Stability Analysis of Unburied Offshore Pipeline on Carobonate Soil Under Severe Storm Condition

The purpose of this paper is to investigate the stability of an unburied offshore pipeline resting on carbonate sand under severe storm condition. Pore pressure accumulation and pipeline movement during cyclic loading caused by waves and currents are numerically investigated. Both drag and lift forces are numerically obtained for 100 years return period storm condition using the Fourier decomposition method. Non-linear spring element is used to simulate a slip phenomenon between pipeline and seabed. The effects of both bi-linear and tri-linear spring element models on pipeline movement and pore pressure response are numerically investigated. Pipeline movement during cyclic loading greatly depends on the mechanical properties of non-linear spring element. In addition, pore water pressure response as well as shear strain are more sensitive to the initial unit tangential stiffness of spring element.