Soil pressure and structural response of large-diameter buried flexible pipes considering internal pressure effects

Buried flexible pipes are essential for infrastructure, yet current soil pressure models often overlook internal pressure. This study employs theoretical analysis and finite element methods to examine the soil pressure under internal pressure. An innovative soil pressure model is proposed, and the corresponding calculation formulas are derived. The results show that soil pressure generally exhibits a parabolic distribution under internal pressure, which is less affected by pipe diameter and diameter-to-thickness ratio but significantly influenced by burial depth. Moreover, the peak soil pressure is higher than that predicted by the prism or Marston models. A parabola model for soil pressure is proposed, characterizing the distribution in a parabolic form, with the peak pressure calculated as 1.2 times the prism load. For good accuracy and adaptability of large-diameter pipes, parabola and basin models are used together according to the relative size of pipe diameter and burial depth. Compared to uniform soil pressure, the parabola model reduces the deformation coefficient by approximately 26%, while the basin model reduces it by about 7%. Furthermore, a comprehensive comparison of pipe deformation from various methods shows that the proposed model aligns more closely with the finite element results in both trend and magnitude.