial depth on the mechanical response of flexible pipelines. The results showed that after six cycles of uneven settlement， the soil pressure on the top of the pipeline increased significantly， with the soil pressure on the side of the pipeline reaching the largest. The soil pressure coefficient also increased with the number of settlement cycles. A nonlinear expression was established， relating the soil pressure coefficient to both the settlement depth and range， which can provide a theoretical basis for evaluating the mechanical response of flexible pipelines under uneven settlement. Both axial and circumferential stresses， as well as the displacements of the pipeline， increased with the expansion of the settlement range and the increase in the settlement magnitude. Increasing the pipe diameter or reducing the burial depth can effectively reduce pipeline stress and displacement. Therefore， in engineering design， the combined influence of both pipe diameter and burial depth should be comprehensively considered.