Coupled DEM-FEM analysis of submarine pipelines with rock armor berm under impact load

Submarine pipelines will possibly be damaged by dropped weights from ocean platforms or anchors from ships. The rock armor berm is the method commonly adopted to protect these pipelines by covering them with a layer of gravels, which can dissipate part of the energy of falling objects. In order to estimate the energy dissipating capacity of the rock armor berm, a coupled discrete element method (DEM) and finite element method (FEM) approach is proposed to analyze the dynamic response of pipelines under impact load. In this approach, DEM is used to model discrete gravels and FEM is used to model other continuous objects. The two kinds of elements interact on each other through the contact interface between them. The calculated results of energy absorptions by gravels coincide well with those recommended by the current code of DNV-RP-F107, and the calculated deformation rules of the pipeline are in good agreement with those given by model tests. These results prove the feasibility of using the proposed approach to evaluate the safety of submarine pipelines with rock armor berm.