A semi-analytical approach for simulating oblique kinematic distress of offshore pipelines due to submarine landslides

Abstract Deep water offshore pipelines are usually directly laid on the seabed, a fact that makes them vulnerable to geohazards, such as submarine landslides and debris flows. The intersection angle between the pipeline and the moving sediments can vary taking into account the pipeline route and the unstable nature of deep seabed. The aim of the current study is to examine the distress of a seabed-laid offshore natural gas pipeline subjected to combined lateral and axial kinematic distress due to an oblique submarine landslide or a debris flow. For this purpose, a new semi-analytical model is developed combining the finite-difference method and the elastic-beam theory. Firstly, the proposed model is compared with a finite-element model for various intersection angles, as well as with previous analytical models considering exclusively lateral loading. Subsequently, various combinations of soil resistance forces and loading conditions that affect the examined problem are investigated. Realistic input data were taken from the offshore section of the high-pressure natural gas pipeline TAP (Trans Adriatic Pipeline). Finally, useful conclusions are drawn regarding the applicability and efficiency of the proposed approach to accurately represent the pipeline response under these loading conditions.