Responses of Submarine Pipelines to Impacts in Soft Clay

Subsea pipelines have been widely used to transfer oil from platforms to the mainland near harbor anchorage zone, and they become increasingly susceptible to risks stemming from dropped object impact damages. The impact from dropped objects may lead to local deformation and fracture in the pipeline and vast economic and environmental consequences. In this research, the responses of continuously supported offshore pipelines subjected to transverse impacts caused by dropped objects are studied. For this, the impact on an internally pressurized pipeline resting on a flexible bed has been numerically simulated. A relatively extensive parametric study has then been carried out to examine effects from variations in the cement coating thickness, internal pressure, indenter shape, impact velocity and subsoil mechanical properties on the pipeline response. It has been noticed that the presence of internal pressure results in substantial decrease in the impact dent depth, causing the deformation to become spatially more localized. It has also been shown that the flexibility of pipe bed plays an important role in the impact energy dissipation.