Numerical Investigation on Uplift Behavior for Pipelines Shallowly Buried in Sloping Ground

Abstract

In practice, pipelines are inevitably buried in sloping ground, however, previous studies and guidelines of pipe-soil interaction mainly focus on level ground. In this study, the upward resistance-displacement curve for slopes with angles up to 20° was numerically investigated. To reflect the state-dependence, pre-peak hardening, and post-peak softening properties for dense sand, a modified Mohr-Coulomb model was implemented and validated by available physical tests. Numerical studies were carried out to explore the resistance-displacement curve, considering the coupling effects of slope angle, pipe-soil interface roughness, burial depth ratio. It is found that the pipeline in slopes is subjected to unbalanced lateral contact stress around its periphery. The pipeline and surrounding soil tend to move towards the slope toe during the uplift, especially for the perfectly smooth pipeline. As the slope angle increases, the peak resistance decreases for the perfectly smooth pipeline while increases for the perfectly rough one. Besides, the generally rough pipeline shows a quick post-peak reduction in the resistance. Possible mechanisms behind these phenomena were explored. Finally, considering the coupling effects of slope angle, interface roughness, burial depth ratio, a simplified method for the resistance-displacement curve based on the limit equilibrium method was proposed.