Rate effects during pipeline upheaval buckling in sand

Abstract

Knowledge of the uplift capacity of buried pipelines is critical in selecting appropriate burial depths to ensure their stability against upheaval buckling. Much work has focused on their capacity under either fully drained or fully undrained conditions. However, partial drainage conditions may be provoked for low-permeability silty sand seabeds, and this has not been studied in detail. This paper reports a series of physical model tests investigating the effects of pipeline displacement rate on both the uplift capacity of pipelines and the displacements required to mobilise peak load. It is shown that these drainage rate effects can be significant, and the drainage conditions will depend on the dimensionless velocity vD/cv, as suggested by previous researchers studying penetration and foundation problems. A change in normalised pipeline velocity will trigger different degrees of drainage and provoke different deformation mechanisms in the soil, and these will affect the load–displacement response of the pipelines. Designers should consider carefully how rate affects the upheaval buckling resistance of pipelines, especially in silty sands.