Numerical Simulation of Pipeline Undergoing Cyclic Lateral Motion in Clay

In a deepwater oil and gas development, a pipeline is often laid directly on the seabed rather than being buried in a trench. In addition to the cost benefit of not having to perform expensive underwater trenching, a pipeline laid in such a manner with planned geometric imperfection accommodate the axial elongation arising from thermal expansion and contraction cycles. Under such a scheme, the change in length of the pipeline during a thermal expansion and contraction cycle manifests itself as a lateral deflection of the pipeline on the seabed and the process relieves additional axial stress that would otherwise be induced. In order to employ this scheme successfully, comprehensive understanding of both the evolution of lateral soil resistance as well as the tendency of pipeline to self-embed into the seabed is required. As an alternative to experimental investigation, numerical analysis can be performed to simulate the response of the system under a cyclic lateral displacement of the pipe. In order to circumvent the deficiencies of a Lagrangian-based finite element approach in analyzing such problems, an Eulerian based finite element technique is employed in this study.