Buried pipeline protection for drag anchor interactions in a clay seabed — assessed through centrifuge modelling

Subsea pipelines are susceptible to drag anchor interactions, potentially compromising their structural integrity. A program of centrifuge tests was performed to investigate the effectiveness of different rock berm configurations in protecting a buried pipeline in a clay seabed against US Navy Stockless drag anchors of various sizes. The centrifuge experiments involved a series of anchor drags towards the buried pipeline, with measurements of the load developing in the anchor line and on the pipeline providing a measure of the effectiveness of the rock berm in deflecting the anchor drag trajectory from the pipeline location. These in-flight measurements were supplemented with drag trajectory and pipe deformation measurements made post-testing. Collectively the data were used to evaluate the performance of various berm geometries in providing protection against anchor dragging and reduced the level of uncertainty with several preferred berm geometries, allowing these to be adopted in the design of an offshore gas pipeline project.