Expansion control design of large diameter pipelines

Pipelines exposed to high internal pressure and temperature have a large potential for axial expansion. Traditionally, an approach to this problem is normally based on extensive rock dumping or trenching, with the intention of freezing the as-laid pipeline configuration. For large diameter pipelines in severe seabed topography, traditional solutions may not be feasible, or they involve unacceptable costs and scheduled restraints. This paper deals with an alternative approach, which provides that axial compression forces are released through lateral snaking. Due to soft soil conditions and large seabed imperfections, the development of a snaked pipeline configuration is normally initiated in the vertical direction, and followed by lateral deflection modes. Local bending moments resulting from the snaking behavior are associated with large pipeline strains. Intervention measures are normally required in order to limit the expansion into snaking sections. This paper focuses on design aspects and acceptance criteria to be considered for an expansion control design of large diameter pipelines in cohesive soils.