Development of V-H Yield Surface for Partially Embedded Offshore Pipelines Using Finite Element Analysis

Offshore pipelines undergo deformations when they are subjected to the hydrodynamic loads due to the combined action of waves and currents. The stability of these pipelines in terms of vertical as well as lateral direction is of important concern. Most of the studies in the literature focused on the pipeline laid on the clayey soil considering the pipe as a rigid material. This study presents the behaviour of the pipeline laid on the sandy soils considering the pipe as a rigid material. Finite element analysis using PLAXIS 3D has been carried when the pipe is subjected to vertical, horizontal, and combined vertical–horizontal loading. The length of the pipe is considered to be sufficiently long and taken to be 40 m. The seabed is modelled as a Mohr–Coulomb material with uniform strength throughout the depth. The V-H yield surfaces are presented for different pipe embedment and for different relative densities of the soil. The depth of embedment (w/D) considered is 0.5 and 1. The yield envelopes developed are useful in assessing the ultimate resistance of the pipelines.